Management tips for constipated cats

dvm360dvm360 April 2021
Volume 54

Treating constipated cats can frustrate many veterinarians due to the chronic, recurrent nature of the disease. Developing an effective management strategy can improve outcomes for these patients.

Constipated cats are presented commonly to veterinary practices. They can vary from mildly constipated and uncomfortable to severely obstipated and systemically ill at presentation. Case management can be frustrating due to the chronic nature of constipation and recurrent presentations. In a session at this week’s Fetch dvm360® virtual conference, Anthony Carr, DVM, DACVIM, a professor in the Department of Small Animal Clinical Sciences at Western College of Veterinary Medicine in Saskatoon, Saskatchewan, discussed an evidence-based, stepwise approach to managing these patients.

Why is this cat constipated?

Cats can present with constipation, obstipation, or megacolon, but the specific definitions of each term are not as clear-cut in feline medicine as in human medicine. Ultimately, Carr says, all these patients need both acute relief and a long-term management plan. The underlying etiology should be identified, if possible, although for over 60% of cats the condition is idiopathic.

Patients may present with vague clinical signs such as inappetence, diarrhea, and vomiting. Some owners may note a lack of stool in the litterbox or report that the pet is straining to defecate. Carr notes that many of these patients have some degree of dehydration, which often contributes to the constipation as the colon performs its normal function of resorbing water from the feces. This results in small, firm fecal material that is more difficult to pass.

On physical examination, firm stool is often palpable, although this can sometimes be challenging to feel in obese cats. The patient should be evaluated for pain in the perineal area (ie, an abscess), pain that prevents appropriate posturing (ie, chronic osteoarthritis or fractures), rectal strictures, and neurologic impairment.

Radiographs can be helpful in evaluating the severity of constipation and assessing for contributing factors such as osteoarthritis, pelvic fractures, extraluminal masses, and vertebral disease. Pelvic fractures and subsequent narrowing of the pelvis are often cited as predisposing to constipation, but in 1 study of cats with these injuries only 20% had constipation and none had megacolon.1 Additionally, the study found that the degree of narrowing was not related to the severity of constipation.

Bloodwork is recommended in all patients presenting with constipation to assess for concurrent diseases and determine patient stability. Most cats presenting with constipation are older and have concurrent diseases that can contribute to the degree of dehydration, such as hyperthyroidism, renal disease, or diabetes mellitus. Severely affected patients may show changes in their complete blood cell count, including toxic changes, left shifts, and neutrophilia.

Management strategies for relieving fecal impaction

Because all constipated cats have some degree of dehydration present, rehydration is the first step in treatment. In mild cases, subcutaneous fluids may be sufficient, but some cats may require hospitalization for intravenous fluids. As the patient is being rehydrated, the fecal impaction can be relieved.

Enemas aid in rehydrating the feces. Carr recommends using warm water with nothing added, but notes that if multiple enemas are repeated in a short period of time, the use of a balanced electrolyte solution such as lactated Ringer’s solution or Normosol may help to prevent major electrolyte shifts in the body. In mild cases, rehydration and enemas alone are usually enough to relieve the constipation.

For severely impacted patients, additional treatment is usually required. Historically, manual disimpaction has been the next step, but Carr rarely resorts to this procedure any longer. He has found the use of percutaneous endoscopic gastrostomy (PEG) solutions administered via nasoesophageal (NE) tube to be highly effective and safe.

After the NE tube is placed and appropriate positioning is confirmed radiographically, the PEG solution is administered over several hours. Most cats defecate within 6 to 12 hours. Typical doses are 100 ml/kg over 10 hours and can be titrated up over time or given for longer time periods if needed. Carr noted that some veterinarians believe the use of PEG solutions is contraindicated but stated that, “in humans, [the use of PEG solutions] has been well documented and, in my personal experience, is very effective.”

Long-term management of constipated cats

Once concurrent conditions have been addressed, patient management starts with dietary therapy and can be augmented from there with laxatives, promotility agents, and probiotics.


Dietary management is the first line of treatment for constipated cats. The best diet for these cats varies by individual and is often based on preference. The most important component of dietary management is the presence of highly digestible fiber. In Carr’s opinion, Royal Canin’s Gastrointestinal Fiber Response cat food has shown good results anecdotally, but it lacks strong evidence-based medicine due to problems with study design.


Several laxatives have been used in cases of feline constipation, including lactulose, bisacodyl, and dioctyl sodium sulfosuccinate. Based on evidence from human medicine, laxatives that contain PEG 3350, such as MiraLAX, are preferred because they are more effective and better tolerated.2 MiraLAX and related products are osmotic laxatives that bind water to keep it in the gastrointestinal tract instead of drawing water into the colon, which can result in dehydration of the body.

These laxatives are well tolerated in cats. In a preliminary study of 6 cats using PEG 3350–containing laxatives, Carr did not observe adverse effects. Doses can vary greatly between patients and often need to be titrated to reach the desired fecal consistency. Carr’s recommended starting dose is a quarter-teaspoon per meal. He notes that it can take up to 3 days to see the full effect, so titrating the dose slowly is recommended.

Promotility agents

For cats that are not responsive to diet and laxatives alone, promotility agents should be added. Cisapride (2.5 to 5 mg per cat every 8 to 12 hours) is the recommended promotility agent and can be compounded to appropriate doses.


Recent evidence has shown that a probiotic available for humans is efficacious for cats with chronic constipation and megacolon.3 Cats treated with this probiotic, which is currently not available in North America, improved clinically and showed improvements on histopathology and endoscopy compared with pretreatment evaluation. Carr stressed that while this particular probiotic was shown to be efficacious, this does not mean that other probiotic strains would show similar results.


In end-stage cases, subtotal colectomy is an option. The surgery is not without risks, but generally has decent outcomes, according to Carr, although avoiding surgery is possible for most patients and medical management is preferred.

Take-home points

The cornerstones of management for all constipated cats, no matter the severity, are relieving the immediate fecal impaction and developing a long-term management strategy to minimize recurrence. Long-term management strategies are multimodal and may need to be adjusted or expanded over time. With appropriate medical management, most constipated cats can live a good life and avoid the need for surgical intervention.


  1. Meeson RL, Geddes AT. Management and long-term outcome of pelvic fractures: a retrospective study of 43 cats. J Feline Med Surg. 2017;19(1):36-41. doi:10.1177/1098612X15606958
  2. Candy DCA, Edwards D, Geraint M. Treatment of faecal impaction with polyethylene glycol plus electrolytes (PGE + E) followed by double-blind comparison of PEG + E versus lactulose as maintenance therapy. J Pediatr Gastroenterol Nutr. 2001;43(1):65-70. doi:10.1097/01.mpg.0000228097.58960.e6
  3. Rossi G, Jergens A, Cerquetella M, et al. Effects of a probiotic (SLAB51™) on clinical and histologic variables and microbiota of cats with chronic constipation/megacolon: A pilot study. Benef Microbes. 2017;9(1):1-10. doi:10.3920/BM2017.0023

Kate Boatright, VMD, is a practicing veterinarian and freelance speaker and author in western Pennsylvania. She is passionate about mentorship, education, and addressing common sources of stress for veterinary teams and recent graduates. Outside of clinical practice, Boatright is actively involved in organized veterinary medicine at the local, state, and national levels.

Related Videos
© 2024 MJH Life Sciences

All rights reserved.