Eur J Trauma Emerg Surg DOI 10.1007/s00068-015-0516-x
REVIEW ARTICLE
“Management of blunt renal injury: what is new?” B. Kautza1 · B. Zuckerbraun1 · A. B. Peitzman1
Received: 29 October 2014 / Accepted: 11 March 2015 © Springer-Verlag Berlin Heidelberg 2015
Abstract The diagnosis, workup and management of blunt renal injury have evolved greatly over the past decades. Evaluation and management of blunt renal injury echoes the increasing success of nonoperative management in other blunt abdominal solid organ injury, such as liver and spleen. Decision-making difficulties still remain regarding the optimal imaging, grading and degree of interventional or operative exploration used. Increasingly, initial nonoperative management has gained acceptance and appears to be applicable even high-grade injuries. Emerging techniques in highly sensitive imaging as well as interventional angiography have allowed safe nonoperative management in the appropriate patient. This review will focus on the contemporary workup and management of blunt renal injury while focusing on some of the emerging literatures in regard to refined imaging and grading of injuries as well as techniques to increase the success of nonoperative management. Keywords Trauma · Blunt · Renal injury · Nonoperative · Kidney
Introduction Renal injury is relatively uncommon and may be difficult to diagnose, and many aspects of treatment remain controversial. Renal injuries are seen in 1–5 % of all trauma patients, the great majority from blunt mechanisms (~90 %) [1–3]. Recent series in Ireland and the UK demonstrated incidences of 10.25
* A. B. Peitzman [email protected] 1
Department of Surgery, University of Pittsburgh, F1200 PUH 200 Lothrop St, Pittsburgh, PA 15213, USA
and 50 cases per million person-years, respectively, with blunt injuries again being the predominant mechanism [4, 5]. Since the first reports of renal trauma in the 1800s [6], the literature produced sporadic case reports or patient series. The paucity of early literature and accurate imaging tools made diagnosis and treatment of blunt renal injuries (BRI) difficult. Recommendations in earlier literature were divided on whether operative or nonoperative management was preferable for the non-exsanguinating patient [7–12]. However, based upon successful outcomes of nonoperative approaches over the past half century [13, 14], nonoperative management of BRI has become the standard in the majority of BRI [15–18]. The trend toward nonoperative management mirrors that of other solid organ injuries, including liver and spleen [19, 20]. Introduction of computed tomography (CT) and a uniform grading system that allowed accurate comparison of renal injuries have revolutionized diagnosis and management of BRI. Furthermore, the promulgation of angiography and endovascular interventions has added a new dimension to treatment of BRI. The American Association for the Surgery of Trauma Organ Injury Scale (AAST-OIS) is applicable across trauma centers and has greatly enhanced clinical research [21–24] (Table 1). Additionally, the adoption of protocols and guidelines across trauma systems has allowed more standardized care and better outcomes [25, 26]. This review will highlight some of the evolving management strategies and continued unanswered controversies in the management of BRI. Our literature search included PubMed, Cochrane and Google Scholar search engines.
Initial workup and evaluation of BRI The initial management of trauma patients injured via blunt force mechanisms should focus on primary life-threatening
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B. Kautza et al. Table 1 Kidney injury scale Gradea
Type of injury
Description of injury
I
Contusion Hematoma Hematoma Laceration Laceration Laceration Vascular
Microscopic or gross hematuria, urologic studies normal Subcapsular, non expanding without parenchymal laceration Nonexpanding perirenal hematoma confirmed to renal retroperitoneum 1.0 cm parenchymal depth of renal cortex without collecting system rupture or urinary extravasation Parenchymal laceration extending through renal cortex, medulla, and collecting system Main renal artery or vein injury with contained hemorrhage
Laceration
Completely shattered kidney
Vascular
Avulsion of renal hilum which devascularizes kidney
II III IV V a
Advance one grade for bilateral injuries up to grade III
injuries with additional advanced imaging and procedures done only when medically appropriate. Patients with hemodynamic instability and signs of exsanguination require prompt operative intervention. In hemodynamically normal patients and those who respond appropriately to resuscitation, advanced imaging will allow identification and evaluation of other injuries. CT has improved the identification of BRI, and of all advances in trauma care, the diagnosis and staging of BRI by CT may have the greatest impact to guide the subsequent management. Anatomy and mechanism The kidney’s anatomic location, lying high in the retroperitoneum with the renal pedicle and PUJ the only major attachment points, makes them relatively well protected. Given the well-protected location, only major forces applied result in significant renal injury, which also accounts for the high incidence of other intra-abdominal injuries in association with BRI [27, 28]. BRI is typically due to forces causing either a direct impact, with motor vehicle accidents comprising the vast majority, or indirect damage that causes sudden displacement of the kidney (e.g., fall from height) [1]. The majority of renal injuries are minor with 90 % of renal injuries comprised of injury to the parenchyma or segmental vessels [29]. More severe injuries including major lacerations, involving hilar vessels, are seen in up to 25 % of bluntly injured patients [30– 33]. Often these injuries are associated with mechanisms involving significant deceleration forces [28]. Initial evaluation and imaging Initial evaluation of the bluntly injured patient must take into account the overall condition of the patient in the context of the hospital setting and resources. The hemodynamic status of the patient is the most important determinant in early management of the patient with BRI.
