Renal autotransplantation in a child following renal artery stent fracture.

We report an 8-year-old child who underwent percutaneous transluminal renal angioplasty (PTRA) and stenting for renal artery stenosis (RAS) and later presented with stent fracture. Ex vivo renal artery repair and renal autotransplantation were successfully done.

INTRODUCTION

Percutaneous transluminal renal angioplasty (PTRA), with or without stenting, is the treatment of choice for pediatric renal artery stenosis (RAS).[1] PTRA has been successful in 28-94% of children with renovascular hypertension (RVH).[1] Renal artery stent fracture leading to restenosis and refractory hypertension is a rare complication after this procedure.[2] The literature on stent fracture in RAS and its optimal management remains limited to a few case reports. We report a case of stent fracture with restenosis of renal artery in an 8-year-old child with left RAS post-PTRA and stenting, in whom successful autotransplantation of left kidney in the right iliac fossa was done. To our knowledge, this is the first case of renal artery stent fracture in a child managed with renal autotransplantation.

CASE REPORT

An 8-year-old male child presented to the Department of Cardiology with uncontrolled hypertension. He had undergone PTRA and stenting with 5 mm × 15 mm balloon expandable metallic stent at 2 years of age for 90% ostial stenosis of left renal artery. His blood pressure remained well controlled for the next 6 years. On admission now, his blood pressure was between 150/90 and 160/110 mm of Hg, on three antihypertensive drugs. A computed tomogram (CT) angiography revealed left renal artery stent fracture at the origin and 70% ostial stenosis with irregularity of the renal artery till the bifurcation [Figure 1a]. Renal scintigraphy with 99 m DTPA (diethylene triamine penta acetic acid) scan showed glomerular filtration rate (GFR) of 69 ml/min with a right to left ratio of 75:25. A repeat PTRA was attempted and confirmed the presence of renal artery stent fracture [Figure 1b]. However dilatation of the stenosed segment could not be done because of tight stenosis. He was referred to our department for surgical revascularization of left kidney. Autotransplantation of the left kidney was planned in view of the CT showing irregularity of the renal artery till the bifurcation. After laparoscopic dissection and retrieval, left kidney was perfused with Eurocollin's solution. On bench dissection, the stent containing stenosed part of the renal artery was excised which on further cut section showed that the fractured stent incorporated into the vessel wall and developed intimal hyperplasia [Figure 2]. The bifurcation of the renal artery was found to be intact. The autograft was implanted in the right iliac fossa with the renal artery anatomosed end to end with right internal iliac artery, renal vein anastomosed end to side with right external iliac vein and ureter implanted into dome of bladder with modified Lich's technique. The postoperative course was uncomplicated. His blood pressure gradually became normal. At 4 years after surgery, serum creatinine was 1.0 mg/dl, blood pressure was 110/70 mm of Hg and DTPA scan showed equal perfusion of both kidneys with total GFR of 90 ml/min.

Figure 1

(a) CT angiography done at 8 years of age showing 70% ostial stenosis of left main renal artery and irregularity of the artery extending till the bifurcation. (b) Percutaneous transluminal renal angiography showing the renal artery stent fracture

Figure 2

Bench dissection showing the stenotic segment of the renal artery and the stent incorporated into the arterial wall and excised segment of the renal artery with fractured stent and intimal hyperplasia (inset)

DISCUSSION

PTRA with stenting was utilized as the first step to achieve revascularization in this patient. Renal artery stent fracture is a rare complication which causes restenosis with refractory hypertension and can also result in renal artery thrombosis or pseudoaneurysm.[2-4] So far in the English literature, seven cases of renal artery stent fracture have been reported.[2-8] All reported cases were adults with mean age of 50.3 years (range 20-83 years). Our case posed a therapeutic challenge in view of his young age at the time of diagnosis of stent fracture.

The precise mechanism of stent fracture remains uncertain. The stents implanted in the left renal artery may be more susceptible to fracture than those placed in the right renal artery.[6] Renal mobility has been thought to play a role in stent fracture as it produces a continuous stress to the stent, resulting in metal fatigue and stent fracture.[7] It has also been hypothesized due to the compression of the renal artery by musculotendinous fibers originating from the diaphragm.[8] The optimal management of stent fracture remains to be defined. Repeat PTRA with stenting is generally not recommended for treating stent fracture.[2] Out of the seven case reports of renal artery stent fracture, kidney was salvaged in six patients either with aortorenal bypass or PTRA, whereas in one patient the left kidney has no residual function and percutaneous occlusion of the left renal artery was done.[4] After a mean follow-up of 12 months (range 2-24 months), these six patients were reported to be stable. In the present case, during PTRA dilatation of the stenosed segment could not be done because of tight stenosis. Aortorenal bypass was not considered in view of the irregularity of the renal artery till bifurcation.

Extracorporeal surgery and autotransplantation has been found to be safe and effective in pediatric patients with complex renal artery disease.[9] Jordan et al. have reported successful use of extracorporeal repair and renal autotransplantation in 14 out of 16 pediatric and young adult patients with renal artery disease.[9] This technique of renal revascularization is best used when vascular reconstruction is anticipated as was expected in the present case due to radiological appearance of involvement of main renal artery till the bifurcation. The excellent long-term outcomes following surgical treatment would be of definite advantage in pediatric patients especially with recurrent stenosis given the lack of long term results following stenting. Thus, in the case of renal artery stent fracture with refractory hypertension, renal autotransplantation can salvage kidney function and cure hypertension when endovascular treatment has failed.