Medical tests

Often it becomes essential to have more information about a patient's condition than a simple physical examination. There are infinite different tests that can be done for different purposes but all these have some basic methods which are used. All these methods are modified according to the need and purpose.

Culture and microscopic examination:

To test infections by bacteria or parasites, the biological sample (e.g., stool sample, urine sample, etc.) needs to be cultured and or examined under the microscope. These tests are done in specialized laboratories. These disease causing organisms can be seen under the microscope once the sample is incubated with special growth medium for 24 or 48 hours. The analysis may require longer time because some of these disease organisms are very slow growing.

Tissue examination:

Sometimes often some cells in the body become abnormal due to the body condition (e.g., blood, skin cells, uterine tissues, etc.). These tissues need to be tested under the microscope for their structural deformity, irregularity, or pure number. This test is done in specialized laboratories and may require some time before they can declare the results.

Imaging:

Imaging is one of the most widely used techniques for visualizing structural defects of the body. X-ray photography from various angles and cross-sections along with the help of computer analysis can create a 3-D image of the body part.

• Normal x-ray are mainly used to look at the changes of the bone structure. Chest x-rays are done to test for the lung diseases and also to see the size of the heart. Some times some dyes or other chemicals are injected into the tissues before x-ray is done. This is to increase the contrast of those organs. For example, to get an x-ray of the upper gastrointestinal tract, barium is given. Similarly for the x-ray of the spine, a dye is injected into the spinal fluid to outline the spinal chord.
• Fuoroscopy is another method wherein we get a moving picture of the body and can be recorded as a video. Such a fluorogram is performed in case of the respiratory system, the gastrointestinal tract, the bladder, etc.
• CT scan (Computed Tomography, 3D images of mainly the head, chest, abdomen, and sometimes of the bones. This test is also called CAT scan).
• Magnetic Resonance Imaging (MRI) is another way to take pictures. In this method, instead of x-rays, magnetism and radiowaves are used and the signals are analyzed by the computer. This method of imaging is more sensitive than x-rays and can differentiate between the different soft tissues of an organ. This test can be used to diagnose disease in any tissue of the body.

Ultrasound:

This technique uses high frequency sound waves and the reflected sound (echo) from organs is detected and analyzed pictographically on a monitor which can then be stored as images.

• Echocardiogram is performed on the heart.
• Sonography is the same thing mainly performed on kidneys, liver and spleen, the brain, the female pelvis, and hips.

Use of radioisotopes as tracers:

Many tests use very small amounts of radioisotopes (radioactive materials) to image parts of the body. Normally the radioisotope is given with a carrier and is inhaled, swallowed, or injected. The positioning of these isotopes in the body is detected by the radiations from these isotopes and an image is produced from that.

• Bone scan: to detect changes in the bone physiology and metabolism.
• Kidney scan (renal): To visualize structure, position, and function of the kidneys.
• Liver and gallbladder scan: Visualizes liver damage, cirrhosis, hepatitis, infection, injury, or even cancer.
• Lung scan: To detect blood clot or structural malformations.
• Thyroid scan: Detects structure, shape, size, or even function of the thyroid.
• Urinary bladder scan: It is to detect the back flow of the urine from bladder to the kidneys.

Measure of electric activity:

The communication and signaling in tissues involve electrical impulses. The recording of these impulses can give a lot of information such as metabolic disturbances, inflammations etc. These impulses are recorded with the help of electrodes which are placed on the body. These electrodes are held using a kind of paste and never needles except in case of electromyography (EMG).

• EEG (electroencephalography) is to test the impulses in the brain. It is often called as brain wave test and thought to test IQ or reads the mind! Nothing of that sort. It tests for seizures, epilepsy, disorders, head injuries, inflammation, tumors, and even sleep disorders.
• EKG (electrocardiography) is performed to test electric activity in the heart. It detects the regularities of the heart beats, and detects injuries.
• EMG (electromyolography) measures the response of the muscle fibers to electrical activity. It detects the reasons behind muscle weakness.

Note:

This is just a brief description and all these tests can be modified according to the need and situation.

Compiled by: Indrajit Sinha; Last updated: 19.11.07© Medhospital Foundation

There is no generalization possible in medicine. The pages included in this website are purely educational and have been presented for information purpose only. Each section has been prepared with utmost care but should not be used as a substitute for your own physician's advice and care. Please see conditions for use.