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Hemodynamic stability allows further investigation during the initial assessment of the blunt trauma victim. Concern for renal trauma can be suspected from signs on the physical examination such as rib fractures or flank ecchymosis [34]. The use of the urinalysis to detect hematuria is important in assessment of a patient with suspected BRI [29]. Hematuria is commonly transient, and collection of the urinalysis on the first void is important [35]. In the patient with suspected BRI, determination between microscopic and gross hematuria does have predictive value in determining the presence of a major renal injury [33]. It has been shown that hematuria can be seen in up 94 % of renal trauma cases, although this common sign does not predict the severity of the injury [36, 37]. Urinalysis for hematuria is done either as microscopic or dipstick [38]. Hematuria can also be associated with injury anywhere in the urinary system including the ureter, bladder and urethra. The presence of hematuria of any degree, combined with highenergy mechanism and concerning physical examination, should raise the possibility of BRI and warrants imaging. Today, advanced imaging of stable patients suspected of having BRI is largely by CT. A group of international authors stated in a consensus paper that radiographic imaging of renal trauma has four main objectives: (1) accurately stage the injury, (2) identify preexisting renal pathology, (3) document the function/presence of the uninjured kidney and (4) identify injuries to other intra-abdominal organs [29]. Contemporary staging is through the application of AAST-OIS to findings on CT. Historically, intravenous urography and renal angiography were the main modalities used in staging BRIs [29, 39]. However, these have been replaced by CT based upon the ease and availability of obtaining CT, the high sensitivity of CT for detecting BRI and of course the ability of CT to detect other injuries. CT with intravenous contrast administration reliably reveals vascular injury, lacerations, urinary extravasation as well as hematomas, making this modality
Management of blunt renal injury…
ideal for grading BRIs [32, 40]. Initial CT arteriovenous phase images allow determination of arterial/vascular injury; however, determination of collecting system injury requires delayed imaging. Contemporary CT imaging protocols for suspected BRI typically consist of initial imaging with contrast administration. Although the initial imaging does not reliably determine whether there is injury to the collecting system, the presence of a more substantial injury should prompt obtaining delayed images 10–20 min after contrast injection to evaluate for collections or extravasation of the contrast consistent with injury to the collecting system [41]. Recently, the use of ultrasound (US) to initially identify BRI has been more widely used. US has the benefit of being noninvasive and can be rapidly done when available. In experienced hands, the use of US may provide vital information regarding the presence of BRI [42]; however, limitations do exist. US does not reliably detect major vascular injury and has more user variability and decreased sensitivity compared to CT [43]. New US techniques including real-time 3D-enhanced imaging are being developed and may show promise in the future [44]. US has been shown to be useful in follow-up imaging, particularly in the diagnosis of post-trauma fluid collections and hydronephrosis. Follow‑up imaging The increase in nonoperative management of BRI has led to the question of whether routine use of follow-up imaging is beneficial. In theory, routine follow-up imaging would allow identification and treatment of complications prior to any clinical deterioration. It has been recommended that routine follow-up radiographic studies be done within 48–96 h to identify progression or complications that may arise [45]. In a recent study, routine imaging changed treatment decisions in less than 1 % of patients, but repeat imaging obtained on a clinical indication altered treatment in 20 % [46]. Another investigation showed that grade III or lower BRI did not develop complications, and the 11.1 % of BRI who did develop complications were all symptomatic, suggesting that selective follow-up imaging based on laboratory and clinical signs is safe [47]. A recent investigation suggested benefit for routine follow-up imaging for all grade IV and V injuries diagnosed on initial CT [48]. Although there is no general consensus regarding followup imaging, radiographic studies should be obtained when clinical (fever, flank pain/mass, bleeding, etc.) or laboratory values indicate concern for complication [29].
