Overview

Constipation is characterized by infrequent or difficult evacuation of feces. Obstipation is the result of recurrent, intractable constipation. Constipation and obstipation may culminate in the syndrome of megacolon. Constipation is a relatively frequent problem in cats while obstipation and megacolon are less common.

Etiology

Primary constipation is due to abnormal colonic motility. Neuromuscular dysfunction may occur in animals with lumbosacral disease or in cats with idiopathic megacolon. Dehydration, hypokalemia, and hypocalcemia may all negatively impact colonic motility. Inactivity and obesity may also be a cause of prolonged large bowel transit time. Furthermore, use of opiates and anticholinergics may also lead to constipation.

Secondary constipation is more common and is associated with processes that impair the transit and evacuation of colonic content, such as mechanical obstruction of the colon or rectum. Obstructions can be intraluminal (e.g., fecal impaction, FB, stricture), intramural (neoplasia), or extramural (e.g., narrowing of the pelvic canal, space-occupying lesions impinging on the descending colon or rectum).

Clinical Presentation

Typical clinical signs include reduced, absent, or painful defecation, and may be progressive. Other clinical signs associated with a primary underlying disease might be present. The onset of distal bowel signs may be insidious and animals may be presented late when the problem is severe. Dyschezia may be observed. Chronic constipation/obstipation may have systemic repercussions such as anorexia, lethargy, weight loss, and vomiting.

Diagnosis

A detailed physical examination is required. This may reveal varying degrees of dehydration, weight loss, and abdominal pain. Rectal palpation (performed under sedation) is challenging in cats, but might reveal pelvic canal abnormalities, a stricture, etc.

A thorough screening of animals presented with recurrent constipation is recommended to identify obstructions and underlying diseases and assess the systemic repercussions of the problem. A minimal database consisting of CBC, biochemistry panel, and urinalysis should be obtained in all cats presented for constipation to rule out metabolic causes and underlying chronic diseases such as chronic kidney disease. Abdominal radiographs help characterize the severity of colonic impaction and identify predisposing factors such as intraluminal radiopaque foreign material, intraluminal or extraluminal mass lesions, pelvic fractures, and spinal cord abnormalities. Extraluminal mass lesions may be further evaluated by abdominal ultrasonography and guided biopsy, whereas intraluminal mass lesions are best evaluated by endoscopy.

Differential Diagnosis

Diseases of the anorectum, such as anal sacculitis, may cause painful defecation. Pseudocoprostasis or constipation can be caused by matted hair around the anus, which occasionally occurs in long-haired cats. Importantly, some cat owners may not be able to differentiate stranguria and dyschezia, and lower urinary tract diseases should always be ruled out.

Management

All identified underlying problems should be treated. If the cause of the obstruction can be addressed in a timely manner, colonic function may be preserved. However, prolonged obstruction is ultimately associated with loss of colonic contractility.

The different methods for treatment of idiopathic, nonobstructive constipation include administration of oral laxatives, enemas (Table 1), and prokinetic agents such as cisapride (0.1–0.5 mg/kg PO q8–12h).

Table 1

In cats with chronic recurrent idiopathic constipation, a stepwise approach has proven useful. Mild to moderate constipation (e.g., first occurrence, recurrence after a long interval with normal defecation) is best treated with an initial enema followed by treatment with laxatives. Maintaining these cats on a psyllium-enriched diet or continuing daily administration of laxatives is recommended. Addition of prokinetics is necessary when management with diet and laxatives fails. Early use of cisapride is likely to prevent the progression of constipation to obstipation and dilated megacolon in these cats. However, some cases become refractory to conservative treatment and slowly progress to obstipation and dilated megacolon.

When treating a constipated cat, enemas should be injected slowly, as rapid administration may cause reflex vomiting and rapid and excessive efflux of the liquid, and may also increase the risk of colonic perforation. If several enemas fail to induce defecation, nasoesophageal administration of polyethylene glycol (PEG) 3350. PEG 3350 is an osmotic laxative that has been shown to be safe and palatable in cats. It can be administered to constipated or obstipated cats through a nasoesophageal tube as a CRI at a rate between 6 and 10 ml/kg/h. In a recent study, the mean total dose required was 80 ml/kg (range 40–156), and defecation occurred on average 8 hours after initiation of treatment (range 5–24). The technique has considerably decreased the need for enemas in feline practice, and the number of cases that need to undergo manual extraction of feces, a technique used when all other options have failed. Manual extraction is best performed on an anesthetized cat with careful transabdominal colonic massage and simultaneous rectal administration of a combination of warm water or physiologic saline with water-soluble lubricants to break down the impacted feces. Some authors recommend administering a low dose of metronidazole (7.5–15 mg/kg PO q12h) in order to limit the risk of bacterial translocation during or after the procedure.

A surgical approach is the last option for severe cases with obstipation or megacolon that does not respond to the conservative treatment options. Different techniques for colectomy have been successful.

Prognosis

Many cats have one or two episodes of constipation without further recurrence, although others may progress to complete colonic failure. When conservative management has failed, colectomy is usually associated with a favorable prognosis, although mild to moderate diarrhea may persist for 4–6 weeks postoperatively in some cases.

References

1.  Garr AP, Gaunt MC. Constipation resolution with administration of polyethylene-glycol solution in cats. J Vet Intern Med. 2010; 24:723 [abstract] (Open access).

2.  Gaschen F. Disorders of esophageal, gastric and intestinal motility in cats. In: Little SE, ed. August's Consultation in Feline Medicine. Vol. 7. St. Louis, MO: Elsevier; 2016.

3.  Washabau RJ. Colonic dysmotility. In: Washabau RJ, Day MJ, eds. Canine and Feline Gastroenterology. St. Louis, MO: Elsevier; 2013.