Internal Medicine: Medical Conditions

Immune-mediated Disorders: 

In these conditions, the body attacks its own tissues. These diseases can affect the entire body, but main systems involved are:

Diseases of the Blood System:

In these disorders, the dog or cat abnormally produces antibodies causing rapid destruction of red blood cells and/or platelets (platelets are needed for normal ability to clot blood). In immune mediated hemolytic anemia or IMHA, the antibodies attaching to red blood cells lead to anemia that is often severe and life-endangering. In immune mediated thrombocytopenia or ITP, antibodies attach to platelets causing their loss which impairs normal clotting ability. Thus, patients with ITP often present for abnormal bleeding or bruising (e.g., bleeding from the nose, gums, or under the skin). Bleeding can be so severe that the patient becomes pale, weak, and anemic. Diagnosis of IMHA or ITP is accomplished using blood tests. It is important to survey general health as finding an underlying cause of IMHA or ITP helps guide appropriate treatment (e.g. possible initiating conditions include: infections, cancer, and drug or vaccine reactions).

Treatment may include blood transfusions, medications aimed at controlling adverse immune responses, and management of any underlying conditions. Prognosis for both conditions can be good depending on patient response to medications and underlying causal disorder.


In this condition, known as polyarthritis, dogs present with lameness in many different joints but typically the wrist, hock, knee and elbow. Diagnosis is often made by evaluating radiographs of the joints to rule out other conditions, retrieving joint fluid for analysis and culture, and performing blood tests for other diseases that can present in a similar way. Treatment is immunosuppressive medications. Prognosis is excellent.

Liver Disorders:

There are numerous types of liver disease commonly seen in dogs and cats. Several of the more common syndromes are profiled below.

Portosystemic Vascular Anomalies (PSVA, or “portosystemic shunts”) and Microvascular Dysplasia (MVD).

These related congenital genetic disorders are most common in small dog breeds. PSVA are also observed in large breed dogs and less commonly in cats. PSVA differs from MVD in the following way: the PSVA malformation involves one or rarely two large vessels that shunt blood around the liver directly to the heart, whereas the MVD malformation involves microscopic blood vessels within the liver. Both PSVA and MVD are recognized by testing bile acid concentrations in a blood sample. Dogs may be referred for definitive differentiation of PSVA from MVD. Patients with PSVA are often small (runt of litter) with poor growth, and often show neurologic signs (staggering, walking the wall, staring, trembling, seizures), drink excessive amounts of water, and might show signs of urinary irritation (blood in urine, straining) or develop a urinary blockage with stones unique to PSVA (ammonium urate stones). Diagnosis of PSVA is first suspected based on history and routine laboratory assessments or finding unique ammonium biurate crystals in urine. Definitive confirmation of a PSVA may be achieved by ultrasonography or isotope testing (colorectal scintigraphy) or a spiral CT scan. The latter imaging modality is used to definitively identify the anatomy of a PSVA for surgical planning and is more exact than ultrasonography or isotope methods. PSVA may be surgically attenuated, however, some patients respond well to medical intervention (diet and medications). Prognosis can be excellent but specific treatments must be tailored to the patient. MVD is often differentiated from PSVA based on blood tests and if necessary, an isotope study that rules out large grade shunting. Neither tissue biopsy nor serum bile acid tests can differentiate PSVA from MVD. We use a Protein C test to help differentiate PSVA from MVD (PSVA often have values < 70% whereas MVD values are > 70%).

Disorders of Hepatobiliary Structures:


This condition is characterized by inflammation of bile ducts and adjacent liver, and is the most common form of chronic liver disease in the cat. Typical signs include jaundice, inappetence, vomiting, diarrhea, weight loss, or simply, persistently increased liver enzyme activity. This disorder is initially suspected based on blood tests and ultrasound imaging but definitive diagnosis requires examination of a liver biopsy (see liver biopsy below). Treatment is usually medical, although in some cases the gall bladder is removed surgically. Prognosis is usually very good.

Gallbladder Mucocele (GBM): 

A disorder observed in dogs in which the GB fills with consolidated bile and mucus leading to GB rupture. Recent work suggests that a metabolic genetic disorder increases risk for GBM in some dogs (e.g. Shetland Sheepdogs). Clinical signs may be vague in the early stage of GBM development: inappetence or evidence of distress after eating. With chronicity, the patient may become jaundiced. Severe distention of the GB may lead to GB rupture necessitating emergency surgery. Diagnosis of GBM is made through routine chemistry tests and abdominal ultrasonographic imaging. Early diagnosis is aided by examining the GB for normal contractility by sequential ultrasound examinations. Prophylactic GB removal is recommended for some dogs with a developing GBM non-responsive to medical management. The success of medical management is not well established.

Hepatic Mass Lesions: 

Mass lesions within the liver are often identified on ultrasound examination and can represent an area of liver healing (or regenerative nodule in a damaged region), a change in tissue content caused by storage of glycogen (starch, common in dogs with Cushing’s Disease described below), infections (abscesses), biliary cysts, chronic fibrous tissue secondary to chronic hepatitis, or benign or malignant tumors. Routine blood tests and fine needle aspiration samples of the mass lesion under ultrasound guidance are needed to determine whether a mass lesion requires surgical intervention (removal).

