Although serum amylase levels are used in the diagnosis of traumatic injury of the pancreas, recent studies have questioned the value of this determination in cases of acute injury. Factors such as the type of pancreatic injury and the interval between the time of the injury and amylase determination might have an influence on serum amylase levels. Takishima and associates evaluated the significance and limitations of serum amylase levels in the diagnosis of blunt pancreatic injury in 73 patients with pancreatic injuries caused by penetrating abdominal trauma.
The patients ranged in age from three to 68 years. Associated intra-abdominal injuries were present in 47 of the 73 patients (64.4 percent). The type of pancreatic injury was identified by computed tomography, endoscopic retrograde pancreatography or gross findings at laparotomy. Type I injury (contusion) was found in 35 cases (47.9 percent); type II injury (laceration) was present in 10 cases (13.7 percent) and type III injury (ductal injury) was documented in 28 cases (38.4 percent). Serum amylase levels were determined on admission in all of the patients.
The serum amylase level was already elevated at the time of admission in 61 of the 73 patients (83.6 percent). Of the 50 patients admitted within three hours after trauma, 38 patients (76 percent) had elevated serum amylase levels at the time of admission. All of the 23 patients admitted more than three hours after trauma had elevated serum amylase levels. The serum amylase level in patients with type III injury was approximately twice that in patients with type I or type II injury. Patients with type I or type III injury who were admitted more than three hours after they sustained trauma had significantly higher serum amylase levels than those admitted within three hours of sustaining trauma.
Regulation of the serum amylase level is multifactorial, and elevated levels can develop in association with decreased renal clearance (e.g., chronic renal failure, macroamylasemia), perforation of the abdominal hollow viscus and pancreatitis. In this study, the interval between injury and serum amylase determination appeared to be the most important factor influencing serum amylase levels in patients with blunt injury to the pancreas. The longest time during which the serum amylase level remains in the normal range might be a three-hour period following trauma (see the accompanying table)
The authors conclude that a normal serum amylase level taken within three hours after blunt abdominal trauma does not eliminate the possibility of pancreatic injury. However, a serum amylase determination more than three hours after trauma may be useful in detecting pancreatic injury.