Surgery of the Bovine Digestive Tract
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Surgery of the Bovine Small Intestine
Donald F. Smith, DVM*
The prevalence of surgical conditions affecting the small intestine in cattle is proportionately much less than that of those affecting the stomach compartments or the large intestine. Nevertheless, obstructive conditions of the small intestine requiring surgical intervention do occur sporadically, and their successful treatment can be very rewarding both to the veterinarian and to the owner. The standard surgical approach to the intestinal tract is through a vertical incision in the right paralumbar fossa. 22 This approach maximizes exposure of the small intestine and allows relatively easy access to the large intestine and the remainder of the abdominal organs. A clear knowledge of visceral and intestinal anatomy as exposed through the right paralumbar fossa incision is a critical factor in determining the degree of success to be achieved in the surgical repair of intestinal lesions. However, despite the availability of accurate and complete textbook descriptions of bovine intestinal anatomy, many veterinarians remain uncomfortable exploring the abdominal viscera from the right side. Surgical manipulation of the small intestine may be difficult because of the abundant mesenteric and omental fat and the difficulty in exteriorizing segments of intestine with short mesentery.
RELEVANT SURGICAL ANATOMys,U,!l The small intestine is located between the pylorus and the cecum and consists of the duodenum, jejunum, and ileum. Because the jejunum and ileum are confluent and there is no clear demarcation between the two segments, they are sometimes referred to as jejunoileum. 21 Compared with the jejunoileum, the duodenum is relatively *Diplomate, American College of Veterinary Surgeons; Associate Dean for Veterinary Education, Professor of Surgery, and Chairman, Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca, New York Veterinary Clinics of North America: Food Animal Practice-Vol. 6, No.2, July 1990
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immobile, thick-walled, and short, although it is capable of expansion to a large diameter when obstructed. It has three parts. The cranial part of the duodenum (cranial duodenum) extends dorsally or slightly dorsocranially from the pylorus. The initial 10 cm is mobile and, with the pyloric part of the abomasum, can be readily exteriorized through the right paralumbar fossa. 22 As the cranial duodenum extends dorsally it is more tightly adherent to the visceral surface of the liver and cannot be readily exteriorized through the right paralumbar fossa. At the liver, the cranial duodenum forms an "S" -shaped curve (sigmoid) near the openings of the common bile duct and the accessory pancreatic duct. The descending part of the duodenum (descending duodenum) extends caudally from the liver along the right side of the abdomen. This portion of bowel is probably the most easily recognized segment of intestine in the cow, as it is generally the first structure encountered upon opening the abdomen through a right paralumbar fossa incision. Although diagrams of the descending duodenum often depict its orientation in a cranial to caudal direction across the dorsal aspect of the abdomen, the central portion of this segment may, in reality, be located far ventrally within the abdomen. This gives the descending duodenum a curved rather than straight appearance. The descending duodenum is suspended dorsally by the mesoduodenum. Its ventral surface serves as the attachment for the superficial and deep sheets of the greater omentum. At the level of the transverse plane of the fifth and sixth lumbar vertebrae, the duodenum crosses to the left side of the root of the mesentery and proceeds cranially as the ascending part of the duodenum (ascending duodenum). The caudal flexure of the duodenum is attached to the descending colon by the prominent duodenocolic ligament. The ascending duodenum is obscured from view from the right side by the combined mesenteries and by portions of the proximal and distal loops of the ascending colon. It is generally thought to be inaccessible to surgical manipulation. However, careful dissection through the mesentery allows relatively direct access to the majority of this segment of intestine. The duodenum is continuous with the jejunum at the level of the cranial mesenteric artery. The jejunoileum is very long relative to other segments of the bovine intestinal tract and relative to the comparable length of the jejunoileum in nonruminant species. In the adult cow, its length is 35 to 55 m. It is arranged in tight coils at the edge of the mesentery. These coils are more tightly compressed in the proximal portions of the jejunoileum, where the mesentery is short. These factors, combined with its cranial positioning within the abdominal cavity, make exposure of this portion of intestine through a paralumbar fossa incision difficult. The jejunum has been arbitrarily divided into three segments: proximal, middle, and distal; and the ileum into two segments: proximal and distal. 12 The proximal jejunum extends from the cranial border of the duodenocolic ligament for a distance of approximately 5 to 7 m to the level of the division of the cranial mesenteric artery into the collateral branch and the continuation of the parent artery. The long middle part
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of the jejunum extends 20 to 30 m to the level of the reunion of the collateral branch with the cranial mesenteric artery. The distal jejunum extends caudally to the point where the mesentery is the longest and the small intestine angles craniodorsally as the ileum. The jejunoileal junction is also adjacent to the termination of the cranial mesenteric artery. The proximal ileum is convoluted and extends to the level of the apex of the cecum, where it is continuous with the shorter and much less convoluted distal ileum. The ileum enters the cecocolic junction at its ventromedial surface. The arterial and venous supply to the jejunoileum is largely obscured from view by the fat-filled mesentery and is intimately associated with the lymph nodes draining the jejunoileum. 12
RESTRAINT FOR SURGICAL EXPLORATION A right paralumbar fossa celiotomy with the cow restrained in a standing position is recommended for the majority of surgical procedures involving the small intestine of the adult cow. 22 With the cow standing, the viscera can generally be most easily palpated, exteriorized, and repositioned. Light tranquilization for a nervous or painful cow is often helpful to minimize movement during the procedure. If the cow is extremely painful or depressed, or if the presurgical diagnosis indicates the need for intestinal resection, it may be wise to perform the procedure with the cow positioned in left lateral recumbency. General anesthesia may be helpful if available. A cow positioned in lateral recumbency is at substantial risk of regurgitation of large quantities of rumen contents. It should be positioned with the head tilted downward, and a cuffed endotracheal tube should be securely in place throughout the procedure. 22 Placement of thick pads beneath the shoulder and the hip area provides a recess to accommodate the distended abdomen of a cow with fluid and gas accumulations in the stomach compartments. 22
INTUSSUSCEPTION Intussusception is the invagination of one segment of bowel into the lumen of the adjacent segment. The apex of the inner segment (intussusceptum) advances into the adjacent bowel, which becomes the outer ensheathing layer (intussuscipiens). Intestinal obstruction results because of the occlusion of the bowel lumen by the swollen and edematous intussusceptum. As the mesentery supporting the intussusceptum is dragged into the ensheathing layer, the vascular supply to the bowel is occluded, resulting in abdominal pain, bowel ischemia, and subsequently peritonitis. 2o Intussusception is considered to be the most common cause of complete obstruction of the jejunoileum in adult cattle. 14 - 16 Neverthe-