mortality in BRI [24] (Table 1). Grade I refers to contusion or nonexpanding subcapsular hematoma without parenchymal laceration. Grade II is a nonexpanding perirenal hematoma confined to the retroperitoneum or a less than 1 cm cortical laceration without urinary extravasation. Grade III is a greater than 1 cm cortical laceration without collecting system involvement or urinary extravasation. Grade IV refers to laceration extending through the cortex to medulla and collecting system or main arterial or venous injury with contained hematoma. Grade V refers to a shattered kidney or hilum avulsion with devascularization. The AAST-OIS has been shown to predict the need for intervention [48, 49] with higher-grade injury more likely to require operation, ureteral stents or interventional angiography with embolization or vascular stenting. There are limitations of the AAST-OIS with regard to BRI. Improvements in CT imaging have allowed detection of previously undiagnosed renal injury and nonoperative management of many high-grade injuries, which would have undergone operative intervention in the past—leading some to suggest revision of the AAST-OIS to reflect current practice [51]. These suggestions particularly relate to segmental renal vascular injury or the “shattered” kidney, both grade IV in the proposed reclassification. Blunt segmental vascular injuries have been proposed to be considered a grade IV injury as they are associated with significantly lower operative intervention rates than previously reported [52]. A recent study proposed to modify the AAST-OIS for grade IV into “high-risk” or “low-risk” injuries. High-risk criteria would include extravascular contrast extravasation, a medial laceration or a perirenal hematoma rim distance of greater than 3.5 cm [53]. Patients with grade IV injuries, and at least two of the previous criteria, were shown to be 25 times more likely to need intervention for hemodynamic instability than in patients without those findings [54]. Recently, it has been suggested that hemodynamically stable patients with grade III or higher BRI and findings on CT of contrast extravasation or extensive hematomas benefit from transarterial embolization [55] as well as those with discontinuity of Gerota’s fascia [56]. Continued investigations such as these will continue to validate the AAST-OIS as well as suggest the need to modify the scoring system further to reflect imaging findings associated with differing outcomes. Furthermore, these changes can be used to adjust treatment recommendations based upon imaging for evolving interventions other than operative management.
Grading of BRI—AAST‑OIS
Treatment of BRI: nonoperative, interventional, and surgical therapies
The AAST-OIS details five grades (I–V) of traumatic renal injury and has been shown to predict morbidity and
Nonoperative treatment of BRIs has become the standard in most cases of BRI [13–18]. A recent consensus
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statement proposed only three absolute indications for operative intervention: life-threatening hemorrhage, renal pedicle avulsion (grade V) and an expanding/pulsatile/ non-contained retroperitoneal hematoma [29]. Nonoperative management relies on experienced surgeons who have available modern radiographic techniques and welltrained ICUs. The ultimate goal of nonoperative treatment should be to prevent exsanguination, preserve renal function, lower morbidity and possibly decreasing length of stay [18]. One of the largest and most closely studied cohorts of renal injuries comes from University of California, San Francisco (UCSF) [50]. Overall, average operative rates over 20 years were as follows: 76 % grade III, 78 % grade IV and 93 % grade V. BRI in their series showed overall operative rate of 63 % [50]. The UCSF experience is comprehensive and comparisons of this cohort to appropriately matched series from other institutions have shown a twofold to fourfold lower operative rates as nonoperative management has become more widely applied [18] (Fig. 1). Over these 20 years, however, CT has improved and surgeons have gained more experience with the nonoperative management of the kidney as well as other solid organs. A recently published series from Australia showed successful observation of all grade I and II injuries with
a 94.9, 90.7 and 35.1 % conservative success rates in grades III, IV and V BRI, respectively [57]. An additional series showed a more than doubling of the complication rate (3.3–7.1 %) when minor or moderate renal injuries underwent operative exploration compared to no exploration [58]. The overwhelming majority of contemporary literature supports selective trials of conservative management with good success, including high-grade renal injury in the stable patient. Increasing use of angiography and embolization has become essential in the management schema (Fig. 2). The management of renal injuries in the hemodynamically normal patient where CT demonstrates vascular injury characterized by contained extravasation or pseudo-anuerysms is considered the most appropriate for interventional adjuncts to nonoperative management [29]. A review of over 500 patients in the US National Trauma Data Bank (NTDB) with blunt renal artery injury showed operative intervention in only 27 % of patients, with the majority (67 %) of these undergoing early nephrectomies [59]. An investigation of the NTDB showed the use of diagnostic angiography and angioembolization resulted in eliminating the need for nephrectomy in 78 and 83 % of grade IV and grade V, respectively; however, most required a second intervention (most commonly repeat angiography)
Fig. 1 Algorithm for the conservative management of renal parenchymal injuries. SBP systolic blood pressure, O.R. operating room (from [18])
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Management of blunt renal injury…
Fig. 2 Algorithm for the workup of renal vascular injury and blunt renal injury (from [29])
[60]. The use of angiography is not without fail. A series from a leading US trauma center showed a failure rate of angioembolization of 27.2 % and those who failed angiography regardless of embolization required significantly more blood transfusion [61]. Angiography/angioembolization does appear to show promise in treating hemodynamically stable patients with high-grade renal injuries. However, the majority of the investigations are retrospective in nature, and the overall rarity of this cohort limits investigation. Continued reviews and prospective studies are underway and will hopefully determine which specific injuries and patients that will benefit the most from angiography.
