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Melena

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Introduction

  • Cause: gastritis (bacterial/viral/parasitic, eg coccidiosis), gastric ulcers, gastroenteritis, foreign body, pancreatitis, dysbiosis, long term use of ulcerogenic medication, rodenticide poisoning.
  • Signs: lethargy, anorexia, abdominal distension, bruxism, bloating, dark, digested blood originating from the small intestine.
  • Diagnosis: clinical history, fecal examination.
  • Treatment: dependent on the cause, can range from antibiotics, fluid, and nutritional support to euthanasia.
  • Prognosis: guarded.

Presenting signs

  • Lethargy.
  • Anorexia.
  • Weakness.
  • Nausea.
  • Bruxism.
  • Signs consistent with dehydration
  • Black, tarry feces on presentation.
  • Pyrexia.
  • Collapse.
  • Hypersalivation.
  • Abdominal pain.
  • Ileus: abnormal fecal volume, size and consistency
  • Tachycardia.
  • Shock.

Acute presentation

  • Lethargy.
  • Anorexia.
  • Weakness.
  • Nausea.
  • Bruxism.
  • Pale mucous membranes.
  • Dehydration.
  • Hypovolemia.
  • Shock.
  • Black, tarry feces.

Geographic incidence

  • Worldwide.

Breed/Species predisposition

  • Lethal white guinea pigs Dalmation Roan are often born malformed; these animals are more predisposed to gastrointestinal problems.

Public health considerations

  • Until fecal analysis has been performed, care should be taken when handling affected animals.

Cost considerations

  • Initial stabilization with hospitalization and analgesia may be expensive especially when the patient presents out of hours.
  • Investigations into the cause of the melena may be expensive involving blood sampling, diagnostic imaging, endoscopy, PCR and repeat testing.
  • Cost of ongoing medication for management of possible underlying ulceration and repeat visits need to be considered.

Special risks

  • Patients affected by acute hemorrhage may require aggressive stabilization before investigations can be carried out.
  • Anemic animals suffering from chronic blood loss may not be suitable for anesthesia until stabilized.

Pathogenesis

Etiology

Predisposing factors

General

  • Poor husbandry with an inappropriate diet, eg scurvy Vitamin C deficiency.
  • Access to inappropriate toys and objects increasing the likelihood of foreign body ingestion.
  • Animals housed outdoor may be checked less frequently and presented later on in disease process.

Specific

  • Long-term use of non-steroidal anti-inflammatory medication such as meloxicam without the use of gastroprotectants and whilst using higher doses.
  • Chronic azotemia due to kidney disease.
  • Chronic hypovitaminosis C may lead to immunocompromise.

Pathophysiology

  • Long-term use of anti-inflammatory medication and inhibition of cyclo-oxygenase-1 (COX-1) receptors in the gastrointestinal tract reduces prostaglandin secretion. Prostaglandins have a cytoprotective effect on the gastric mucosa. This increases the risk of mucosal injury and development of ulceration.
  • Gastrointestinal ulceration Gastric ulceration of the stomach and duodenum has been shown to happen after intraperitoneal and intramuscular administration of histamine. This leads to an increased acid secretion and subsequent ulceration.
  • Chronic vitamin C deficiency Vitamin C deficiency.
  • Glucocorticoid administration may lead to gastric ulceration.

Timecourse

  • Ulceration may develop acutely following rodenticide toxicity or gastrointestinal surgery.

Epidemiology

  • Young, stressed, and immunocompromised animals will be more predisposed to infectious causes of gastrointestinal ulceration.
  • Geriatric animals will be more predisposed to gastrointestinal ulceration as they will often have coexisting conditions such as kidney and heart disease Heart disease as well as neoplasia Neoplasia overview.
     

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Cho C H & Pfeiffer C J (1981) Gastrointestinal ulceration in the guinea pig in response to dimaprit, histamine, and H1 and H2-blocking agents. Dig Dis Sci 26 (4), 306-311 PubMed.

Other sources of information

  • Hoefer H L, Fox J G & Bell J A (2012) Gastrointestinal Diseases. In: Ferrets, Rabbits and Rodents. 3rd edn. Eds: Quesenberry K E & Carpenter J W. Elsevier, USA. pp 27-45.