Lee C. Zhao, MD, MS
Allen F. Morey, MD, FACS
BASICS
DESCRIPTION
• Renal injuries can occur by either blunt or penetrating trauma
– Renal contusions, renal laceration, and renal vascular injury are the general categories
• Renal injury classification: Based on American Association for the Surgery of Trauma (AAST) renal injury grading system (1)
– Grade I: Subcapsular hematoma
– Grade II: Laceration <1 cm deep into cortex, small hematoma with Gerota’s fascia
– Grade III: Laceration >1 cm into medulla, no collecting system injury
– Grade IV: Laceration into collecting system, vascular segmental vein or artery injury, renal pelvis laceration and/or complete ureteral pelvic disruption
– Grade V: Main renal artery or vein injury or thrombosis
– Substratification of grade IV injuries (2)[B]
Grade IVb: Higher risk of intervention (angioembolization or exploration) if 2 or more
Active vascular extravasation
Perinephric hematoma >3.5 cm
Medial/complex laceration
EPIDEMIOLOGY
Incidence
• 1–3% of all traumatic injuries
• Most commonly injured GU organ
Prevalence
Estimated 245,000 cases of traumatic renal injuries per year, world wide
RISK FACTORS
• Blunt trauma
– Rapid deceleration
Motor vehicle
Falls
Direct strike to abdomen or flank (sports injury related, bicycle accident, pedestrian in motor vehicle accident [MVA])
• Penetrating trauma
– Upper abdominal
Stab, gunshot, or industrial injury
• Iatrogenic injury
– Laparoscopic, endourologic, renal biopsy, percutaneous procedures
PATHOPHYSIOLOGY
• Kidneys are well protected in the retroperitoneum
– Deceleration can lead to intimal tearing of renal artery and thrombosis
ASSOCIATED CONDITIONS
• Rib fractures
• Injury to other organ systems
GENERAL PREVENTION
• General trauma preventative measures
– Restraints in motor vehicles
DIAGNOSIS
HISTORY
• Ample trauma history:
– Allergies
– Medications
– Past medical history
– Last meal
– Event
• Contrast allergy, previous renal surgeries, stones, trauma, cancer
PHYSICAL EXAM
• Tachycardia and hypotension suggest major bleeding
• Primary survey
– Flank contusion
– Abdominal tenderness
ALERT
Degree of hematuria does not correlate with degree of injury.
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urinalysis
– Hematuria >90% of renal injuries
– Hematuria absent in 36% renal vasculature injuries
– Hematuria with hypotension predictor for major renal injury
• Basic labs: Hgb, Hct, Cr, electrolytes
Imaging
• Indications for imaging
– Blunt trauma
Hypotension (SBP < 90) and hematuria
Gross hematuria
Clinical indicators of renal injury from mechanism or associated injury
– Penetrating trauma
Any degree of hematuria
• US
– Focused abdominal sonography for trauma (FAST) used in some centers for detection of hemoperitoneum
• CT
– Contrast enhanced is best
– Delayed films to evaluate urine leak and collecting system
– Medial urine extravasation
• IV urography (IVP)
– While mostly replaced by CT scan, single shot intraoperative IVP when pre-op imaging is not available before abdominal exploration in the OR with a film under patient on OR table
Single plain film 10 min after 2 mL/kg of IV contrast (max 150 mL)
Diagnostic Procedures/Surgery
Angiography may be performed if embolization is being considered
DIFFERENTIAL DIAGNOSIS
• Spontaneous hemorrhage in patients with renal mass: Traumatic or atraumatic
– Renal angiomyolipoma
– Renal cell carcinoma
– Wunderlich syndrome: Atraumatic renal hemorrhage
• Injury to other organs
TREATMENT
GENERAL MEASURES
• Supportive care
• Assessment of associated injuries
• Decision for nonoperative or operative management of renal injuries (for operative management see “Surgery/Other Procedures” below)
• Nonoperative management: Blunt trauma
– Hemodynamically stable patients with well-staged renal injury may be managed nonoperatively
– 97% blunt renal injuries can be managed nonoperatively (1)[B]
– Monitor with serial Hct and imaging
– Consider angiography and embolization as alternative to renal exploration
Large perinephric hematoma and extravasation of contrast predictive for need of angiographic embolization (3)[B]
– Isolated renal injuries
Most managed nonoperatively except for grade V pedicle avulsion
Consider placement of ureteral stent for persistent urine extravasation
