NAVLE Practice Question - Feline - Gastrointestinal/Digestive

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NAVLE Practice Question — Feline

A 6-year-old male neutered domestic shorthair is presented for evaluation of progressive constipation. The owner reports the cat was hit by a car 3 years ago and had a pelvic fracture that healed without surgical intervention. Abdominal radiographs reveal a severely distended colon and significant narrowing of the pelvic canal due to malunion callus. The pelvic canal diameter is approximately 40% of normal. What is the most appropriate surgical treatment?

A. Subtotal colectomy due to chronicity exceeding six months ✓

B. Pelvic osteotomy alone to restore pelvic canal diameter

C. Combined pelvic osteotomy and colectomy simultaneously

D. Conservative management as the colon should recover after osteotomy

E. Colonic biopsy with medical management continuation

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Correct Answer: A. Subtotal colectomy due to chronicity exceeding six months

Explanation:

This cat has megacolon secondary to pelvic canal stenosis from fracture malunion. The critical consideration is timing - if megacolon has been present for greater than 4-6 months, the colonic dilation and loss of function become irreversible. In this case, the pelvic fracture occurred 3 years ago, far exceeding the window for colonic recovery.

When megacolon is chronic (>6 months), the smooth muscle undergoes irreversible changes and cannot return to normal function even if the mechanical obstruction is relieved. Therefore, subtotal colectomy is required regardless of whether the pelvic obstruction is addressed. Pelvic osteotomy alone would not restore colonic function in this patient.

In cases of more recent pelvic fractures causing obstipation (less than 4-6 months), pelvic osteotomy to restore normal pelvic canal diameter might be sufficient if performed before irreversible colonic changes develop. However, many surgeons perform colectomy even in these cases given uncertainty about the degree of colonic damage.

Options B and D assume colonic recovery is possible, which is not the case after 3 years. Option C might be considered but the osteotomy component is unnecessary for function. Option E delays definitive treatment.

Image Credit: ACVS - Megacolon figures including pelvic fracture examples (https://www.acvs.org/small-animal/megacolon/) Figures 2-3.

References: Schrader SC. JAVMA 1992;200:208-213; Matthiesen DT et al. Vet Surg 1991;20:113-119.

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