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.
Read Further From Authentic Sources:
1. Bladder Anatomy & Function
🔗 National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) – Bladder Basics
2. Imaging Techniques for Bladder Assessment
🔗 Radiopaedia – Urinary Bladder Imaging
3. Cystoscopy & Endoscopic Bladder Evaluation
🔗 Urology Care Foundation – Cystoscopy Procedure
4. Bladder Wall Layers & Histology
🔗 Kenhub – Urinary Bladder Histology
5. Pediatric Bladder Anatomy
🔗 Children’s Hospital of Philadelphia – Pediatric Bladder Conditions
