The renal medulla contains the structures of the nephrons responsible for maintaining the salt and water balance of the blood.

Though the renal medulla only receives a small percentage of the renal blood flow, the oxygen extraction is very high, causing a low oxygen tension and more importantly, a critical sensitivity to hypotension, hypoxia, and blood flow.

[4] The broad base of each pyramid faces the renal cortex, and its apex, or papilla, points internally towards the pelvis.

The pyramids appear striped because they are formed by straight parallel segments of nephrons' Loops of Henle and collecting ducts.

The base of each pyramid originates at the corticomedullary border and the apex terminates in a papilla, which lies within a minor calyx, made of parallel bundles of urine collecting tubules.

The most common toxic causes of renal papillary necrosis are NSAIDs[dubious – discuss], such as ibuprofen, acetylsalicylic acid, and phenylbutazone, in combination with dehydration.