A full urinary bladder in an adult may be punctured through the anterior abdominal wall just above the pubic symphysis without entering the peritoneal cavity. What anatomical change makes this possible?

• A When full the bladder descends deeper into the true pelvis away from the peritoneum
• B The empty bladder lies entirely below the peritoneal reflection, and when full it peels the peritoneum upward off the anterior abdominal wall ✓
• C The urachus closes the peritoneal space over the filled bladder
• D When full the bladder becomes retroperitoneal behind the rectum

Explanation

The empty adult bladder is an extraperitoneal organ below the peritoneal reflection. As it fills it enlarges superiorly into the abdomen, stripping the peritoneum off the anterior abdominal wall, so a suprapubic needle enters the bladder wall directly without traversing the peritoneal cavity. In infants the bladder is an abdominal organ even when empty, which is a related point often tested.

Reference: Snell's Clinical Anatomy by Regions, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.