Did you know that the diabetes treatment for a cat is different from that of a dog? Or that anal sac issues are a common topic for dog owners, but rarely for cat owners? While these differences might seem like interesting trivia, they have serious implications for your pet’s health, nutrition, and overall care.
The truth is, cats and dogs are not the same. From the hormones that control their bodies to how their organs react to illness and medicine, these furry family members are as different on the inside as they are on the outside. In this blog, our vets at Savannah Veterinary Internal Medicine discuss the top differences in feline and canine internal medicine that every pet owner should know.
Endocrinology (Hormone)
- Thyroid Diseases: In dogs, the most common thyroid disorder is hypothyroidism (underactive thyroid). In contrast, cats typically develop the opposite disease, hyperthyroidism (overactive thyroid). Dogs have too little hormone and cats have too much.
- Adrenal Gland (Cortisol) Disorders: Cortisol-related hormonal diseases, such as hyperadrenocorticism (Cushing’s disease) and hypoadrenocorticism (Addison’s disease), are far more common in dogs and occur rarely in cats.
- Adrenal Gland (Aldosterone) Disorders: Hyperaldosteronism is a condition caused by the excessive secretion of aldosterone leading to high blood pressure and low potassium. While it’s a recognized disorder in both dogs and cats, it is far more common in cats.
- Diabetes mellitus: Dogs generally develop Type 1 diabetes due to a lack of insulin, while cats are more prone to Type 2 diabetes, often linked to obesity, insulin resistance and diet. Unlike in dogs, remission is sometimes possible for cats with early treatment and diet changes. A notable difference is that cataracts are a near certainty for diabetic dogs but are rare in cats.
- Parathyroid Gland Disease: The parathyroids are four small hormone-producing glands in the neck and are responsible for regulating the calcium level. Dogs develop hypoparathyroidism which results in low calcium. This is a very uncommon disease in cats, and in fact, cats tend to have too much calcium from a unique feline condition called idiopathic hypercalcemia (idiopathic, meaning cause unknown).
- Pancreatitis: This inflammatory condition of the pancreas is common in both species, but the causes and symptoms In dogs it is often triggered by eating unaccustomed or fatty foods. In cats, it is frequently idiopathic (unknown cause) and cats often have vague symptoms such as lethargy and anorexia, rather than the classic vomiting and abdominal pain seen in dogs.
Digestive Tract
- IBD versus Lymphoma: Cats are more prone to a specific type of intestinal cancer called small cell lymphoma, while dogs are not. Both species can get inflammatory bowel disease (IBD). Telling the difference between IBD and small cell lymphoma in cats is often tricky because the symptoms, ultrasound findings, and even biopsies can look almost identical. This isn’t usually an issue with dogs, as their low risk for small cell lymphoma makes an IBD diagnosis much more straightforward.
- Esophagus Disorders: Megaesophagus, a condition where the esophagus loses muscle tone and dilates, is a well-known disorder in dogs but is rarely seen in cats.
- Anal sac diseases: Anal sac disease is a common problem in dogs, with up to 15% of dogs experiencing impaction, infection, or cancer during their lifetime. In contrast, these diseases are uncommon in cats, affecting fewer than 0.5% of the feline population. Did you know that allergies can cause anal sac issues, and that allergies love the hot, humid, buggy environment of Savannah and Coastal Georgia?
Liver & Gallbladder
- Hepatic Lipidosis: Is a severe, life-threatening condition in cats that is rarely seen in dogs. It occurs when a cat stops eating, leading to the mobilization of fat stores to the liver. The feline liver is inefficient at processing this fat, resulting in fatty infiltration and liver failure. This makes anorexia in a cat a medical emergency, whereas a dog can often tolerate a short period of not eating without the same risk.
- Hepatic Portosystemic Shunts (PSS): These are congenital abnormal blood vessels that bypass the liver, resulting in circulating blood that is not detoxified. While this condition is not common even in dogs (less than 1% of the population), it is significantly rarer in cats (less than 0.03%). In cats, an often tell-tale sign of PSS is copper-colored irises, not frequently seen in dogs. Despite the rarity of PSS in cats, a patient of Savannah Veterinary Internal Medicine diagnosed with PSS is seen in this picture (note the unique iris coloration). What color are your cat’s irises?
- Biliary Mucocele and Gallbladder Sludge: Biliary mucoceles, which are abnormal accumulations of thick mucus in the gallbladder, are a common and serious condition in dogs, especially in certain breeds like Shetland Sheepdogs. The presence of gallbladder “sludge” is also a frequent finding in dogs and often not of significant concern. In cats these conditions are considered rare.
Cardiology
- Heart Disease: In large breed dogs, the most common type of heart muscle disease is Dilated Cardiomyopathy (DCM), where the heart becomes enlarged and its pumping ability weakens. Cats, in contrast, are more prone to Hypertrophic Cardiomyopathy (HCM), a condition where the heart walls thicken, making it difficult for the heart to fill and pump blood effectively. In cats, this can be caused by untreated hyperthyroidism.
Urinary
- Urinary Tract Infection & Inflammation: Dogs are more prone to bacterial urinary tract infections (UTIs). In cats, a common and often frustrating condition is feline idiopathic cystitis (FIC), a non-infectious inflammatory condition of the bladder wall with no identifiable cause. It is often stress-induced, is not a urinary tract infection (UTI) and does not need antibiotics to treat.
- Urinary Tract Cancer: Urinary tract cancer in dogs is encountered all too frequently, with the most common type being transitional cell carcinoma. Fortunately for cats, urinary tract tumors are very rare.
