Align-ju STUDENT
Aetiology
There are two recognised types of DM : type 1 is due to a lack of insulin production and type 2 occurs when the body produces insulin but the tissues do not respond normally and are said to be insulin resistant . Without management or treatment , a DM patient will become hypoglycaemic , so it is vital that these patients are closely monitored and stabilised .
In dogs , type 1 DM is more common than type 2 , and is caused by immune destruction of insulin-producing cells in the pancreas . Insulin therapy is the preferred method of treatment .
Female dogs can become transiently diabetic during oestrus . However , insulin resistance can be seen in entire bitches and in patients with hyperadrenocorticism ( Cushing ' s disease ) and pancreatitis [ 1 ] . It is recommended that entire bitches that show signs of DM should be neutered as soon as possible .
Some breeds of dog are predisposed to DM , including the dachshund , Alaskan malamute , labrador retriever , poodle , chow chow , beagle , dobermann , English springer spaniel , miniature schnauzer and West Highland white terrier [ 2 ] .
In cats , DM is often the result of insulin resistance ( i . e . type 2 ) due to obesity , meaning that cats produce insulin but their cells do not respond appropriately . A cat may be diabetic only temporarily and can go into remission when it loses weight . Insulin resistance can occur in cats with acromegaly , which is caused by excess secretion of growth hormone . Some of these cats may present with an enlarged chin , paws and skull [ 3 ] . Burmese , Siamese and British shorthair cats are predisposed to type 2 DM [ 4 ] .
Clinical signs
Polyuria – more frequent urination and / or excessive urine volume – the result of excessive thirst / drinking and high glucose levels in the urine .
Polydipsia – excessive thirst and drinking – the result of high levels of glucose in the urine .
Polyphagia – excessive , insatiable hunger – the result of unstable blood glucose and the inability of glucose to enter the cells normally to support the metabolism .
Weight loss – the result of fats and proteins replacing glucose as the main source of energy [ 5 ] .
Causes
There are a number of causes of DM ( Table 1 ) [ 6 ] , although it is usually related to the destruction of islet cells in the pancreas . It is important to consider this when animals present to the veterinary practice .
Table 1 . Aetiology and pathogenesis of diabetes mellitus [ 6 ] .
Severe pancreatitis in dogs or chronic relapsing pancreatitis can cause destruction of islet cells
Amyloidosis in cats , where amyloid is deposited in the islets of Langerhans , with degenerative changes in the beta cells leading to insulin resistance
Chronic administration of corticosteroids or progesterone may increase the clinical signs of DM
Spontaneous hyperadrenocorticism in dogs Hyperthyroidism in cats Pregnancy and dioestrus in dogs Obesity
Complications
Complications can occur if DM is not properly controlled [ 6 ] . These include :
• Lower resistance to bacterial and fungal infections
• Retinal bleeds , if blood glucose is uncontrolled for a prolonged period
• The kidneys may be affected , causing renal damage
• The arteries may be affected and blood samples may be lipaemic
• Neuropathy and weakness in the limbs
• Development of cataracts in dogs , because glucose breakdown products bind to the proteins of the eye lens , leading to blindness . This is rare in cats
• Hindlimb weakness in cats , due to peripheral neuropathy when glucose breakdown products bind to the nerves . Affected cats present with a plantigrade stance , where the hock touches the ground when the cat stands or walks
• Diabetic ketoacidosis ( DKA ) due to the accumulation of ketone bodies ( see p . 48 – 51 ).
DM patients undergoing a general anaesthetic or sedation should have their blood glucose checked on the morning of surgery , and insulin should be given as directed by the veterinary surgeon ( VS ). Blood glucose levels should be monitored during the procedure and dextrose administered intravenously if required .
Diagnosis
Diagnosis of DM is made on the basis of clinical signs and diagnostic testing . A blood sample will be taken to check the glucose level . The normal range of blood glucose for dogs should be between 4.11 and 7.9 mmol / l , and for cats it should be between 4.11 and 8.83 mmol / l [ 1 ] .
Volume 38 ( 5 ) • October 2023
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