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Pylorus of stomach

The pylorus is the distal region of the stomach that connects the gastric antrum to the duodenum. It consists of the pyloric antrum (proximal portion) and the pyloric canal (distal portion), which terminates at the pyloric sphincter, a thickened ring of circular smooth muscle that regulates gastric emptying. Anatomically, the pylorus lies at the level of L1 (transpyloric plane), slightly to the right of the midline. The pyloric region plays a vital role in regulating the passage of gastric contents into the duodenum while preventing duodenogastric reflux.

Synonyms

  • Gastric pylorus

  • Pyloric sphincter

  • Distal stomach outlet

Function

  • Regulates gastric emptying into the duodenum

  • Acts as a sphincter, preventing backflow of intestinal contents

  • Controls the rate of digestion by coordinating peristaltic contractions

  • Prevents duodenogastric reflux

Arterial Supply

  • Primarily by the right gastric artery and right gastroepiploic artery (branches of the common hepatic artery)

  • Additional supply from the left gastric artery and gastroduodenal artery

Venous Drainage

  • Venous blood drains via the right gastric vein and right gastroepiploic vein, both tributaries of the portal venous system

  • Connects directly to the splenic vein and superior mesenteric vein through portal tributaries

Nerve Supply

  • Parasympathetic fibers from the vagus nerve (CN X) regulate motor activity and sphincter relaxation

  • Sympathetic fibers from the celiac plexus inhibit gastric motility and contract the sphincter

MRI Appearance

T1-weighted images:

  • Pyloric wall appears intermediate signal intensity; lumen contains variable contents (air = signal void, fluid = low signal)

  • Perigastric fat is hyperintense, providing contrast for wall definition

T2-weighted images:

  • Pyloric wall shows intermediate signal intensity

  • Fluid-filled lumen appears bright hyperintense, aiding in identifying the canal and sphincter

  • Hypertrophy or thickening (e.g., pyloric stenosis) shows as symmetric or asymmetric mural thickening

STIR (Short Tau Inversion Recovery):

  • Suppresses surrounding fat, highlighting edema or inflammation of the pyloric wall

  • Pathological thickening (e.g., gastritis, tumor infiltration) appears bright hyperintense

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal pyloric wall enhances homogeneously

  • Neoplastic lesions or inflammation show heterogeneous, asymmetric, or irregular enhancement

CT Appearance

Non-contrast CT:

  • Pylorus appears as a soft tissue density tubular structure between the antrum and duodenum

  • Lumen may contain air (hypodense) or fluid (soft tissue density)

  • Wall thickening is visible in pathological states

Contrast-enhanced CT (CECT):

  • Pyloric wall enhances uniformly in normal states

  • Hypertrophic pyloric stenosis: demonstrates concentric wall thickening with narrowed lumen

  • Malignancy: appears as irregular, enhancing mural mass possibly extending into adjacent structures

  • Excellent for assessing gastric outlet obstruction, tumors, or inflammation

MRI images

Pylorus of stomach anatomy MRI axial image -img-00000-00000

MRI images

Pylorus of stomach anatomy MRI CORONAL image -img-00000-00000

CT image

Pylorus of stomach anatomy CT axial image -img-00000-00000