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less, there may be a tendency to overdiagnose the condition whenever one encounters a cow with signs of colic and evidence of small intestinal distention. In most species, intussusception is primarily a disease of the young. This is also likely to be true in cattle,24 although most case summaries describe its occurrence in adult cattle. The enteric form of intussusception, in which one segment of jejunoileum becomes invaginated into an adjacent segment of similar bowel, is most common in mature cattle. 24 Most of these occur in the distal jejunum and the proximal ileum. This is the portion of bowel suspended by the mesenteric "flange," where the mesentery is longest and most mobile. Although common in other species, ileocecal or ileocolic intussusceptions are not observed in adult cattle because of the stability afforded by the ileocecal ligament. However, these forms of intussusception do occur in young calves, as the mesentery is very thin and does not provide the same degree of support as in older animals. In the adult form of the condition, a mass or tumor is often found at the leading edge of the intussusception. These lesions may be intraluminal or intramural and may include parasitic nodules, caseocalcareous abscesses, and neoplasms. 1,4,14,20 The mass acts as an intestinal foreign body bulging into the lumen and predisposes to asynchronous peristalsis that forces one segment of bowel into its adjacent portion. In calves, postulated causative factors include dietary changes and viral and bacterial enteritis. These conditions may cause asynchronous peristalsis or hypermotility and predispose to intussusception. 24 Diagnosis The onset of clinical signs following intussusception is acute and is characterized by an abrupt change in attitude, anorexia, colic, and rapid decrease in milk production. The initial phase of severe abdominal pain is caused primarily by the tension on the mesentery as it is drawn into the intussuscipiens, and it persists for 6 to 12 hours. After the involved segment of intestine and its associated mesentery have become necrotic, signs of discomfort are less intense. The cow becomes progressively depressed as localized, and in late stages more generalized, peritonitis develops. Untreated cows often survive 5 to 10 days if the lesion is in the distal part of the small intestine, and they can be successfully operated upon several days after onset of clinical signs. 24 Abdominal distention becomes apparent within hours of the onset of colic. The abdomen first becomes pear-shaped when viewed from behind the cow. This results from the accumulation of fluid and gas in the small intestine proximal to the obstruction. Similarly, the ventral sac of the rumen starts to enlarge as the movement of digesta from the rumenoreticulum into the omasum and abomasum slows. In later stages of the condition, the abdomen appears round (apple-shaped) because of massive distention in the stomach compartments and in the proximal jejunoileum. 23 Feces often continue to be passed during the first few hours after intussusception as the distal part of the intestinal tract empties. There-
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after, the cow passes small amounts of sticky, dark red feces that consist of blood from the mucosal surface of the intussusceptum mixed with mucus from the distal portions of the intestinal tract. These feces are sometimes described as having a Hraspberry jam" appearance. 20 Simultaneous auscultation and percussion of the right surface of the abdomen may yield several small areas of tympanitic resonance, representing gas accumulation within segments of small intestine proximal to the intussusception. 19,24 Splashing sounds can be heard during succussion of the lower right flank with simultaneous auscultation in the paralumbar fossa. Examination of the abdominal cavity per rectum is often the single most helpful test in establishing the diagnosis of intussusception.24 Multiple loops of tightly distended small intestine can be felt throughout the right side of the abdominal cavity, filling the pelvic cavity, and often extending into the left side of the abdomen caudal to the rumen. The actual intussusception can often be felt as a firm or spongy coiled mass in the upper right portion of the abdomen. Fibrinous adhesions can be felt in the area, and the cow may exhibit a painful response to manipulation of the lesion. If the intussusception is located in the proximal jejunum, neither distended small intestine nor the lesion itself will be palpable, and one may seriously doubt the diagnosis even if all other parameters indicate the presence of intussusception. Similarly, distended bowel may not be felt in cows that are in mid to late gestation because the uterus is pushed caudally and dorsally into the pelvic inlet. Clinicopathologic parameters are seldom useful in establishing the diagnosis. They are more helpful in determining the severity of the disease process and in establishing the prognosis. As the cow's condition deteriorates, hemoconcentration and leukocytosis with left shift become evident. 25 Hypochloremic metabolic alkalosis with hypokalemia typically develops within 48 to 72 hours after distal small intestinal intussusception and much more rapidly following proximal obstruction. 25 Peritoneal fluid is voluminous and contains high concentrations of protein. The nucleated cell count may be normal or high, depending on the severity of peritonitis. Treatmenti5 Surgical correction should not be unnecessarily delayed, although it is important to adequately stabilize the cow before surgery. Intravenous fluid therapy to treat metabolic alkalosis is indicated if dehydration is present. This can be accomplished by the use of isotonic NaCI with the addition of 20 to 30 mEqJL of KCI. Some prefer to add small amounts of glucose to enhance intracellular movement of potassium. Parenteral antibiotic therapy should be initiated before surgery to ensure optimal tissue levels at the time of resection and anastomosis. Surgery is performed through the right paralumbar fossa. Although adequate exposure can usually be achieved with the cow standing, manipulation and tension on the mesentery may cause enough pain to make the cow attempt to lie down during the surgical procedure. If this becomes a problem, it may be advisable to close the abdomen
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temporarily, cast the cow, and proceed with the cow restrained in a recumbent position. 22 Locating the intussusception during surgical exploration is not difficult. Sweeping of the hand through the distended intestine generally will locate the lesion, either within or outside of the supraomental recess. With gentle traction, the intussusception can be exteriorized from the incision and packed off from the adjacent bowel. Attempting to manually reduce the intussusception is contraindicated because the bowel and associated mesentery are fragile and prone to tearing. Furthermore, because of the likelihood that the intussusception was caused by an intestinal mass, it is only logical to remove the offending bowel and thus to minimize the chance for recurrence. Wide resection of the bowel on each side of the intussusception is recommended, especially proximally, where the distention of the proximal bowel may have compromised the integrity of the vascular supply. Mesenteric vessels are ligated close to the bowel to avoid inadvertently cutting the continuation of the cranial mesenteric vessels, which traverse relatively close to the intestine. An end-to-end anastomosis using either an apposing or inverting technique provides accurate realignment of the intestinal lumen. Because the adult bovine mesentery contains large amounts of fat, the mesenteric border or CCangle" is wider than in many other species. 13 This has the potential of weakening the most compromised area of closure, that is, the mesenteric angle, where there is no serosal covering. Levine recently reported that the bursting wall tension of mesenteric border incisions was lower than that of antimesenteric incisions. 13 An end-to-end anastomosis in which one end is rotated approximately 30 relative to the other end (such as has been reported in human beingsll) may be useful in minimizing the likelihood of leakage of intestinal contents from the mesenteric angle. Following completion of the anastomosis, the mesenteric defect must be carefully closed. The intestine is rinsed and replaced within the supraomental recess, and the abdomen is closed. Postoperative care is routine and should include fluid and antibiotic therapy as indicated. Feces usually are passed within hours of the completion of surgery. Initially, these are copious and watery, but the feces soon become more formed and return to normal within days of surgery. Rapid and complete recovery should be expected in uncomplicated cases. 0
INTESTINAL VOLVULUS Volvulus results from twisting of a segment of intestine upon itself, thereby creating a closed loop obstruction. In addition to rapid distention of the portion of the bowel enclosed within the volvulus, the intestine proximal to the lesion becomes distended because of accumulation of intestinal contents. There are two relatively easily distinguishable forms of intestinal volvulus in cattle: segmental volvulus of the jejunoileum, and volvulus of the small (and large) intestine about the mesenteric root.
