Tom Mitchell and James Armitage
Urological trauma may be classified into that affecting the upper urinary tract; the lower urinary tract; and genitoscrotal trauma (Box 5.1).
Box 5.1 Classification of urological trauma.
•Upper urinary tract: renal and ureteric trauma.
•Lower urinary tract: bladder and urethral trauma.
•Genitoscrotal: trauma to penis, scrotum or testes.
Upper urinary tract trauma encompasses trauma to the kidneys and ureters.
Renal trauma occurs in approximately 3% of all trauma cases and 10% of those with abdominal trauma. There is a 3:1 male to female predominance, reflecting overall trends in trauma exposure. Of patients with renal trauma, there is a 40% incidence of other associated intra-abdominal injuries (rising to 80% if the aetiology of the injury was penetrating).
In the developed world, the majority of traumatic ureteric injuries are iatrogenic, from pelvic cancer surgery, gynaecological surgery, abdominal surgery or ureteroscopy.
Blunt trauma accounts for the majority of renal injuries. Two mechanisms of injury may occur: direct trauma may crush the kidney against the ribcage, whereas a rapid deceleration can result in renal vascular or pelviureteric injury. However, in the urban setting, penetrating trauma may account for over 20% of injuries.
The mechanism of trauma helps to determine which patients require urgent radiographic imaging. The degree and cause of any pre-existing renal disease may affect the chosen management (e.g. chronic renal dysfunction, renal calculi) and can predispose to injury (e.g. pelviureteric junction [PUJ] obstruction, renal cysts).
The initial examination should be focused on cardiorespiratory findings as per the Advanced Trauma Life Support® (ATLS®)guidelines. Bruising, penetrating trauma wounds, loin or abdominal masses or fractured ribs may be detectable and may signify an underlying renal injury. Haematuria is not sensitive or specific (13% of patients with penetrating renal injury have no haematuria; conversely, 63% of patients with multi-system trauma may have haematuria, of which only about 12.5% have a confirmed renal injury). All patients suffering high-impact trauma should undergo examination of the perineum and genitalia, and have a digital rectal examination with the findings recorded in the medical records.
Indications for computed tomography (CT) with contrast to characterise renal injury are shown in Box 5.2. Injuries can then be classified according to the American Association for the Surgery of Trauma (Figure 5.1). Whilst this is a useful anatomical grading system, it does not include a description of whether or not there is any active bleeding or pseudoaneurysm present. These are important features that often dictate management.
Box 5.2 Indications for contrast-enhanced CT in the diagnosis of renal trauma.
•Blunt trauma and visible haematuria.
•Blunt trauma, non-visible haematuria and shock (systolic blood pressure <90mmHg).
•Major deceleration injury.
•Visible or non-visible haematuria after penetrating trauma.
•Paediatric trauma in a patient with visible or non-visible haematuria.
•Associated injuries suggesting underlying renal injury.
Figure 5.1 Grades of renal trauma (American Association for the Surgery of Trauma). Advance one grade for bilateral injuries up to grade 3.
Trauma CT imaging protocols vary between hospitals. Unenhanced images will show haematomas or fluid collections although many institutions reduce the overall radiation dose by omitting this phase. An arterial phase is important to evaluate arterial bleeds and pseudoaneurysm formation. A venous phase will give information on renal parenchymal enhancement and show contusions as well as slow venous bleeds. Where a collecting system, ureteric or bladder injury is suspected, a delayed phase, usually at 10 minutes can be added. At this time the intravenous (IV) contrast medium is excreted into the collecting system. Images from a traumatic renal injury with non-contrast, arterial and venous phases are shown in Figure 5.2. Due to hypotension, hypovolaemia or renal injury, excretion may be impaired, so further delayed images may be necessary. Contrast medium can also be injected directly into the urinary bladder via a urethral catheter to perform a direct CT cystogram.
Figure 5.2 Axial computed tomography images with a non-contrast, arterial phase and delayed phase, respectively, at the level of the left renal pelvis (a–c) and level of the lower pole (d–f), showing a high-density perinephric haematoma (thin arrow) and low-density fluid collection (arrow head). The low-density fluid is shown to be a urinoma on the delayed phase images (c and f).
The intra-operative diagnosis of ureteric injuries requires a high index of suspicion. IV indigo carmine or methylene blue, or retrograde studies with fluoroscopy can be used to confirm the diagnosis. Post-operatively, any drain fluid with creatinine levels higher than serum might indicate urinary leakage. Ureteric injuries may be classified according to the American Association for the Surgery of Trauma, as shown in Box 5.3.
