10. Chronic interstitial nephritis

Question 1

What is chronic tubulointerstitial disease?

Answer 1

• It encompasses a variety of disorders sharing similar histological appearance on biopsy
  
  • The tubulointerstitial compartment is extensively fibrosed with lymphocytic infiltrate in scarred areas
  • Tubules are often dilated and atrophic
  • Glomeruli are spared
• Chronic tubulointerstitial disease is a diagnosis itself
  
  • Drug-induced AIN may progress to it if untreated
  • It is part of CKD

Question 2

What are the causes of chronic tubulointerstitial disease?

Answer 2

• Drugs (NSAIDs, caffein, codein, acetaminophen)
• Autoimmune disorder (SLE, Sjögren’s syndrome, sarcoidosis)
• Metabolic causes (Chronic hypokalemia in anorexia nervosa for example)
• Heavy metals
• Reflux nephropathy
• Balkan endemic and chinese herbal nephropathies
• Urate nephropathy (tumor lysis syndrome, Gout)
• Radiation nephropathy
• Chronic infection (TB)

Question 3

What are the clinical features of chronic tubulointerstitial disease?

Answer 3

• Slowly progressing renal failure with insidious onset and usually mild symptoms and signs:
  
  • Impaired urinary concentration (nocturia, polyuria)
  • LMW tubular proteinuria
  • Inactive urinary sediment composed of leukocytes and WBC casts
  • Renal anemia
  • Osteomalacia
  • Glucosuria (Fanconi syndrome) and renal tubular acidosis
  • Often normal BP
  • Small, symmetrical kidneys on US (except with reflux nephropathy, which is asymmetric)

Question 4

How do we manage chronic tubulointerstitial disease?

Answer 4

• Management of CKD
• Control of BP
• Elimination of inciting agent