Constipation and Straining to Defecate in Dogs

Key Takeaways

Constipation is characterized by difficulty defecating with the resulting feces being dry and hard.

• This symptom is slightly different from tenesmus, which is straining to defecate with an empty or irritated colon, however both of these symptoms appear similarly to pet owners

• Constipation is an uncommon symptom indicative of various conditions affecting a dog’s mobility, ability to move stool through the intestinal tract, or causing dehydration

• Veterinary consultation is advised any time a dog is straining to defecate

• Symptoms often observed alongside constipation include lethargy, vomiting, lack of appetite, and abdominal swelling

• Diagnostics involve physical exam, lab tests, and possible imaging

• Treatment for constipation typically involves immediate relief as well as follow-up care for the underlying cause

A Closer Look: What is Constipation in Dogs?

Constipation ranges from a temporary symptom to a chronic one, potentially resulting in obstipation. Obstipation is defined as constipation that is resistant to treatment with the animal fully unable to defecate or pass gas without assistance. Obstipation typically requires invasive veterinary treatment performed under anesthesia, whereas constipation can commonly be treated with less invasive methods such as dietary changes, fluid therapy, medications, and enemas. Prolonged tenesmus with an empty colon may lead to conditions such as rectal and anal prolapse.

It is common for a dog to go 2-3 days without having a bowel movement after: 

• General anesthesia/surgery

• A major injury

• An upset stomach with vomiting, diarrhea, or appetite loss

This is not classified as constipation as long as the dog isn’t straining.

Possible Causes

Constipation is associated with many conditions that can be categorized according to whether there is impact to overall mobility, motility or structure of the intestines, and dehydration.

Conditions affecting mobility include

• Obesity • Arthritis • Previous injuries, particularly pelvic fractures • Rickets • Swimmer syndrome

• Tick paralysis • Reluctance to defecate due to stress or fear • Pain

Intestinal motility or structural conditions include 

• Sudden dietary changes • Megacolon  • Medication side effects • Hernia • Bacterial infection

• Parasitic infection • Vitamin B1 (thiamine) deficiency • Dysautonomia • Inflammatory bowel disease

• Pancreatitis • Peritonitis • Injuries of the spinal cord or structures surrounding the colon

• Intussusception • Foreign body obstruction • Fecal impaction • Intestinal torsion • Sublumbar lymphadenopathy

• Prostate enlargement (inflammation, hyperplasia, cancer) • Intestinal or anal deformities

• Spinal cord deformities, disease or lesions

• Cysts/tumors/cancer of the bowel, nervous system or adjacent structures

Conditions that lead to dehydration-associated constipation include:

• Chronic kidney disease • Acute renal failure • Cholangitis• Amyloidosis • Toxicosis/poisoning

• Hepatitis • Hypothyroidism • Hyperparathyroidism • Diabetes mellitus • Portosystemic shunt

Risk Factors

Constipation is not common in dogs, and is a secondary symptom of a wide range of conditions. Veterinary consultation is recommended to ascertain the cause of straining to defecate. If symptomatic treatments are used without addressing the cause of constipation, the pet will most likely become constipated again. The cycle of relief and return of symptoms has the possibility of exacerbating the condition. If constipation is due to kidney disease or cancer, prolonged delay in treatment can lead to less favorable outcomes.

If constipation is present with other symptoms such as severe pain, a hard, distended abdomen, breathing difficulties, pupillary changes, blood in the urine or stool, pale gums, seizures, sudden difficulties with walking, or fever, immediate medical attention is necessary.

Testing and Diagnosis

Treatment varies widely and are divided by options that provide immediate relief, and those intended to treat underlying conditions causing constipation. Constipation will return if the cause is not properly addressed.

Diagnostic procedures include;

• Physical exam, including rectal exam

• Diagnostic imaging, including colonoscopy

• Fecal sample testing

• Neurologic exam

• Blood work

• Urinalysis Treatments for immediate relief include;

• Dietary changes

• Bathing if matting due to inability to groom is contributing

• Enema

• Surgical intervention, including removal of fecal impaction or foreign body and De-obstipation

• Medication (stool softeners, laxatives)

• IV fluids

Additional procedures and treatments for the underlying condition causing constipation include;

• Biopsy

• Spinal tap

• Colectomy

• Nutraceuticals

• Exercise

• Physical rehabilitation

• Administration of condition-specific antidotes/antiserums

• Chemotherapy and radiation

• Dialysis

Similar symptoms

Straining to urinate is commonly confused with constipation. A blocked urethra, urinary tract infection, inflamed intestines due to diarrhea, cancers of the urinary system, or kidney stones can all cause straining in a defecating position. 

False constipation, also known as pseudocoprostasis, also presents similarly to constipation. It occurs more commonly in dogs with mobility problems due to age, injury, or obesity. As a result of an inability to groom, hair and fecal matter can become matted leading to a blockage of the anal region. This matted region also carries the risk of becoming infested with maggots if not treated.

Associated Symptoms

Constipation alone is often seen with the following symptoms;

• Passage of firm, dry feces • Thin, ribbon-like fecal shape • Putrid smelling feces • Lethargy

• Lack of appetite • Vomiting • Hard abdomen • Swollen abdomen

Constipation due to more serious conditions is accompanied by a myriad of other symptoms which are associated with the underlying condition.