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Interventional Radiology Case Conferences |
1 All authors: Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, 55 Fruit St, White Bldg. 270, Boston, MA 02114.
Received October 19, 2001;
accepted after revision December 6, 2001.
Address correspondence to P. R. Mueller.
Case History
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Laboratory analysis of the patient's blood revealed a WBC count of 27,800/µL, hematocrit of 43.8%, hemoglobin of 14.5 g/dL, and platelets of 236,000/µL. The patient's blood urea nitrogen was 16 mg/dL and creatinine was 1.5 mg/dL. The amylase was 52 U/L and lipase was 3.6 U/dL. The alanine aminotransferase was 57 U/L and the aspartate aminotransferase was 72 U/L. Urinalysis revealed numerous RBC/high-powered field and 10-20 WBC/high-powered field.
CT of the abdomen revealed a fractured right kidney with a large surrounding hematoma, hemorrhage in the perinephric space, and extravasation of contrast material around the right kidney (Fig. 1A).
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Dr. Titton. How does the mechanism of injury to the kidney alter the evaluation of the patient with renal trauma?
Dr. Mueller. Patients who suffer from blunt abdominal trauma account for most renal injuries, either due to direct impact or rapid deceleration [1,2,3,4,5]. Any patient who has sustained blunt abdominal trauma and has either macrohematuria or microhematuria (<5 RBC/high power field) with symptoms of hypotension (systolic blood pressure <90 mm Hg) should be evaluated on CT of the abdomen. Patients who have sustained blunt abdominal trauma with microhematuria without evidence of hypotension do not require renal imaging [6]. Patients who have sustained penetrating renal trauma may present without evidence of any hematuria on urinalysis and should have CT of the abdomen, provided that the patient is hemodynamically stable, regardless of the results of the urinalysis. The degree of hematuria does not correlate with the severity of renal injury, and most patients with renal vascular pedicle injuries present with only microscopic hematuria [4, 6, 7].
Dr. Titton. When a patient has symptoms suggestive of renal trauma, what CT protocol is necessary to optimize evaluation of the patient?
Dr. Gervais. CT is sensitive and accurate for diagnosing the presence and extent of renal trauma and also permits evaluation of the remainder of the abdominal structures for associated injuries and evidence of hemoperitoneum [8]. CT in patients with suspected renal trauma should include unenhanced scans and then scans in the corticomedullary phase and delayed phase after the administration of 100-150 mL of IV contrast material. Unenhanced CT is necessary to detect hyperdense hematomas. After the administration of IV contrast material, scans in the corticomedullary phase can detect renal contusions, lacerations, fractures, renal vascular injuries, and associated intraabdominal injuries. Delayed images of the kidneys (5-20 min after contrast injection) are optimal for showing urinary leakage from the collecting system or ureter [1, 6]. Three-dimensional CT reconstructions can provide additional valuable information, primarily in cases of more severe renal trauma. Images in the coronal and sagittal planes can aid in the evaluation of the viability of renal parenchyma in renal fractures and can further define the extent of injuries to the collecting system in injuries to the renal pelvis or ureter [6, 9].
Dr. Titton. Is there any role for excretory urography in the evaluation of patients with suspected renal trauma?
Dr. Boland. Although the role of excretory urography has diminished, especially since the advent of multidetector CT, a one-shot excretory urography still performs a limited role in patients who have experienced significant renal trauma necessitating emergent surgery and are too unstable for CT. In these patients, 2 mg/kg of body weight of IV contrast material (hypaque sodium 50% [Diatrizoate]; Nycomed, Princeton, NJ) can be administered through an existing IV line 10 min before abdominal radiography is performed [6, 10] either with a portable unit or in the operating room. This examination may provide information regarding the status of the vascular pedicle and the renal pelvis of both the kidney in question and the contralateral kidney. According to a recent study by Santucci and McAninch [6], findings on intraoperative one-shot excretory urography were abnormal in 98% of patients with a suspected major renal injury. An excretory urogram alone cannot be used to determine whether surgical exploration may be necessary after renal trauma due to its overall lack of both sensitivity and specificity for renal injuries. Overall, excretory urography has been shown to be accurate in depicting only 60-85% of renal injuries [4, 5, 11, 12].
Dr. Titton. Is there any role for MR imaging in evaluation of patients with suspected renal trauma?
Dr. Mueller. Whereas MR imaging is not always available as an emergency procedure and requires longer imaging times, MR imaging has been shown to be useful in an adjunctive role in patients with renal trauma and equivocal CT findings. MR imaging has been shown to more accurately characterize intrarenal versus perirenal hematoma and, in some cases, may more clearly reveal noviable fragments in cases of renal fracture because of its multiplanar capabilities [2, 13]. MR imaging may also be used in evaluating stable pregnant patients, patients with renal insufficiency, and patients with iodine allergy who have sustained suspected renal trauma. In general, MR imaging does not play a prominent role in imaging of the patient with renal trauma at this time, because of the accuracy and availability of CT scanning.
