Renal Papillary Necrosis (RPN) = ischaemic necrosis of the renal papillae, which may slough into the collecting system and cause haematuria, infection, or urinary obstruction.
💡 The renal medulla is relatively hypoxic and hyperosmolar even in health, making the papillae especially vulnerable to ischaemic injury.
📖 About
- RPN is ischaemic destruction of the renal papillae due to impaired medullary blood supply.
- It may occur in association with diabetes, sickle cell disease or trait, upper urinary tract infection, obstruction, and analgesic / NSAID-related renal injury.
- Presentation ranges from incidental microscopic haematuria to renal colic, obstruction, or sepsis.
📊 Epidemiology
- Often seen in people with underlying renal vascular compromise or chronic renal stressors.
- In sickle cell disease/trait, papillary necrosis may occur in younger adults because the hypoxic, hypertonic medulla promotes sickling and microinfarction.
- Historically, analgesic nephropathy caused many cases; this is less common now than in the phenacetin era.
🧬 Pathophysiology
- The papillae lie at the end of the renal medullary circulation and behave like a vascular watershed zone.
- Reduced perfusion leads to medullary and papillary infarction, followed by coagulative necrosis.
- Necrotic papillae may detach and slough into the renal pelvis or ureter.
- This can cause colicky pain, filling defects on imaging, hydronephrosis, or secondary infection.
🔑 Important Causes / Associations
- Diabetes mellitus
- Sickle cell disease or trait
- Pyelonephritis / severe upper urinary tract infection
- Obstruction of the upper urinary tract
- Chronic analgesic / NSAID-related nephropathy
- Renal tuberculosis and other chronic inflammatory conditions (less common)
- Vascular compromise or vasculitic disease in selected cases
🩺 Clinical Features
- Asymptomatic or incidental microscopic haematuria.
- Flank pain or renal colic if a sloughed papilla obstructs the ureter.
- Macroscopic or microscopic haematuria.
- Sterile pyuria may occur, especially in analgesic nephropathy.
- Passage of tissue fragments in urine is a classic but uncommon clue.
- Fever, dysuria, or sepsis if there is superimposed infection.
- May present with AKI or worsening CKD if bilateral or recurrent.
🔎 Investigations
- Bloods: U&E, creatinine/eGFR, inflammatory markers if infection is suspected.
- Urinalysis: haematuria, pyuria, mild proteinuria; send urine for microscopy/culture if infection is possible.
- Imaging:
- CT urography is often the preferred imaging test when RPN is suspected and anatomy, obstruction, or collecting-system defects need to be defined.
- Findings may include papillary excavation, ring-like contrast outlining a necrosed papilla, filling defects, or a sloughed papilla in the pelvis/ureter.
- Older IVU/IVP descriptions include the classic “ring sign”.
- Ultrasound may show hydronephrosis if obstruction has developed, but can miss early papillary disease.
⚕️ Management
- 🔹 Supportive care: hydration, treat AKI if present, and stop nephrotoxins - especially NSAIDs.
- 🔹 Treat the underlying cause: antibiotics for pyelonephritis, optimise diabetic control, manage sickle-cell-related complications, and investigate chronic inflammatory or infective causes where relevant.
- 🔹 Relieve obstruction urgently if a sloughed papilla causes hydronephrosis, uncontrolled pain, infection, or renal impairment - for example with ureteric stenting or nephrostomy depending on the situation.
- 🔹 Prevent recurrence: avoid prolonged NSAID exposure, manage diabetes well, and treat UTIs promptly.
🌟 Summary:
Renal papillary necrosis is ischaemic injury to the renal papillae in a medulla that is already physiologically vulnerable.
Think of it in patients with diabetes, sickle cell disease/trait, upper UTI, obstruction, or chronic analgesic use who develop haematuria, flank pain, or obstructive symptoms.
Management is: recognise it, treat the cause, stop nephrotoxins, and relieve obstruction if present.
📚 References
