This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
In children the bladder is practically an abdominal organ; when it is empty the peritoneum sinks about to the level of the top of the symphysis, but when distended it rises from 2.5 to 6.25 cm. (1 to 2 1/2 in.) above. In the adult the top of the bladder is held to the top of the symphysis by the urachus, and as it becomes empty the upper surface descends until a curved line is formed from the top of the symphysis downward and backward to the rectovesical pouch, which is opposite the insertion of the ureters and corresponds to a point just below the extremities of the seminal vesicles and 2.5 to 4 cm. (1 to 1 1/2 in.) above the posterior border of the prostate.
Fig. 451. - The bladder in its empty and distended state. When distended the peritoneal reflection en the anterior abdominal wall is seen to be raised. The posterior or rectovesical reflection remains nearly or quite unchanged.
As held by Greig Smith, the main factor in raising the peritoneum from the front of the bladder above the upper edge of the symphysis is its distention, and 450 to 600 c.c. (15 to 20 oz.) will raise the fold 2.5 to 5 cm. (1 to 2 in.).
When the body is placed in the Trendelenburg posture the contents of the bladder gravitate toward the diaphragm, and therefore push the peritoneum up or away from the upper border of the symphysis: hence this position is usually employed when the bladder is to be opened for operative purposes. The use of a rubber bag in the rectum distended with water has been found to raise the peritoneal folds so little that its use has been abandoned in favor of the Trendelenburg posture.
Posteriorly the rectovesical pouch is approximately 8.75 cm. (3 1/2 in.) from the anus, but it may be as little as 7.5 cm. (3 in.), or as much as 10 cm. (4 in.). As has already been stated the attachment of the rectovesical pouch to the rectum is so firm that whether the bladder is distended or collapsed its distance from the prostate is but little altered. It does not change its position markedly as does the peritoneum above the pubes. Waldeyer (Joessel and Waldeyer, Topog. Chirurg. Anat., vol. ii, p. 554) gives 1.5 to 2 cm. (3/5 to 4/5 in.) as the greatest possible variation.
Tapping the distended bladder is done above the pubes, and care is to be taken to avoid wounding the peritoneum; this is to be done by knowing how its position is influenced as just detailed above. In front of the anterior bladder wall and between it and the posterior surface of the symphysis and transversalis fascia is the space of Retzius, filled with loose connective tissue. Care is to be taken not to infect it in operative procedures. It readily becomes infiltrated in extravasation of urine.
Fig. 452. - View of the interior of the base of the bladder.
Rupture of the bladder occurs most often through the peritoneum of its posterior surface when the bladder is distended. Extraperitoneal ruptures may occur when it is empty, and are usually the result of wounds by foreign bodies or spicules of bone in fractures.