Vomiting can be defined as the ejection of part or all the contents of the stomach and/or upper intestine through the mouth, usually in a series of involuntary spasmodic movements. The disturbances in gastrointestinal (GI) motility are coordinated with respiratory and abdominal muscle contractions and mediated by the central nervous system (CNS).

Vomiting begins with retching, a series of brief negative intrathoracic pressure pulses that coincide with positive abdominal contractions. These pressure changes occur because of repeated herniations of the abdominal esophagus and cardiac portion of the stomach into the esophagus. During retching, food freely moves back and forth in the esophagus, which is now dilated because of the ingesta. Ultimately, the diaphragm rapidly moves cranially, resulting in positive intrathoracic pressure that leads to expulsion of these contents.1 Vomiting is such an active process that it seems to involve the whole cat, and so it is little wonder that it concerns owners so much.

Since vomiting is mediated by the CNS with input and influence from just about anywhere in the body, it is important to summarize this physiology so it can be appreciated when managing clinical cases. Vomiting results from stimulation of the “vomiting center,” which is in the brainstem; there are four main pathways that stimulate the vomiting center,¹ and these are summarized below and in Fig. 26.1.

These complex pathways highlight the need to consider the whole cat and not just the cat’s GI tract when assessing a cat presenting for vomiting. The approach to managing a cat with vomiting must follow logical steps. When the underlying cause is GI disease, a precise diagnosis can only be reached after obtaining biopsy samples. A summary of diagnostic steps and possible underlying causes is shown in Fig. 26.2.

The diagnostic steps are:

The important aspects of the clinical history are given in Table 26.1. Signalment is important, because younger cats are more likely to have ingested foreign bodies (though not all older cats have grown out of this habit). Some extra-GI problems, such as hyperthyroidism and renal disease, are more likely to occur in older cats.

Most texts and references instruct clinicians to distinguish between vomiting and regurgitation, with the latter noted as being quite passive.1–3 In practice, it can be hard to make this distinction, because it is the author’s experience that cats with esophageal disease can have quite forceful, spasmodic movements when ejecting ingesta by regurgitation—although it is also possible for regurgitation to be a passive process. Given that the physiology of vomiting, as described earlier, results in ingesta being forced into and then evacuated from the esophagus, it is hardly surprising that it can resemble regurgitation. Fortunately, regurgitation and esophageal disease do vary from vomiting in other ways! Vomiting is usually preceded by the cat licking its lips, salivating, or making attempts to swallow. Regurgitated ingesta is often in a tube-like structure and if undigested can be covered with frothy saliva. Partially digested food suggests vomitus, and the presence of bile or digested blood confirms this.

It is important to determine if the cat vomits regularly. Many owners have seen their cat vomit on a regular basis with no evidence of the cat being unwell, and this is noted frequently in the veterinary literature.^1,2 Hairballs can cause gastric irritation, and it may be that eating quickly also stimulates the peripheral sensory receptors that contribute to vomiting. If a cat does vomit regularly, it is important to assess if the cat is presenting for a change in the vomiting pattern (e.g., frequency or timing in relation to eating) and if the cat is unwell in any way, such as anorexia or weight loss.

The pattern of vomiting is important in all cases, because cats presenting with acute gastritis usually have a sudden onset of frequent vomiting compared to those with chronic disease processes that may vomit every few days. The timing in relation to eating can be helpful because the stomach should empty by 6 to 8 hours after a meal; vomiting longer than 8 hours after a meal can suggest motility or retention disorders. The description of the vomitus can be helpful. If bile is present, the pylorus is not obstructed; the presence of blood (digested or fresh) indicates ulceration. Hair in the vomitus can indicate hairball gastritis, and the possibility of trichobezoar obstruction should be considered.

Access to foreign bodies or toxins is an important aspect of the clinical history. Has the cat been seen playing with an insect, mouse, or other prey? Are there any medications unaccounted for (e.g., a medication tablet dropped on the floor)? Are lilies present in the house?

Vomiting is the major sign of gastric disease but given the number of potential organ systems that can be involved, a thorough physical examination should be undertaken. Because linear foreign bodies are a common cause of vomiting, all cats presenting for anorexia or vomiting should have the underside of the tongue evaluated for the presence of string caught there. Applying gentle pressure with a thumb in the intermandibular space to elevate the tongue is an effective way to visualize lesions or foreign bodies in the sublingual area (see Chapter 3: Deciphering the Cat: The Medical History and Physical Examination, Fig. 3.9).

A thorough examination may reveal specific signs, such as a palpable thyroid nodule and tachycardia in the case of hyperthyroidism or palpably small kidneys with chronic kidney disease. The author has found that some cats with dental disease can gorge their food, resulting in vomiting; paying attention to the state of the teeth and gums is important. Of course, some cats have multiple problems, and correction of dental disease may not resolve vomiting if there is a concurrent disease. In the examination, it is also important to note consequences of both the underlying process and the vomiting itself; these include the demeanor of the cat, hydration status, and whether abdominal pain is present.

