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Veins in the paraumbilical region were investigated in eight fresh cadavers, in which radiopaque materials were injected into both the arterial and the venous systems, to determine their locational relationship to the arteries. Veins in the skin and subcutaneous tissue consisted of venae comitantes and non-venae comitantes. The main trunk of the non-venae comitantes was the superficial inferior epigastric vein, and it formed a polygonal venous network in the skin layer. A large communicating vein, which did not accompany an artery, connected the venous network to a vena comitans of a large paraumbilical arterial perforator. Venous blood that had perfused the dermis of the paraumbilical region had two kinds of pathways to a deep vein: through the superficial inferior epigastric vein to the femoral vein and through the vena comitans to the deep inferior epigastric vein.
In previous radiographic studies of blood vessels, investigators have injected contrast medium in either the arterial or the venous system, so it was difficult to understand the locational relationship between arteries and veins.
In order to observe both arteries and veins simultaneously, we had taken the new approach of injecting contrast medium into both the arterial and the venous systems of the same cadaver.
By this method, there found to be venae comitantes and non-venae-comitantes in the skin and subcutaneous tissue. Non-venae comitantes were basically derived from venae comitantes and formed a mainly polygonal venous network in the skin layer. These veins were considered to play a role in the drainage of venous blood that had perfused the dermis, and, in this sense, they were called cutaneous veins. The paraumbilical arterial and venous perforators has been used as the pedicle of the paraumbilical perforator flap, but there was no anatomic and clinical studies to clarify the locational relationship between the superficial inferior epigastric vein and the paraumbilical arterial and venous perforators.
The vascular anatomy of the lower anterior abdominal wall: a microdissection study on the deep inferior epigastric vessels and the perforator branches.
In this study, we report the result of our investigations into the relationships between arteries and veins in the paraumbilical region.
1. Materials and methods
Whole-body injection of lead-oxide-gelatin mixture into the arterial system was performed in eight fresh cadavers. The skin and the underlying subcutaneous adipofascial tissue of the hemiabdomen were elevated en mass. Barium-sulphate-gelatin mixture was additionally injected into veins just under the dermis.
Numerous veins from which contrast medium leaked in cross-section or on the undersurface of the specimen, were ligated. Then each specimen was radiographed stereoscopically in order to clarify the three-dimensional relationship between the arteries and the veins. On the other hand, whole-body injection of lead-oxide-gelatin mixture into the venous system was performed in five fresh cadavers, and only the skin was elevated in the paraumbilical region. Each specimen was stereographically radiographed.
2. Results
In the paraumbilical region, a relatively large paraumbilical arterial perforator with a large skin territory existed in each specimen, and it was accompanied by a vein. On the other hand, the superficial epigastric vein located in the paraumbilical region, and it did not accompany an artery. Branches of the superficial inferior epigastric vein formed a polygonal venous network in the superficial layer of the region, and veins of the venous network also did not accompany an artery (Fig. 1) . Numerous small veins from the venous network were observed. Most of them were ascending and some were descending. Existence of valves was confirmed as small diverticular projections at the sites where the small veins arose (Fig. 2) . The polygonal venous network was connected to the vena comitans of the large paraumbilical arterial perforator by large and small communicating veins. In the six hemiabdomens, a large communicating vein was given off from the vena comitans in the proximal portion of the large paraumbilical arterial perforator, and did not accompany an artery, and then anastomosed with the polygonal venous network. Some small communicating veins were observed in the middle or distal portions and anastomosed with small veins of the polygonal venous network (Fig. 3) . In the two hemiabdomens, those communicating veins were also observed, but the large communicating vein anastomosed directly with the main trunk of the superficial inferior epigastric vein in the proximal portion. A schematic representation of the relationship between the arteries and the veins in the paraumbilical region is shown in Fig. 4.
