Many conditions can cause constipation, as can medications (including opiates, diuretics, antacids and anticholinergics). In dogs, ingestion of stones, gravel, sand, soil or bone can result in constipation. In cats, hairballs are frequently associated with constipation. In young orphaned kittens, lack of perineal stimulation can lead to constipation. Perineal hernia, perianal fistulas, anal gland abscesses, foreign bodies and some types of orthopaedic surgery pose risks of constipation due to pain experienced during defecation. Poorly consolidated pelvic fractures can reduce the diameter of the pelvic cavity and obstruct the colon, causing constipation.
The colon is innervated by the parasympathetic nervous system and by the intrinsic myenteric and submucosal plexuses. Damage to one of these nerve pathways impairs colonic motility and contributes to constipation. Dehydration and electrolytic imbalance (especially hypokalaemia) can lead to constipation. Dehydration promotes absorption of water from the colon, leaving a hard, dry faecal mass. Electrolyte imbalances disrupt the activity of muscles in the colon, leading to constipation.
Constipation can also result from a mechanical obstruction due to an intra- or extraluminal mass or rectal stenosis. Some neurological disorders can reduce colonic motility, e.g. cauda equina syndrome, autonomic dysfunction, diabetic polyneuropathy or hypothyroidism.
There are also several aggravating factors: lack of exercise, a low-fibre diet, obesity, changes of environment, prolonged stays at the vet’s and general anxiety. Severe chronic constipation or neurological disorders can cause megacolon, which means the colon is persistently greatly enlarged and loses its motility. Affected animals suffer from painful defecation, abdominal pain, weight loss, loss of appetite, vomiting, depression and poor coat condition. Cats are more prone to megacolon than dogs. Siamese cats have a congenital form associated with the absence of ganglion cells in the myenteric and submucosal plexus.
Constipation is a significant risk factor for bowel cancer in humans and possibly also in pets.
In cats, grooming serves several purposes. It is a way for them to clean their fur, regulate their temperature, reduce stress and create social bonds (in the case of mutual grooming). A cat’s tongue is covered in backward-facing spines called papillae that act like a brush, helping the cat to remove dead hair and debris. By licking its body, a cat ingests between 30 mg and 70 mg of hair per kg body weight per day, which has to be eliminated in its stools. During a moulting period, this rises to 100 mg per kg body weight per day, which is a daily volume of 10 cm3 for a 4-kg cat. (TOURNIER & al., 2005)
The hairs coalesce in the digestive tract to form a ball, which is usually regurgitated. In some cases, however, the cat becomes constipated. This is a fairly common problem, judging by that fact that 50% of vets have had to deal with it. The formation of hairballs depends on individual factors related to the formation of retention pockets in the digestive tract and also on environmental factors. Cats that live indoors are more at risk, since they cannot hunt or eat grass and are sedentary. The same applies to cats that shed a lot of fur or groom themselves frequently.
The solution to prevent the formation of hairballs is to speed up intestinal transit, so hairs are gradually eliminated in the faeces, which stops them collecting in the stomach or intestine.
Management of the cause if possible.
Water is an essential nutrient for constipated pets. To encourage them to drink, provide water in several different places and with different flavours, give priority to moist foods, flavour the water with stock or meat juices and give them ice cubes as a treat.
Doctor Veterinary Medicine Estelle Lhoëst
POST-GRADUATE DIPLOMA in Nutrition | University Degree in Herbal Medicine and Aromatherapy