Reproductive
Prostate Disease: Dogs are at a significantly higher risk for prostate disorders than cats. In non-neutered male dogs, hormonal influence can lead to conditions such as benign prostatic hyperplasia (BPH), prostatic cysts, and prostatitis. Prostate cancer, on the other hand, is not hormonally driven and can affect both neutered and intact dogs. Overall, prostate diseases are rare in cats.
- Uterine Disease: Pyometra, a serious uterine infection where the uterus fills with pus, is more common in dogs than cats. The difference is due to dogs experience prolonged periods of the hormones during reproductive cycling, which can prime the uterus for infection. This is less of a risk in cats, which are induced-ovulators and only experience these hormonal changes after mating.
Medications
- Acetaminophen: Cats lack certain liver enzymes that humans and dogs have, which limits their ability to metabolize certain medications. This explains why acetaminophen (Tylenol) is toxic to cats but safe for dogs and humans.
- Permethrin: This is a common insecticide used in some dog flea and tick medications. While safe for dogs, it’s highly toxic to cats, as they lack the necessary enzymes to break down the chemical. Even a small amount of permethrin can be fatal to cats because it attacks their nervous system.
- Prednisone: Due to a cat’s poor ability to convert prednisone into its active form, prednisolone, we always prescribe prednisolone directly. It’s also important to note that cats taking prednisolone have an increased risk of developing diabetes mellitus and congestive heart failure, which are not considerations for dogs.
- Fluoroquinolone Antibiotics: This class of antibiotics, with enrofloxacin being the most notable, can cause acute permanent blindness in cats (retinal degeneration). For dogs, fluoroquinolones are generally considered safe for the eyes and do not cause the same type of retinal toxicity.
- Doxycycline Antibiotic: Doxycycline in its tablet form can cause severe esophageal injury in cats, leading to esophageal stricture. Liquid formulations of doxycycline are generally considered safer for cats and less likely to cause this issue. It is important to note that while this side effect is well-documented in cats, it is far less common in dogs.
Infectious Diseases
- Heartworm Disease: While both dogs and cats can contract heartworms, the disease is much more severe and life-threatening in cats. For dogs there is a safe and effective approved treatment to kill the adult worms. For cats, there is no approved treatment. This makes prevention critical for both dogs AND cats. Did you know that Georgia consistently ranks in the top 10 states of having heartworms, and that the wet, marshy areas of the Lowcountry of South Carolina, Savannah and Coastal Georgia are especially appealing to this parasite and the mosquitoes that transmit them? Which feline heartworm prevention are you giving?
- Leptospirosis: Is a serious bacterial infection that is a significant concern for dogs but is rarely seen in cats, as felines are highly resistant to the disease. Dogs typically contract the infection through contact with contaminated water (such as marshes) or urine from infected wildlife like deer, raccoons, and rats. Because rats are common carriers, even urban areas not known for large wildlife populations—such as historic Savannah—can pose a significant risk. In dogs, the disease primarily affects the kidneys and liver sometimes resulting in failure of one or both of those organs.
- Highly Pathogenic Avian Influenza (HAPI): As of August 2025, due to feline differences in physiology (specifically, cats having the preferred receptors that H5N1 binds to), bird flu has been shown to be more commonly infecting cats than dogs. Furthermore, infections in cats tend to be more severe, frequently resulting in death. Fortunately for cats living in Savannah and Coastal Georgia, there has yet to be a reported feline infection (August 2025).
- Fungal Rhinitis: While both dogs and cats can develop nasal fungal infections, they are typically caused by different organisms. In dogs, Aspergillus is the most common cause. Cats, on the other hand, more frequently are infected with an organism called At Savannah Veterinary Internal Medicine, we diagnose many canine and feline patients with nasal fungal infections with the use of rhinoscopy.
- Pythiosis: Also known as “Swamp Cancer”, Pythium insidiosum is a fungal-like water mold, which thrives in stagnant warm water (e.g., ponds, swamps). Infection typically occurs when a dog swims in, or ingests the water. This organism is most commonly encountered in the Gulf Coast states of the US. Fortunately for cats, they are rarely infected when compared with dogs.
Toxicities
- Easter Lilies: Along with other “true lilies” such as Tiger lilies, Daylilies, and Stargazer lilies, are extremely toxic to cats. Even a few licks of pollen can lead to severe, irreversible, and fatal kidney failure. Dogs, on the other hand, typically experience gastrointestinal upset, such as vomiting or diarrhea. Fortunately, Easter lilies are not native to Coastal Georgia, so Savannah pets who venture outdoors will only encounter them if they are purchased and displayed outdoors.
- Xylitol: The artificial sweetener is extremely toxic to dogs, but not cats. After ingestion by a dog, there is a period of extreme hypoglycemia (low blood glucose), possibly followed by acute liver failure. Cats have not been shown to have these side effects. Be cautious of some of the liquid forms of gabapentin as these may contain xylitol! Unfortunately, xylitol has made its way into a variety of human foods (e.g. peanut butter) that are often given to dogs as a treat or a way to hide pills into.
Conclusion
Understanding and recognizing the unique differences between dogs and cats is crucial for veterinarians and pet owners alike. Being aware of these species-specific distinctions is essential when choosing over-the-counter medications, foods, and household items to ensure the safety and well-being of your furry companions. If your pet is experiencing abnormal symptoms that haven’t responded to treatment or for which a diagnosis is unclear, feel free to contact us, we can help.
Author:
James Woods DVM, MS, DACVIM (SAIM)
Ph: (912) 721-6410
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