1991, The British Journal of Radiology, 64, Ill-Yl^
Case reports
Computed tomography of lesser sac hernia through the gastrohepatic omentum By *T. L Tran, MB BS, FRCS, FRCR, F. Regan, MB BS, MRCP and M. A. 0. Al-Kutoubi, MD, DMRD, FRCR Department of Radiology, St Mary's Hospital, Praed Street, London W2 1 NY, UK {Received May 1990 and in revised form July 1990)
Keywords: Computed tomography, Gastrointestinal tract, Internal hernia, Lesser sac, Gastrohepatic omentum
Internal hernia is an unusual cause of intestinal obstruction and pre-operative diagnosis on plain films has seldom been made. Before the introduction of computed tomography (CT), the literature on the subject was composed principally of case reports, often based on observations made at surgery or autopsy. However, with the increasing use of CT, pre-operative diagnosis of paraduodenal hernias has been made (Passas et al, 1986; Day et al, 1988). We report a case of lesser sac hernia through a rare congenital defect in the gastrohepatic *Author for correspondence.
omentum. The diagnosis, based on the findings of CT, was made pre-operatively. The CT appearance of the condition has not been described in the literature previously. Case report A previously healthy 24-year-old female presented with a 6-hour history of epigastric colicky abdominal pain and clear vomiting. She was apyrexial and normotensive with a pulse rate of 90/min. Her abdomen was not distended but was tender with guarding in the epigastric region. Initial laboratory findings included a leucocytosis of 13 000, normal serum biochemistry and serum amylase. Supine and erect abdominal radiographs
(b) Figure 1. (a) Supine and (b) erect abdominal radiographs on admission, demonstrating a circumscribed collection of dilated loops of small bowel in the lesser sac, compressing and displacing the stomach laterally. The large arrow shows small bowel loops ascending and descending towards the hepatorenal fossa before herniating into the lesser sac. Note that the signs of intestinal obstruction in the abdominal area below the lesser sac are minimal despite complete obstruction of the hernia.
372
The British Journal of Radiology, April 1991
Case reports duodeno-jejunal junction. The bowel was resected and the defect was closed. She made an uneventful recovery and has been asymptomatic since her discharge from hospital. Discussion
Figure 2. Computed tomograph of the abdomen at the level of the foramen of Winslow demonstrating loops of small bowl with thickened walls in the lesser sac. The stomach with the nasogastric tube in situ is displaced anteriorly. The splenic flexure and the descending colon are compressed and displaced. Note that anterior to the portal triad which form the anterior edge of the foramen of Winslow, there are loops of small bowel which are continuous with the small bowel in the lesser sac, thus allowing possible differentiation of hernia through the gastrohepatic omentum from hernia through the foramen of Winslow. The congenital defect in the gastrohepatic omentum is the area extending from the lesser curvature of the stomach (arrow) to the portal triad.
(Fig. 1) on admission revealed a circumscribed collection of dilated loops of small bowel in the upper abdomen medial to the stomach shadow which was also noted to be moderately distended. In accordance with the clinical diagnosis of small bowel obstruction, she was treated with intravenous fluid and nasogastric tube suction. The following day, her abdominal symptoms remained unresolved. Abdominal radiographs were repeated which revealed no change in the appearance of the dilated small bowel loops in the upper abdomen. Serum amylase was repeated and found to be elevated at 534 units/1. A diatrizoate meglumine-diatrizoate sodium (gastrografin) meal and follow-through was performed. A 30 minute film demonstrated compression of the gastric outlet and the lesser curvature by the dilated small bowel loops, and no contrast medium was seen distal to the pylorus. The appearances were thought to be due to ileus, probably due to acute pancreatitis. Abdominal CT was performed as an emergency. Computed tomography demonstrated the small bowel loops with thickened walls sandwiched between the stomach and the retroperitoneal structures: the pancreas and the left kidney which form the posterior wall of the lesser sac (Fig. 2). The stomach with the nasogastric tube in situ was displaced anteriorly. The splenic flexure and descending colon were compressed and displaced posterolaterally. A diagnosis of lesser sac hernia was made. The abdominal radiographs were reviewed and herniation through the foramen of Winslow was thought to be the most likely cause. At surgery, 125 cm of jejunum had herniated through a defect in the gastrohepatic omentum just medial to the portal triad, measuring 4 cm in diameter. The bowel was gangrenous and the proximal viable margin was only 30 cm from the
Vol. 64, No. 760
Internal hernias constitute only 1 % of all intraperitoneal causes of intestinal obstruction. In the majority, herniation occurs through one of the peritoneal recesses, the commonest being the paraduodenal fossa, representing 53% of all internal hernias (Hansmann & Morton, 1939). Herniation into the lesser sac may occur through one of the following structures: the foramen of Winslow, the transverse mesocolon, the greater omentum or the gastrohepatic omentum (Stewart, 1962). The commonest method is through the foramen of Winslow, constituting 8% of all internal hernias (Hansmann & Morton, 1939). Herniation through a primary opening in the gastrohepatic omentum is exceedingly rare, the only published case was that of Gants and Ryle (1953). Defects in the gastrohepatic omentum, through which herniation occurs, can be congenital or acquired. Of the acquired type, both surgical and blunt abdominal trauma have been implicated. In the case described by Gants and Ryle (1953), the defect was probably secondary to crush injury sustained 3 years previously, and through which