Radiographic Anatomy of the Abdomen in Dogs and Cats

Introduction

• Presenter: Pit Mantis
• Topic: Normal radiographic appearance of abdominal organs in dogs and cats

Key Points

• Not all abdominal organs/structures are always visible on radiographs.
• Commonly visible structures:
  • Stomach
  • Liver
  • Urinary bladder
  • Small intestine
  • Colon (especially descending colon)
• Partially visible structures: Spleen (especially in cats)
• Seldom seen structures: Prostate gland, pancreas, adrenal glands, ovaries, mesenteric lymph nodes

Liver

• Location: Cranioventral, within the rib cage
• Important factors:
  • Caudal edge is pointed and sharp
  • Gastric axis: line from fundus to pylorus should be vertical to the spine or parallel to the ribs
• If liver margin extends beyond rib cage but is sharp, consider inspiratory radiograph, not necessarily hepatomegaly.

Spleen

• Commonly seen in dogs; tail of spleen is usually ventrally located.
• In dogs, triangular shape on DV view, behind the stomach.
• In cats, rarely seen unless spleenomegaly.

Stomach

• Appearance varies with positioning due to air movement.
• Right lateral view: air moves to fundus and body.
• Rule: Stomach extending beyond last rib indicates dilatation.
• Pylorus location: near midline and right in dogs; mostly midline in cats on ventrodorsal view.

Small Intestine

• Cannot identify individual segments radiographically.
• Measurements:
  • Diameter: no wider than the height of mid-lumbar vertebra or twice the width of a rib in dogs.
  • In cats: less than 12 mm or central part of L4.

Large Intestine and Colon

• Cecum: C-shaped, at level of L3.
• Descending colon: visible radiographically; not more than diameter of L7.
• Contrast studies with barium are useful but messy.

Kidneys

• Not normally seen; location important.
• Measurements:
  • Dog: 13th thoracic to 2nd lumbar for right kidney, 2nd to 4th lumbar for left kidney.
  • Cat: Between first and fourth lumbar (right), second to fifth lumbar (left).
  • Length: 2.5-3.5 times the length of L2 in dogs; 1.8-2.4 times in cats.

Ureters

• Not normally seen unless dilated or contain calculi.
• Seen with contrast studies like IVU or excretory urogram.

Urinary Bladder

• Visibility: Cranial to pubis, ventral to rectum and descending colon.
• Wall thickness: up to 2mm in a full bladder.
• Urethra usually not seen; requires contrast studies.

Prostate Gland

• Dorsal to pubis, ventral to ilium.
• Size: less than 2/3 of the pelvic inlet or 70% of the distance between pubic rim and sacral promontory.

Uterus and Ovaries

• Not seen in non-pregnant females unless abnormal.
• Seen in obese animals due to fat density difference.

Conclusion

• Summary of radiographic anatomy for abdominal organs in dogs and cats.
• Importance of understanding normal appearance for diagnosis.