Jejunal veins corresponding to the DJUV (Fig. 2)
Either J1V or J2V corresponded to the DJUV in all cases. J1V was the DJUV (Type 1) in 89 cases, whereas J2V was the DJUV (Type 2) in 11 cases. The DJUV was divided into two subtypes depending on its positional relationship with the SMA, i.e., running dorsal (subtype a) or ventral (subtype b) to the SMA. There were 74 cases of Type 1-a, 15 cases of Type 1-b, 8 cases of Type 2-a, and 3 cases of Type 2-b (Fig. 2). Among the Type 2-a and Type 2b cases, J1V drained into the splenoportal confluence (splenic vein near the confluence of the SMV) in 3 and 2 cases, respectively.
Anatomical variations in the IPDV (Fig. 3)
As the IPDVs could not be visualized in 8 cases, 92 cases were analyzed. Three variations were identified: the IPDV drained into the DJUV only; it drained into the SMV only, or it drained into both. Variations were observed in 37, 20, and 11 cases, respectively, for Type 1-a patients; in 3, 9, and 1 case for Type 1-b patients; in 1, 6, and 1 case for Type 2-a patients; and in 0, 0, and 3 cases for Type 2-b patients, respectively. In no case did the IPDV join the SMV distal to the DJUV.
Anatomical variations in the IPDA (Fig. 4)
Only one IPDA was confirmed in most cases. The IPDA branched from the J1A in 53 cases, branched directly from the SMA in 34 cases, branched from the J2A in 3 cases, and branched from the replaced right hepatic artery in 3 cases. Two IPDAs were observed in the remaining 7 cases: one from the J1A and the other from the SMA (n = 4); both from the J1A (n = 2); and one from the J1A and the other from the J2A (n = 1). The IPDA(s) bifurcated from the more cranial side than the MCA and the DJUV intersecting point in all cases.
Distance between the MCA bifurcation and the DJUV intersecting point (Fig. 5)
According to General Rule for the Study of Pancreas Cancer edited by the Japan Pancreas Society, the lymph nodes located between the bifurcation of the MCA and the root of the SMA are regional in cases of cancer of the head of the pancreas [20]. If the distance between the bifurcation of the MCA and the intersection of the DJUV and SMA (DJUV intersecting point) is short, dissecting along the DJUV will reach the SMA at around the bifurcation of the MCA, which is at the distal end of the regional lymph nodes. Matched was defined as a distance of within 10 mm. When the DJUV was equivalent to the J1V (Type 1), the matching rate was 87.8% for the dorsal type and 73.3% for the ventral type. When the DJUV was equivalent to the J2V (Type 2), the rates were 50% and 33.3%, respectively. The matching rate in all cases was 81%. Of the 19 non-matching cases, the DJUV crossed the SMA 11 mm or more cephalad to the MCA bifurcation in 12 cases.
Number of jejunal arteries branching between the root of the SMA and the DJUV intersecting point
A single jejunal artery (J1A) was identified in 11 cases. Two arteries (J1A and J2A) were detected in 53 cases, 3 arteries (J1A, J2A, J3A) in 29 cases, and 4 arteries (J1A, J2A, J3A, and J4A, in 7 cases (Table 1).
Table 1
The number of cases in which jejunal arteries branch between the root of the SMA and the DJUV intersecting point
Jejunal artery branch | Number of cases |
---|
J1A | 11 |
J1A + J2A | 53 |
J1A + J2A + J3A | 29 |
J1A + J2A + J3A + J4A | 7 |
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Surgical techniques for resecting the mesopancreatoduodenum using the DJUV as a landmark
The following is our standard procedure for typical anatomy.
a) The resection of the caudal border of the mesopancreatoduodenum at the
DJUV confluence area from the right side
The SMV is identified in the inferior border of the pancreas. After dividing the gastrocolic trunk, the SMV trunk is detached toward the caudal side. After the uncinate process is identified, the DJUV is confirmed by further detaching to the caudal side of the SMV. The IPDV that connects the uncinate process to the SMV trunk and/or the DJUV should be divided carefully. We sequentially dissect the veins from the region of the SMV- DJUV confluence while inverting the SMV. The DJUV bifurcation is confirmed behind the SMV and serves as a landmark of the endpoint during mesopancreatoduodenum resection. If the IPDV can be resected during the initial stage, the mesopancreatoduodenum resection can easily be performed via the derotation method [16].
b) Resection of the caudal border of the mesopancreatoduodenum using the JDUPV
The retroperitoneum is dissected from the left side of the ligament of Treitz, and the abdominal aorta, inferior vena cava, and left renal vein are exposed. After dividing the jejunum 20–30 cm from the anal side of the ligament of Treitz, the marginal vessels are followed to the DJUV. As shown in the present study, the DJUV runs with the jejunal artery dorsally via the dorsal side of the SMA in most cases. Therefore, the DJUV is easily identified by dividing the mesojejunum serosa from the dorsal side. The SMA is surrounded by a nerve plexus and was identified at its left-anterior aspect; the MCA was identified around the intersecting point of the DJUV. Then, the dissection of the mesojejunum from the ventral side communicated with the dissection from the dorsal side with the DJUV as a caudal surgical margin. The dissection of the mesojejunum was promoted to the cranial side toward the origin of the SMA along with the regional lymph node resection, and the common trunk of the IPDA/J1A was divided at the posterior aspect of the SMA. The IMV was dissected from the mesojejunum as the left side surgical margin. The dissection of the anterior-to-posterior aspect of the SMA was promoted to its origin, and the ligament of Treitz was dissected at the left aspect of the SMA. After dividing the ligament of Treitz, the left renal vein was identified by prior dissection as the dorsal surgical margin. The dissection of the mesopancreatoduodenum and uncinate process from the SMA was almost completed toward the right aspect of the SMA with rotation of the SMA counterclockwise using a left-sided approach. The dissected part of the mesopancreatoduodenum on the left side is connected to the exfoliated area around the DJUP confluence of the SMV; excision of the caudal side of the mesopancreatoduodenum is then completed. Finally, the jejunum and mesojejunum are pulled through to the patient’s right side, and the connective tissue between the SMA and the head of the pancreas, which is called the “second portion of the pancreatic head plexus (PLphII)” [20] in Japan, was dissected toward the origin of the SMA.