Complex tubular flow in the acutely obstructed kidney.

Application of Poiseuille's Law of Laminar Flow to the renal tubules using published figures for their dimensions permits estimates of the pressure differences required to produce flow through the different types of nephron and their different segments. In the obstructive situation the pressures, flows and osmolar relationships (particularly those associated with the concentration mechanism) are greatly altered. It may be predicted that this, together with a greater osmotic leak from the distal convoluted tubules of nephrons arising from peripheral glomeruli, will lead to complex (i.e. mixed forward and retrograde) flow in the respective distal convoluted and collecting tubules. Such an hypothesis would explain some hitherto ill-understood phenomena, including resorption from the obstructed renal pelvis, some aspects of ascending renal infections, reflux nephropathy and chronic obstructive disease, and certain radiological appearances in acute ureteric obstruction in man.