Introduction: Horseshoe kidney (HK) is the most common renal fusion anomaly, with an estimated incidence of 1/666.¹ Tumors arising from HK are rare and management guidance is sparse. This study aimed to report on the surgical management and oncological outcomes of patients treated for HK tumors.

Methods: We retrospectively reviewed the medical records of nine patients treated at a single institution for tumors involving HKs between 2000 and 2020. Demographics, operative details, pre/postoperative course, histopathology, and oncological information were collected.

Results: The study cohort included six male and three female patients (Table 1). Five patients underwent radical heminephrectomy; two underwent open partial nephrectomy, nephroureterectomy was performed on two patients. Tumor histologies were clear-cell renal cell carcinoma (ccRCC) in five patients, papillary RCC (pRCC) in two patients, and high-grade non-invasive urothelial carcinoma (UC) in two patients. One patient had a concomitant, localized, low-grade kidney leiomyosarcoma with hilar lymph node metastasis of ccRCC (following a previous partial nephrectomy of ccRCC). Tumor size ranged from 3.5–8 cm. All cases had negative surgical margins. Additional preoperative imaging was performed in 7/9, and accessory blood vessels were identified in 7/9 patients. Five patients had a postoperative complication, including one major (Clavien grade 5, death due to acute myocardial infarction) and four minor (Clavien grade ≤2) complications (Table 2). During a median followup of 39 months (range 8–67), three ccRCC patients developed distant metastasis and one patient with UC developed a bladder recurrence. None of the patients developed new-onset chronic kidney disease.

Conclusions: Treatment of tumors in HKs can be managed by partial and hemi-nephrectomy. This can be done safely with acceptable operative and oncological outcomes. Preoperative imaging of the blood vessels is necessary, as most patients have an accessory blood supply.