Renal Cell Carcinoma Masquerading as Acute Upper Gastrointestinal Bleeding.

Acute upper gastrointestinal bleeding (UGIB) is a medical emergency with most common cause being peptic ulcer disease (PUD) or variceal bleeding. However, cancers that cause UGIB by invading the small intestine are uncommon, and the invasion of renal cell carcinoma (RCC) into the duodenum is an even rarer occurrence. A 55-year-old male presented with melena and right flank pain. Esophagogastroduodenoscopy (EGD) revealed an active bleeding source in the duodenum, later identified on contrast-enhanced computed tomography (CECT) as a duodenorenal fistula (DRF) caused by direct extension of the RCC. The imaging confirmed the presence of a malignant renal mass infiltrating adjacent organs. This atypical presentation of RCC with DRF manifesting as UGIB underscores the importance of comprehensive evaluations in cases of gastrointestinal bleeding to identify rare underlying causes.