grovercentervetThe Complete Guide to Constipation & Megacolon in Dogs & Cats
You’re a dedicated pet owner and keep a close eye on your pet’s habits. You hear them eating it, watch them as they get active, and, of course, hear their litter box and observe their walks and outdoor habits. One or two bowel movements may be lost at any given time but when the condition becomes a recurring problem it can easily escalate into a medical crisis.
If a pet has multiple episodes of infrequent bowel movements, or experiences difficulty during bowel movements, or is unable to defecate, it indicates that there is an underlying problem with the large intestine. In dogs and cats, simple straining can progress to dangerous situations of constipation and megacolon.
In this complete reference guide, you will learn about the relationship between these diseases, learn the warning signs and discover the most recent veterinary diagnostic and treatment options for these conditions.
Understanding the spectrum from constipation to "megacolon"
You need to understand that digestive problems can be progressive to help protect your pet’s digestive health. The longer the faeces remains stagnant in the large intestine, the more serious the condition is.
1. Simple Constipation
Constipation is defined as having very few bowel movements, having trouble passing stool or not passing stool at all. The main function of the colon is to absorb the water that’s in the digested waste. If stool is not eliminated from the colon, it stays there for an extended period of time and the colon continues to extract moisture from the stool. This causes the waste to become tough, dry and rock hard, which makes it very painful and hard to pass.
2. Obstipation
If simple constipation is ignored or is not resolved by the initial treatment, it becomes obstipation. The faecal mass becomes so compacted, dry and impacted that it cannot be passed by itself. The intestine is completely obstructed and there is a severe functional blockage.
3. Megacolon
Megacolon is the last and most serious step in this process of gastrointestinal disease. Dogs and cats with constipation and megacolon are closely related as the constipation causes the large intestine smooth muscles to become over-stretched.
This extreme stretching over time damages the nerves and muscle fibres locally and eventually leads to the colon becoming permanently stretched, floppy and paralyzed. The colon changes into a large, droopy bag that can’t squeeze or propel stool through it. This condition is sometimes seen in older dogs, but is much more often seen in middle aged to older cats.
Common Causes of Constipation and Megacolon in Dogs and Cats
Constipation and megacolon in dogs and cats can be triggered by a variety of underlying lifestyle, mechanical and metabolic factors that upset the digestive tract. The most common are:
- Idiopathic: In cats, the overwhelming majority of cases are considered “idiopathic” and the actual cause of the condition remains unknown. In this, it is a major disease of smooth muscle of the colon, and the organ simply fails to move normally.
- Mechanical Obstructions: Anything which physically constricts the pelvic canal or prevents stool from leaving can cause back-up and stretching. Examples include poorly healed pelvic fractures from previous injuries, a very large prostate gland in male dogs, colorectal tumours or strictures.
- Dehydration and Diet: Dry stools are very common in animals that don’t drink enough water or that are eating poor-quality diets that are not balanced for the appropriate fiber. The colon becomes hyperactive at reabsorbing water, leading to long-term constipation, because it is constantly starved of water.
- Large Intestine Disorders: Damage to the spinal cord, pelvic nerve injuries or diseases such as Intervertebral Disc Disease (IVDD) can impair the communication of important nerves between the brain and the smooth muscles of the large intestine.
- Metabolic and Electrolyte Imbalances: Conditions such as chronic kidney disease, hypokalemia (low potassium) and hypercalcemia (high calcium) reduce the overall muscle strength and slow down intestinal motility.
- Ingestion of Foreign Bodies or Hair: Foreign bodies, excess hair (long haired cats) or ingestion of dirt, bones and toys can cause dense unpassable fecal mixtures.
Signs and Symptoms to Watch For
Signs and symptoms to watch for are similar to those of meningitis. A dog or cat can develop a condition known as megacolon, which is a progressive constipation caused by structural changes. The early signs of constipation and megacolon can be identified in dogs and cats and prompt veterinary treatment can prevent irreversible damage to the large bowel.
Animals affected with these diseases show any or all of the following clinical symptoms:
Frequent Straining leads to Small, Hard Stools which leads to Lethargy & Vomiting.
- Tenesmus (Prolonged Straining): You will notice your pet straining (aggressively) outside the litter box for extended periods of time (not getting anything out) or hunched over inside the litter box for long periods of time.
- Production of Fecaliths: Any waste will be a small, bone-dry, rock hard pellet.
- Diarrhea of the opposite type: sometimes, owners will think they have diarrhea when they actually have constipation. As stool that is liquid comes down from the upper part of the digestive system can push around the compacted stool, which can leak out and give the impression of loose stools.
- Systemic Illness: When the impaction progresses and the toxins are absorbed into the bloodstream, the pets lose their appetite, become lethargic, lose weight and frequently vomit.
- Abdominal Pain: Avoid touching or lifting your dog or cat’s belly, as they might react by vocalizing, growling or moving away.
How Veterinarians Diagnose the Condition
If you think your pet may have Megacolon in dogs and cats, the veterinarians are the only people who can make an accurate diagnosis. The veterinarian will do a thorough physical exam and gently palpate the abdomen to look for a distended, stool-filled colon.
Veterinarians use objective diagnostic imaging to rule out simple constipation and differentiate from irreversible megacolon:
Abdominal Radiographs (X-rays)
This is the Gold Standard to evaluate this condition. The severity is calculated using a very precise mathematical formula that compares the colon diameter to the length of the 5th Lumbar Vertebra (L5):
Colon Diameter>1.5×Length of the 5th Lumbar Vertebra (L5)
If the diameter of the colon is greater than 1.5 times the length of the L5 vertebra, it strongly suggests that the patient has moved from normal constipation to true megacolon. The vet will also use X-rays to inspect for old pelvic fractures, arthritis or swallowed foreign bodies.
