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When Symptoms and Diseases Overlap

This interactive diagram shows you at a glance what are the symptoms caused by the main chronic diseases in dogs and cats.

You can wander back and forth, from diseases to symptoms and reverse to get a quick idea of what situation your pet may be in.

You'll also understand why it is never possible to diagnose a disease on the sole basis of the symptoms and why complementary exams are always necessary: physical examination, lab tests, X-rays, echography etc...

Warning: not all diseases and symptoms are listed here. This interactive diagram does not replace a veterinary consultation.

Vomiting PU - PD Diarrhea Weight loss Change in appetite Lethargy Dehydration Discharge Coughing Seizures or fainting Bad breath Fever Abdominal swelling Intolerance to exercise Diabetes Kidney Dis. Allergy Infections Cancer Liver Dis. Heart Dis. Pancreatitis Arthritis Symptoms(consequences) Diseases(the cause)

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Hover over a disease or symptom

Symptom: vomiting

Vomiting is an involuntary expulsion of stomach content through the mouth. The process of vomiting involves the contraction of the powerful muscles of the stomach, the diaphragm and other respiratory muscles.

The most obvious reason for vomiting is a digestive disorder often caused by an infection. It may also come from the need to get rid of foreign objects, or toxic substances; or caused by an intolerance or an allergy to certain types of food. Puppies or kittens may vomit some long and white round worms (Toxocara or Toxascaris).

The most important concern is when vomiting is one of the symptoms of a serious underlying chronic disease: diabetes, kidney disease, liver disease, pancreatitis, cancer, or inflammatory bowel disease. Vomiting may also be caused by neurologic disorders.

Whatever the cause, vomiting induces dehydration.

More information on vomiting in dogs or in cats.

Symptom: Polyuria - polydipsia (PUPD)

Polyuria consists of urinating too much, or more than usual. Polydipsia consists of drinking too much, or more than usual. Polyuria and polydipsia always come together. But, depending on the disease, only one of them entrenches this cycle.

This disorder is difficult to notice. You'd have to pay attention to subtle signs. For instance, you may need to refill the water bowl more often. Your dog may insist on going out for a walk, even at night or the litter of your cat may need to be changed more frequently. Owners may not notice it, especially in the case the cat is allowed to wander outside or if the dog has free access to a yard.

At the clinic, the vet will perform precise measurements of urine output and water intake to confirm the symptom.

The causes of PUPD are very diverse and need to be taken seriously. Polyuria-polydipsia can be one of the symptoms of many diseases:
diabetes, liver disease, hyperadrenocorticism, hypercalcemia, hyperthyroidism, hypokaliema, kidney diseases...

More information on polyuria-polydipsia in dogs and in cats.

Symptom: diarrhea

Diarrhea is made of loose or liquid stool. Diarrhea is composed by 60% to 90% of water. It is the result of faster bowel movements and/or disturbed water exchanges between the body and the intestines.

Osmotic diarrhea occurs when high-osmolarity food attracts water from the body to the intestines. For instance, this is the case for food containing a large proportion of salt or fructose (ex: syrup, fruit juice...).

Diarrhea also happens when the intestine secretes more minerals (electrolytes) than it can absorb as in infections, or in some forms of cancer.

A rapid intestinal transit may bring about a diarrhea. Food can't be digested normally because it moves too quickly in the intestine. This happens in hyperthyroidism, in case of inflammation of the digestive tract caused by intestinal bowel disease or food allergy.

Pancreatitis or liver disease lead to the malabsorption syndrome and secretion of water in the intestine.

More information on diarrhea in dogs and in cats.

Symptom: weight loss

Weight loss is present in a wide range of diseases. In diabetes, weight loss comes from the use of muscle proteins as a source of energy to replace glucose.

In many other diseases, it is the consequence of digestive disorders (vomiting, diarrhea) caused by kidney disease, liver disease, or pancreatitis.

Weight loss in heart failure may be the consequence of the loss of muscles due to the lack of physical exercise. In the later stages of the disease, it is considered as a complication. The animal loses its appetite and its ability to store fat. It may not react well to diet changes, too.

