Obstructive disorder, it causes accumulation of urine in the bladder, which will have a back flow to the kidney, now renal pelvix already has the filtered urine and 5-8 ml. with the accumulation of urine from the bladder adn the kidney itself, there will dilatation of the renal pelvix, aausing the unilateral or bilateral kidney enlargement. that will cause barotrauma. this leads to damage to the reanl tissues, vessles and the nerves leading to hypertrophy that damages the neuphron. causing acute renal failure.