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SEGMENTAL VOLVULUS OF THE JEJUNOILEUM6,26
This type of volvulus usually affects the segment of jejunoileum suspended by the distal-most aspect of the mesenteric flange. Twisting of 180 to 360 is common, with the affected bowel often ending up snugly compacted within the caudal part of the abdomen and the pelvic inlet. Unlike horses and other species, cattle are not as likely to develop intestinal ischemia because the thick layer of mesenteric fat acts as a cushion and spares the major arteries from occlusion in early stages of the volvulus. In addition, the fat may actually prevent severe twisting of the intestine. Consequently, affected cattle do not deteriorate as rapidly as might otherwise be expected. 0
Diagnosis This condition occurs sporadically in cattle of all ages. Its cause is obscure, although ileus has been reported to be an inciting cause. I6 Onset of clinical signs is sudden and dramatic. Affected cows show signs of severe colic, more severe than that observed with intussusception or incarceration of similar segments of intestine. Signs of colic usually persist until the lesion is corrected, although the pain becomes less severe if ischemic necrosis of the affected bowel develops. As in cows with intussusception, the abdomen first appears pearshaped, then round and full when viewed from behind. 23 Feces may continue to be passed for several hours. However, after the colon becomes empty, there is complete cessation of fecal passage. Thick, tenacious mucus may be present within the rectum. Rectal examination reveals the presence of multiple tightly distended loops of small intestine, usually within the pelvic inlet and extending cranially as far as can be reached. The cow may exhibit pain when these loops are palpated. Tachycardia and hemoconcentration are present, the severity of which is determined by the duration of the illness and the amount of intestine involved in the twist. Some cows demonstrate a mild metabolic alkalosis with hypochloremia, although development of superimposed metabolic acidosis is to be anticipated as the condition progresses. Treatment Once the provisional diagnosis has been made, surgical repair should not be delayed, as affected cows generally deteriorate much more rapidly than cows with intussusception or incarceration. A right paralumbar fossa approach with the cow in a standing position is usually recommended as it facilitates manipulation, untwisting, and repositioning of the involved intestine within the distended abdominal cavity. This decision is generally made with the realization that ischemia, to the degree that resection of the involved bowel would become necessary, is seldom encountered. However, the decision to perform surgery with the cow standing or recumbent is usually dictated by the facilities at hand and the confidence one has in the accuracy of the provisional diagnosis.
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Exploration of the abdominal cavity reveals distention of the majority of the small intestine (proximal to the volvulus). The involved bowel is turgid and is usually located within the caudodorsal part of the peritoneal cavity at the pelvic inlet. Although difficult, exteriorization is usually necessary to permit untwisting of the bowel. A clear depressed and blanched line of demarcation across the mesentery confirms the diagnosis. Regardless of the need for resection, the use of antiprostaglandins before and during the surgical procedure is recommended to minimize the effects of toxin release after untwisting. Following reduction, the intestine is carefully returned to the supraomental recess, although the massive distention of all of the small intestine may make repositioning difficult. The prognosis is good and most cows recover rapidly and completely. Recurrence of the volvulus or development of clinically significant adhesions is rare. VOLVULUS
OF THE INTESTINE ABOUT THE MESENTERIC ROOT 18,!6,!9
Torsion of the mesenteric root results in volvulus of the jejunum, ileum, cecum, and the majority of the ascending colon. Only the duodenum and the parts of the colon located within the dorsal parts of the mesentery are spared. This is a most dramatic and rapidly fatal condition because of the large amount of intestine that undergoes acute vascular compromise. Diagnosis The predominant clinical sign is the peracute onset of severe unrelenting pain. A typically affected cow may first kick at her abdomen, then throw herself to the ground, roll onto her side, then jump to her feet and repeat the process. The heart rate is very high, and affected cows rapidly develop bilateral abdominal distention, giving them a round appearance when viewed from behind. Multiple areas of tympanitic resonance can be elicited over wide areas of the right side of the abdomen, usually centered in the paralumbar fossa, but extending cranially over the rib area. The prominent outline of tightly distended viscera may be seen though the right paralumbar fossa. On rectal examination, multiple loops of tightly distended small intestine, cecum, and colon can be felt throughout the entire caudal aspect of the abdomen. Tight bands of mesentery may be identified. Treatment This condition represents an acute medical and surgical emergency. Because of the need for rapid decompression and untwisting of the bowel, there is seldom time for transport of the cow to a referral surgical facility. A liberal right paralumbar fossa celiotomy is performed with the cow standing, if possible. As the peritoneal cavity is opened, distended intestine is readily apparent throughout the abdominal cavity. By carefully following the mesentery to its root, the site and
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direction of the twist can usually be identified. The volvulus can more easily be reduced after removal of gas from the larger segments of colon and cecum. Aggressive medical therapy is necessary during the preoperative and intraoperative periods. Prognosis for survival, even through the surgical period, is poor. Some cows succumb shortly after the bowel is untwisted, presumably as a result of release of toxins sequestered in the occluded vessels.
INCARCERATION, ENTRAPMENT, OR EXTRALUMINAL COMPRESSION During the past few years, there have been several reported cases of incarceration or entrapment of the small intestine in cattle. The distal flange of the jejunoileum is typically the primary site of such lesions, although they may occur throughout the jejunum or ileum. Reported causes of this form of obstruction include persistent vitelloumbilical band,IO persistent round ligament of the liver, 5 parovarianomental bands,17 persistent urachal remnant, 2 and remnant of the ductas deferens in steers. 30 Remnants of embryonal structures often persist as thin, tough ligamentous bands fixed at both ends. One end is usually attached to the body wall (often the umbilicus), and the other end is attached to a viscus, such as the liver (round ligament), ileum (vitelloumbilical band), or bladder (urachal remnant). Obstruction results when a segment of intestine wraps around, or becomes entrapped within, a loop formed by the band. The vascular supply to the segment of bowel is compromised and passage of digesta through the intestine ceases. This represents a true incarceration. Affected cows develop acute anorexia and visceral abdominal pain. They typically appear similar to cattle with intussusception. The offending band may occasionally be identified on examination per rectum. Surgical correction is achieved through a right paralumbar fossa celiotomy. The involved intestine is readily recognized and exteriorized if possible. The affected bowel should be handled carefully to minimize the risk of rupture. Sharp transection of the offending band results in immediate release of the incarceration. The bowel should then be carefully examined to determine whether resection is necessary. Unlike cows with intussusception, in which resection and anastomosis is almost always indicated, incarcerated bowel from the described causes often remains viable, and the cow makes a rapid and full recovery. Segments of the small intestine may also become incarcerated through a rent in the mesentery, either spontaneously or after intestinal resection in which the mesentery has not been adequately closed. 18,27 Clinical signs and surgical approach are similar to those described earlier. After identification of the involved segment of intestine, the herniated bowel is reduced by gentle traction, perhaps after enlarging the hole through which the bowel has become entrapped. Although rare, portions of the intestine may become compressed from the exterior by lipomatosis or fat necrosis. 3 Onset of signs is
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gradual; affected cows slowly become progressively hypophagic and pass smaller and smaller amounts of loose feces. Multiple loops of distended small intestine can be palpated on rectal examination, and the offending mass(es) of fat can sometimes be felt as hard structures embedded among the distended intestine. Effective surgical repair is seldom possible.
