2.2 Construction of Virtual Laparoscopic Images
Preoperative CT was performed in all patients to examine individual variations in arterial, venous, and pancreatic anatomies. The preoperative CT imaging protocol included performing CT using a 64-row multi-detector CT scanner (Somatom Definition AS; Siemens) after systemic injection of a nonionic contrast agent (Iomeron (350mgI/135ml), 1.8 ml/kg; Eisai) at a rate of 4 mL/s with the following imaging parameters: 100 kV, 400 mA, section thickness of 0.75 mm, and collimation of 0.7 mm. The images were then uploaded to Synapse Vincent image processing software (FUJIFILM Medical Co., Tokyo, Japan) to review reconstructed pancreatic structures (i.e., pancreatic parenchyma, splenic vessels, and tumor tissue) and generate virtual laparoscopic 3D geometries that accurately represented the cartography of the pancreas. These images allow surgeons to confirm both the pancreatic parenchymal anatomy and the spatial relationship between vessels and tumors for enhanced safety during the procedure.
2.4 Selection of the Surgical Procedure
Initially, the ventral approach was used for type V (Figure 1) and the dorsal approach for type D (Figure 2) in dissecting the splenic artery. However, if the dissection proved difficult, the surgeon modified the procedure accordingly.
2.5 Operative Procedure
Under general anesthesia, patients were placed in the reverse Trendelenburg position with hemi-right lateral rotation. The first trocar was placed in the umbilicus to insert a laparoscope (Olympus Medical Systems, Tokyo, Japan) into the peritoneal cavity; intra-abdominal pressure was set at 12 mmHg. Under direct observation, a 12-mm trocar was inserted at the left lateral edge of the rectus abdominis muscle, followed by the insertion of 5-mm trocars in the bilateral subcostal areas and a 5-mm trocar along the left anterior axillary line. The surgeon stood on the left side of the patient, with the first assistant and camera operator standing on the right side.
The left hepatic lobe was kept retracted using a laparoscopic retractor inserted through the left subcostal trocar. A laparoscopic ultrasonic device (HARMONIC ACE+; Ethicon Endosurgery, New Brunswick, NJ, USA) was used for dissection and vessel coagulation. The greater omentum was divided below the gastroepiploic arch to open a window to the omental bursa, followed by the enlargement of the window to expose the pancreas.
For the ventral approach, the peritoneum was dissected along the superior pancreatic border to expose the splenic artery at the parenchymal dividing line. The inferior border of the pancreas was also dissected toward the splenic lower pole to liberate the pancreatic parenchyma. The pancreatic body was then separated from the retroperitoneum until the splenic vein could be visualized from the dorsal side.
For the dorsal approach, the splenic artery was exposed from the inferior border of the pancreas separating from the splenic vein. The pancreatic parenchyma was then liberated using the same procedure as used for type V cases.
After separation from the pancreas, the splenic artery was ligated using laparoscopic clips (LIGAMAX 5; Ethicon Endosurgery, New Brunswick, NJ, USA) and dissected. Following splenic artery dissection, the splenic flexure of the colon was taken down to achieve complete mobilization of the distal transverse and proximal descending colon from the tail of the pancreas. The gastrocolic ligament was then incised, completely exposing the tail of the pancreas. The gastrosplenic ligament and short gastric vessels were transected up to the superior pole of the spleen. The distal pancreas was then elevated and transected completely from the retroperitoneum.
For parenchymal dissection, laparoscopic ultrasonography was used to identify the location of the tumor and to reconfirm the surgical resection line that was preoperatively planned according to virtual laparoscopic imaging. A linear stapler was inserted through the left lateral 12-mm trocar. After pre-compression, the pancreatic parenchyma including the splenic vein was dissected. After complete dissection of the spleno-retroperitoneum ligament, the specimen was placed into a retrieval bag and removed through the enlarged umbilical trocar site.
2.7 Statistical Analysis
Continuous variables (such as age) were compared using independent-samples t-tests and categorical variables (such as sex) using chi-square tests. P < 0.05 (two-tailed) was considered significant for all tests. All statistical analyses were performed using JMP ver14 (SAS institute Inc., Cary, NC).