Injuries to the Duodenum and Pancreas

Benjamin Braslow

George Joseph Koenig Jr.

PANCREATIC INJURIES

In comparison to injury to other visceral organs from both blunt and penetrating trauma, injury to the pancreas is far less common probably secondary to its retroperitoneal location. Likewise, isolated pancreatic injury with major duct disruption is exceptionally rare and is associated with injury to other organs, most commonly liver, stomach, spleen, or colon, in up to 98% of cases.¹ Pancreatic injury has been reported to occur in only 3% to 12% of patients presenting with abdominal injuries.¹,² Two thirds of these injuries are penetrating in nature with gunshot wounds being most common followed by stabbings.³ In fact, pancreatic injury has been reported to occur in 1.1% of all patients presenting with penetrating torso traumas, as opposed to 0.2% of all blunt trauma patients.⁴ Regarding blunt pancreatic injury, motor vehicle accidents are by far the most common causative mechanism, being reported in approximately 65% of such patients. Most pancreatic traumas are observed in unrestrained drivers secondary to direct abdominal impact with the steering wheel or by the handle bars during a motorbike crash.⁴ Although proved to save lives by preventing ejection from the vehicle, seat belts are also often implicated in abdominal visceral trauma during a crash. The so-called seat belt syndrome is characterized by the presence of abdominal wall contusions or abrasions associated with lumbar spine compression fracture (most commonly at L1 or L2 secondary to hyperflexion) and visceral injury. Here the organ is compressed against the vertebral body by the force of the belt against the abdominal wall.⁵ Airbag deployment during a crash does not entirely rule out the possibility of such injury.⁶

Despite the infrequent nature of pancreatic injuries, when present, the associated morbidity is exceptionally high often because identification is a diagnostic challenge and delays in diagnosis are common.

Pancreatic Anatomy and Physiology

The pancreas lies transversely across the retroperitoneum at the level of the pylorus and crosses the anterior body of the first and second lumbar vertebrae. It measures roughly 15 to 20 cm in length, 3 cm in width, and up to 1.5 cm in thickness and weighs an average of 90 g.⁷ The head of the pancreas is nestled within the concavity of the second and third portion of the duodenum with which it shares its blood supply through the pancreaticoduodenal arcades. The body crosses the spine obliquely headed in a superior direction toward the left shoulder. The tail ends in close proximity to the splenic hilum. The splenic artery arises from the celiac plexus and takes a tortuous course along the upper border of the pancreas whereas the splenic vein courses medially behind the pancreas just above its inferior edge. Both vessels give off multiple branches into the body and tail of the pancreas that must be ligated in spleen-sparing procedures. The superior mesenteric vein and artery lie just behind the neck of
the pancreas and are partially enclosed posteriorly by an extension of the pancreatic head known as the uncinate process.

The main pancreatic duct of Wirsung usually traverses the entire length of the pancreas just above the midline of the gland and opens into the posterior medial wall of the second portion of the duodenum, at the ampulla of Vater along with the common bile duct. The accessory duct of Santorini usually arises from the main pancreatic duct in the neck of the pancreas and empties into the duodenum proximal to the ampulla of Vater. Pancreatic ductal anatomy is highly variable and intraoperative pancreatography is often necessary to determine the status of the pancreatic duct following injury.

At the microscopic level, the pancreas is organized into exocrine and endocrine units called acini and islets of Langerhans, respectively. The acini and related ductal system produce up to 2 L per day of pancreatic juice, which is not only rich in digestive enzymes necessary for the breakdown of proteins (i.e., trypsinogen, chymotrypsinogen, and procarboxypolypeptidase), carbohydrates (amylase), and fats (lipase) but also contains large quantities of bicarbonate necessary to neutralize the acid chyme emptied from the stomach into the duodenum. The islets of Langerhans are distributed throughout the pancreas but seem to be most concentrated in the pancreatic tail area. These islets are composed primarily of α, β, δ, and F or pancreatic polypeptide (PP) cells which produce glucagon, insulin, somatostatin and PP, respectively with β cells being the most prevalent (60%) cell type. It has been shown that excision of >90% of the pancreas substance is required to produce a state of endocrine deficiency, if the pancreas is otherwise normal. This is likely a result of islet hypertrophy and increased activity following partial resection. Remarkably, even after removal of 90% to 95% of the pancreas following trauma, digestion and absorption of food may be unimpaired.

