Key Terms: Anesthesia, Autopsy, Hemorrhage, Histology, Incision, Metastasis, Pelvis, Pneumothorax.
Definition
A CT-guided biopsy is a procedure by which the physician uses a very thin needle and a syringe to withdraw a tissue or fluid specimen from an organ or suspected tumor mass. The needle is guided while being viewed by the physician on a computed tomography (CT) scan.
Purpose
A definite diagnosis of cancer is almost always based on the histological examination of cell or tissue samples. The procedure used to obtain a specimen for this testing is called a biopsy. Biopsies can be performed by surgical removal of the specimen if the suspicious area is located near the surface of the body or during surgery. If, however, the suspected tumor is located deep inside the body and cannot be seen or felt by the physician, he may decide to perform a CT-guided biopsy. The main advantage of a CT-guided biopsy is that it does not require an incision, but the disadvantage is that in some cases, the needle may not be able to remove enough tissue for analysis.
Precautions
CT-guided biopsy can be performed on almost all organs of the body, for example on the lungs, liver, kidneys, adrenal glands, pancreas, and pelvis. The procedure is not indicated for the spleen because there is a high risk of severe post-biopsy hemorrhage. CT-guided biopsy is not indicated for patients with bleeding disorders such as hemophilia, or who are at risk for bleeding as a result of cancer treatments (chemo-radiation) or the cancer itself, as when a patient develops thrombocytopenia.
Description
The development of CT technology provided a powerful means to visualize the inner features of the human body which previously could only be seen during surgery or autopsy. Before CT, if a patient had a tumor located in the chest, abdomen, or pelvis, biopsies could only be performed with a surgical procedure. If the patient needed surgery so as to treat the tumor, then biopsy specimens were also collected at the same time for analysis. However, there was no way to obtain samples from patients whose tumors could not be treated with surgery, such as patients with metastatic cancer or with general conditions not allowing surgery. CT-guided needle biopsy has become a welcome alternative to surgical exploration and biopsy.
Preparation
The technique will vary depending on the site of specimen collection and the patient's general condition. In most procedures, the patient lies on the CT table on his back, or on either side, depending on where the needle is to be inserted. Some patients may require intravenous injection of pain killers. A CT scan is first performed, to locate the best site for needle insertion. The skin is then disinfected and anesthetized with its underlying tissue. The needle is inserted through the skin into the body. Another CT scan is perfomed to confirm that the tip of the needle lies at the desired location. When the tip of the needle is seen to be in the proper position, the biopsy specimen is withdrawn through the needle.
Aftercare
After the procedure, the patient is monitored in the hospital or clinic department or in an observation unit for a few hours, and then sent home.
Risks
CT-guided biopsy is a fairly safe procedure. The risks are certainly less than the risks involved with the alternative method, surgical biopsy. In any case, recovering from CT-guided biopsy takes considerably less time than it would if the biopsy were surgically performed.
Questions to Ask the Doctor
- Will the CT-guided biopsy procedure be painful?
- How many times will I need to have one?
- What is the normal success rate in obtaining enough tissue to make a diagnosis?
- What kind of complications may I experience at the biopsy site?
- When will I know the results?
The risks associated with CT-guided biopsy depend on the site where the biopsy specimen is collected. They include:
- Bleeding: Most patients have had their blood evaluated before the procedure. Although rare, bleeding can occur and may require surgery to control.
- Infection: An infection is possible whenever an object,—such as the needle used in CT-guided biopsy—, pierces the skin, —even if sterile procedures are always followed during the procedure. This is a very rare complication.
- Pneumothorax: Partial or total collapse of a lung is a reported complication in approximately 25% of lung biopsies. It is also a risk during CT-guided biopsies of the liver and adrenal glands.
Normal Results
A preliminary evaluation of the CT-guided biopsy specimen is often performed by the physician. If enough tissue has been obtained for the required tests, the procedure is terminated and the specimen is sent to the histology lab for analysis.
Abnormal Results
If the CT-guided biopsy has not been successful, it may be repeated or another biopsy procedure may be selected. Abnormal results indicate that a malignancy or other abnormality is present.
Resources
Books
Seeram, E. Computed Tomography: Physical Principles, Clinical Applications and Quality Control. W. Saunders & Co., 2001.
Periodicals
Sklair-Levy, M., Polliack, A., Shaham, D., Applbaum, Y. H., Gillis, S., Ben-Yehuda, D., Sherman, Y., and E. Libson. "CT-guided core-needle biopsy in the diagnosis of media-stinal lymphoma." European Radiology 10 (2000): 714-8.
—Monique Laberge, Ph.D.