Renal salvage and avoidance of long-term complications have been and remain main goals of conservative treatment. All renal trauma patients are at 64 % risk of nephrectomy when renal injuries are explored, regardless of intent of exploration [24]. Bleeding is often exacerbated by exploration making renal preservation less likely once exploration is undertaken. This underscores the importance of advanced decision-making at the time of laparotomy for blunt traumatic injury. Exploration of zone 2 hematomas and specifically the kidney and Gerota’s space should only be performed in the setting of signs of ongoing hemorrhage. Avoiding exploration of BRI, unless necessary, is a strategy that is more likely to preserve the kidney and its function.
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Pediatrics and geriatrics As described in detail earlier, nonoperative management appears to be safe and effective in the adult trauma literature. Evaluation of the pediatric trauma literature has echoed adult literature in regard to nonoperative management of other solid organ injuries (liver, spleen) and appears to be the same with regard to renal injury [26, 62]. Geriatric trauma patients have been shown to have similar rates of BRI, and rates of angiography, nephrectomy and nonoperative success were similar to non-geriatric patients. However, geriatric trauma patients did have significantly longer ICU stays, more hospital complications and higher mortality [63]. These specific populations appear to have similar outcomes with nonoperative management of BRI to the adult trauma population. However, the frailty of geriatric patients makes it even more important to define specific injury complexes that are most likely to fail nonoperative or interventional therapies to prevent further complications.
Adoption of policy and guidelines The implementation and adoption of center-wide and trauma system-wide policies and/or guidelines for nonoperative management have been shown to decrease operative rates without increases in complications [15]. The importance of guidelines or a “standardization” of care is demonstrated in a survey of practice patterns between urologists and primary trauma surgeons in regard to renal trauma. This survey demonstrated significant differences between practices of urologist and trauma surgeons in operative technique, methods to achieve vascular control, use of angiography and use of ureteral stenting [64]. Two studies on adoption of nonoperative management policy/guideline from Europe showed a twofold to sixfold decrease in operative rates [15, 65]. A prospective registry after the adoption of a nonoperative protocol at a children’s hospital demonstrated a successful 97 % nonoperative rate [26]. The growing body of literature on the success of nonoperative management of BRIs suggests that outcomes will improve from adoption of management guidelines based upon standardized and nuanced severity scoring in the context of the clinical scenario.
Conclusion The evaluation and management of BRI has evolved over the past decades. Increased use and availability of sensitive CT imaging, emerging adjunctive therapies such as interventional angiography, and improved ICU care have led to the acceptance of nonoperative management in BRI. Contemporary recommendations for the management of BRI
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shows that nonoperative management is safe and effective in the majority of low-grade renal injuries, and with appropriate use of techniques such as angioembolization, highergrade injuries are more often successfully treated nonoperatively. Most of the recommendations discussed have evolved largely from retrospective reviews or single-institution reviews, and although great strides in management have been made, there exists areas where more study is needed. Areas of continued investigation into the care of BRIs in the future will likely help to continue to validate and refine the AAST-OIS, to better determine treatment in specific populations (i.e., pediatrics/geriatrics), to better define the best use of interventional angiography and to better define appropriate nonoperative patients with high-grade renal injuries, as well as determining appropriate follow-up. Conflict of interest Benjamin Kautza, Brian Zuckerbraun and Andrew B. Peitzman declare that they have no conflict of interest. Compliance with ethical requirements This work is in compliance with ethical requirements. Benjamin Kautza, Brian Zuckerbraun and Andrew B. Peitzman declare that this is a review article that includes no studies on humans or animals.
