DogsVitalSigns

As your dog grows older, the muscles of the colon and rectum may lose some of their ability to propel and expel feces adequately during a bowel movement. Reduction in stomach and intestinal digestive secretions can produce a bulkier, firmer stool as can diets very high in dry food content if there is insufficient water intake. Your dog will squat and strain to force the fecal mass slowly out. She may cry from the discomfort.

Prostatic disease can mechanically cause constipation as the prostate gland enlarges and presses up against the floor of the rectum. Similarly, tumors in the rectum or on the anus can interfere with the passage of feces. Any dog may have an isolated difficult bowel movement on occasion. This should be no cause for alarm if he is otherwise in good health and there is no bleeding or excessive pain.

Repeated bouts of constipation can slowly stretch the rectal muscles, causing permanent dilatation and resulting in chronic constipation. Once this occurs, your dog will need frequent enemas as well as fecal softeners to help him eliminate. The increased time the stool remains in the colon and rectum will allow bacteria that normally live there to act on the stool, causing putrefaction and excessive gas production...