Disorders Causing Vomiting in Cats
Todd R. Tams, DVM
Vomiting is a frequent presenting complaint in cats seen in clinical practice. It can result from disorders of many body systems, and each vomiting patient should be evaluated systematically to obtain a diagnosis. Many clinically significant vomiting associated disorders in cats can be diagnosed and managed successfully.
Cats vomit for many reasons including food sensitivity (one of the most common causes), ingestion of irritants such as grass or plants, infectious diseases, parasites (both GI and heartworms), gastric disorders, pancreatitis, liver disease, inflammatory bowel disease, metabolic disorders, GI foreign bodies, and neoplasia. Hairballs are almost certainly over diagnosed as a cause of vomiting. Cats that eat grass or plants may vomit intermittently, and clinicians are frequently faced with the frustrating task of trying to determine why some cats routinely vomit once or twice a week but never lose condition or appear sick. Unexplained vomiting should be called just that, not "gastritis", unless a specific tissue diagnosis confirms the presence of that lesion.
These notes will not involve a comprehensive discussion of all the causes of vomiting in cats but rather will specifically describe several causes of vomiting in the cat related to gastric disorders which probably occur more frequently than they are diagnosed. Selected other disorders will be discussed as well.
There are few reports of chronic gastritis in cats, but it is being diagnosed more frequently as vomiting cats are more thoroughly evaluated (i.e., by obtaining gastric biopsies). Most lesions probably occur as a result of a variety of extrinsic influences, particularly with repeated exposure, resulting in damage to the gastric mucosa. Immune mechanisms or allergic conditions may also be a cause. More recently Helicobacter has been implicated as a cause of gastritis in some cats. The inflammatory component in gastritis may consist of lymphocytes, plasma cells, eosinophils, neutrophils, or histiocytes or various combinations of these cell infiltrates.
Intermittent vomiting is usually the predominant presenting complaint. There may be a long history of infrequent vomiting over months to years followed by a gradual increase in frequency leading up to the time of presentation. Alternatively, there may be a short history of frequent vomiting that does not respond to symptomatic therapy. Mild weight loss may be evident, and occasional vomiting of small amounts of blood tinged fluid may occur. As the disease becomes more severe the predominant clinical signs often include listlessness, weight loss, and inappetence. Frequently this is the point at which clients become alarmed and seek veterinary attention. A work-up should be expedited so that definitive treatment can be initiated as soon as possible. Greater degrees of disease activity may be significantly more difficult to control on a longterm basis.
Baseline tests including CBC, biochemistry profile, serum thyroxine (TT4), heartworm testing, urinalysis, and fecal examination are helpful in ruling out a variety of disorders that can cause vomiting. In cats with chronic gastritis these tests are usually normal or negative. Fecal examinations should be done routinely. Survey radiographs are often unrevealing while barium series occasionally will delineate filling defects or prolonged retention of barium in the stomach. Radiographs are of value, however, in helping to rule out the possibility of a foreign body. Ultrasonography may or may not reveal a thickened gastric wall. Definitive diagnosis of chronic gastritis is only established after examination of biopsy specimens. Biopsies are most easily and safely obtained via endoscopy. Mucosal appearance at endoscopy may range from normal to irregular, follicular, or erosive. Many clients that are reluctant to permit laparotomy to obtain biopsies will readily allow endoscopic examination because it can be done quickly and with less trauma to the patient. If an endoscope is not available, surgical biopsies should be considered. If clinical signs warrant a laparotomy, always obtain biopsies whether or not serosal examination and gastric palpation are abnormal. In most cases involvement is limited to the gastric mucosa and frequently no abnormalities are noted on external evaluation of the stomach at laparotomy.
The pathologist should give a complete description of the degree of change from normal and the type of cell infiltrate that is present in the gastric mucosa. The degree of change (e.g., mild, moderate, severe) is important in determining how aggressive therapy should be at the outset. In addition, moderate to severe chronic gastritis usually requires longterm (possibly lifelong) therapy. A simple diagnosis of "chronic gastritis" from the pathologist is not adequate.
Treatment includes antiinflammatory therapy (prednisolone is usually effective) and dietary management (feed a diet with a novel protein source).
Gastric Motility Disorders
Gastric motility disorders cause delayed gastric emptying. Stress, trauma, psychogenic causes, hypokalemia, hypothyroidism, chronic gastritis, and anticholinergic drugs can decrease gastric motility and delay the rate of gastric emptying. Gastric motility disorders do not occur as commonly in the cat as they do in the dog.
Cats with chronic hairball problems may have a primary gastric motility disorder. Unlike in humans and dogs migrating motor complexes ("housekeeper contractions") do not occur in cats. These are sweeping contractions that occur during the interdigestive phase and their purpose is to evacuate nondigestible material from the stomach between meals. The absence of "housekeeper contractions" may promote retention of hair material in cats with hairball problems.
Common clinical signs of a gastric motility disorder include vomiting undigested material 6 to 12 hours after eating, periodic bloat and inappetence, intermittent nausea, and vomiting bile. Many times these disorders are responsive to promotility therapy with either metoclopramide (Reglan) or cisapride (Propulsid).
