15 Lymphocytic inflammatory bowel disease/al- imentary lymphoma in a cat

Initial presentation

2 months of intermittent vomiting, with recent increase in frequency

Signalment: 9-year-old neutered male domestic shorthaired cat; body weight

3.9 kg

Case history

The cat presented with a 2-month history of vomiting and an increasingly poor appetite.

His previous diet was a commercial dry food supplemented once a day with canned food. During the time his appetite was decreasing the owner had been tempting him with cooked chicken and ham.

His vaccinations were up to date and he had been treated for parasites 3 months prior to presentation. He had not travelled outside of the UK.

Physical examination

On physical examination the cat was bright and alert, but seemed to tire quickly. His body condition score was 3/9. His mucous membranes were pink but slightly dry and capillary refill time was infectious, e.g. bacteria, viral, fungal

• gastrointestinal (GI) parasites

• inflammatory bowel disease

• infiltrative neoplasia, e.g. lymphoma, mastocytosis

• high partial obstruction, e.g. intussusception, foreign body

• Systemic disease

• uraemia

• liver failure

• sepsis

• congestive heart failure

• acidosis

• hypoadrenocorticism

• ketoacidotic diabetes mellitus

• hyperparathyroidism

• gastrinoma

• Neurological diseases (no other signs consistent with these in this cat)

• dysautonomia

• vestibular disease

• CNS disease

• Drugs, toxins (no known history of drug or toxin exposure)

Case work-up

Minimum data base

Haematology, serum chemistry, urinalysis and faecal examination were preformed.

Haematology results were within the reference ranges. Serum chem­istry showed a mild decrease in albumin to 24 g/l (reference range 28-39 g/l), and mild hyperglycaemia of 6.7 mmol/l (reference range 3.0-5.0 mmol/l), which was thought to be likely due to stress. Serum total thyroxin was within the reference range at 17.5 nmol/l (reference range 13-48 nmol/l).

The serum cobalamin concentration was decreased to 177 ng/l (refer­ence range 251-908 ng/l) and folate was decreased to 6.4 μg∕ml (refer­ence range 9.7-21.6 μg/^.

Clinical tip: folate and cobalamin (vitamin Bι₂)

Cobalamin is absorbed in the ileal part of the small intestine. It requires prior binding with intrinsic factor, which comes from the pancreas in cats and the stomach and pancreas in dogs. Deficiency may be caused by poor ab­sorption due to intestinal disease, exocrine pancreatic insufficiency, excessive bacteria in the upper small intestine utilizing the vitamin, or a deficiency in intrinsic factor. In humans who are vegetarians (especially elderly humans), a dietary deficiency is possible; however, this is unlikely in cats as they cannot successfully be vegetarians.

Unlike most other B vitamins, cobalamin is stored in the body. In healthy cats the half life is 11 to 14 days and in cats with GI disease it is only 4.5 to 5.5 days. Clinical signs of cobalamin deficiency in humans include anaemia, thrombocytopenia, neuropathies and digestion abnormalities. In cats (and dogs) the clinical signs are not as well described; however, it has been sugges­ted that response to treatment of intestinal disorders is improved with cobal­amin repletion. A high serum concentration of cobalamin does not appear to have clinical significance and may occur with supplementation. The recom­mended dose for supplementation in humans exceeds the amounts needed to reach serum reference ranges and there is a consideration that there may be positive pharmacological effects.

Folate is absorbed only in the proximal intestine.

caused by bacterial production, although serum concentrations of this vitam­in are sensitive to food intake and a high dietary intake can also increase the serum concentration (Fig 15.1).

Serum titres for Toxoplasma gondii were zero for IgM and 100 for IgG, inconsistent with the presence of this organism. Blood test results for feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) were also negative.

Urinalysis showed a urine specific gravity of 1.026. The chemical strip analysis results were within reference ranges and the urine sediment was inactive. Urine protein to creatinine ratio was within the reference range (as the intestine is nourished by the luminal presence of nutrients, especially glutamate in the small intestine.

The estimation of caloric requirements for hospitalized patients is based upon the resting energy requirement, which is in kcal 70 ? body weight in kilograms⁰-⁷⁵. The presenting weight is used initially, rather than the optimal weight. In this cat, this value was:

The estimated amount to initiate feeding was decreased to one-third of this amount, or 65 kcal to decrease the risk of the re-feeding syndrome. The key tips for nutritional supplementation of sick animals are to feed early and to try to not feed too much.

