Several clinical and autopsy studies have suggested that the pancreatic duct likely dilates with age in the absence of underlying pancreatic pathology. In one autopsy study of 112 patients without known pancreatic disease, 18 patients (16%) had pancreatic duct diameters greater than 4 mm. Interestingly, a significantly higher proportion of patients (40%) had dilated pancreatic side branches, which were typically seen in association with inspissated eosinophilic deposits in the side branches.¹ Hastier and colleagues compared pancreatograms obtained at endoscopic retrograde cholangiopancreatography (ERCP) from 105 subjects older than 70 years of age with those obtained from a control group of patients less than 50 years of age.² Subjects with pancreatic pathology were excluded from both cohorts. They found that mean main pancreatic duct diameter in the head of the pancreas was 2 mm wider (5.3 mm compared to 3.3 mm, p <0.05) in the older cohort and that 20% of the subjects in the elderly group had pancreatic duct diameters that were more than 2 standard deviations above normal. In a prospective endoscopic ultrasound (EUS) study of age-related changes in the pancreas, patients older than 60 years of age had wider pancreatic ducts in the head of the pancreas (median diameter in mm; interquartile range = 2.9 [2.2 to 3.5]) than did patients less than 40 years of age (2.0 [1.6 to 2.2]).³ Similarly, pancreatic duct diameters in the pancreatic body were greater in patients older than 60 years (1.8 [1.3 to 2.1]) compared to patients younger than 40 years (1.5 [1.2 to 2.0]) while the duct diameter in the tail of the pancreas did not differ significantly between these two groups.

Evaluation

Clinical

A patient with a dilated pancreatic duct may present with abdominal pain, acute or chronic pancreatitis, exocrine insufficiency, or a pancreatic duct leak, or may be completely asymptomatic. The most important aspect is the clinical setting (patient characteristics, symptoms, associated imaging features) in which the abnormality is found and thus a detailed history is imperative. Abdominal pain associated with pancreatic ductal dilation is thought to result from increased pressure within the duct as well as the associated parenchymal hypertension and localized ischemia and inflammation. If a dilated duct is found in a pain-free patient, the concern for an underlying obstructive neoplasm is substantially increased. This is particularly true in the setting of concomitant weight loss, a double-duct sign (biliary duct dilation in concert with pancreatic duct dilation), presence of pancreatic atrophy found on imaging studies, and other “red flag” symptoms such as new-onset or worsening diabetes mellitus and depression. Alternatively, if the patient has significant pain with pancreatic calcifications on imaging tests, a diagnosis of chronic pancreatitis with associated pancreatic duct distension with or without a downstream stricture is more likely. In this case, a prior history of recurrent bouts of acute pancreatitis is reassuring.

If the patient is truly asymptomatic it may influence the decision regarding further treatment or investigation. This is particularly true if the patient is of an advanced age or has significant comorbidities, wherein a potential endoscopic procedure or surgical resection may not affect the natural history of the disease or improve the length or quality of life. In contrast, since one third of patients with isolated pancreatic duct dilation without chronic pancreatitis are diagnosed with an underlying pancreatic malignancy, it is generally prudent to obtain further diagnostic information in the majority of patients.⁴

Laboratory Evaluation

Laboratory values can help to identify signs of pancreatic inflammation as well as exocrine insufficiency with associated fat malabsorption and steatorrhea. The presence of elevated serum tumor markers may raise the suspicion for malignant lesions, though their relative specificity and sensitivity can vary depending on cutoff values and comorbid conditions.

Serum amylase and lipase: These values can be elevated in the setting of pancreatitis, pancreatic cystic lesions, and pancreatic neoplasms. Amylase and lipase levels may also be increased in the absence of pancreatic disease in the setting of renal insufficiency, intestinal injury, or gastrointestinal ischemia. Nevertheless, a serum lipase greater than three times the upper limit of normal is a reliable diagnostic criterion for acute pancreatitis in the appropriate clinical setting. In patients with chronic pancreatitis, normal levels of amylase and lipase do not exclude a flare of acute pancreatitis. Persistent but mild elevations can be seen in chronic pancreatitis.

Fecal fat: Elevated levels of fecal fat imply an element of fat malabsorption, typically from exocrine pancreatic insufficiency. This can be tested in a qualitative manner as a one-time stool test. A timed quantitative 72-hour cumulative collection can be used as a screening or confirmatory test. The upper level of normal is a measurement of >7 g of fat per 24-hour period.

Fecal elastase-1 and chymotrypsin: The fecal elastase-1 test is used to measure the concentration of elastase-3B enzyme in the stool, a zymogen that is secreted by the pancreas. Levels in the stool of <200 µg/g of stool suggest exocrine pancreatic insufficiency.

Serum CA 19-9: CA 19-9 has limited utility as a screening test and is employed more effectively as a surveillance test for disease recurrence in those patients in whom levels are high prior to treatment. Serum CA 19-9 lacks specificity for diagnosis of pancreatic cancer and can be elevated in a variety of nonpancreatic cancers, including colon cancer, hepatoma, and gastric cancer, as well as in noncancerous disease states, including acute and chronic pancreatitis, choledocholithiasis with or without cholangitis, cirrhosis of the liver, and biliary obstruction of any cause.⁵ The presence of hyperbilirubinemia is particularly confounding in the interpretation of elevated serum CA 19-9 levels. In one retrospective study serum CA 19-9 was elevated in 61% (25 of 61) of subjects ultimately found to have obstructive jaundice from benign causes.⁶ The same study showed that normalization or a significant drop in CA 19-9 levels (to less than 90 U/mL) after biliary drainage was highly suggestive of a benign etiology. It is possible that alternative assays for CA 19-9 may improve specificity in the future⁷ but at the present time this marker should be considered adjunctive information in the particular setting where pancreatic ductal dilation is identified, as a markedly high level (>1000 U/mL) would argue for a malignant etiology. For a detailed discussion of the utility and limitations of CA 19-9 in the evaluation of patients with suspected pancreatic cancer, the reader is referred to two comprehensive reviews on the topic.^8,⁹