Defined as necrosis of papillae and inner portions of renal medulla (which receives 10% of renal blood flow).
When bilateral and diffuse, it may be associated with ARF, fever, chills, flank pain, and hematuria.
When insidious in onset, may manifest as a concentrating defect or as progressive renal failure.
Typically affects adults (>60 years).
Bilateral in 70% of cases.
May be associated with any number of disease entities, but most common is diabetes mellitus; also: analgesic abuse, sickle cell disease.
Pathogenesis is ischemic, related to marginal blood supply of medulla (which explains prevalence in patients with underlying vascular disorders such as diabetics); also vasoconstriction due to prostaglandin inhibition by NSAID.
Gross: necrosis of renal papillae/medullary portion (image A).
Coagulative necrosis rimmed by acute inflammation (image B).
Minimal inflammation at necrotic area.
Necrosis usually does not involve the entire medulla.
From a vascular standpoint, the papillary tip is the most vulnerable, so it is the first to go.
Because the necrosis is induced by ischemia, it typically has a coagulative appearance (ghost cells).
Microcalcifications may be present.
Renal changes of cause: diabetes nephropathy (diffuse nodular mesangial sclerosis), analgesic nephropathy (interstitial fibrosis, tubular atrophy, capillary sclerosis), and sickle cells (sickling in blood vessels) can be seen.
Prognosis depends on the causative factor and extent of damage and varies (diabetes worst).