SCROTAL AND INGUINAL HERNIAS
External hernias resulting in incarceration or strangulation are unusual. I8 Umbilical or ventral abdominal hernias typically involve the abomasum or associated omentum. Scrotal or inguinal hernias involving the jejunoileum are seen predominantly in beef bulls. 18 Most hernias occur during the breeding season and involve the left side. Incarceration and strangulation seldom occur. The scrotum is enlarged unilaterally, either just at the neck region (inguinal hernia) or along the whole length of the scrotum (scrotal hernia).9 Careful palpation reveals the presence of gas and fluid-filled loops of small intestine. Definitive diagnosis can be made by rectal examination, in which the small intestine can be felt entering the inguinal canal. Surgical Repair Scrotal and inguinal hernias may be repaired through a left paralumbar fossa incision in a standing or recumbent bull, or through an incision over the inguinal canal with the bull positioned in lateral recumbency. Use of the paralumbar fossa technique assumes reducibility and viability of the herniated intestine. The incision is made in the ventral part of the paralumbar fossa approximately 12 cm dorsal to the fold of the flank. 9 The internal inguinal ring is located intra-abdominally, and the herniated segment of intestine is reduced. One or two large mattress sutures of nonabsorbable material are blindly placed through the margins of the internal inguinal ring. The ring must be closed sufficiently to avoid reherniation, although not so tightly as to cause compression of the spermatic cord. The abdominal cavity is closed in a routine manner. The inguinal or scrotal approach allows more direct access to the hernia. An incision is made over the external inguinal ring extending onto the neck of the scrotum. 18 The intestines should be reduced without incising the parietal tunic unless adhesions are present or compromised intestine is anticipated. The parietal tunic is reduced in size by placing sutures through its redundant portion. Part of the external inguinal ring is then sutured, being careful to leave sufficient space for the spermatic cord. Skin closure is routine. The testicle is retained in both of the described methods for surgical repair, although if necessary it can be removed readily by means of the inguinal approach.
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FUNCTIONAL OBSTRUCTION OF THE DUODENUM Functional obstruction of the sigmoid curve of the duodenum may be easily confused with right-sided abomasal displacement or volvulus. 28 Affected cows develop signs consistent with abomasal outflow failure, that is, anorexia, decreased milk production, progressive bilateral abdominal distention, and the presence of succussible fluid in the right cranial portion of the abdominal cavity. Some cows have easily recognizable gaseous abomasal tympany that can be detected over the last few ribs on the right side. Occasionally, the fluid-distended abomasum may be palpated on rectal examination, just caudal to the right costal arch. Affected cows are dehydrated and have tachycardia with severe hypochloremic metabolic alkalosis, hyponatremia, and hypokalemia. In a recent study of cows with obstruction of the proximal part of the duodenum, Garry also reported the presence of hyperglycemia and increased anion gap in affected cows, the latter thought to be due in part to prerenal azotemia and associated hyperphosphatemia and hyperproteinemia. 7 Surgical correction is by right paralumbar fossa celiotomy with the cow restrained in a standing position. The abomasum is decompressed, and a side-to-side anastomosis is performed between the cranial and descending parts of the duodenum. 28 This serves to bypass the sigmoid area of the duodenum, where the functional obstruction is thought to be present. Prognosis for full recovery is good.
REFERENCES 1. Archer RM, Cooley AJ, Hinchcliff KW, et al: Jejunojejunal intussusception associated with a transmural adenocarcinoma in an aged cow. J Am Vet Med Assoc 192:209-211, 1988 2. Baxter GM, Darien BJ, Wallace CE: Persistent urachal remnant causing intestinal strangulation in a cow. J Am Vet Med Assoc 191:555-558, 1987 3. Bridge PS, Spratling FR: Bovine lipomatosis. Vet Rec 74:1357-1362,1962 4. Bossard JK: Telescoped intestines in cattle. Cornell Vet 20:55-58, 1930 5. Ducharme NG, Smith DF, Koch DB: Small intestinal obstruction caused by a persistent round ligament of the liver in a cow. J Am Vet Med Assoc 180:1234-1236, 1982 6. Fubini SL, Smith DF, Tithof PK, et al: Volvulus of the distal part of the jejunoileum in four cows. Vet Surg 15:150-152, 1986 7. Garry F, Hull BL, Rings DM, et al: Comparison of naturally occurring proximal duodenal obstruction and abomasal volvulus in dairy cattle. Vet Surg 17:226-233, 1988 8. Habel RE: Ruminant digestive system. In Getty R (ed): Sisson and Grossman's Anatomy of the Domestic Animals, ed 5. Philadelphia, WB Saunders, 1975, pp 903-908 9. Hofmeyr CFB: Ruminant Urogenital Surgery. Ames, Iowa State University, 1987, pp 32-34 10. Koch DB, Robertson IT, Donawick WJ: Small intestinal obstruction due to persistent vitello umbilical band in a cow. J Am Vet Med Assoc 173:197 -200, 1978 11. LaCalle JP, Sole JMG, Pey CG, et al: Rotated intestinal anastomoses. Surg Gynecol Obstet 154:662-666, 1982
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12. Levine SA, Smith DF, Wilsman NJ, et al: Arterial and venous supply to the bovine jejunum and proximal part of the ileum. Am J Vet Res 48:1295-1299, 1987 13. Levine SA, Smith DF, Wilson JW, et al: Comparative healing of mesenteric and antimesenteric incisions in the bovine jejunum. Am J Vet Res 49:1339-1343, 1988 14. Pearson H: Intussusception in cattle. Vet Rec 89:426-437, 1971 15. Pearson H: The treatment of surgical disorders of the bovine abdomen. Vet Rec 92:245-254, 1973 16. Pearson H, Pincent PJN: Intestinal obstruction in cattle. Vet Rec 101:162-166, 1977 17. Richardson DW: Paraovarian-omental bands as a cause of small intestinal obstruction in cows. J Am Vet Med Assoc 185:517 -519, 1984 18. Robertson JT: Differential diagnosis and surgical management of intestinal obstruction in cattle. Vet Clin North Am [Large Anim Pract] 1:377 -394, 1979 19. Smith DF, Erb HN, Kallaher KM, et al: The identification of structures and conditions responsible for right side tympanitic resonance (ping) in adult cattle. Cornell Vet 72:180-199, 1982 20. Smith DF: Intussusception in adult cattle. Comp Cont Ed Pract Vet II:S49-S53, 1980 21. Smith DF: Bovine intestinal surgery. Part 1: Surgical anatomy. Mod Vet Pract 65:705-710, 1984 22. Smith DF: Bovine intestinal surgery. Part 2: Surgical exploration. Mod Vet Pract 65:853-857, 1984 23. Smith DF: Bovine intestinal surgery. Part 3: Clinical examination. Mod Vet Pract 65:909-914, 1984 24. Smith DF: Bovine intestinal surgery. Part 5: Intussusception. Mod Vet Pract 66:405-409, 1985 25. Smith DF: Bovine intestinal surgery. Part 6: Intussusception (continued). Mod Vet Pract 66:443 - 446, 1985 26. Smith DF: Bovine intestinal surgery. Part 7: Intestinal volvulus. Mod Vet Pract 66:995-999, 1985 27. Trent AM, Bailey JV: Herniation of the small intestine through the right lateral ligament of the bladder in a bull. Can Vet J 26:16-19, 1985 28. Velden MA Van der: Functional stenosis of the sigmoid curve of the duodenum in cattle. Vet Rec 112:452-453, 1983 29. Willet MDJ: Intestinal torsion in cattle. NZ Vet J 18:42-43, 1970 30. Wolfe DW, Mysinger PW, Carson RL, et al: Incarceration of a section of small intestine by remnants of the ductus deferens in steers. J Am Vet Med Assoc 191:1597 -1598, 1987
Address reprint requests to Donald F. Smith, DVM Department of Clinical Sciences New York State College of Veterinary Medicine Cornell University Ithaca, NY 14853
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Surgery of the Bovine Small Intestine
Donald F. Smith, DVM*
The prevalence of surgical conditions affecting the small intestine in cattle is proportionately much less than that of those affecting the stomach compartments or the large intestine. Nevertheless, obstructive conditions of the small intestine requiring surgical intervention do occur sporadically, and their successful treatment can be very rewarding both to the veterinarian and to the owner. The standard surgical approach to the intestinal tract is through a vertical incision in the right paralumbar fossa. 22 This approach maximizes exposure of the small intestine and allows relatively easy access to the large intestine and the remainder of the abdominal organs. A clear knowledge of visceral and intestinal anatomy as exposed through the right paralumbar fossa incision is a critical factor in determining the degree of success to be achieved in the surgical repair of intestinal lesions. However, despite the availability of accurate and complete textbook descriptions of bovine intestinal anatomy, many veterinarians remain uncomfortable exploring the abdominal viscera from the right side. Surgical manipulation of the small intestine may be difficult because of the abundant mesenteric and omental fat and the difficulty in exteriorizing segments of intestine with short mesentery.
