Internal medicine includes thoracic and abdominal organ diseases (e.g. gastrointestinal, liver, kidney, lung and heart diseases), blood diseases (e.g. anemia and coagulation disorders), endocrine diseases (such as diabetes mellitus, thyroid-, adrenal- or pancreatic insufficiency, cats hyperthyroidism). Also some cancers, such as lymphoma, are treated in the internal medicine department. Examination of an internal medicine patient can be very challenging and it can take several hours. In these cases the patient is taken into the hospital for the day.

Precise medical history is extremely important (how and when the symptoms have started, how they have progressed and what treatments have already been tried). In the clinical examination of the patient, the vet is searching for answers to how the patient is behaving and where it is painful.

Very often when diagnosing the disease, various research methods are used. Basic blood sample is checked almost from every internal medicine patient. Blood samples are examined right away in the clinic and results are obtained within thirty minutes to an hour. In some cases, for example hormonal tests or examinations for infectious diseases, samples are sent to an external laboratory. Before taking a blood sample, the animal should be starved for at least 10 hours. If the animal is on continuous medications, the treating veterinarian should be consulted for the best time to do the blood sample.

Urine samples are mainly taken in the clinic directly from the bladder through the abdominal wall. This provides a sterile sample and reliable results. Usually a quick screening (stix), specific gravity, sediment, bacteriologic culture and sensitivity measurements are performed from the urine sample. If a renal disease is suspected, a proteine-creatinine ratio test can be performed from the urine.

Stool samples are mainly examined in case of endoparasites. Other examinations are rare. Stool samples, for endoparasite examination, would be good to collected for three consecutive days.

Radiographs are a very common examination method that gives a good picture of the abdominal and thoracic organs, their size, shape and location. For example, when lung diseases, foreign body or urolithiasis is suspected, radiographs are often necessary. In some cases, mostly in examination of gastrointestinal tract or the kidney and urinary tract diseases, contrast enhancement is used. Contrast agent is administered either orally or intravenously.

Ultrasound scan allows examination of the organs more accurate, we are able to see their shape, size and structure also beneath the surface. With the help of ultrasound, we are able to visualize organs that are not seen in x-rays, such as adrenal glands, pancreas and abdominal lymph nodes. During ultrasound, samples can be taken from a changed or suspicious area. Ultrasound also gives a picture if there are fluids in the abdomen or thorax and it is often used in examination of a trauma patient.

After the localization of the cause, in chronic and serious diseases, biopsy is taken in order to get a clear diagnosis. Biopsies are sent to a pathologist for examination, after which we know the prognosis for the disease and we can choose the best treating method. Biopsies can be taken laparoscopically.