Dark Blood In Cat Stool (Melena)

What is melena?

Blood in the stool can refer to melena or hematochezia. The type of and appearance of blood can give a clue as to the possible cause.

• Melena refers to blood in the stool which is black and tarry, this type of blood in the stool originates in the upper gastrointestinal tract.
• Hematochezia is the presence of bright red blood on or throughout the feces which originates in the lower gastrointestinal tract.

This article looks at what causes melena in cats. For information on hematochezia, read here.

The dark colour of melena is due to digested blood in the feces. This bleeding may originate from the pharynx, lungs (where the blood is coughed up and then swallowed), esophagus, stomach or upper small intestine. The colour and tarry texture is due to the breakdown of hemoglobin in the blood by bacteria in the stomach.

A large amount of blood is required to cause melena, therefore it should be treated as an emergency as there are several potentially serious causes of this condition. Seek immediate veterinary attention.

Causes

Melena isn’t a disease in itself, it is a symptom of an underlying disorder.

• Gastrointestinal ulcers: Erosion of the lining of the stomach due to stomach acid, poisons, chemical burns or certain medications such as NSAIDs and corticosteroids.
• Mucosal trauma: Foreign body or injury during an endoscopy procedure.
• Ingestion of blood: Nosebleed, bleeding in the lungs, dental bleeding.
• Blood clotting disorders: Disseminated intravascular coagulation, which is caused by multiple factors such as parasites, infection, inflammatory conditions, liver disease, snake bite, shock, pancreatitis and inflammatory conditions or thrombocytopenia (low blood platelets).
• Systemic diseases: Liver disease, pancreatitis, chronic kidney disease.
• Inflammatory diseases: Inflammatory bowel disease, colitis.
• Cancer: Several cancers can develop along the gastrointestinal tract causing bleeding.
• Infection – Hookworm, histoplasmosis, salmonella, campylobacter, parvovirus, coronavirus.

Symptoms

The most obvious symptom is black, tarry and greasy feces. Other symptoms will depend on the underlying cause, common signs to look out for include:

• Vomiting (which may or may not contain blood)
• Abdominal pain
• Loss of appetite (anorexia)
• Difficulty breathing
• Weight loss

In addition to vomiting, symptoms will vary depending on the underlying cause.

Anemia:

• Lethargy
• Weakness
• Pale gums
• Difficulty breathing

Blood clotting disorders:

• Nosebleeds
• Bruising under the skin
• Blood in urine
• Kidney failure
• Liver failure
• Heart failure

Aspirin toxicity:

• Rapid breathing
• Increased urination
• Nervous system disturbances (excitability, loss of balance, seizures)
• Jaundice
• Fever

Diagnosis

Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. This will include questions about other symptoms you may have noticed, any medications, supplements or poisons your cat may have ingested.

It will be necessary to run baseline tests which include biochemical profile, complete blood count, and urinalysis to determine the overall health of your cat and look for any abnormalities in the blood, serum and urine which may narrow down the possible cause.

• Complete blood count: May reveal anemia (low red blood cell count), thrombocytopenia (low platelets), increased white blood cells.
• Biochemical profile: This may reveal elevated liver enzymes, hyperbilirubinemia (high bilirubin levels in the serum), elevated BUN and creatinine levels.
• Urinalysis: To look for blood in the urine.

Additional tests depending on your veterinarian’s index of suspicion may include:

• Specialist blood and serum tests: Blood clotting tests, coagulation profile, blood gas test.
• Blood smear examination: To look for abnormalities in the red blood cells.
• Fecal examination: This may reveal the presence of parasite eggs.
• Upper gastrointestinal barium series: To evaluate the upper gastrointestinal tract. Barium is a white powder which is not transparent to x-rays. The cat eats a barium meal that coats the GI structures, an x-ray will highlight tumours, ulcers, and damage.
• Endoscopy: A flexible tube with a camera at the end is inserted into the esophagus and into the stomach to look for tumours, blockages, ulcers, a biopsy may be taken during the procedure.
• Xrays and/or ultrasound: To look for tumours, blockages, foreign bodies and evaluate the kidneys and liver.

Treatment

The goal of treatment is to address the underlying condition as well as provide supportive care.

Supportive care:

• Intravenous fluids to treat dehydration and help the body flush out toxins
• Anti-nausea medications to control vomiting
• Blood transfusion may be required for severely anemic cats
• Bland diet such as boiled chicken and rice which is easy for your cat to digest.

Specific treatments:

• Ingestion of toxins: Induce vomiting if exposure has occurred within the past 2 hours, pump the stomach to remove the toxins from the system followed by activated charcoal.
• Ingestion of blood: Find and treat the source of bleeding such as dental extraction or surgery to repair damaged tissues.
• Gastrointestinal ulcers: Medications to protect the stomach lining such as ranitidine, cimetidine or famotidine and antacids.
• Cancer: Surgery to remove a tumour followed by chemotherapy where indicated.
• Foreign body: Surgery or endoscopy to remove the object.
• Chronic kidney disease: Low protein and phosphorous diet, phosphorous binders, appetite stimulants, anti-nausea medications and fluids to treat dehydration.
• Liver disease: Surgery (where possible), nutritional support and supportive care.
• Pancreatitis: Find and address the underlying cause, and aggressive supportive care such as analgesics, anti-nausea medication, and nutritional support.
• Infection: Anti-parasitic medications to treat worms, antibiotics for bacterial infections, itraconazole or ketoconazole to treat histoplasmosis and supportive care for viral infections.
• Blood clotting disorders: Treatment depends on the underlying cause, which must be identified. A blood transfusion may also be necessary.