Fig. 1(Left) Arteriovenogram of the skin and subcutaneous tissue of the left abdomen. The superficial inferior epigastric vein (SIEV) gave off branches (triangles) and formed a polygonal venous network. Paraumbilical arterial and venous perforators (*) were observed, but in two-dimension, the three-dimensional architecture between the polygonal venous network and the paraumbilical arterial and venous perforators was unknown. (Right) A trace of the angiogram; black lines indicate the large paraumbilical arterial perforator and its branches, and gray lines indicate veins. U, umbilicus; Scale bar: 1 cm.
Fig. 2Enlargement of a polygonal venous network in the left abdomen. Stereographic venograms. Do cross-set eyes, as the left and right white circles in the venograms become three white circles, and then gaze into the central venogram. The central venogram can be seen three-dimensionally. The venous polygon had small ascending veins (arrows) and small diverticular-like projections (triangles) which indicates existence of valves. Scale bar: 1 cm.
Fig. 3(Above) Stereographic angiograms of a large paraumbilical arterial and venous perforators. (Below) A trace of the angiogram; black lines indicate arteries and gray lines indicate veins. The large communicating vein (LV) was given off from the vena comitans (triangles) of the large paraumbilical arterial perforator and anastomosed with the polygonal venous network. Some small communicating veins (arrows) were observed and anastomosed small veins of the venous network. SIEV, superficial inferior epigastric vein. Scale bar: 1 cm.
Fig. 4Schematic representation between the superficial inferior epigastric vein (SIEV) and the large arterial and venous paraumbilical perforators. (Left) The large communicating vein (an arrow) anastomosed with the polygonal venous network, and (Right) it (an arrow) anastomosed with the main trunk of the superficial inferior epigastric vein.
The numerous ascending veins from the polygonal venous network, the polygonal venous network and the large communicating vein were also observed in the scapular region.
We called those veins that did not accompany arteries cutaneous veins, because we considered that venous blood that had perfused the dermis was mainly drainaged through the veins. The cutaneous venous system that was observed in the paraumbilical region was also considered to perform the same role. However, there was a great difference between the scapular and paraumbilical regions. In the scapular region, a polygonal venous network in the skin layer were formed by large communicating veins from the scapular and parascapular veins, but in the paraumbilical region branches of the superficial inferior epigastric vein chiefly formed a polygonal venous network. Accordingly, venous blood that had perfused the dermis in the scapular region entered only the circumflex scapular vein. However, in the paraumbilical region, the venous blood entered deep veins through the two kinds of pathways. One is through the superficial inferior epigastric vein to the femoral vein. The other is through the large or small communicating veins, via the venae comitantes of the paraumbilical perforator, to the deep inferior epigastric vein. In the physiological state, it cannot be said exactly which pathway is dominant for venous drainage of the dermis, but distribution of the cutaneous vein is considered to suggest that the superficial inferior epigastric venous system will be dominant for venous drainage from the dermis of the abdomen. Further, the venous territory of the superficial inferior epigastric vein is clearly larger than that of the venae comitantes of the large paraumbilical arterial perforator. Accordingly, in previous clinical studies of the paraumbilical flap,
The vascular anatomy of the lower anterior abdominal wall: a microdissection study on the deep inferior epigastric vessels and the perforator branches.
the large paraumbilical arterial and venous perforators have been always used as the anastomosing vessels, but using the superficial inferior epigastric vein as a drainage vein is considered to lead to safe extension of the flap. This idea corresponds to the free radial forearm flap using the cephalic vein as a drainage vein.
Acknowledgements
This work was supported in part by grant from the Ministry of Education, Culture, Sports, Science and Technology to N.I., H.N. and S.A.
References
Cormack G.C.
Lamberty B.G.H.
The arterial anatomy of skin flaps. Churchill Livingstone,
Edinburgh1986
The vascular anatomy of the lower anterior abdominal wall: a microdissection study on the deep inferior epigastric vessels and the perforator branches.
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