CT lymph nodes is a layered scan of lymph nodes of a certain localization (usually 1-2 zones) using X-ray radiation. During the study, it is possible to detect an increase, heterogeneity and change in the contours of lymph nodes, the formation of conglomerates and packages, infiltration of nearby tissues. The technique is used to detect lymphogenic metastasis in tumors of other organs and tissues, to assess the condition of lymph nodes in malignant lesions of the blood system and lymphatic system, infectious and autoimmune pathologies. To increase the informative value of CT lymph nodes, in some cases, it is carried out with contrast.
CT of the lymph nodes is performed independently or is a complementary study, it is prescribed together with CT and MRI of various organs and systems in which malignant neoplasms are presumably located, which are a possible source of metastases. The list of indications for native scanning includes:
- Lymphogenic metastasis. Confirmation of the presence or absence of cancer metastases in the lymph nodes in malignant neoplasms of various localization allows you to choose the optimal tactics for the treatment of cancer.
- Malignant lesions of lymphoid tissue. The study is prescribed for non-Hodgkin’s lymphomas and lymphogranulomatosis, which are usually accompanied by hyperplasia of the cervical and / or supraclavicular, less often inguinal, pelvic, intra–abdominal lymph nodes and mediastinal nodes.
- Lymphocytic leukemia. One of the manifestations of diseases of this group is generalized lymphadenopathy with a predominant increase in intra-thoracic and abdominal lymph nodes. Pathologies are also characterized by enlargement of the liver and spleen, anemia, asthenia and increased bleeding.
- Autoimmune diseases. Rheumatoid arthritis, sarcoidosis and other autoimmune lesions, along with joint involvement, are manifested by adenopathy in combination with damage to the eyeballs, spleen, liver, lungs and other organs.
- Infectious diseases. An increase in lymph nodes is noted in tuberculosis, toxoplasmosis, AIDS, and a number of other infections. The purpose of CT is usually to differentiate infectious and metastatic lesions of the lymphatic system.
- Insufficient information content of other methods. The procedure is carried out with ambiguous results of external examination, ultrasound, radiography and other methods prescribed at the initial stages of diagnostic search.
CT lymph nodes with contrast is used in clinical practice less often than native. Contrast examination is used to assess the condition of lymph nodes surrounded by adipose tissue or located near large vessels. Contrast is usually introduced when studying the lymph nodes of the neck, pelvis, abdominal cavity and axillary lymph nodes in malignant tumors of the mammary glands.
Limitations in using the technique are due to X-ray radiation and some technical aspects of the procedure. The list of contraindications corresponds to those when scanning other areas. Contrast-free CT is not prescribed in the following cases:
- The gestation period. X-ray radiation has a teratogenic effect on the fetus, can cause congenital anomalies, and in the early stages of pregnancy lead to its spontaneous termination.
- The serious condition of the patient. If artificial ventilation of the lungs is necessary, severe hemodynamic disorders, continuous infusions of drugs, it is impossible to place the patient inside a CT scanner.
- Problems with maintaining immobility. Early childhood, intense pain, claustrophobia, some mental illnesses, neurological disorders with hyperkinesis cause problems while maintaining a stationary state during scanning. Sometimes the study is carried out using anesthesia or sedatives.
- Severe obesity. Computer tomographs have load capacity limitations.
Contrast CT lymph nodes has additional contraindications. These include intolerance to iodine preparations (allergic reactions are possible, including anaphylactic shock and Quincke’s edema), some chronic diseases. The introduction of contrast in iodine-dependent thyroid pathology, thyrotoxicosis, diabetes mellitus and multiple myeloma can cause decompensation or the development of severe metabolic disorders.
Special preparation for contrast-free tomography is not required. The patient provides all available medical information related to the underlying pathology: referral for CT, extracts from medical histories, conclusions of specialists of various profiles, data from instrumental and laboratory studies (ultrasound, radiography, tests for cancer markers). Before contrast CT lymph nodes, a general urinalysis, biochemical and general blood test are prescribed to assess the state of the kidneys. To prevent anaphylactic reactions, an allergy test is performed with the selected contrast agent.
Methodology of conducting
The patient is taken to the locker room, where he removes all metal objects, changes into special underwear, and then goes into a room with a CT scanner. The doctor tells the patient about the specifics of the procedure, after which the patient is placed on a special table that is moved inside the scanner. Scanning without using contrast does not cause any sensations, the operation of the device is accompanied by clicks and a soft hum. When a contrast agent is administered, some patients experience weakness, nausea or dizziness, which disappear on their own within a few hours. The duration of the study ranges from a few minutes to half an hour.
Depending on the workload of the radiology doctor, the conclusion is prepared within a few hours or 1-2 days. The scan results can be obtained in printed form. In many medical institutions, for a small additional fee, the conclusion is sent by e-mail or recorded on electronic media. In the description of the CT, the radiologist lists the detected changes, interprets them, and indicates a preliminary diagnosis.
Interpretation of results
A common sign of lymph node damage is hyperplasia – an increase in the diameter of one node of more than 0.8-1 cm. Other changes are determined by the nature of the underlying disease:
- With lymphogranulomatosis, an increase in single lymph nodes or the formation of packets in the neck, inguinal, supraclavicular, less often in other areas is detected. The structure of the nodes is homogeneous.
- In non-Hodgkin’s lymphomas, conglomerates, lymphoid infiltrate in the zone of 3-4 or more groups are determined. The structure of lymph nodes is heterogeneous, signs of decay are visualized.
- With lymphogenic metastasis, heterogeneity of the structure, violation of contours, the appearance of calcification zones in regional lymph nodes is noted.
- In autoimmune pathologies, there is a violation of the uniformity of the structure, areas of calcification.
- Infectious diseases and lymphocytic leukemia are usually accompanied by an increase in lymph nodes while maintaining uniformity and clarity of contours.