Chapter 96 - Acute Tubulointerstitial Nephritis

Abstract

Acute interstitial nephritis (AIN) is the cause of acute kidney injury in about up to 20% of cases that undergo a kidney biopsy. AIN is a histological diagnosis character­ized by presence of inflammatory cells in the kidney interstitium and infiltration of these cells into the tubules (“tubulitis”). While AIN is treatable, a delay in diagnosis leads to permanent loss of kidney function as ongoing inflammation in AIN can lead to fibrosis. Medications are the cause of AIN in over 70% cases. Proton pump inhibitors, antibiotics, nonsteroidal antiinflammatory drugs, and, recently, immune checkpoint inhibitors are the common classes of medications causing AIN, although over 100 medications have been reportedly associated with AIN. Autoimmune diseases such as sarcoidosis, Sjogren syndrome, and tubulointerstitial nephritis with uveitis syndrome (TINU) are the second most common cause of AIN. There is no typical clinical feature, blood or urine test, or imaging test that can reliably diagnose AIN. Most patients present with acute or subacute loss of kidney function with minimal abnormalities on urine sediment and often mild pyuria and proteinuria. A kidney biopsy is required to establish diagnosis. The mainstay of AIN treatment is early identification and removal of culprit medication followed by corticosteroid therapy in selected patients.