Introduction

• Cause: enlargement of the abdomen brought about by increased intra-abdominal pressure or by abnormalities of the abdominal wall.
• Signs: variable, dependent on cause.
• Diagnosis: physical examination, rectal examination, auscultation, laparoscopy, abdominocentesis, radiography, ultrasound, exploratory laparotomy.
• Treatment: dependent on cause.
• Prognosis: dependent on cause can be serious and life-threatening.

Pathogenesis

Etiology

• One of the 'Seven Fs', ie:
  • Fat.
  • Fluid.
  • Food.
  • Feces.
  • Fetus.
  • Flatus.
  • Foreign body.

Gas accumulation

• Gastrointestinal ileus:
  • Severe ascites associated with peritonitis    Abdomen: peritonitis   (rare).
  • Carbohydrate overload, eg whole grain corn   Stomach: impaction   (due to large intestinal accumulation of fluid).
• Large colon obstruction:
  • Intussusception   Large colon: intussusception    Cecum: intussusception - cecocecal / cecocolic  .
  • Tympany.
  • Torsion/volvulus   Colon: torsion  .
  • Foreign body   Colon: small - obstruction  .
  • Enterolith   Gastrointestinal: enterolith  .
  • Displacement   Colon: displacement - left dorsal    Colon: displacement - pelvic flexure    Colon: displacement - right dorsal  .
  • Impaction   Colon: impaction  .
• Small intestinal obstruction   Ileum: impaction    Gastrointestinal: stricture    Gastrointestinal: small intestine - torsion    Gastrointestinal: small intestine - intussusception   (not in adults).
• Cecal obstruction   Cecum: torsion    Cecum: impaction  .
• Air ingestion (aerophagia), eg crib-biting   Behavior: crib-biting and wind-sucking   (very rare).
• Pneumoperitoneum/free gas in abdomen: secondary to trauma or anaerobic infection, eg GI rupture   Stomach: rupture  , peracute peritonitis.

Fluid accumulation

• Ascites:
  • Peritonitis   Abdomen: peritonitis  .
  • Neoplasia.
  • Right-sided heart failure   Heart: failure - overview  .
  • Hypoproteinemia   Hypoproteinemia  .
• Hydrops amnii/allantois   Uterus: hydroallantois / hydroamnios  .
• Hemoperitoneum (very rare):
  • Splenic rupture.
  • Hepatic rupture.
  • Middle uterine artery rupture in mares   Uterus: uterine artery / vein rupture  .
  • Neoplasia.
  • Rupture of a verminous aneurysm of the cranial mesenteric artery   Cardiovascular: parasitic arteritis  .
• Uroperitoneum   Abdomen: uroperitoneum  :
  • Ruptured bladder   Bladder: rupture  .

Intra-abdominal mass

• Neoplasia   Abdomen: lipoma - pedunculated  .
• Abscess   Abdomen: abscess  .

Body wall abnormalites

• Prepubic tendon rupture   Prepubic tendon: rupture  .
• Cushings syndrome   Pituitary: adenoma  .

Specific

• Crib-biters: aerophagia.
• Carbohydrate overload: bloat.
• Sandy soils: sand impaction.
• Pregnancy.

Pathophysiology

• Increased intra-abdominal pressure from fluid or gas accumulation or a tissue mass    →   abdominal distention. 
• Abnormalities of the body wall itself can   →    an increase in abdominal size.

Timecourse

• Can be acute, eg cecal obstruction, large colon obstruction, pre-pubic tendon rupture   Prepubic tendon: rupture  .
• Can be chronic, eg hydrops amnii/allantois   Uterus: hydroallantois / hydroamnios  .

Diagnosis

Treatment

Prevention

Outcomes