The renal papilla is the location where the renal pyramids in the medulla empty urine into the minor calyx in the kidney. Histologically it is marked by medullary collecting ducts converging to form a papillary duct to channel the fluid. Transitional epithelium begins to be seen.
Some chemicals toxic to the kidney, called nephrotoxins, exert their damage at the renal papillae. Damage to the renal papillae may result in death to cells in this region of the kidney, called renal papillary necrosis. The most common toxic causes of renal papillary necrosis are NSAIDs, such as ibuprofen, acetylsalicylic acid, and phenylbutazone, in combination with dehydration.
This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)