  Some simple mathematical formulae to calculate the volumes of proximal
pyeloureteral reflexive systems are presented, and the results are compared to
bladder capacity values. Using the results of the calculi, the author discusses
possible implications of severe urinary sequestration in the pyeloureteral
systems. Using geometrical and topological approximations we calculate the
volumes of ureters and renal pelvises, applying in vivo measurements obtained
from conventional ultrasound, retrograde cystourethrograms and topographic
anatomic references. Approximations use 2 decimals and assumed $\pi$ value was
3.14. Ureteral and pyelic volumes are calculated, respectively, from the
mathematical formula for the cylinder and cone volumes. Dolicomegaureter are
compensated using proportional calculi. Bladder volumes are estimated from
conventional formulae. Proximal urinary sequestration is compared between
infants and older children with VUR. Mechanisms of direct induction of bladder
urodynamic failure from VUR are suggested. Sequestration of urine in the ureter
and renal pelvis can be estimated from mathematical formulae in patients with
VUR. The values used derive from ultrasound examinations, CUM and topographical
anatomical references. Primary VUR can determine urodynamic problems. Urine
sequestration in the proximal urinary system is worse in infants than in older
children.
