The accuracy of a catheterized residual urine

Residual urine is important in the evaluation of the urological patient. The gold standard to obtain this information is a catheterized specimen. We examined the accuracy of a catheterized value to ascertain whether the bladder was emptied completely. After the bladder was catheterized 10 ml. radiocontrast material were instilled into the bladder to allow radiographic documentation of complete evacuation. We found that 26 per cent of 515 patients evaluated had residual urine after routine attempts were made to evacuate the bladder fully. We conclude that a single residual urine estimate may be inaccurate and one should not always base therapeutic decisions upon any single such measurement.