herniation of the greater omentum and transverse colon occurred with resultant partial volvulus of the stomach. The gastrohepatic omental defect in our case was probably congenital since there was no previous history of any abdominal trauma or operation and the margins of the defect were smooth and well formed with no adhesions in the periphery. The predisposing causes of internal herniation through the gastrohepatic omentum are unknown. In our case, the event was spontaneous with no apparent cause found in the patient's history or at surgery. Nonetheless, the majority of internal hernias result from congenital anomalies of intestinal rotation and peritoneal attachments (Pennel & Shaffner, 1971). The gastrohepatic omentum is normally shielded by the liver in the hepatorenal fossa. Access of viscus to the hepatorenal fossa is facilitated when the greater omentum is atrophic and loops of intestine are rendered mobile due to abnormally long mesentery (Erskine, 1967). It is possible that alteration in intra-abdominal pressure including parturition, vomiting and straining may provoke the onset of internal herniation in those patients with an anatomical predisposition (Erskine, 1967). The radiographic appearances of intestine in the lesser sac may be characteristic and when correctly interpreted could lead to the diagnosis (Stewart, 1962). The essential findings are a circumscribed collection of loops of gas-containing intestine in the upper abdomen medial and posterior to the stomach, associated with mechanical intestinal obstruction. The stomach is usually displaced anteriorly and to the left side with extrinsic pressure on the lesser curvature. In our case, the appearances on the abdominal radiographs were characteristic but misinterpreted. 373
Case reports
The exact nature of the gas collection may be difficult to interpret; this problem can be overcome by aspirating the stomach with a nasogastric tube and then repeating the film, obtaining in addition a lateral view preferably in an erect position. Distinction from other conditions which can present with gas in the lesser sac, such as perforated gastric ulcer or abscess, is possible by identification of the presence of a mucosal pattern and fluid levels within the herniated bowel. If thefindingsare still equivocal, valuable information can usually be gained by barium studies of the gastrointestinal tract when clinical condition allows. A soluble contrast meal was performed in our case but was unhelpful as the contrast medium could not pass beyond the gastric outlet which was completely obstructed by the herniated intestine. Computed tomography provides excellent delineation of the structures forming the boundaries of the lesser sac. In the case described and illustrated here, CT clearly demonstrated the small bowel loops in the lesser sac, allowing a confident diagnosis pre-operatively (Fig. 2). Computed tomography is helpful in elucidating the nature of the gas collection in the lesser sac, especially when the radiographic findings are uncharacteristic. It is also helpful in differentiating a true hernia from other conditions such as abscess and perforated viscus which may present with gas in the lesser sac. In the event of a hernia, the fluid levels are confined to the intestinal loops and do not conform to the anatomical recesses of the lesser sac. Other structures such as greater omentum and gall bladder, which have been found in the lesser sac after herniating through the foramen of Winslow (Erskine, 1967), are more readily demonstrated on CT than on plain radiographs. Paraduodenal hernias, in particular those on the left side, may present with a circumscribed collection of loops of bowel in the left upper abdomen indenting the posterior wall of the stomach. Computed tomography can differentiate these from a lesser sac hernia by demonstrating the retroperitoneal position of the herniated intestine behind and to the left of the body of the pancreas (Passes et al, 1986). It may also demonstrate a loop of bowel interposed between the stomach and the body of the pancreas due to the duodeno-jejunal flexure which is antero-medially displaced by the herniated intestine (Day et al, 1988). In our case, owing to the obstruction of the gastric outlet, the signs of intestinal obstruction in the abdominal area below the lesser sac were minimal (Fig. 1). A loop of small bowel ascending towards the hepatorenal
374
fossa before joining the herniated intestine could also be identified; this had led to the initial misdiagnosis of hernia through the foramen of Winslow. Erskine (1967) reviewed the literature on lesser sac hernia through the foramen of Winslow and found a number of these patients had demonstrated these radiographic features. The obstruction of the gastric outlet is due to either the loop of bowel passing across the duodenum before herniating into the lesser sac or the intestinal loops at the hernial ring, therefore air will not pass down into the intestine, and typical signs of obstruction are either absent or minimal even though the intestine in the hernia is completely obstructed. Our case has also demonstrated that hernia through the gastrohepatic omentum can not be differentiated from hernia through the foramen of Winslow on plain films but CT may be able to do this by demonstrating intestinal loops anterior to the foramen of Winslow before joining the intestine in the lesser sac (Fig. 2). The defect in the gastrohepatic omentum can, in retrospect, be seen on the CT images as the area extending from the lesser curvature of the stomach to the portal triad. In summary, when dealing with patients with acute abdomen, the possibility of the condition should be kept in mind and, with careful interpretation of the radiology, pre-operative diagnosis can be made. The plain radiographic findings could be characteristic and diagnostic. However, when the radiographic findings are equivocal and barium studies are unhelpful or contraindicated, CT may readily provide the diagnosis.
