Gastrointestinal Stasis in Rabbits

Is it Really a Hairball Causing the Blockage?

By Laurie Hess, DVM, Diplomate ABVP (Avian Practice)

The term “hairball” has been used for decades to describe a syndrome in rabbits in which they stop eating, stop passing stool, and become bloated with gastrointestinal (GI) tract gas, fecal material, and dry mats of hair. The assumption was that the “hairball” was the cause of the slowing down or complete cessation of food movement through the GI tract. This is not true, however. The hairball actually is a result of, rather than the cause of, the problem.

兔子通常有一些胃肠道神经束的头发from grooming. With GI stasis, the problem is not an accumulation of hair in the stomach, but is instead decreased movement of food through the GI tract from a combination of decreased food intake, dehydration, and changes in the population of GI bacteria that normally ferment the food in a healthy rabbit’s GI tract. As a result, food and dehydrated mats of hair form an impaction, typically in the stomach and occasionally in the cecum (large intestine).

The more appropriate term for this condition is GI stasis (or cecal stasis, if the impaction is within the large intestines rather than within the stomach and small intestines).

Normal Rabbit Digestive Tract Function

To better understand how GI stasis occurs, you must understand how the normal rabbit’s GI tract works. Rabbits are herbivores, consuming only plant matter. Plants are made of both digestible and indigestible fiber. Rabbits digest fiber in their lower intestines and thus are referred to as hindgut fermenters. They use their large strong teeth to grind up greens and hay, which then pass down the esophagus into the stomach, where they are further broken down into smaller particles. These particles then pass from the stomach into the small intestines, where nutrients are extracted and water is added. The remainder of the ingested food then passes into the large intestine (colon).

On entering the colon, small digestible fiber particles and starch are separated from larger, indigestible fiber particles. These smaller particles and starch are then passed backward, up the GI tract into the cecum, a blind-ending sac that contains very specific bacteria, yeast, and other microorganisms that ferment these small digestible fiber particles into nutritionally valuable amino acids, fatty acids, and certain vitamins.

Some of the nutrients produced in the cecum are absorbed directly through the cecal walls, while others move into the rest of the large intestine (colon), where they then pass to the outside as nutrient-rich feces, called cecotropes, which the rabbit then re-ingests to obtain further nutrients. Cecotropes, typically passed 4-8 hours after a meal, are soft, green, often covered with mucus, and are more irregularly shaped than normal rabbit fecal pellets.

Larger, indigestible fiber particles bypass the cecum and move from the small intestine directly into the colon, where water is reabsorbed. There, they are made into the symmetrically-formed, dry fecal pellets with which rabbit owners are familiar and which typically are passed out of the body within four hours after eating. While these large, indigestible fiber particles do not contribute nutrients to the rabbit, they help promote normal motility of the GI tract and are essential for normal GI tract function.

The Causes for GI Stasis

One of the most common causes of GI stasis in rabbits is a diet too high in carbohydrates and fat and too low in digestible fiber. Greens and grass hay contain digestible fiber, while commercially available rabbit pellets typically contain high amounts of carbohydrate, and seeds and nuts contain high levels of fat. Rabbits eating large amounts of pellets or high-fat seeds and nuts have slow GI tract motility and often develop GI stasis as a result.

Other causes of GI stasis in rabbits include anything that causes a rabbit to eat less, including stressful environments, painful conditions of the mouth (dental problems and oral infections/abscesses), lack of access to water/dehydration, and the presence of other systemic illnesses, such as liver or kidney disease.

When rabbits eat less, the motility of the GI tract slows, the food within the GI tract sits longer than normal in the stomach and cecum, and the rabbit’s body extracts more water from the GI tract to make up for less fluid intake, leaving a mass of dried food and hair within the GI tract (hence the term “hairball”). Dry impacted material accumulates in the stomach and cecum, making the rabbit feel bloated and uncomfortable.

另外,胃肠道的pH值(或酸度)的变化, resulting in a change in the normal population of bacteria that ferment digestible fiber. Consequently, gas-producing bacteria develop, resulting in the build-up of painful gas in the GI tract, further contributing to decreased appetite and to the vicious cycle of GI stasis.

It is important to note that unless the rabbit has ingested a foreign object, such as carpet fibers, flooring, or baseboard, the lack of fecal production with GI stasis is not from a true physical GI tract obstruction but rather from a physiologic slowing down of GI tract motility.