RELEVANT SURGICAL ANATOMys,U,!l The small intestine is located between the pylorus and the cecum and consists of the duodenum, jejunum, and ileum. Because the jejunum and ileum are confluent and there is no clear demarcation between the two segments, they are sometimes referred to as jejunoileum. 21 Compared with the jejunoileum, the duodenum is relatively *Diplomate, American College of Veterinary Surgeons; Associate Dean for Veterinary Education, Professor of Surgery, and Chairman, Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca, New York Veterinary Clinics of North America: Food Animal Practice-Vol. 6, No.2, July 1990
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immobile, thick-walled, and short, although it is capable of expansion to a large diameter when obstructed. It has three parts. The cranial part of the duodenum (cranial duodenum) extends dorsally or slightly dorsocranially from the pylorus. The initial 10 cm is mobile and, with the pyloric part of the abomasum, can be readily exteriorized through the right paralumbar fossa. 22 As the cranial duodenum extends dorsally it is more tightly adherent to the visceral surface of the liver and cannot be readily exteriorized through the right paralumbar fossa. At the liver, the cranial duodenum forms an "S" -shaped curve (sigmoid) near the openings of the common bile duct and the accessory pancreatic duct. The descending part of the duodenum (descending duodenum) extends caudally from the liver along the right side of the abdomen. This portion of bowel is probably the most easily recognized segment of intestine in the cow, as it is generally the first structure encountered upon opening the abdomen through a right paralumbar fossa incision. Although diagrams of the descending duodenum often depict its orientation in a cranial to caudal direction across the dorsal aspect of the abdomen, the central portion of this segment may, in reality, be located far ventrally within the abdomen. This gives the descending duodenum a curved rather than straight appearance. The descending duodenum is suspended dorsally by the mesoduodenum. Its ventral surface serves as the attachment for the superficial and deep sheets of the greater omentum. At the level of the transverse plane of the fifth and sixth lumbar vertebrae, the duodenum crosses to the left side of the root of the mesentery and proceeds cranially as the ascending part of the duodenum (ascending duodenum). The caudal flexure of the duodenum is attached to the descending colon by the prominent duodenocolic ligament. The ascending duodenum is obscured from view from the right side by the combined mesenteries and by portions of the proximal and distal loops of the ascending colon. It is generally thought to be inaccessible to surgical manipulation. However, careful dissection through the mesentery allows relatively direct access to the majority of this segment of intestine. The duodenum is continuous with the jejunum at the level of the cranial mesenteric artery. The jejunoileum is very long relative to other segments of the bovine intestinal tract and relative to the comparable length of the jejunoileum in nonruminant species. In the adult cow, its length is 35 to 55 m. It is arranged in tight coils at the edge of the mesentery. These coils are more tightly compressed in the proximal portions of the jejunoileum, where the mesentery is short. These factors, combined with its cranial positioning within the abdominal cavity, make exposure of this portion of intestine through a paralumbar fossa incision difficult. The jejunum has been arbitrarily divided into three segments: proximal, middle, and distal; and the ileum into two segments: proximal and distal. 12 The proximal jejunum extends from the cranial border of the duodenocolic ligament for a distance of approximately 5 to 7 m to the level of the division of the cranial mesenteric artery into the collateral branch and the continuation of the parent artery. The long middle part
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of the jejunum extends 20 to 30 m to the level of the reunion of the collateral branch with the cranial mesenteric artery. The distal jejunum extends caudally to the point where the mesentery is the longest and the small intestine angles craniodorsally as the ileum. The jejunoileal junction is also adjacent to the termination of the cranial mesenteric artery. The proximal ileum is convoluted and extends to the level of the apex of the cecum, where it is continuous with the shorter and much less convoluted distal ileum. The ileum enters the cecocolic junction at its ventromedial surface. The arterial and venous supply to the jejunoileum is largely obscured from view by the fat-filled mesentery and is intimately associated with the lymph nodes draining the jejunoileum. 12
RESTRAINT FOR SURGICAL EXPLORATION A right paralumbar fossa celiotomy with the cow restrained in a standing position is recommended for the majority of surgical procedures involving the small intestine of the adult cow. 22 With the cow standing, the viscera can generally be most easily palpated, exteriorized, and repositioned. Light tranquilization for a nervous or painful cow is often helpful to minimize movement during the procedure. If the cow is extremely painful or depressed, or if the presurgical diagnosis indicates the need for intestinal resection, it may be wise to perform the procedure with the cow positioned in left lateral recumbency. General anesthesia may be helpful if available. A cow positioned in lateral recumbency is at substantial risk of regurgitation of large quantities of rumen contents. It should be positioned with the head tilted downward, and a cuffed endotracheal tube should be securely in place throughout the procedure. 22 Placement of thick pads beneath the shoulder and the hip area provides a recess to accommodate the distended abdomen of a cow with fluid and gas accumulations in the stomach compartments. 22
INTUSSUSCEPTION Intussusception is the invagination of one segment of bowel into the lumen of the adjacent segment. The apex of the inner segment (intussusceptum) advances into the adjacent bowel, which becomes the outer ensheathing layer (intussuscipiens). Intestinal obstruction results because of the occlusion of the bowel lumen by the swollen and edematous intussusceptum. As the mesentery supporting the intussusceptum is dragged into the ensheathing layer, the vascular supply to the bowel is occluded, resulting in abdominal pain, bowel ischemia, and subsequently peritonitis. 2o Intussusception is considered to be the most common cause of complete obstruction of the jejunoileum in adult cattle. 14 - 16 Neverthe-
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less, there may be a tendency to overdiagnose the condition whenever one encounters a cow with signs of colic and evidence of small intestinal distention. In most species, intussusception is primarily a disease of the young. This is also likely to be true in cattle,24 although most case summaries describe its occurrence in adult cattle. The enteric form of intussusception, in which one segment of jejunoileum becomes invaginated into an adjacent segment of similar bowel, is most common in mature cattle. 24 Most of these occur in the distal jejunum and the proximal ileum. This is the portion of bowel suspended by the mesenteric "flange," where the mesentery is longest and most mobile. Although common in other species, ileocecal or ileocolic intussusceptions are not observed in adult cattle because of the stability afforded by the ileocecal ligament. However, these forms of intussusception do occur in young calves, as the mesentery is very thin and does not provide the same degree of support as in older animals. In the adult form of the condition, a mass or tumor is often found at the leading edge of the intussusception. These lesions may be intraluminal or intramural and may include parasitic nodules, caseocalcareous abscesses, and neoplasms. 