Chapter 45. The Exocrine Pancreas

The pancreas is situated retroperitoneally in the upper abdomen. It is divided into the head, which lies in the curve of the duodenum; the body, which is situated horizontally in the upper retroperitoneum; and the tail, which extends leftward to the hilum of the spleen.

The pancreas has two functional components: exocrine and endocrine.

1.  The exocrine pancreas contains acini that secrete a variety of enzymes into the pancreatic ducts. The main pancreatic duct opens at the duodenal papilla and in 70% of patients joins with the terminal common bile duct at the ampulla of Vater. An accessory (minor) pancreatic duct usually opens independently into the duodenum proximal to the papilla.

2.  The endocrine pancreas is composed of the islets of Langerhans, distributed throughout the pancreas with a maximum density in the tail and containing several different hormone-producing cell types (Chapter 46: The Endocrine Pancreas (Islets of Langerhans)).

Pain

Acute or chronic inflammation of the pancreas is associated with pain, often severe and constant, situated deep in the epigastric region and frequently radiating to the back.

Failure of Exocrine Secretion

Failure of exocrine pancreatic function leads to maldigestion of fat (lack of lipase), which results in steatorrhea. Lack of pancreatic proteolytic enzymes, although important in protein digestion, can be compensated for by gastric and intestinal proteases.

Changes in Pancreatic Hormone Production

See Chapter 46: The Endocrine Pancreas (Islets of Langerhans).

Assessment of Structure

The pancreas is not easily evaluated clinically because it becomes palpable only when it contains a large mass. Plain abdominal x-ray is useful for demonstration of pancreatic calcification, which is a feature of chronic pancreatitis. Ultrasonography and computerized tomography permit visualization of the pancreas and detection of mass lesions. It is also possible to cannulate the pancreatic duct via an endoscope in the duodenum and inject dye to permit evaluation of the duct system (endoscopic retrograde cholangiopancreatography (ERCP)).

Percutaneous fine-needle aspiration biopsy under radiologic control is a safe method of obtaining cytologic material for diagnosis of mass lesions of the pancreas.

Assessment of Function

Elevated serum levels of amylase and lipase provide evidence of necrosis of pancreatic cells, as in acute pancreatitis. It is more difficult to test the adequacy of secretion of enzymes by the pancreas into the duodenum, and failure of exocrine secretion is usually deduced by the occurrence of maldigestion (steatorrhea). Assays for hormones secreted by the pancreatic islets are useful in diseases of the endocrine pancreas.

Ectopic Pancreatic Tissue

Ectopic pancreatic tissue is present in about 2% of persons, usually discovered as an incidental finding at autopsy. In descending order of frequency, ectopic pancreas is found in the stomach, duodenum, jejunum, and ...