Antech News - April 2001

April • 2001

LABORATORY DATA IN GERIATRIC DOGS & CATS

The following summarizes a study of geriatric dogs and cats performed at the VCA West Los Angeles Animal Hospital in 1998 and 1999.

Background

As laboratory tests play an important role in the overall evaluation of animal patients, a clinical study of routine laboratory parameters was conducted in healthy senior dogs and cats. The study purpose was to evaluate laboratory findings from a large number of clinically normal older dogs and cats to evaluate the rationale for, and value of doing laboratory work routinely as part of a senior wellness program. Ninety dogs and 100 cats, all over seven years old, were enrolled in the study.

As an animal ages, there is a definite loss of functional reserve capacity of every organ system (Table). These changes of aging may affect laboratory data without necessarily reflecting the presence of a disease process and must be considered when interpreting laboratory values in senior patients.

Background

Study animals were selected from the overall hospital database over a 5 month period. They were all over seven years of age, in apparent good health according to the owner, and had no underlying medical condition or treatment known to alter laboratory values (e.g., corticosteroids, phenobarbital). Once enrolled, the animal was presented for a thorough historical review, general physical examination and laboratory tests including a CBC, serum chemistry profile, T4, urine cortisol:creatinine ratio (dogs only), and complete urinalysis (cystocentesis samples). Only animals with a normal physical exam were selected.

EFFECTS OF AGING

Metabolic Effects

Decreased metabolic rate and activity reduces caloric need by 30-40%.
Decreased immune competence despite normal lymphocyte numbers.
Decreased phagocytosis and chemotaxis with less resistance to infections.
Autoantibodies and autoimmune disease develop more commonly.
Increased function of most endocrine organs (thyroid, reproductive, pancreas) plus increased activation of hypothalamic-pituitary-adrenal axis.

Physical Effects

Increased % of body weight represented by fat.
Skin becomes hyperpigmented, loses elasticity.
Footpads hyperkeratinize and claws become brittle.
Loss of bone, muscle and cartilage mass with resultant development of osteoarthritis.
Dental calculus results in gingival hyperplasia. Calculus with periodontitis leads to gingival atrophy, gum retraction, and tooth loss.
Gastric mucosa becomes atrophic and fibrotic alongwith decreased production of pancreatic enzymes.
Decreased hepatocyte numbers, with fibrous connective tissue replacement (hepatic fibrosis). Progressive disease may result in cirrhosis.
Lungs lose elasticity and begin to fibrose, secretions become more viscous, vital capacity decreases as does cough reflex and expiratory ability.
Decreased kidney weight, tubular atrophy, and increased glomerular filtration rate. Urinary incontinence may occur.
Prostate and ovaries enlarge, testes atrophy, prepuce becomes pendulous, mammary glands become fibrocystic.
Decreased cardiac output, valvular fibrosis and intramural coronary arteriosclerosis along with arrhythmias and increased peripheral resistance.
Bone marrow becomes pale and fatty and anemia ensues.
Decreased number of nervous system cells, with increasing amounts of beta amyloid.

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