1,4,14,20 The mass acts as an intestinal foreign body bulging into the lumen and predisposes to asynchronous peristalsis that forces one segment of bowel into its adjacent portion. In calves, postulated causative factors include dietary changes and viral and bacterial enteritis. These conditions may cause asynchronous peristalsis or hypermotility and predispose to intussusception. 24 Diagnosis The onset of clinical signs following intussusception is acute and is characterized by an abrupt change in attitude, anorexia, colic, and rapid decrease in milk production. The initial phase of severe abdominal pain is caused primarily by the tension on the mesentery as it is drawn into the intussuscipiens, and it persists for 6 to 12 hours. After the involved segment of intestine and its associated mesentery have become necrotic, signs of discomfort are less intense. The cow becomes progressively depressed as localized, and in late stages more generalized, peritonitis develops. Untreated cows often survive 5 to 10 days if the lesion is in the distal part of the small intestine, and they can be successfully operated upon several days after onset of clinical signs. 24 Abdominal distention becomes apparent within hours of the onset of colic. The abdomen first becomes pear-shaped when viewed from behind the cow. This results from the accumulation of fluid and gas in the small intestine proximal to the obstruction. Similarly, the ventral sac of the rumen starts to enlarge as the movement of digesta from the rumenoreticulum into the omasum and abomasum slows. In later stages of the condition, the abdomen appears round (apple-shaped) because of massive distention in the stomach compartments and in the proximal jejunoileum. 23 Feces often continue to be passed during the first few hours after intussusception as the distal part of the intestinal tract empties. There-
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after, the cow passes small amounts of sticky, dark red feces that consist of blood from the mucosal surface of the intussusceptum mixed with mucus from the distal portions of the intestinal tract. These feces are sometimes described as having a Hraspberry jam" appearance. 20 Simultaneous auscultation and percussion of the right surface of the abdomen may yield several small areas of tympanitic resonance, representing gas accumulation within segments of small intestine proximal to the intussusception. 19,24 Splashing sounds can be heard during succussion of the lower right flank with simultaneous auscultation in the paralumbar fossa. Examination of the abdominal cavity per rectum is often the single most helpful test in establishing the diagnosis of intussusception.24 Multiple loops of tightly distended small intestine can be felt throughout the right side of the abdominal cavity, filling the pelvic cavity, and often extending into the left side of the abdomen caudal to the rumen. The actual intussusception can often be felt as a firm or spongy coiled mass in the upper right portion of the abdomen. Fibrinous adhesions can be felt in the area, and the cow may exhibit a painful response to manipulation of the lesion. If the intussusception is located in the proximal jejunum, neither distended small intestine nor the lesion itself will be palpable, and one may seriously doubt the diagnosis even if all other parameters indicate the presence of intussusception. Similarly, distended bowel may not be felt in cows that are in mid to late gestation because the uterus is pushed caudally and dorsally into the pelvic inlet. Clinicopathologic parameters are seldom useful in establishing the diagnosis. They are more helpful in determining the severity of the disease process and in establishing the prognosis. As the cow's condition deteriorates, hemoconcentration and leukocytosis with left shift become evident. 25 Hypochloremic metabolic alkalosis with hypokalemia typically develops within 48 to 72 hours after distal small intestinal intussusception and much more rapidly following proximal obstruction. 25 Peritoneal fluid is voluminous and contains high concentrations of protein. The nucleated cell count may be normal or high, depending on the severity of peritonitis. Treatmenti5 Surgical correction should not be unnecessarily delayed, although it is important to adequately stabilize the cow before surgery. Intravenous fluid therapy to treat metabolic alkalosis is indicated if dehydration is present. This can be accomplished by the use of isotonic NaCI with the addition of 20 to 30 mEqJL of KCI. Some prefer to add small amounts of glucose to enhance intracellular movement of potassium. Parenteral antibiotic therapy should be initiated before surgery to ensure optimal tissue levels at the time of resection and anastomosis. Surgery is performed through the right paralumbar fossa. Although adequate exposure can usually be achieved with the cow standing, manipulation and tension on the mesentery may cause enough pain to make the cow attempt to lie down during the surgical procedure. If this becomes a problem, it may be advisable to close the abdomen
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temporarily, cast the cow, and proceed with the cow restrained in a recumbent position. 22 Locating the intussusception during surgical exploration is not difficult. Sweeping of the hand through the distended intestine generally will locate the lesion, either within or outside of the supraomental recess. With gentle traction, the intussusception can be exteriorized from the incision and packed off from the adjacent bowel. Attempting to manually reduce the intussusception is contraindicated because the bowel and associated mesentery are fragile and prone to tearing. Furthermore, because of the likelihood that the intussusception was caused by an intestinal mass, it is only logical to remove the offending bowel and thus to minimize the chance for recurrence. Wide resection of the bowel on each side of the intussusception is recommended, especially proximally, where the distention of the proximal bowel may have compromised the integrity of the vascular supply. Mesenteric vessels are ligated close to the bowel to avoid inadvertently cutting the continuation of the cranial mesenteric vessels, which traverse relatively close to the intestine. An end-to-end anastomosis using either an apposing or inverting technique provides accurate realignment of the intestinal lumen. Because the adult bovine mesentery contains large amounts of fat, the mesenteric border or CCangle" is wider than in many other species. 13 This has the potential of weakening the most compromised area of closure, that is, the mesenteric angle, where there is no serosal covering. Levine recently reported that the bursting wall tension of mesenteric border incisions was lower than that of antimesenteric incisions. 13 An end-to-end anastomosis in which one end is rotated approximately 30 relative to the other end (such as has been reported in human beingsll) may be useful in minimizing the likelihood of leakage of intestinal contents from the mesenteric angle. Following completion of the anastomosis, the mesenteric defect must be carefully closed. The intestine is rinsed and replaced within the supraomental recess, and the abdomen is closed. Postoperative care is routine and should include fluid and antibiotic therapy as indicated. Feces usually are passed within hours of the completion of surgery. Initially, these are copious and watery, but the feces soon become more formed and return to normal within days of surgery. Rapid and complete recovery should be expected in uncomplicated cases. 0
INTESTINAL VOLVULUS Volvulus results from twisting of a segment of intestine upon itself, thereby creating a closed loop obstruction. In addition to rapid distention of the portion of the bowel enclosed within the volvulus, the intestine proximal to the lesion becomes distended because of accumulation of intestinal contents. There are two relatively easily distinguishable forms of intestinal volvulus in cattle: segmental volvulus of the jejunoileum, and volvulus of the small (and large) intestine about the mesenteric root.
