a 20-year - old boy presented to the emergency department with sudden onset severe left flank pain for a week and no associated vomiting or urinary symptoms .
he had a history of per - rectal bleeding 6 months earlier for which he was evaluated elsewhere .
an ultrasound done elsewhere the previous day was suggestive of a left perinephric mass , hence a contrast enhanced computed tomography ( ct ) of the abdomen was performed .
it revealed an 8  7 cm hyperdense lesion in the perinephric space displacing the kidney anteriorly , with an intensely enhancing lesion adjacent to the hemorrhage , indicating an arterial aneurysm with surrounding hemorrhage [ figure 1 ] .
it revealed multiple small left renal arterial aneurysms with no active bleeding [ figure 2a ] .
it also revealed similar aneurysms in the superior mesenteric and lumbar arteries [ figure 2b ] .
anti - nuclear antibodies , hepatitis b and c serology were negative , and complement levels were normal .
a diagnosis of pan was made and he was started on steroids and mycophenolate mofetil , as well as anti - hypertensive medication .
he was well at 9 months follow - up and ct angiogram showed no beading of the renal vasculature [ figure 3 ] .
computed tomography of the abdomen showing perinephric hematoma ( arrow ) with adjacent intensely enhancing lesion suggestive of an aneurysm ( arrowhead ) abdominal arteriography ( a ) left renal arteriogram showing multiple small aneurysms involving segmental and interlobar branches of renal artery ( arrows ) ( b ) aortogram showing involvement of superior mesenteric and lumbar vasculature ( arrows ) follow - up computed tomography angiogram with no beading of renal vasculature ( arrows )
spontaneous perinephric hemorrhage ( wunderlich syndrome ) is a rare condition with a wide - ranging etiology .
zhang et al . in their meta - analysis reported on 165 such cases . of these ,
101 ( 62.2% ) were secondary to the rupture of renal tumors , with angiomyolipoma being the most common cause .
they reported five cases of bilateral spontaneous hemorrhage and all of these were secondary to pan .
pan is a multi - system necrotizing vasculitis that involves small and medium sized vessels .
the kidneys are affected in 80% cases with hypertension , proteinuria and ultimately renal functional deterioration being the most common manifestations .
it is secondary to the rupture of arterial aneurysms that usually involve the renal artery , and its segmental and interlobar divisions .
nephrectomy is associated with a high mortality rate ( 50% ) in the acute setting .
angiography with selective embolization allows preservation of renal parenchyma and is now the treatment of choice in cases of active bleeding .
a reduction or resolution in aneurysms has been noted following immunosuppressive therapy and is probably due to the decline in inflammation of the vessel wall . per - rectal
identified gastrointestinal manifestations , and the need for a surgical consult as an independent predictor of mortality in pan .
 we report the case of a young man who presented with spontaneous left perinephric hematoma and per - rectal bleeding . 
 evaluation revealed renal and superior mesenteric arterial aneurysms secondary to polyarteritis nodosa ( pan ) . 
 computed tomography and angiographic findings are presented . 
 the aetiology of spontaneous perinephric hemorrhage along with relevant features of pan are discussed . 
CASE REPORT
DISCUSSION