Abnormal renal physiology Isothenuria Inability of the kidneys to produce either concentrated or dilute urine. Isothenuria is seen in the final stages of renal failure. It reflects rapid flushing of fluid through the tubules in renal failure as the number of functioning nephrons decreases; the normal concentrating (particularly) and diluting mechanisms of the kidney do not have time to function. The consequence is that the specific gravity of the urine becomes approximately the same as that of the glomerular filtrate. UMLS:C4022665