34 Corticosteroid induced gastrointestinal ulceration in a dog
Initial presentation
Weakness, lethargy, muscle wasting, soft dark faeces
Signalment: 7-year-old neutered female Labrador retriever, body weight 21.8 kg
Case history
This dog had a history of immune mediated thrombocytopenia the previous year, which had responded to oral methylprednisolone. Two months prior to admission her platelet count had dropped to 136 × 109/l (reference range 200–500 × 109/l) and the referring veterinary surgery had again initiated oral methylprednisolone at 1.5 mg/kg body weight divided into two treatments per day. She had been maintained on this dose. Serum chemistry performed by the referring veterinary surgery had documented increased alanine aminotransferase (ALT) and alkaline phosphatase (AP), although the values were not recorded.
The owner was concerned that the dog was very lethargic and had very poor exercise tolerance. She reported that the dog had increased urination and thirst and a very good appetite. She was not vomiting, although had had several episodes of diarrhoea with soft, dark faeces.
The dog’s usual diet was a low calorie dry food and she was normally fed twice a day. She had previously been on glucosamine and chrondroitin sulphate for arthritis, but these had not been administered during the previous 2 months. She was on no other medications or supplements. She was current on her vaccinations but had not been de-wormed for about a year.
Physical examination
The dog was quiet but responsive. Her body condition score was approximately 5/9, although this was hard to determine as she had moderate muscle wasting with retention of body fat.
Her capillary refill time was less than 2 seconds. Her mucous membrane colour was pale pink and her membranes were tacky. She was estimated to be about 6% dehydrated.
Thoracic auscultation revealed normal heart and lung sounds, with a heart rate of 76 beats per minute and a respiratory rate of 14 breaths per minute. There was no evidence of pain on abdominal palpation, but the abdomen was pendulous and felt soft. Her rectal temperature was 38.4° C. Her coat was dry and showed evidence of seborrhoea.
Problem list and discussion of problems
Differential diagnosis
Many of this dog’s problems may have been due to the administration of corticosteroids, but they were still explored as this assumption can result in missing a disorder.
Lethargy and exercise intolerance have many differential diagnoses, but for this dog the list included anaemia, hepatopathy, electrolyte disturbances, hypoglycaemia, corticosteroid induced myopathy, cardiopulmonary disorders and renal disease.
The slightly tacky membranes were likely indicative of mild dehydration due to the polyuria.
The pale mucous membranes may have been due to poor perfusion or anaemia. The heart sounds were regular and on palpation her pulses felt normal, making anaemia the more likely diagnosis. Anaemia may be divided into non-regenerative or regenerative, which is determined by performing a reticulocyte count. Non-regenerative anaemias are due to systemic diseases suppressing bone marrow function or primary bone marrow disorders. Regenerative anaemias are due to blood loss or haemolysis. Gastrointestinal blood loss is always a potential problem in animals on corticosteroid treatment.
The muscle wasting was typical of that induced by corticosteroids, but can also be caused by myopathies or weight loss due to illness, where muscle loss can be more prominent than fat loss.
The pendulous abdomen on this dog may have been due to the administration of corticosteroids, which cause muscle weakness and abdominal deposition of fat. Other causes for the abdominal enlargement included ascites or organomegaly.
The polyuria and polydipsia are common side effects of corticosteroids, but other common or concurrent disorders like renal disease, urinary tract infection, endocrine disorders or electrolyte disturbances were also included in the differential diagnoses list.
The elevation in liver enzymes may be due to corticosteroids or primary or secondary liver disorders.
Dark faeces can indicate melaena (the presence of digested blood in the faeces). Usually the stools are described as being dark and tarry. The black colour is a result of the oxidation of haemoglobin and the tarry appearance is from the bacterial breakdown of haemoglobin. Generally melaena is thought to be from bleeding from the upper intestinal tract or from the ingestion of blood (e.g. from epistaxis or oral lesions). Blood must be present in the gastrointestinal tract for several hours (8 hours in humans) before the colour turns black, so a rapid transit time of blood may not show melaena and a very slow transit time may show as melaenic faeces from a bleed in the lower gastrointestinal tract.
Clinical tips for diagnosing gastrointestinal bleeding
In dogs 350 to 500 mg of haemoglobin per kilogram of body weight must enter the gastrointestinal tract before melaena is seen, so gastrointestinal bleeding without the overt presence of melaena is very possible. A faecal occult blood test is useful to rule out melaena.
With chronic gastrointestinal bleeding, iron is lost from the body and an iron deficient anaemia may develop. Iron deficiency anaemias become microcytic and hypochromic. More acute bleeding can cause a significant drop in the packed cell volume (PCV), even within hours.
The serum urea nitrogen to creatinine ratio increases with upper gastrointestinal bleeding due to the absorption of blood protein. An increased serum urea with a creatinine within the reference range (or other similar disproportionate changes) should prompt the clinician to check for gastrointestinal bleeding. The use of diuretics can also cause this change.
Faecal occult blood tests using orthotolidine or guaiac tablets are qualitative and only moderately sensitive. It is recommended to feed a meat-free diet (e.g. cottage cheese and rice) for 3 days prior to collecting the faecal sample as the myoglobin from meat in the diet may interfere with the test, causing a false positive.
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