Medullary kidney disease · KIMS Secunderabad
Renal Papillary Necrosis — When the Inner Kidney Tissue Dies and Sloughs Off
Renal papillary necrosis (RPN) is ischaemic necrosis of the renal papillae — the triangular apices of the medullary pyramids that project into the renal calyces. The renal papillae occupy the innermost zone of the kidney, where blood supply is most tenuous — the vasa recta capillaries that supply the papillary tip are long, thin, and subject to ischaemia when renal medullary blood flow is compromised. When papillary ischaemia is severe and sustained, the papillary tissue undergoes coagulative necrosis, the necrotic papilla detaches from the rest of the medullary pyramid, and the sloughed tissue passes through the collecting system — sometimes causing ureteric obstruction and renal colic as it does so.
RPN is not a single disease — it is a common pathological endpoint of several distinct conditions that all cause medullary ischaemia through different mechanisms. The mnemonic POSTCARDS is used clinically to remember the important causes: Pyelonephritis (severe, especially in diabetics), Obstruction, Sickle cell disease and trait, Tuberculosis, Cirrhosis of the liver, Analgesics (NSAIDs — the most important cause in India), Renal vein thrombosis, Diabetes mellitus, and Sjögren's syndrome. In India, diabetes with associated pyelonephritis and NSAID use are the two most clinically important causes.
Causes and mechanisms
| Cause | Mechanism | Indian prevalence | Clinical pattern |
|---|---|---|---|
| Diabetes mellitus | Diabetic microangiopathy reduces medullary blood flow | High — diabetes epidemic in India | Often bilateral · Associated with recurrent UTIs · Glycaemic control reduces risk |
| NSAIDs / Analgesic nephropathy | Prostaglandin inhibition removes protective vasodilation of medullary vasa recta | Very high — OTC NSAID use widespread in India | Bilateral · Chronic, progressive · Associated with chronic interstitial nephritis · See KIMS Analgesic Nephropathy page |
| Sickle cell disease | Sickling in vasa recta causes medullary infarction | Significant in Telangana and Andhra Pradesh | Bilateral · Haematuria prominent · Occurs even in HbSC and sickle trait |
| Obstructive uropathy | Increased intrarenal pressure compresses medullary vasa recta | Common | Often unilateral (ipsilateral to the obstruction) · Resolves when obstruction is relieved |
| Severe pyelonephritis | Bacterial toxins and inflammatory mediators reduce medullary perfusion | Common in diabetics | Usually unilateral (infected side) · Associated with fever and sepsis |
| TB | Direct granulomatous destruction of papillary tissue | Important in India | Often unilateral · Chronic presentation · See KIMS GUTB page |
Clinical presentation
How papillary necrosis presents clinically
Haematuria — gross or microscopic, from bleeding at the site of papillary separation. Often the first clinical sign. In sickle cell disease, haematuria from RPN can be massive and life-threatening.
Renal colic — as a sloughed papilla passes through the ureter, it causes obstruction and colicky loin-to-groin pain — clinically indistinguishable from stone colic. CT KUB may show a soft tissue filling defect in the ureter rather than a stone.
Recurrent UTIs — stagnant urine collects in the calyceal cavities left by sloughed papillae, providing a nidus for bacterial colonisation.
Chronic, progressive CKD — repeated episodes of papillary necrosis reduce the functional medullary mass progressively.
Incidental — chronic, asymptomatic RPN may be detected on CT KUB or IVU performed for other reasons: the characteristic ring shadows (calcification outlining the cavity left by sloughed papillae) or filling defects in the calyces are pathognomonic.
Diagnosis at KIMS
CT KUB and CT urogram
The most sensitive investigation. On the excretory phase CT urogram, sloughed papillae appear as filling defects within the calyces (the cavity left by the papilla fills with contrast). In chronic cases: ring shadows (calcification of necrotic papillary tissue outlining the papillary cavity). The 'ball in calyx' sign — a partially detached papilla outlined by contrast on both sides. In the ureter: a sloughed papilla appears as a soft tissue filling defect without the dense calcium of a stone.
Intravenous urogram (IVU)
Historically the gold standard imaging investigation for RPN — the papillary cavities and ring shadows are dramatically demonstrated. Still used where CT is not available or contrast CT is contraindicated.
