Introduction

• Cause: multifunctional including: obstruction, neurological, orthopedic, prostatic, metabolic and functional causes.
• Signs: tenesmus, anorexia, reduced fecal output, dry hard feces, vomiting.
• Diagnosis: signs, radiography.
• Treatment: find and correct underlying cause, fecal softening, enemas, occasionally manual removal.
• Prognosis: good for resolution of signs but may recur.
• If untreated megacolon Megacolon: acquired may develop.

Pathogenesis

Predisposing factors

General

• Foreign material in diet, eg bones, rawhide, hair accumulation.
• Intestinal lumen narrowing:
  • Prostatic enlargement.
  • Pelvic fracture malunion.
  • Neoplasia (intraluminal, mural or extraintestinal).
  • Foreign body impaction.
  • Rectal tumor/stricture Rectum: stricture.
  • Rectal polyp.

• Dehydration due to concurrent disease such as chronic kidney disease Kidney: chronic kidney disease (CKD) or increased losses from vomiting/diarrhea.
• Reduced gastrointestinal motility:
  • Neurological dysfunction due to spinal injury.
  • Endocrine disease, eg hypothyroidism Hypothyroidism.
  • Metabolic disease, eg hypercalcemia Hypercalcemia: overview, hypokalemia Hypokalemia, hypomagnesemia Hypomagnesemia.
  • Drug-induced, eg anticholinergics, diuretics Furosemide, opioids Analgesia: opioid.

• Behavioral - related to infrequent voiding:
  • Paraplegia/spinal.
  • Animal unwilling to posture, eg hip dysplasia Hip: dysplasia.
  • Painful defecation, eg pelvic fracture, anal sacculitis Anal sacculitis.
  • Laziness or lack of opportunity to exercise (hospitalized).
• Inadequate water intake:
  • Lack of access to water due to social or mobility issues.
  • Oral disease or difficulty swallowing.
  • Diet high in insoluble fiber such as commercial therapeutic weight loss diet.
• Obesity Obesity.

• Dysautonomia Dysautonomia (very rare) (except in Kansas and Missouri).
• Lead toxicity Lead toxicity  - can cause constipation or diarrhea.

Pathophysiology

• Failure to pass feces due to functional/mechanical causes.
• Prolonged retention of feces in colon → increased water resorption → harder drier feces.
• Resorption of toxins may also occur → vomiting.
• Vomiting can also result from vagal stimulation of vomiting center as a result of bowel wall stretching and/or irritation.
• Prolonged constipation may lead to megacolon.

Timecourse

• Days to weeks for constipation to develop.
• Predisposing factors may be present for years.

Diagnosis

Treatment

Prevention

Outcomes