In cancer, nausea and metabolic changes often induce a decrease in appetite. Cancer treatments may affect the digestive tract and thus cause a loss of appetite. Finally, cancers located along the digestive tract can make eating difficult or painful.

More information on diarrhea in dogs and in cats.

Symptom: change in appetite

Change in appetite concerns nearly all serious chronic diseases, since it is an effect of a change in the general condition of the animal.

It can be the consequence of (examples: vomiting, diarrhea) or a cause (example: weight loss) for other symptoms.

In most cases, change in appetite means the animal has lost interest in food. But there is a noticeable exception with diabetes that causes polyphagia, a persistent hunger.

More information on change of appetite in dogs and loss of appetite in cats.

Symptom: lethargy

Lethargy, or weakness, is a common condition. The symptom is vague and doesn't necessarily mean that there is a serious underlying disease. As for humans, it may be natural, part of the usual life's ups and downs. The owner should start worrying and consult her veterinary surgeon when this condition lasts for more than a couple of days or when it is associated with other symptoms.

Lethargy is easier to notice in very active dogs. It can also be spotted by cat owners: the cat is less playful, does not ask to leave the house, or sleep even more than usual.

As for loss in appetite, lethargy is involved in a lot of diseases, especially in the latest stages: infections, diabetes, kidney disease, heart disease, cancer, liver disease, pancreatitis, and so on...

More information on lethargy in dogs and in cats.

Symptom: dehydration

The balance of water and electrolytes is tightly regulated by the kidneys and the hormonal system related to them. Dehydration may occur though, when the body can't recover the quantity of water it needs to compensate the losses. There are really only two ways to get water: by drinking or eating. It is a voluntary active process. On the opposite there are many ways to lose water, which animals do not control: urination, sweat, breathing, or fecal excretion.

When too much water has been lost, a coma occurs that can be followed by death!

Dehydration is also a symptom of some serious conditions: kidney disease, of course, but also infections, and pancreatitis. The main reasons for dehydration include vomiting and diarrhea. Both induce the loss of a large amount of water.

Owners may notice an unusual fatigue, sunken eyes or darker urine. But probably, the easier way to assess dehydration is to test skin elasticity. In dehydrated animals, the skin retracts much slower to normal after it was pinched (usually between the shoulders).

More information about dehydration in dogs and in cats.

Symptom: discharge

The mucous membranes and the skin are the frontier between the body and the outside environment. Mucous membranes are located inside the body. They cover the respiratory and digestive tracts, the mouth, the nose and the eyes. Unlike the skin, mucosal surfaces allow exchange of fluid, nutrients or gas. However, mucous membranes are more fragile. They are covered with mucus they produce themselves, and which helps them prevent microbes from entering the body.

In case of infections, the mucous membranes produce additional mucus to wash out the infective bacteria or viruses. This production can be very abundant: this is where discharges come from. Learn more about the epithelia in this chapter of the Vaccination Guide about the immune system.

Likewise, a allergy provokes nasal, oral or eye discharge. Allergens trigger an inflammatory response that also leads to the production of a large quantity of mucus. This is what happens in the well-known hay fever, for instance.

Bloody discharge may occur in cancer when the tumor is located close to the face.

More information about cat eye discharge and dog nose discharge.

Symptom: coughing

Coughing is a three-phase process. It starts with a large inspiration. Then, the glottis closes the airways and the respiratory muscles contract. Finally, the glottis opens and the air is vigorously expelled. It can be a voluntary action or a reflex.

The primary reason for coughing is to get rid of substances that obstruct the lungs and the airways: dust, food that has taken the wrong route, or abundant and/or infected mucus. It can also be the consequence of some irritation in some places in the respiratory tract.

In dogs, the kennel cough is a recognizable cough that signals an infection with respiratory bacteria and viruses. It sounds like a goose honk.

Allergy is an exacerbated inflammatory response to a specific substance, an allergen. The body tries to get rid of it by coughing when it detects the allergen's presence in the airways.

Cancer within the respiratory tract may also induce coughing. Irritation and bleeding cause the animal to cough.

