Renal Trauma

Renal injuries are the most common genitourinary (GU) injuries, occurring in up to 3% of all civilian trauma patients, with more than 90% resulting from blunt mechanisms.^[1] Despite their frequency, the majority are low-grade injuries managed nonoperatively. High-grade renal injuries (AAST grades IV–V) pose the greatest risk for life-threatening hemorrhage and long-term complications including renovascular hypertension and chronic kidney disease. This page summarizes imaging indications, AAST grading, nonoperative management (NOM), angioembolization, operative techniques, and follow-up protocols based on the ACS Best Practices Guidelines for Management of Genitourinary Injuries (August 2025).^[2]

Epidemiology and Mechanism

Renal trauma occurs most often after motor vehicle collisions, falls from height, and direct blows to the flank. Penetrating injuries — particularly gunshot wounds — carry a higher risk of associated injuries to adjacent structures (liver and duodenum on the right; diaphragm, spleen, stomach, pancreas, and colon on the left).^[3] Pediatric patients are disproportionately affected due to underdeveloped cartilaginous ribs and relatively larger kidney-to-body ratio, with renal injuries commonly following pedestrian–motor vehicle crashes and recreational vehicle accidents.^[1]

Indications for Imaging

Plain radiography and ultrasound are not recommended as primary diagnostic tools for suspected renal injury. Contrast-enhanced abdominal/pelvic CT is the gold standard in hemodynamically stable or stabilized patients.^[4]

Obtain CT imaging for suspected renal injury when any of the following are present:^[2]

• Gross hematuria (any mechanism)
• Microhematuria with hypotension, in the absence of indications for emergent laparotomy
• Penetrating injury to the abdomen or flank
• Significant mechanism: fall from height, rapid deceleration, direct flank blow
• Clinical findings of renal trauma: flank ecchymosis, lower rib fractures on chest radiograph

:::note Key Point Microhematuria without hypotension in a patient with no other high-risk features does not mandate renal imaging. This selective approach reduces unnecessary CT radiation exposure. :::

CT Imaging Protocol

Phase	Timing After Contrast	Clinical Role
Portal venous phase	~70 seconds	Essential; parenchymal injury, active bleeding detection
Arterial phase	~20–40 seconds	Optional; improves detection of pseudoaneurysm (PSA) and arteriovenous fistula (AVF)
Delayed (excretory) phase	3–20 min (optimal ~10 min)	Required to detect collecting system injury and urinary extravasation

Delayed-phase imaging should be obtained selectively when: a renal injury is already demonstrated on portal venous phase imaging; mechanism raises concern for renal/ureteral injury; or unexpected perirenal or periureteral fluid is present.^[2] When the patient must leave the scanner before review, delayed images may be acquired up to approximately 60 minutes after the initial contrast injection.^[5]

AAST Organ Injury Scale — Kidney (2018 Revision)

The AAST renal injury scale was updated in 2018 to incorporate CT-based findings including PSA, AVF, and active extravasation beyond Gerota's fascia.^[6]

Grade	Description
I	Subcapsular hematoma without parenchymal laceration; parenchymal contusion
II	Perirenal hematoma confined to Gerota's fascia; parenchymal laceration ≤1 cm depth, no urinary extravasation
III	Parenchymal laceration >1 cm depth without urinary extravasation; active bleeding contained by Gerota's fascia; PSA or AVF arising from the kidney and contained by Gerota's fascia
IV	Parenchymal laceration into the collecting system with urinary extravasation; renal pelvis laceration or ureteropelvic junction (UPJ) disruption; segmental renal vein or artery PSA or AVF; active bleeding extending beyond Gerota's fascia; segmental or complete kidney infarction
V	Shattered kidney; devascularized kidney; main renal artery or vein laceration or avulsion of hilum with active bleeding

:::note Grade IV Substratification AAST grade IV injuries with segmental renal infarction (without active bleeding) carry a significantly lower hemorrhage risk than other grade IV injuries and have been proposed for downgrade to grade III. Revascularization is not warranted for segmental infarction.^[7] :::

Nonoperative Management (NOM)

Eligibility Criteria

All patients with renal injuries (blunt or penetrating, grades I–V) are candidates for NOM when:^[2]

• Hemodynamics are normal on presentation or after initial resuscitation
• No independent indication for operative exploration exists (peritonitis, bowel injury, etc.)

The only absolute contraindication to NOM is persistent hemorrhagic shock directly attributable to a high-grade renal injury.