References DAY, D. L., DRAKE, D. G., LEONARD, A. S. & LETOURNEAU,
J. G., 1988. CT findings in left paraduodenal herniae. Gastrointestinal Radiology, 13, 27-29. ERSKINE, J. M., 1967. Hernia through the foramen of Winslow. Surgery, Gynecology and Obstetrics, 125, 1093-1109. GANTS, R. T. & RYLE, J. W., 1953. Hernia of stomach and
colon into the omental bursa through a defect in the gastrohepatic ligament. Annals of Surgery, 137, 285-288. HANSMANN, G. H. & MORTON, S. A., 1939. Intra-abdominal
hernia. Archives of Surgery, 39, 973-984. PASSAS, V., KARAVIAS, D., GRILIAS, D. & BIRBAS, A., 1986.
Computed tomography of left paraduodenal hernia. Journal of Computer Assisted Tomography, 10, 542-543. PENNELL, T. C. & SHAFFNER, L. S., 1971. Congenital internal
hernia. Surgical Clinics of North America, 51, 1355-1359. STEWART, J. O. R., 1962. Lesser sac hernia. British Journal of Surgery, 50, 321-326.
The British Journal of Radiology, April 1991
Case reports
Computed tomography of lesser sac hernia through the gastrohepatic omentum By *T. L Tran, MB BS, FRCS, FRCR, F. Regan, MB BS, MRCP and M. A. 0. Al-Kutoubi, MD, DMRD, FRCR Department of Radiology, St Mary's Hospital, Praed Street, London W2 1 NY, UK {Received May 1990 and in revised form July 1990)
Keywords: Computed tomography, Gastrointestinal tract, Internal hernia, Lesser sac, Gastrohepatic omentum
Internal hernia is an unusual cause of intestinal obstruction and pre-operative diagnosis on plain films has seldom been made. Before the introduction of computed tomography (CT), the literature on the subject was composed principally of case reports, often based on observations made at surgery or autopsy. However, with the increasing use of CT, pre-operative diagnosis of paraduodenal hernias has been made (Passas et al, 1986; Day et al, 1988). We report a case of lesser sac hernia through a rare congenital defect in the gastrohepatic *Author for correspondence.
omentum. The diagnosis, based on the findings of CT, was made pre-operatively. The CT appearance of the condition has not been described in the literature previously. Case report A previously healthy 24-year-old female presented with a 6-hour history of epigastric colicky abdominal pain and clear vomiting. She was apyrexial and normotensive with a pulse rate of 90/min. Her abdomen was not distended but was tender with guarding in the epigastric region. Initial laboratory findings included a leucocytosis of 13 000, normal serum biochemistry and serum amylase. Supine and erect abdominal radiographs
(b) Figure 1. (a) Supine and (b) erect abdominal radiographs on admission, demonstrating a circumscribed collection of dilated loops of small bowel in the lesser sac, compressing and displacing the stomach laterally. The large arrow shows small bowel loops ascending and descending towards the hepatorenal fossa before herniating into the lesser sac. Note that the signs of intestinal obstruction in the abdominal area below the lesser sac are minimal despite complete obstruction of the hernia.