Dr. Titton. Are there any patients who are at an increased risk of sustaining renal trauma?
Dr. Gervais. The radiologist should have a high index of suspicion for underlying renal disease in any patient who has renal trauma. In a retrospective study by Schmidlin et al. [11] of patients who sustained a renal injury, 19% had a preexisting renal abnormality. Patients with congenital genitourinary anomalies such as horeshoe kidneys, ectopic kidneys, polycystic kidneys, and congenital ureteropelvic junction obstruction are at an increased risk of sustaining injuries after abdominal trauma. Patients with chronic hydronephrosis, renal infection, simple renal cysts, and renal cell cancers are also at increased risk of sustaining renal trauma [1, 2]. Patients with preexisting pathologic kidneys may sustain injury from minimal trauma, and the extent of hemorrhage may be disproportionate to what was expected on the basis of the mechanism of injury [11, 12].
Dr. Titton. What are some common injuries associated with renal trauma?
Dr. Boland. Obviously patients who have blunt or penetrating abdominal trauma are at risk of sustaining multiorgan injuries. Overall, the degree of the renal injury correlates with the degree of associated intraperitoneal and retroperitoneal injuries [5]. Injury to the kidney may be associated with trauma to the liver, common bile duct, spleen, pancreas, bowel, mesentery, musculoskeletal system, and chest. Imaging should be extended into the pelvis to evaluate the intrapelvic bowel and mesentery and to evaluate for a possible occult intrapelvic retroperitoneal hemorrhage [14].
Injuries to other organs are seen in approximately 20% of patients with renal trauma due to blunt abdominal trauma, and associated injuries are seen in up to 80% of patients with a penetrating renal injury [2, 4, 15]. In a recent study by Hagiwara et al. [16], the most commonly associated injury with blunt renal trauma was a lung contusion (13%). In this study, the most commonly injured abdominal organ associated with blunt renal trauma was the liver (11%). In a 1999 study by Armenakas et al. [4], the most commonly injured organ associated with penetrating abdominal trauma was also the liver (21%). Other investigators have shown that the presence of a stable additional intraabdominal injury should not influence treatment decisions regarding the treatment of renal trauma [17].
Dr. Titton. How is renal trauma graded radiologically?
Dr. Mueller. It is helpful when categorizing renal injuries radiologically, to keep the clinical and surgical implications of the type of renal injury in mind [8]. For this reason, renal injuries may be classified into three major categories. The first category is minor renal injuries, which account for approximately 80% of renal injuries [18] and include renal contusions and renal lacerations that do not extend into the collecting system. Nearly all minor renal injuries heal spontaneously [2, 19]. The second category is intermediate renal injuries, which account for approximately 15% of renal injuries and include renal lacerations extending into the collecting system and major renal lacerations that do not involve the renal vasculature [2]. The third category is severe renal injuries that require emergent surgery. Severe renal injuries account for approximately 5% of all renal injuries, including renal vascular pedicle avulsions or complete traumatic occlusions, renal pelvic avulsions, and shattered kidneys with devitalized nonenhancing segments of kidneys [2]. The absence of renal enhancement on CT after IV contrast administration is characteristic of a significant renal vascular injury. A cortical rim of enhancement caused by collateral blood flow may sometimes be visualized [12]. A subcapsular or perinephric hematoma may be seen with any degree of renal injury.
Multiple grading systems characterizing renal trauma have been described in the literature. Federle et al. [20] described a system of categorizing renal injury into four groups, with categories 3 and 4 both representing forms of severe renal injury. Nguyen and Carroll [5] described a system of categorizing renal injury into five groups, with categories 1 and 2 representing forms of mild renal injury, categories 3 and 4 representing forms of intermediate injury, and category 5 representing severe renal injury.
Dr. Titton. What are the major considerations in deciding how to treat patients with renal trauma?
Dr. Gervais. Despite the fact that 90-95% of renal injuries can be treated conservatively without surgery [3, 5, 12], the treatment of renal trauma is often debated. The decision is dependent on many factors, including the age of the patient, the mechanism of injury, the hemodynamic status of the patient, serial laboratory assessments, and the extent of injury to the kidneys that is shown on imaging. Some investigators have reported that the size of a perinephric hematoma is indicative of the extent of the underlying renal vascular injury and should influence clinical treatment of patients with renal trauma [6, 21]. Over the past several years, the role of emergent nephrectomy has diminished, with a resultant increase in the rate of renal salvage [17]. Absolute indications for renal exploration include major renal artery injury (avulsion or occlusion) resulting in either non-perfusion of the kidney on CT or hemodynamic instability after resuscitation due to rapidly expanding hemorrhage that may lead to exsanguination [4, 6, 12, 17, 21].