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REVIEW ARTICLE
“Management of blunt renal injury: what is new?” B. Kautza1 · B. Zuckerbraun1 · A. B. Peitzman1
Received: 29 October 2014 / Accepted: 11 March 2015 © Springer-Verlag Berlin Heidelberg 2015
Abstract The diagnosis, workup and management of blunt renal injury have evolved greatly over the past decades. Evaluation and management of blunt renal injury echoes the increasing success of nonoperative management in other blunt abdominal solid organ injury, such as liver and spleen. Decision-making difficulties still remain regarding the optimal imaging, grading and degree of interventional or operative exploration used. Increasingly, initial nonoperative management has gained acceptance and appears to be applicable even high-grade injuries. Emerging techniques in highly sensitive imaging as well as interventional angiography have allowed safe nonoperative management in the appropriate patient. This review will focus on the contemporary workup and management of blunt renal injury while focusing on some of the emerging literatures in regard to refined imaging and grading of injuries as well as techniques to increase the success of nonoperative management. Keywords Trauma · Blunt · Renal injury · Nonoperative · Kidney
Introduction Renal injury is relatively uncommon and may be difficult to diagnose, and many aspects of treatment remain controversial. Renal injuries are seen in 1–5 % of all trauma patients, the great majority from blunt mechanisms (~90 %) [1–3]. Recent series in Ireland and the UK demonstrated incidences of 10.25
* A. B. Peitzman [email protected] 1
Department of Surgery, University of Pittsburgh, F1200 PUH 200 Lothrop St, Pittsburgh, PA 15213, USA
and 50 cases per million person-years, respectively, with blunt injuries again being the predominant mechanism [4, 5]. Since the first reports of renal trauma in the 1800s [6], the literature produced sporadic case reports or patient series. The paucity of early literature and accurate imaging tools made diagnosis and treatment of blunt renal injuries (BRI) difficult. Recommendations in earlier literature were divided on whether operative or nonoperative management was preferable for the non-exsanguinating patient [7–12]. However, based upon successful outcomes of nonoperative approaches over the past half century [13, 14], nonoperative management of BRI has become the standard in the majority of BRI [15–18]. The trend toward nonoperative management mirrors that of other solid organ injuries, including liver and spleen [19, 20]. Introduction of computed tomography (CT) and a uniform grading system that allowed accurate comparison of renal injuries have revolutionized diagnosis and management of BRI. Furthermore, the promulgation of angiography and endovascular interventions has added a new dimension to treatment of BRI. The American Association for the Surgery of Trauma Organ Injury Scale (AAST-OIS) is applicable across trauma centers and has greatly enhanced clinical research [21–24] (Table 1). Additionally, the adoption of protocols and guidelines across trauma systems has allowed more standardized care and better outcomes [25, 26]. This review will highlight some of the evolving management strategies and continued unanswered controversies in the management of BRI. Our literature search included PubMed, Cochrane and Google Scholar search engines.
Initial workup and evaluation of BRI The initial management of trauma patients injured via blunt force mechanisms should focus on primary life-threatening
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B. Kautza et al. Table 1 Kidney injury scale Gradea
Type of injury
Description of injury
I
Contusion Hematoma Hematoma Laceration Laceration Laceration Vascular
Microscopic or gross hematuria, urologic studies normal Subcapsular, non expanding without parenchymal laceration Nonexpanding perirenal hematoma confirmed to renal retroperitoneum 1.0 cm parenchymal depth of renal cortex without collecting system rupture or urinary extravasation Parenchymal laceration extending through renal cortex, medulla, and collecting system Main renal artery or vein injury with contained hemorrhage
Laceration
Completely shattered kidney
Vascular
Avulsion of renal hilum which devascularizes kidney
II III IV V a
Advance one grade for bilateral injuries up to grade III
injuries with additional advanced imaging and procedures done only when medically appropriate. Patients with hemodynamic instability and signs of exsanguination require prompt operative intervention. In hemodynamically normal patients and those who respond appropriately to resuscitation, advanced imaging will allow identification and evaluation of other injuries. CT has improved the identification of BRI, and of all advances in trauma care, the diagnosis and staging of BRI by CT may have the greatest impact to guide the subsequent management. Anatomy and mechanism The kidney’s anatomic location, lying high in the retroperitoneum with the renal pedicle and PUJ the only major attachment points, makes them relatively well protected. Given the well-protected location, only major forces applied result in significant renal injury, which also accounts for the high incidence of other intra-abdominal injuries in association with BRI [27, 28]. BRI is typically due to forces causing either a direct impact, with motor vehicle accidents comprising the vast majority, or indirect damage that causes sudden displacement of the kidney (e.g., fall from height) [1]. The majority of renal injuries are minor with 90 % of renal injuries comprised of injury to the parenchyma or segmental vessels [29]. More severe injuries including major lacerations, involving hilar vessels, are seen in up to 25 % of bluntly injured patients [30– 33]. Often these injuries are associated with mechanisms involving significant deceleration forces [28]. Initial evaluation and imaging Initial evaluation of the bluntly injured patient must take into account the overall condition of the patient in the context of the hospital setting and resources. The hemodynamic status of the patient is the most important determinant in early management of the patient with BRI.