Inflammatory Small Bowel Disease
Inflammatory small bowel disease is a frequent cause of chronic vomiting in cats. Biopsy is required for diagnosis. Treatment protocols are described in various textbooks.
Gastric neoplasia is rare in the cat. Of those cases recognized, lymphosarcoma is the most common and may involve only the stomach or may affect other organs as well. The majority of cats with gastric lymphosarcoma are FeLV negative. Intestinal lymphoma is not uncommon in cats. Some cats have a low grade lymphoma that is not associated with any masses. Clinical signs can be exactly the same as cats with inflammatory bowel disease. This highlights the importance of obtaining biopsies of the stomach and intestines in cats with unexplained vomiting and/or diarrhea.
Vomiting is the most consistent clinical finding in cats with gastric LSA. The vomiting may vary in both the frequency and onset after eating and hematemesis occasionally occurs. Diarrhea and weight loss may be evident if there is intestinal involvement as well.
Diagnosis is confirmed only by biopsy, either obtained at endoscopy or laparotomy. Lesions may include small discrete raised masses or involve a diffuse infiltration of the gastric wall. The gastric mucosa may even appear grossly normal.
Pre-treatment work-up should include a CBC, blood chemistry profile, TT4, FeLV and FIV determination, and urinalysis.
Treatment involves chemotherapy. Some cats respond very well to chemotherapy. Various protocols have been published. I commonly use a combination of cyclophosphamide, vincristine, and prednisolone.
Feline Heartworm Disease
Acute or chronic vomiting is a fairly common clinical sign in cats with heartworm disease. Vomiting or respiratory signs are the predominant clinical complaint in chronic disease. The vomiting tends to be sporadic and can be related to eating. Vomitus usually consists of food or foam and bile or blood are rarely present. In endemic areas heartworm disease should be considered as one of the primary differential diagnoses in cats presented with the problem of chronic vomiting. In areas where heartworm disease is not common it should be considered as a possibility in cats with chronic vomiting that is not due to disorders such as inflammatory bowel disease, hyperthyroidism, chronic gastritis, chronic pancreatitis, motility disorders, etc.
Respiratory signs that may be observed include coughing, intermittent dyspnea, and occasional hemoptysis. Nonspecific clinical signs include anorexia or lethargy (these may be the only presenting signs in heartworm-infected cats).
Cats with heartworm disease are also at risk for sudden death.
Kidney disorders, such as acute renal failure (always consider the possibility of ethylene glycol intoxication), chronic renal disease, and pyelonephritis frequently cause vomiting in cats. Vomiting cats should be routinely evaluated by CBC, biochemical profile, AND urinalysis testing as an initial screening. Both BUN and serum creatinine concentrations are, at best, only crude reflections of glomerular filtration rate. In the presence of abnormal renal function neither value will rise above the normal range until approximately three-fourths of renal function is lost. Conversely, both values will rise under conditions that cause a decrease in glomerular filtration rate despite normal renal function (prerenal or postrenal azotemia). In prerenal azotemia the BUN and creatinine may be significantly elevated but the urine specific gravity will usually be quite high (cats have the ability to normally produce very concentrated urine) as well. It is extremely important that a urinalysis (especially urine specific gravity) be evaluated in conjunction with BUN and creatinine values when trying to differentiate prerenal from primary renal azotemia. A patient may be mistakenly diagnosed as being in renal failure when in fact marked prerenal azotemia due to dehydration may be the cause of elevated BUN and creatinine values.
Prerenal azotemia is most commonly the result of either hypovolemia secondary to dehydration or blood loss, or decreased renal blood flow due to shock or heart failure. Cats are able to produce urine with a specific gravity of 1.080. In cats normal urine concentrating ability is indicated by a urine specific gravity greater than 1.035.
Cats with chronic renal failure have elevated BUN and creatinine levels and a urine specific gravity of less than 1.035 (often less than 1.025). Recommended treatment of vomiting due to uremic gastritis includes: 1) NPO, 2) IV fluids, 3) an H2-receptor blocker such as cimetidine (initial dose 5 mg/lb IM followed by 2.5 mg/lb IM BID) or preferably famotidine (Pepcid) at 0.25 mg/lb IV BID, 4) antiemetic therapy (chlorpromazine 0.1-0.2 mg/lb IM SID-TID, lower dose is generally used to minimize sedation), and 5) sucralfate for gastric mucosal cytoprotective effect if there is hematemesis (125-175 mg PO QID). Famotidine is usually continued for 7-10 days total and chlorpromazine is discontinued 24-48 hours after vomiting has stopped. Famotidine is continued longterm in cats that have a decreased appetite. Diuresis, of course, with IV fluids is the cornerstone of treatment for decompensated chronic renal failure. Dietary management, control of serum phosphorus levels (e.g., Dialume 1/4-1/6 capsule mixed with each meal or Alternagel 2-3 cc per meal), and in some cases maintenance fluid therapy in the form of SC fluids administered by the owner at home comprise treatment for compensated chronic renal failure.