Clinical Reasoning in Veterinary Practice

With secondary GI disease:

Animals will often have evidence from the history and/or clinical examination of abnormalities affecting other organ systems, for example, jaundice, polyuria/polydipsia (PU/PD).

Vomiting is usually intermittent, unrelated to eating and may often occur subsequent to the onset of other signs of malaise.

In general, animals that are vomiting due to extra‐GI disease are metabolically ill and are not usually bright, alert and happy.

If a patient has been metabolically ill (depressed and inappetant) for a significant period before vomiting was observed, then secondary GI disease is more likely.

Secondary GI causes of regurgitation will frequently have other systemic signs such as generalised weakness or metabolic malaise. It is usually only patients with megaoesophagus due to focal myasthenia gravis who present with regurgitation as their only clinical sign.

The exception to these generalisations about the features of secondary GI disease is pancreatitis in dogs. Canine pancreatitis behaves similarly to a primary GI disease in that it causes acute‐onset vomiting in an initially often otherwise well dog and often subsequent to an episode of dietary indiscretion. The vomiting often occurs immediately after eating, and decreased appetite and depression may not precede the onset of vomiting.

Pancreatitis in cats, however, usually behaves similarly to a secondary GI disease. Cats with hyperthyroidism may also vomit intermittently over a prolonged period and seem otherwise well (although, of course, they may also have other clinical signs suggestive of hyperthyroidism).

If primary GI disease is determined to be present, the temporal relationship of vomiting to eating and the character of the vomitus should be used to assess where the lesion is likely to be – the upper or lower GI tract.

Diagnostic tools such as contrast radiography may be appropriate to localise the lesion. An assessment of the likely location of the lesion is important, as this may determine what further diagnostic procedures are suitable. For example, endoscopy would be appropriate for examining the stomach and possibly duodenum but will be of little use if lower small bowel disease is suspected.

Defining the location for secondary GI disease usually involves routine clinical pathology and dynamic or function tests +/− imaging to localise the organ affected, for example, liver, kidney, pancreas and adrenals.

The location of the problem for patients who are regurgitating is almost always the oesophagus (occasionally the pharynx), whether the cause is primary or secondary GI. Thus, regurgitation is a clinical sign where location is considered first, and then the question is asked, Is this a primary or secondary GI lesion?

Once the lesion has been located within the GI tract, it must now be identified. Biopsy may be appropriate or the type of lesion may be evident by visual inspection (e.g. foreign body).

In the GI tract, as elsewhere, neoplasia and inflammation often look grossly identical, and biopsies should always be taken even if the GI tract looks grossly normal.

GastritisDietary indiscretionDrug induced, for example, non‐steroidal anti‐inflammatory drugs (NSAIDs)Immune‐mediated inflammatory diseaseInfection, for example, Helicobacter pyloriRarely clinically significant

Gastric foreign bodies

Gastric ulceration (see section below discussing haematemesis)

Gastric neoplasia

Disorders of the pylorusPylorospasmPyloric obstructionCongenital pyloric stenosisChronic hypertrophic gastropathy

Abnormal gastric motility

Those intestinal diseases for which vomiting is a predominate clinical feature include the following:

Infectious enteritis, for example, parvovirus, corona virus (diarrhoea will usually also be present)

Dietary indiscretion (diarrhoea often present)

Intestinal obstruction – foreign body and intussusception

Inflammatory bowel disease especially in cats (dogs tend to more commonly present with diarrhoea as the major clinical sign).

The closer the obstruction is to the pylorus, the more frequent and severe the vomiting.

A large number of secondary GI disorders can cause vomiting. However, most of these can be eliminated with relatively few tests – at least in dogs. Cats are more problematic, especially in the diagnosis of pancreatic and hepatic disease. In Table 3.1, the most important secondary GI disorders are listed with tests that are useful in their diagnosis.

Table 3.1 Secondary gastrointestinal causes of vomiting in cats and dogs.

You should consult other textbooks to read about specific details of primary and secondary GI diseases causing vomiting and regurgitation.

Persistent vomiting of fresh blood or vomiting of digested blood (coffee grounds) can be of significant clinical concern. The cause may be primary GI disease or secondary GI disease. Contrary to popular belief, most patients that are vomiting do not have gastric ulceration and do not need to be treated with an anti‐ulcer drug. However, there may be a role for use of drugs that suppress gastric acid secretion (preferably proton‐pump inhibitors) to prevent secondary oesophagitis.

Haematemesis may be the only sign of gastric bleeding, but concurrent melaena is common (see Chapter 12).

Primary GI causes of haematemesis include:

NeoplasiaLymphoma, adenocarcinoma, leiomyoma and leiomyosarcoma

Gastric foreign body

Severe inflammatory disease.

Secondary GI causes of haematemesis include:

Coagulopathy

Secondary GI diseases causing gastric ulcerationNSAIDsHepatic diseaseHypoadrenocorticismGastrinomaMast cell tumour (non‐GI location)TraumaRenal failureSystemic inflammationFor example, pancreatitis, sepsisExtreme exerciseFor example, sled dog racing.