Bladder content and residual urine in renal transplant patients: measurement using ultrasonography and relevance to urinary tract infection

Abstract

Since the incidence of urinary tract infection after renal transplantation is high, and residual urine after voiding may be associated with urinary tract infection, the reliability of ultrasonographic determination of bladder content and residual urine in renal transplant recipients was investigated. Both bladder content and residual urine, calculated by the formula 0.6 × length × width × depth of the bladder (in cm), correlated closely (r>0.9, P<0.001) to the measured volumes of urine obtained by voiding and catheterization. We conclude that ultrasonography is a reliable method for determining bladder content and residual urine in renal transplant recipients. Out of 44 patients, 4 exhibited residual urine of more than 10 cm3; 25 of the 44 patients (57%) had one or more urinary tract infections within the first year of transplantation. One of the patients with residual urine had recurrent pyelonephritis and another had recurrent cystitis; the other two patients did not have any urinary tract infection at all. Since residual urine does not appear to be a frequently occurring phenomenon, it probably does not contribute to the high incidence of urinary tract infections in renal transplant recipients.