Ultrasound signs of pancreatic cancer

Comprehensive ultrasound examination of pancreatic cancer

Based on ultrasound data, an algorithm for examining patients suffering from pancreatic cancer has been developed:

• Real-time transcutaneous B-mode imaging, widely used to detect pancreatic tumors, is essentially a screening method that begins a patient's examination;
• Color Doppler scanning or B-mode examination in combination with the use of carbon dioxide (CO2 microbubbles ₎ as a contrast agent provides additional opportunities in the differential diagnosis of the tumor process and inflammatory changes in the pancreas;
• Color Doppler scanning using the color Doppler or EDC modes provides information on the nature of the relationship between the tumor and the vessels of the portal vein system, the inferior vena cava system, as well as the aorta and its branches.

If the diagnosis is not finally established, then based on the results of a comprehensive ultrasound examination, a decision is made on the choice of the necessary additional research method or their combined use. These include: ultrasound endoscopic examination, ultrasound intraductal examination, percutaneous aspiration biopsy of the pancreas under ultrasound control. Intraoperative ultrasound examination allows you to clarify the type and scope of the operation.

Pancreatic cancer diagnostics in B-mode in real time is based on direct and indirect signs. Direct signs include detection of a solitary lesion or cavity of non-uniform density with a demarcation line between the tumor and pancreatic parenchyma. Tumor reorganization of the pancreatic parenchyma is the main direct sign of the tumor. Reorganization of the structure in the affected area causes a change in the intensity of the reflection of echo signals from the tumor. The following variants of tumor echogenicity are distinguished: hypoechoic, hyperechoic, isoechoic and mixed.

According to our B-mode ultrasound data of 131 patients with pancreatic adenocarcinoma, the localization of the process in the head was noted in 62% of cases, in the body - in 12%, in the tail - 24% and total lesion - in 2% of cases. In most cases, hypoechoic formations were diagnosed - 81.7%, mixed echogenicity - in 10.7% of cases, hyperechoic - in 4.5% and isoechoic - in 3.1% of cases.

The ability of B-mode ultrasound to diagnose tumors depends on the location and size of the tumor. Depending on the size of the tumor, the size of the gland may remain unchanged or a local or diffuse increase may be noted.

Indirect signs of adenocarcinoma include dilation of the pancreatic duct and dilation of the common bile duct (CBD). Obstruction of the main pancreatic duct (MPD) due to compression or tumor invasion may occur directly in the area of its transition to the ampulla with subsequent dilation distal to the level of obstruction. In this case, a duct with a diameter of more than 3 mm is visualized in the body and/or head. We have noted dilation of the main pancreatic duct from 4 to 11 mm in 71% of cases with tumor localization in the head of the pancreas. When the tumor is localized in the head of the pancreas and close to the intrapancreatic part of the common bile duct, obstruction of the common bile duct develops due to tumor invasion, circular compression by the tumor, or tumor growth into the lumen of the duct. With a common bile duct diameter of 12-17 mm, the lumen of the intrahepatic bile ducts reached 8 mm in combination with an increase in the size of the gallbladder. Dilation of the intrahepatic bile ducts may be due to the presence of a tumor in the head of the pancreas or lymph nodes in the area of the hepatoduodenal ligament.

When cancer is localized in the area of the uncinate process, it is not always possible to adequately visualize and evaluate changes at an early stage of the disease using B-mode ultrasound data. As the process spreads and infiltrates the head of the pancreas, the tumor masses reach the level of the terminal section of the common bile duct. However, these changes are usually diagnosed at a late stage of the disease. Therefore, a tumor originating from the uncinate process is characterized by dilation of the common bile duct, the common bile duct, and the development of jaundice at a late stage of the disease.

It is necessary to differentiate the echographic picture of cancer primarily from local forms of pancreatitis, cancer of the major duodenal papilla, sometimes pseudocysts, lymphomas, metastases in the pancreas. It is tactically important to take into account clinical and laboratory data in combination with biopsy results.

Additional opportunities in differential diagnostics of tumor process and inflammatory changes of pancreas are opened by application of color Doppler scanning in color Doppler, EDC and/or B-mode in combination with carbon dioxide. We analyzed additional opportunities of obtaining necessary information by means of color Doppler scanning. When using this technique, presence of vessels, character and velocity of blood flow in them were determined. During duplex scanning in patients with pancreatic cancer either absence of blood flow of vessels inside the tumor is noted or vessels with predominantly arterial blood flow of collateral type, diameter of 1-3 mm, BSV-10-30 cm/s are registered. Vessels enveloping the tumor in the form of a rim were not revealed in any observation.

