"The distal nephron index": a measure of obstructive nephropathy in experimental hydronephrosis

An experimental model is described in rabbits where chronic partial ureteric occlusion and permanent renal pelvic cannulation were performed. For periods of up to three months, parameters of distal nephron function were measured repeatedly and pressure-flow studies performed. Fractional water clearance, free water clearance/GFR ratio and the relative intrapelvic pressure (IPP) on perfusion were increased (P less than 0.01) as a result of partial ureteric occlusion. A new parameter, "the distal nephron index", is described which is also raised in obstruction (P less than 0.01) and which exhibits a linear correlation with relative IPP (r = +0.40; P less than 0.05) not demonstrated by the other distal nephron function measurements. The implications of this relationship in the assessment of upper tract dilatation are discussed.