Chapter 7 Acute Pancreatitis
Incidence
Acute pancreatitis is common, with an incidence of 10 to 50 cases per 100,000 person-years. Although reports suggest a three-fold increase in incidence since the 1970s, this may reflect an increase in diagnosis rather than a true increase in disease burden.
Patients with HIV have a higher incidence of acute pancreatitis. Acute pancreatitis is also more common in women, who usually develop gallstone pancreatitis. Men are more likely to have alcohol-induced pancreatitis. Gallstone disease and alcohol use account for approximately 70% to 80% of cases of pancreatitis. Ten percent of cases are due to other diagnosable factors, and the remaining 10% are “idiopathic.” (See Table 7-1.)
Table 7-1 Causes of Acute Pancreatitis
| Cause | Useful tests |
|---|---|
| Gallstones | RUQ ultrasound, ALT > 3 times normal |
| Alcohol use | Medical history, lipase:amylase ratio > 2 |
| Hypertriglyceridemia | Lipid profile on admission |
| Hypercalcemia | Calcium level on admission |
| Biliary sludge, microlithiasis | EUS, biliary crystal analysis |
| Medications (see Box 7-1) | Medical history |
| Infections | Signs and symptoms consistent with infectious etiology |
| Post-ERCP | Medical history, amylase, and lipase > 5 times normal 4 hr after procedure |
| Trauma or postoperative | |
|---|---|
| Pancreas divisum | CT, MRCP, EUS, ERCP |
| Choledochal cyst | MRCP, ERCP |
| Duodenal disease: Crohn’s disease, ulcers | EGD with possible biopsies |
| Ischemia: Vasculitis, shock | |
| Genetic diseases | |
|---|---|
| Hereditary pancreatitis | Genetic testing for cationic trypsinogen mutation |
| Cystic fibrosis | Genetic testing |
| Autoimmune pancreatitis | IgG4 level |
RUQ = right upper quadrant, ALT = alanine aminotransferase, EUS = endoscopic ultrasound, MRCP = magnetic resonance cholangiopancreatography, ERCP = endoscopic retrograde cholangiopancreatography, EGD = esophagogastroduodenoscopy.
Morbidity and Mortality
Acute pancreatitis spontaneously resolves in 75% to 85% of cases. The remaining cases tend to follow a more severe course, with both local and systemic complications. Mortality within the first two weeks is due to the systemic inflammatory response syndrome and organ failure. Mortality after the first 2 weeks is usually due to infectious complications and sepsis.
The overall mortality for acute pancreatitis is approximately 10%, but this number represents a heterogeneous group of patients. Interstitial pancreatitis has a 1.5% mortality, pancreatitis complicated by sterile necrosis has a 12% to 14% mortality, and pancreatitis with infected necrosis has a mortality rate as high as 30%.
Patients with their first episode of acute pancreatitis have a higher likelihood of morbidity and mortality. Obesity is associated with a worse prognosis, as more peripancreatic fat leads to greater risk and degree of necrosis. In fact, 66% of obese patients have severe pancreatitis (with 36% mortality) compared with 6% of non-obese patients.
Roughly, 80% of deaths from pancreatitis are due to complications, with 60% of deaths occurring in the first week, usually due to systemic complications (primarily pulmonary), and 40% of deaths occurring after the first week, primarily due to sepsis. Infected necrosis causes death later in the disease course.
Etiology
We will briefly discuss a few of the more common causes of acute pancreatitis. Please refer to Table 7-1 for a listing of etiologies of acute pancreatitis.
Gallstones
Gallstone pancreatitis accounts for 35% of acute pancreatitis. Only 3% to 7% of patients with gallstones develop acute pancreatitis. The risk of pancreatitis is inversely proportional to stone size, with stones smaller than 5 mm having the highest risk. Although the risk of developing gallstone pancreatitis is higher in men with cholelithiasis, gallstone pancreatitis is more common in women because more women have gallstones.
Patients often present with a history of biliary colic prior to the development of pancreatitis. Alanine aminotransferase (ALT) greater than three times the upper limit of normal in a patient with pancreatitis is highly suggestive of gallstone pancreatitis (ALT > 150 IU/L has a 95% positive predictive value for gallstone pancreatitis).
Treatment is cholecystectomy, preferably during the same hospitalization.
Alcohol
Alcohol-induced pancreatitis is more common in men and occurs in 10% of persons who are chronic alcoholics. Most cases of alcohol-induced pancreatitis occur in patients with chronic pancreatitis.
Patients with alcohol-induced pancreatitis should be advised to abstain from alcohol intake.
Hypertriglyceridemia
Hypertriglyceridemia causes less than 4% of cases of acute pancreatitis. Triglyceride levels greater than 1000 mg/dL are required to induce disease. The most common types of familial hyperlipidemia associated with acute pancreatitis are Type V (40%), Type I (35%), and Type II (15%). In adults, such high triglyceride levels are usually caused by a combination of an inherited familial hyperlipidemia syndrome and an acquired etiology of hypertriglyceridemia, such as obesity, diabetes mellitus, or use of medications.
The three common presentations of hypertriglyceridemia-induced pancreatitis are:
Trigylceride levels should be obtained on admission. If triglyceride levels are checked after the patient has been fasting for a period of time, the results may be falsely low. Amylase levels may be falsely normal in the presence of hypertriglyceridemia because the high triglyceride levels interfere with the amylase assay.
Hypercalcemia
Hypercalcemia is an uncommon cause of acute pancreatitis. The association of hyperparathyroidism with pancreatitis is debatable. Less than 0.5% of cases of acute pancreatitis are due to hyperparathyroidism, and fewer than 1.5% of patients with hyperparathyroidism develop acute pancreatitis.
Medications
Medication-induced pancreatitis (see Box 7-1) accounts for 1.4% of cases of pancreatitis, and may be due to either dose-dependent effects or idiosyncratic reactions.
