Makindo Medical Notes

Renal Papillary Necrosis (RPN) = ischaemic necrosis of the renal papillae, which may slough into the collecting system and obstruct urine flow. 💡 The medulla is already relatively hypoxic and hypertonic, making papillae especially vulnerable.

📖 About

• RPN = ischaemic destruction of renal papillae due to reduced medullary blood supply.
• Seen especially in patients with diabetes, sickle cell disease, or chronic NSAID use.
• May be silent or present with haematuria, infection, or obstruction.

📊 Epidemiology

• More common in older diabetic patients (due to vascular disease + infection susceptibility).
• In sickle cell disease/trait, may occur in younger adults due to vaso-occlusion.
• Analgesic nephropathy historically caused many cases (now rarer).

🧬 Pathophysiology

• Papillae = “watershed zone” → furthest from main renal arterial supply.
• Ischaemia → necrosis → papilla detaches and sloughs into ureter/collecting system.
• Results in obstruction, secondary infection, or haematuria.
• Necrosis may be focal (single papilla) or diffuse (multiple papillae).

🔑 Causes (Mnemonic = POSTCARDS)

• Pyelonephritis
• Obstruction (stones, strictures)
• Sickle cell disease/trait
• Tuberculosis
• Cirrhosis / chronic liver disease
• Analgesic abuse (esp. NSAIDs)
• Renal vein thrombosis
• Diabetes mellitus
• Systemic vasculitis (e.g. PAN)

🩺 Clinical Features

• Asymptomatic (incidental finding).
• Colicky flank pain if papilla obstructs ureter.
• Macroscopic or microscopic haematuria.
• Sterile pyuria ± passage of necrotic tissue fragments.
• Fever, dysuria, or sepsis if complicated by infection.

🔎 Investigations

• Bloods: U&E (AKI/CKD status).
• Urinalysis: haematuria, mild proteinuria, sterile pyuria.
• Imaging:
  • CT urography: diagnostic test of choice → shows non-enhancing cavities in papillae, filling defects, or sloughed papillae.
  • IVP (historical): “ring sign” = contrast outlining necrosed papilla.
• EM exam pearl: “sloughed papilla” visible in urine specimen.

⚕️ Management

• 🔹 Supportive: hydration, analgesia, avoid nephrotoxins (esp. NSAIDs).
• 🔹 Treat cause: antibiotics for pyelonephritis, optimise diabetic control, treat sickle cell crisis, address TB/vasculitis.
• 🔹 Relieve obstruction: endoscopic retrieval, stent, or nephrostomy if sloughed papilla blocks ureter.
• 🔹 Prevention: risk factor modification, treat infections promptly, avoid prolonged NSAID use.

🌟 Summary: Renal Papillary Necrosis = ischaemic necrosis of renal papillae → obstruction, haematuria, infection. Mnemonic: POSTCARDS (Pyelonephritis, Obstruction, Sickle cell, TB, Cirrhosis, Analgesics, Renal vein thrombosis, Diabetes, Systemic vasculitis). Diagnosis: CT urography (ring defect, sloughed papilla). Management: supportive + treat cause + relieve obstruction.