Liberal opening of Gerota's fascia during exploratory laparotomy dramatically increases nephrectomy rates; NOM, including angioembolization when available, should be pursued aggressively.^[8]

NOM by Injury Grade

Grade	Success Rate	Notes
I–II	~100%	Standard of care; no intervention typically required
III	~95%	Active monitoring required; cortex-to-medulla traverse raises failure risk
IV	~94%	Urine leak may require stenting or nephrostomy; UPJ avulsion is absolute contraindication to NOM
V	~85%	Angioembolization can be successful; hilar avulsion usually requires emergent exploration

NOM Principles

NOM requires a clinical environment capable of serial hemodynamic and laboratory monitoring. Elements include:^[2]

• Bed rest and close hemodynamic monitoring (ICU for higher-grade injuries)
• Serial hematocrit measurement
• Availability of urology and interventional radiology consultation
• Minimum observation period of 48–72 hours for high-grade injuries
• Injury to the renal pelvis or proximal ureter initially managed with NOM but may require expeditious drainage via ureteral stenting or percutaneous nephrostomy within the same admission

Angioembolization (Renal Artery Angiography with Embolization, RAE)

Indications

RAE is appropriate for hemodynamically stable patients or those who respond to resuscitation with any of the following:^[2]

• Active arterial contrast extravasation on CT (arterial or portal venous phase)
• Renal PSA
• Renal AVF
• Persistent gross hematuria
• Large or expanding perirenal hematoma (hematoma rim distance >3.5 cm independently predicts need for bleeding intervention — each additional centimeter from 1.5–≥4 cm increases odds of intervention by ~66%)^[9]

Technical Considerations

• Sub-selective embolization is preferred over main renal artery embolization to preserve renal parenchyma and function
• Primary RAE failure rate: 27%–29%; repeat angioembolization for ongoing bleeding is recommended and carries a ~97% success rate^[10]
• Grade V injuries with complete hilar avulsion most likely require emergent surgical exploration regardless of RAE availability
• Grade V shattered kidney without hilar avulsion can be managed conservatively with RAE as needed
• Hybrid OR suites (combined IR/surgical capability) allow concurrent angioembolization and open exploration in refractory shock

:::note Clinical Pearl A validated nomogram incorporating mechanism, shock, pararenal hematoma presence, hematoma rim distance, and active extravasation predicts need for bleeding control interventions after high-grade renal trauma and can guide RAE vs. observation decisions.^[9] :::

Operative Management

Indications for Exploration

Absolute:

• Hemodynamic instability unresponsive to resuscitation with active renal hemorrhage
• Grade V hilar avulsion
• Expanding, pulsatile, or ruptured Zone II retroperitoneal hematoma

Blunt trauma: A non-expanding Zone II retroperitoneal hematoma found at laparotomy for other injuries should not be explored — it is associated with significantly higher nephrectomy rates. Obtain postoperative CT for characterization.^[2]

Penetrating trauma: Zone II hematomas after penetrating injury may be explored due to increased likelihood of clinically significant renal pelvis, ureteral, or vascular injury.

Preoperative Preparation

• Midline incision from xyphoid to pubis
• Balanced resuscitation (permissive hypotension, limited crystalloid, blood product transfusion)
• Activate massive transfusion protocol when appropriate
• Before exploring the injured kidney: palpate the contralateral kidney. If absent or abnormal (polycystic, atrophic), a single-shot IV pyelogram (2 mg/kg contrast at 10 minutes) confirms contralateral function and guides renal salvage decision-making

Renal Exposure Approaches

Medial approach: Opens retroperitoneum in the midline to isolate renal artery and vein before entering Gerota's fascia. Provides definitive vascular control but may be difficult with large central hematomas distorting hilar anatomy.

Lateral approach: Mobilizes the colon and opens the hematoma directly; kidney is rapidly mobilized with manual hilar compression available. Allows rapid inspection of parenchyma, collecting system, and vasculature.

Operative Repair by Grade

Grade	Operative Approach
I–III	Cautery, topical hemostatic agents, absorbable suture ligation of individual parenchymal vessels; partial nephrectomy if parenchyma cannot be approximated
IV (stable)	Parenchymal bleeding controlled as above; collecting system closed with running absorbable suture (watertight); Gerota's fascia or omental flap for buttress; closed-suction drain left in place
IV (unstable) / V	Nephrectomy; no attempt at renal salvage in hemodynamically unstable patients requiring ongoing resuscitation
IV vascular — segmental vessels	Ligation acceptable without significant functional impact
IV vascular — main renal vein	Primary repair if lumen not narrowed >50%; left renal vein can tolerate greater narrowing due to collateral drainage; right-side compromise → nephrectomy
IV vascular — main renal artery	Primary repair, end-to-end anastomosis, saphenous vein interposition, or hybrid endovascular stenting; outcomes are poor and nephrectomy is common

Follow-Up Imaging

Early Follow-Up (48–72 Hours)

Obtain contrast-enhanced CT with delayed phase within 48–72 hours for:^[2]

• Grades III–V injuries with ongoing blood loss or urine extravasation on initial imaging
• Penetrating destructive firearm injury (grade III or above)
• Symptoms suggesting complications (fever, worsening flank pain, ongoing blood loss)

Routine repeat imaging for asymptomatic, clinically improving patients is not recommended and does not change management.^[11]

Late Follow-Up (Weeks to Months)

Delayed imaging is recommended only for patients who develop:^[2]

• New-onset gross hematuria
• Clinical signs or symptoms of renal trauma complications

All patients with high-grade renal injuries managed nonoperatively should receive routine blood pressure monitoring by their primary care physician, with referral to urology or nephrology if hypertension develops.

