Tumors in kidney fusion anomalies - Report of five cases and review of the literature

Objective: Fusion anomalies of the kidney are rarely encountered and the association of malignant tumors with such conditions is exceedingly rare. Association of tumors with horseshoe kidney is also uncommon, with fewer than 200 cases having been reported in the literature, and the association of tumors with crossed-fused ectopia is even rarer, with only four cases having been reported so far. Material and Methods: During the past decade five patients with fusion anomalies have been treated for tumors in our clinic, four of whom had horseshoe kidney and one of whom had crossed-fused left-to-right ectopia. The clinical, diagnostic and operative peculiarities of each case are presented and the recent literature on this topic is reviewed. Results: Two patients were diagnosed with renal cell carcinoma, two had transitional cell carcinoma and one had oncocytoma. Conclusions: The commonest tumor reported in kidney fusion anomalies is renal cell carcinoma, although its reported incidence is no higher than that in the normal population. In the case of transitional cell carcinomas, diagnosis is usually made at an advanced stage. The value of thorough urologic and radiological investigations is stressed. Angiography, whether classical or in combination with multi-slice CT, is considered essential in order to confirm renal anomalies and the tumor situation and to plan the surgical approach. In our experience, radical nephrectomy with isthmus division via a transperitoneal approach is the treatment of choice.