Related Subjects:
|Metabolic acidosis
|Lactic acidosis
|Acute Kidney Injury (AKI) / Acute Renal Failure
|Renal/Kidney Physiology
|Chronic Kidney Disease (CKD)
|Anaemia in Chronic Kidney Disease
|Analgesic Nephropathy
|Medullary Sponge kidney
|IgA Nephropathy (Berger's disease)
|HIV associated nephropathy (HIVAN)
|Balkan endemic nephropathy (BEN)
|Autosomal Dominant Polycystic kidney disease
About 🩺
- Chronic Interstitial Nephritis (CIN): A progressive kidney disease involving long-standing inflammation and fibrosis of the renal interstitium.
- Often evolves from untreated or recurrent Acute Interstitial Nephritis (AIN).
- Common final pathway → Chronic Kidney Disease (CKD).
- Classic association: prolonged use of NSAIDs ⚠️ (“analgesic nephropathy”).
Aetiology 🔬
- Chronic inflammation and fibrosis of the renal tubules and interstitium.
- Loss of tubular function → impaired urine concentration and progressive renal failure.
Causes 📌
- Drug-induced 💊: NSAIDs, lithium, ciclosporin, tacrolimus, tenofovir, antibiotics (AIN history).
- Inherited/Genetic 🧬: Medullary cystic kidney disease, Wilson’s disease.
- Autoimmune 🛡️: Sarcoidosis, SLE, Sjögren’s syndrome, amyloidosis.
- Infectious/Environmental 🌍: Aristolochia (“Chinese herbal nephropathy”), Balkan endemic nephropathy, lead exposure.
- Other: Chronic transplant rejection, vesicoureteric reflux, sickle cell disease, renal dysplasia.
- Miscellaneous 🍄: Cortinarius mushroom toxicity (Scotland/Scandinavia), collecting system tumours, some GN.
Clinical Features 👀
- Insidious onset of chronic renal failure (fatigue, anorexia, pruritus, weight loss).
- Hypertension is common.
- Polyuria & Nocturia 💧🌙: Early sign due to tubular dysfunction (salt-losing nephropathy).
- Small, scarred kidneys on imaging.
Investigations 🧪
- FBC & ESR: ESR may be elevated due to chronic inflammation.
- U&E: Raised creatinine, hyperkalaemia; check Ca²⁺, phosphate, ALP for bone disease.
- Urinalysis: Mild proteinuria, sterile pyuria (WBCs without infection).
- Urine concentration test: Dilute urine (loss of concentrating ability).
- Renal Tubular Acidosis (RTA): Common in late stages.
- USS: Shows small, atrophic kidneys.
- Renal Biopsy (gold standard): Interstitial fibrosis, tubular atrophy, lymphocyte/plasma cell infiltration.
Management 🩹
- Remove/Treat Cause: Stop nephrotoxins (e.g., NSAIDs, lithium) or treat underlying autoimmune/infective condition.
- Supportive CKD Care:
- Correct metabolic acidosis (oral bicarbonate).
- Manage hyperkalaemia.
- Fluid and electrolyte replacement as needed.
- CKD Management: BP control (ACEi/ARB), lipid optimisation, smoking cessation.
- Renal Replacement Therapy (RRT): Dialysis or transplant in advanced disease.
Key Clinical Pearls ✨
- Think CIN in a patient with progressive CKD + history of long-term NSAID/lithium use.
- Polyuria/nocturia can precede renal failure → clue to tubular dysfunction.
- Biopsy confirms diagnosis but often not needed once advanced scarring is present.
