LAUSR

A 58-year-old male with comorbid hypertension, asthma and previous renal calculi presented to the emergency department with right flank pain. He denied recent trauma, haematuria, coagulopathy or anticoagulant use. He was haemodynamically stable and abdominal examination revealed only right flank tenderness. Serum investigations demonstrated acute kidney injury (creatinine 153 μmol/L, estimated glomerular filtration rate (eGFR) 43 mL/min/1.73 m), anaemia (haemoglobin (Hb) 114 g/L) and leukocytosis (white cell count 15.1 × 10/L). Abdominal computed tomography (CT) with intravenous contrast demonstrated a right-sided retroperitoneal haematoma (Fig. 1a) of unclear aetiology with no active bleeding. The presumed cause was a ruptured aneurysm from a small sub-cortical angiomyolipoma (8.4 mm) incidentally demonstrated 2 years’ prior during urolithiasis investigation (Fig. 1b). He was observed and subsequently discharged. He re-presented 2 weeks later with contra-lateral left groin pain, frank haematuria and worsened anaemia (Hb 99 g/L), suspicious for ongoing bleeding. No haemodynamic compromise or active bleeding on CT imaging was observed. Following a further period of observation, he was discharged with outpatient follow up. Six weeks after initial presentation, he re-presented with left flank pain and in hypovolaemic shock. Following fluid resuscitation, CT imaging demonstrated a new left kidney sub-capsular haematoma with rupture and perinephric extension (Fig. 2a,b) due to rupture of two distal pseudo-aneurysms (Fig. 2c) which were embolized to achieve haemostasis (Fig. 2d). With spontaneous aneurysm formation, vasculitis was suspected. Vascular medicine review diagnosed polyarteritis nodosa (PAN) made in accordance with the American College of Rheumatology 1990 criteria. Aetiology investigation revealed hepatitis B (core antibody positive) and chronic myelomonocytic leukaemia (CMML), both of which are known to be associated with PAN. Mesenteric angiography revealed stable vasculitis involving the inferior mesenteric artery. His immunosuppressive treatment consisted of steroid (maintenance therapy following loading), cyclophosphamide therapy, as well as lamivudine to prevent recurrence of hepatitis B while immunosuppressed. At 5 months follow up, his serum haemoglobin (126 g/L) and renal function (creatinine 120 μmol/L, eGFR 66 mL/min/1.73 m) have improved to baseline in accordance with progressive reduction of the sub-capsular haematomas (Fig. 3). His baseline hypertension has not worsened to suggest development of a Page kidney. He will require ongoing follow up to monitor for deterioration in renal function or blood pressure control given bilateral renal insult. Spontaneous renal haemorrhage (SRH), or Wunderlich syndrome, is a rare condition characterized by acute onset of non-