Dynamics of the ureterovesical junction: its resistance to upper urinary tract outflow in pigs

In pigs, upper urinary tract outflow resistance at the ureterovesical junction (UVJ) has been investigated before and after changes of capacity and compliance of the bladder with ureterovesical perfusion pressure (UV-PP) measurements and cystometry (PB). Changes of UV-PP approximately paralleled changes of PB during volume changes and compression of the bladder, and during detrusor activity. Exceptions were: detrusor activity in all bladders, being nondistended, during which UV-PP always increased more than PB; and low and high compliant, and small capacity bladders in which UV-PP may change more than PB under all conditions once these bladders are so far filled that they are distended. From these findings and UVJ anatomy it is concluded that, besides intravesical pressure, anatomical factors and forces in the bladder wall also may determine upper urinary tract outflow resistance. The clinical implications are discussed.