39 Colonic inflammatory bowel disease in a cat

Initial presentation

Diarrhoea, decreased appetite and weight loss

Signalment: 11-year-old, male neutered, domestic shorthaired cat, body weight 3.8 kg

Case history

The cat had a 1-month history of decreased appetite and weight loss, along with increasingly softer faeces.

The cat had been vaccinated within the past year, but had not been de-wormed for several years. His usual diet was a commercial canned cat food, fed two to three times per day. During the past month the owner had also been feeding him cooked ham and canned tuna to encourage his appetite.

Physical examination

Physical examination revealed the cat to be bright, alert and responsive. He was in slightly thin body condition (body condition score 4/9) and ap­peared well hydrated. His mucous membranes were pink with a capillary refill time of less than 2 seconds. Oral examination showed that most of his teeth were missing but was otherwise unremarkable.

Thoracic auscultation revealed a heart rate of 200 beats per minute with matched pulses. Heart and lung sounds and percussion and com­pression of the thorax were unremarkable. The respiratory rate was nor­mal at 32 breaths per minute. Abdominal palpation was not resented. There was possible abdominal lymph node enlargement. Rectal temper­ature was 38.3° C. The remainder of the physical examination was unre­markable.

Problem list and discussion of problems

• Diarrhoea

• Weight loss

• Decreased appetite

The diagnostic approach to diarrhoea usually begins with determining if the cause is large or small intestinal in origin.

Differential diagnosis

Large intestinal diarrhoea

•Inflammatory conditions

• non-specific colitis

• chronic inflammatory colitis, e.g. plasmacytic/lymphocytic, eosinophil­

ic, granulomatous, suppurative

•Infectious causes

•FIP

• feline leukaemia virus (FeLV)

• Salmonella

• Campylobacter

• Clostridium perfringens

•Parasitic

• whipworms

• hookworms

• Giardia

• Tritrichomonas foetus

• Toxoplasma gondii

•Diet related

• dietary sensitivity (allergy or intolerance)

• fibre responsive diarrhoea

•Neoplasia, e.g lymphoma, adenocarcinoma, others

•Systemic disorders

•Uraemia

• toxicities

• pancreatopathy

• Secretagogues, e.g. unconjugated bile acids, hydroxylated fatty acids sec­ondary to small intestinal disorders

Small intestinal diarrhoea

• Diet related

• dietary sensitivity

• food poisoning

• sudden change of diet

• Small intestinal disease

• inflammatory bowel disease, e.g. plasmacytic/lymphocytic, eosinophil­ic, other

• infectious (viral, bacterial enterotoxins, fungal - although fungal disor­ders of the small intestine are unlikely in the UK)

• parasites, e.g. Giardia, cryptosporida, Strongyloides, ascarids, hook­worms, Toxoplasma gondii

• neoplasia, e.g. lymphoma, mastocytosis

• lymphangiectasia (uncommon in cats)

• ileus, e.g. hypokalaemia, enteritis, dysautonomia

• antibiotic responsive diarrhoea

• Pancreatic disorders

• pancreatic exocrine insufficiency

• Chronic pancreatitis

• Liver disorders

• liver failure

• intrahepatic cholestasis

• bile duct obstruction

• Kidney disease and uraemia

• Hyperthyroidism

• Congestive heart failure

• Hypoadrenocorticism (uncommon in cats)

Case work-up

A 4- to 6-week dietary trial with a highly digestible restricted novel pro­tein or hydrolyzed diet is appropriate in some cases of diarrhoea.

Minimum data base

Routine haematology was performed and revealed a moderate mature neutrophilia (21.7 ? 10⁹∕l; reference range: 2.5-12.8 ? 10⁹∕l) and a mild monocytosis (1.06 ? 10⁹∕l; reference range: 0.07-0.85 ? 10⁹∕l). Blood smear analysis confirmed these findings and showed atypical, re­active appearing lymphocytes, suggestive of antigen stimulation.

