There are many reasons your dog may be constipated, from diet to medical conditions, to eating something they shouldn’t have and causing a blockage. However, these are other common causes of constipation in dogs:
Unfortunately, many dogs simply do not get enough moisture in their food, or drink enough water, and this lack of fluid leads to dry and hard stools, resulting in constipation.
Excessive/matted hair around the anus
Long-haired dogs can become matted, especially round the tail and anus area. These dense clumps of hair can actually block the pathway if not removed, contributing to the potential for constipation. Regular grooming and trimming the area should help to prevent this.
Certain medical conditions
Various medical conditions contribute to constipation in dogs, and some others mimic it quite convincingly. IBS, intestinal inflammation, damage to the spinal cord (from tumours, injuries, etc.), and prostate issues in males  are all examples of medical conditions that can cause constipation in dogs.
Anal gland issues
Another cause of constipation in dogs can be issues pertaining to their anal glands. These can become inflamed, blocked, or even afflicted with abscesses and tumours in some cases, which would certainly make bowel movements more difficult .
As dogs age, and become less mobile, it’s more common for constipation to occur due to natural changes in the digestive tract. Especially those dogs that are fed a processed food diet or don’t get as much exercise as they used to. However, if your ageing canine is experiencing constipation, there are still ways you can help. See more on how to help dogs with constipation below.
All dogs are not created equal, and that goes for their digestion, too. Even a dog who is fed a species-appropriate, raw food diet can have issues with constipation, which is likely due to their meals not being precisely balanced for their unique digestive needs. Common culprits are lack of fibre and excessive bone content, both of which could potentially cause dogs constipation.
Like humans (and most species, for that matter), stress can have a negative impact on your dog’s gut. Stress hormones prepare the body to defend itself or to escape, shutting down non-essential processes, such as digestion, making stress a potential cause of constipation in dogs.
Medications are another potential cause for constipation in dogs, as they often create imbalance in the gut and digestive tract. Often, giving medication with food will help to combat this, but not in all cases. Supplementing with a canine-specific probiotic, like ProDog’s Probiotic paste, can help dogs on medication with any acute gut issues.
Various food items
Dogs are experts at getting into the things they shouldn’t, which means they sometimes eat foods that don’t agree with them. Some of these items (e.g. stones, sticks, corn on the cob, cooked bones etc.) can upset their digestion or even cause obstructions in their intestines, resulting in vomiting, diarrhoea, and constipation.