Contributors: Fraser J McConnell

 Species: Feline   |   Classification: Miscellaneous



  • Radiological examination forms a vital role in the investigation of gastrointestinal tract disease.
  • Radiography allows evaluation of shape and position of gastrointestinal tract.

Significant gastrointestinal disease may be present despite normal radiological appearance.

  • Contrast radiography is required for full evaluation of the gastrointestinal tract.

Radiographic considerations

  • Positional radiography is often useful particularly in gastric disease.
  • Taking both lateral projections  may reduce risk of missing gastric masses.
  • A low KVp and high mAs should be used to maximize contrast of abdominal radiographs.
  • Care should be taken to include the entire gastrointestinal tract for most investigations.
  • A table-top technique and detail film-screen combination should be used.


Sedation and general anesthesia will affect gastrointestinal motility.


  • Vomiting.
  • Suspected foreign body.
  • Abdominal pain.
  • Weight loss.
  • Melena.
  • Chronic diarrhea.
  • Investigation of abdominal masses.

Ultrasonography    Ultrasonography: GI system  often allows a more detailed evalaution of the gastrointestinal tract.

Radiographic anatomy


  • The stomach lies parallel with the ribs or perpendicular to the lumbar vertebrae.
  • Position may be affected by liver size.
  • The fundus lies dorsally and to the left of the midline.
  • The pylorus is ventral on the right hand side of midline.
  • Positioning the cat in right lateral recumbency allows the pylorus to fill with fluid and it may appear spherical.

This appearance may mimic a gastric foreign body   Stomach: foreign body - lateral (barium)  .

Small intestine

  • The position of the small intestine is largely dependent on the size and position of other abdominal organs.
  • Primary alteration in position of the small intestine is rare.
  • The small intestine however should form natural soft loops.
  • Diameter of small intestine is usually relatively uniform and can be assessed by comparison with the diameter of the ribs or lumbar vertebrae.
  • In many cats, especially if obese, the small intestine may appear bunched on the right side of the abdomen.

Large intestine and colon

  • The cecum is occassionally gas filled and appears as an ovoid lucency in the mid-abdomen on the right side adjacent to the ascending colon link.
  • The colon forms a question mark shape on the VD projection.
  • It can be recognized by its larger diameter than the small intestine and the presence of feces within its lumen.
  • Occasionally contrast studies, eg pneumocolon  are required to differentiate colon from small intestine.
  • The transverse colon lies adjacent to the greater curvature of the stomach and to the left of the pancreas.
  • The normal diameter of the colon is less than the length of L2.



  • Size
    • Depends on content.
  • Position
    • Cranial wall contacts liver, part of cardia touches diaphragm.
    • A line drawn from cardia to pylorus should be parallel to 12th intercostal space in normal animals.
    • On VD projection pylorus is in midline.
  • Opacity
    • Very variable depending on contents which may be fluid or gas.
  • Appearance
    • Can be divided into 4 parts:
      • Cardia - where esophagus enters.
      • Fundus - to the left and dorsal to the cardia.
      • Body - main part of the stomach.
      • Pylorus - where the duodenum exits the stomach.

Small intestine

  • Size
    • Width should be <12 mm.
  • Position
    • Location varies except for proximal duodenum which exits pylorus courses cranially before turning right and caudally.
  • Opacity
    • Variable as can contain gas or air but generally contains more fluid than air.
  • Appearance
    • Gentle curving loops.

Large intestine and colon

  • Size
    • Colon should be 2-3 times width of normal small intestine.
  • Position
    • Colon starts at cecum (ventral to L2/L3) and in cats is less spiral than in the dog.
    • Ascending colon becomes transverse colon caudal to stomach and then bends caudally to become descending colon.
  • Opacity
    • May contain gas or fecal material which often has mottled density.


Other imaging modalities

Ultrasonography  Ultrasonography: GI system 

  • Allows assessment of structure and thickness of gastrointestinal tract wall which is not possible with plain contrast radiography.

Contrast studies  Radiography: contrast media 

  • Introduction of contrast (gas or barium) into stomach, intestine or colon allows better assessment of position.