Melena is the presence of digested blood in the feces, and usually occurs as a result of bleeding in the gastrointestinal tract, including the crop, esophagus, proventriculus, ventriculus or small intestine. Occasionally, melena occurs as a result of blood being ingested. For example this might occur if blood from the nose or mouth were swallowed.

Melena should be differentiated from fresh blood in the feces, which is bright red, and usually comes from the colon or the cloaca (common emptying and storage chamber for the intestinal, urinary and reproductive tract). The color of the feces can also change due to alterations in the diet, and may be mistaken for melena. For example, if birds are fed heavily pigmented foods, such as berries, tomato products or colored pellets, the stool may turn the color of the food. If the stool ever appears to be a very dark green-black color, and has a shiny consistency, your veterinarian should be notified immediately, since this is likely to be caused by digested blood.

Anorexia, weight loss, crop stasis, vomiting or regurgitation often accompany melena. Feces may be a normal or loose consistency.

Causes

There are many causes of melena in birds. In most cases, bleeding within the gastrointestinal tract is reason for serious concern. There are many contagious diseases which cause melena, so it is important to inform your veterinarian of any potential contact – direct or indirect – with other birds. Possible causes of melena in birds include:

Foreign bodies. Ingested foreign objects cause irritation and ulceration of the gastrointestinal lining, and are therefore a common cause of melena. Psittacine birds have powerful beaks, and a strong instinct to chew. Common foreign bodies include string toys, bark or wood shavings, and pieces of rubber toys.

Toxins. Heavy metals, plants and cigarettes are commonly ingested. Most plants and cigarettes cause melena by irritating the intestinal tract. Heavy metal toxicity, caused by ingestion of objects containing lead or zinc, is one of the most common diseases seen in pet birds. Not all birds with heavy metal toxicosis have melena, and most have other symptoms, especially neurologic signs.

Bacterial infection. Bacteria may invade the lining of the gastrointestinal tract, resulting in ulceration or hemorrhage. Bacterial infections may come from other birds, from an overgrowth of dangerous bacteria on dirty food or water bowls, or spoiled foods. Often, small amounts of potentially dangerous bacteria live in the intestinal tract without causing harm. This population of bacteria can overgrow and cause disease if the bird's immune system is not functioning properly, as may occur during times of stress. An overgrowth of harmful bacteria may also occur when antibiotics are used improperly.

Viral infection. Several different avian viruses may cause melena. In most cases, melena will be only one of several symptoms.

Neoplasia (cancer). Tumors in the intestinal tract occasionally hemorrhage.

Cloacal papillomas. Papillomas are wart-like structures. They appear most commonly in the cloaca but may occur anywhere along the gastrointestinal tract. Papillomas are one of the most common causes of fresh blood in the feces, but may occasionally also cause melena. There is also a higher incidence of gastrointestinal tract cancer in birds with cloacal papillomas.

Obstruction. Occasionally, an intestinal intussusception (telescoping of one part of the intestinal tract into another) may cause diarrhea and melena initially, then a lack of feces later in the course of disease.

Metabolic disorders. Liver disease or renal disease can cause melena.

Nasal or oropharyngeal hemorrhage. Blood from hemorrhaging tumors, irritation or infection in the nasal cavity, mouth or pharynx may be swallowed, resulting in melena.