As this cat was vomiting, the provision of oral or gastric nutrition could have been difficult. Constant rate intravenous metoclopramide was admin­istered with his intravenous fluids at a rate of 1 mg/kg/24 hours.

The initial feeding attempted was the use of a complete and balanced liquid food containing 1 kcal/ml.

A naso-oesophageal tube could have been placed to feed the cat; however, there was a risk of vomiting the tube and having it displaced into the trachea. If the cat had not started eating, placement of a jejunostomy tube and/or in­travenous parenteral nutrition would have been indicated.

By the end of the first week, the cat was eating a complete canned food in adequate amounts and had only vomited on days 4 and 6. He was discharged on oral medications, with repeat visits for evaluation and cobalamin administration.

He gained 0.6 kg over the 2 months following diagnosis and the owner reported that he vomited only once or twice a week and was much brighter and more active. His urine specific gravity did not increase above 1.030; however, he did not become azotaemic and his kidney dis­ease appeared stable. He was lost to follow-up 1 year after the tentative diagnosis of intestinal lymphoma.

Discussion and epidemiology

As more cats are vaccinated for FeLV, the more common site of feline lymphoma has shifted from the mediastinal form to the GI form, which most often affects the small intestine. Cats with GI lymphoma have a lower incidence of FeLV (15%) infection than do cats with other forms of lymphoma (20-85% depending upon the site), although the true in­cidence might be higher if more sensitive tests were used (e.g. PCR test­ing).

The most common age range of cats with GI lymphoma is 9 to 13 years. There is no evidence of a breed predilection, but male cats are slightly more likely to develop the disease. As in this cat, the signs are chronic and often include a poor appetite and weight loss.

Some cases show a non-regenerative anaemia consistent with anaemia of chronic disease or bone marrow infiltration of the tumour in cases with FeLV. Mild to moderate hypoalbuminaemia is often present; however, this is common with many diseases of the small intestine. In some cases liver involvement in the neoplasia results in increased liver enzymes.

Low serum cobalamin and folate are present in many cases, but again, this is true of many small intestinal diseases where absorption is de­creased.

The increased intestinal wall thickness is characteristic, but does not differentiate GI lymphoma from inflammatory bowel disease. The dis­ruption of normal intestinal wall layering is usually more pronounced with lymphoma than other inflammatory bowel disease. The increase in mediastinal lymph node size is a non-specific finding common in many abdominal disorders.

Histology of GI biopsies is needed for a definitive diagnosis, but even then the diagnosis can be difficult. There are three grades of GI lymph­oma: • Low - lymphocytic or small cell

• Intermediate • High - lymphoblastic, immunoblastic or large cell.

It can be extremely difficult, even with histopathology, to differentiate low grade small cell lymphoma from lymphocytic inflammatory bowel disease. Many clinicians believe that inflammatory bowel disease may lead to lymphoma in some cases. CD79a (B-cell) and CD3 (T-cell phen­otype) antibody stains can be used to assess B- and T-cell immunoreact­ivity to help differentiate between the disorders. A predominance of one type of cell is more likely to be tumour and a mixed population more likely to be IBD. While an aid in diagnosing, the type of tumour cell (B versus C) does not correlate to response to therapy or survival time in cats.

Treatment discussion

Various chemotherapy protocols have been used for GI lymphoma; these include various combinations of cyclophosphamide, vincristine, prednisolone, L-asparaginase, doxorubicin and methotrexate. Remission rates with these protocols are difficult to interpret as many studies do no include the histological grade of the disease and remission rates are better for low grade small cell lymphoma.

Cats with low grade lymphoma, such as this cat, can often have a good response to the less aggressive chemotherapy protocol of chlorambucil and prednisolone with less risk of serious side effects. A remission rate of 69% has been reported with this treatment in these cases, with a me­dian survival time of 17 months. Cats which achieve complete remis­sion have better survival times. It may be that some of the cats treated for small cell lymphoma have a form of inflammatory bowel disease; however, the treatment appears to be appropriate for either disorder.