Trauma to the genitourinary (GU) tract is relatively uncommon because of the anatomic location of key GU organs. However, prompt recognition of the signs and symptoms associated with GU trauma will allow the clinician to order appropriate imaging tests and implement therapeutic plans that can save organs and even a person’s life.
Definition (Classifications)
Table 22-1 summarizes the classification of kidney trauma injuries according to severity. This classification correlates with the need for surgical intervention.
| Grade | Type | Description |
|---|---|---|
| I | Contusion | Microscopic or gross hematuria; urologic studies normal |
| Hematoma | Subcapsular and nonexpanding without parenchymal laceration | |
| II | Hematoma | Nonexpanding perirenal hematoma confined to the renal retroperitoneum |
| Laceration | <1 cm parenchymal depth of renal cortex without urinary extravasation | |
| III | Laceration | >1 cm parenchymal depth of renal cortex without collecting system rupture or urinary extravasation |
| IV | Laceration | Parenchymal laceration extending through the renal cortex, medulla, and collecting system |
| Vascular | Main renal artery or vein injury with contained hemorrhage | |
| V | Laceration | Completely shattered kidney |
| Vascular | Avulsion of the renal hilum, devascularizing the kidney |
Epidemiology
Of all the GU organs, the kidneys are the most likely to be injured after a patient experiences trauma. The overall incidence of renal injury as a result of trauma ranges from 1.4% to 3.25%. Sports-related trauma to the kidney is uncommon and is reported to constitute only 15% to 20% of all traumatic renal injuries. Most cases of renal trauma are the result of blunt trauma, specifically relating to motor vehicle accidents and falls. Kidney injuries are particularly common when a patient is subjected to rapid deceleration forces. One analysis showed that of the 23,666 sports-related injuries among high school–age varsity athletes, only 18 kidney injuries were reported, none of which was serious. In an analysis of more than 653,000 trauma cases from the National Trauma Data Bank, 16,585 were identified as trauma from bicycle injuries. Only 2% of the patients in these cases experienced a GU tract injury, with the kidneys being the organ most likely affected (in 75% of cases), followed by the bladder and urethra (in 15% of cases) and the penis and scrotum (in 10% of cases). Sixty percent of the patients with GU injuries had evidence of concomitant fractures of the spine or pelvis, suggesting that isolated GU trauma is uncommon. Compared with renal injuries, testicular injuries in sports occur at a much lower rate. A review of a trauma registry of all cases of renal and testes injuries (1.4% of all injuries) showed that 92% of injuries involved the kidneys and 8% involved the testes. It is estimated that more than half of injuries to the testes occur during sporting events.
Pathobiology/Pathophysiology
The kidneys are located in the retroperitoneal space and are surrounded by visceral fat and the Gerota fascia. The kidneys lie on either side of the spinal column in front of the psoas muscle and medial to the quadratus lumborum muscle. The hepatic flexure of the colon on the right and the spleen and the splenic flexure on the left cover the kidneys anteriorly. Because they are protected by surrounding structures, traumatic injuries to the kidneys occur mainly in association with major forces and are usually associated with injury to other organs.
Injury to the renal parenchyma constitutes the vast majority of cases. Preexisting renal abnormalities such as hydronephrosis, renal cysts, or abnormal renal position increase the likelihood of renal injury during trauma and are reported in 4% to 19% of adults and 12% to 35% of children. These subjects have more severe symptoms and are more likely to require surgical interventions. Vascular injuries of the kidneys occur during deceleration forces and result from damage to the renal pedicle. These cases may present with thrombosis or rupture of vasculature.
Testicular injuries mainly result when blunt trauma forces the tissue against the pelvic bone. Testicular rupture, a scrotal wall hematoma, or an intrascrotal hematocele are possible.
Diagnosis
Obtaining a thorough history is imperative. The initial evaluation of patients should include attention to vital signs recorded on the field and upon arrival at the hospital. The lowest recorded systolic blood pressure may indicate the need for radiologic assessment of subjects for a kidney injury. Careful examination of the abdomen, chest, and back is critical. Patients with evidence of abdominal or flank tenderness or hematoma, rib fractures, and penetrating injuries to the low thorax or flank may have sustained an injury to the kidney and require further assessment. Persons with a testicular injury usually present with swelling, tenderness, and ecchymosis. Rupture of the testis is associated with immediate and severe pain. Scrotal ultrasound is a safe, noninvasive, and valuable tool for detecting testicular rupture, hematocele, hematoma, or traumatic torsion.
Laboratory Findings
Hematuria, either microscopic or gross, is the best indicator of injury to the urinary tract after trauma. Although hematuria is seen in 80% to 90% of cases with kidney trauma, lack of hematuria does not eliminate the possibility of GU injuries, and thus a high degree of clinical suspicion should be maintained if the mechanism of injury suggests renal trauma. In addition, the degree of hematuria may not correlate with the degree of injury. However, in general, the presence of gross hematuria in cases with blunt trauma increases the likelihood of major injury.
Imaging studies specifically focused on the GU tract are required for all patients with rapid deceleration as the mechanism of blunt trauma (e.g., a motor vehicle accident or falls from a height), patients with hypotension (systolic blood pressure <90 mm Hg), adults with gross hematuria, and children with microscopic hematuria. Hemodynamically stable patients with only microscopic hematuria may not require further imaging but should undergo a thorough follow-up evaluation for potentially harmful, delayed effects of trauma.
Imaging
An abdominal computed tomography (CT) scan with use of intravenous contrast is considered the imaging modality of choice in patients with trauma to the GU tract. In one series, the most common findings on CT were perirenal hematoma (29.4%), intrarenal hematoma (24.7%), and parenchymal disruption (17.6%). Measurement of serum electrolytes and serum creatinine is useful in deciding the most appropriate diagnostic and treatment plans. Contrast-enhanced CT should be avoided in subjects who have severely reduced renal function, although in emergent situations, imaging with contrast may be unavoidable.
Differential Diagnosis
Exercise-induced hematuria is a relatively common and benign finding among athletes. The incidence ranges between 50% and 80%, with the highest incidence reported among swimmers, track athletes, and lacrosse players. Obtaining a thorough medication history is critical. Among medications commonly used by athletes, nonsteroidal inflammatory drugs (NSAIDs) are commonly associated with microscopic hematuria. In one study, more than half of athletes with idiopathic hematuria regularly used NSAIDs. Preexisting kidney diseases such as glomerular or cystic diseases may be the source of microscopic hematuria and need to be differentiated from trauma-induced hematuria. The finding of significant amounts of proteinuria may suggest a preexisting glomerular lesion.
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