On the Cover

A 55-year-old man was seen in consultation for AKI. His history was notable for recent partial liver resection for metastatic colorectal cancer. Pertinent exam findings included hypotension, icterus, hyperbilirubinemia, and change in serum creatinine from 1.0 mg/dL to 2.7 mg/dL. Urine microscopy revealed several leucine crystal casts such as the one demonstrated on the left side of the cover image. Subsequent kidney biopsy demonstrated several tubular casts with polarizing round crystals with a “Maltese cross” appearance (see right side of cover image). Leucine crystals are often seen in the urine of patients with severe liver disease. Loss of enzymatic function of the branched-chain α-ketoacid decarboxylase complex in the liver reduces the metabolism of leucine and elevates serum levels. Little is known about whether the crystals are toxic to nephrons. They are not believed to contribute to loss of kidney function. Yet, in this patient, casts with leucine crystals were found in the renal tubules and in the urine. It raises the concern that intra-tubular obstruction or direct tubular toxicity may lead to the development of AKI. (Images and text provided by Koyal Jain, MD and Abhijit V. Kshirsagar, MD, MPH, Division of Nephrology and Hypertension, University of North Carolina Kidney Center, Chapel Hill, North Carolina)