Urine culture, AFB, and CBNAAT
For infectious causes (pyelonephritis, TB).
HbS electrophoresis and sickle solubility test
For sickle cell-related RPN.
Treatment
Treat the underlying cause
This is the most important intervention — the only way to prevent further papillary necrosis is to control the underlying condition: optimise glycaemic control in diabetes, stop all NSAIDs, treat sickle cell disease with hydroxyurea, relieve urinary obstruction, treat pyelonephritis and TB, manage cirrhosis. Without addressing the cause, RPN will continue to progress regardless of symptomatic management.
Haematuria management
Mild to moderate haematuria from RPN is managed conservatively — vigorous IV hydration to maintain urine flow and prevent clot formation and retention in the ureter. For massive haematuria (from sickle cell RPN in particular): selective renal artery embolisation of the bleeding medullary artery is the nephron-sparing treatment of choice. Nephrectomy is the last resort.
Ureteric obstruction from sloughed papilla
Ureteroscopy or JJ stent insertion to relieve obstruction from a sloughed papilla in the ureter. The papillary tissue can often be retrieved or fragmented endoscopically.
Renal replacement therapy
For the progressive CKD from cumulative papillary destruction and cortical scarring — ACE inhibitors for CKD protection, transplant for ESRD.
Book a Nephrology Assessment for Papillary Necrosis at KIMS
Frequently Asked Questions — Papillary Necrosis
Renal papillary necrosis results from ischaemic death of the renal papillary tissue — caused by any condition that reduces medullary blood flow. In India, the most common causes are: diabetes mellitus (diabetic microangiopathy reduces vasa recta flow, particularly during episodes of pyelonephritis), NSAIDs and analgesic combinations (prostaglandin inhibition removes the protective vasodilation of the medullary capillaries), and sickle cell disease and trait (sickling in the hyperosmolar, hypoxic medullary environment causes vascular occlusion). Genitourinary tuberculosis is an important cause in India — TB granulomas directly destroy papillary tissue. The POSTCARDS mnemonic covers all the causes.
Ultrasound is not sensitive for detecting early or mild papillary necrosis. In established cases, ultrasound may show: echogenic medullary pyramids (from calcification of necrotic papillary tissue), small cavities or defects at the tips of the medullary pyramids, and irregular calyceal outlines from the absent papillae. CT urogram — particularly the excretory phase — is the definitive imaging investigation, showing the characteristic ring shadows, ball-in-calyx appearances, and calyceal filling defects that pathognomically confirm RPN. Plain X-ray may show medullary calcification in chronic cases.
The necrosed papillary tissue itself is permanently destroyed — it does not regenerate. However, stopping the underlying cause (discontinuing NSAIDs, optimising glycaemic control, treating TB) halts further papillary necrosis and prevents additional nephron loss. Early, mild papillary necrosis with adequate remaining papillary tissue may allow preservation of kidney function for decades. Advanced bilateral papillary necrosis — where most or all of the papillary tissue has been destroyed — produces a severe concentrating defect, polyuria, and eventual CKD. The best outcome is achieved by removing the cause before extensive bilateral necrosis has occurred.
Yes — a sloughed papilla passing through the ureter causes renal colic and obstruction identical in character to stone colic, and the patient and referring clinician may assume it is a stone. On non-contrast CT KUB (the standard first-line investigation for renal colic), a sloughed papilla appears as a soft tissue density filling defect in the ureter — without the high density (bright white, 200–400 HU) of calcium-containing stones. A CT KUB showing a ureteric filling defect that is soft-tissue density rather than calcium dense should prompt a contrast CT urogram to characterise the defect (sloughed papilla, tumour, or clot) rather than assuming it is a stone.
KIMS Secunderabad — Dr. V. S. Reddy (Senior Consultant Nephrologist), CT urogram for papillary necrosis diagnosis, underlying cause identification and treatment (NSAID cessation, diabetic optimisation, sickle cell management, TB treatment), selective renal artery embolisation for massive haematuria, ureteroscopy and JJ stenting for papillary obstruction, CKD management, transplant evaluation for ESRD. NABH and NABL accredited. Call 040-4488-5000.