The urinary bladder, commonly referred to as the bladder, is a key component of the urinary system. Located in the true pelvis, it functions primarily as a reservoir for urine. Below is a detailed overview of its anatomy, imaging features, and related pathology. (Urinary Bladder anatomy and imaging)
Gross Anatomy of Urinary Bladder
The bladder has a triangular shape with distinct regions:
- Posterior base (fundus): Forms the back portion.
- Superior dome: The top part of the bladder.
- Anterior apex: Directed behind the pubic symphysis and connected to the umbilicus via the median umbilical ligament (a remnant of the embryological urachus).
- Inferior neck: Leads to the urethra.
The bladder is lined with trabeculated transitional cell epithelium, except at the trigone, a smooth triangular area on the internal surface of the base. The trigone is defined by:
- Superolateral angles: Formed by the ureteric orifices.
- Inferior angle: Formed by the internal urethral orifice.
In males, as the prostate enlarges with age, the trigone may protrude, forming a mild elevation called the uvula of the bladder.
Structural Relationships of Urinary Bladder
- Urethra: Arises from the neck of the bladder and is surrounded by the internal urethral sphincter. It is separated from the pubic symphysis by the retropubic space of Retzius.
- Peritoneum: Covers the bladder loosely, except at the ureter insertions and the inferior bladder, where it condenses into pelvic fascia.
- In males, the peritoneum forms the rectovesical pouch between the rectum and bladder.
- In females, it forms the vesicouterine pouch and rectouterine pouch (pouch of Douglas).
Arterial Supply of Urinary Bladder
- Upper part: Supplied by the superior vesical artery (in both males and females).
- Lower part:
- Males: Inferior vesical artery.
- Females: Vaginal artery.
- Both arteries are branches of the anterior division of the internal iliac artery.
Venous Drainage of Urinary Bladder
- Males: Drained by the vesical and prostatic venous plexuses, which connect to the internal iliac and internal vertebral veins.
- Females: Drained by the vesical and uterovaginal plexuses, which connect to the internal iliac veins.
Lymphatic Drainage of Urinary Bladder
- Upper part: Drains to the external iliac lymph nodes.
- Lower part: Drains to the internal iliac lymph nodes.
Innervation of Urinary Bladder
- Autonomic innervation: Provided by the vesical nerve plexus, which includes:
- Sympathetic fibers: From the hypogastric nerves (originating from the inferior mesenteric ganglion).
- Parasympathetic fibers: From the pelvic splanchnic nerves (originating from the sacral parasympathetic outflow).
- Somatic innervation: Provided by the pudendal nerves.
Relations of Urinary Bladder
In Males:
- Anteriorly: Pubic symphysis.
- Posteriorly: Rectovesical pouch and rectum.
- Inferiorly: Obturator internus muscle, levator ani muscle, and prostate.
- Superiorly: Peritoneum.
- Laterally: Ischioanal fossa.
In Females:
- Anteriorly: Pubic symphysis.
- Posteriorly: Vesicouterine pouch, uterus, cervix, and vagina.
- Inferiorly: Urogenital diaphragm, pelvic fascia, and perineal membrane.
- Superiorly: Uterus and peritoneum.
- Laterally: Ischioanal fossa.
Variant Anatomy
- Double bladder: Receives ipsilateral ureters and has a separate urethra.
- Septation: Internal division into two or more compartments.
- Agenesis: Persistence of the cloaca.
- Ureterocele: Dilation of the intravesical part of the ureter.
Radiographic Features
The bladder is best evaluated when full.
Plain Radiograph:
- Appears as a rounded soft tissue mass.
Fluoroscopy (Cystography):
- The bladder is filled with contrast to assess its structure and function.
Ultrasound:
- Used to assess bladder wall thickness (normal: 3-5 mm).
- Ureteric jets can be visualized using color Doppler.
MRI:
- T1-weighted: Bladder wall and contents appear as homogeneous low signal.
- T2-weighted: Bladder wall appears as low signal, while urine appears as high signal.
Related Pathology
Structural Abnormalities:
- Pine cone bladder or Christmas tree bladder.
- Thimble bladder.
Neoplastic Conditions:
- Bladder cancer: Includes transitional cell carcinoma and squamous cell carcinoma.
Other Conditions:
- Bladder diverticulum.
- Bladder hernia.
- Ketamine bladder.
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging
Urinary Bladder anatomy and imaging