Condition Deep-Dives 10 min read·Updated 22 July 2026 Clinician-reviewed

Renal Papillary Necrosis

A UK Consultant Nephrologist on renal papillary necrosis — an often-missed cause of haematuria, recurrent UTIs and unexplained CKD, especially in diabetic patients.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

View Credentials

Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

Ischaemic necrosis of the renal papilla. Think POSTCARDS — Pyelonephritis, Obstruction, Sickle cell, TB, Cirrhosis, Analgesics, RVT, Diabetes, Systemic vasculitis. Diagnose with CT urography. Treat the cause; relieve obstruction from sloughed papillae.

Key recommendation: Diabetes is the commonest UK cause.

Quick answer

✓ Best choices

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

✓ Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Key takeaway

Ischaemic necrosis of the renal papilla. Think POSTCARDS — Pyelonephritis, Obstruction, Sickle cell, TB, Cirrhosis, Analgesics, RVT, Diabetes, Systemic vasculitis. Diagnose with CT urography. Treat the cause; relieve obstruction from sloughed papillae.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Renal Papillary Necrosis

Pathophysiology

Anatomy

  • Medulla supplied by vasa recta from juxtamedullary efferent arterioles
  • Counter-current flow → low pO2 in inner medulla
  • Papilla is most distal — most vulnerable to ischaemia
  • Any insult reducing medullary perfusion (microangiopathy, sickling, vasoconstriction, infection, obstruction) can cause necrosis

Mechanisms

  • DIABETES: small-vessel disease + recurrent infection
  • SICKLE CELL: red-cell sickling in hypoxic medulla
  • ANALGESICS: chronic NSAID/phenacetin → reduced medullary prostaglandins → vasoconstriction
  • OBSTRUCTION + INFECTION: pressure necrosis + bacterial toxins
  • RVT, vasculitis: direct vascular compromise

Clinical presentation & diagnosis

Presentation

  • Painless gross haematuria (commonest)
  • Recurrent or unusually severe pyelonephritis
  • Flank pain — can mimic ureteric colic (sloughed papilla in ureter)
  • Passage of sloughed tissue per urethra
  • Unexplained AKI or progressive CKD in known risk group
  • Sterile pyuria

Investigation

  • Urinalysis: blood, leucocytes, occasionally necrotic papillary fragments
  • MSU for culture
  • FBC, U&E, glucose, HbA1c, sickle screen (if appropriate)
  • Bloods to assess underlying cause
  • Urine cytology — may show necrotic tubular cells
  • CT UROGRAPHY (CTU): imaging of choice

– medullary cavitation – 'lobster claw' sign — contrast tracking around sloughed papilla – 'ring shadow' — sloughed papilla within calyx – ureteric filling defects – ureteric obstruction proximal to fragment

  • MR urography — alternative if iodinated contrast contraindicated
  • Cystoscopy ± retrograde pyelography occasionally needed

Management

Treat Underlying Cause

  • Diabetes: optimise glycaemic control (HbA1c target individualised); SGLT2i for renal protection
  • Sickle cell: hydration, hydroxycarbamide, transfusion as per haematology; avoid dehydration
  • Stop NSAIDs and combination analgesics (paracetamol monotherapy is safer)
  • Treat tuberculosis if confirmed (RIPE regimen — caution rifampicin/CKD)
  • Relieve obstruction urgently
  • Aggressive treatment of infection

Acute Obstruction From Sloughed Papilla

  • Hydration
  • Analgesia (paracetamol; cautious low-dose opioid; AVOID NSAIDs)
  • Urological referral — JJ stent, ureteroscopy with stone-basket extraction of papillary fragment
  • Nephrostomy if infected obstructed system

Long-term

  • Annual U&E, eGFR, ACR
  • Renal ultrasound every 1–2 years
  • CKD pathway: ACE-i / ARB, SGLT2i (eGFR > 20), statin, BP target < 130/80
  • Avoid further nephrotoxins (NSAIDs, gentamicin)
  • Vaccinations (pneumococcal, influenza)