Diagnosis

Outcome following pancreatic injury is directly linked to the accurate and timely diagnosis of major pancreatic duct injury.⁸,⁹ Patients with isolated pancreatic injuries often present with vague or totally absent abdominal complaints and frequently lack any physical signs.²,¹⁰ The retroperitoneal position of the pancreas accounts for most of the delay in symptoms. Also, most of the caustic pancreatic enzymes released at the site of injury are in their inactivated form and surrounding tissue destruction is limited. Usually when a patient does have symptoms, they may be related to coexisting visceral or boney injuries. A high index of suspicion is reasonable in any patient who has sustained a direct high-energy blow to the epigastrium. For adults, this is most often a result of chest wall impact with the steering wheel of a car during a crash, whereas children often suffer a spearing type insult from the handlebars of a bicycle. For patients with blunt trauma, the presence of soft tissue contusion or abrasion in the upper abdomen or epigastric pain out of proportion to the abdominal examination should prompt suspicion of retroperitoneal injury. If the patient has a clear indication for laparotomy, and the suspicion of pancreatic injury is present, preoperative evaluation directed at identifying a possible pancreatic injury is usually not indicated and would lead to unwarranted delays in definitive patient care. Here, the diagnosis of pancreatic injury should be made intraoperatively after hemorrhage control and control of abdominal contamination has been achieved. Without a clear indication for exploratory laparotomy, the physician has several diagnostic modalities available to help in identifying injury to the pancreas.

Despite the fact that the highest concentration of amylase in the human body is in the pancreas, hyperamylasemia is not a reliable indicator of pancreatic trauma but its presence should raise the index of suspicion for pancreatic injury and warrant further evaluation.¹¹,¹² Other sources of hyperamylasemia following trauma include salivary gland injury, bowel injury, and even brain injury although the etiology for this is not clear.¹³ The spectrum of the sensitivity and specificity of the serum amylase assay in multiple studies has been quite varied; however, the accuracy of the assay seems to be time dependant. Takishima et al. found that when the blood specimen was drawn later than 3 hours after injury, the accuracy of the test was significantly increased.¹⁴ On a more useful note, after blunt trauma the negative predictive value of a normal serum amylase level has been shown to be approximately 95%.

Diagnostic peritoneal lavage (DPL), although useful in the abdominal investigation of the unexaminable, unstable blunt trauma patient, has not been proved to be useful in diagnosing significant injury to the pancreas. The retroperitoneal location of the pancreas renders DPL inaccurate in the prediction of isolated pancreatic injury. Also the estimation of amylase levels in the DPL fluid, even if >20 IU/L, is unreliable leading to both false-positive and false-negative results.¹⁵

The central retroperitoneal position of the pancreas also renders ultrasonographic evaluation of the gland following injury very difficult and inaccurate. The large amount of air-containing bowel overlying the pancreas interferes with the transmission of ultrasonographic waves and obscures the view generated by this modality.

To date, contrast-enhanced computed tomography (CT) is generally accepted as the imaging modality of choice for evaluating the retroperitoneum in a hemodynamically stable patient following trauma. Sensitivities and specificities between 70% and 80% have been reported with factors including the experience of the interpreter, the quality of the scanner, and the time elapsed since injury all playing an important role.¹⁶ Characteristic CT findings associated with pancreatic injury include (a) fracture of the pancreas with or without separation of the fractured
fragments, (b) enlargement of the pancreas or presence of hematoma in or around the gland, (c) fluid separating the splenic vein and pancreas, (d) increased attenuation of the peripancreatic fatty tissue, (e) thickening of the anterior renal fascia, (f) fluid accumulation in the lesser sac, and (g) retroperitoneal fluid or hematoma. Often these findings are subtle and rarely are they all present at a single scan. The sensitivity of CT increases with time as the injury evolves.¹⁷ This accounts for the false-negative CT scans reported in as many as 30% of patients with significant pancreatic injuries and indicates the utility of repeat scans if symptoms persist.¹⁷ Bradley et al. found CT to be sensitive in approximately 72% of cases of pancreatic trauma but noted that CT did not accurately estimate the grade of injury and showed only a 43% sensitivity for the prediction of ductal injury.¹⁸

