Constipation is a condition where bowel movements are infrequent and is a common problem of captive bearded dragons and other reptile species. There are many potential causes, including weakness, pain, spinal injury, or muscle weakness from nutritional secondary hyperparathyroidism, lack of sufficient water or roughage (dark leafy greens), folliculogenesis (maturation of eggs in the female reptile’s ovaries), parasites (coccidia or flagellated protozoans), atadenovirus infection, masses blocking the colon (such as with microsporidiosis), or renomegaly (large kidneys). Ingested substrate (such as sand, Sani-Chips, cypress mulch, crushed walnut shells or coconut coir) can also build up slowly and obstruct the colon.
Often, a lack of appetite is present when reptiles are in this condition. There are many causes of constipation in reptiles, but one of the most common is a solid urate mass in the cloaca that can cause colon and cloacal obstruction, leading to constipation. In most reptiles, urine is produced as a semi-solid uric acid salt, known as urates, while in mammals’ urine is produced in the liquid form of urea. Urates are made up of a suspension of uric acid salts and water and can be seen as the white or whitish-yellow semi-solid portion of the feces.
How does urine, in whatever form, cause a problem with reduced bowel movements? Reptiles do not have a separate opening for urates and feces to pass from the body; instead, they have a cloaca. The cloacal opening, most commonly called the vent, is located on the underside of the reptile's tail. The cloaca receives feces from the colon, urates from the kidneys, and eggs and babies from the oviduct. Then all these products pass out of the body through the cloacal opening.
A mass of urates can occur in any reptile species, but we will discuss this in bearded dragons as this is one of the most common reasons for taking these lizards to the veterinarian.
Your veterinarian will take a detailed diet and husbandry history about your bearded dragon and will perform a physical exam. In many cases, the information from the history and the exam will suggest constipation from a urate plug. The urate plugs are located just inside the opening to the vent on the underside of the tail, where feces pass from your dragon. This urate mass blocks the feces from passing out of the cloaca and causes feces to build up in the colon, forming a fecal mass. When feeling the stomach, there will often be a firm, cylindrical fecal mass in the colon that your veterinarian can detect. A complete blood count and biochemistry panel, and X-rays may be taken to confirm the diagnosis.
Treating the majority of colon obstructions caused by a urate plug is relatively simple. Your veterinarian will help to rehydrate the animal by soaking in lukewarm, shallow water for 30 minutes to 2 hours, or may give some fluids by injecting them under the skin, usually called subcutaneous fluid. If the bearded dragon is severely dehydrated, your veterinarian may give fluids into the bone canal (the hollow center of a bone) of the shin, which is known as intraosseous administration.
Some dragons will be able to pass the urate plug and then defecate on their own just from the bath. Others will pass the urate plug and defecate when stimulated by your veterinarian after using a lubricated swab or catheter, which is barely inserted past the cloacal opening.
More commonly, once rehydrated, the majority of lizards will need an enema to help them pass the urate plug and be able to defecate. Your veterinarian will insert a lubricated red rubber catheter or a ball-tipped feeding syringe into the cloaca and gently flush it with warm water. After the warm water flush, the lizard is placed on the ground and will usually pass a mucus-coated, hard, white-to-yellow mass of urates in a few minutes. This will often be followed by a large amount of feces. Your veterinarian may examine the feces under the microscope to look for organisms that build up from constipation. These organisms are not the cause of the constipation but a result of a build-up of organisms because they cannot be eliminated from the body due to constipation. In high numbers, they may cause infection. These organisms can be treated with the antibiotic metronidazole.
Urates are not stored in the bladder because the bladder of bearded dragons is small for their body size. Instead, the urate/water suspension is sent for storage to the lower portion of the colon, near the cloaca. The colon's job is to absorb water to help the dragon stay hydrated. This function helps to form the normal firmness of bowel movements you see from your dragon. Any material that remains for too long in the colon will have more and more water absorbed from it, until it becomes a very hard mass that is difficult or almost impossible to pass out of the body. This is what happens to the urate suspension stored in the colon. Due to some husbandry errors (discussed below), normal bowel movements are reduced in number and the colon absorbs too much water from the urate suspension, causing the formation of a hard mass (urate plug) that leads to a fecal build-up in the colon.
There are five key husbandry errors that may cause a reduction in bowel movements and the urate suspension to become a hard mass, leading to obstruction and constipation.
First, captive dragons are often in a state of undetectable, chronic dehydration because of the misunderstood needs of a desert lizard for water. Some dragons aren’t given the amount of water that they need to be healthy. This lack of enough water leads to the dragon being dehydrated, which reduces the muscle movement of the colon (but not the ability to absorb water). This, in turn, affects the frequency of bowel movements, which allows the colon to absorb too much water from the urates suspension, turning it into a hard urate plug.
Four errors that decrease the frequency of defecation and thereby increase the length of time that water can be absorbed from the urate fluid are:
- low temperatures in the basking area;
- insufficient amounts of vegetables and greens so there is not enough roughage in the diet to promote regular defecation;
- insufficient exercise;
- and overfeeding that leads to obesity.
Your veterinarian can help you manage these dragons’ constipation at home, discussing with you corrections to the husbandry errors discussed above. Soaking in warm water for 30 minutes daily for seven days and then going to a routine soak every two to four days will keep the dragon hydrated and stimulate regular defecation, as will an appropriate amount of water in the diet. In some cases, assisted feeding (feeding by a tube) every three days of the daily high-fiber diet (see #2 above) may help with regular defecation.