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Hemodynamic stability allows further investigation during the initial assessment of the blunt trauma victim. Concern for renal trauma can be suspected from signs on the physical examination such as rib fractures or flank ecchymosis [34]. The use of the urinalysis to detect hematuria is important in assessment of a patient with suspected BRI [29]. Hematuria is commonly transient, and collection of the urinalysis on the first void is important [35]. In the patient with suspected BRI, determination between microscopic and gross hematuria does have predictive value in determining the presence of a major renal injury [33]. It has been shown that hematuria can be seen in up 94 % of renal trauma cases, although this common sign does not predict the severity of the injury [36, 37]. Urinalysis for hematuria is done either as microscopic or dipstick [38]. Hematuria can also be associated with injury anywhere in the urinary system including the ureter, bladder and urethra. The presence of hematuria of any degree, combined with highenergy mechanism and concerning physical examination, should raise the possibility of BRI and warrants imaging. Today, advanced imaging of stable patients suspected of having BRI is largely by CT. A group of international authors stated in a consensus paper that radiographic imaging of renal trauma has four main objectives: (1) accurately stage the injury, (2) identify preexisting renal pathology, (3) document the function/presence of the uninjured kidney and (4) identify injuries to other intra-abdominal organs [29]. Contemporary staging is through the application of AAST-OIS to findings on CT. Historically, intravenous urography and renal angiography were the main modalities used in staging BRIs [29, 39]. However, these have been replaced by CT based upon the ease and availability of obtaining CT, the high sensitivity of CT for detecting BRI and of course the ability of CT to detect other injuries. CT with intravenous contrast administration reliably reveals vascular injury, lacerations, urinary extravasation as well as hematomas, making this modality
Management of blunt renal injury…
ideal for grading BRIs [32, 40]. Initial CT arteriovenous phase images allow determination of arterial/vascular injury; however, determination of collecting system injury requires delayed imaging. Contemporary CT imaging protocols for suspected BRI typically consist of initial imaging with contrast administration. Although the initial imaging does not reliably determine whether there is injury to the collecting system, the presence of a more substantial injury should prompt obtaining delayed images 10–20 min after contrast injection to evaluate for collections or extravasation of the contrast consistent with injury to the collecting system [41]. Recently, the use of ultrasound (US) to initially identify BRI has been more widely used. US has the benefit of being noninvasive and can be rapidly done when available. In experienced hands, the use of US may provide vital information regarding the presence of BRI [42]; however, limitations do exist. US does not reliably detect major vascular injury and has more user variability and decreased sensitivity compared to CT [43]. New US techniques including real-time 3D-enhanced imaging are being developed and may show promise in the future [44]. US has been shown to be useful in follow-up imaging, particularly in the diagnosis of post-trauma fluid collections and hydronephrosis. Follow‑up imaging The increase in nonoperative management of BRI has led to the question of whether routine use of follow-up imaging is beneficial. In theory, routine follow-up imaging would allow identification and treatment of complications prior to any clinical deterioration. It has been recommended that routine follow-up radiographic studies be done within 48–96 h to identify progression or complications that may arise [45]. In a recent study, routine imaging changed treatment decisions in less than 1 % of patients, but repeat imaging obtained on a clinical indication altered treatment in 20 % [46]. Another investigation showed that grade III or lower BRI did not develop complications, and the 11.1 % of BRI who did develop complications were all symptomatic, suggesting that selective follow-up imaging based on laboratory and clinical signs is safe [47]. A recent investigation suggested benefit for routine follow-up imaging for all grade IV and V injuries diagnosed on initial CT [48]. Although there is no general consensus regarding followup imaging, radiographic studies should be obtained when clinical (fever, flank pain/mass, bleeding, etc.) or laboratory values indicate concern for complication [29].
