Kidney CT is a study of paired urinary organs with obtaining their layered image using X-ray radiation. It is indicated for the diagnosis of traumatic injuries, tumors, structural abnormalities, hydronephrosis, urolithiasis, abscesses and cysts. Tomography is used to examine the retroperitoneal space and the adrenal glands, to determine the site of taking the material during a biopsy, and to monitor the kidneys in postoperative patients. For more information, the examination can be carried out with the introduction of contrast agents.
Kidney CT is recommended for suspected congenital anomalies, neoplasms and metastases, polycystic kidney abscess; in the clinic of nephrolithiasis, not confirmed by ultrasound and traditional radiological methods; non-functioning kidney, detected by excretory urography or nephroscintigraphy; injuries of the kidney, hydronephrosis, etc. CT is also used to determine the site of a renal tissue biopsy, to assess the condition of the renal bed after a total nephrectomy or a donor kidney after transplantation. CT of the kidneys allows you to accurately differentiate tissue and fluid formations and determine their size, reveals the presence of urate stones that are not determined by survey urography.
Factors of refusal to perform computed tomography in favor of non-radiographic studies can be kidney failure, pregnancy, diabetes mellitus, which requires taking certain medications (metformin, etc.). A contraindication to conducting radiopaque CT of the kidneys is an allergy to iodine and iodide preparations.
When conducting a native (standard non-contrast) study of restrictions in the mode and nature of nutrition is not required. When using contrast 4 hours before CT, abstinence from eating is recommended. The question of the need to introduce contrast is decided by a radiologist, based on the task of the study. Before the procedure, the patient is asked to remove jewelry and metal products that fall into the scanning area. Kidney CT is performed on an X-ray table, where the patient is placed on his back and fixed.
Methodology of conducting
The table on which the patient lies is brought behind the arch of the scanner and the tomograph is turned on. The scanner, rotating around the body body, performs a series of tomograms at different angles. During the scanning procedure, the patient should be motionless. When performing a kidney CT scan, a short-term respiratory delay may be required. If necessary, after the first series of radiographs, contrast is injected intravenously and tomographic examination of the kidneys is continued. If an allergic reaction to contrast appears in the form of difficulty breathing or urticaria, you should inform the doctor who is monitoring the progress of the study, or press the call button.
X-ray radiation is recorded using sensors. The information transformed by the computer is fed to the monitor in the form of an image, which is interpreted by a radiologist. The quality of images obtained by CT of the kidneys may be affected by the patient’s motor anxiety, the presence of surgical clips or catheters, barium suspension in the gastrointestinal tract after radiography of the esophagus and stomach, small intestine or irrigoscopy.
Interpretation of results
The topography of the kidneys by CT is estimated relative to neighboring formations. The size and shape of the kidneys are determined by the slices between the poles and their contours. The unchanged parenchyma of the kidneys has a slightly higher density compared to the hepatic one, but is many times inferior to the density of bone tissues. On native tomograms, the collective tubules are expressed in a dark color; when contrast is introduced, their density increases, and the shade lightens. The density of the volumetric formations determined by CT of the kidneys differs from the density of the normal parenchyma. Kidney cysts are differentiated in the form of thin-walled formations with sharp borders and lower density.
The tumor, including kidney cancer, has fuzzy borders and heterogeneous density, but less than the unchanged parenchyma, even after contrast. Tumors with foci of calcification, hemorrhage, necrosis are more dense. Vascular formations after contrast administration are visualized more clearly. CT can also diagnose urinary tract obstruction, urolithiasis, polycystic disease, developmental abnormalities, fluid accumulation in the paranephral tissue (hematomas, abscess, lymphocele). Pathological formations detected in the projection of the renal bed after nephrectomy indicate a recurrence of the tumor.
The radiation load used in kidney CT, as a rule, does not cause complications. When contrast agents are administered, allergic manifestations (urticaria, edema, itching) may occur. In rare cases, the introduction of contrast can provoke the development of renal failure, especially in patients taking glucophage. Usually, the study is carried out satisfactorily and does not provoke a deterioration in the patient’s well-being.