Serum biochemistry results revealed a marginal increase in urea (9.9 mmol/l; reference range: 2.8-9.8) and bile acids (7.2 mmol/l; ref­erence range 0-7) and a marginal hypophosphataemia (1.39 mmol/l; reference range: 1.4-2.5). Mild hypoalbuminaemia (24.0 g/l; reference range: 28-39) was also present.

Clinical tip on decreased serum albumin

Decreased serum albumin can be due to decreased production by the liver, increased loss via the intestines or kidneys or a ‘third space shift’ (e.g. into an obstructed loop of intestine, the pleural space or the peritoneal space). Pro­duction may also be decreased in inflammatory states, as it is a negative acute phase protein and decreases whereas production of some of the other proteins increases. After checking for urinary loss (a urine protein to creatinine ratio), further diagnostics involve looking for evidence of hepatic or gastrointestinal disorders or inappropriate fluid accumulation.

To assess the pancreas, serum samples were submitted for measure­ment of feline pancreatic lipase (fPL) and trypsin-like immunoreact­ivity (TLI) which were both found to be within the reference range (fPL: 1.2 μg∕l; reference range: 0.1-3.5; TLI: 22.5 μg∕l; reference range: 12-82).

Both serum folate (4.2 μg∕l; reference range: 9.5-20.2 μg∕l) and ser­um cobalamin (186.0 ng/l; reference range: 270-1000 ng∕l) concentra­tions were decreased and supplementation was initiated.

Clinical tip on serum folate and cobalamin

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 or 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 gastrointestinal 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 treatment of gastrointestinal disease in humans ex­ceeds the recommended daily amounts and there is a consideration that there may be positive pharmacological effects.

Folate is absorbed only in the proximal intestine. A deficiency usually in­dicates small intestinal disease and if it is accompanied by a cobalamin de­ficiency it likely indicates widespread disease. A high serum folate can be caused by bacterial production, although serum concentrations of this vitam­in can also be increased by dietary intake.

Serum T4 was at the low end of the reference range at 15.3 nmol/l (reference range: 15-48 nmol/l). An feline immunodeficiency virus (FIV)∕FeLV ELISA was performed which was negative for FeLV but pos­itive for FIV antibodies.

Toxoplasma serology showed a negative IgM titre (1 : 64 or a four-fold or greater increase in paired (2 to 3 weeks apart) IgG titres is likely to indicate disease. The absence of the titre increases does not rule out toxoplasmosis as some cats and dogs with the disease will undergo an antibody class shift from IgA to IgM. A response to treatment (e.g. clindamycin) is diagnostically support­ive (although not definitive of diagnosis) if there is a suspicion of disease.

Urinalysis showed a urine specific gravity of 1.048, indicating good urine concentrating ability. The chemistry strip was unremarkable, and the urine sediment was inactive. Urine protein to creatinine ratio was 0.13 (reference range there were no obvious mass lesions or ulcerated areas. Biopsy samples were collected from the stomach, duodenum and colon. While the cat was anaesthetized for endoscopy, fine needle aspirates of an en­larged mesenteric lymph node and the thickened colonic wall were also taken under ultrasound guidance and submitted for cytological evalu­ation.

Fig 39.3

Endoscopic picture of colonic mucosa showing thickening and loss of visualization of submucosal vessels

Cytology of the lymph node aspirate was suggestive of reactive hyper­plasia. The colonic wall cytology was, unfortunately, non-diagnostic.

Histopathological examination of the gastric mucosal biopsies re­vealed the presence of some Helicobacter-like spiral organisms at the sur­face of the gastric mucosa. There was no associated gastric inflammation and it was therefore considered an incidental finding.

Clinical tip on gastric Helicobacter

A causal role of Helicobacter in chronic gastritis and vomiting in dogs and cats has not been established, although there are cases in which treatment im­proves the clinical condition.

