Morphological dynamics of ureteral transport. I. Shape and volume of constituent urine fractions.

Ureteral transport was studied in 50 urinary systems by urography with video recording in the upright and recumbent positions using low-osmolality and high-osmolality contrast media. Morphometry and volumetry were applied to right urinary systems in which the urine-filled segments had a circular cross section at maximum peristaltic distension. The filling of the lumbar segment was composed of four fractions, each entering that segment by a specific mechanism: 1) the residual urine left behind by the preceding contraction ring, 2) the postcontraction injection from the pyelocalyceal system, 3) the extraperistaltic flow, and 4) the peristaltic injection produced by the pyelocalyceal contraction rings. The variations in the precontraction filling by fractions 1-3 and in the volume of fraction 4 gave rise to four types of transport. The junction between the lumbar and pelvic segments constituted a constant point of resistance to flow that prevented fractions 1-3 from entering the pelvic segment, the peristaltic injection into that segment being determined solely by the resistance at the junction and the volume of the bolus in the lumbar segment. Extraperistaltic flow to the bladder constituted a separate type of transport.