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SEGMENTAL VOLVULUS OF THE JEJUNOILEUM6,26
This type of volvulus usually affects the segment of jejunoileum suspended by the distal-most aspect of the mesenteric flange. Twisting of 180 to 360 is common, with the affected bowel often ending up snugly compacted within the caudal part of the abdomen and the pelvic inlet. Unlike horses and other species, cattle are not as likely to develop intestinal ischemia because the thick layer of mesenteric fat acts as a cushion and spares the major arteries from occlusion in early stages of the volvulus. In addition, the fat may actually prevent severe twisting of the intestine. Consequently, affected cattle do not deteriorate as rapidly as might otherwise be expected. 0
Diagnosis This condition occurs sporadically in cattle of all ages. Its cause is obscure, although ileus has been reported to be an inciting cause. I6 Onset of clinical signs is sudden and dramatic. Affected cows show signs of severe colic, more severe than that observed with intussusception or incarceration of similar segments of intestine. Signs of colic usually persist until the lesion is corrected, although the pain becomes less severe if ischemic necrosis of the affected bowel develops. As in cows with intussusception, the abdomen first appears pearshaped, then round and full when viewed from behind. 23 Feces may continue to be passed for several hours. However, after the colon becomes empty, there is complete cessation of fecal passage. Thick, tenacious mucus may be present within the rectum. Rectal examination reveals the presence of multiple tightly distended loops of small intestine, usually within the pelvic inlet and extending cranially as far as can be reached. The cow may exhibit pain when these loops are palpated. Tachycardia and hemoconcentration are present, the severity of which is determined by the duration of the illness and the amount of intestine involved in the twist. Some cows demonstrate a mild metabolic alkalosis with hypochloremia, although development of superimposed metabolic acidosis is to be anticipated as the condition progresses. Treatment Once the provisional diagnosis has been made, surgical repair should not be delayed, as affected cows generally deteriorate much more rapidly than cows with intussusception or incarceration. A right paralumbar fossa approach with the cow in a standing position is usually recommended as it facilitates manipulation, untwisting, and repositioning of the involved intestine within the distended abdominal cavity. This decision is generally made with the realization that ischemia, to the degree that resection of the involved bowel would become necessary, is seldom encountered. However, the decision to perform surgery with the cow standing or recumbent is usually dictated by the facilities at hand and the confidence one has in the accuracy of the provisional diagnosis.
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Exploration of the abdominal cavity reveals distention of the majority of the small intestine (proximal to the volvulus). The involved bowel is turgid and is usually located within the caudodorsal part of the peritoneal cavity at the pelvic inlet. Although difficult, exteriorization is usually necessary to permit untwisting of the bowel. A clear depressed and blanched line of demarcation across the mesentery confirms the diagnosis. Regardless of the need for resection, the use of antiprostaglandins before and during the surgical procedure is recommended to minimize the effects of toxin release after untwisting. Following reduction, the intestine is carefully returned to the supraomental recess, although the massive distention of all of the small intestine may make repositioning difficult. The prognosis is good and most cows recover rapidly and completely. Recurrence of the volvulus or development of clinically significant adhesions is rare. VOLVULUS
OF THE INTESTINE ABOUT THE MESENTERIC ROOT 18,!6,!9
Torsion of the mesenteric root results in volvulus of the jejunum, ileum, cecum, and the majority of the ascending colon. Only the duodenum and the parts of the colon located within the dorsal parts of the mesentery are spared. This is a most dramatic and rapidly fatal condition because of the large amount of intestine that undergoes acute vascular compromise. Diagnosis The predominant clinical sign is the peracute onset of severe unrelenting pain. A typically affected cow may first kick at her abdomen, then throw herself to the ground, roll onto her side, then jump to her feet and repeat the process. The heart rate is very high, and affected cows rapidly develop bilateral abdominal distention, giving them a round appearance when viewed from behind. Multiple areas of tympanitic resonance can be elicited over wide areas of the right side of the abdomen, usually centered in the paralumbar fossa, but extending cranially over the rib area. The prominent outline of tightly distended viscera may be seen though the right paralumbar fossa. On rectal examination, multiple loops of tightly distended small intestine, cecum, and colon can be felt throughout the entire caudal aspect of the abdomen. Tight bands of mesentery may be identified. Treatment This condition represents an acute medical and surgical emergency. Because of the need for rapid decompression and untwisting of the bowel, there is seldom time for transport of the cow to a referral surgical facility. A liberal right paralumbar fossa celiotomy is performed with the cow standing, if possible. As the peritoneal cavity is opened, distended intestine is readily apparent throughout the abdominal cavity. By carefully following the mesentery to its root, the site and
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direction of the twist can usually be identified. The volvulus can more easily be reduced after removal of gas from the larger segments of colon and cecum. Aggressive medical therapy is necessary during the preoperative and intraoperative periods. Prognosis for survival, even through the surgical period, is poor. Some cows succumb shortly after the bowel is untwisted, presumably as a result of release of toxins sequestered in the occluded vessels.
INCARCERATION, ENTRAPMENT, OR EXTRALUMINAL COMPRESSION During the past few years, there have been several reported cases of incarceration or entrapment of the small intestine in cattle. The distal flange of the jejunoileum is typically the primary site of such lesions, although they may occur throughout the jejunum or ileum. Reported causes of this form of obstruction include persistent vitelloumbilical band,IO persistent round ligament of the liver, 5 parovarianomental bands,17 persistent urachal remnant, 2 and remnant of the ductas deferens in steers. 30 Remnants of embryonal structures often persist as thin, tough ligamentous bands fixed at both ends. One end is usually attached to the body wall (often the umbilicus), and the other end is attached to a viscus, such as the liver (round ligament), ileum (vitelloumbilical band), or bladder (urachal remnant). Obstruction results when a segment of intestine wraps around, or becomes entrapped within, a loop formed by the band. The vascular supply to the segment of bowel is compromised and passage of digesta through the intestine ceases. This represents a true incarceration. Affected cows develop acute anorexia and visceral abdominal pain. They typically appear similar to cattle with intussusception. The offending band may occasionally be identified on examination per rectum. Surgical correction is achieved through a right paralumbar fossa celiotomy. The involved intestine is readily recognized and exteriorized if possible. The affected bowel should be handled carefully to minimize the risk of rupture. Sharp transection of the offending band results in immediate release of the incarceration. The bowel should then be carefully examined to determine whether resection is necessary. Unlike cows with intussusception, in which resection and anastomosis is almost always indicated, incarcerated bowel from the described causes often remains viable, and the cow makes a rapid and full recovery. Segments of the small intestine may also become incarcerated through a rent in the mesentery, either spontaneously or after intestinal resection in which the mesentery has not been adequately closed. 18,27 Clinical signs and surgical approach are similar to those described earlier. After identification of the involved segment of intestine, the herniated bowel is reduced by gentle traction, perhaps after enlarging the hole through which the bowel has become entrapped. Although rare, portions of the intestine may become compressed from the exterior by lipomatosis or fat necrosis. 3 Onset of signs is
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gradual; affected cows slowly become progressively hypophagic and pass smaller and smaller amounts of loose feces. Multiple loops of distended small intestine can be palpated on rectal examination, and the offending mass(es) of fat can sometimes be felt as hard structures embedded among the distended intestine. Effective surgical repair is seldom possible.
