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Urinary Bladder in Pregnancy

The urinary bladder is a hollow, muscular organ located in the anterior pelvis that stores urine until voluntary micturition. During pregnancy, the bladder undergoes important anatomical and functional changes due to the enlarging uterus and hormonal influences.

The gravid uterus progressively compresses and displaces the bladder, especially in the second and third trimesters. These changes alter bladder capacity and voiding frequency and are important to recognize in radiology and obstetrics.

Synonyms

  • Vesica urinaria

  • Maternal bladder

  • Gravid urinary bladder

Structure

  • Wall: Composed of mucosa (transitional epithelium), submucosa, muscularis (detrusor muscle), and adventitia/serosa

  • Neck: Inferior region continuous with urethra

  • Lumen: Normally filled with urine, variable in volume depending on maternal hydration and voiding cycle

Relations in Pregnancy

  • Anteriorly: Pubic symphysis and anterior abdominal wall

  • Posteriorly: Uterus (enlarged during pregnancy) and vagina

  • Superiorly: Expanding uterus compresses and elevates the bladder dome as pregnancy progresses

  • Inferiorly: Pelvic diaphragm and urethra

Function

  • Reservoir for urine storage and controlled emptying

  • Maintains urinary continence during increased intra-abdominal pressure of pregnancy

  • In pregnancy, frequent urination results from both mechanical compression and hormonal relaxation of bladder musculature

Clinical Significance in Pregnancy

  • Urinary frequency/urgency: Common symptom due to uterine compression

  • Urinary tract infections: Increased risk during pregnancy due to stasis and hormonal effects

  • Obstetric imaging: Full bladder used in early pregnancy ultrasound to visualize uterus

  • Placenta accreta spectrum: Relationship of placenta and bladder is critical for diagnosis of invasion

  • Surgical relevance: Bladder is at risk during cesarean section or in abnormally invasive placenta

MRI Appearance

T2 HASTE (T2 GRE):

  • Urinary bladder lumen (urine): very bright hyperintense signal

  • Bladder wall: thin, low-signal rim

  • In pregnancy, compressed bladder may appear flattened or displaced superiorly/posteriorly

T1 GRE:

  • Urinary bladder lumen: low signal intensity (dark)

  • Hematuria, infection, or high-protein content: focal or diffuse hyperintensity

  • Wall: appears as a thin intermediate-to-low signal outline

MRI image

Urinary bladder (pregnancy) mri sagittal image