Anatomy - Cephalic pancreatoduodenectomy with Blumgart anastomosis and biliopancreatic separation (Merheim technique)

The pancreas is made of lobules and has a reddish-grey color, is 14–18 cm long and weighs 65–80 grams. Thus wedge -shaped organ is located at the level of the first and second lumbar vertebra and extends from the epigastric region to the left hypochondrium. Embryologically, the organ is in close relation with the organs and vessels of the upper abdomen.

The pancreas is invested by capsule-like connective and fatty tissue and is divided into three parts: Head, body and tail (caput, corpus and cauda). While the posterior aspect of the head rests on a somewhat coarser plate of connective tissue, the connection of the organ with the posterior connective tissue is otherwise mostly loose. Since it is a retroperitoneal organ, the anterior aspect of the gland is overlaid with peritoneum.

The gland is widest at the head, which nestles within the curve of the duodenum just to the right of the second lumbar vertebra. Both the anterior and posterior aspect of the duodenum may be overlaid to varying degrees by glandular tissue. The inferior (uncinate) process of the head reaches behind the superior mesenteric vein and sometimes even behind the accompanying artery. The notch in the uncinate process extending along the junction of the left half of the pancreatic head and the neck of the pancreas is known as the pancreatic notch (incisura pancreatis).

With a width of approx. 2 cm, the region of the pancreas at the level of the first lumbar vertebra constitutes the transition between the head and tail of the organ and is located craniad to the superior mesenteric vessels. From a surgical point of view, this is also known as the neck of the pancreas.

The elongated pancreatic body extends obliquely caudocephalad anterior to the first and second lumbar vertebra, protruding anteriorly into the lesser sac and arcing toward the splenic hilum; anatomically, the body of the pancreas is not clearly delimited from the tail. The aorta, inferior vena cava, and superior mesenteric artery and vein are posterior to the pancreas and adjacent to the spinal column.
The pancreatic tail constitutes the tapered continuation of the body and extends to the splenorenal ligament or may even enter it.

The pancreatic anlage may take various shapes – oblique, S-shaped, transverse, and L-shaped. Horseshoe and inverted V-variants have also been described. The transition between these variant shapes is fluid.

Pancreatic topography comprises the following relations with neighboring organs and retroperitoneal pathways:

• Anteriad, the lesser sac and posterior aspect of the stomach
• To the right, a close relation between the head of the pancreas and the curve of the duodenum
• To the left, a close relation with the splenic hilum
• At the level of the head, the posterior aspect of the pancreas touches the portal vein, superior mesenteric artery and vein, and common bile duct., while at the level of the body it touches the splenic artery and vein, inferior mesenteric vein, and abdominal aorta. At the level of the tail the posterior aspect is in contact with the left kidney.

The pancreatic duct is approximately 2 mm wide and traverses the organ in its longitudinal direction close to the posterior aspect. Along its path, numerous short glandular ducts terminate in the pancreatic duct at right angles.In about 77% of cases, the duct together with the common bile duct terminates in the major duodenal papilla at the posterior wall of the descending duodenum; in the remaining cases, both ducts terminate separately but close together. Quite often, the accessory pancreatic duct is only rudimentary or completely absent. If present, it terminates at the minor duodenal papilla.