Melena (Blood in Stool) in Dogs
Overview of Melena (Bloody Stools) in Dogs
Melena, in dogs, 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). 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.
- Infectious agents
- Certain drugs
- Foreign bodies in the stomach or intestines
- Infiltrative and inflammatory gastrointestinal diseases
- Ingestion of blood
- Coagulopathies (bleeding disorders)
- Metabolic and other diseases that cause gastrointestinal ulceration
- Hemorrhagic gastroenteritis (HGE)
- Perioperative hemorrhage (bleeding associated with surgery on the intestinal tract)
- Gastrointestinal ischemia (lack of blood supply)
- Ingestion of heavy metals (uncommon causes)
What to Watch For
- Dark, almost black stools
- Pale gums
- Other areas of bleeding or bruising on the body
- Weight loss
- Poor appetite
- Excessive drinking or urinating
- Excessive urinating
Diagnosis of Melena in Dogs
A thorough history and physical examination are often helpful in determining if melena is present and in suggesting an underlying cause. To determine the exact cause of melena in dogs, additional tests are usually necessary and include the following:
- Complete blood count (CBC)
- Biochemical profile
- Fecal examination
- Abdominal and chest radiographs (X-rays)
- Serology for certain infectious diseases
- Coagulation profile
- Abdominal ultrasonography
- Upper gastrointestinal barium series
Treatment of Melena in Dogs
There are several things your veterinarian might prescribe to treat your dog symptomatically while results of diagnostic tests are pending:
- Individuals with melena may be treated as outpatients if there are minimal systemic signs, especially if there is a known cause that can be removed immediately.
- Dietary recommendations vary depending on the cause; however, a bland diet that is easy to digest may be recommended.
- Avoid all gastrointestinal irritants like corticosteroids, aspirin and other nonsteroidal anti-inflammatory drugs.
- Drugs that block the production of stomach acid and coat the stomach may be recommended.
- In severe cases, hospitalization is warranted for intravenous fluid therapy, blood transfusions, and supportive care.\
- Administer any prescribed medications and follow all dietary recommendations as directed by your veterinarian. Observe your dog’s general activity and appetite, and watch closely for the recurrence of melena, and/or presence of blood in any vomitus. Additionally, report any other signs to your veterinarian.
In-depth Information on Melena in Dogs
Melena usually indicates the presence of significant upper gastrointestinal disease, although occasionally other diseases (such as clotting disorders, ingestion of blood, etc.) unrelated to the gastrointestinal tract may present with melena. The classic appearance of melena is black, shiny, sticky, foul-smelling feces with a tarry consistency. Melena may be seen as the only clinical sign, although other systemic signs often accompany it.
Ingestion of blood must be ruled out, including swallowing blood from the oral cavity or respiratory tract, and licking blood from a wound. A careful history and thorough physical examination of these patients is essential. The presence of melena generally warrants hospitalization, extensive diagnostic testing, and supportive care. It is best to determine the underlying cause and treat the specific problem.
Causes of Melena in Dogs
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 nonsteroidal anti-inflammatory agents (NSAIDs).
- Gastrointestinal ulcerations or erosions commonly produce melena. Such ulcers may occur following acute gastric dilatation and volvulus (twisting of the stomach), heat stroke, overwhelming body infections, the overproduction of stomach acid, shock, anaphylaxis, 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, pancreatitis and hypoadrenocorticism (Addison’s disease) 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.
- Hemorrhagic gastroenteritis (HGE) is a syndrome seen in dogs whose cause is unknown. It usually causes acute diarrhea with fresh blood in it, and vomiting, hematemesis (vomiting blood), and melena can also be seen.
- 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 are uncommon causes of melena in the dog.
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
- An ACTH stimulation test to rule out hypoadrenocorticism (Addison’s disease)
- 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
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), Pepcid® (famotidine), Zantac® (ranitidine), and Prilosec® (omeprazole) 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®) and misoprostol (Cytotec®). 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.
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.