Tubulointerstitial Nephritis

Overview – Tubulointerstitial Nephritis

Tubulointerstitial nephritis is a condition involving inflammation of the renal tubules and interstitial tissue, often resulting in acute kidney injury or chronic renal impairment. It may be caused by drugs, infections, autoimmune diseases, or secondary to other renal pathologies. Drug-induced hypersensitivity reactions are a common aetiology in hospital settings. Clinical presentation varies from asymptomatic biochemical abnormalities to polyuria, fever, rash, and progressive renal failure.

Definition

• Tubulointerstitial nephritis is characterised by inflammatory infiltration and structural damage to the renal tubules and interstitium.
• It can be acute or chronic in onset, and often leads to impaired renal function.

Aetiology

Primary Causes (Drug/Toxin-Induced – Often Allergic Reactions)

• Antibiotics:
  • Penicillin, Cephalosporins, Sulfa drugs, Rifampicin, Ciprofloxacin
• Diuretics:
  • Frusemide
• NSAIDs
• Chemotherapy agents
• Allopurinol
• Proton pump inhibitors (e.g. Omeprazole)
• Heavy metals:
  • Cadmium, Lead, Lithium

Secondary Causes

• Acute tubular necrosis
• Multiple myeloma
• Polycystic kidney disease
• Pyelonephritis
• Vesicoureteral reflux
• Sarcoidosis
• Sickle cell disease
• Sjögren’s syndrome, SLE

Pathophysiology

• Trigger (e.g. drug, infection, toxin) →
  • Leukocyte infiltration (T-cells, eosinophils)
  • Tubular epithelial damage
  • Fibrosis and degeneration of interstitial tissue
• In chronic forms:
  • Progressive fibrosis → nephron loss → chronic kidney disease
• May follow acute tubular necrosis and protein cast deposition

Clinical Features

Acute Tubulointerstitial Nephritis

• Polyuria
• Electrolyte imbalances (e.g. hyponatraemia, hypokalaemia)
• Fever, rash, arthralgia
• Dysuria or flank pain (if infective cause)

Chronic Tubulointerstitial Nephritis

• Polyuria and nocturia
• Fatigue
• Pruritus
• Nausea, anorexia
• Reduced urine concentrating ability

Investigations

• Blood tests:
  • Elevated urea and creatinine
  • Electrolyte disturbances (especially ↓ potassium, ↓ bicarbonate)
  • Metabolic acidosis
• Urinalysis:
  • Mild proteinuria
  • Pyuria or haematuria possible
• Definitive diagnosis:
  • Renal biopsy – reveals interstitial inflammation, tubular atrophy, and fibrosis

Management

• Eliminate offending agent (e.g. discontinue drug)
• Treat underlying cause if systemic condition present
• Corticosteroids may reduce inflammation and improve outcomes
• Supportive care:
  • Fluid and electrolyte balance
  • Monitor renal function
• Dialysis or transplant may be needed in advanced cases

Complications

• Acute kidney injury
• Progression to chronic kidney disease
• Electrolyte derangements (e.g. hyperkalaemia in late stages)
• End-stage renal failure (rare if treated early)

Differential Diagnosis

• Acute tubular necrosis
• Glomerulonephritis
• Pyelonephritis
• Obstructive uropathy
• Renal vasculitis

Summary – Tubulointerstitial Nephritis

Tubulointerstitial nephritis is an inflammatory kidney disorder affecting the tubules and interstitium, commonly triggered by drug reactions or systemic diseases. It may present acutely with fever, rash, and renal dysfunction, or progress chronically with fatigue and polyuria. Management involves removing the offending agent, corticosteroids, and supportive care. For a broader context, see our Renal Overview page.