B77 Tubulointerstitial nephritis

Question 1

What are the types of Tubulointerstitial nephritis

Answer 1

Usually TIN is caused by bacterial infection and the renal pelvis is prominently involved, as a part of pyelonephritis.

Interstitial nephritis is a term reserved for non-bacterial inflammation, even though it still involves both the tubules and interstitium

• includes Acute Interstitial Nephritis
• and Analgesic Papillary Necrosis

In either case, the glomeruli are usually not involved or only become involved late in the course of severe cases.

Question 2

What are the causes of interstitial nephritis?

Answer 2

Drug-induced hypersensitivity reaction involving the interstitium and tubules

• NSAIDs, penicillin, and diuretics

Question 3

What is the histology/morphology of Acute Interstitial Nephritis?

Answer 3

Hypersensitivty reaction within the tubules and interstitium,

• Interstitial and tubular edema
• Lymphocytes, macrophages, mononuclear cells, neutrophils and especially
• Eosinophils
• Normal glomeruli - (except in some cases of NSAID where there is foot process efacement and nephrosis)

Question 4

What is the clinical course of acute interstitial nephritis?

Answer 4

Requires a latent period after exposure to the drug. Usually about 2 weeks.

This is consistent with a hypersensitivity reaction ,as it takes times for the IgE to be syntehsized and accumulated on the eosinophils.

Symptoms:

• fever
• rash (in 25%)
• oliguria/anuria
• azotemia
• no proteinuria
• leukocyturia and eosinophiluria

Resolves with drug cessation, but can be severe enough to cause potential papillary necrosis first.

Question 5

Pathogenesis of analgesic nephritis

Answer 5

Causes chronic interstitial nephritis and often papillary necrosis.