Renal glycosuria in patients with the nephrotic syndrome

Transient or persistent renal glycosuria may occur in patients with the nephrotic syndrome. In an attempt to elucidate its mechanism, glucose titration experiments were performed in 20 nephrotic patients. The type A titration curve was found in one and type B in four patients with severe organic changes and low glomerular filtration rate. The remaining subjects displayed a particular type of curve (type C) characterized by a low point of splay but an otherwise almost physiological tracing. In type B and C patients the maximal rate of reabsorption per ml glomerular filtrate (TmG/GFR) was significantly increased and correlated inversely with the filtration fraction. In these patients the point of splay correlated with the glomerular filtration rate and the sodium clearance, but not with the plasma albumin concentration or the rate of proteinuria. These observations suggest that type A was due to diffuse tubular atrophy, and type B to increased nephron heterogeneity resulting from chronic organic changes. Type C was presumably caused by a potentially reversible alteration of the late proximal or distal glucose transport related to the nephrotic syndrome itself.