Kidney Biopsy Case: AKI

A 54 year old man was referred to the Nephrology service due to AKI after presenting with lethargy and severe thirst. He had a long history of pulmonary and hepatic sarcoidosis which had been quiescent for some time. He likely had some baseline mild CKD with a serum creatinine of 1.3 mg/dl and 0.5 g/day proteinuria. His medications were unremarkable except for a calcium and vitamin D preparation which he had been taking for several months. His creatinine was 4.0 mg/dL and calcium was 13.5 mg/dl on presentation. He was volume resuscitated, treated for his hypercalcemia and proceeded to renal biopsy. Low power light microscopy is below which reveals an interstitial infiltrate with moderate fibrosis and some sclerosed glomeruli.

Higher power demonstrates multiple non-caseating granulomas. The granulomas consist of amorphous reddish material as well as multi-nucleated giant cells (below; top left and right of center).

Another example below of a granuloma (on the left of the panel) in a sick looking tubulo-interstitium.

The diagnosis was sarcoidosis-related granulomatous interstitial nephritis. He was commenced on high dose oral steroids and his renal function settled back down to normal over several weeks. Sarcoidosis does uncommonly affect the kidneys and is a major differential for granulomatous interstitial nephritis (see previous post). A teaching point for this case is not to presume the hypercalcemia is all iatrogenic. The high calcium points to sarcoid activity which was demonstrated nicely on the biopsy.