Bilateral Renal Cell Carcinoma in the Horseshoe Kidney With Metastasis in Gallbladder, Pancreas and Duodenum: A Report of a Rare Case and Literature Review.

Horseshoe kidney is the most common renal fusion anomaly and is associated with various complications, ranging from infections to neoplasms. While renal cell carcinoma (RCC) is the most frequent renal neoplasm in adults, its occurrence in a horseshoe kidney is rare, and bilateral involvement is rarer. Furthermore, RCC metastasizing to organs is known and rare sites of metastasis are also documented. The report presents a unique case of bilateral RCC in a horseshoe kidney with synchronous metastasis to the gallbladder, pancreas, and duodenum. This presentation, involving metastasis to these specific organs, is exceedingly uncommon, making it a rarest of rare possibilities. The current case report underscores the importance of vigilant monitoring and comprehensive evaluation in patients with horseshoe kidneys, as they may be predisposed to unusual complications like RCC and rare site metastasis.