Continent urinary diversion (Mitrofanoff principle). Physical mechanisms and urodynamic explanation of continence

To analyze the urodynamic parameters and the mechanisms of continence of Mitrofanoff urinary diversion. Urodynamic assessment was performed via the stoma in 11 patients with continent urinary diversion according to the Mitrofanoff principle. The mean age of the patients at the time of the operation was 29 years. The appendix, used as conduit in all cases, was anastomosed to the skin of the right iliac fossa. Ileocystoplasty was performed in 10 patients. The urodynamic assessment was performed after a mean follow-up of seven years (range: five to 12 years). Reservoir pressures after filling did not exceed 20 cm H2O in nine cases. Uninhibited contractions were recorded in two patients with an enlarged bladder with pressures not exceeding 30 cm H2O. Appendix pressures during filling were always higher than bladder pressures. The mean pressure measured at the end of filling was 75 cm H2O (range: 45 to 90 cm H2O). After the Valsalva maneuver, these pressures were between 80 and 150 cm H2O with good transmission. The mean conduit closing pressure was 70 cm H2O (range: 40 to 90 cm H2O). The mean functional length of the conduit was 5 cm (range: 2.6 to 7.2 cm). The Mitrofanoff diversion is mainly characterized by the high intraluminal pressure in the continent conduit. A low bladder pressure is essential to maintain a perfectly continent diversion.