mortality in BRI [24] (Table 1). Grade I refers to contusion or nonexpanding subcapsular hematoma without parenchymal laceration. Grade II is a nonexpanding perirenal hematoma confined to the retroperitoneum or a less than 1 cm cortical laceration without urinary extravasation. Grade III is a greater than 1 cm cortical laceration without collecting system involvement or urinary extravasation. Grade IV refers to laceration extending through the cortex to medulla and collecting system or main arterial or venous injury with contained hematoma. Grade V refers to a shattered kidney or hilum avulsion with devascularization. The AAST-OIS has been shown to predict the need for intervention [48, 49] with higher-grade injury more likely to require operation, ureteral stents or interventional angiography with embolization or vascular stenting. There are limitations of the AAST-OIS with regard to BRI. Improvements in CT imaging have allowed detection of previously undiagnosed renal injury and nonoperative management of many high-grade injuries, which would have undergone operative intervention in the past—leading some to suggest revision of the AAST-OIS to reflect current practice [51]. These suggestions particularly relate to segmental renal vascular injury or the “shattered” kidney, both grade IV in the proposed reclassification. Blunt segmental vascular injuries have been proposed to be considered a grade IV injury as they are associated with significantly lower operative intervention rates than previously reported [52]. A recent study proposed to modify the AAST-OIS for grade IV into “high-risk” or “low-risk” injuries. High-risk criteria would include extravascular contrast extravasation, a medial laceration or a perirenal hematoma rim distance of greater than 3.5 cm [53]. Patients with grade IV injuries, and at least two of the previous criteria, were shown to be 25 times more likely to need intervention for hemodynamic instability than in patients without those findings [54]. Recently, it has been suggested that hemodynamically stable patients with grade III or higher BRI and findings on CT of contrast extravasation or extensive hematomas benefit from transarterial embolization [55] as well as those with discontinuity of Gerota’s fascia [56]. Continued investigations such as these will continue to validate the AAST-OIS as well as suggest the need to modify the scoring system further to reflect imaging findings associated with differing outcomes. Furthermore, these changes can be used to adjust treatment recommendations based upon imaging for evolving interventions other than operative management.
Grading of BRI—AAST‑OIS
Treatment of BRI: nonoperative, interventional, and surgical therapies
The AAST-OIS details five grades (I–V) of traumatic renal injury and has been shown to predict morbidity and
Nonoperative treatment of BRIs has become the standard in most cases of BRI [13–18]. A recent consensus
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statement proposed only three absolute indications for operative intervention: life-threatening hemorrhage, renal pedicle avulsion (grade V) and an expanding/pulsatile/ non-contained retroperitoneal hematoma [29]. Nonoperative management relies on experienced surgeons who have available modern radiographic techniques and welltrained ICUs. The ultimate goal of nonoperative treatment should be to prevent exsanguination, preserve renal function, lower morbidity and possibly decreasing length of stay [18]. One of the largest and most closely studied cohorts of renal injuries comes from University of California, San Francisco (UCSF) [50]. Overall, average operative rates over 20 years were as follows: 76 % grade III, 78 % grade IV and 93 % grade V. BRI in their series showed overall operative rate of 63 % [50]. The UCSF experience is comprehensive and comparisons of this cohort to appropriately matched series from other institutions have shown a twofold to fourfold lower operative rates as nonoperative management has become more widely applied [18] (Fig. 1). Over these 20 years, however, CT has improved and surgeons have gained more experience with the nonoperative management of the kidney as well as other solid organs. A recently published series from Australia showed successful observation of all grade I and II injuries with
a 94.9, 90.7 and 35.1 % conservative success rates in grades III, IV and V BRI, respectively [57]. An additional series showed a more than doubling of the complication rate (3.3–7.1 %) when minor or moderate renal injuries underwent operative exploration compared to no exploration [58]. The overwhelming majority of contemporary literature supports selective trials of conservative management with good success, including high-grade renal injury in the stable patient. Increasing use of angiography and embolization has become essential in the management schema (Fig. 2). The management of renal injuries in the hemodynamically normal patient where CT demonstrates vascular injury characterized by contained extravasation or pseudo-anuerysms is considered the most appropriate for interventional adjuncts to nonoperative management [29]. A review of over 500 patients in the US National Trauma Data Bank (NTDB) with blunt renal artery injury showed operative intervention in only 27 % of patients, with the majority (67 %) of these undergoing early nephrectomies [59]. An investigation of the NTDB showed the use of diagnostic angiography and angioembolization resulted in eliminating the need for nephrectomy in 78 and 83 % of grade IV and grade V, respectively; however, most required a second intervention (most commonly repeat angiography)
Fig. 1 Algorithm for the conservative management of renal parenchymal injuries. SBP systolic blood pressure, O.R. operating room (from [18])
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Management of blunt renal injury…
Fig. 2 Algorithm for the workup of renal vascular injury and blunt renal injury (from [29])
[60]. The use of angiography is not without fail. A series from a leading US trauma center showed a failure rate of angioembolization of 27.2 % and those who failed angiography regardless of embolization required significantly more blood transfusion [61]. Angiography/angioembolization does appear to show promise in treating hemodynamically stable patients with high-grade renal injuries. However, the majority of the investigations are retrospective in nature, and the overall rarity of this cohort limits investigation. Continued reviews and prospective studies are underway and will hopefully determine which specific injuries and patients that will benefit the most from angiography.
