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.
