Pancreatic injuries and pancreaticoduodenectomy

Injuries to the pancreas remain uncommon, occurring in <1% of all adult traumas and 3.7% to 11% of abdominal trauma. Despite advances in modern trauma care, including damage control surgery and improved imaging techniques, injuries to the pancreas present a continuing challenge to the trauma surgeon for several reasons. First, the pancreas is relatively protected within the confines of the retroperitoneum, confounding the clinical detection of injury. Next, complications, related to physiologic functions, are also common following pancreatic injuries, occurring in 30% to 60% of these patients. Finally, the relative infrequency of these injuries has resulted in a lack of experience in both diagnosing and managing these injuries among practicing trauma surgeons. Consequently, morbidity and mortality rates associated with pancreatic injuries have changed little over the past three decades. The high complication and mortality rates associated with these injuries are primarily related to diagnostic delays and missed injuries. When identified early, the treatment of most pancreatic injuries is straightforward. It is the delayed recognition and treatment of these injuries that can result in devastating outcomes, with mortality rates ranging from 9% to 34%.

There are few well-documented historical accounts about the management of pancreatic injuries. The first documented case of pancreatic trauma was an autopsy report from St. Thomas Hospital in London in 1827 in which a patient struck by the wheel of a stagecoach suffered a complete pancreatic body transection. Over the next several decades, reports of pancreatic injuries were scattered. In 1903, only 45 cases of pancreatic trauma, 21 resulting from penetrating injuries and 24 from blunt trauma, could be identified. Mickulicz-Radecki noted that all 20 of the patients observed died and 18 of the 25 (72%) who were operated on survived. With these findings, he recommended a thorough exploration through a midline incision, suture control of hemostasis, and drainage—similar to modern approaches.

Complications following pancreatic injury were also historically described and have continued to be a problem throughout the years. In 1905, Korte reported the first case of a pancreatic fistula following an isolated pancreatic transection. The fistula closed spontaneously and the patient survived. Whipple first described pancreaticoduodenectomy in 1935 and later reported the associated complications of secondary hemorrhage, fistula formation, duodenal leaks, and peritonitis.

This chapter attempts to clarify the anatomic and physiologic basis for the concerns over injuries to the pancreas as well as elucidate specific diagnostic and therapeutic interventions following traumatic injuries to the pancreas with the goal of improving the notoriously poor outcomes associated with these injuries.

Anatomy

A complete understanding of pancreatic relational anatomy is essential for providing appropriate treatment and understanding the potential for associated injuries. The pancreas is about 15 to 20 cm in length, 3.1 cm wide, and 1 to 1.5 cm thick. The average mass is 90 g (ranging from 40 to 180 g). The inferior vena cava, aorta, left kidney, both renal veins, and right renal artery lie posterior to the pancreas. The head of the pancreas is nestled in the duodenal sweep, with the body crossing the spine and the tail resting within the hilum of the spleen. The splenic artery and vein can be found along the superior border of the pancreas. The superior mesenteric artery and vein reside just behind the neck of the pancreas and are enclosed posteriorly by the uncinate process, which can be absent or can almost completely encircle the mesenteric vessels.

The head of the pancreas is suspended from the liver by the hepatoduodenal ligament and is firmly fixed to the medial aspect of the second and third portions of the duodenum. A line extending from the portal vein superiorly to the superior mesenteric vein inferiorly marks the division between the head and the neck of the gland. The neck of the pancreas measures approximately 1.5 to 2 cm in length and lies at the level of the first lumbar vertebra. It overlies the superior mesenteric vessels and is fixed between them and the celiac trunk superiorly. The body of the pancreas is technically defined as that portion of the pancreas that lies to the left of the superior mesenteric vessels. There is no true anatomic division between the body and the tail, nor is there any imaginary dividing line as in the case of the head and neck.

The main pancreatic duct of Wirsung originates in the tail of the pancreas and typically traverses the entire length of the gland and joins the common bile duct before emptying into the duodenum. Throughout its course in the tail and body, the duct lies midway between the superior and inferior margins and slightly more posterior. The accessory duct of Santorini usually branches out from the pancreatic duct in the neck of the pancreas and empties separately into the duodenum. A significant number of anatomic variants exist and must be recognized. In 60% of individuals, the ducts open separately into the duodenum; in 30%, the duct of Wirsung carries the entire glandular secretion and the duct of Santorini ends blindly; and in 10%, the duct of Santorini carries the entire secretion of the gland and the duct of Wirsung is either small or absent. In all cases, the ducts lie anterior to the major pancreatic vessels. Regardless, surgeons dealing with pancreatic injuries should be well versed with these anatomic variants.

The arterial and venous blood supply of the pancreas is relatively constant. The arterial blood supply of the pancreas originates from both the celiac trunk and the superior mesenteric artery. The blood supply to the head of the pancreas appears to be the greatest, with less flow to the body and tail and the least to the neck. The veins, like the arteries, are found posterior to the ducts, lie superficial to the arteries, and parallel the arteries for the most part throughout their course. The venous drainage of the pancreas is to the portal, splenic, and superior mesenteric veins.

Physiology

The pancreas is a compound tubuloalveolar gland with both endocrine (insulin, glucagon, somatostatin) and exocrine (digestive enzyme precursors, bicarbonate) function. The endocrine cells are separated histologically into nests of cells known as the islets of Langerhans. There are three predominant subtypes of islet cells: alpha cells (produce glucagon), beta cells (produce insulin), and delta cells (produce somatostatin). Although these cells are distributed throughout the substance of the pancreas, the majority reside primarily within the tail. Consequently, it would seem that a distal pancreatectomy would be poorly tolerated in terms of endocrine function. However, it is well known that resection of more than 90% of the pancreas must occur before endocrine insufficiency develops, provided the remainder of the gland is normal. In fact, partial resection induces hypertrophy and increased activity of the residual islet cells. In animal studies, Dragstedt was the first to show that removal of 80% of the pancreas did not significantly alter carbohydrate and fat metabolism or the digestion and absorption of food, provided that the remaining gland is normal and that pancreatic secretions still have access to the upper digestive tract via the ductal system.

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