Review Note
Last Update: 12/01/2024 12:06 AM
Current Deck: State Exam::Nephrology
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Acute abacterial interstitial nephritis – etiology, pathogenesis, clinical picture, diagnosis, and
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Acute Tubulointerstitial Nephritis (ATIN)
Definition:- Kidney lesion involving interstitial inflammatory infiltrate and edema, resulting in decreased renal function.
- Typically develops over days to months.
- A frequent cause of acute kidney injury (AKI) that may lead to chronic kidney disease (CKD).
- Drugs (~70–75%):
- NSAIDs, certain antibiotics (e.g., beta-lactams, sulfonamides, fluoroquinolones), PPIs, diuretics, allopurinol, quinolones.
- Infections (~4–10%):
- Examples: Streptococci, MTB, Legionella, CMV, EBV, adenovirus.
- Autoimmune/Systemic Diseases (~10–20%):
- Examples: SLE, sarcoidosis, Sjögren’s syndrome.
- Tubulointerstitial Nephritis and Uveitis (TINU) Syndrome (<5%).
- Many patients are asymptomatic.
- Some present with non-specific symptoms of AKI:
- Nausea, vomiting, malaise.
- Other findings:
- Polyuria and nocturia (due to impaired urinary concentration and sodium reabsorption).
- Constitutional symptoms: Malaise, anorexia, arthralgias.
- Hypersensitivity manifestations: Low-grade fever, rash, eosinophilia.
- Urinary findings: Leukocyturia, microhematuria, non-nephrotic proteinuria.
- Suspect ATIN in patients with:
- Elevated serum creatinine.
- Presence of leukocyturia and systemic or hypersensitivity symptoms.
- Lab Findings:
- Blood:
- Increased serum creatinine.
- Decreased GFR.
- Eosinophilia (possible in drug-induced cases).
- Urinalysis:
- Microhematuria, non-nephrotic proteinuria.
- Characteristic urine sediment:
- RBC, WBC, and WBC casts.
- Eosinophiluria may be seen in drug-induced cases.
- Sterile pyuria (absence of bacteria on culture).
- Blood:
- Imaging:
- No diagnostic imaging findings; used to exclude other causes.
- Renal Biopsy:
- Not always necessary (e.g., if AKI occurs after drug initiation).
- Findings:
- Interstitial edema with inflammatory infiltrate (mainly T-cells).
- Additional Tests:
- Assess CBC, BUN, creatinine, and liver function tests (for drug-induced liver injury).
- Serologic tests for associated diseases:
- Anti-SSA/SSB for Sjögren’s syndrome.
- Antinuclear antibody for SLE.
- Serum IgG4 for IgG4-related disease.
- Therapy:
- Drug-Induced:
- Stop the offending agent immediately.
- Severe cases of AKI requiring dialysis:
- Perform kidney biopsy.
- Initiate glucocorticoid (GC) therapy and dialysis:
- IV Methylprednisolone: 500–1000 mg daily for 3 days.
- Follow with oral Prednisolone: 1 mg/kg daily for 2–3 weeks.
- Mild cases without the need for dialysis:
- Observe the patient for 3–7 days after stopping the offending agent.
- If kidney function has not stabilized:
- Perform kidney biopsy.
- Start GC therapy:
- Oral Prednisolone: 1 mg/kg daily for 2–3 weeks.
- NSAID-induced AIN generally responds poorly to GC therapy.
- Drug-Induced:
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