Melena (Blood in Stool) in Cats
Melena is the presence of digested blood in the feces and makes the stools appear black and tarry. Melena is different from fresh blood in the stool (hematochezia). In cats, melena may represent a severe, life-threatening illness, and should not be ignored. It must especially be addressed if it persists or worsens.
Melena develops when bleeding occurs into the stomach or small intestines. The bleeding must be high in the intestinal tract in order for the blood to be digested and become discolored. Bleeding into the colon or rectum (hematochezia) appears as fresh blood in the stool.
Causes of Melena in Cats
There are many potential causes for melena. The most common causes are usually diseases of the gastrointestinal tract that create ulcerations or cause bleeding into the tract. Ingestion of blood or bleeding from clotting abnormalities can also cause melena. It is important to determine a cause, as specific treatment is necessary to successfully treat patients with melena.
- Infectious disorders such as intestinal parasites, viral, bacterial, and/or fungal infections should be ruled out.
- Intestinal irritation and ulceration may occur with the administration of certain drugs, particularly corticosteroids and aspirin.
- Gastrointestinal ulcerations or erosions commonly produce melena. Such ulcers may occur following heat stroke, overwhelming body infections, the overproduction of stomach acid, shock, and as a side effect of some cancers.
- Gastrointestinal tumors or foreign bodies can cause bleeding and melena.
- Certain metabolic diseases, such as kidney and liver failure can cause bleeding into the intestinal tract.
- Inflammation of the walls of the intestines (inflammatory bowel disease) can be associated with melena.
- Ingested blood should be considered as a cause when bleeding is present in the oral cavity or respiratory tract, or when the animal has been witnessed licking a bleeding wound.
- Coagulopathies (abnormalities in blood clotting) should also be considered, especially if there is evidence of bleeding from other body sites.
- Any time surgery is performed on the upper gastrointestinal tract, bleeding may occur into the tract. Melena can then appear 12-72 hours after surgery. This form of melena should be very transient.
- Gastrointestinal ischemia (lack of blood supply) secondary to shock, volvulus (torsion), intussusception (telescoping of the bowel into itself), or infarction (blockage of circulation to an area) can cause death of the lining of the intestines and bleeding into the intestines with subsequent melena.
- Heavy metal toxicity including arsenic, lead, and zinc can cause melena, but are rare in the cat.
Diagnosing Melena in Cats
Obtaining a complete medical history, and performing a thorough physical examination are necessary in order to create an appropriate diagnostic plan for the patient with melena. An extensive battery of tests is often required to identify or isolate the specific cause, and such tests may include:
- A complete blood count (CBC) to evaluate for the presence of infection, inflammation and anemia associated with some diseases that cause melena
- A biochemical profile to rule out metabolic causes of melena, and to evaluate electrolyte and protein levels
- A urinalysis to evaluate the kidneys, the hydration status of the patient, and the presence of blood in the urine
- Fecal tests for parasites and fecal culture for bacteria
- A coagulation profile and platelet count to assess blood clotting
- Abdominal radiographs (X-rays) to evaluate the abdominal organs and possibly identify foreign material or a tumor
- Chest radiographs to evaluate for the presence of fluid (blood) or metastasis (spread of tumor) in the lungs
Your veterinarian may recommend additional tests to ensure optimal medical care. These are selected on a case-by-case basis:
- Serologic tests for certain infectious diseases that may cause melena
- Bile acids tests if liver disease was identified on the biochemistry test
- A blood lead assay if there has been exposure to lead, or if there is material that looks like lead visible on abdominal x-rays
Abdominal ultrasonography to evaluate the size, shape and texture of abdominal organs and help assess the presence of tumors and foreign bodies
- An upper gastrointestinal (GI) barium (dye) series of x-rays, especially when the above tests fail to reveal the cause of melena
- Upper GI endoscopy, which involves the insertion of a flexible viewing scope into the stomach and upper small intestines
- Exploratory surgery of the abdomen for undiagnosed disease or cases requiring corrective surgery
Treating Melena in Cats
As the above diagnostic tests are underway, your veterinarian may start symptomatic therapy, especially if the problem is severe. The following nonspecific (symptomatic) treatments may be applicable to some pets with melena. These treatments may reduce the severity of symptoms and provide some relief to your pet. However, nonspecific therapy is not a substitute for definitive treatment of the underlying disease responsible for your pet’s condition.
- Temporarily discontinue all oral liquids and food, especially if the animal is also vomiting. This allows the GI tract to rest and may facilitate healing of the lining of the GI tract. Gradual reintroduction of small amounts of bland food may then be instituted if the clinical signs have subsided.
- Subcutaneous or intravenous fluid and electrolyte therapy may be necessary in some patients with melena to correct dehydration, acid-base, and electrolyte abnormalities.
- Blood transfusions may be indicated in the patient that becomes anemic from the melena.
- Plasma transfusions and vitamin K therapy may be indicated in patients with coagulopathies.
- Drugs that decrease acid production by the stomach such as Tagamet® (cimetidine), and Zantac® (ranitidine) may expedite the resolution of melena, especially if it is secondary to gastrointestinal ulcers.
- Gastrointestinal protectants and adsorbents (bind harmful substances) may be considered. Protectants that may be tried include sucralfate (Carafate®. Protectants containing bismuth should be avoided because they often turn the stools black and can make it difficult to determine whether the melena has resolved.
- In some cases surgical intervention is recommended, especially when a bleeding ulcer, gastrointestinal tumor, foreign body, or malpositioning of the stomach/intestines is diagnosed.
Home Care for Cats with Melena
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve.
- Administer all prescribed medications exactly as directed. Alert your veterinarian if you are experiencing problems treating your pet.
- Discontinue or avoid any medication or substance that may be irritating to the stomach lining.
- Return to your veterinarian for follow-up testing as directed. Monitoring for anemia, electrolyte problems, and blood clotting ability may be indicated depending on the underlying cause of melena in your pet.