Constipation and Straining to Defecate in Cats

Key Takeaways

Constipation is straining to defecate when the colon is full. Constipation is not to be confused with diarrhea which may cause straining to defecate when the colon is empty and irritated.

• Constipation is characterized by the passage of small, dry feces

• This symptom is common in cats and often becomes more frequent with age

• It may present with lethargy, loss of appetite, vomiting, and blood in the stools

• Most commonly associated with diseases of senior cats that lead to dehydration, like chronic kidney disease and hyperthyroidism, but occurs with a variety of other conditions

• Any initial episode of constipation must be treated as an emergency

• Symptomatic therapy includes laxatives, enemas, and fluid therapy

• Treatment of the underlying condition is critical for preventing recurrence

• Constipation often leads to severe complications in cats such as obstipation and megacolon

A Closer Look: What is Constipation in Cats?

Constipation is common, particularly in older cats. It indicates an underlying illness that interferes with the normal passage of stool, often as a result of dehydration. Treatment allows for the stool to pass or be removed, but recurrence is expected unless the underlying condition is corrected. In some cases, constipation can develop into  chronic difficulty defecating. Veterinarian investigation is warranted immediately, especially if other symptoms appear, like weight loss, blood in the stools, loss of appetite, or lethargy.

Possible Causes

Constipation occurs as a result of many conditions including:

• Megacolon • Kidney injury or disease, renal failure • Hyperthyroidism • Diabetes mellitus • Hernia

• Tumor/cancer • Bacterial infections

Constipation can also be an indicator of a condition that affects the animal’s mobility such as:

• Obesity • Arthritis • Injuries

Neurologic conditions may interfere with the normal passage of stool: 

• Malformations in the spinal cord (common in Manx cats) • Dysautonomia

• Idiopathic megacolon

Constipation may occur as a side effect with some medications. 

Sometimes constipation is caused by something as simple as matted or dirty fur blocking the anus. It can also occur following ingestion of a large amount of indigestible material, leading to GI foreign body obstruction.

Some cats become constipated in response to major stressors like being boarded or hospitalized.

Risk Factors

Depending on the duration of the symptom, the severity may vary.

In mild cases, it might be a symptom of dietary issues or dehydration. Drinking more water or consuming high-fiber foods or medications (e.g. laxatives) may lead to a quick recovery.  If the constipation is severe or chronic it is necessary to consult a veterinarian as it may develop into more serious conditions such as megacolon or obstipation.

Testing and Diagnosis

There are a variety of tests to determine what is causing constipation as well as the underlying condition leading to it, including: 

• Physical examination, including a rectal exam • X-ray or ultrasound  • Blood work

Once the root cause is determined, removal of the fecal mass is often the next step, either via enemas or laxatives. In case of dehydration, the next step is intravenous fluid therapy.  To relieve constipation laxatives and stool softeners may be prescribed. Nutritional therapy is also important. Failing to address the primary source of constipation will likely lead to recurrence, which often develops into more serious complications over time. In severe cases (e.g. megacolon) it may be necessary to surgically remove the affected portion of the colon.

Similar symptoms

Constipation is often confused with straining to urinate. Diarrhea can also cause difficult or painful evacuation because the colon is empty and irritated.

Associated Symptoms

• Lethargy • Blood in the stools • Loss of appetite • Weight loss • Vomiting • Excessive thirst 

• Excessive urination