The diagnosis of “hairball” or “wool block” is commonly made in rabbits. Unfortunately this is not an accurate description of the real problem the rabbit is experiencing. By using the term ‘hairball’ the true nature of the disorder is disguised and frequently goes untreated. The problem is not an accumulation of hair in the stomach, but rather a decreased motility (movement) of the gastrointestinal (GI) tract leading to the dehydration and impaction of the material in the stomach and sometimes also the cecum. A more accurate term for this condition would be gastric stasis and if it occurs in the cecum, cecal stasis. This means the stomach or cecum has stopped moving material out into the intestinal tract. How does this condition occur? We need to review some facts about the rabbit GI tract in order to understand the process that leads up to this disease.
GASTROINTESTINAL TRACT FUNCTION
Rabbits are strict herbivores. Their relatively small body size makes it difficult to store large volumes of coarse fiber as might be done in the cow or horse. The GI tract attempts to eliminate fiber as quickly as possible. Large indigestible fiber particles stimulate healthy motility of the GIT. The rabbit GI tract then breaks down the digestible portion of the food to produce the nutrients that are needed for life, some of which are absorbed directly from the GI tract and some of which are eaten again in the form of cecotropes.
Food in the stomach is essentially sterilized, massaged a bit and broken down into smaller particles. It then moves into and through the small intestine where nutrients are extracted, and more water is added resulting in a fluid content. At the point where the small intestine flows into the large intestine is joined a large blind sac called the cecum.
In the cecum resides a specific population of bacteria and other microorganisms that break down the digestible portion of the gut content. Through bacterial fermentation, amino acids, fatty acids and certain vitamins are produced. Any changes in the delicate balance of the flora of the cecum can have disastrous results for the rabbit. Factors that can interfere with cecal function include a diet too high in carbohydrates and/or too low in indigestible fiber, toxins, some medications, dehydration, extreme stress and other systemic disease. Some of the nutrients produced in the cecum are absorbed directly thorough the wall of the cecum, but most are contained in cecotropes which are nutrient-rich “feces” that are passed from the cecum, through the large intestine to the outside. Rabbits know when these cecotropes are being excreted and eat them directly from the anus. Cecotropes are produced approximately 4 to 8 hours after a meal. When the cecotropes are digested, the nutrients are extracted and absorbed by the rabbit. Occasionally cecotropes are not eaten and can be seen in the toilet area. Cecotropes are irregularly shaped, greenish in color, coated with mucous and have a strong odor.
Waste feces are the hard, round, dry droppings found in the toilet area. These feces have a high fiber and low moisture content and do not contain any nutrients for the rabbit. Waste feces are produced during the first four hours after a meal.
Appropriate amounts of liquid are important in the rabbit diet to promote proper mixing and sorting of ingesta (intestinal contents) in the lower intestine and cecum. If a rabbit becomes dehydrated the ingesta becomes dry and impacted.
HOW GASTRIC STASIS OCCURS
The most common cause for gastric stasis is an inappropriate diet. As we can see from this brief discussion of the GI tract a healthy diet for a rabbit includes large amounts of both digestible and indigestible fiber, has a low to moderate carbohydrate level and contains adequate moisture. A diet consisting of grass hay and green foods works well. A diet of highly concentrated carbohydrates and low indigestible fat levels can promote abnormal GI motility. Commercial rabbit pellets, commercial rabbit treats and high carbohydrate foods such as grains and legumes are examples of dietary items that are too high in carbohydrates and too low in indigestible fiber. When rabbits are fed these foods the result is a slower than normal GI motility. Although diet is the most common cause of gastric stasis, any condition that changes GI tract motility can result in this disease. This would include chronic high levels of stress in the environment, postsurgical adhesions, ingestion of toxins or other foreign material, chronic dehydration (lack of access to clean water), painful conditions and dental disease (these conditions change eating habits), and other systemic disease that causes alterations in GI tract motility such as liver or kidney disease.
As the movement of material through the GI tract slows, the ingesta sits longer at any point, particularly the stomach and cecum and the body extracts more fluid than normal. This serves to dehydrate the ingesta, which causes further slowdown of GI motility in a vicious cycle. The result is dry impacted material in the stomach as well as the cecum, which ceases to move altogether. The rabbit then stops eating and drinking because nothing is moving and further aggravates the condition. Now we have a “ball” of material in the stomach that can be felt on a physical examination and seen on a x-ray. Dehydrated stomach contents viewed on a x-ray exhibit a “halo” of air demonstrating that there is little liquid present.
So where does the hair come from? Rabbits always have some hair in their stomach contents. They groom themselves constantly and swallow the hair. A true “hairball” is comprised of nearly 100% hair as in the cat or the ferret. In the rabbit, hair is mixed with stomach contents in a loose mass. As the stomach contents dehydrate as described above, the largest particles are left behind which includes the hair. The liquid stomach contents gradually turn into a solid tightly adhered mass. If you look closely at a ?hairball? you can see that it is made up of both hair and dried stomach contents. In a few rare instances, the longhaired breeds of rabbits, such as Angoras and Jersey Wooly’s, can develop excessive amounts of hair in the stomach. This is due to the fact that the hair is abnormally long. Humans have created this situation through the alteration of the genetics of our pets. In these species it is beneficial to brush the pet frequently to reduce the amount of hair eaten.