In as many as 20% of patients with acute renal trauma, controversy still exists over initial conservative versus surgical treatment [2, 12]. In these patients, treatment decisions are based on a combination of the patient's clinical, laboratory, and radiologic data. Generally, the trend has been that these patients will undergo conservative treatment for a period of time with close clinical surveillance to minimize unnecessary surgical exploration without increasing morbidity from a missed injury [4, 5]. Ultimately, the condition of these patients may improve without intervention, the patients may eventually have an operation on a nonemergent basis because of devitalized tissue or persistent transfusion requirements, or the patient may be referred to the radiology service for an interventional procedure.
Dr. Titton. What potential complications may be expected in patients with renal trauma?
Dr. Boland. Persistent urinary extravasation is the most common complication of renal trauma that is cited in the literature [3]. These patients are at an increased risk of developing a perinephric abscess and, therefore, are placed on prophylactic antibiotics [3, 17]. Patients who have sustained renal trauma need close interval follow-up both in the period immediately after the traumatic event and over the next several months. A risk of delayed hemorrhage is related to renal vascular injuries such as renal artery pseudoaneurysm formation or renal arteriovenous fistula formation [4, 12, 16] that expands over time and may eventually rupture directly into either the renal parenchyma or the collecting system. These renal vascular injuries may be manifest at any time after the traumatic event. Renovascular hypertension from a compressive subcapsular hematoma (Page kidney) or from a renin-mediated response from a segmental renal infarction or large parenchymal defect may occur as a late complication of renal trauma in up to 33% of patients [3, 15, 19].
Dr. Titton. At the time of this patient's initial diagnosis of renal fracture with a urinoma was an angiogram considered?
Dr. Mueller. Indications for an emergent renal artery arteriogram include persistent hypotension associated with hematuria, evaluation of posttraumatic renal artery occlusion, or a preoperative evaluation [1, 2, 10, 22]. An emergent renal angiogram was not indicated in the treatment of this patient because he remained hemodynamically stable with the administration of IV fluids and the CT scan showed perfusion to the fractured kidney. A nonemergent renal arteriogram may be indicated if the patient has a persistent transfusion requirement or delayed renovascular hypertension after the renal trauma. The patient's hemoglobin did drop from 14.5 to 11.6 g/dL, but this change was thought to be due to hemodilution from the administration of IV fluids and possibly also due to hemoconcentration on admission. The patient's blood was typed and screened, but the patient did not receive a transfusion during the hospitalization. The patient's blood pressure remained stable throughout the course of his hospitalization; therefore, an arteriogram was not indicated.
Dr. Titton. Are there any special considerations when performing renal arteriography for suspected renal trauma?
Dr. Gervais. As little contrast material as possible should be injected before the actual renal arteriogram to minimize opacification of the renal collecting systems and to more clearly delineate subtle angiographic findings [10]. Angiographic findings may include perirenal hematoma, arteriovenous fistula, arteriocaliceal fistula, pseudoaneurysm, evidence of retroperitoneal hematoma, intimal injury, or complete renal artery occlusion. Percutaneous transcatheter embolization with either gelatin sponge (Gelfoam; Upjohn, Kalamazoo, MI) or stainless steel coils is the preferred method of treatment of bleeding traumatic lesions of the kidney to preserve renal function and viable renal parenchyma [10, 22, 23].
Dr. Titton. After several days of conservative treatment, the perirenal urinoma remained largely unchanged in appearance. The patient was referred to the interventional radiology service for treatment of the urinoma with a percutaneous drainage catheter (Figs. 1B and 1C). How was the urinoma drainage performed?
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Dr. Boland. Posttraumatic urinomas, once an indication for surgery and possible nephrectomy, can now be treated radiologically with direct percutaneous drainage [6]. Under CT guidance, a 10-French all-purpose drainage catheter was placed into the right perinephric urinoma using the trocar technique. Some radiologists would advocate placing the drainage catheter using the Seldinger technique. With this technique, initially a 22-gauge needle is placed into the collection. A guidewire is then placed through the needle, and then a series of dilators are exchanged over the guidewire until a drainage catheter is eventually placed into the collection [10]. After the catheter is placed into the urinoma, a culture of the urinoma fluid should be taken, and the patient should be placed on empiric antibiotic therapy to minimize the risk of a perinephric abscess until the culture and sensitivity of the urinoma are known.
Dr. Titton. After placement of the percutaneous urinoma drainage catheter, output decreased daily. Follow-up CT 3 days after the percutaneous urinoma drainage showed an interval decrease in the perinephric fluid collection. How was the patient treated?
