Urinary bladder !

The urinary bladder is the muscular bag behind the pubic bone that stores urine, about 400-600 ml, and empties it through the urethra.

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What it is

A hollow muscular bag behind the pubic bone that stores urine. In the female it sits in front of the uterus and the vagina.

What it does

Holds about 400-600 ml and empties through the urethra.

Key facts

Where: Pelvis behind pubic symphysis, rising into abdomen when full; trigone between ureteric orifices and internal urethral orifice
Blood supply: Superior and inferior vesical arteries (internal iliac; in females vaginal arteries); vesical venous plexus
Nerve: Pelvic splanchnics (S2–S4) contract detrusor; sympathetic (T11–L2) relaxes it; pudendal nerve (S2–S4) to external urethral sphincter
Function: Stores urine (about 400–600 ml) and empties it by detrusor contraction (micturition reflex)

Relations

In front: Pubic symphysis and the retropubic space (of Retzius), filled with fat and the vesical venous plexus
Above: Peritoneum over the dome; in the female the body of the uterus leans forward on it across the vesicouterine pouch; in the male small bowel and sigmoid colon
Behind: Female: the cervix and the anterior wall of the vagina. Male: the seminal glands and the ends of the ductus deferens, with the rectum behind and the rectovesical pouch above
Below: Female: the neck rests on the pelvic floor beside the urethra. Male: the neck sits on the base of the prostate
Lateral: Levator ani and obturator internus, with the obturator nerve and vessels on the side wall

How to find it

Empty, it hides behind the pubic symphysis and cannot be felt. In urinary retention it rises out of the pelvis as a smooth, tender midline mass above the pubis, dull to percussion, sometimes reaching toward the umbilicus. A suprapubic catheter goes in the midline just above the symphysis, into a full bladder, so the needle passes below the peritoneal reflection.

On imaging

Ultrasound shows wall thickness and the volume left after voiding; a full bladder is the window for transabdominal pelvic ultrasound. For suspected rupture, CT cystography (the bladder filled through a catheter): contrast around bowel loops means intraperitoneal; flame-shaped streaks in the perivesical fat mean extraperitoneal.

Common problems

Bladder infections (cystitis), much more common in women.
Overactive bladder and incontinence.
Cystocele: the bladder bulges into the front wall of the vagina.
Injury risk in a caesarean section or hysterectomy, so it is moved away and emptied with a catheter.

How it is diagnosed

Urine test and culture; bladder diary; ultrasound; cystoscopy in some cases.

Treatment

Antibiotics for infections; bladder training and medicines for overactive bladder.
Anterior repair for a cystocele.

Clinical notes

Extraperitoneal rupture is usually managed with catheter drainage; intraperitoneal rupture usually needs surgical repair
Spinal cord injury above the sacral segments gives a spastic, reflex bladder; damage to S2–S4 or the cauda equina gives a flaccid bladder that overflows
Male: an enlarged prostate obstructs outflow; the detrusor thickens and trabeculates and diverticula can form
Part of the bladder wall can slide into an inguinal or femoral hernia, more often in men, and is at risk when the hernia sac is opened

Development

Forms from the urogenital sinus after the urorectal septum divides the cloaca. The urachus runs from the dome to the umbilicus and normally closes into the median umbilical ligament; if it stays open, urine can leak at the umbilicus, or a urachal cyst or sinus forms.

Memory aid

Parasympathetic makes you Pee; Sympathetic helps you Store.

Test yourself

Think of the answer, then tap the question to see it.

Why can a suprapubic catheter be placed into a full urinary bladder without entering the peritoneum?

As it fills, the bladder rises above the symphysis with no peritoneum in front, so the needle passes below the peritoneal reflection.

How do extraperitoneal and intraperitoneal bladder ruptures differ in cause?

Extraperitoneal: usually with a pelvic fracture, urine in the retropubic space. Intraperitoneal: a blow to a full bladder tears the dome.

How do extraperitoneal and intraperitoneal bladder ruptures differ in management?

Extraperitoneal is usually managed with catheter drainage; intraperitoneal usually needs surgical repair.

Which autonomic divisions control storage and voiding of the urinary bladder?

Storage: sympathetic plus voluntary (pudendal). Voiding: parasympathetic, coordinated by the pontine micturition centre.

What type of bladder results from damage to S2–S4 or the cauda equina?

A flaccid bladder that overflows; injury above the sacral segments gives a spastic, reflex bladder.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): vesica urinaria TA2 3401
Official Spanish (DeCS): Vejiga urinaria DeCS D001743
English (TA2): Urinary bladder

Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Abdomen and Pelvis: Bladder.

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Representative model, for educational purposes only.

Urinary bladder highlighted on the Durgical 3D model