• Nonoperative management: Penetrating trauma
– 55% of stab wounds and 24% of GSW can be managed nonoperatively
– If laparotomy is required for other reasons explore the retroperitoneum for pulsatile, expanding hematoma
MEDICATION
First Line
• Basic fluid and transfusion management
• Broad-spectrum antibiotics for penetrating injury and blunt trauma with urinary extravasation or large retroperitoneal hematoma
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Indications for operative management
– Absolute: Persistent bleeding, expanding and pulsatile retroperitoneal hematoma
– Relative: Urine extravasation, urinoma, nonviable parenchyma, delayed diagnosis, segmental arterial injury
– Isolated urine extravasation can be managed nonoperatively with expectation of >90% resolution (4)[B]
Stent placement if no resolution after 3–7 days
– Nonviable tissue >20%, then complications are greater
• Renal exploration: Transperitoneal approach
– Early isolation of vessels
– Retroperitoneal exploration for expanding and pulsatile hematoma
• Renal reconstruction
– Debridement of nonviable tissue, closure of collecting system, coverage of parenchymal defect
– For polar injury, consider partial nephrectomy with removal of devitalized tissue
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
Bed rest for nonoperative management
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
Most blunt trauma does not require surgical intervention and prognosis is excellent
COMPLICATIONS
• Urinoma/urinary extravasation
– May require internal stent or external drainage
• Urinary fistula
• Delayed bleeding
• Perinephric abscess
• Sepsis
• Calculus formation
• Hydronephrosis
• Hypertension
– Due to renal vessel injury
– Compression of kidney
– Posttraumatic AV fistula
• Pseudoaneurysm
FOLLOW-UP
Patient Monitoring
• Bed rest for continued hematuria
• Repeat CT scan
• Serial Hct
Patient Resources
• Urology Care Foundation: Kidney (renal) Trauma
http://www.urologyhealth.org/urology/index.cfm?article=61
REFERENCES
1. Buckley JC, McAninch JW. Revision of current American Association for the Surgery of Trauma Renal Injury grading system. J Trauma. 2011;70:35–37.
2. Dugi DD, Morey AF, Gupta A, et al. American Association for the Surgery of Trauma grade 4 renal injury substratification into grades 4a (low risk) and 4b (high risk). J Urol. 2010;183:592–597.
3. Nuss GR, Morey AF, Jenkins AC, et al. Radiographic predictors of need for angiographic embolization after traumatic renal injury. J Trauma. 2009;67:578–582.
4. Alsikafi NF, McAninch JW, Elliott SP, et al. Nonoperative management outcomes of isolated urinary extravasation following renal lacerations due to external trauma. J Urol. 2006;176:2494–2497.
ADDITIONAL READING
• Alsikafi NF, Rosenstein DI. Staging, evaluation, and nonoperative management of renal injuries. Urol Clin N Am. 2006;33:13–19.
• American Association for the Surgery of Trauma (AAST) Injury Scoring Scale. http://www.aast.org/Library/TraumaTools/InjuryScoringScales.aspx. Accessed January 26, 2014.
See Also (Topic, Algorithm, Media)
• Bladder Trauma
• Renal Trauma, Adult Algorithm 
• Renal Trauma, Adult Images 
• Renal Trauma, Pediatric
• Retroperitoneal Hematoma
• Ureter, Trauma
• Wunderlich Syndrome
CODES
ICD9
• 866.00 Injury to kidney without mention of open wound into cavity, unspecified injury
• 866.01 Injury to kidney without mention of open wound into cavity, hematoma without rupture of capsule
• 866.02 Injury to kidney without mention of open wound into cavity, laceration
ICD10
• S37.009A Unspecified injury of unspecified kidney, initial encounter
• S37.019A Minor contusion of unspecified kidney, initial encounter
• S37.039A Laceration of unsp kidney, unspecified degree, init encntr
CLINICAL/SURGICAL PEARLS
• CT with IV contrast is single best study.
• Most blunt renal trauma is managed nonoperatively.
• Angioembolization should be considered for stable patients with isolated renal laceration and renal vascular laceration.
• Renal vascular avulsions should be explored.
• Grade IV renal injuries may be substratified by additional findings of active vascular extravasation, perinephric hematoma, medial/complex laceration.