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Fundus of urinary bladder

The fundus of the urinary bladder, also referred to as the base or posterior surface of the bladder, is the portion opposite the bladder apex. It lies directed posteroinferiorly and is of clinical and radiological importance due to its relations with the ureters, seminal vesicles, prostate (in males), and uterus and vagina (in females). Its structure and relationships are critical in gynecology, urology, and pelvic surgery.

Synonyms

  • Base of bladder

  • Posterior wall of bladder

  • Bladder fundus

Location and Boundaries

  • Superiorly: Related to the bladder body and dome

  • Inferiorly: Continuous with the bladder neck and trigone

  • Anteriorly: Opposite the bladder apex and anterior wall

  • Posteriorly: Directed toward pelvic cavity structures — seminal vesicles, vas deferens, rectum (male); uterus, cervix, and vagina (female)

Relations

  • Male:

    • Posterior surface is related to the seminal vesicles and ampullae of vas deferens

    • Inferiorly related to the prostate gland

    • Superior relations with loops of small intestine or sigmoid colon (depending on distension)

  • Female:

    • Posterior surface related to the anterior wall of the uterus and cervix

    • Separated from uterus by the vesicouterine pouch

    • Inferior relation to the upper anterior vaginal wall

Function

  • Acts as the posterior storage surface of the bladder, forming part of the bladder reservoir for urine

  • Provides attachment for ureters as they enter obliquely into the bladder wall at the fundus to prevent reflux

  • Maintains integrity of the vesicoureteral junction and contributes to continence

Clinical Significance

  • Common site of tumors (urothelial carcinoma)

  • Important landmark for ureteric orifices and the trigone

  • In females, may be involved in endometriosis or uterine pathology extending into bladder

  • In males, posterior bladder wall tumors can mimic seminal vesicle or prostate lesions

  • Pouch-related collections (vesicouterine pouch in females, rectovesical pouch in males) can extend around the fundus

MRI Appearance

T1-weighted images:

  • No urine: Fundus appears as low signal intensity muscular wall, often indistinct from adjacent fat planes

  • Urine present: Lumen shows dark low signal intensity; wall remains low signal

  • Fat: Bright signal outlining bladder wall externally

T2-weighted images:

  • No urine: Fundus visualized as dark low signal muscular wall

  • Urine present: Bright high signal filling bladder lumen, wall remains low signal

  • Fat: Intermediate-to-bright signal external to bladder wall

STIR (Short Tau Inversion Recovery):

  • No urine: Fundus remains low signal band

  • Urine present: Fluid appears bright hyperintense

  • Fat: Suppressed, appearing dark

T1 Fat-Sat Post-Contrast:

  • Normal fundus wall enhances thinly and uniformly

  • Tumors show focal or irregular enhancing nodules or masses

  • Inflammation may show diffuse wall enhancement

  • Urine does not enhance

CT Appearance

Non-Contrast CT:

  • Fundus appears as a soft tissue wall of homogeneous density

  • No urine: Collapsed lumen difficult to identify

  • Urine present: Appears as low-density fluid (0–20 HU) with distinct wall

  • Fat planes surrounding the fundus usually visible unless obscured by inflammation

Post-Contrast CT:

  • Normal bladder wall enhances thinly and uniformly

  • Tumors appear as enhancing mural nodules or masses

  • Cystitis shows diffuse wall thickening and enhancement

  • Surrounding fat stranding indicates inflammation or infection

MRI image

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CT image

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CT image

Fundus of urinary bladder ct sagittal anatomy image-img-00000-00000