Transmission electron microscopy of urinary sediment in human acute renal failure

Urinary sediments from 31 patients with acute tubular necrosis (ATN) were studied using transmission electron microscopy (TEM). Variable quantities of renal tubule cells (RTCs), characterized by abundant cytoplasmic organelles, were a consistent finding in these sediments. TEM analyses of well-preserved RTCs permitted identification of their nephron segment(s) of origin. On the basis of the severity of ultrastructural changes observed, the sediments were divided into three types. Type I (N = 11) and II (N = 8) consisted of homogeneous populations of severely and mildly affected RTCs, respectively, while Type III (N = 12) sediments were composed of a heterogeneous population of variably affected cells. A correlation was found between the sediment type and the severity of the clinical illness. Of the 11 patients with Type I sediments, only two survived and they required chronic dialysis support. In contrast, seven of eight patients exhibiting Type II sediments survived, with only one requiring temporary dialysis therapy. Patients with Type III sediments had an intermediate course, with six of seven survivors regaining sufficient renal function to remain off dialysis over a 3-month period of observation. Our study suggests that TEM of urinary sediment can provide a useful non-invasive means of studying patients with ATN.