Endoscopic retrograde cholangiopancreatography (ERCP) is a very accurate method of defining pancreatic duct anatomy and integrity, especially in patients with blunt abdominal trauma, but has no role in the acute evaluation of hemodynamically unstable patients.¹⁹ This modality offers both the ability to diagnose and occasionally treat pancreatic duct disruption by stent placement either across the zone of injury or at the ampulla to decrease the pressure within the ducts and allow for healing of ductal lesions.²⁰,²¹,²² ERCP can preclude laparotomy in stable patients with suspected pancreatic injury by demonstrating an intact pancreatic duct or a stentable lesion in the absence of peritonitis. It is an invasive procedure associated with limited but real morbidity including pancreatitis, hemorrhage, and gastrointestinal (GI) perforation in up to 5% of patients. Although limited, there is occasionally a role for intraoperative ERCP to evaluate the pancreatic duct when injury determination is equivocal. This is only an option in a hemodynamically stable patient with limited other injuries. Often coordinating an ERCP during an emergency surgery is difficult and limited by the timely availability of the appropriate personnel and equipment.²³ Intraoperative ERCP can eliminate morbidity associated with duodenotomy or distal pancreatectomy in order to gain access to the pancreatic duct for pancreatography.²⁴

Magnetic resonance imaging, more specifically, magnetic resonance cholangiopancreatography (MRCP), is emerging as a valuable modality for the evaluation of the pancreatic duct following suspected injury. Several recent studies have touted its accuracy and low morbidity profile.²⁵,²⁶,²⁷ Unlike CT technology, MRCP depicts the pancreatic duct and biliary tract as high signal intensity or bright structures without the use of contrast material. It has been shown to be diagnostic in 95% to 99% of cases.²⁸ In addition to delineating the pancreatic duct, MRCP detects pancreas-specific complications such as pseudocysts that may not opacify at ERCP. Because MRCP is performed without instrumentation, it avoids the above-mentioned risks of ERCP but does not offer the possibility of being a therapeutic modality.

Intraoperative Evaluation

The presence of an upper abdominal central retroperitoneal hematoma, edema around the pancreatic gland and the lesser sac, and retroperitoneal bile staining and/or the presence of saponification of the retroperitoneal fat mandate thorough pancreatic inspection. More simply stated, if there are any of the “3 Bs” (bile, blood, and bubbles) present around the peripancreatic area, the local structures should be meticulously explored.²⁹ Inspection of the pancreas requires complete exposure of the gland. Entering the lesser sac through an opening in the gastrocolic omentum allows visualization of the anterior surface of the body and tail of the pancreas to be explored. The stomach is retracted upward while the transverse colon is retracted in a caudal direction. Frequently, there are some adhesions between the posterior wall of the stomach and the anterior surface of the pancreas that must be lysed. Next, a generous Kocher maneuver is performed including mobilization of the hepatic flexure of the colon. This provides adequate visualization of the pancreatic head and the uncinate process both anteriorly and posteriorly and allows for bimanual examination of the head and neck of the gland. Injury to the tail requires mobilization of the spleen and left colon to allow medial reflection of the pancreas by creating a plane between the kidney and the pancreas with blunt finger dissection. Division of the ligament of Treitz and reflection of the fourth portion of the duodenum can enhance exposure of the inferior aspect of the pancreas.

Most pancreatic duct injuries, regardless of mechanism, can be diagnosed through careful inspection of the injury tract following adequate exposure. With most penetrating wounds to the periphery of the gland, the pancreas can be inspected directly and the likelihood of duct disruption ruled out. With penetrating wounds to the head, neck, or central portion of the pancreas, however, further evaluation is often required. Occasionally, intravenous (IV) injection of 1 to 2 µg of cholecystokinin pancreozymin (CCK-PZ) may stimulate pancreatic secretions enough to allow for visualization of pancreatic duct leakage from an otherwise occult ductal injury. Several options exist for intraoperative imaging of the pancreatic duct. These include intraoperative ERCP, direct open ampullary cannulation through lateral duodenostomy, needle cholangiopancreatography, or antegrade pancreatography through transaction of the tail of the pancreas and distal ductal cannulation. Remember that in unstable (hypotensive, cold, coagulopathic, and acidotic) patients for whom damage control principles are indicated, prolonged techniques of evaluating the pancreatic duct integrity at the initial surgery are not appropriate. Here the peripancreatic region is packed and widely drained. Postoperative duct interrogation is performed following physiologic resuscitation. For stable patients, as stated in the preceding text, intraoperative ERCP is often logistically too difficult to organize during an emergency surgery especially at night in most hospitals. Much has
been written about duodenotomy and direct ampullary cannulation or transaction of the tail of the pancreas and distal duct cannulation in the past. These techniques are very invasive, requiring iatrogenic injury to an otherwise uninjured section of the bowel or pancreas and have largely been abandoned by most surgeons as a consequence of advances in less invasive perioperative imaging techniques such as ERCP and MRCP. Needle cholecystocholangiopancreatography remains a useful intraoperative adjunct in the evaluation of the injured pancreatic duct. This technique involves cannulating the gallbladder with an 18-gauge angiocatheter and injecting 30 to 75 mL of water-soluble contrast material under fluoroscopic guidance. In a recent study, this technique visualized the pancreatic duct in 64% of patients.³⁰ The administration of IV morphine, which promotes contracture of the sphincter of Oddi, may enhance the likelihood of pancreatic duct visualization. If the gallbladder is surgically absent then the common bile duct can be directly cannulated using a short “butterfly” needle for injection. Some operative dissection of the hepatoduodenal ligament is usually required here to expose the duct and a smaller caliber needle is necessary to minimize ductal trauma and limit leakage once the needle is removed. This can limit contrast flow and decrease the accuracy of the study.

