Urinary Muramidase and Renal Disease

Abstract

Muramidase appeared in the urine of 80 healthy adults and 51 patients with acute or chronic leukemia, all without clinical evidence of renal disease, only when the serum muramidase concentration exceeded approximately three times the control level, demonstrating an apparent renal threshold for excretion of the enzyme. Similar determinations in 73 patients with renal disease or conditions known to affect the kidney in whom histologic examination of kidney tissue was also made indicated muramidase activity in the urine that correlated well with histologic evidence of damage to renal tubules. These observations are consistent with the suggestion that the appearance of the enzyme in the urine is due to reduced tubular reabsorption of filtered enzyme from the urine. Measurement of urinary muramidase may be a useful diagnostic index of renal tubular injury when serum values do not exceed the renal threshold.