Why pancreas is known as both endocrine and exocrine?

Pancreas Imaging

The pancreas is an abdominal organ possessing both endocrine and exocrine functions. It produces a variety of hormones that mostly pertain to regulating blood sugar levels. As an exocrine gland, it secretes pancreatic fluid that contains bicarbonate and digestive enzymes. Commonly, a few broad categories of diseases affect the pancreas that can be characterized on imaging: pancreatitis, pancreatic insufficiency, cystic lesions of the pancreas, and pancreatic tumors.

Pancreatitis is a generalized inflammation of the pancreas due to the activation of digestive enzymes produced by the pancreas while still inside the organ. Acutely, this can result from gallstones, alcohol misuse, or hypertriglyceridemia. Gallstones are the etiology of the majority of acute pancreatitis cases, 40 to 70%, while alcohol misuse accounts for 25 to 35%. Pancreatitis typically presents as an acute onset of epigastric pain that may radiate through to the back. Nausea and vomiting frequently accompany abdominal pain. The revised Atlanta classification separates acute pancreatitis into two subtypes: interstitial edematous pancreatitis and necrotizing pancreatitis. The severity further classifies acute pancreatitis into mild, moderately severe, or severe, based on the absence of organ failure, the presence of transient organ failure, or persistent organ failure, respectively. The mortality rate from acute pancreatitis is approximately 5%, while those with necrotizing pancreatitis see a higher rate at 17%. Chronic pancreatitis can occur in patients with alcohol use disorder, in which scarring of the gland prevents it from functioning properly.

Pancreatic insufficiency results when the pancreas is unable to produce enough digestive enzymes to break down food in the digestive tract. This condition is typically a deficiency in the exocrine function of the gland that can be caused by a variety of disease processes, most commonly cystic fibrosis in children and chronic pancreatitis in adults.

Pancreatic exocrine cancer is one of the leading causes of cancer-related deaths in the United States. It also ranks among the most lethal cancers, with a one-year survival rate of 20% and a five-year survival rate of only 5%. The lethality is mostly due to the insidious onset of the malignancy, with symptoms (e.g., jaundice, weight loss, and vague subacute epigastric pain) not presenting until late in the course of illness. Frequently, at the time of diagnosis, the lesion is inoperable due to extension into nearby structures. Over one-third of the tumors are Stage IV upon identification, and less than 20% of these cancers are candidates for surgical resection. The most common malignancy is ductal adenocarcinoma involving the exocrine glands; most of these tumors get discovered in the head of the pancreas.

Pancreatic neuroendocrine tumors (NETs) are malignancies that form in the endocrine tissue of the pancreas. Also known as islet cell tumors, these are rare tumors occurring in approximately 1 in every 100,000 people, and only 1% of all pancreatic tumors are NETs. NETs can result in the overproduction and secretion of pancreatic hormones, including insulin, gastrin, glucagon, and vasoactive intestinal peptide (VIP), resulting in specific clinical syndromes on presentation.

Cystic lesions of the pancreas are a relatively common incidental finding on body imaging, with prevalence in the general population ranging up to 14%. Classification of these cysts is important as they can either be true cysts, pseudocysts (usually related to pancreatitis) or related to benign or malignant neoplasms. Radiological imaging has historically helped distinguish the etiology of the cystic lesions in 75 to 90% of presentations. True epithelial cysts are rare in the general population and are classically only associated with cystic fibrosis, von Hippel-Lindau disease, and autosomal dominant polycystic kidney disease. Pseudocysts, related to pancreatitis or trauma, are the most common cystic lesion identified in the pancreas. Approximately 20 to 40% of patients with chronic pancreatitis develop pseudocysts, while only 2-3% of those with acute pancreatitis will develop them. Cysts associated with malignancy may rarely occur with exocrine tumors, occasionally with endocrine tumors, or in isolation. Cystic neoplasms include intraductal papillary mucinous neoplasms, mucinous cystic neoplasms, and serous cystadenomas.

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Conflict of interest statement

Disclosure: Kyle Stevens declares no relevant financial relationships with ineligible companies.

Disclosure: Christopher Lisanti declares no relevant financial relationships with ineligible companies.