CT Anatomy of the Pancreatic Head

The vessels around the head of the pancreas can be identified on CT by following the course of the SMV, the gastrocolic trunk, the gastroduodenal artery, the posterior SPDA and SPDV, the anterior SPDA and SPDV, the proximal jejunal vessels, and the IPDA and IPDV (Fig. 12-3). These vessels form excellent anatomic landmarks around the head of the pancreas. At the level of the cranial portion of the head of the pancreas, the gastro-duodenal artery is located in the retropyloric space at the anterolateral surface and can be seen in almost every case. The posterior SPDA and SPDV can be identified along the posterior lateral surface accompanying the bile duct in 72-88% of CT scans.11-13 The posterior SPDV can be followed cranially, and it drains into the caudal surface ofthe suprapancreatic segment of the portal vein. Medial to the pancreatic head and behind the pancreatic neck, the SMV is routinely seen here, and on occasion, the branch of the dorsal pancreatic artery to the head of the pancreas may be seen. The 1MV can be seen draining into the left side of the SMV in this location in 5070%.

At the midlevel of the head of the pancreas, the anatomic landmark is the gastrocolic trunk where it enters into the SMV.15 Although the branching patterns that form the gastrocolic trunk may vary, the site where it enters into the SMV and the position of the SMV in relationship to the head of the pancreas are constant. The gastrocolic trunk enters into the SMV anteriorly, and the SMV is usually anterior and medial to the head. The position of the posterior SPDV and the bile duct remains the same at the posterolateral surface of the head of the pancreas. The anterior SPDA continues the same course of the gastroduodenal artery at the anterolateral surface of the head, but the anterior SPDV can be seen draining into the gastrocolic trunk. The anterior SPDV is a small vein that is closely approximated to the head. Its course can be similar to a larger right colic vein that is located at the root of the transverse mesocolon and also drains into the gastrocolic trunk. This may explain the difference in the ability to identify this vein, as reported by Crabo et al. and Ibukuro et al. (98% vs. 50%, respectively).11,12 At this same level of the head of the pancreas, the branches of the IPDV may be identified at the posterior surface of the head as it forms a network with the posterior SPDV.

At the level of the caudal portion of the head and the uncinate process, the IPDV can be identified medial to the head as it connects with the proximal jejunal vein before entering into the posterior wall of the SMV. This type of anatomy can be seen in 66-90% of cases. The branching pattern of the IPDA and proximal jejunal artery is similar to that of the veins.

Pancreatic Vascular Anatomy

Fig. 12—3. Arterial anatomy of the pancreas (see text).

(a) The gastroduodenal artery (arrow) is behind the pylorus (P). The posterior superior pancreaticoduodenal artery (PSA) accompanies the bile duct (BD). The dorsal pancreatic artery (arrowhead) gives off a branch medial to the pancreatic head. D = duodenum.

(b) The gastroepiploic artery (large white arrow) is branching out from the gastroduodenal artery (small white arrow),

(c) The anterior superior pancreaticoduodenal artery (large white arrow) and posterior inferior pancreaticoduodenal artery (small white arrow) form an arcade around the head of the pancreas.

(d) Anterior to the uncinate process is the jejunal vein (small white arrow) draining into the SMW (large white arrow).

Fig. 12—3. Arterial anatomy of the pancreas (see text).

(a) The gastroduodenal artery (arrow) is behind the pylorus (P). The posterior superior pancreaticoduodenal artery (PSA) accompanies the bile duct (BD). The dorsal pancreatic artery (arrowhead) gives off a branch medial to the pancreatic head. D = duodenum.

(b) The gastroepiploic artery (large white arrow) is branching out from the gastroduodenal artery (small white arrow),

(c) The anterior superior pancreaticoduodenal artery (large white arrow) and posterior inferior pancreaticoduodenal artery (small white arrow) form an arcade around the head of the pancreas.

(d) Anterior to the uncinate process is the jejunal vein (small white arrow) draining into the SMW (large white arrow).

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