More information on coughing in dogs and in cats.

Symptom: seizure or fainting

Seizure is neurological disorder in the brain that causes convulsions and collapsing. Epilepsy is a repetition of seizures. But it is not the only cause.

Diabetes is an impairment of blood glucose regulation. Seizures occur when the concentration of glucose is far too low, depriving the brain of its source of energy. It may happen in case of too much exercise, too much insulin or when the cat or the dog hasn't eaten enough.

Seizure is also a symptom of advanced liver disease. The liver can't clean up the blood and remove its toxins as it used to. The most sensitive organ is the brain, which develops a condition called Hepatic Encephalopathy.

Fainting (or syncope) is not a seizure. It does not have a neurological origin. It comes from a temporary drop of blood flow in the brain. In heart failure the heart may lose sometimes its ability to pump enough blood into the circulation and therefore lead the dog to collapse (much rarer in cats).

More information about seizure in dogs or in cats. And about fainting in dogs.

Symptom: bad breath

In dogs, the most common reason for bad breath is not a disease, although it may become one (periodontal disease). It is a lack of hygiene. Either they don't get their teeth cleaned (by the vet, the owner or with dental chews) or they have very poor feeding habits such as eating poop or dead animals.

Pets with diabetes can't use all the glucose they need. Instead, they metabolize fat as an alternative source of energy. Ketones are a by-product of fat digestion. They have a sweet and fruity odor. Periodontal disease is also a consequence of diabetes. High glucose concentrations help bacteria develop within the gum.

An ammonia smell from your pet's mouth may be a sign of kidney disease. This odor is characteristic of nitrogenous waste from protein metabolism. Failing kidneys can't remove it properly from the blood.

Oral cancer generates a strong odor of dead tissues, coming from the tumor itself.

Hepatic fetor is one of the signs of late stage liver disease. Liver malfunction leads to the production of sulfur molecules that are released in the blood stream and gives the breath a distinct smell.

More information on bad breath in dogs and in cats.

Symptom: fever

Normal body temperature in dogs and cats ranges from 101 to 102.5 degrees Fahrenheit (38.3 to 39.2 degrees Celsius), which is a bit more than in humans. Fever is an elevation of body temperature most often due to an illness. It can hardly be considered as a warning symptom because it's almost impossible the owner can notice it. In practice, the vet takes the temperature because she/he or the owner has spotted other concomitant signs: dehydration, lethargy, vomiting, discharge etc...

Fever is a positive reaction of the body against infections. It is now acknowledged that increased body temperature helps the immune system fight pathogens. It enhances inflammatory reaction and effector T-cells activity.

In pancreatitis the pancreatic enzymes are activated too early and attack the pancreas itself. They activate the complement system (part of the immune system), and trigger an inflammation that causes fever.

More information on fever in dogs and in cats.

Symptom: abdominal swelling

We are talking here about ascites: the accumulation of fluid in the abdomen.

Right-sided heart failure slows down blood flow from the organs to the heart. Fluids accumulate upstream in the abdomen.

Cell necrosis and fibrosis are very frequent in a diseased liver. They prevent blood from circulating normally in the liver: part of the blood flows back causing portal hypertension and ascites.

Cancers affecting the liver, the peritoneum or the lymphatic system cause ascites.

Not all abdomen enlargements are caused by ascites. There are many other origins and some of them are obvious: weight gain, pregnancy, internal parasites in puppies/kittens, gas build-up in the intestinal tract...

More information about abdominal enlargment in dogs and in cats.

Symptom: intolerance to exercise

Exercise intolerance is not an unwillingness to move caused by laziness, fatigue or sickness. It's when a pet, willing to move, can't do it the same way it used to. This is not always easy to notice and may be interpreted as an effect of aging. It takes the form of an intolerance to hot and humid days, a short breath, a walk that doesn't last as long as before.

This is a key sign of decompensated heart failure. The heart, acting as a pump that pushes blood in the arteries and veins, is not as efficient as it was. It doesn't get as much oxygen from the lungs, and fails to bring to organs and muscles the oxygen and nutrients they need. The animal loses endurance and lacks energy.