The physical examination findings, together with the clinical history, help determine the next appropriate steps. Well cats that are not continually vomiting and are appropriately hydrated, with no other specific signs, may be treated as outpatients by fasting for 24 hours, then returning to food with a bland diet, such as plain cooked chicken or commercial, low-residue prescription diets designed for this purpose. Follow-up is important to ensure signs do not progress. Cats with nonspecific signs may require supportive care with subcutaneous or intravenous fluids and perhaps analgesia (with an opioid). If clinical signs do not resolve, the pursuit of a specific diagnosis should be attempted. The practitioner must ask the following important questions:

Radiography is most useful for identifying foreign bodies or signs of intestinal obstruction from other causes. The major findings are noted later in the section on Intestinal Obstruction. Contrast radiography can aid in the diagnosis for both discrete and linear foreign bodies but should be used with caution, because intestinal perforation may be present. Nonionic iodinated agents that are typically used for myelography (such as iopamidol or iohexol) should be used because barium irritates the peritoneum and oral iodine compounds are hypertonic. Hypertonic compounds may draw fluid into the stomach and intestines after oral administration, with the potential of creating further fluid and electrolyte imbalances in an already compromised patient.8

Ultrasonography is a useful diagnostic adjunct and helps to detect and characterize localized thickening of the stomach or intestinal wall, lymphadenopathy, radiolucent foreign bodies, and changes in the size and echogenicity of the pancreas, liver, kidneys, or spleen. Abdominal effusions can be assessed and sampled. Ultrasound-guided fine needle aspirates (FNAs) can be used to sample masses, bile, or peritoneal fluid. It should be recognized that in most cases of GI disease, imaging will not give a definitive diagnosis and biopsy will be required using endoscopy, laparoscopy, or laparotomy. It is also important to recognize that a significant proportion (as much as 30%) of cats may have a histologic diagnosis of GI disease but ultrasonographically normal small intestines.⁹

Ultrasonography can be a considered a way to “survey the field,” assessing:

Histologic evaluation of affected tissue is usually needed for diagnosis of most chronic GI diseases. Intestinal biopsy samples can be obtained by of endoscopy, laparotomy, or laparoscopy, each of which has advantages and disadvantages. Laparotomy allows gross examination of and access to the entire intestinal tract as well as other abdominal organs. Laparotomy is the most invasive alternative, but with careful anesthesia and analgesia, most cats recover uneventfully. One survey found that 83% of cats undergoing exploratory laparotomy survived the hospitalization, and although complications occurred in 26% of cats, these were more likely to be associated with the underlying disease process and not surgery or anesthesia.10

Laparoscopy is becoming more common but still is not readily available in most veterinary clinics. This alternative is less invasive and allows exploration of the abdomen but not as thoroughly as with laparotomy. Full thickness intestinal biopsies require exteriorization, although this is not necessarily required for other abdominal organs. There is the possibility of anesthetic complications associated with insufflating the abdomen.

Endoscopy is the least invasive procedure and is the only alternative that allows examination of the intestinal lumen. Equipment is available that allows access to all areas of the GI tract. However, available equipment and operator expertise may limit which areas of the feline GI tract can be examined and biopsied in many veterinary practices. In addition, endoscopy does not allow examination or sampling of any other part of the GI tract and does not enable full-thickness biopsy samples. One study found that, of cats investigated for GI disease, 9 of 33 cats (27%) had no pathology recognized proximal to the jejunum (i.e., the effective length of some endoscopes would have precluded diagnosis), and other organs were affected in 9 of 10 cats with inflammatory bowel disease (IBD) and 7 of 8 cats with intestinal small cell lymphoma.¹¹ Additionally, hypocobalaminemia, an important marker of GI disease, reflects distal small intestinal disease which would require, in many cases, ileal biopsies to diagnose (beyond the reach of some endoscopes). Careful case selection for endoscopy from survey ultrasonography can reduce the number of missed diagnoses from endoscopy, but the possibility remains depending on the available equipment.

The quality of endoscopically obtained biopsy samples varies greatly with the skill of the endoscopist. It has been stated that “it is exceedingly easy to take inadequate tissue samples with a flexible endoscope.”¹² In an assessment of endoscopically obtained biopsy samples, two laboratories were compared, one that received samples from any practitioner and the other that received samples only from practitioners trained to take, mount, and submit endoscopy samples. All slides were reviewed by three pathologists who found that, of samples from the first laboratory, 15% of the slides were considered inadequate for diagnosis, 71% were considered questionable, and only 14% were adequate. By comparison, in the second laboratory (with samples from experienced practitioners) 0% of slides were inadequate, 21% were questionable, and 79% were considered adequate for diagnosis.¹³ In the case of distinguishing between lymphocytic intestinal infiltrates (commonly known as IBD) and lymphocytic neoplasia (small cell lymphoma), endoscopically obtained samples can give an incorrect diagnosis.¹⁴ Many of these problems can be minimized with experienced operators and careful case selection from survey ultrasonography.