Complications

Complication	Notes
Delayed hemorrhage	May present days to weeks post-injury; secondary PSA or AVF; managed with repeat RAE
Urine leak / urinoma	Grade IV collecting system injury; managed with ureteral stenting or percutaneous nephrostomy
Renovascular hypertension	Rare but serious; associated with renal artery injury, large devitalized fragments, or Page kidney phenomenon (circumferential hematoma compressing parenchyma); activates renin-angiotensin system; majority eventually require delayed nephrectomy[12]
Abscess / perinephric infection	Requires percutaneous drainage
Renal insufficiency	Follow renal function in high-grade injuries, especially with contralateral renal disease

:::note Pediatric Considerations In children, hypotension is a late sign of shock and should not be used as the primary trigger for CT imaging; instead, base decisions on hematuria and associated injury patterns. Ultrasound is insufficient for initial renal injury evaluation. NOM is recommended for all grades based on hemodynamic stability. Routine follow-up imaging after discharge is not recommended unless symptoms develop.^[2] :::

:::note Geriatric Considerations Anticoagulation status must be assessed on presentation; reversal should be considered for hemodynamically unstable patients or those with significant blood loss. Do not withhold contrast-enhanced CT based on age alone — evidence linking age alone to contrast-induced nephropathy is inconclusive. Early thromboembolism chemoprophylaxis should be considered for low-grade injuries in stable geriatric patients.^[2] :::

References

1. McGeady JB, Breyer BN. Current epidemiology of genitourinary trauma. Urol Clin North Am. 2013;40(3):323–334. doi:10.1016/j.ucl.2013.04.001.

2. American College of Surgeons Trauma Quality Programs. ACS TQP Best Practices Guidelines: Management of Genitourinary Injuries. Chicago, IL; August 2025. facs.org/cot.

3. Voelzke BB, McAninch JW. Renal gunshot wounds: Clinical management and outcome. J Trauma. 2009;66(3):593–600. doi:10.1097/TA.0b013e318196d0dd.

4. Morey AF, Broghammer JA, Hollowell CMP, McKibben MJ, Souter L. Urotrauma Guideline 2020: AUA Guideline. J Urol. 2021;205(1):30–35. doi:10.1097/JU.0000000000001408.

5. Expert Panel on Major Trauma Imaging, Shyu JY, Khurana B, et al. ACR Appropriateness Criteria® major blunt trauma. J Am Coll Radiol. 2020;17(5S):S160–S174. doi:10.1016/j.jacr.2020.01.024.

6. Kozar RA, Crandall M, Shanmuganathan K, et al. Organ injury scaling 2018 update: Spleen, liver, and kidney. J Trauma Acute Care Surg. 2018;85(6):1119–1122. doi:10.1097/TA.0000000000002058.

7. Keihani S, Gross JA, Joyce RP, et al. The American Association for the Surgery of Trauma Renal Grading System — Should Segmental Kidney Infarction be Classified as a Grade IV Injury? J Urology. 2021;205(1):165–173. doi:10.1097/JU.0000000000001240.

8. Hakam N, Keihani S, Shaw NM, et al. Grade V renal trauma management: Results from the Multi-institutional Genito-Urinary Trauma Study. World J Urol. 2023;41(7):1983–1989. doi:10.1007/s00345-023-04432-w.

9. Keihani S, Rogers DM, Putbrese BE, et al. A nomogram predicting the need for bleeding interventions after high-grade renal trauma: Results from the AAST Multi-institutional Genito-Urinary Trauma Study (MiGUTS). J Trauma Acute Care Surg. 2019;86(5):774–782. doi:10.1097/TA.0000000000002222.

10. Hakam N, Amend GM, Nabavizadeh B, et al. Utility and outcome of angioembolization for high-grade renal trauma management in a large hospital-based trauma registry. J Urol. 2022;207(5):1077–1085. doi:10.1097/JU.0000000000002424.

11. Loftus CJ, Hagedorn JC, Johnsen NV. Does routine repeat imaging for blunt high-grade renal trauma lead to unnecessary interventions? J Trauma Acute Care Surg. 2021;90(1):143–147. doi:10.1097/TA.0000000000002966.

12. Chedid A, Le Coz S, Rossignol P, Bobrie G, Herpin D, Plouin PF. Blunt renal trauma-induced hypertension: Prevalence, presentation, and outcome. Am J Hypertens. 2006;19(5):500–504. doi:10.1016/j.amjhyper.2005.08.015.