Arthritis is another reason why a pet would be reluctant to move. The inflammation it generates causes discomfort and pain. Lameness is not necessarily present if more than one limb is affected. There is also a certain stiffness that should be apparent to the owner.

More information on intolerance to exercise in dogs.

Disease: diabetes

Diabetes is an abnormal increase in body's glucose concentration. Glucose, the only type of sugar that body cells can use, is not properly regulated any more by an important hormone, the insulin: either the pancreas can't provide enough insulin (type-I diabetes, mostly in dogs), or the body becomes progressively insensitive to insulin (type-II diabetes, mostly in cats).

A diabetic pet tends to react to the increased concentration in blood glucose. The animal drinks more (and urinates more) in order to dilute blood glucose: this is the polyuria-polydipsia symptom (PU-PD). Body cells can't use glucose as well as they used to: the animal lacks energy and feels lethargic. Excessive glucose is eliminated in the urine, thus damaging the kidneys and leading to a chronic kidney disease. As the body is lacking usable glucose, it uses its own proteins, especially from the muscles, as an alternative source of energy. This makes the organism starve for proteins causing weakness, weight loss and increased hunger.

Diabetic seizures come from a lack of glucose within the brain due to either a too aggressive treatment with insulin injections or the pet not eating enough.

Others diabetes symptoms:

vomiting, poor coat quality, cataracts, ketoacidosis.

More information on diabetes in dogs and in cats.

Disease: chronic kidney disease

Chronic kidney disease is a progressive and irreversible loss of nephrons. Nephrons are very small kidneys' sub-units, which filtrate blood to produce urine (there are around 400,000 nephrons in cats and 600,000 in dogs).

After one or several initial injuries (kidney stones, hypertension, urinary tract infection, diabetes, auto-immune disease...), the nephrons are no more numerous enough to perform their task. They tend to be "in overload" and die one after the other.

As the kidney filtration capabilities decrease, waste accumulates in the blood. The body can't accept excessive nutrient intakes. The appetite is reduced and the animal starts vomiting regularly: it gets tired and feels lethargic. It loses weight.

It drinks and urinates more (polyuria/polydipsia) so that waste is diluted in the blood and more easily eliminated.

Other symptoms:

urinary incontinence, oral ulcers, pale appearance, dehydration, bad breath smelling like ammonia.

More information on chronic kidney disease in dogs and in cats.

Disease: allergy

Allergy is an excessive inflammatory reaction of the body's immune system to a foreign substance usually called an allergen. Allergic symptoms range from mild to very severe (anaphylactic shock, potentially life threatening).

The symptoms of an allergic reaction do not depend on the allergen. Thus, they don't help find where the allergy comes from (i.e. what is the allergen), which is often a long and difficult process.

Food allergy often causes vomiting or diarrhea.

Skin allergy symptoms: itchiness, red skin, hive, secondary ear infections, constant licking.

Other symptoms:

eye and nose discharge, swelling of the face (or the ears, lips, eyelids).

More information on allergy in dogs and skin allergy in cats.

Disease: infectious diseases

Infections are caused by a wide variety of viruses, bacteria or parasites. That's to say they are capable of causing very many different symptoms. We can't put a comprehensive list here. Many of them are discussed in our Essential Guide to Pet Vaccination.

The symptoms may be categorized according to the organs the pathogens make the most damage to. All pathogens may generate fever as this is a reaction to help the immune system fight infection. They affect the animal's health condition, which feels tired, lethargic, or loses appetite.

Respiratory pathogens induce coughing, oral, nasal and ocular discharges, expectoration, irregular breathing.

Digestive pathogens cause vomiting, diarrhea, anorexia, or dehydration.

Some other symptoms:

paralysis/paresis, blindness, arthritis, bleeding

More information on infectious diseases in dogs and in cats.

Disease: cancer

Cancer is an abnormal, uncontrolled development of some body cells. They affect nearby cells or disseminate as metastases in the whole body. Cancer can affect any body's organ. It often, but not always (ex: blood cancers), develops in the form of tumors. On the opposite, benign or non-cancerous tumors don't spread to other body's places.