Box 5.3 The American Association for the Surgery of Trauma: grades of ureteric trauma.
•Grade I – haematoma.
•Grade 2 – laceration <50% circumference.
•Grade 3 – laceration >50% circumference.
•Grade 4 – complete transection with <2cm of devascularisation.
•Grade 5 – complete transection with >2cm of devascularisation.
•Advance one grade for bilateral injuries up to grade 3.
The immediate management of renal trauma follows the ATLS® guidelines. Subsequently, the over-riding aims are to minimise morbidity and preserve renal function. Conservative management is now commonplace, especially for patients with stable grade 1–4 blunt renal trauma and stable grade 1–3 penetrating renal trauma. Conservative management entails bed rest, prophylactic antibiotics and monitoring of vital signs. Repeat imaging should be considered after 2–4 days. Eighty to ninety percent of urinary extravasation heals spontaneously but sometimes requires placement of a ureteric stent and percutaneous drain. Such management of a collecting system injury is shown in Figure 5.3. Percutaneous nephrostomy and/or antegrade ureteric stent insertion is possible; however, the collecting system is usually not dilated and puncture of the collecting system can be very challenging in an injured kidney.
Figure 5.3 Sagittal and coronal images of the left kidney at the time of renal injury (a and b) showing a grade 4 injury with collecting system rupture, and at 3 months (c and d) showing renal preservation with lower pole scarring following conservative management and ureteric stenting.
Indications for operative or radiological management include life-threatening haemodynamic instability, active bleeding, pseudoaneurysm, grade 5 renal injuries particularly with active bleeding, surgical exploration for associated injuries or an expanding peri-renal haematoma identified during laparotomy.
Endovascular intervention is a minimally invasive option for treating arterial injury following trauma. More often than not, embolisation can be very specific in order to stop bleeding yet preserve renal function, as shown in Figure 5.4. It is also possible in severe injuries to perform complete embolisation of the main renal artery.
Figure 5.4 Coronal computed tomography (a) showing a grade 4 renal injury with a pseudoaneurysm and haematoma. Note multiple renal arteries. Digital subtraction angiograms (b) showing the interpolar artery supplying the pseudoaneurysm and (c) following super-selective embolisation.
The main approach to operative management is via a midline, transperitoneal approach with control of the renal pedicle prior to opening the retroperitoneum. Any devitalised tissue should be debrided and if feasible, a partial nephrectomy may be performed, although the priority is to save life over preventing renal loss. If there has been damage to the collecting system this should be repaired.
Longer-term follow-up of renal trauma includes a renogram (DMSA) and ultrasound scan, usually after 3 months, to document functional and structural outcome. Serum creatinine should be checked and blood pressure monitored for the detection of possible renovascular hypertension.
Management of ureteric trauma depends upon the timing of diagnosis, the anatomical location and the grade of the injury (Box 5.3). The first principle is to establish low-pressure urinary drainage either by ureteric stenting or nephrostomy placement. The optimal timing of any definitive surgical repair is not clear but should generally be considered either early (within 1 week of injury), or delayed (after 3 months) once inflammation and oedema have resolved. Surgical approaches commonly include primary repair (ureteroureterostomy), reimplantation to either the renal pelvis (rarely a lower pole calyx) or to the bladder (psoas hitch or Boari flap). Other surgical approaches include reimplantation of the affected ureter into the contralateral ureter (transureteroureterostomy), autotransplantation of the entire kidney and ureter, an ileal interposition graft that can replace part of, or the whole ureter, or performing a nephrectomy.
A successful ureteric repair relies upon a tension-free anastomosis of viable tissue. Spatulation of the distal and proximal ureteric ends is recommended to reduce the chance of stricture formation. An internal stent and external non-suction drain are placed, and if possible the repair covered with peritoneum or omentum.
•Renal trauma accounts for 3% of all trauma cases.
•Most patients with renal trauma will have visible or non-visible haematuria, but not all.
•Conservative management is appropriate for most blunt grade 1–4 trauma (and grade 1–3 penetrating trauma).
•Operative or interventional radiological management is needed for life-threatening haemodynamic instability, active bleeding, pseudoaneurysm, grade 5 renal injuries particularly with active bleeding, and expanding peri-renal haematomas identified during laparotomy.
•Ureteric trauma is commonly iatrogenic, caused by pelvic or abdominal surgery, or during ureteroscopy.
•Repair of ureteric trauma is dependent on the location and length of the defect, and requires the repair to be tension-free, and to try to preserve healthy, well-perfused tissue.