The longer feces remains in the colon, the more water is reabsorbed from it and the drier and harder it becomes. This in turn makes it harder to expel the motion. Build-up of feces in the rectum and colon can be toxic. A constipated kitten may have a hard, distended or tender abdomen. If it strains to defecate this can cause prolapse of the anus.
Normal kitten feces has the consistency of toothpaste and is easily passed. If it becomes more solid, the kitten strains to pass bowel motions. If a kitten has not had a bowel motion for 48 hours, a small dose of liquid paraffin or a feline laxative (e.g. Katalax) is needed. Dosage for liquid paraffin is approx 0.5 ml per feed during the next 48 – 72 hours, less if bowel motions return to normal earlier. Liquid paraffin is not suitable for young kittens as it can irritate the intestine. Working a small pat of warm Vaseline (or equivalent white petroleum jelly) into the anus often acts as a gentle suppository. Recurrent or persistent constipation requires veterinary treatment e.g. a glycerin enema.
Dehydration is a common cause since this causes hard, lumpy bowel motions. Underlying dehydration must be corrected. Another cause may be the mother’s failure to stimulate defecation. She can be encouraged to lick the anal area by smearing it with a little meat jelly or similar.