Urinary tract anomalies and dysfunctional voiding: a spectrum dictated by the influence of amniotic pressure upon fetal urodynamics

The etiologic basis of urinary tract anomalies and dysfunctional voiding la rgely remain unknown. However, the travel of urine from renal pelvis into t he amniotic cavity under the pressures exerted by amniotic fluid satisfacto rily explains the etiologic basis. Amniotic pressure is affected by the cha nges in maternal intraabdominal pressure. The intraabdominal pressure of th e fetus is also dictated by the amniotic pressure. Amniotic pressure compre sses the urethra throughout the length, and may increase both bladder leak point pressure and urethral resistance. Furthermore, the urine is propelled against amniotic pressure. These factors closely simulate outflow obstruct ion. Since the pressure within the bladder with minimal urine content refle cts the intraabdominal pressure, intravesical pressure is also elevated dur ing fetal life. Additionally, elevated intravesical pressures impair ureter al drainage. The compressive effect exerted by fetal intraabdominal pressur e upon ureters, further elevate the pressure within the renal pelvis. While forwarding the urine against these pressures may result in anomalies of th e urinary tract, the increased work load of the detrusor may act as a state of injury that forms the basis of dysfunctional voiding. (C) 2000 Harcourt Publishers Ltd.