The small intestinal mucosal biopsies revealed evidence of mild, dif­fuse chronic enteritis. Histopathology of the colonic mucosal biopsies showed severe, multifocal, granulomatous ulcerative colitis (Fig 39.4). There was no evidence of any aetiological agents and Ziehl-Neelsen stains of the colonic biopsies for the presence of acid fast (i.e. mycobac­terial) organisms were negative.

Fig 39.4

Histopathology of the colon showing severe, multifocal, granulo­matous ulcerative colitis

(courtesy of Professor Elspeth Milne)

Treatment and outcome

This cat was diagnosed with a granulomatous ulcerated from of colonic inflammatory bowel disease, complicated by a positive FIV status. The FIV may either have caused or contributed to the cat’s clinical condition. The enteritis in the small intestine was thought to be of less significance, although may have contributed to decreased nutrient absorption.

Initial treatment included:

• Prednisolone: 5 mg po q 24 hours

• Marbofloxacin: 7.5 mg po q 24 hours

• Folic acid: 2.5 mg po q 24 hours

• Vitamin B12: 300 μg sq every 7 days for 3 weeks

• A novel restricted protein, highly digestible canned diet

Clinical tip on fluoroquinolone use in cats

In some cats given enrofloxacin, retinal degeneration leading to partial, temporary or total blindness has occurred. This reaction is not common even with very high doses, but there is no way to predict which cats will react. This reaction has only been reported with enrofloxacin and not with other fluoroquinolones, as it is theorized that the biochemical structure of enro­floxacin leads to especially high concentrations in the feline eye. Because of the potential adverse reactions to enrofloxacin in cats, marbofloxacin was ini­tiated in this cat prior to the results of the periodic acid-Schiff tests in the chance that similar pathophysiology to the histiocytic colitis of Boxer dogs might be present.

At the time of discharge the cat was very bright, with a good appetite, having gained 500 g since admission and with only intermittently soft stools.

Two weeks later the owners reported that the cat had done very well; his faecal quality was improving and he had gained some weight. After the marbofloxacin was stopped, the cat immediately showed signs of diarrhoea again and it was re-instituted 2 days later. The cat again im­proved and has remained well while continuing on marbofloxacin.

Pathophysiology and prognosis

In general, the more common forms of inflammatory bowel disease, with infiltration of lymphocytes and plasmacytes or even eosinophils, carry a relatively good prognosis for improvement in clinical signs.

Granulomatous colitis or enteritis, however, has a more guarded pro­gnosis. Granulomatous colitis is characterized by the presence of aggreg­ates of histiocytes in the lamina propria. In this cat the infiltration of the mucosa and lamina propria was described as predominantly large mac­rophage like cells, which may have been a histiocytic type of cell. The presence of underlying infectious causes (e.g. mycobacterial organisms, parasitic organisms, feline infectious peritonitis or fungal infections, al­though the latter are uncommon in the UK) should be ruled out be­fore treatment with corticosteroids or other immunosuppressive drugs is used. Metronidazole is commonly used in feline chronic colitis, as it has multiple effects: antibiotic, antiprotozoal and inhibition of some aspects of cell mediated immunity.

An ulcerative histiocytic colitis has been reported in young Boxer dogs, which presents with thickened colonic mucosa and haemorrhage. This disorder shows a cellular infiltrate of plasma cells, lymphocytes and periodic acid-Schiff positive macrophages. The presence of the period­ic acid-Schiff positive macrophages is a discriminating feature between this form of colitis and granulomatous colitis.

An infectious aetiology is suspected for this histiocytic disorder and treatment of cases early in the course of disease with enrofloxacin has been successful. Treatment is lifelong in these cases.

Cats with FIV show a significant incidence of dental disease (50-52% of seropositive cats) and most of the teeth in this cat had been lost or removed. A significant number (15-20%) of seropositive cats show chronic enteritis or enterocolitis. Clinical signs include anorexia, chronic diarrhoea, dehydration and weight loss. The diarrhoea may be persistent and, as in this cat, intestinal thickening develops. A high mortality rate is seen in FIV positive cats with gastrointestinal signs.