Renal salvage and avoidance of long-term complications have been and remain main goals of conservative treatment. All renal trauma patients are at 64 % risk of nephrectomy when renal injuries are explored, regardless of intent of exploration [24]. Bleeding is often exacerbated by exploration making renal preservation less likely once exploration is undertaken. This underscores the importance of advanced decision-making at the time of laparotomy for blunt traumatic injury. Exploration of zone 2 hematomas and specifically the kidney and Gerota’s space should only be performed in the setting of signs of ongoing hemorrhage. Avoiding exploration of BRI, unless necessary, is a strategy that is more likely to preserve the kidney and its function.
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Pediatrics and geriatrics As described in detail earlier, nonoperative management appears to be safe and effective in the adult trauma literature. Evaluation of the pediatric trauma literature has echoed adult literature in regard to nonoperative management of other solid organ injuries (liver, spleen) and appears to be the same with regard to renal injury [26, 62]. Geriatric trauma patients have been shown to have similar rates of BRI, and rates of angiography, nephrectomy and nonoperative success were similar to non-geriatric patients. However, geriatric trauma patients did have significantly longer ICU stays, more hospital complications and higher mortality [63]. These specific populations appear to have similar outcomes with nonoperative management of BRI to the adult trauma population. However, the frailty of geriatric patients makes it even more important to define specific injury complexes that are most likely to fail nonoperative or interventional therapies to prevent further complications.
Adoption of policy and guidelines The implementation and adoption of center-wide and trauma system-wide policies and/or guidelines for nonoperative management have been shown to decrease operative rates without increases in complications [15]. The importance of guidelines or a “standardization” of care is demonstrated in a survey of practice patterns between urologists and primary trauma surgeons in regard to renal trauma. This survey demonstrated significant differences between practices of urologist and trauma surgeons in operative technique, methods to achieve vascular control, use of angiography and use of ureteral stenting [64]. Two studies on adoption of nonoperative management policy/guideline from Europe showed a twofold to sixfold decrease in operative rates [15, 65]. A prospective registry after the adoption of a nonoperative protocol at a children’s hospital demonstrated a successful 97 % nonoperative rate [26]. The growing body of literature on the success of nonoperative management of BRIs suggests that outcomes will improve from adoption of management guidelines based upon standardized and nuanced severity scoring in the context of the clinical scenario.
Conclusion The evaluation and management of BRI has evolved over the past decades. Increased use and availability of sensitive CT imaging, emerging adjunctive therapies such as interventional angiography, and improved ICU care have led to the acceptance of nonoperative management in BRI. Contemporary recommendations for the management of BRI
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shows that nonoperative management is safe and effective in the majority of low-grade renal injuries, and with appropriate use of techniques such as angioembolization, highergrade injuries are more often successfully treated nonoperatively. Most of the recommendations discussed have evolved largely from retrospective reviews or single-institution reviews, and although great strides in management have been made, there exists areas where more study is needed. Areas of continued investigation into the care of BRIs in the future will likely help to continue to validate and refine the AAST-OIS, to better determine treatment in specific populations (i.e., pediatrics/geriatrics), to better define the best use of interventional angiography and to better define appropriate nonoperative patients with high-grade renal injuries, as well as determining appropriate follow-up. Conflict of interest Benjamin Kautza, Brian Zuckerbraun and Andrew B. Peitzman declare that they have no conflict of interest. Compliance with ethical requirements This work is in compliance with ethical requirements. Benjamin Kautza, Brian Zuckerbraun and Andrew B. Peitzman declare that this is a review article that includes no studies on humans or animals.
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