Autotransplant and Renal Artery Aneurysm Repair in a Patient with a Congenital Solitary Kidney

Case Report

A 44-year-old, normotensive woman with a 28-pack year history of smoking and a congenital solitary kidney was referred for a right renal artery aneurysm (RAA) seen on magnetic resonance imaging (MRI). The MRI was done as part of a work up for back pain 2 years previously. The patient subsequently had a computed tomography (CT) angiogram where a 2-cm aneurysm was seen in the right renal artery at the hilum of the kidney, with 5 of 7 branches of the renal artery arising from the aneurysm, excluding endovascular repair. The patient initially opted for watchful observation. She was then referred to us for a second opinion. She continued to have intermittent back pain, which was relieved with narcotics and muscle relaxants. The patient remained normotensive without peripheral edema, and renal function was normal with serum creatinine of 0.9 mg/dL and a normal urinalysis. Work up for vasculitis was negative, with normal serologies and normal erythrocyte sedimentation rate and C-reactive protein. CT angiogram was repeated after consultation, which showed a stable, 2-cm aneurysm, and a new 6 x 8 mm polar branch aneurysm. Repeat CT angiogram 10 months later showed 2 RAA, a 2-cm right RAA that had remained stable, and the polar branch aneurysm had increased in size to 7 x 9 mm. At this point, a difficult decision had to be made. One could argue that since the larger aneurysm was stable in size, embolization of the smaller aneurysm would suffice. However, embolization would result in a loss of more kidney function in a person who already has compromised function from a solitary kidney. Also, since she was young and the larger aneurysm, though stable, was approaching the critical size for repair, it was thought to be more prudent to repair both aneurysms and not just the smaller one. Because of the complexity of the larger aneurysm, with smaller arterial branches arising from the aneurysm and the location in the renal hilum, endovascular repair was impossible. The patient had an ex-vivo repair of the RAA and a renal autotransplant. The small aneurysm was ligated at the base, and the large aneurysm was completely resected, followed by end-to-end anastomosis of the main renal artery and branches. Of note, no leak was seen at surgery to account for the patient’s back pain. The University of Wisconsin Solution was used to irrigate the autotransplant. The kidney was transplanted into the right lower quadrant, and anastomoses of the renal vessels were made to the common iliac vessels. Pathology of the renal aneurysm revealed atherosclerosis and calcification. The patient recovered from her surgery uneventfully and renal function remained normal at the 6-month follow up. No long-term complications were noted.

Incidence

RAA is a rare condition caused by focal dilatation of the renal artery, secondary to weakness of one or more layers of the vessel wall. It was first reported in 1770 by Rouppe¹ when he reported the death of a sailor after hitting his right flank following a fall. Subsequent autopsy revealed a large, false aneurysm with rupture.¹ More cases have since been reported, presumably from increased use of radiographic techniques. Primary RAA has been estimated to account for 0.09–0.1% of all aneurysms^2–4 and 15–25% of all visceral aneurysms.^2,5 RAA is more common in women than in men and frequently affects the right renal artery more than the left, except in pregnancy where the left renal artery seems to be more commonly involved.^3,4

Signs and Symptoms

Most RAA are asymptomatic and are found incidentally when radiologic imaging is performed for different reasons. Symptoms may include hypertension, flank pain, hematuria, hydronephrosis from obstruction, renal infarction, and rupture, causing death.

Renal Artery Repair (RAR)

The classic therapy for RAA has been surgery. Principal techniques for aneurysm repair include renal artery resection and reanastomosis, graft interposition, aortorenal bypass, and autoplastic reconstruction.^6,9 Surgical approaches for the treatment of aneurysms are technically challenging, although, in expert hands, they have relatively low mortality and morbidity. More recently, endovascular therapies have emerged as viable options. The two main approaches used are: 1) stent grafts for main renal arteries (mainly in RAA with narrow necks, although intervention in RAA with wide neck has been reported) and 2) embolization (with elimination of aneurysm and limited renal infarct) for branch arteries.^2,5,9,11,12 Published data seem to indicate that endovascular techniques in experienced hands are viable options in RAA, although results are lacking to prove the long-term durability of grafts and the patency of renal vasculature.

Reasons for Intervention

At present, the natural history and clinical significance of RAA remains unclear and thus controversial. The most common reason for intervention is the fear of rupture. Most people believe that the risk of rupture is small,^4,13,14 except in the case of pregnancy. Pregnancy is associated with increased blood flow and intra-abdominal pressure, and vessel wall changes from hormonal alterations are thought to play a role in predisposing to rupture.³ Ruptures have been reported to carry a maternal mortality rate of 70–80%² and a fetal mortality rate of 100%.⁴ Of the mentioned indications, the management of RAA > 2 cm and those aneurysms causing renovascular hypertension are the most controversial and the most debated. Size cut-off for RAA remains controversial. Some older series reported no ruptures in patients followed conservatively using this size cut-off,^4,13 while occasional cases are reported of ruptures, even with a diameter of 1 cm, as well as total renal artery thromboses in an unrepaired RAA.¹⁴ Hypertension is associated in up 70–80% of cases, and may or may not be from renovascular hypertension.⁴ RAA may cause secondary hypertension by the following mechanisms: occult stenoses, arterial compression, parenchymal embolization, and branch vessel compromise.^4,9 At the same time, preexisting hypertension in patients with congenital defects in the renal artery vascular wall may very well predispose to aneurysm formation. Thus, it is not surprising that the cure rate and improvement of hypertension with RAA varies.^4,13 Even then, most larger series report at least a 50% improvement and/or cure in hypertension regardless of the cause and thus advocate for RAR in RAA associated with hypertension.

Renal Autotransplant

There have been case reports on the safety and effectiveness of renal explantation, ex-vivo or in-vitro RAR, followed by heterotopic autotransplantation. The procedure was performed in cases when patients had complex renal artery disease with solitary kidneys^15,16 and bilateral kidneys.^17,18 In all cases, nephrectomy was avoided. The most feared complication of autotransplant in a solitary kidney is loss of function of that kidney and the patient ending up on dialysis; although, of the cases reported in the literature, all have been successful, with no other morbidities reported.

Conclusion

This is an interesting approach to management of a patient with complex RAA and a solitary kidney. Due to the location of the aneurysms and the enlarging size of the second aneurysm, a conservative approach to management may have resulted in rupture and possible death. The risks of surgery also were increased with the possible loss of a solitary functioning kidney and the possibility of a patient requiring chronic dialysis. The surgical approach here included renal explantation, ex-vivo renal preservation, ex-vivo renal artery repair, and heterotopic autotransplantation. We conclude that this is a safe and effective strategy for patients with RAA and solitary kidneys.