CT of the biliary tract is a method of radiation diagnostics, which is used to study the biliary tract and gallbladder. The technique allows you to study the lobular bile ducts of the liver, the common hepatic duct, the gallbladder and cystic duct, choledoch, as well as the overall structure and size of the liver. CT of the biliary tract makes it possible to identify concretions, their number, exact localization, size and degree of obstruction of the duct; inflammatory changes, developmental abnormalities, traumatic injuries and regional neoplasms. As a rule, CT of the biliary tract is performed with contrast enhancement. The native study is used when the patient is completely obturated or intolerant of X-ray contrast agents.
CT of the biliary tract is based on the use of X-rays. A CT scanner passes a small amount of radiation through the studied area of the body, while simultaneously recording its interaction with internal tissues. The latter are displayed on tomograms in the form of light or dark areas. Data processing takes place at various stages of the passage of rays through the body, which makes it possible to obtain a series of layered images. Despite the fact that computed tomography was introduced into medicine only in the 80s of the last century, at the moment CT of the biliary tract is a fairly popular diagnostic procedure. This is facilitated by the high detail of the images and the minimum amount of distortion and artifacts.
CT of the biliary tract is used in gastroenterology, oncology and abdominal surgery. Alternative diagnostic methods are RCPG, ultrasound and MRI of the liver and biliary tract. Ultrasound is a more common and relatively cheap study that allows you to visualize most of the bile ducts in real time. But unlike CT of the biliary tract, ultrasound scanning is not informative when the intrahepatic biliary tract is affected and does not make it possible to differentiate the structure of concretions, and its result depends on the professionalism of the doctor and the severity of the patient’s subcutaneous fat layer. Endoscopic retrograde cholangiopancreatography allows using classical radiography and a probe to visualize in detail most of the biliary tract. Its disadvantages are invasiveness, patient discomfort and high radiation load. MRI cholangiography shows the structure of the ducts well.
The indication for CT of the biliary tract is the uninformativity of physical examination and routine diagnostic methods against the background of the following symptoms: pain and a feeling of heaviness in the right hypochondrium, fecal acholia, dyspeptic syndrome, icteric sclera and mucous membranes, attacks of biliary colic, hepatomegaly. This study is used for suspected neoplasms, metastatic lesions, cysts and obturation of the biliary tract, the presence of concretions of various localization. Signs of cholangitis, cholecystitis, gallbladder polyps can serve as indications for CT of the biliary tract. It is also used to diagnose traumatic injuries and ruptures of the biliary tract. In some cases, CT is used to determine the approximate chemical composition of concretions, which is important for choosing the tactics of treatment of cholelithiasis: surgical intervention or extracorporeal shock wave lithotripsy.
Absolute contraindications to CT of the biliary tract are pregnancy (X-ray radiation has a teratogenic effect) and severe cardiovascular insufficiency with unstable hemodynamics (computed tomography excludes the possibility of cardiopulmonary resuscitation or intravenous drip administration of drugs). Also, CT of the biliary tract is not performed for preschool children, people suffering from claustrophobia, epilepsy or other mental illnesses with increased excitability – this category of patients is not able to maintain a static position during the study. If there is an urgent need for this study, drug sedation can be used.
CT of the biliary tract with contrast is contraindicated in patients with individual intolerance to X-ray contrast agents – in this case there is a high risk of anaphylactic reactions. Severe renal dysfunction also hinders the study, because they remove most of the contrast agents used from the body. Computed tomography with contrast enhancement is not performed for multiple myeloma, thyrotoxicosis and type II diabetes mellitus – against their background, the pharmacological drugs used can cause severe metabolic disorders or provoke decompensation. After performing CT of the biliary tract with contrast, nursing mothers are recommended to interrupt breastfeeding for a period of 12 to 36 hours.
Preparation for CT
Specialists such as a gastroenterologist, abdominal surgeon or oncologist can prescribe the passage of CT of the biliary tract. Preliminary preparation for this study with contrast enhancement implies the following: fasting 4-6 hours before the scan, conducting an allergy test with the injected drug and evaluating the excretory function of the kidneys – measuring creatinine and blood urea, calculating GFR. Native CT of the biliary tract does not require preparation. In addition, before starting the scan, you need to change into a special robe to prevent distortion of the images by metal elements of clothing. If the patient is unable to maintain a stationary position, a full-time anesthesiologist performs drug sedation.
Methodology of conducting
CT of the biliary tract is performed using a classical computed tomograph. Externally, it resembles a ring or a short tunnel with a horizontal couch in the middle. Before starting, the patient is briefly explained the course of the study and its actions inside the scanner, including the fact that at the command of the radiologist you will need to inhale and hold your breath. The need to delay breathing is due to the distortion of the images by the respiratory movements of the diaphragm and the displacement of internal organs. Next, the patient lies down on the couch and is placed inside the device. The duration of CT of the biliary tract is from 2 to 15 minutes. The use of contrast may be accompanied by general malaise, dizziness or nausea. These phenomena can persist for up to several hours after the study, after which they pass independently. CT of the biliary tract does not cause other complications.
Interpretation of results
Depending on the mode of operation of the medical institution, the issuance of CT results of the biliary tract can occur in the period from several hours to 2 days. The set of materials includes a CD-ROM with all the obtained tomographic images; a series of sections printed on film; a written or printed conclusion of a radiologist. The latter can also be supplemented with a detailed description of the detected deviations from the norm.
CT data of the biliary tract may indicate the presence of bile concretions, their localization and structure – they manifest as a defect in the filling of the biliary tract or gallbladder. The images may show cysts in the form of local extensions of one or more bile ducts. Cholangitis and cholecystitis on CT of the biliary tract are manifested by compaction of the walls of the biliary ducts or gallbladder. Malformations are indicated by additional biliary tract, stenosis or massive expansion of the ducts of the biliary tract, their deformation, etc.
This method of diagnostic makes it possible to identify tumors or metastases that are visualized as formations of different densities. Abscesses on the tomogram have the appearance of capsule-limited accumulations of purulent masses of a certain localization. Traumatic injuries in the images may be characterized by rupture of the ducts (the contrast goes beyond them) or the formation of hematomas (an accumulation of homogeneous fluid that does not have a capsule and is limited by internal tissues). CT of the biliary tract allows you to visualize foreign bodies, their localization and penetration into nearby organs and structures.