Hypoadrenocorticism in a dog

14 Hypoadrenocorticism in a dog




Initial presentation


Vomiting, weakness and lethargy


Signalment: 6-year-old neutered female cocker spaniel, body weight 17 kg



Case history


The dog had become lethargic during the past month and was vomiting digested food 3 to 4 times a week. Her exercise tolerance had decreased over the last 1 to 2 months. Her stools varied between normal and soft. The owner was unsure if the dog’s drinking and urination patterns had changed.


The dog was de-wormed regularly with fenbendazole and she was vaccinated yearly.


Her usual diet was a high quality dry food and she was also given snacks and treats regularly. She was on no medications or supplements.



Physical examination


The dog was very depressed at presentation. Her body condition score was 4/9 with evidence of recent weight loss. Her mucous membranes were tacky; capillary refill time was 3 seconds. Peripheral pulse quality was weak, but there was a pulse for every heart beat. There was a slight loss of skin elasticity. Based on these findings, she was estimated to be approximately 7% dehydrated.


Peripheral lymph nodes were unremarkable. Thoracic auscultation revealed normal heart and lung sounds, with a heart rate of 56 beats per minute (bpm). This heart rate was thought to be too slow for the degree of dehydration. She had a respiratory rate of 36 breaths per minute and her rectal temperature was 38.9° C.



Problem list and discussion of problems



• Vomiting

• Decreased exercise tolerance

• Slow heart rate, especially for hypovolaemia


Differential diagnosis


Differential diagnoses for vomiting in this dog include the following disorders:


• Disorders of the stomach
• foreign body

• gastritis

• ulceration

• chronic partial dilatation-volvulus

• neoplasia

• Disorders of the small intestine
• foreign body

• inflammatory bowel disease

• neoplasia

• parasites

• intussusception (unlikely)

• Disorders of the large intestine
• colitis

• obstipation

• Systemic disorders
• pancreatopathy

• hypoadrenocorticism

• diabetes mellitus

• liver disorders

• peritonitis

• renal disease/uraemia (unlikely)

• Dietary causes
• adverse reaction to food (allergy or intolerance)

• dietary indiscretion

Most dogs with intussusception are less than 1 year of age, although it is still a possible diagnosis in a dog of this age.


Differential diagnoses for decreased exercise tolerance in this dog include:


• Cardiovascular disease

• Neuromuscular disorders such as myasthenia gravis, peripheral neuropathies, brain or spinal cord disease, myopathies

• Respiratory disorders

• Electrolyte disorders, e.g. hypo- or hyperkalaemia, hypo- or hypernatraemia, hypocalcaemia

• Endocrine diseases such as diabetes mellitus, hypothyroidism, hypoglycaemia, hypoadrenocorticism

• Infectious disease

• Anaemia

• Nutritional deficiencies or malassimilation of nutrients

• Neoplasia

• Medications or toxins; however, the dog had no history of ingestion of these

• Pain – although there was no evidence of pain on physical examination, this can be subtle

A heart rate of 56 bpm is considered bradycardic for a medium sized dog and the degree of hypovolaemia would be expected to have increased the rate. Possible causes for the bradycardia include:


• increased vagal tone

• hypothyroidism

• sinus node disease (sick sinus syndrome)

• sinus block due to atrial disease

• atrial standstill (e.g. due to hyperkalaemia) or an atrioventricular heart block

Very fit dogs sometimes have a slow heart rate, but this dog did not appear fit and also had not been exercising normally for the past month or longer.



Case work-up


The dog was admitted to the hospital for diagnostic investigation and treatment of her dehydration. Intravenous balanced electrolyte crystalloid fluids were initially started at 85 ml/hour, calculated to correct her dehydration over 24 hours.



Nursing tip on intravenous fluid therapy


Fluid therapy needs to take into account the amount needed for maintaining normal hydration and replenishing the amount lost. Maintenance fluids are usually calculated at 40 to 60 ml/kg per 24 hours or 1.6 to 2.5 ml/kg/hour. In this 17 kg dog, that was approximately 34 ml/hour. To replete the amount of fluid deficit, the dog’s body weight is multiplied times the estimated amount of dehydration, e.g. 17 × 0.07 = 1.19 kg or 1.19 l in 24 hours. This is 1190 ml in 24 hours or about 50 ml/hour. Adding the 34 ml plus 50 ml is 84 ml/hour. The pet’s hydration should be assessed several times during fluid administration as sometimes hydration improves before this total amount is given. If the pet is vomiting or has diarrhoea, sometimes additional fluid needs to be given to make up these ongoing losses.

Related posts:

  1. Oesophageal stricture in a cat
  2. Vomiting
  3. Linear foreign body in a cat
  4. Intussusception in a cat

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Sep 22, 2016 | Posted by in SMALL ANIMAL | Comments Off on Hypoadrenocorticism in a dog

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