CPT code 50391 denotes the instillation of a therapeutic agent—such as an anticarcinogenic or antifungal medication—directly into the renal pelvis and/or ureter via a pre-existing nephrostomy, pyelostomy, or ureterostomy tube. This targeted local therapy is used in select urologic and oncologic contexts to deliver medication to the upper urinary tract and can reduce systemic exposure while concentrating treatment at the disease site. Nationally, the code matters for hospitals, interventional radiology services, and urology practices that manage patients with urinary tract stomas or nephrostomy access.

Key payers in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical purpose and service setting, common billing modifiers and practical billing context, and pointers to related procedural and diagnosis coding where available. The publication summarizes typical sites of service and the procedural intent, clarifies common modifier usage patterns, and highlights areas where payers commonly require documentation to support the medical necessity of local instillation therapies. Data not available in the input will be noted explicitly in relevant sections.