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Topic

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Fetal stomach

The fetal stomach is a fluid-filled abdominal organ seen in prenatal imaging as a round or oval structure in the left upper abdomen, just below the diaphragm. It develops from the foregut during early embryogenesis and is consistently visible on prenatal imaging by 14–16 weeks of gestation.

The presence, size, and contents of the stomach are important markers of fetal swallowing, amniotic fluid regulation, and gastrointestinal tract patency. Abnormalities in stomach appearance or size can indicate a variety of congenital or acquired conditions.

Synonyms

  • Prenatal stomach

  • Fetal gastric bubble

  • Gastric sac in utero

Structure and Development

  • Embryologic origin: Derived from foregut (endoderm) around the 4th week of gestation

  • Shape: Initially fusiform, later rotates and assumes J-shaped gastric form

  • Wall: Thin muscular coat with mucosal lining, visible on advanced fetal MRI

  • Contents: Primarily amniotic fluid swallowed by fetus; later may contain debris (vernix, blood, meconium)

Relations

  • Superiorly: Fetal diaphragm and left lung base

  • Inferiorly: Developing small intestine and spleen

  • Anteriorly: Abdominal wall

  • Posteriorly: Pancreas and left kidney (retroperitoneal structures)

Function

  • Stores swallowed amniotic fluid

  • Contributes to amniotic fluid homeostasis via swallowing and absorption

  • Provides space for fetal gastrointestinal motility and early digestive activity

  • Serves as a biomarker of fetal swallowing and GI patency on imaging

Clinical Significance

  • Normal finding: Visible fetal stomach bubble by ~16 weeks is reassuring

  • Non-visualization: May suggest esophageal atresia, oligohydramnios, or technical factors

  • Enlarged stomach (megastomach): Seen in duodenal atresia, gastric outlet obstruction, or impaired swallowing

  • Double bubble sign: Duodenal atresia (stomach + proximal duodenum dilation)

  • Polyhydramnios: May be secondary to impaired swallowing or outlet obstruction

  • MRI role: Used when ultrasound findings are inconclusive for GI tract anomalies

MRI Appearance

T2 HASTE (T2 GRE):

  • Stomach lumen (fluid-filled): Very bright hyperintense signal

  • Stomach wall: Thin hypointense rim, well defined against bright fluid

  • Surrounding structures: Amniotic fluid is also bright, but stomach bubble appears as a discrete rounded/oval bright structure in the left abdomen

  • Obstruction or abnormal debris: May alter lumen signal (heterogeneous)

T1 GRE:

  • Stomach lumen (normal fluid-filled): Low signal intensity (dark)

  • Wall: Thin hypointense outline

  • Pathological contents:

    • Hemorrhage, proteinaceous fluid, or meconium → focal or diffuse bright hyperintensity

    • Debris/vernix → may appear with scattered hyperintense foci

MRI image

fetal stomach MRI axial anatomy image-img-00000-00000

MRI image

fetal stomach mri sag image