Surgical Management and Outcomes of Renal Tumors Arising from Horseshoe Kidneys: Results from an International Multicenter Collaboration

Background: Despite being the most frequent renal fusion anomaly, tumors arising from horseshoe kidneys (HSKs) are extremely rare and management guidance is lacking. Objective: To evaluate the perioperative, oncological, and functional outcomes of surgically treated HSK tumors. Design, setting, and participants: A retrospective, multicenter cohort study of 43 HSK tumors in 40 patients was conducted, and technical description of the surgical approach has been provided. Surgical procedure: Surgical resection of renal tumors arising from HSKs was performed either via open surgery or via minimally invasive surgery (MIS). Measurements: We analyzed patient and tumor characteristics as well as surgical technique, and functional and oncological outcomes. Results and limitations: Eight patients were treated by MIS and 32 by open surgery. One patient (2.5%) experienced an intraoperative complication and 13 patients (32.5%) experienced postoperative complications, of which three (7.5%) were Clavien-Dindo >= 3 complications. Surgical margins were positive in two tumors (4.7%). The most frequent histology was clear-cell renal cell carcinoma (46.5%). The median follow-up was 51 (interquartile range [IQR] 17-73) mo. The 5-yr overall, cancer-specific, and recurrence-free survival rates were 81.2%, 86.8%, and 83.1%, respectively. The percent decreases in estimated glomerular filtration rate at discharge and the last follow-up were 15% (IQR 4-26%) and 17% (IQR 1-31%), respectively. Limitations include the cohort's retrospective nature, heterogeneity, and small sample size. Conclusions: Surgical management of tumors in HSKs can be approached via both open surgery and MIS, with maximal preservation of functional renal parenchyma. In this cohort, rates of complications, positive surgical margins, and renal functional decrease were acceptable, considering the anatomical complexity of these kidneys and tumors. These tumors display great variation in histological subtypes. Meticulous presurgical planning, taking advantage of advanced imaging techniques, can aid in achieving good outcomes. Patient summary: We evaluated the surgical management of renal tumors in horseshoe kidneys, which are very rare. Although these procedures are highly complex, outcomes are acceptable. Modern imaging techniques are often required in presurgical planning. (C) 2020 European Association of Urology. Published by Elsevier B.V. All rights reserved.