Renal Sinus Angiomyolipoma: An Unusual Cause of a Pelvicalyceal Mass.

Renal angiomyolipomas (AMLs) are typically benign tumors of the renal cortex, often discovered incidentally. Although rare, AMLs can originate in the renal sinus and extend into the pelvicalyceal system, leading to obstructive uropathy and mimicking urothelial malignancies. We present the case of a 23-year-old female who was referred to our institution with right flank pain and hematuria. Imaging revealed a fat-containing mass in the right renal sinus extending into the pelvicalyceal system and causing ureteropelvic junction obstruction. A presumptive diagnosis of AML was made based on CT characteristics, which was later confirmed histopathologically following surgical excision. This case emphasizes the importance of recognizing the characteristic imaging features of AMLs, particularly in unusual locations, and highlights the role of biopsy in guiding conservative, nephron-sparing management.