372
The British Journal of Radiology, April 1991
Case reports duodeno-jejunal junction. The bowel was resected and the defect was closed. She made an uneventful recovery and has been asymptomatic since her discharge from hospital. Discussion
Figure 2. Computed tomograph of the abdomen at the level of the foramen of Winslow demonstrating loops of small bowl with thickened walls in the lesser sac. The stomach with the nasogastric tube in situ is displaced anteriorly. The splenic flexure and the descending colon are compressed and displaced. Note that anterior to the portal triad which form the anterior edge of the foramen of Winslow, there are loops of small bowel which are continuous with the small bowel in the lesser sac, thus allowing possible differentiation of hernia through the gastrohepatic omentum from hernia through the foramen of Winslow. The congenital defect in the gastrohepatic omentum is the area extending from the lesser curvature of the stomach (arrow) to the portal triad.
(Fig. 1) on admission revealed a circumscribed collection of dilated loops of small bowel in the upper abdomen medial to the stomach shadow which was also noted to be moderately distended. In accordance with the clinical diagnosis of small bowel obstruction, she was treated with intravenous fluid and nasogastric tube suction. The following day, her abdominal symptoms remained unresolved. Abdominal radiographs were repeated which revealed no change in the appearance of the dilated small bowel loops in the upper abdomen. Serum amylase was repeated and found to be elevated at 534 units/1. A diatrizoate meglumine-diatrizoate sodium (gastrografin) meal and follow-through was performed. A 30 minute film demonstrated compression of the gastric outlet and the lesser curvature by the dilated small bowel loops, and no contrast medium was seen distal to the pylorus. The appearances were thought to be due to ileus, probably due to acute pancreatitis. Abdominal CT was performed as an emergency. Computed tomography demonstrated the small bowel loops with thickened walls sandwiched between the stomach and the retroperitoneal structures: the pancreas and the left kidney which form the posterior wall of the lesser sac (Fig. 2). The stomach with the nasogastric tube in situ was displaced anteriorly. The splenic flexure and descending colon were compressed and displaced posterolaterally. A diagnosis of lesser sac hernia was made. The abdominal radiographs were reviewed and herniation through the foramen of Winslow was thought to be the most likely cause. At surgery, 125 cm of jejunum had herniated through a defect in the gastrohepatic omentum just medial to the portal triad, measuring 4 cm in diameter. The bowel was gangrenous and the proximal viable margin was only 30 cm from the
Vol. 64, No. 760
Internal hernias constitute only 1 % of all intraperitoneal causes of intestinal obstruction. In the majority, herniation occurs through one of the peritoneal recesses, the commonest being the paraduodenal fossa, representing 53% of all internal hernias (Hansmann & Morton, 1939). Herniation into the lesser sac may occur through one of the following structures: the foramen of Winslow, the transverse mesocolon, the greater omentum or the gastrohepatic omentum (Stewart, 1962). The commonest method is through the foramen of Winslow, constituting 8% of all internal hernias (Hansmann & Morton, 1939). Herniation through a primary opening in the gastrohepatic omentum is exceedingly rare, the only published case was that of Gants and Ryle (1953). Defects in the gastrohepatic omentum, through which herniation occurs, can be congenital or acquired. Of the acquired type, both surgical and blunt abdominal trauma have been implicated. In the case described by Gants and Ryle (1953), the defect was probably secondary to crush injury sustained 3 years previously, and through which herniation of the greater omentum and transverse colon occurred with resultant partial volvulus of the stomach. The gastrohepatic omental defect in our case was probably congenital since there was no previous history of any abdominal trauma or operation and the margins of the defect were smooth and well formed with no adhesions in the periphery. The predisposing causes of internal herniation through the gastrohepatic omentum are unknown. In our case, the event was spontaneous with no apparent cause found in the patient's history or at surgery. Nonetheless, the majority of internal hernias result from congenital anomalies of intestinal rotation and peritoneal attachments (Pennel & Shaffner, 1971). The gastrohepatic omentum is normally shielded by the liver in the hepatorenal fossa. Access of viscus to the hepatorenal fossa is facilitated when the greater omentum is atrophic and loops of intestine are rendered mobile due to abnormally long mesentery (Erskine, 1967). It is possible that alteration in intra-abdominal pressure including parturition, vomiting and straining may provoke the onset of internal herniation in those patients with an anatomical predisposition (Erskine, 1967). The radiographic appearances of intestine in the lesser sac may be characteristic and when correctly interpreted could lead to the diagnosis (Stewart, 1962). The essential findings are a circumscribed collection of loops of gas-containing intestine in the upper abdomen medial and posterior to the stomach, associated with mechanical intestinal obstruction. The stomach is usually displaced anteriorly and to the left side with extrinsic pressure on the lesser curvature. In our case, the appearances on the abdominal radiographs were characteristic but misinterpreted. 373
