Teaching Case

A 23-year-old male presented with chest pain to the emergency department after a motor vehicle accident. Vital signs showed tachycardia and hypotension. On examination, pale, diaphoretic, abdomen with mild tenderness in epigastrium, no guarding. Focused assessment with sonography with trauma (FAST) showed a small amount of fluid over the left lobe of the liver, and the right kidney appearance was not clear.

Initial intravenous contrast CT of the abdomen and pelvis showed a non-enhancing right kidney with renal artery avulsion and evidence of small contrast extravasation (Figure 1). Also, significant retroperitoneal haematoma was causing substantial anterior displacement of the right kidney (Figure 1). Additionally, liver injury with perihepatic and retroperitoneal haemorrhage was present (Figure 1). Angiography was indicated for suspicion of active bleeding. On the same day, angiography was performed, showing a complete transection of the right renal artery with a very short right renal artery stump; no extravasation was present, and embolisation was not required (Figure 2). The patient remained haemodynamically stable throughout the procedure.

Follow-up after 4 days with contrast CT of abdomen and pelvis showed persistent lack of perfusion of right kidney with resolving right retroperitoneal haematoma. The liver showed heterogeneous enhancement, and haematoma in the right lobe, but no active bleeding. A small medial splenic laceration with left subphrenic and perisplenic haematoma was also visualised (Figure 3). He was followed by urology with no need for acute surgical intervention; management was conservative, and he was discharged after 12 days with a urology follow-up.

Background

Traumatic renal injury is graded on a scale of I–V by the American Association for the Surgery of Trauma (AAST) based on CT imaging criteria [1]. According to the AAST, Grade V renal injury is classified when there is a devascularised kidney with active bleeding, shattered kidney, kidney infarction due to vessel thrombosis without active bleeding, avulsion of renal hilum, or laceration of the main renal artery or vein [1,2]. Blunt renal trauma occurs in 1–5% of trauma cases, and only 5% of these lesions will affect the renal vasculature [3]. High-energy accidents will cause rapid deceleration, which is the most likely cause of renal artery avulsion [3]. The pathophysiologic mechanism after a renal artery avulsion will vary between patients based on chronic comorbidities, use of anticoagulant or antiplatelet drugs, haemodynamic status, and concomitant lesions. A well-known mechanism is when the proximal renal artery undergoes wall vasospasm and thrombosis, preventing further bleeding. On imaging, this will be shown as an artery stump with no extravasation of contrast.

Imaging Perspective

The imaging of choice recommended by AAST guidelines for blunt renal trauma is a CT of abdomen and pelvis with dual phase (arterial and portal venous) [1]. Also, delayed phase imaging after 5–15 minutes should be considered when an injury to the collecting system is suspected [4]. Normally, the renal collecting system is not well seen with the contrast material; however, a delayed phase has been reported to be useful. Lack of enhancement in the renal parenchyma on CT indicates a non-functioning kidney, as renal artery avulsion will have a complete absence of perfusion. Selective renal angiography and venography will show the specific vascular injury and if there is active bleeding or an artery stump. FAST is the initial evaluation for blunt trauma patients. A positive finding correlates with abdominal injury; however, it is not sensitive to retroperitoneal haemorrhage, and renal injuries can be easily missed [5]. Intravenous urography is not used anymore for patients with renal trauma [5].

Outcome

The mainstay treatment for grade V renal injury is surgical intervention; however, management will vary based on the clinical history and diagnostic imaging results [6,7]. Treatment for renal pedicle avulsion remains a controversial debate. The management in renal artery avulsion can be conservative, endovascular, or surgical [6,8]. The kidney and urogenital trauma of the World Society of Emergency Surgery (WSES) and the American Association for the Surgery of Trauma (AAST) guidelines suggest with high-quality evidence that if a patient is stabilised, the presence of a devascularised kidney is not an indication of surgical intervention in the acute setting [9]. Haemodynamically stable patients with main renal artery dissection typically undergo angioembolisation or percutaneous revascularisation [9]. Successful revascularisation has been reported for up to 12 hours after trauma, the preferred time frame is 4 hours [6,10,11]. This is attributed to ischemic changes observed within the first 2 hours and a poor prognosis in patients undergoing revascularisation, with preservation of long-term kidney function seen in less than 25% of cases [12,13]. In our case, the presence of an arterial stump made angioembolisation unnecessary, and revascularisation was unfeasible due to an ischemic time exceeding 12 hours.

Teaching Points

• CT of abdomen and pelvis with dual phase is the gold standard to evaluate blunt renal lesions. The use of delayed images is helpful when damage to the renal collecting system is suspected.
• Treatment for patients with blunt renal trauma is considered in a case-by-case scenario. Based on imaging results and clinical status, management can be surgical, non-operative, or endovascular.

All patient data have been completely anonymised throughout the entire manuscript and related files.