You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
a 31-year - old caucasian man was admitted to a hospital with severe renal failure .
he presented with a 1 week history of sudden onset of severe lower back and loin pain accompanied by swelling of both lower limbs and reduced urine output .
he had no past medical or family history , and was an ex - smoker .
apart from his work as a taxi driver , there was no history of immobility , long airline journeys or major physical exertion .
biochemically , he had severe renal failure ( creatinine 1167 mol / l = 13.2 mg / dl ) .
283 mg / l , erythrocyte sedimentation rate 55 mm and serum albumin 41 g / l . his clotting profile was normal , d - dimer was 15 570 ng / ml ( normal below 250 ) and creatinine kinase was 51 iu / ml .
the operator reported difficulty in cannulating the vein but on haemodialysis high venous pressure and poor blood flow were noted . this catheter was removed and further haemodialysis was carried out via a right internal jugular venous catheter .
the next day , computed tomography ( ct scan - venous phase contrast ) of thorax , abdomen and pelvis revealed complete venous thrombotic occlusion extending from both common femoral veins to the supra - renal inferior vena cava ( ivc ) , and both the renal veins were occluded with oedematous kidneys ( figure 1a ) .
( a ) initial contrast enhanced ct scan demonstrating acute thrombus and venous distension within the ivc ( solid arrow ) and left renal vein ( broken arrow ) .
( b ) magnetic resonance venography 3 months later demonstrating patency of the ivc ( arrow ) and bilateral renal veins ( arrow heads ) .
( a ) initial contrast enhanced ct scan demonstrating acute thrombus and venous distension within the ivc ( solid arrow ) and left renal vein ( broken arrow ) .
( b ) magnetic resonance venography 3 months later demonstrating patency of the ivc ( arrow ) and bilateral renal veins ( arrow heads ) .
the interventional radiologists started thrombolytic therapy : initially , venous access was gained in the left femoral vein and digital subtraction venography demonstrated near - occlusive thrombus extending from the femoral vein to the supra - renal ivc as seen on ct . at this point , a 20 cm cragg - mcnamara thrombolysis catheter ( ev3 ) was placed along the length of the ivc and a recombinant tissue plasminogen activator ( rtpa ) was administered as a bolus of 5 mg , followed by a continuous infusion of 1 mg / h for 12 h. a simultaneous infusion of unfractionated heparin at a rate of 500 iu / h was given through the femoral vascular access sheath for 48 h. repeat venography at 12 and 48 h showed some minor improvements but still significant residual thrombus . then , renal venography and thrombolysis were attempted via a right internal jugular vein approach after placement of a vascular access sheath . imaging from here
identified supra - renal ivc stenosis , which was angioplastied with a 12 mm diameter balloon .
venography showed heavy thrombus burden within the left renal vein and thrombus at the origin of the right renal vein .
a new cragg - mcnamara ( ev3 ) thrombolysis catheter was positioned in the left renal vein thrombus and further rtpa bolus ( four pulse spray of 1 mg ) followed by continuous infusion ( 1 mg / h ) was given .
right renal vein patency was gained by suction thrombectomy of the thrombus at its origin and balloon angioplasty of the same region to disperse residual thrombus .
venography 48 h later showed complete patency of both renal veins ; the supra - renal ivc stenosis was apparent and a 22 mm  80 mm sinus xl stent was deployed across this successfully .
urine output resumed on the third day of starting thrombolysis , oedema gradually settled and the creatinine level continued to improve ( figure 2 ) .
the antiphospholipid screen was negative [ protein c 130 u / dl ( 66122 ) , protein s 112 u / dl ( 74146 ) , antithrombin iii 134 u / dl ( 75140 ) , activated protein c ratio 2.99 [ > 2.1 ] , factor v leiden absent , lupus anticoagulant negative , anti-2-glycoprotein i antibodies 2 u / ml ( 020 ) , cardiolipin antibodies igg < 12 u / ml ( 012 ) and igm < 10 u / ml ( 010 ) ] .
magnetic resonance venography ( figure 1b ) at 3 months confirmed patency of all veins and the stented ivc segment .
eight months after initial presentation , the creatinine level was still normal at 76 mol / l . 

acute renal vein thrombosis is an uncommon condition that may present with loin pain and haematuria , or proteinuria .
bilateral acute , complete renal vein occlusion is very rare and results in oliguric acute renal failure .
predisposing causes include nephrotic syndrome , thrombophilic states , endovascular intervention , malignancy ( tumour thrombosis ) , major physical exertion ( running a race ) or trauma [ 25 ] .
uncommonly , no underlying cause is found as in our case [ 6 , 7 ] .
a short supra - renal stricture in the ivc can be contributory [ 2 , 7 , 8 ] .
possible treatment options beyond anticoagulation include selective or systemic thrombolysis , mechanical thrombectomy and surgery , but the optimal management for this condition is not established .
two decades ago , laville et al . described 27 patients with renal vein thrombosis , 18 of which were bilateral ; 9 patients had thrombosis involving ivc ; the authors found no difference in renal function recovery between endovascular intervention versus anticoagulation alone .
however , these patients had underlying renal parenchymal disease including nephrotic syndrome , unlike our case .
more recently , kim et al . reported six patients with renal vein thrombosis ( two renal allograft , three unilateral native kidneys and one bilateral native kidney ) .
endovascular treatment resulted in some renal function improvement in all patients but here again there was pre - existing renal disease .
our patient had severe , dialysis - dependent renal failure due to bilateral renal vein occlusion , but made a complete renal recovery after 7-day treatment of intense selective venous thrombolysis , even though treatment did not start until 10 days after initial presentation .
the absence of pre - existing renal disease in our patient may have aided full recovery .
although systemic thrombolysis is used by some , in our experience repeated catheter - directed treatments for such extensive thrombus burden are more effective and safe .
we conclude that aggressive endovascular intervention with selective thrombolysis can restore bilateral renal vein patency and renal function recovery , even with prolonged venous occlusion .
whilst repeated selectively delivered thrombolysis is a well - established endovascular technique , this is the first report of complete renal recovery after extensive spontaneous thrombosis .
a previously healthy young man presented with acute renal failure due to extensive spontaneous deep vein thrombosis , including the inferior vena cava ( ivc ) and both renal veins . 
 the patient was treated with selectively delivered thrombolytic therapy over a 7-day - period , which resulted in renal vein patency and complete recovery of renal function . 
 a stent was placed over a segment stenosis of the ivc . 
 no thrombophilic factors were identified . 
 bilateral renal vein thrombosis in young fit individuals is an unusual cause of acute renal failure . 
 thrombolytic therapy , even with delay , can completely restore renal function .