Aging pets are more prone to develop cancer. Many factors increase the risk of cancer. They are the same as for humans: exposition to chemical substances, air pollution, ultra-violet light, or nutrition. Cats seem a bit more at risk because of the FeLV virus or the sarcoma at the vaccine injection site, fortunately very rare and curable.

The animal's general health declines and it displays symptoms of rapid weight loss, change in appetite, lethargy or depression. It may feel pain, most often unnoticed by the owner.

Within the skin, the owner may notice lumps or not-healing wounds. Abnormal discharge from the eyes, mouth, ears, coughing and difficult breathing may be mistakenly interpreted as symptoms of an infection or a respiratory disease.

Other symptoms:

abdominal swelling, abnormal odors.

More information about cancer in dogs and in cats.

Disease: liver disease

The liver is a vital organ that has a huge functional reserve and the ability to regenerate. The liver has many functions: it detoxifies the nutrients just after they've been absorbed by the intestinal tract, stores glycogen (reserve of glucose), produces the bile which helps digest fat and, releases hormones.

Chronic inflammation, many infective agents, poor blood circulation may damage the hepatic functions. The liver may also get intoxicated by the waste it is supposed to treat. Liver disorder affects digestion with vomiting, diarrhea, loss of appetite, resulting in weight loss.

Poor blood circulation in the liver may be the cause of fluid retention in the abdomen. This is the origin of abdominal swelling or ascites.

Toxins that have not been removed from the blood by the liver and metabolic changes may induce many neurologic disorders including behavioral changes, blindness, seizures, coma...

Other symptoms:

excessive urination, jaundice, gastrointestinal bleeding.

More information on liver disease in dogs and in cats.

Disease: heart disease

The heart is the pump that moves the blood in the arteries and veins. It's a double pump actually. The left-sided heart moves the blood from the lungs to the other organs. The right-sided heart does the opposite: from the organs to the lungs.

Heart disease is a frequent disease in dogs. There are two common types of heart disease. Mitral disease is common on small breeds of dogs. It affects the left heart. It is a leakage of the valve that separates the atrium from the ventricle. Dilated cardiomyopathy is common on larger breeds. It is an enlargement of the size of the heart with thinning of the heart wall.

Both diseases make the heart less efficient in bringing blood to the organs. They cause the same symptoms: coughing, difficulty in breathing, intolerance to exercise, lethargy, loss of appetite and weight loss, and in the most advanced stages of the disease, fainting.

Abdominal swelling or ascites is less frequent. It occurs when the right-sided heart's valve is damaged. It causes retention of fluids upstream in the abdomen.

More information on chronic heart failure in dogs and in cats.

Disease: pancreatitis

The pancreas is both an exocrine AND an endocrine gland. It means that it releases hormones in the blood (endocrine role) and digestive enzymes in the intestinal tract (exocrine role). The organ is located just under the stomach. A mammal can't live without a pancreas, this organ is vital.

Pancreatitis is an inflammation of the pancreas. It occurs when the digestive enzymes become active before they leave the pancreas, which should not happen. They start to digest the pancreas itself! Some enzymes may even leak into the blood stream.

The symptoms range from mild to very severe and death. Anorexia, weight loss and vomiting are the most frequent symptoms. They may be accompanied by dehydration, diarrhea, lethargy or fever.

More information on pancreatitis in dogs and in cats.

Disease: arthritis

Arthritis is a progressive degenerative disease of the joints. A continuous inflammation of the joints causes pain and contributes to cartilage damage. The origins are diverse. The most documented one is the hip or elbow dysplasia: the head of the femur or of the humerus does not fit smoothly in the articulation capsule. Body conformation in some breeds may trigger the onset of arthritis.

Arthritis may also be caused by obesity, an injury, too intensive physical activities, or orthopedic surgery. Most often, it is a combination of these factors.

The main symptoms are pain although it is difficult to be noticed by the owner, unwillingness to exercise, lameness, stiffness, loss of appetite, or weight gain.

More information about arthritis in dogs and in cats.