The influence of bladder fullness on upper urinary tract dimensions and renal excretory function

Nearly full bladders (375 ml.) produced significantly greater dimensions of the renal calices, pelves and ureters on excretory urograms compared to nearly empty bladders. These dimensions were frequently to the point of being considered pathological dilatations. On planimetry the urographic areas of the pelviocaliceal systems decreased by 43 per cent on the right side and 38 per cent on the left side when the nearly full bladder was compared to the nearly empty bladder in 10 patients. Renal excretory function also was affected by nearly full bladders. Urea clearances after 1 hour were 24 per cent lower and creatinine clearances were 9 per cent lower when starting with a nearly full bladder as compared to starting with an empty bladder. The implications of these findings are of potential significance with respect to 1) interpretation of excretory urograms and 2) chronic urine holding in patients with recurrent urinary tract infections, impaired renal function and/or urolithiasis.