26th June 2023

Chronic tubulointerstitial nephritis

Definition of chronic tubulointerstitial nephritis (CTIN)

In chronic tubulointerstitial nephritis there is scarring of the tubulointerstitium, characterised by tubular atrophy (defined as reduction in tubular diameter of more than fifty percent), and interstitial fibrosis. It presents as slowly progressive renal impairment and is normally asymptomatic, however, proteinuria, polyuria or nocturia may be present.

Causes of CTIN

• Drugs
  • Analgesics –paracetamol, aspirin, NSAIDs
  • Lithium
  • Calcineurin inhibitors – ciclosporin, tacrolimus
  • Cisplatin
• Metabolic
  • Hypercalcaemia
  • Hypokalaemia
  • Hyperuricaemia (gout)
• Chronic pyelonephritis
• Heavy metals
  • Lead, cadmium, gold, mercury
• Autoimmune
  • Sarcoidosis
  • Sjogren’s syndrome
  • Systemic lupus erythematosus (more associated with glomerular disease)
• Haematological/Malignancy
  • Sickle cell disease
  • Multiple myeloma
  • Lymphoproliferative disorders
• Structural
  • Reflux nephropathy
  • Obstructive nephropathy (most often secondary to renal calculus)
• Congenital
  • Polycystic kidney disease
  • Cystinosis
  • Dent disease
• Balkan endemic nephropathy – long-term exposure to aristolochic acid found in cereal products in Balkan areas plus a genetic predisposition
• Aristolochic acid nephropathy (found in herbal remedies)
• Progressive glomerular diseases (glomerulonephritides, diabetic nephropathy, hypertensive nephropathy).

Diagnosis

The diagnosis of chronic tubulointerstitial nephritis is normally a clinical diagnosis based on the possible underlying cause, the presenting features, examination findings and clinical judgement; however, there are some clinical tests to aid in the diagnosis.

• Urinalysis – proteinuria, leukocytes, occasional white cell casts
• Blood tests
  • Evidence of normocytic anemia is often disproportionate compared to the extent of the reduction in the glomerular filtration rate caused by reduced production of erythropoietin.
  • Increased urea and creatinine
  • Abnormal electrolytes – hypokalaemia, hyperkalaemia, hypocalcaemia, hypomagnesaemia, hyponatraemia
  • Metabolic acidosis – normal anion gap metabolic acidosis secondary to renal tubular acidosis
• Ultrasonography
  • Small kidney, increased echogenicity, scarring

Management

• Treat the underlying cause – for example, stop offending drug if this is the cause.
• Manage CKD – patient may need to undergo dialysis or renal transplant.