Case reports
The exact nature of the gas collection may be difficult to interpret; this problem can be overcome by aspirating the stomach with a nasogastric tube and then repeating the film, obtaining in addition a lateral view preferably in an erect position. Distinction from other conditions which can present with gas in the lesser sac, such as perforated gastric ulcer or abscess, is possible by identification of the presence of a mucosal pattern and fluid levels within the herniated bowel. If thefindingsare still equivocal, valuable information can usually be gained by barium studies of the gastrointestinal tract when clinical condition allows. A soluble contrast meal was performed in our case but was unhelpful as the contrast medium could not pass beyond the gastric outlet which was completely obstructed by the herniated intestine. Computed tomography provides excellent delineation of the structures forming the boundaries of the lesser sac. In the case described and illustrated here, CT clearly demonstrated the small bowel loops in the lesser sac, allowing a confident diagnosis pre-operatively (Fig. 2). Computed tomography is helpful in elucidating the nature of the gas collection in the lesser sac, especially when the radiographic findings are uncharacteristic. It is also helpful in differentiating a true hernia from other conditions such as abscess and perforated viscus which may present with gas in the lesser sac. In the event of a hernia, the fluid levels are confined to the intestinal loops and do not conform to the anatomical recesses of the lesser sac. Other structures such as greater omentum and gall bladder, which have been found in the lesser sac after herniating through the foramen of Winslow (Erskine, 1967), are more readily demonstrated on CT than on plain radiographs. Paraduodenal hernias, in particular those on the left side, may present with a circumscribed collection of loops of bowel in the left upper abdomen indenting the posterior wall of the stomach. Computed tomography can differentiate these from a lesser sac hernia by demonstrating the retroperitoneal position of the herniated intestine behind and to the left of the body of the pancreas (Passes et al, 1986). It may also demonstrate a loop of bowel interposed between the stomach and the body of the pancreas due to the duodeno-jejunal flexure which is antero-medially displaced by the herniated intestine (Day et al, 1988). In our case, owing to the obstruction of the gastric outlet, the signs of intestinal obstruction in the abdominal area below the lesser sac were minimal (Fig. 1). A loop of small bowel ascending towards the hepatorenal
374
fossa before joining the herniated intestine could also be identified; this had led to the initial misdiagnosis of hernia through the foramen of Winslow. Erskine (1967) reviewed the literature on lesser sac hernia through the foramen of Winslow and found a number of these patients had demonstrated these radiographic features. The obstruction of the gastric outlet is due to either the loop of bowel passing across the duodenum before herniating into the lesser sac or the intestinal loops at the hernial ring, therefore air will not pass down into the intestine, and typical signs of obstruction are either absent or minimal even though the intestine in the hernia is completely obstructed. Our case has also demonstrated that hernia through the gastrohepatic omentum can not be differentiated from hernia through the foramen of Winslow on plain films but CT may be able to do this by demonstrating intestinal loops anterior to the foramen of Winslow before joining the intestine in the lesser sac (Fig. 2). The defect in the gastrohepatic omentum can, in retrospect, be seen on the CT images as the area extending from the lesser curvature of the stomach to the portal triad. In summary, when dealing with patients with acute abdomen, the possibility of the condition should be kept in mind and, with careful interpretation of the radiology, pre-operative diagnosis can be made. The plain radiographic findings could be characteristic and diagnostic. However, when the radiographic findings are equivocal and barium studies are unhelpful or contraindicated, CT may readily provide the diagnosis.
References DAY, D. L., DRAKE, D. G., LEONARD, A. S. & LETOURNEAU,
J. G., 1988. CT findings in left paraduodenal herniae. Gastrointestinal Radiology, 13, 27-29. ERSKINE, J. M., 1967. Hernia through the foramen of Winslow. Surgery, Gynecology and Obstetrics, 125, 1093-1109. GANTS, R. T. & RYLE, J. W., 1953. Hernia of stomach and
colon into the omental bursa through a defect in the gastrohepatic ligament. Annals of Surgery, 137, 285-288. HANSMANN, G. H. & MORTON, S. A., 1939. Intra-abdominal
hernia. Archives of Surgery, 39, 973-984. PASSAS, V., KARAVIAS, D., GRILIAS, D. & BIRBAS, A., 1986.
Computed tomography of left paraduodenal hernia. Journal of Computer Assisted Tomography, 10, 542-543. PENNELL, T. C. & SHAFFNER, L. S., 1971. Congenital internal
hernia. Surgical Clinics of North America, 51, 1355-1359. STEWART, J. O. R., 1962. Lesser sac hernia. British Journal of Surgery, 50, 321-326.
The British Journal of Radiology, April 1991