TABLE 1 AMERICAN ASSOCIATION FOR THE SURGERY OF TRAUMA (AAST) GRADING OF PANCREAS INJURY

Pancreas Injury Scale
Grade^a	Type of Injury	Description of Injury	AIS-90 Score Score
I	Hematoma	Minor contusion without duct injury	2
	Laceration	Superficial injury without duct injury	2
II	Hematoma	Major contusion without duct injury or tissue loss	2
	Laceration	Major laceration without duct injury or tissue loss	3
III	Laceration	Distal transection or parenchymal injury with duct injury	3
IV	Laceration	Proximal transection or parenchymal injury with probable duct injury (not involving ampulla)^b	4
V	Laceration	Massive disruption of pancreatic head	5
^aAdvance one grade for multiple injuries up to grade III. ^bProximal pancreas is to the patient’s right of the superior mesenteric vein.
AIS, Abbreviated Injury Scale.

Classification of Pancreatic Injuries

Classification of pancreatic injuries is based on the status of the pancreatic duct and the site of the injury relative to the neck of the pancreas or the superior mesenteric vein. Currently, the system devised by the American Association for the Surgery of Trauma (AAST) (see Table 1) is most widely used.³¹ Management strategies for pancreatic trauma vary greatly and are guided by the grade of pancreatic injury and the presence of associated injuries.

Operative Management

Grades I and II Pancreatic Injuries

Contusions and lacerations without duct injury are treated with hemostasis and adequate external drainage.³²,³³,³⁴ Approximately 75% of all pancreatic injuries fall into these two categories. Closing the pancreatic capsule is ill advised as this might lead to pseudocyst formation whereas a controlled pancreatic fistula is usually self-limiting. Soft closed suction drains (i.e., 10 F JacksonPratt) are preferred over Penrose drains or sump drains (Davol) because they provide more complete removal of secretions, offering decreased intra-abdominal abscess formation, fewer infectious complications, and less skin excoriation at the drain exit site.³⁵ Duration of drainage remains a matter of controversy. Most authors recommend drainage until the patient is tolerating an oral diet or gastric feeds and the concentration of amylase in the effluent is equal to or less than that of serum. Others advocate earlier drain removal if output is minimal or ceases outright before a feeding challenge.³⁶

Grade III Pancreatic Injuries

Distal transection or distal parenchymal injury with duct disruption are best treated by distal pancreatectomy and drainage.¹⁰,³⁵,³⁷,³⁸,³⁹,⁴⁰ Following mobilization of the distal pancreas, a large (4.8 mm) TA-55 stapler can be used to divide the gland or some surgeons prefer to ligate the duct individually and place full thickness nonabsorbable mattress sutures through the cut parenchyma (anterior capsule to posterior capsule) to minimize leakage. A small omental patch may be used to buttress the cut surface of
the pancreas and a closed suction drain placed nearby. Placement of fibrin sealant over the cut surface of the gland might add some additional leak protection,⁴¹ but not much has been written in the trauma literature to confirm its efficacy. If there is any question regarding the integrity of the more proximal duct, intraoperative pancreatography can be performed through the open lumen of the proximal duct. However, locating the aperture is not always an easy task especially if a stapling device is used to transect the gland.

Concerns for the development of overwhelming postsplenectomy infection (OPSI) and the potential for left subphrenic abscess have prompted several authors to recommend splenic preservation during distal pancreatectomy.³⁹,⁴²,⁴³,⁴⁴,⁴⁵,⁴⁶ This is only considered an option in the traumatized patient provided the spleen is not severely injured and the patient’s condition is stable. This procedure requires complete mobilization of the distal pancreas and spleen. There are on average 22 tributaries of the splenic vein and 7 branches of the splenic artery that must be ligated to separate the structures.⁴⁷ This maneuver has been shown to increase operative times by approximately 1 hour (37 to 80 minutes).⁴⁵ Meticulous technique is mandated to prevent injury to the splenic hilum and thrombosis of the splenic vein.

