Haemorrhagic gastroenteritis

A hyperacute syndrome of unknown aetiology, characterized by sudden onset vomiting and bloody diarrhoea leading to rapid dehydration, haemoconcentration and hypovolemia due to large loss of water and electrolytes that pass into the intestinal lumen.

The triggering cause is thought to be an increase in intestinal vascular permeability associated with mucus hypersecretion, which causes red blood cells, plasma and fluids to enter the intestinal lumen. Increased permeability is caused by an abnormal local immune overreaction to bacteria or bacterial toxins (similar to endotoxic shock) or to a dietary component. It could even involve a type I hypersensitivity reaction (IgE- and mast cell-mediated allergic reaction). According to some authors, hyperactivity and stress can also contribute to the onset of the pathology.

Several studies have associated this pathology with the presence of bacteria of the genus Clostridium, which has led to speculation that this microorganism or its toxins could be the triggering cause. However, most experts believe that Clostridium is merely a complicating factor, since the inflammation and necrosis of the intestinal mucosa caused by this bacteria does not usually appear in cases of acute haemorrhagic enteropathy.

The disease can affect dogs of any age and breed, but it is more common in young adults (2 - 4 years) of small breeds (for example Poodle, Schnauzer, Yorkshire Terrier, Pekingese, Maltese Bichon).

Clinical signs

The symptoms are usually peracute, appear in animals that are in good health, and are not associated with changes in habits (dietary, intoxication, etc.). The clinical picture is initially (although not always) characterized by vomiting (bloody or not), sudden onset bloody, generally foul-smelling jelly-like diarrhoea, anorexia, depression, abdominal pain, and rarely fever.

The animal may exhibit signs of shock, with a rapid, weak pulse and prolonged capillary refill time. It is important to note that there is no clinical evidence of dehydration (the skin fold test is usually normal) due to the peracute course of the disease.

Interpretation of laboratory tests

Diagnosis is differential, i.e., ruling out other pathologies that present with similar symptoms:

• Viral gastroenteritis, typical in puppies: parvovirus o coronavirus infection.
• Bacterial enteritis: caused by Salmonella, Clostridium, or Campylobacter.
• Leptospirosis
• Acute pancreatitis
• Parasitosis, such as giardiasis, coccidiosis, trichuriasis, etc.
• Acute intestinal obstruction.
• Primary gastrointestinal disease, such as ulcerative colitis.
• Gastrointestinal ulcers due to uncontrolled administration of NSAIDs for human use.
• Hypoadrenocorticism (Addison's disease).
• Clotting disorders (rodenticide poisoning, thrombocytopaenia).
• Lead, arsenic, or thallium poisoning

Diagnosis will rely heavily on thorough history-taking and knowledge of the pathology associated with these toxins (neurological, renal, dermal signs, etc.).

The most notable features of haemorrhagic gastroenteritis are its peracute presentation in an otherwise healthy animal and haemoconcentration without apparent dehydration.

General Tests

• Complete blood count: Most patients show marked haemoconcentration (HCT: 60%-75%) due to acute, major fluid loss. A stress leukogram is usually observed, with leucocytosis, neutrophilia and lymphopaenia.
• Blood biochemistry: Hepatic transaminases may be elevated due to destruction of hepatocytes secondary to absorption of toxins and hepatic hypoxia. Urea may be moderately elevated (prerenal uraemia), usually associated with oliguria. Pancreatic enzymes are normal or only slightly elevated, which helps rule out pancreatitis. Total proteins are usually normal or decreased due to gastrointestinal losses. Ionic imbalance with hypokalaemia may occur.
• Stool parasites: Usually absent, although in some cases they can appear as an associated factor.

Specific tests (differential diagnosis)

• Clotting tests: Normal, except in advanced cases in which disseminated intravascular coagulation, usually sepsis-related, may occur. CT, aPTT, PT, and FDPs are elevated while the platelet count is decreased (consumptive thrombocytopaenia).
  Stool culture: For enteropathogens such as Salmonella, Campylobacter and Clostridium.
  Parvovirus and coronavirus antigen tests.
  TLI (tripsine-like inmunorreactivity): Values greater than 80 ng/ml are diagnostic of acute pancreatitis.

Bibliography

• GUILFORD, W.G.; CENTER, S.A.; STROMBECK,D.R. et al. (1996): Strombeck´s Small Animal Gastroenterology. (3ª ed.) Saunders, pg. 433-435
• BUSH, B.M. (1999): Interpretation of Laboratory Results for Small Animal Clinicians ( 6ª ed.) Blackwell Science Ltd., pg. 35-42
• MORGAN, R.V. (1997): Handbook of Small Animal Practice ( 3ª ed.) Churchill Livingstone., pg. 360
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• NELSON, R.W., COUTO, C.G. (2020) Medicina interna de pequeños animales (6ª ed.) EDRA pg 1231-1234.