Diagnosis, Management, and Challenges in Synchronous Bilateral Wilms Tumor in a Horseshoe Kidney: A Case Report.

Horseshoe kidney (HK) refers to a congenital malformation that results from fusion of both the kidneys at one pole, and is the most common renal fusion defect with an incidence of 1 in 400 to 600 individuals. Synchronous bilateral development of Wilms tumor (WT) in an HK is extremely rare. Here, we present a case of synchronous bilateral WT in an HK in an 18-month-old girl. The patient received 12 weeks of preoperative chemotherapy followed by 2-step surgical resection including nephron-sparing surgery (NSS) in both kidneys and left nephrectomy because of positive surgical margin and adjuvant chemotherapy. The patient is still in remission and asymptomatic 6 months after the completion of treatment. In this report, we discuss the treatment modalities of synchronous bilaterally located WT in HK. We conclude that successful outcomes can be obtained with preoperative chemotherapy and NSS in such cases even in the presence of advanced disease and complex anatomic conditions. In addition, the deepest tumor point can be reached during NSS, but total nephrectomy should be considered regarding the possibility of microscopic residue.