To sum it up, the cause of this condition is not the presence of hair in the stomach, but rather a GI tract motility disorder that results in firm material in the stomach and the cecum. If we do not correct the underlying problem, then this condition is destined to reoccur.
SIGNS OF GASTRIC STASIS
The following is a list of signs that are commonly noted with gastric or cecal stasis:
Rabbits will eat less over a period of days or weeks.
Eventually rabbits stop eating altogether.
The waste droppings become smaller, then stop altogether.
Often, these rabbits will be bright and alert for several days after they stop eating.
Rabbits will refuse to eat pellets but will chew the paper on the bottom of the cage, the woodwork or wall board which are all sources of the fiber they are craving,
Some rabbits have periodic soft, pudding-like stools prior to a complete loss of appetite.
As the condition progresses with further dehydration of GI contents and finally complete shut down of the GI tract, the rabbit becomes increasingly lethargic, depressed and ultimately can die.
It is important to note that with gastric stasis, the changes usually come on gradually. If complete intestinal obstruction occurs with dried ingesta or any other material, the signs are much more dramatic and require immediate veterinary attention. The signs of ingestion of a toxic substance may be similar.
Signs of intestinal obstruction or toxicosis
Rabbit suddenly stops eating
Depressed or lethargic, may be reluctant to move or appear bloated
Suddenly stops producing any stools
Rabbit may make grunting noises or continually grind the teeth in response to abdominal pain
Eventually the pet will go into shock and collapse
If you see any of these signs in your rabbit you should consider it a dire emergency and seek veterinary assistance immediately.
DIAGNOSIS OF GASTRIC STASIS
History and Physical Examination? The diagnosis of gastric stasis starts with a history of an inappropriate diet, often combined with inadequate exercise that only serves to compound the problem. The physical examination reveals a large, doughy mass in the stomach and possibly cecum. Rabbits are often overweight and may be slightly to moderately dehydrated.
Laboratory Testing ? A x-ray of the abdomen is useful to confirm the presence of dehydrated material in the stomach and/or cecum. In addition it can give clues to the health of the rest of the GI tract as well as other abdominal organs. Blood tests can give information on the health of the immune system, the level of dehydration and the condition of other organ function.
TREATMENT OF GASTRIC STASIS
Rehydration ? Rehydration (replacing fluid) is one of the most important things we can do to reverse gastric stasis. We need to rehydrate both the stomach and intestinal contents, but the rabbit itself. Rehydration is accomplished through the administration of oral and, needed, injectable fluids. If the rabbit is only mildly affected, simply offering fresh green foods can often provide enough moisture and indigestible fiber to get things moving again. For more severely affected patients, it is necessary to administer fluids either under the skin or in a vein in addition to oral fluids such as electrolyte solutions or fruit juices.
Gastric Motility Drugs ? There are several drugs that can be used to stimulate the stomach to start moving again. They can help to speed recovery time, but are discontinued after normal stools are produced.
Analgesia ? Some rabbits with advanced gastric or cecal stasis are in pain due to a buildup of gas in the GI tract. Pain medications are used in these cases to improve appetite and to reduce stress, which ultimately speeds recovery.
Diet ? It is important to administer oral, high moisture, high fiber foods to these patients in order to stimulate increased GI tract motility. If nothing is going into the system, then movement will not improve, even with medications. Initially, if the pet is not eating at all, foods such as canned pumpkin (not pumpkin pie filling), vegetable baby food or blenderized green foods can be administered with a syringe. A naso-esophageal tube can be placed in pets that will not accept syringe feedings. As mentioned previously, many rabbits start eating fresh green foods immediately when offered. Add to this grass hay and you need nothing else. For prevention of this disease, feed the pet a healthy diet of grass hay and green foods and remove commercial pellets and treat foods from the diet forever.
Not Useful ? Antibiotics do not need to be administered in uncomplicated cases of gastric stasis. In fact the inappropriate use of antibiotics may aggravate the condition. In addition there is no benefit to giving enzyme products to dissolve the hair. As discussed, the problem is not an accumulation of hair and these products do not dissolve hair anyway. If strong enzyme products are used in a rabbit with complete GI shutdown, there is a chance that they may erode through the lining of the stomach and create an ulcer. Please consult your veterinarian first before using any of these products.
Hairball is the fiction and gastric stasis caused by an underlying GI motility problem is the fact. Let’s stop using this antiquated term that only draws our attention away from the true nature of this disease. The best prevention for gastric stasis is a healthy diet, ample exercise and a clean and calm environment. With these factors in place you will save yourself and your pet a lot of pain, anguish and dollars spent on veterinary bills!
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