Megacolon in a 12-year-old cat. Photos courtesy Dr. Phil Zeltzman Garfield, a 12-pound, 8-year-old domestic shorthair cat, had become constipated in the past few months. His family veterinarian initially prescribed psyllium fiber (Metamucil). Then, a few weeks later, the vet prescribed methylcellulose fiber (Citrucel). Then a few weeks later, lactulose. Then a few weeks later, a high-fiber canned diet. Then a few weeks later, mineral oil and petrolatum (Laxatone). Then a few weeks later, dioctyl sulfosuccinate (docusate or Colace). Then a few weeks later, polyethylene glycol (MiraLAX). Then a few weeks later, cisapride was started. Then a few weeks later came canned pumpkin. Then a few weeks later Garfield received a low-residue diet. Garfield was hospitalized multiple times along the way to receive subcutaneous fluids. None of the above options worked well, so he had a few enemas along the way, as well. His owner spent hundreds and hundreds of dollars in total, and she became incredibly frustrated with the lack of results. Many months later, Garfield weighed 8 pounds. He technically was obstipated. He had been vomiting and had a rough hair coat, chronic tenesmus, and a poor appetite. He was dehydrated, anorexic, and experiencing pain. He was miserable. A subtotal colectomy finally was recommended. Sadly, our feline patient was a much worse anesthetic candidate than he was a few months ago. What happened? Megacolon in a 10-year-old cat with huge fecoliths. Feline megacolon is a progressive condition that invariably leads to irreversible distension of the colon. Two thirds of the time, we don’t know the cause of megacolon in cats, so it can be called an idiopathic, functional obstruction. It is believed that the cause is a degenerative neuromuscular disorder, which is ineluctable, irreversible, and untreatable. This is the reason why medical management is so often palliative at best. In some cases, megacolon is secondary to untreated pelvic fractures (and rarely a tumor or a foreign body), i.e., a mechanical obstruction. Simple radiographs and rectal examination under heavy sedation or anesthesia will confirm that the fracture malunion is indeed causing stenosis of the pelvic canal. Feces (fecoliths) in a megacolon are large and rock hard, and cannot mechanically move through a poor cat’s anus. Recall that one of the colon’s main jobs in life is to reabsorb water. So we can administer all the cisapride, lactulose, and special diets in the world—that poop is just not coming out. And then, there’s the dreadful enema. At best, it will help temporarily; at worst, it can cause traumatic tears of the colon. Either way, the smells and sights probably will make your toughest technicians sick to their stomachs. And it just doesn’t accomplish much, once the colonic distension has reached the point of no return. None of the medical options above provides a cure. In many case, they’re a temporary Band-Aid approach. Even cisapride, a prokinetic agent, can stimulate only those feline colonic smooth muscles that are functional. When the colon is overdistended, i.e., when a megacolon is present, cisapride won’t help one bit. However, in the vast majority of cases, megacolon is curable with surgery. Garfield finally goes to surgery After a thorough a physical and neurological exam, Garfield had a CBC, a biochemical profile, and a urinalysis. The results ruled out metabolic causes for constipation such as hypokalemia and hypercalcemia. Any patient who has been treated for hyperthyroidism also should have thyroxine levels checked to ensure that constipation is not caused by iatrogenic hypothyroidism. Presurgical preparation is important to improve the outcome. Food is classically withheld 12 hours prior to anesthesia. Access to water should be allowed to reduce the chance of dehydration. Broad spectrum, parenteral antibiotics, analgesics, and IV fluids are administered before, during, and after surgery. Garfield underwent a thorough laparotomy and a subtotal colectomy. His colon was the size of your forearm. During this procedure, 90 to 95 percent of the colon was resected, regardless of gross appearance. It is important to leave as little colon as possible—just enough to allow for anastomosis without any tension along the suture line. Failure to remove enough of the colon can lead to a recurrence of the megacolon, as it is a progressive disease. The colon separates nicely into two layers, which allows for a double layer closure. The colon is emptied and sent for histopathology to rule out inflammatory bowel disease or cancer. Removal of the ileocolic junction is avoided, unless it is necessary to avoid having tension along the anastomosis. The ileocolic valve is responsible for allowing small intestinal contents to pass into the colon, without allowing reflux of colonic bacteria. Removal of the valve causes reflux of colonic contents, which results in small intestinal bacterial overgrowth (SIBO). Studies have shown that patients who had ileocolic junction resection had significantly looser stools than those who in which the one-way valve was preserved. These patients go from being obstipated to having chronic diarrhea, which typically improves over time as the intestine adapts and a source of fiber is provided. Food and possibly an appetite stimulant are offered as soon as possible post-op. In good, experienced hands, complications are rare. However, they are possible, including colonic leakage, peritonitis, stricture, ischemic necrosis, and abdominal incision dehiscence. Garfield went home two days after surgery. The next follow-up occurred after four weeks of strict confinement. He was a happy, purring, comfortable cat with a great appetite and a new lease on life. So please remember: Megacolon does not have to be a horrible, chronic, debilitating nightmare. It can be a curable disease with early surgical intervention. MEGACOLON UNKNOWNS, MISTAKES, AND MISCONCEPTIONS Cats should never receive an enema during the preop period. Otherwise, it dramatically increases the risk of fecal leakage during the anastomosis. Fibers may help in the early stages of idiopathic megacolon when the colon still has some ability to contract. But in the later stages, fiber supplementation may worsen distention and subsequent symptoms. Misoprostol, ranitidine, and nizatidine have shown positive effects in vitro on feline colonic smooth muscle contraction. In vivo studies have yet to confirm whether they are a good option for treating idiopathic megacolon. Erythromycin has no effect on feline colonic smooth muscle; therefore, is it not indicated in the treatment of feline constipation, obstipation, or megacolon. Metoclopramide and domperidone enhance gastric motility, but they have no effect on colonic transit times, therefore making them useless for megacolon. It is important to inform cat owners to never use over-the-counter enemas, even infant enemas, such as Fleet (sodium phosphate), which can be toxic to cats. Using daily bisacodyl (Dulcolax) long term is not recommended because of potential injury to nerves cells in the colon (myenteric neurons). Dr. Phil Zeltzman is a board-certified veterinary surgeon and author. His traveling surgery practice takes him all over Eastern Pennsylvania and Western New Jersey. Visit his websites at DrPhilZeltzman.com and VeterinariansInParadise.com. Kat Christman, a certified veterinary technician in Effort, Pa., contributed to this article.
