Extraperitoneal paravesical spaces: CT delineation with US correlation.

The extraperitoneal space around the urinary bladder is lamellate, just like the retroperitoneal space around the kidneys. The bladder, urachus, and obliterated umbilical arteries lie within the perivesical space, surrounded by umbilicovesical fascia, analogous to the perinephric space within the renal fascia. A much larger prevesical space, analogous to the anterior pararenal space, lies anterior and lateral to the umbilicovesical fascia. Posterior to the urinary bladder, the lower uterine segment or seminal vesicles lie within the perivesical space, rather than in a separate compartment, corresponding to the posterior pararenal space. The cul-de-sac, and the inferolateral extension of its peritoneal layers as the rectovaginal or rectovesical septum, separate the posterior perivesical space from the rectum. The sectional anatomy of these spaces, and particularly their computed tomographic and ultrasound appearances, were noted in normal anatomic sections, patients with extraperitoneal fluid collections, and a cadaver into which fluid was injected.