my cat keeps getting constipated and straining when he poops

Colleague,

Recurrent constipation in cats can be a frustrating cycle. Let's break down a systematic approach to get ahead of it. My primary goals are to rule out underlying causes, establish effective initial deobstipation, and create a sustainable long-term management plan.

1. Diagnostic Workup:
Before we can manage it long-term, we need to rule out contributing factors.
* Minimum Database: A complete CBC, chemistry panel, and urinalysis are essential. I'm particularly focused on ruling out dehydration, azotemia (indicative of CKD), hypokalemia, and hypercalcemia, all of which can impair colonic motility.
* Physical & Rectal Exam: A thorough abdominal palpation is a given, but a careful rectal exam under sedation can reveal pelvic canal narrowing (from a previous fracture), strictures, or masses that are easily missed.
* Abdominal Radiographs: This is non-negotiable. We need to confirm the degree of constipation and assess for megacolon. The classic radiographic criterion for megacolon is a colonic diameter greater than 1.5 times the length of the L5 vertebral body. Rads also help screen for obstructive lesions or spinal abnormalities.

2. Management Strategy:

Acute Deobstipation:
* If the cat is impacted, rehydration is the first step (IV or SQ fluids).
* Once hydration is addressed, medical deobstipation can be started with osmotic laxatives (lactulose, polyethylene glycol 3350/Miralax) and lubricating agents.
* Manual deobstipation under general anesthesia is often necessary for severe cases.

Chronic Management:
* Dietary: The cornerstone is increasing water intake. Transitioning to an exclusively canned, high-moisture diet is critical. The role of fiber can be patient-dependent; some respond to high-fiber diets, while others do better on highly digestible, low-residue diets.
* Medical:
* Laxatives: Daily Miralax (1/8 to 1/4 tsp PO BID mixed in food) is often my first choice due to its palatability and efficacy. Lactulose is also effective but can be less palatable for some cats.
* Prokinetics: If there's evidence of impaired motility without obstruction, cisapride is the go-to prokinetic for the colon. It requires compounding but can be very effective.

If the patient has confirmed megacolon and becomes refractory to medical management, a subtotal colectomy is the definitive treatment and should be discussed with a board-certified surgeon.

Let me know what you find on your initial workup. The renal status and radiographic findings will be key in guiding our next steps.

Working hypothesis only — need more data.

Best,
Dr. Elena Vasquez, DVM, DACVIM

Colleague, constipation is a frustrating one to manage. From a nutritional standpoint, my approach always starts with hydration and fiber, as these are the two pillars we can most effectively control.

First, let's look at water intake. This is the single most critical factor. If the cat is on any dry kibble, I would transition him to an exclusively canned, moisture-rich diet. The goal is to increase total daily water intake, which softens fecal material from the inside out. This is far more effective than simply providing more water bowls, though things like water fountains or adding a tablespoon of water to each meal can also help.

Second is fiber strategy. We have two primary paths here:

Low-Residue Diet: In some cats, especially those with painful defecation, reducing fecal volume with a highly digestible, low-fiber diet can provide relief. This is less common but worth considering if fiber supplementation fails.

Fiber Supplementation: This is the more traditional route. I strongly prefer soluble fiber, like psyllium husk (e.g., unflavored Metamucil), over insoluble fiber sources. Soluble fiber forms a gel, retains water in the stool, and promotes motility without the excessive bulking that can sometimes worsen the problem in a dehydrated patient. I'd start with 1/4 to 1/2 teaspoon mixed into each meal of canned food.

There are also several excellent therapeutic GI diets formulated with a blend of soluble and insoluble fibers that can be very effective.

Of course, this all assumes we've addressed any underlying medical causes. Elena will likely want to ensure we've ruled out comorbidities like CKD causing dehydration, or hypokalemia which can impair colonic motility. But starting with a diet change to 100% canned food and adding a soluble fiber source is a safe and often highly effective first step.

Let me know the current diet and I can give more specific guidance.

— Dr. Yuki Tanaka 🥗