Renal papillary necrosis is ischemic, coagulative necrosis of the renal medullary pyramids and papillae and is a feature of various conditions.
Epidemiology
Etiology
- Often multifactorial
- Sickle cell disease and sickle cell trait
- Acute pyelonephritis
- Obstruction of the urinary tract
- Tuberculosis
- Cirrhosis of the liver
- NSAIDs (due to inhibition of prostaglandin-mediated vasodilation in the vasa recta)
- Diabetes mellitus
Pathophysiology
- Coagulative necrosis of the renal papillae and medullary pyramids due to ischemia. The renal medulla is naturally a low oxygen tension environment, making it vulnerable to ischemic injury.
- Ischemia can result from direct vascular obstruction (e.g., sickle cell), vasoconstriction (e.g., NSAIDs), or inflammation.
Clinical features
- Can be asymptomatic and found incidentally.
- Symptomatic patients may present with:
- Acute flank pain and renal colic (due to obstruction by sloughed papillae).
- Sloughed papillae can obstruct the ureters.
- Gross or microscopic hematuria.
- Fever and chills, especially if a superimposed infection (pyelonephritis) is present.
- Passage of necrotic tissue in the urine.
- Acute flank pain and renal colic (due to obstruction by sloughed papillae).
- Sudden deterioration of kidney function in a patient with a known risk factor (e.g., diabetes) should raise suspicion.
Acute tubular necrosis vs Renal papillary necrosis
- ATN: Oliguria
- Causes: ischemic or toxic
- RPN: Flank pain, hematuria
- Causes: sickle cell disease, NSAIDs