Influence of serum albumin on renal function in nephrotic syndrome

 Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), determined by the clearances of inulin and para-aminohippuric acid, were evaluated in 119 children with different types of nephrotic syndrome and in different stages: the nephrotic stage (serum albumin <25 g/l), recovery stage (25–35 g/l), and remission (>35 g/l). GFR in the nephrotic stage was significantly lower than in remission and in controls, and was lowest at onset of the disease (84±6, 111±4, and 119±2 ml/min per 1.73 m²). ERPF was higher in the nephrotic stage than in recovery, especially in children with histological lesions. Thus the filtration fraction (FF) was greatly decreased in the nephrotic stage. In patients investigated both in the nephrotic and the remission phase, GFR and FF increased significantly. There was a direct correlation between the serum albumin concentration and FF and an inverse correlation between mean arterial pressure (MAP) and GFR and FF in all patients, a direct correlation between the serum albumin concentration and GFR in minimal change nephrotic syndrome patients, and an inverse correlation between ERPF and serum albumin in children with histological lesions. In conclusion, GFR and FF were decreased and ERPF increased in the nephrotic stage, normalizing in remission. The low GFR in the nephrotic stage was thus not dependent on hypoperfusion. We suggest that the low GFR is dependent on a very low ultrafiltration coefficient. The direct correlation between GFR and serum albumin and the indirect correlation between GFR and MAP suggest compensatory mechanisms that increase the ultrafiltration pressure to counteract the severely reduced ultrafiltration coefficient. Received: 19 November 1997 / Revised: 11 April 1998 / Accepted: 14 April 1998