Overfed, underactive snakes are prime candidates for constipation. Some snakes that are fed frozen and thawed food items tend to become dehydrated as a consequence of fluid loss in prey items during the freeze thaw cycle. Other fac-tors that can contribute to constipation are cooler temperatures and lower humidity than the snake is used to. Cooler air temperatures can cause a snake to "hug" its heat source; by doing so, the inactive snake essentially "cooks" the stool in its colon for several days, thereby drying it out and making it more difficult to pass. Lower cage humidity increases the rate of evaporative water loss even more and worsens an already serious situation. Without any intervention, the snake's stools may become as hard as rocks, which is why they are called fecoliths (fecal stones). Chronic constipation (formally, obstipation, noted by hard stools every three to five days) may result in quite a backup, especially as many snakes continue eating even when constipated.
There are a number of treatments for constipation. The first and most important action is to correct the environment. Eliminate drying substrates, such as corncob litter. Wood and cardboard fixtures are also very drying and thus should be removed from the cage. Avoid using cages with sides made of untreated wood as these types may also dry out the air within the cage. Other treatment options to consider include using a humidifier, increasing the size of the cage and providing additional accessories to encourage exercise, or reducing the frequency of feeding or feeding smaller and more digestible items. Renowned reptile veterinarian Steven Divers (pers. comm.) suggests that injecting water into frozen and thawed prey items may be helpful. The next step in treating constipation is to try several warm water soaks. Placing the snake in shallow, warm water for fifteen minutes per day for three or four days will usually cause it to defecate. If not, an enema of warm water or of a very dilute solution of dioctyl sodium sulfosuccinate (DSS) will likely work. Frye (1991) quotes PaulMurphy and colleagues (1987) in advising that DSS be diluted at a ratio of one part DSS (standard stock solution) to 20 parts water if the solution is to be administered through a stomach tube. Frye also advises the use of magnesium oxide (milk of magnesia) suspension or mineral oil in small amounts as aids for constipation. One mL/kg of body weight is a safe dose for milk of magnesia.
A small quantity of mineral oil (1 mL/kg of body weight) administered through a stomach tube has long been recommended and, indeed, does seem to work. However, the administration must be made by someone experienced in tubing reptiles as the improper placement may lead to regurgitation as well as aspiration of the oil and result in pneumonia. One means of administering the mineral oil that we have found successful has been jokingly referred to by the senior author as "mouse lax" or "rat lax:" Basically, if a snake is still feeding, you can offer a prekilled mouse or rat that has been injected with the appropriate dose of mineral oil. Several days later, when the mouse or rat is digested, the oil is released and softens the stool; defecation occurs within several days to a few weeks.
If the above approach proves unsuccessful, surgical removal of the fecoliths is necessary. However, the best approach to this problem is prevention. Avoid overfeeding your snake, provide it with as much room as possible, and maintain appropriate temperature and humidity ranges. Although some sources have suggested that routine handling may be good exercise for the snake, remember that some animals do not tolerate handling very well.