Procedures associated with resection of >80% of the pancreatic tissue can be associated with a risk of endocrine or exocrine pancreatic insufficiency.⁴⁸ Even resection of all pancreatic tissue left of the superior mesenteric vein, or roughly left of the spine, leaves roughly 45% to 50% of the gland in situ,⁴⁹ and safely avoids pancreatic insufficiency.⁵⁰

Grade IV Pancreatic Injuries

Proximal transection or parenchymal injury to the pancreatic head with probable duct disruption can be the most difficult pancreatic injuries to manage. More often then not, injuries to this portion of the pancreas are associated with injuries to adjacent structures such as the duodenum and great vessels and are therefore associated with very high morbidity and mortality rates.¹⁰ Once bleeding and local contamination are controlled, defining the anatomy of the pancreatic duct becomes paramount. If the patient is unstable, damage control principles should prevail. The pancreatic bed is packed and drained widely and ductal interrogation is delayed. For the stable patient, local exploration is initially performed to evaluate the integrity of the duct. If after careful inspection of the gland there is still a question of ductal injury, more extensive intraoperative diagnostic procedures can be attempted (see preceding section on interoperative assessment). Generally there is a trend toward a more conservative approach with proximal pancreatic injuries, including wide external drainage and limited use of pancreaticoenteric anastomosis even in the presence of injury to the main pancreatic duct. The morbidity associated with proximal pancreatic resection is high. Some authors have concluded that the morbidity associated with a moderately high rate of fistula formation is more easily managed than the potential early and late complications of major proximal pancreatic resection.⁴⁰ Nevertheless, in the presence of proximal pancreatic ductal disruption without injury to the ampulla or duodenum (an albeit rare scenario) two operative options exist. The first option is extended distal pancreatectomy, resulting in subtotal gland removal. Here, the proximal residual gland drains into the duodenum in a normal manner. If, however, by this approach a >90% distal pancreatectomy ensues, endocrine and exocrine pancreatic insufficiency is bound to develop. Alternatively, preservation of the distal pancreas with a Roux-en-Y jejunal anastamosis to the distal pancreatic stump has been proposed.⁵¹,⁵² This technique involves division of the pancreas at the site of injury, debridement of injured retained parenchyma, closure of the proximal duct and cut edge of proximal parenchyma, and anastamosis of the open end of the distal pancreas to the Roux jejunal limb. The benefits of this technique are, however, debatable as it has been demonstrated that obstructive fibrotic lesions often develop in the preserved distal pancreatic segment, which results in gradual loss of its endocrine and exocrine function.⁵³

Historically, in cases of incomplete pancreatic parenchymal transection, surgeons have tried end-to-side jejunopancreatic anastamosis. This technique is no longer recommended as anastomotic failure rates were extremely high as were mortality rates.⁵⁴ Often the extent of parenchymal injury is not fully appreciated at the initial inspection and debridement and progressive destruction compromises the suture line of the anastamosis.⁵⁵

Grade V Pancreatic Injuries

Massive disruption of pancreatic head or combined pancreatic-duodenal injuries are discussed in the latter portion of this chapter.

Morbidity Associated with Pancreatic Injury

Morbidity after pancreatic trauma is high, ranging between 20% and 65% in several published series.³⁸,⁵⁶,⁵⁷,⁵⁸ It is mainly influenced by the grade on the AAST scale of the injury and the presence and number of associated intra-abdominal injuries.³⁶ The most common of these complications are pancreatic fistula, pancreatic pseudocysts, pancreatitis, hemorrhage, intra-abdominal abscesses, wound complications, and pancreatic exocrine and endocrine insufficiency.³,⁴,¹⁰,¹⁸ Fistula and pseudocysts formation are dependent on the presence of pancreatic duct injury while septic complications seem related to the presence of concomitant hollow viscus injuries, particularly colonic injuries.²,¹⁸ Although almost all pancreas-related posttraumatic complications are treatable or self-limiting, very often they could have been completely avoided by a more accurate and timely assessment of whether the pancreatic duct was damaged.⁹,⁵⁸,⁵⁹,⁶⁰

Only gold members can continue reading. Log In or Register to continue