The condition you describe is called gastrointestinal stasis. Basically its intestines have shut down and it cannot process food. When it gets this bad is usually not reversible. In your case I think you are dealing with some kind of obstruction.
If it is a foreign object obstructing the bowel there really isn't much you can do. If the obstruction is caused by gas in the intestines causing twisting of the gut it could be a surgical condition especially if the tissues of the bowel have been compromised from poor circulation.
Stasis can start when a chinchilla stops eating. Common causes are malocclusion of the teeth causing eating to become painful, which should show up on the xray. If you have a copy of the x-ray feel free to post it or e-mail it to
admin@chinchinchillaclub.com and I can take a look at it. Malo isn't that difficult to spot on a good radiograph when it bad enough to cause anorexia. Sometimes it's pneumonia or some kind of respiratory infection although usually with those cases I think it's usually from a bad reaction to the anitbiotics used to treat it but drainage can cause the animal to stop eating if it is severe. I would think the veterinarian would have observed this and observed lung sounds indicative of infection. It could be some kind of parasitic infection. Worms or parasites can in some extreme cases obstruct the bowels. More likely it causes diarrhea and irritation, which leads to stasis, which leads to bloat, which leads to obstruction.
If it is now at the point where distention of the stomach is interfering with breathing and there is no improvement after 24 hours I am going to recommend euthanasia but it is entirely your call. Syringe feeding is the right thing to do to attempt to keep him alive. Water and nutrients in the critical care can be absorbed through the stomach, however, if the intestines aren't flowing, and the animal is pain, its health will deteriorate.
I also recommend a few drops of simthecone with each dose of critical care, which is an OTC medication for infants to help with gas. You can also try to flip your chinchilla over on its back and massage its belly to try to stimulate flow of the intestines after each feeding. Be very gentle and do not bruise your chinchilla's abdomen.
I'm sorry you're going through such hard times. I don't want to you keep your hopes up because I don't think there is much of a chance for this one. These are very serious symptoms and this is a somewhat common problem that I come across on the boards. Without being able to identify or treat the underlying cause that makes it all the more difficult to treat.
Chinchillas should have a fairly constant flow of bowel movements. 24 hours without fecal output indicates something is seriously wrong and should be treated as an emergency. That is partly because whatever caused stasis or anorexia happened some time prior to that event and mostly because the intestines are designed to flow constantly in chinchillas and complications like bloat subsequent torsion can be irreversible if not caught early. When catching it early syringe feeding often reverses it depending on the cause.
Bowel obstructions from foreign objects can be caused by ingestion of plastics from cage accessories, artificial paper bedding or super-absorbent bedding, and sometimes cloth materials like fleece cage accessories. If you have these accessories and observe your chinchilla damaging or chewing them they should be removed. Health problems like malocclusion or respiratory infections can be monitored by weighing your pet regularly, about once a week, and looking for downwards trends of 20% or greater. This should prompt a vet visit. Measuring water is good practice as well. Just rubber band a ruler to the bottle and reset it each morning. Typically when a chinchilla stops drinking on it's own it's pretty far gone but it's a good check to making sure your bottle is dispensing.
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