How to Tell if Your Rabbit Has GI Stasis

Signs of GI stasis can occur suddenly or gradually. Typically, rabbits will eat less or stop eating completely. Their fecal pellets become smaller, drier, and eventually stop being produced. They may initially pass soft, pudding-like stools before their feces becomes small and dry.

Over a few days, rabbits that are not eating well get dehydrated, weak, and stop moving. Their stomachs may appear bloated, and they may grind their teeth from GI discomfort. When left untreated, these animals can die. Any rabbit owner who sees these signs in his or her rabbit should have the pet checked by a veterinarian as soon as possible.

What to Expect at the Veterinary Hospital

To figure out what the primary problem is (e.g., dental disease, inappropriate diet, etc.) behind the secondary GI stasis, your veterinarian will ask you several questions about what your rabbit eats and what signs you have noticed at home. The doctor will perform a complete physical examination on your bunny and will likely palpate (examine by touch) a firm, doughy mass in your rabbit’s stomach +/- cecum. The vet will likely take x-rays, which will show a larger than normal amount of food, fluid, and gas in the stomach +/- cecum with little to no food passing into the large intestines.

Your veterinarian also may want to run blood tests to assess your rabbit’s degree of dehydration and the health of critical organs such as the kidneys and liver. If your bunny is severely dehydrated and weak, the vet will admit the pet to the hospital to place an intravenous catheter for administration of fluids. The vet also will likely administer medications to treat the pain and to promote GI tract motility.

In general, unless the veterinarian feels that toxic bacteria have built up in the GI tract, resulting in potential life-threatening infection, antibiotics are not generally given, as they destroy normal and healthy GI bacteria along with the bad bacteria.

最后,由于胃肠道瘀通常不是由于build-up of hair obstructing the GI tract, the administration of enzymes (such as pineapple-based papain) to break down and digest hair is not warranted and is an antiquated and inappropriate treatment.

If the rabbit isn’t eating, the vet will syringe feed a commercially available liquid food formula, while still offering fresh greens and hay, until the rabbit starts eating on its own. Occasionally, rabbits will reject syringe feeding and refuse to swallow. These rabbits may need to have a tube placed through their nostrils and down into their stomachs to deliver liquid food.

The vet also will treat any identifiable underlying causes of GI stasis (such as sharp points on the teeth irritating the gums/tongue, chronic kidney failure, oral abscesses, etc.).

If the rabbit is only mildly dehydrated, the vet may administer fluids subcutaneously and send you home with oral medications and syringe feeding. The vet will also likely suggest that you encourage the bunny to move around and exercise to pass gas and to help re-establish normal GI motility. The vet also will likely make recommendations regarding an appropriate diet to feed at home (i.e., unlimited amounts of grass hay and greens with a very small amount of commercially available pellets, and no sugary treats, fruit, nuts, or seeds).

What to Expect When Your Rabbit Comes Home from the Vet

Once your rabbit comes home from the animal hospital, your vet will likely advise you to continue supplemental syringe feeding until your bunny is eating 100 percent normally on its own and its stools appear normal in size and number. You may also be asked to continue to administer anti-gas and GI pro-motility medications until your bunny’s appetite and stool production are normal.

In addition, your vet may recommend that you eliminate or significantly reduce your rabbit’s intake of high-carbohydrate pellets that can contribute to the development of GI stasis, and that you increase the amount of high-fiber grass hay and high-moisture greens in your rabbit’s daily feedings.

How to Prevent GI Stasis in Your Rabbit

The best way to prevent GI stasis in rabbits is to ensure that their diets contain a large amount of high-fiber grass hay and high-moisture greens, with a very small amount (no more than a quarter of a cup per 4-5 pounds of rabbit weight per day) of pellets — and no sugary or high-fat treats unless otherwise instructed by your veterinarian.

Since obese rabbits are more prone to developing GI stasis, encouraging your rabbit to get out of its cage to exercise will promote not only a healthy body weight, but also normal GI motility. In addition, ensuring your rabbit is drinking an adequate amount of water (by offering both a water bowl and a bottle, and by providing fresh greens) will help lessen the chance for GI stasis, particularly in hot weather, and will aid in keeping your bunny’s GI tract functioning properly all year ‘round.

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