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Basics ⬇

Basics

Definition

  • Dyschezia-painful or difficult defecation
  • Hematochezia-bright red blood in or on the feces

Pathophysiology

Results from inflammatory, infectious, or neoplastic conditions affecting the colon, rectum, or anus.

Systems Affected

Gastrointestinal

Signalment

  • Dog and cat
  • No breed or sex predilection

Signs

Historical Findings

  • Vocalizing and whimpering during defecation.
  • Tenesmus.
  • Decreased frequency of defecation in association with severe dyschezia (animal resists defecating due to pain) resulting in constipation or obstipation.
  • Mucoid, bloody diarrhea with a marked increase in frequency and scant fecal volume in patients with colitis.
  • Scooting behavior in association with anal gland infection or impaction.

Physical Examination Findings

  • Rectal examination may reveal hard feces (constipation or obstipation), diarrhea (colorectal disease), colorectal masses, anorectal thickening, rectal or colonic strictures, anal sac enlargement/pain, prostatomegaly, or perineal hernias.
  • Fistulous tracts around anus occur with perianal fistulae.
  • Anal occlusion with matted hair and feces occurs with pseudocoprostasis.

Causes

Rectal/Anal Disease

  • Stricture or spasm
  • Anal sacculitis or abscess
  • Perianal fistulae
  • Rectal or anal foreign body
  • Pseudocoprostasis
  • Rectal prolapse
  • Trauma-bite wounds, etc.
  • Neoplasia-adenocarcinoma, lymphoma, and anal sac tumors
  • Rectal polyps
  • Mucocutaneous lupus erythematosus

Colonic Disease

  • Neoplasia-adenocarcinoma, lymphoma, other tumors
  • Idiopathic megacolon-cats
  • Inflammation-IBD, infectious parasitic agents, colitis secondary to dietary-responsive enteropathy (see Colitis and Proctitis)
  • Constipation (see Constipation and Obstipation)

Extraintestinal Disease

  • Fractured pelvis or pelvic limb
  • Prostatic disease
  • Perineal hernia
  • Intrapelvic neoplasia

Risk Factors

  • Ingestion of hair, bone, foreign material may contribute to constipation and subsequent dyschezia.
  • Environmental factors such as a dirty litter pan, infrequent outside walks may contribute to constipation and subsequent dyschezia.

Diagnosis ⬆ ⬇

Diagnosis

It is pivotal to recognize that hematochezia in animals can be seen with both diffuse colitis as well as with focal or discrete colorectal neoplasms. The fundamental differences in the clinical presentation between the two disorders can usually be recognized during the history and following a thorough physical examination, including a rectal examination. Dogs with colorectal neoplasms do not have diarrhea, and the most important and frequent clinical sign is hematochezia in the absence of an increase in defecation frequency or change in stool consistency. Pencil-thin or ribbon-like stools can be seen when the colorectal neoplasm is advanced, causing a change in the shape of the stool. A rectal examination must be performed on every patient with a history of hematochezia or dyschezia.

Differential Diagnosis

  • Dysuria, stranguria, or hematuria-abnormal findings on urinalysis, such as pyuria, crystalluria, bacteriuria. The history and physical examination should differentiate whether the animal is having difficulty urinating or defecating.
  • Dystocia-differentiate with history and imaging.

CBC/Biochemistry/Urinalysis

  • Usually unremarkable, unless there is a history of chronic blood loss with secondary iron deficiency causing a microcytic and hypochromic non-regenerative anemia.
  • Mild neutrophilia (with or without a left shift) with infection or inflammation.

Other Laboratory Tests

Centrifugation fecal flotation to help rule out parasitic causes of colitis

Imaging

  • Pelvic radiographs may reveal intrapelvic disease, foreign body, or fracture.
  • Ultrasonography may demonstrate prostatic disease or caudal abdominal masses; however, a portion of the descending colon cannot be visualized because of the pelvis.

Diagnostic Procedures

Colonoscopy/proctoscopy to evaluate for inflammatory or neoplastic disease

Treatment ⬆ ⬇

Treatment

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

  • Antibiotics-if bacterial infection (e.g., anal sac abscess); amoxicillin/clavulanic acid 15 mg/kg PO q12h for 7–10 days.
  • Anti-inflammatory drugs-sulfasalazine or prednisone (dogs) and prednisolone (cats) if colitis is present (see Colitis chapters).
  • Cyclosporine (5 mg/kg q12h for 3–4 months with gradual taper thereafter) for dogs with perianal fistulae.
  • Laxatives-lactulose, 1 mL/4.5 kg PO q8–12h to effect; docusate sodium or docusate calcium-dogs, 50–100 mg PO q12–24h; cats, 50 mg PO q12–24h.
  • Cisapride-prokinetic indicated for cats with moderate to severe megacolon (and no evidence of obstruction) in conjunction with lactulose and dietary therapy at a dose of 5 mg per cat q12h.

Contraindications

Avoid agents that cause increased fecal bulk (insoluble fiber), unless specifically indicated (colitis).

Precautions

N/A

Possible Interactions

N/A

Alternative Drug(s)

N/A

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

Daily monitoring by the owner with periodic phone calls to the clinician every 2–3 weeks during the beginning of treatment.

Possible Complications

  • May see fecal incontinence following surgical resection of anal sacs or colorectal tumors if anal sphincter is compromised.
  • Secondary megacolon may occur if obstipation is severe and long-term.

Miscellaneous ⬆

Miscellaneous

Associated Conditions

N/A

Age-Related Factors

N/A

Zoonotic Potential

N/A

Pregnancy/Fertility/Breeding

Caution with corticosteroids, antibiotics

Abbreviations

  • IBD = inflammatory bowel disease

Author Stanley L. Marks

Consulting Editor Stanley L. Marks

Suggested Reading

Webb CB. Anal-rectal disease. In: Bonagura JD, Twedt DC, eds., Current Veterinary Therapy XIV. St. Louis, MO: Elsevier, 2009, pp. 527–531.

Zoran DL. Rectoanal disease. In: Ettinger SJ, Feldman EC, eds., Textbook of Veterinary Internal Medicine, 6th ed.St. Louis, MO: Elsevier, 2005, pp. 1408–1420.