Tubulointerstitial Nephritis

Abstract

Damage in the renal tubular cells associated with inflammation in the spaces between the tubules is called tubulointerstitial nephritis, which is classified into acute and chronic interstitial nephritis. In acute interstitial nephritis (AIN), there is a rapid decline in renal function that is associated with pathologic findings of lymphocyte and monocyte infiltrates with varying composition of eosinophils, plasma cells and neutrophils, and interstitial edema with no glomerular or vascular involvement. It is commonly drug-induced and antibiotics account for 30-49% of the cases, but it is also caused by infections and immunologic disorders, including tubulointerstitial nephritis with uveitis (TINU) syndrome and immunoglobulins G4 (IgG4)-related disease. The classic clinical triad of fever, rash and eosinophilia is not always manifested in AIN. The diagnosis is confirmed with a kidney biopsy, which is not often performed because as the drug is discontinued, kidney recovery usually ensues. Laboratory test shows an elevated serum creatinine that is suggestive of acute kidney injury (AKI). Urine microscopy can be helpful when there is a high suspicion for AIN, but absence of urinary findings does not exclude the diagnosis. Renal ultrasound may show enlarged kidneys, but it is not diagnostic. Prognosis is good if AIN is recognized early and if the offending drug is promptly discontinued. In chronic interstitial nephritis (CIN), there is a gradual decline in renal function that is associated with nonspecific pathologic findings of tubulointerstitial fibrosis and atrophy. Because of its chronicity, the glomerular and vascular components can eventually be affected, which results in the progression of chronic kidney disease (CKD) and may lead to end-stage renal disease (ESRD). Drugs, nephrotoxins, and immune-mediated disorders are among those that cause CIN. Clinical manifestations vary depending on the etiology. Laboratory test shows an elevated serum creatinine that is suggestive of chronic kidney injury (CKD). Renal ultrasound may show small kidneys. Prognosis depends on the stage of chronic kidney disease (CKD) when CIN is diagnosed and on the underlying cause of CIN.