Renal papillary necrosis
Renal papillary necrosis is ischemic coagulative necrosis of the renal medullary pyramids and papillae, most often from sickle cell disease or trait, chronic NSAID/analgesic use, diabetes mellitus, or acute pyelonephritis (the SAAD mnemonic), presenting with gross or microscopic hematuria and sometimes flank pain. It is a clinical diagnosis of exclusion, supported by mild pyuria and proteinuria on urinalysis and confirmed on noncontrast CT showing sloughed papillae, and management is discontinuation of the offending agent and treatment of the underlying cause, since no disease-specific drug therapy exists.
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What this article covers
- Overview
Renal papillary necrosis is ischemic coagulative necrosis of the medullary pyramids and papillae, caused by any condition that impairs medullary perfusion.
- Epidemiology
Sickle cell disease and sickle cell trait are leading causes, with sickle cell trait specifically associated with hematuria from renal papillary necrosis, splenic infarction at high altitude…
- Risk factors
Sickle cell disease or sickle cell trait: sickled erythrocytes obstruct the small vessels supplying the renal medulla, the region most vulnerable to ischemia.
- Pathophysiology
The renal medulla has an inherently low, hypoxic baseline blood flow and high metabolic demand for countercurrent concentration, making the papillae the most ischemia-vulnerable region of the kidney.
- Clinical features
Hematuria is the hallmark and most consistent finding, ranging from microscopic to grossly visible, sometimes with patient-reported passage of tissue clumps (sloughed papillae).
- Differential diagnosis
Glomerulonephritis: proteinuria and hematuria similar to papillary necrosis, but distinguished by red cell casts and/or dysmorphic erythrocytes on urine microscopy, absent in papillary necrosis; see iga-nephropathy.
- Diagnosis
Renal papillary necrosis is a clinical diagnosis of exclusion, established when hematuria with mild pyuria and proteinuria occurs in a patient with a SAAD risk factor after the more common causes of…
- Management
First, discontinue the offending agent, most commonly the causative NSAID or combination analgesic, since this is the single most important intervention and there is no drug therapy that reverses papillary necrosis itself.
- Complications
Progression to chronic kidney disease, the principal long-term complication when the underlying cause (analgesic use, uncontrolled diabetes, recurrent pyelonephritis) is not corrected.
- Prognosis
Prognosis is generally favorable when the offending cause is identified and removed promptly, with many patients experiencing resolution of hematuria without permanent kidney damage.
- Prevention
Limit chronic NSAID exposure to the lowest effective dose and shortest duration, and avoid combination analgesic regimens (an NSAID plus acetaminophen plus caffeine) taken daily for years, the…
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