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Paper text:
renal artery stenosis is a cause of secondary hypertension which can be cured by surgical or radiological intervention such as percutaneous transluminal renal artery stent placement1 ) .
hyperperfusion syndrome is a rare complication following revascularization of the internal carotid artery2 ) . in case of renal artery stenosis
subcapsular hematoma of the kidney , an accumulation of blood between the renal parenchymal surface and the surrounding fibrous capsule , occurs most often secondary to post - traumatic bleeding .
although the incidence of subcapsular hematoma following percutaneous transluminal stent placement has been considered rare , we experienced a case whose radiological signs and clinical symptoms were consistent with subcapsular hematoma of the kidney following the procedure .
this report is presented to propose the possibility of such a complication associated with the procedure , especially under the state of chronic hypoxia .
a 59-year - old man was admitted for a follow - up evaluation and treatment of his renal artery stenosis , which was diagnosed one year prior to his admission . at that time , narrowing of the proximal portion of the right renal artery was discovered by abdominal magnetic resonance imaging .
his hypertension was classified as the seventh report of the joint national committee on the prevention , detection , evaluation , and treatment of high blood pressure ( jnc 7 ) stage 2 .
he had been medicated with the following antihypertensive drugs : nifedipine , 90 mg ; carvediol , 25 mg ; eprosartan , 600 mg ; doxazocin , 8 mg ; hydralazine , 25 mg ; metolazone , 5 mg ; and aspirin , 100 mg . on admission
an abdominal bruit was heard at his epigastric area and the rest of the findings were unremarkable .
the vital signs on admission were as follows : blood pressure , 150/90 mmhg with medication ; temperature , 36.5 ; pulse , 55 bpm ; and respiratory rate , 23/min .
the laboratory findings on admission are unremarkable except for a 2 positive proteinuria on his urinalysis .
arteriography of abdominal aorta showed more than 90% narrowing of his right renal artery at the ostium ( fig .
pressure gradient of the aorta and both renal arteries were as follows : aorta , 179/80 mmhg ; left renal artery , 153/76 mmhg ; and right renal artery , 35/23 mmhg .
an 8 fr guiding catheter was placed at the distal portion of the right renal artery , and a 5 mm14 mm corinthian stent ( cordis endovascular / johnson & johnson , miami , fl , usa ) was placed at the stenotic area of the right renal artery ( fig .
pressure gradient of the aorta and right renal artery were reexamined ; they were 205/95 mmhg and 192/90 mmhg , respectively .
approximately 2 hours after the procedure , the patient complained of severe pain in his right flank with diaphoresis .
an emergency contrast enhanced computed tomography ( ct ) revealed a large right perirenal subcapsular hematoma and compression of that kidney ( fig .
three hours after the stenting procedure , his hemoglobin level dropped to 7.5 g / dl .
three units of blood were transfused and an angiotensin receptor blocker ( eprosartan 600 mg ) for hypertension was prescribed .
ten days later , a follow - up contrast enhanced ct examination revealed that the compression of renal parenchyma was much improved .
his blood pressure fell to 120/75 mmhg without medication . following the treatment , the patient 's general condition became stable and he was discharged without antihypertensive medication .
aging and coexisting atherosclerosis are also known to have significant effects on the prevalence of renovascular hypertension in this population3 ) .
percutaneous transluminal renal artery stent placement , when performed by experienced hands , has been regarded as a safe and effective procedure4 ) .
the technical success rate ranges from 96% to 100% , with complications occurring in 13% of the cases5 ) .
mortality related to this procedure is extremely rare , ranging 0 - 0.5% immediately following the procedure and 1% in the 30-day follow up period1 , 3 , 5 ) .
axelrod et al.6 ) have reported a case of guide wire perforation that led to a fatal perirenal hemorrhage from the transcortical collaterals after renal artery stent placement .
since there was no evidence of injury provoked by the guide wire in this case , the cause for the subcapsular hematoma was postulated to be secondary to the reperfusion injury , such as seen in increased intrarenal pressure .
the pressure gradient of right renal artery before and after stenting were 35/23 mmhg and 192/90 mmhg , respectively .
the intrarenal pressure was markedly increased after renal artery stent placement . in case of cerebral hyperperfusion syndrome ,
the risk factors are considered as long standing high grade carotid artery stenosis , loss of cerebral reserve capacity , and marked increased post - intervention flow velocities in the ipsilateral cerebral artery2 ) . in our case ,
the patient had long - standing severe renal artery stenosis and high pre- and post - procedure pressure gradient .
, this case suggests the possibility of reperfusion injury to the kidney after percutaneous transluminal renal artery stent placement of severe long - standing renal artery stenosis .
renal artery stenosis is a cause of secondary hypertension which can be cured by surgical or radiological intervention such as percutaneous transluminal renal artery stent placement . in this case 
 we present a subcapsular hematoma of the kidney , a complication following percutaneous transluminal stent placement in the renal artery . 
 reperfusion injury to the kidney may be a possible mechanism of subcapsular hematoma of the kidney . 
 long standing severe renal artery stenosis and high pre- and post - procedure pressure gradient might contribute to the complication .