Melena: Cat Kidney Disease Glossary

Melena is defined as the passage of black, tarry, and foul-smelling feces. It is a specific sign of upper gastrointestinal bleeding. The black color comes from the hemoglobin in the blood being oxidized by stomach acid and intestinal enzymes as it passes through the digestive tract.

In the Chronic Kidney Disease (CKD) cat, Melena is a grave warning sign that the uremic toxins are causing severe physical damage to the gut.

The "Tarry" Distinction It is vital for owners to distinguish Melena from regular dark stool.

Melena: The texture is sticky, like road tar or blackberry jam. It usually has a very distinct, metallic, and offensive odor.
Constipation: CKD cats often have dark, rock-hard stool. This is not melena.
Iron Supplements: If a cat is taking an iron supplement for anemia, their stool may turn black, but it will remain firm. This is a harmless side effect, whereas true melena is a medical emergency.

The Cause: Uremic Ulceration As discussed with Hematemesis, high levels of uremic toxins and gastric acid erode the lining of the stomach and the upper part of the small intestine (duodenum). When these ulcers bleed, the blood travels down the entire length of the intestine.

The "Hidden" Blood Loss: Because the blood is digested, owners often do not realize the cat is bleeding until the cat becomes severely anemic. A cat can lose a significant amount of blood into their gut before melena becomes obvious in the litter box.

The Connection to Anemia Melena often appears in cats who are suffering from "crashing" anemia (low red blood cell count). If a cat is receiving Erythropoietin (EPO) injections but their anemia is not improving, or is getting worse, veterinarians will immediately check for melena to see if the cat is losing blood faster than the body can replace it.

Disclaimer: This content is for educational purposes only and does not constitute veterinary medical advice. Always consult with your primary care veterinarian or a veterinary internal medicine specialist regarding your cat’s specific condition.

In the Chronic Kidney Disease (CKD) cat, Melena is a grave warning sign that the uremic toxins are causing severe physical damage to the gut.

The "Tarry" Distinction It is vital for owners to distinguish Melena from regular dark stool.

Melena: The texture is sticky, like road tar or blackberry jam. It usually has a very distinct, metallic, and offensive odor.
Constipation: CKD cats often have dark, rock-hard stool. This is not melena.
Iron Supplements: If a cat is taking an iron supplement for anemia, their stool may turn black, but it will remain firm. This is a harmless side effect, whereas true melena is a medical emergency.

The "Hidden" Blood Loss: Because the blood is digested, owners often do not realize the cat is bleeding until the cat becomes severely anemic. A cat can lose a significant amount of blood into their gut before melena becomes obvious in the litter box.