To enhance the ultrasound signal reflected from erythrocytes, echo contrast agents are used. In our work, Levovist was used. The studies were conducted in two stages in three patients with pancreatic cancer and six with chronic pancreatitis. At the first stage, an ultrasound study of the vascular bed in the head of the pancreas was performed. At the second stage, blood flow in the vessels of the head of the pancreas was assessed after intravenous administration of 6 ml of Levovist at a concentration of 400 mg / ml, with subsequent comparison of the intensity of signals from the blood flow before and after the use of Levovist. In pancreatic cancer, at the first stage of the study, blood flow inside the tumor was absent in three patients. After the introduction of Levovist, arterial vessels up to 2 mm in diameter with a collateral type of blood flow were clearly visualized in two cases for one to two minutes after 15-20 s. Among 6 patients with CP, at the first stage, arteries with the main type of blood flow and veins were visualized in the head of the pancreas in four cases. At the second stage, the registration of the course of previously recorded vessels significantly improved. In the remaining observations, an image of vessels, mainly veins, appeared that had not been determined previously. Thus, based on the accumulated experience, we recommend the use of color Doppler scanning in the CDC _: EDC modes in complex diagnostic situations for the differential diagnosis of pancreatic diseases.

The simplest substance that enhances the image in B-mode is carbon dioxide (microbubbles of CO ₂ ). The introduction of CO ₂ microbubbles into the celiac trunk during angiographic examination when studying the pancreas using ultrasound in B-mode is essentially a combined diagnostic method. The use of carbon dioxide makes it possible to more clearly confirm and differentiate the nature of the process in the pancreas. According to the data of Kazumitsu Koito et al., when examining 30 patients with pancreatic cancer and 20 with chronic pancreatitis, depending on the filling of the affected area with CO ₂ microbubbles, the presence and degree of vascularization were diagnosed. The authors found that the cancerous tumor in 91% of cases is hypovascular, the CP zone in 95% of cases is isovascular. Comparison of the results of B-mode ultrasound using carbon dioxide, computed tomography and digital subtraction angiography in the differential diagnosis of pancreatic cancer and CP showed that the sensitivity of the methods is 98%, 73% and 67%, respectively.

One of the key moments in determining the resectability of cancer is the assessment of the state of the main vessels and the degree of their involvement in the tumor process. Already at the preoperative stage, the necessary information can be obtained from the ultrasound examination data. When cancer is localized in the head of the pancreas, as a rule, a targeted study is carried out of the superior mesenteric vein, portal vein and its confluence, superior mesenteric artery, common hepatic artery and celiac trunk, in the body - the celiac trunk, common hepatic and splenic arteries, in the tail - the celiac trunk and splenic vessels. The state of the inferior vena cava is also important in determining the resectability of the tumor. In our opinion, to assess the state of the vessels according to the data of color Doppler scanning, it is advisable to analyze:

1. Localization and anatomical location of the main arteries and veins relative to the tumor (the vessel does not contact the tumor, contacts the tumor, is located in the tumor structure).
2. Conditions of the vessel wall and lumen (echogenicity of the vessel wall is unchanged, increased; lumen size is unchanged, changed at the site of contact with the tumor).
3. The values of linear blood flow velocity along the entire length of the vessel, accessible to ultrasound visualization.

When a vessel contacts a tumor, recording a local increase in LSC indicates the presence of hemodynamically significant extravasal compression of the vessel by the tumor. In such a situation, information on tumor invasion into the vessel wall is of primary importance for determining tumor resectability. Increased echogenicity of the vessel wall at the site of contact with the tumor indicates either tumor fixation or tumor invasion of the vessel wall. Increased echogenicity of the wall and the presence of a substrate in the lumen of the vessel indicate tumor invasion of the vessel. The absence of an ultrasound image of a vessel whose anatomical course is located in the tumor structure also indicates vessel invasion. In addition, pancreatic cancer often causes a parietal or occlusive thrombus in the superior mesenteric vein and/or splenic vein. Thrombosis from these veins can also spread to the portal vein.

Today, three-dimensional reconstruction of a pancreatic tumor and adjacent main vessels using a combination of B-mode and angiography allows us to assess their anatomical relationship and the degree of contact. However, to resolve the issue of the state of the vessel wall at the site of contact with the tumor, the data obtained using the B-mode are of primary importance. Comparison of the capabilities of the B-mode in two-dimensional scanning and three-dimensional reconstruction indicates a higher resolution of the method in three-dimensional ultrasound imaging. Structural features and the contour of the wall, as well as the state of its echogenicity, are more clearly recorded, which is of great clinical importance in determining indications for surgical treatment of patients suffering from pancreatic cancer.

The three-dimensional reconstruction method is effective in assessing the condition of the vessel wall and has less clinical significance in assessing the ultrasound characteristics of the pathological lesion. Improvement of the tumor image in B-mode with three-dimensional reconstruction compared to two-dimensional scanning (tumor borders are more clearly visualized, structural features are more clearly determined) is not strictly necessary information for deciding on the resectability of pancreatic cancer.

Such information at the preoperative stage allows us to determine the tactics of patient management and decide on the possibility of tumor removal with or without reconstruction of the affected segment of the vessel.

Analyzing our material, based on the results of examination of more than 50 patients with focal lesions of the pancreas, we came to the conclusion that in order to assess the condition of the wall, lumen of the vessel and to decide on the possibility of performing surgical treatment and its volume in patients with pancreatic cancer, the indication for three-dimensional reconstruction is the presence of a pancreatic tumor in contact with the main vessels.