Dr. Mueller. The patient was discharged from the hospital 4 days after the placement of the percutaneous urinoma drainage catheter with instructions to flush the catheter three times a day and to monitor urine output from the catheter. He underwent follow-up CT 10 days after discharge. At this time, the perinephric urinoma had almost completely resolved, and the kidney fracture had begun to heal (Fig. 1D).
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The patient then underwent follow-up renal sonography 4 weeks after the initial placement of the drainage catheter, which showed complete resolution of the perirenal urinoma and continued healing of the right kidney fracture (Fig. 1E). The patient was then instructed to return to the interventional radiology service for removal of the drainage catheter, after confirmation that the urinoma cavity had been completely obliterated. The patient was maintained on oral antibiotics until the percutaneous drainage catheter was removed.
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Dr. Titton. If the urinoma had not decreased in size on the 3-day follow-up CT or if the output from the percutaneous drainage catheter had not decreased over the first few days after the placement of the percutaneous drainage catheter, what other interventional options would have been considered?
Dr. Gervais. Persistence of a urinoma for longer than several days despite placement of an optimally positioned percutaneous drainage catheter into the urinoma is indicative of a continuous leak from the collecting system. Placement of an antegrade nephrostomy alone may not adequately divert enough urine to allow a fistula to heal spontaneously [22]. Therefore, in cases of persistent leakage from the collecting system, an antegrade nephrostomy in combination with antegrade ureteral stent placement or placement of a nephroureterostomy catheter is usually warranted [3, 10, 22]. The combination of percutaneous drainage catheters with either antegrade nephrostomies and ureteral stents or with nephroureteral catheters diverts the urine away from the area of urinary leakage and promotes primary healing of the collecting system.
Dr. Titton. If the ureter had been involved in the traumatic injury, what treatment options are available?
Dr. Boland. The optimal treatment of ureteral injuries is controversial [24]. Primary surgical repair of ureteral injuries may be complicated by a perianastomotic leak or stricture or by an anastomotic dehiscence in up to 53% of patients [24]. Many urologists advocate percutaneous nephrostomy with ureteral stenting, which may be performed either retrogradely through the bladder or antegradely through percutaneous nephrostomy [24]. The retrograde approach may be difficult or impossible because of a large area of ureteral transection, an intervening urinoma, or tortuosity of the ureter [10]. Using floppy guidewires and steerable catheters in an antegrade approach, we can often place a stent across the site of a partial ureteral transection or across a complete ureteral disruption. Ureteral stents are usually left in place for 8-12 weeks to allow the ureter to heal [10]. Posttraumatic ureteral strictures may also be treated with percutaneous endoureteral balloon angioplasty using 4- to 10-mm balloons. Immediate patency approaches 90%, but long-term results have been variable [22].
Some complete ureteral transections are not amenable to repair using either the retrograde or antegrade approaches, and in these instances, antegrade percutaneous nephrostomy along with percutaneous urinoma drainage may be combined with delayed open surgical repair of the ureter [24].
Dr. Titton. In conclusion, can you summarize some of the key steps in evaluating and treating patients with suspected renal trauma?
Dr. Mueller. There should always be a high index of suspicion for renal injury in any patient who presents with blunt abdominal trauma with microhematuria or hypotension with microhematuria and in any patient who has sustained penetrating abdominal injury. Patients with underlying renal disease are especially at risk of renal injury. Triphasic CT has been shown to be both sensitive and accurate in characterizing the degree and extent of the patient's renal injury and possible associated injuries. There are adjunctive roles for both excretory urography and MR imaging. Characterization of the nature of the patient's renal trauma can aid clinicians in follow-up of these patients, because the trend over recent years has been toward conservative initial treatment. Interval changes in renal injuries can be monitored using conventional helical CT in combination with three-dimensional CT techniques. Radiologists may offer percutaneous drainage of urinomas, hematomas, or abscesses. In addition, radiologists may provide first-line treatments for ureteral injuries, with diversionary percutaneous nephrostomies with or without antegrade ureteral stenting. Renal arteriography can provide diagnostic information preoperatively and is the first line of treatment available in achieving hemostasis in renal parenchyma hemorrhage. The expanded role of radiology in the last 15 years in both the diagnosis and treatment of renal injuries has led to improved morbidity, fewer nephrectomies, and overall improved outcomes in patient care.
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  R. L. Titton, D. A. Gervais, P. F. Hahn, M. G. Harisinghani, R. S. Arellano, and P. R. Mueller Urine Leaks and Urinomas: Diagnosis and Imaging-guided Intervention RadioGraphics, September 1, 2003; 23(5): 1133 - 1147. [Abstract] [Full Text] [PDF]
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