Additional Laboratory Diagnostics
Further laboratory tests may be ordered to exclude possible metabolic causes, such as bloodwork and urinalysis. These tests assess kidney function and test for serious electrolyte imbalance such as low potassium or high calcium, which can reduce the normal movement of food in the intestines.
Treatment and Management Protocols
The treatment and management of constipation and megacolon in dogs and cats is a gradual process. Treatment depends on the severity of the impaction and if the colon has any natural muscle function left.
1. Medical and Lifestyle Measures
In early or reversible constipation, medical and lifestyle measures can restore normal bowel patterns:
Treatment Type
How It Works / Protocol
Aggressive Rehydration
Fluid therapy is the first step in treatment. The pet must be hydrated with subcutaneous or intravenous fluids, which will rehydrate his body, and therefore the dry intestinal tract.
Modern Laxative Therapy
Osmotic laxatives such as Polyethylene Glycol (PEG 3350) or lactulose are very effective. These compounds don’t get absorbed into the pet but rather stay in the bowel and bring the water directly into the stool, softening the stool without any danger.
Prokinetic Medications
If the colon smooth muscle is still working, medications are used to activate the smooth muscle in the colon to move it.
Strategic Dietary Adjustments
Dietary requirements differ with patient. Others require very digestible, low-residue prescription diets which reduce the volume of faeces. Others thrive with high fibre diets using soluble fibre (such as psyllium husk) which helps to gel and retain water in the stool.
2. Clinical Deobstipation
If a pet is very affected or has extreme obstipation, the oral medications are not sufficient. Veterinarians must use only a hard mass removal to extract the hard mass.
Important Warning: Do not try to remove a hard mass at home using an over-the-counter human enema (e.g., a Fleet phosphate enema). They are highly poisonous to pets, and can cause a fatal electrolyte imbalance.
Clinical deobstipation will be carried out under general anaesthetic to prevent the pet from becoming too painful in doing it and to prevent accidental tearing of the intestinal wall. A specially formulated warm water enema is gently administered to the pet to break up and dislodge impacted stool; gentle manual manipulation is used by the veterinarian.
If that’s not an option, a temporary NG tube can be inserted and used to administer an infusion of PEG 3350 solution over 12-24 hours, which will safely break down the blockage.
3. Surgical Intervention: Subtotal Colectomy
If medical management is not effective, and the patient has chronic, irreversible megacolon, surgery is the most humane and effective treatment.
The procedure of choice is a subtotal colectomy. This is a significant abdominal operation, in which the stretched out part of the large bowel is cut away and then the surgeon sutures the healthy ends back together.
Although pets often get temporary diarrhea for several weeks after undergoing subtotal colectomy as they get used to their new body, most dogs and cats adjust very nicely. They then lead pain-free, normal lives and enjoy a good long life.
Conclusion
Managing a dog or cat’s constipation and megacolon requires attentiveness, prompt treatment by a veterinarian, and individualized treatment. If you’re having irregular bowel movements, it’s best to solve this problem early by making a few lifestyle changes and drinking more water before it gets worse. If your pet’s condition progresses into complete nonfunctional megacolon, however, do not worry—there are advanced medical treatments and surgical procedures such as a subtotal colectomy that will ultimately help your pet. With close collaboration with your veterinarian, these uncomfortable obstructions can be addressed and you can get your furry friend’s digestive system and comfort back to normal.
Frequently Asked Questions
What is the difference between constipation and megacolon in dogs and cats?
Constipation is a brief or intermittent problem of defecation, in which the colon remains structurally normal and is still capable of contracting. Megacolon is a late stage, pathological process involving a long-standing impaction which causes the smooth muscle of the colon to be so stretched that it is permanently weakened, flaccid and structurally dilated, and no longer able to expel stool.
Does a high fibre diet aggravate megacolon?
Yes, it can. Adding bulk-forming insoluble fiber to an animal with a non-functioning megacolon, due to paralysis, can be potentially harmful – fiber is used to prevent simple constipation. When the colon isn’t contracting, the extra mass is not able to be moved forward and this can rapidly exacerbate the fecal impaction. The advanced patients generally respond well on prescription low residue, high digestible diets.
Does pumpkin benefit an upset dog or cat with constipation?
Canned pumpkin (unsweetened form) is a great source of soluble fibre and water which is very beneficial in treating mild and occasional constipation. If your pet’s obstipation is deep or if it is true megacolon, however, pumpkin is not enough to provide sufficient therapeutic relief to break up a hardened fecalith, and it is necessary that you pet’s medical condition be attended to immediately.
Does megacolon hurt animals?
Yes, megacolon is extremely uncomfortable and painful. The constant pressure and stretching of the soft tissues of the intestine, combined with the intense abdominal pressure, cramping and systemic nausea and vomiting caused by the reabsorption of toxins into the pet’s bloodstream, is not a pleasant condition.
Is it normal to live with a subtotal (partial) colectomy in a pet?
Absolutely. Although the surgery is a major one (subtotal colectomy), the prognosis is good. Most pets do fine within a few weeks after the other digestive tract is able to compensate for the loss of the colon. Their bowel movements may always be softer than usual, but their pain is completely removed, and they do not need any drastic laxative treatments or manual deobstipations.
