Mechanical factors and tissue stresses in chronic hydronephrosis.

From 21 dogs kidneys removed at 0, 1, 2, and 4 weeks after ureteral blockage we found the expected early increase, than subsequent decrease, in pressure and the expected continuing increase in volume and thinning of the walls. However the calculated wall stress builds up continuously with time as does the elastic modulus of the wall. By the 4th week, the wall material has become approximately 3 times as resistant to stretch as the normal ureter.