Chronic Hepatitis: 

Chronic hepatitis is a common disorder in the dog causing increased liver enzyme activity over weeks to months and only vague clinical signs in the early stages. This syndrome represents ongoing inflammatory liver injury and is often immune-mediated. It may initially start as a primary disease process or secondary to another disease syndrome or exposures to toxins, drugs, or infections. Chronic hepatitis is initially considered as a differential diagnosis based on history, physical assessment, and routine laboratory tests and usually requires ultrasonographic imaging and diagnostic biopsy for definitive diagnosis. In some cases, a simple fine needle aspiration sample is collected to rule out easily diagnosed conditions (neoplasia, vacuolar hepatopathy). An important subcategory of chronic canine hepatitis is that caused by pathologic copper retention (Copper Associated Hepatopathy). This important syndrome can be entirely eliminated with medical and nutritional intervention. The prognosis for dogs with chronic hepatitis and copper associated hepatopathy is variable depending on the stage at time of diagnosis and the underlying cause. In most cases, chronic treatment and periodic health assessments are needed.

Feline Hepatic Lipidosis (FHL): 

The most common acute liver disorder causing severe jaundice in the cat that is potentially lethal without judicious supportive care. FHL is a syndrome initiated by several days of inappetence. Thus, many primary disease processes initiate FHL and must be concurrently managed during FHL diagnosis and treatment. After vitamin K treatment to reduce risk of bleeding, placement of an esophageal feeding tube is needed to allow owner feeding and treatments that support feline metabolic needs during FHL recovery. We have come a long way in managing this common feline syndrome over the last 20 years and now most affected cats can recover. Early diagnosis improves chance of recovery and involves routine laboratory tests, ultrasonographic abdominal imaging, and fine needle aspiration of the liver.

Liver Biopsy: 

Diagnosis of many liver disorders requires blood tests, abdominal ultrasound imaging, and liver biopsy. Liver biopsy is usually necessary to establish a definitive diagnosis and can be completed at the time of an exploratory abdominal surgery or by minimally invasive methods (tru cut needle biopsy, laparoscopic surgery). The best non-invasive method of liver sampling is by laparoscopic “key-hole” surgery as this offers the ability to examine the entire organ grossly, to sample selective lesions, and obtain adequately sized tissue samples.

Endocrine diseases. 

The endocrine system is the collective system of organs that control hormones in the body. There are many types of endocrine diseases, but three we see commonly include:

Cushing’s syndrome in dogs: 

Cushing’s syndrome is a commonly diagnosed endocrine condition of the dog resulting in high blood cortisol levels from the adrenal glands. The disorder usually develops from adrenal gland enlargement stimulated by signaling from the pituitary gland, but also may be caused by an adrenal gland tumor. Common symptoms include increased thirst, excessive urination, ravenous appetite, and thinning hair coat. The condition is diagnosed through blood and urine tests and imaging scans in dogs with appropriate clinical signs. Treatments include medications to reduce cortisol levels, or in some instances surgery. Prognosis is variable depending on the underlying cause.

Diabetes mellitus: 

In this condition, your dog or cat does not have enough insulin to control blood sugar levels and maintain normal body function. As a result, blood sugar levels rise leading to clinical signs of increased urination, excessive thirst, and weight loss. Diabetes mellitus is routinely diagnosed by blood and urine tests. Successful treatment involves daily insulin injections and dietary modification.

Hyperthyroidism in cats

Excessive production of thyroid hormone by an overly active thyroid gland can lead to weight loss, behavioral changes, vomiting, and diarrhea. Diagnosis is based on appropriate clinical signs and physical examination findings in conjunction with routine blood and urine tests and thyroid hormone measurement. This common condition in older cats may be treated by anti-thyroid drugs, radioactive iodine therapy, surgery, or dietary management. Prognosis is generally good to excellent.

Gastrointestinal diseases

Inflammatory bowel disease or IBD: 

Dogs often present with diarrhea, weight loss and sometimes vomiting. In cats, loss of appetite, vomiting, weight loss and diarrhea are common signs associated with IBD. Diagnosis is informed by a thorough history and physical examination, blood tests, fecal analysis, and diagnostic imaging. Taking a biopsy of the intestine either by endoscopy or surgery is required for definitive diagnosis. Treatment depends on the type and severity of IBD and frequently involves diet changes, vitamin supplementation, antimicrobial or immunosuppressive therapy. Prognosis varies according to type and severity of IBD, with good responses observed in the majority of dogs and cats with lymphocytic plasmacytic IBD. Cats with IBD frequently have concurrent diseases of the liver (cholangitis, lipidosis) and or pancreas (pancreatitis) that need to be addressed for optimal response to treatment.
Small Intestinal lymphoma in cats: Small intestinal lymphoma is an important gastrointestinal disease in cats, with clinical signs similar to those of cats with IBD. Intestinal biopsy is required to reliably distinguish small intestinal lymphoma from IBD. Treatment typically includes vitamin supplementation, prednisolone and chlorambucil. Prognosis is good for cats with small cell lymphoma.

Infectious diseases

We see and treat a wide range of infectious diseases. The two most common are:

Lyme disease in dogs: 

Unlike in human, dogs with Lyme disease rarely show clinical signs. The most common sign is lameness due to inflammation of several joints. Some dogs develop kidney disease. Diagnosis is based on history, physical examination, diagnostic imaging (radiograph) and blood and urine tests. Joint fluid may be sampled in some cases. Treatment is by using appropriate antibiotics. Prognosis is usually excellent for dogs with Lyme associated lameness, although dogs rarely clear the infection completely. Kidney involvement carries a much poorer prognosis.

Leptospirosis in dogs: 

A very serious condition that can result in kidney and liver failure. Diagnosis is informed by a thorough history and physical examination, blood and urine tests, and diagnostic imaging. Often dogs need to be hospitalized for an extended stay to treat kidney disease with intravenous fluids and antibiotics. Prognosis is good as long as the kidney function recovers.