Prevention

  • Limit chronic NSAID use to shortest course needed
  • Combination analgesics (codeine + paracetamol + aspirin / caffeine) — avoid long-term use
  • Maintain hydration in sickle cell, diabetics
  • Tight diabetes control
  • Prompt treatment of UTI in at-risk groups
Sickle Cell Nephropathy
Related reading: Sickle Cell Nephropathy.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Cook from scratch when you can
  • Read sodium labels (≤ 0.3 g per 100 g is low)
  • Take any concerns to your GP or renal team early

Clinical guidance

TL;DR summary

Ischaemic necrosis of the renal papilla. Think POSTCARDS — Pyelonephritis, Obstruction, Sickle cell, TB, Cirrhosis, Analgesics, RVT, Diabetes, Systemic vasculitis. Diagnose with CT urography. Treat the cause; relieve obstruction from sloughed papillae.

Key takeaways
  • Diabetes is the commonest UK cause.
  • Avoid chronic NSAIDs in at-risk patients.
  • CT urography is the imaging of choice.
  • Sloughed papillae can cause ureteric obstruction.
  • No reversal — focus on slowing further CKD.
Kidney Diet & Nutrition Considerations

Diet is one of the most powerful tools you have to look after your kidneys. UK renal guidance points to a Mediterranean-style, reduced-salt pattern: plenty of vegetables, lower-potassium fruit, whole grains, sensible protein, beans and pulses in moderation, oily fish and olive oil. Personal targets — for potassium, phosphate, protein and fluid — should be set by your renal team based on your bloods.

Foods to prioritise

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What is renal papillary necrosis?

Renal papillary necrosis (RPN) is ischaemic necrosis of one or more renal papillae — the tip of the medullary pyramid where collecting ducts open into the calyx. Sloughed papillae can cause obstruction, haematuria, infection and chronic kidney disease. The medulla has a precarious blood supply that makes it particularly vulnerable to ischaemia from microvascular disease, infection or toxins.

What causes it?

Mnemonic POSTCARDS: Pyelonephritis (severe), Obstruction, Sickle cell disease/trait, Tuberculosis, Cirrhosis (alcohol), Analgesic nephropathy (chronic NSAIDs, phenacetin historically), Renal vein thrombosis, Diabetes mellitus (commonest), Systemic vasculitis. Diabetes is the leading cause in the UK; analgesic nephropathy from long-term combination analgesics is now rare but still seen in older patients.

How is it diagnosed?

Suspect in a patient with one of the above risk factors and any of: gross haematuria, recurrent UTIs, loin pain (ureteric colic from sloughed papilla), unexplained AKI or progressive CKD. CT urography (CTU) is the imaging of choice: medullary cavitation, 'lobster claw' sign, 'ring shadow' from sloughed papilla within the calyx, and sometimes filling defects in the ureter. MR urography is the alternative if contrast contraindicated. Urine cytology may show necrotic papillary tissue.

How is it managed?

Treat the underlying cause: optimise glycaemic control (diabetes), stop NSAIDs/combination analgesics, treat sickle cell with hydration and crisis avoidance, relieve obstruction, treat infection vigorously. Sloughed papillae causing acute obstruction may need urological intervention (stent, ureteroscopy). There is no specific reversal — the goal is to prevent further necrosis and progression to CKD. Adequate hydration is essential, especially in sickle cell and analgesic users.

What foods are good for kidney health?

A Mediterranean-style, mostly plant-based, reduced-salt diet is the most consistent evidence-based pattern for kidney health. Build meals around vegetables, lower-potassium fruit, whole grains, fish, eggs or tofu, beans and pulses in moderation, and olive oil.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK guidance

Aligned with NICE NG203 chronic kidney disease, KDIGO 2024 CKD evaluation, BAUS urology pathways and MHRA NSAID guidance.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Cause-led & CKD-protective

Practical guidance on the POSTCARDS aetiology, CT urography and avoiding further nephrotoxic injury.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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