Time gets the better of even the healthiest dogs. From cancer and deteriorating thought processes to arthritis and diabetes, geriatric dogs develop diseases similar to those that befall humans. Below is a brief summary of the physical conditions you and your veterinarian may encounter as you help your dog navigate old age.

Note: Older dogs should see a vet every 6 months. Between visits, report any changes in your dog’s health or appearance.

The Senses

With age, your dog’s nervous system will dull. The pathways that transmit messages to the brain from nerve endings slow down, and his senses, which receive messages from the outside world, won’t be as receptive as they once were.

Hearing. Hearing loss occurs naturally in elderly dogs, as nerve cells and hearing apparatus degenerate. Inner-ear problems are also common and may cause dizziness or loss of balance. In some breeds, matted hair growing inside the ear can muffle sounds, as can wax build-up in dogs with narrow ear canals. Drop-eared breeds are prone to infections from yeast, fungus and bacteria.

Sight. Although your dog’s eyes may look cloudy, this condition – called “nuclear sclerosis” – won’t necessarily affect his vision. However, he may lose his ability to focus on nearby objects. Other age-related eye problems include reduced ability to see in the dark (or even in bright light), cataracts, glaucoma and degeneration of the retina.

Smell. The dog’s nose is a highly developed sensory organ, and a large area of the canine brain is devoted to the sense of smell. Tumors and polyps in the nose can weaken the sense of smell, which degenerates considerably in dogs over 15.

Canine Cognitive Dysfunction. At times, degeneration of the nervous system is extreme enough to affect a dog’s quality of life and the way the animal relates to his family. Canine cognitive dysfunction – a syndrome akin to Alzheimer’s disease in humans – can manifest itself in many ways. These include decreased interaction with family; disorientation, confusion and staring into space; abnormal sleep and activity patterns, such as pacing; decreased attention; reduced ability to navigate stairs; apparent hearing impairment; or lapses in housetraining.

Other Systemic Problems

Respiration. Lung capacity decreases with age, and allergies may become more pronounced. Dogs not only use their lungs to draw in oxygen and breathe out carbon dioxide, they also use their lungs and panting for evaporative cooling. Pugs and other short-nosed dogs of all ages are particularly prone to respiratory distress in hot and polluted environments.

Heart and circulation. Dogs do develop heart disease, but heart attacks are rare. Heart murmurs, indicating progressive heart valve disease, can occur in some elderly dogs.

Skeleton, joints and muscles. Arthritis affects one out of every five dogs, caused by wear and tear on the cartilage that connects bones and joints. Selective breeding has altered the bone structure in some dogs, and they tend toward bone disease. What’s more, the vertebrae – the bones that protect the spinal cord – can deteriorate and impinge on its sheath of nerves, causing complications that range from pain and limping to paralysis. Short-legged, long-backed breeds, such as dachshunds and basset hounds, frequently experience slipped discs.

Digestive system. Digestive problems – from stomachs that don’t tolerate certain foods, to intestines that fail to absorb nutrients – are common in elderly dogs. Signs of problems include diarrhea, vomiting and gas. Constipation is another common gastrointestinal malady. Anal sacs also become more susceptible to blockage or infection. Obesity must be controlled with a high-fiber low-calorie senior diet. Overweight dogs are also likely candidates for diabetes.

Kidneys and bladder. The kidneys are one of the first organ systems to wear out in dogs. As the bladder loses elasticity, the animal can become incontinent. Unregulated diabetes can result in frequent urination in middle-aged to older dogs. Straining, pain with urination, increased or decreased urination may signal kidney failure, spinal injury or various infections. If the dog shows any of these signs, take him to the vet promptly.

Hormones and glands. The endocrine system’s glands produce hormones that regulate and coordinate metabolism, immune response and other vital functions. If aging throws hormone production out of balance, multiple body systems are affected, and conditions such as lethargy, weak muscles, arthritis, dry skin, hypertension and heart problems can result. Diabetes occurs when the pancreas fails to produce enough of the hormone insulin or when insulin receptors do not work. In this case, the pancreas still secretes insulin, but it is not effective.

Reproductive system. Between 60 and 80 percent of unneutered male dogs over age 8 develop enlarged prostate glands. They are also prone to testicular cancer. Older, unspayed dogs are prone to uterine infections, uterine or ovarian cancer and ovarian cysts. Older females that become pregnant have significant health problems associated with pregnancy. Female dogs have one-seventh the risk of developing breast cancer if they are spayed before reaching sexual maturity.

Cancer. Cancer is a rampant, abnormal growth of cells. It may first become apparent as a tissue mass called a tumor. Older dogs are more likely to develop cancer, which is often treatable. If it cannot be cured, modern veterinary care, proper nutrition and love can make your pet more comfortable.