Colon and rectal tumors or polyps in cats
A mass can develop in the wall of the large intestine or rectum, the very last part of the digestive tract. In cats, this is rare. It may be a polyp, a non-cancerous growth, or a malignant tumor. Lymphoma is the most common malignant rectal...
What is it?
A mass can develop in the wall of the large intestine or rectum, the very last part of the digestive tract. In cats, this is rare.
It may be a polyp, a non-cancerous growth, or a malignant tumor. Lymphoma is the most common malignant rectal tumor in cats; adenocarcinoma more often affects the small intestine but can reach the colon.
The mass impedes stool passage: the cat strains, bleeds, and sometimes a red mass protrudes from the anus.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Prolonged straining to defecate, with the cat sometimes continuing to strain after passing normal stools.
Bright red blood on the stools.
Red mass protruding from the anus during straining or constantly, especially with a polyp.
Stools thinner than before, constipation, or conversely diarrhea.
Weight loss and vomiting as the tumor progresses.
Duration matters: signs worsening gradually over more than three weeks in an older cat point toward this disease rather than passing colitis.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
As with most tumors, the precise cause is unknown.
Age is the main identified factor.
Certain breeds appear predisposed to intestinal tumors.
Older cat: digestive tumors mainly affect cats over ten years old.
Siamese cats are described as predisposed to intestinal tumors, adenocarcinoma and lymphoma.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian performs a rectal examination, which sometimes allows direct detection of a mass or narrowing.
An abdominal ultrasound examines the colon wall, neighbouring lymph nodes, and other organs.
Colonoscopy allows visualization of the mass and collection of tissue samples.
Only these samples determine whether it is a polyp, lymphoma, or another cancer, which entirely determines the treatment plan.
Blood tests and sometimes chest radiographs complete the evaluation before any treatment.
Treatment
Treatment depends on the nature of the mass.
A polyp is removed surgically or sometimes by endoscopy; analysis confirms it is not cancerous.
An adenocarcinoma is treated by surgery when accessible, sometimes followed by additional treatments.
Lymphoma is most often treated with chemotherapy, which is usually well tolerated by cats.
Pain management and ease of bowel movements are addressed throughout treatment: appropriate diet and medications to facilitate intestinal transit as recommended by the veterinarian.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no known prevention.
In older cats, regular veterinary check-ups and attention to litter box habits make it possible to spot straining or unusual bleeding early.
Possible complications
Colon obstruction, with inability to pass stools.
Recurrent bleeding.
Perforation of the intestinal wall, rare but serious.
Spread of the tumour to lymph nodes or other organs.
Recurrence of a polyp after removal.
When to see a veterinarian
Your cat cannot pass stools and becomes lethargic: consult the same day.
Red material is coming from the anus: consult the same day.
In a male cat, straining in the litter box without passing anything can indicate a urinary obstruction: consult urgently.
Your older cat is straining, bleeding, or having abnormal stools for several weeks.
It is losing weight with no apparent cause.
Prognosis
A polyp that is completely removed has a good prognosis, although recurrence remains possible.
For malignant tumours, the prognosis depends on the tumour type, its extent at the time of diagnosis, and response to treatment; the veterinarian is best positioned to evaluate this after the tissue samples are analysed.
Early diagnosis significantly improves treatment options.
Frequently asked questions
My elderly cat is pushing and bleeding: tumor or simple colitis?
Acute colitis begins suddenly and improves over a few days. A tumor or polyp produces signs that worsen gradually over several weeks, often in an older cat. Only a veterinary examination, and often biopsies, can determine which one it is.
Tumor or chronic constipation?
In chronic constipation, stools are hard, dry and infrequent. A cat that continues to strain after passing normal stools, or that bleeds, suggests an obstruction in the rectum rather.
Is a polyp cancer?
No, a polyp is in principle a benign growth. However, it must be removed and analyzed to confirm this.
Is chemotherapy tolerable for a cat?
In cats, chemotherapy is generally well tolerated: the goal is to give them time with good quality of life, not to make them sick. The veterinarian adjusts the treatment to their condition.
References
Content reviewed by the TunisieVet editorial team · Updated 10 October 2026
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