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57 Rectoanal Diseases – Medical and Surgical Management 613

diarrhea postoperatively can be expected, lasting from
VetBooks.ir several weeks up to three months. Various methods
of anastomosis (end‐to‐end, end‐to‐side, side‐to‐side)
have been described, including hand‐suturing, GIA and
TA stapling devices, transanal or transcecal circular
end‐to‐end anastomotic stapling, and biofragmentable
anastomotic rings. Excellent outcomes have been
reported with all the above methods and the exact tech-
nique chosen should depend on the planned resection,
surgeon experience, and equipment availability.
In cases of secondary megacolon due to pelvic canal
narrowing, typically due to malunion following pelvic
fracture, a pelvic osteotomy may be required. Duration
of clinical signs has been associated with outcome, with
cats that have had clinical signs for less than six months
experiencing better resolution of constipation postoper-
Figure 57.2 Intraoperative view of a severely distended and
atonic colon in a feline patient with idiopathic megacolon. atively. Cases with longer durations of clinical signs may
Patients in whom constipation and obstipation have progressed require a combination of subtotal colectomy along with
to this degree are best managed via subtotal colectomy. pelvic osteotomy to resolve their condition.

Failure of medical management for obstipation is
not uncommon, and likely reflects failure to recognize Prognosis
that the disease has already proceeded to megacolon. The long‐term prognosis after surgical treatment of
In patients that have proceeded to megacolon, surgical megacolon via subtotal colectomy in both dogs and cats
intervention is warranted (Figure 57.2). is generally considered excellent, with four‐year survival
rates reported of 90–100%. Patients should be monitored
Surgical Management of Megacolon for potential postoperative complications such as dehis-
cence with development of septic peritonitis, stricture,
Megacolon should be treated via surgical subtotal colec- and/or recurrent constipation.
tomy once clinical signs progress beyond the ability of
medical management to maintain the patient’s quality of
life. This is typically soon after diagnosis, as the condition Perianal Fistulae
is generally progressive and quickly becomes refractory
to dietary modification, laxatives, prokinetics, and/or Clinical Presentation
enemas. Although surgical treatment is essentially an
intestinal resection and anastomosis, several anatomic Perianal fistulation, as the name implies, is the develop-
factors combine to make this procedure significantly ment of ulcerative, fistulated tissue tracts in the perianal
more challenging than a typical midintestinal resection skin. Owner history generally includes excessive anal
and anastomosis. These include tension at the level of the and perianal licking, the presence of foul‐smelling dis-
ileocecocolic junction, lack of physical space to suture the charge, dyschezia, and tenesmus. Affected dogs are often
aborad intestinal segment due to the bony pubis, a higher extremely painful, and show a “dropped” tail posture.
bacterial load within the colon compared to other seg- These patients often resent tail handling during physical
ments of intestine, potential luminal disparity between examination, and may need to be deeply sedated or anes-
the two segments of bowel to be sutured together, prox- thetized to allow full examination. The perianal skin
imity to the ureters, and necessity for specific transection shows areas of ulceration and draining tract/fistula for-
locations if preserving the ileocolic valve. mation; these fistulas may extend up to 7 cm deep, and
Surgical subtotal colectomy should aim to remove as the entire circumference of the anus may be affected
much of the colon as possible to prevent recurrence. (Figure 57.3). Anal gland impaction and abscess forma-
Some surgeons prefer to preserve the ileocolic valve with tion are common co‐morbidities, but they are not a
the idea that it may reduce duration of diarrhea postop- prerequisite for development of this disorder.
eratively, as there is some support for this concept in the Perianal fistulation can be a devastating disease, with
published literature. Regardless of whether the valve is some dogs showing altered temperament and increasing
removed or not, a transient period of watery to mucoid difficulty in handling due to ongoing pain.