SCROTAL AND INGUINAL HERNIAS
External hernias resulting in incarceration or strangulation are unusual. I8 Umbilical or ventral abdominal hernias typically involve the abomasum or associated omentum. Scrotal or inguinal hernias involving the jejunoileum are seen predominantly in beef bulls. 18 Most hernias occur during the breeding season and involve the left side. Incarceration and strangulation seldom occur. The scrotum is enlarged unilaterally, either just at the neck region (inguinal hernia) or along the whole length of the scrotum (scrotal hernia).9 Careful palpation reveals the presence of gas and fluid-filled loops of small intestine. Definitive diagnosis can be made by rectal examination, in which the small intestine can be felt entering the inguinal canal. Surgical Repair Scrotal and inguinal hernias may be repaired through a left paralumbar fossa incision in a standing or recumbent bull, or through an incision over the inguinal canal with the bull positioned in lateral recumbency. Use of the paralumbar fossa technique assumes reducibility and viability of the herniated intestine. The incision is made in the ventral part of the paralumbar fossa approximately 12 cm dorsal to the fold of the flank. 9 The internal inguinal ring is located intra-abdominally, and the herniated segment of intestine is reduced. One or two large mattress sutures of nonabsorbable material are blindly placed through the margins of the internal inguinal ring. The ring must be closed sufficiently to avoid reherniation, although not so tightly as to cause compression of the spermatic cord. The abdominal cavity is closed in a routine manner. The inguinal or scrotal approach allows more direct access to the hernia. An incision is made over the external inguinal ring extending onto the neck of the scrotum. 18 The intestines should be reduced without incising the parietal tunic unless adhesions are present or compromised intestine is anticipated. The parietal tunic is reduced in size by placing sutures through its redundant portion. Part of the external inguinal ring is then sutured, being careful to leave sufficient space for the spermatic cord. Skin closure is routine. The testicle is retained in both of the described methods for surgical repair, although if necessary it can be removed readily by means of the inguinal approach.
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FUNCTIONAL OBSTRUCTION OF THE DUODENUM Functional obstruction of the sigmoid curve of the duodenum may be easily confused with right-sided abomasal displacement or volvulus. 28 Affected cows develop signs consistent with abomasal outflow failure, that is, anorexia, decreased milk production, progressive bilateral abdominal distention, and the presence of succussible fluid in the right cranial portion of the abdominal cavity. Some cows have easily recognizable gaseous abomasal tympany that can be detected over the last few ribs on the right side. Occasionally, the fluid-distended abomasum may be palpated on rectal examination, just caudal to the right costal arch. Affected cows are dehydrated and have tachycardia with severe hypochloremic metabolic alkalosis, hyponatremia, and hypokalemia. In a recent study of cows with obstruction of the proximal part of the duodenum, Garry also reported the presence of hyperglycemia and increased anion gap in affected cows, the latter thought to be due in part to prerenal azotemia and associated hyperphosphatemia and hyperproteinemia. 7 Surgical correction is by right paralumbar fossa celiotomy with the cow restrained in a standing position. The abomasum is decompressed, and a side-to-side anastomosis is performed between the cranial and descending parts of the duodenum. 28 This serves to bypass the sigmoid area of the duodenum, where the functional obstruction is thought to be present. Prognosis for full recovery is good.
REFERENCES 1. Archer RM, Cooley AJ, Hinchcliff KW, et al: Jejunojejunal intussusception associated with a transmural adenocarcinoma in an aged cow. J Am Vet Med Assoc 192:209-211, 1988 2. Baxter GM, Darien BJ, Wallace CE: Persistent urachal remnant causing intestinal strangulation in a cow. J Am Vet Med Assoc 191:555-558, 1987 3. Bridge PS, Spratling FR: Bovine lipomatosis. Vet Rec 74:1357-1362,1962 4. Bossard JK: Telescoped intestines in cattle. Cornell Vet 20:55-58, 1930 5. Ducharme NG, Smith DF, Koch DB: Small intestinal obstruction caused by a persistent round ligament of the liver in a cow. J Am Vet Med Assoc 180:1234-1236, 1982 6. Fubini SL, Smith DF, Tithof PK, et al: Volvulus of the distal part of the jejunoileum in four cows. Vet Surg 15:150-152, 1986 7. Garry F, Hull BL, Rings DM, et al: Comparison of naturally occurring proximal duodenal obstruction and abomasal volvulus in dairy cattle. Vet Surg 17:226-233, 1988 8. Habel RE: Ruminant digestive system. In Getty R (ed): Sisson and Grossman's Anatomy of the Domestic Animals, ed 5. Philadelphia, WB Saunders, 1975, pp 903-908 9. Hofmeyr CFB: Ruminant Urogenital Surgery. Ames, Iowa State University, 1987, pp 32-34 10. Koch DB, Robertson IT, Donawick WJ: Small intestinal obstruction due to persistent vitello umbilical band in a cow. J Am Vet Med Assoc 173:197 -200, 1978 11. LaCalle JP, Sole JMG, Pey CG, et al: Rotated intestinal anastomoses. Surg Gynecol Obstet 154:662-666, 1982
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12. Levine SA, Smith DF, Wilsman NJ, et al: Arterial and venous supply to the bovine jejunum and proximal part of the ileum. Am J Vet Res 48:1295-1299, 1987 13. Levine SA, Smith DF, Wilson JW, et al: Comparative healing of mesenteric and antimesenteric incisions in the bovine jejunum. Am J Vet Res 49:1339-1343, 1988 14. Pearson H: Intussusception in cattle. Vet Rec 89:426-437, 1971 15. Pearson H: The treatment of surgical disorders of the bovine abdomen. Vet Rec 92:245-254, 1973 16. Pearson H, Pincent PJN: Intestinal obstruction in cattle. Vet Rec 101:162-166, 1977 17. Richardson DW: Paraovarian-omental bands as a cause of small intestinal obstruction in cows. J Am Vet Med Assoc 185:517 -519, 1984 18. Robertson JT: Differential diagnosis and surgical management of intestinal obstruction in cattle. Vet Clin North Am [Large Anim Pract] 1:377 -394, 1979 19. Smith DF, Erb HN, Kallaher KM, et al: The identification of structures and conditions responsible for right side tympanitic resonance (ping) in adult cattle. Cornell Vet 72:180-199, 1982 20. Smith DF: Intussusception in adult cattle. Comp Cont Ed Pract Vet II:S49-S53, 1980 21. Smith DF: Bovine intestinal surgery. Part 1: Surgical anatomy. Mod Vet Pract 65:705-710, 1984 22. Smith DF: Bovine intestinal surgery. Part 2: Surgical exploration. Mod Vet Pract 65:853-857, 1984 23. Smith DF: Bovine intestinal surgery. Part 3: Clinical examination. Mod Vet Pract 65:909-914, 1984 24. Smith DF: Bovine intestinal surgery. Part 5: Intussusception. Mod Vet Pract 66:405-409, 1985 25. Smith DF: Bovine intestinal surgery. Part 6: Intussusception (continued). Mod Vet Pract 66:443 - 446, 1985 26. Smith DF: Bovine intestinal surgery. Part 7: Intestinal volvulus. Mod Vet Pract 66:995-999, 1985 27. Trent AM, Bailey JV: Herniation of the small intestine through the right lateral ligament of the bladder in a bull. Can Vet J 26:16-19, 1985 28. Velden MA Van der: Functional stenosis of the sigmoid curve of the duodenum in cattle. Vet Rec 112:452-453, 1983 29. Willet MDJ: Intestinal torsion in cattle. NZ Vet J 18:42-43, 1970 30. Wolfe DW, Mysinger PW, Carson RL, et al: Incarceration of a section of small intestine by remnants of the ductus deferens in steers. J Am Vet Med Assoc 191:1597 -1598, 1987
Address reprint requests to Donald F. Smith, DVM Department of Clinical Sciences New York State College of Veterinary Medicine Cornell University Ithaca, NY 14853
