Introduction:
Liver resection has remained the best treatment option for primary liver cancer. The most frequently encountered primary liver cancer types are hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). For hepatocellular carcinoma, particularly anatomical resection of the tumor-affected areas is done to prevent the spread of cancer through the portal venous branches. Innovation in imaging studies has helped specialists to plan a pre-operative design of the procedure, navigate during the intraoperative period, and evaluate the postoperative quality after surgical resection. Early diagnosis and treatment of primary liver cancer are important to improve the prognosis. The best choice for treating HCC and IC types of primary liver cancer is hepatectomy.
What Are the Prerequisites for Precision Surgery?
An evaluation of liver functional reserve is important before performing hepatectomy so as to obtain a sufficient liver volume remnant. The degree of liver damage varies among patients as most of the patients have chronic hepatitis. Liver load test like indocyanine green (ICG) retention is performed before surgery. Individual evaluation of liver volume is done, and accordingly, treatment procedures are compared and chosen.
The crucial step during surgery to keep in mind is that sufficient surgical margins should be resected without leaving a tumor cell in solid tumors. Also, the micro metastases that sound like the main lesion should also be surgically removed, as the main feature of HCC progression is its spread into the portal vein and intrahepatic metastases. Tumor burden territory removal is important to completely remove cancer and microscopic intrahepatic metastasis (satellite lesions).
In ICC, limited liver resection with adequate surgical margins is important. When there is an invasion of the hepatic hilum, then an extended hemi-hepatectomy along with concurrent resection of the extrahepatic bile duct is important. Around ⅓ rd of the patients with ICC, have cancer that has metastasized into the lymphatic nodes. Therefore, preoperative assessment of the regional lymph nodes and intraoperative assessment are required. In such cases, an extended lymphadenectomy will be required.
How Is Image-Guided Precision Surgery Remarkable?
1. Planning the Procedure: The location of anatomical resection should be planned by identifying the main feeding artery and vein to the hepatocellular carcinoma using a dynamic CT (computed tomography) scan. Usually, there can be one or more vessels that are feeding the HCC and they have to be properly identified and resected. In case of intrahepatic metastases around the main tumor site, all portal venous branches should be resected. Recent advancements in three-dimensional (3D) simulation software have allowed physicians to visualize an instant display of this area in order to calculate the surgical territory with precision, and the territorial volume of any selected portal branch can be calculated and resected. This has also helped physicians to accurately know the post-operative results, like future remnant liver volume (FRLV), and also allows them to practice any method of surgical resection on the computer, and this is called virtual hepatectomy. The 3D simulation will help in the concomitant resection of a hepatic vein by showing the assumed drainage area, which will further help in preoperative evaluation with precision.
In determining the appropriate amount of liver tissue to remove, it is crucial to take into account both the size and spread of the tumor, as well as the liver's functional capacity. If the functional reserve of the liver is compromised due to an insufficient FRLV, then portal embolization before the hepatectomy may need to be considered.
2. Target Segment Recognition: An intraoperative ultrasonography (IOUS) is used to detect the target portal venous branch before the liver resection procedure. It can be difficult for non-expert liver surgeons to target the portal venous branch as it requires deep knowledge and practical experience in IOUS. Advancements in the intraoperative navigation system have helped overcome this. Due to the introduction of several navigation systems, synchronization can be obtained of the CT and IOUS images.
After ultrasonography images are matched with the CT image, the preoperative CT image will sync with the real-time image of IOUS. The process of matching is called registration. Several anatomical landmarks, such as the large tributary of the middle hepatic vein (MHV), bifurcation of the portal veins, or the bifurcation of the anterior and posterior portal veins, are marked annually during registration. A newer software generation now exists that utilizes an electromagnetic IOUS navigation system incorporating machine learning and artificial intelligence. This system aims to minimize positional errors and provide greater convenience through an automatic registration procedure.
3. Visualization and Recognition of Borderlines Between Segments: Post recognition of the porta branch to be resected, next is to assess the territory and visualize it. The most commonly employed method for this purpose is the dye-injection method. This involves the injection of an indigo carmine solution into the target portal branch using the IOUS imaging.
4. Anatomical Liver Resection Evaluation: An assessment should be made to determine if the hepatic veins on the transection liver plane are exposed clearly or not. The 3D simulation software produces a completion picture after liver resection, and it can be compared with the real view. The volume of segments to be resected can also be calculated using this software.
What Is Fluorescence Cholangiography?
Fluorescence cholangiography (FC) is a technique used to visualize the biliary tract during surgery. Previous studies have indicated that FC can be achieved through the intravenous or intra-biliary injection of indocyanine green (ICG). In cases where liver cancer surgery is performed along with laparoscopic cholecystectomy, it is common practice to inject 2.5 mg of ICG (in solution) intravenously to identify the cystic duct during the surgery and prevent damage to the bile duct. However, it is important to note that ICG is excreted through the bile and takes about 30 minutes after intravenous injection to reach the biliary system. Therefore, it is recommended to administer ICG in advance, before the patient arrives in the operating room.
Conclusion:
Advancements in imaging modalities have helped surgeons resect tumors and their borders with precision so as to minimize their recurrence and prevent their metastases. Preoperative and intraoperative images have provided promising results and significantly improved the prognosis. Image-guided precision surgery has been minimally invasive and has helped improve the lives of many patients.
