What is a VIPoma?
A VIPoma is a rare type of islet cell tumor that is associated with the endocrine system and is cancerous in 50-75% of patients. The incidence of the disease is so rare, in fact, that only 1 in 10 million people each year are diagnosed with the condition. VIPomas are almost always diagnosed in adults rather than children, and it arises most commonly in people who are around 50 years old. Though technically anyone can develop a VIPoma, women are slightly more likely to get it than men; it is unclear so far why this might be true.
VIPomas are considered pancreatic neuroendocrine tumors because they originate in the pancreas, an important organ that functions both as part of the endocrine system and the gastrointestinal system. These pancreatic endocrine tumors develop from special pancreatic cells called islet cells, which are important in glucose metabolism and represent the bulk of the pancreas that is devoted to endocrine function. Even though these cells represent a small fraction of pancreatic volume, they receive an oversized share (10-15%) of blood flow.
The name VIPoma (and the unusual capitalization) refers to vasoactive intestinal peptide (VIP), a hormone that has an impact on both the digestive system and the cardiovascular system. In addition to vasodilation (the widening of blood vessels), VIP contributes to muscle relaxation and the secretion of water and electrolytes in the digestive tract. When the tumor is present, it causes an overproduction of VIP in the pancreas, which, in turn, causes a host of gastrointestinal and general symptoms:
- diarrhea (can become chronic diarrhea)
- abdominal pain and cramping
- hypokalemia (muscle cramps stemming from low blood potassium)
- achlorhydria (the absence of hydrochloric acid in digestive acid secretions)
- metabolic acidosis (an electrolyte disorder due to an imbalance of acids and bases in the body)
- redness or flushing in the face (similar to carcinoid syndrome)
- hypercalcemia (muscle weakness due to high calcium levels in the blood)
- weight loss
VIPoma is also sometimes referred to as pancreatic cholera syndrome (PCS) or WDHA syndrome because of the three main symptoms that many patients experience: watery diarrhea, hypokalemia, and achlorhydria. In other contexts it can be referred to Verner-Morrison syndrome (VMS) after the two physicians who originally described the condition. In about 6% of cases, VIPomas can arise from a related condition called multiple endocrine neoplasia type 1, a disorder that involves the development of neoplasms (abnormal growths) or lesions on some endocrine system glands.
What Does the Endocrine System Do?
To really grasp how a VIPoma affects the body, it’s helpful to consider endocrinology and how the glands in our body regulate various processes. In essence, the endocrine system works like a chemical messenger network that links different organs and body systems. Through the secretion of hormones into the bloodstream, different parts of the body will modify their behavior (when everything is working correctly) so they can adjust to new stimuli. In the case of VIP, both the pancreas and hypothalamus can secrete it, but it is also produced in the digestive tract.
The imbalance of any kind of hormone—too much or too little—can cause a wide variety of health problems. The adrenal glands, for instance, secrete a hormone called cortisol that regulates the metabolism of glucose (among other things); too much cortisol in the system can lead to a condition called Cushing’s syndrome that includes symptoms like abdominal obesity and high blood pressure. Another example is diabetes; when the pancreas doesn’t produce enough insulin and your body isn’t able to regulate blood sugar levels, a number of symptoms and complications can emerge.
How is a VIPoma Diagnosed and Treated?
Diagnosing VIPoma can be challenging in large part because of how rare it is, but it generally involves examining a patient’s medical history as well as performing a physical exam. One of the primary tests involves determining whether secretory diarrhea is a factor; secretory diarrhea happens when electrolytes are secreted into the digestive tract and cause excessive water to accumulate in the bowels. Another important test looks for serum VIP and serum potassium in the blood. A doctor of gastroenterology might also use imaging tests like an endoscopic ultrasound or somatostatin receptor scintigraphy to determine localization of the tumor.
If VIPoma is confirmed, one of the most important initial tasks is to treat the inevitable dehydration that accompanies the high volume watery diarrhea. Dehydration is generally addressed through fluid and electrolyte replacement, and bicarbonate can be used to mitigate the dangers of metabolic acidosis and fecal loss. The next part of treatment focuses on controlling or slowing down the diarrhea, usually with octreotide, a medication that simulates the hormone responsible for regulating other hormones produced by the endocrine system (somatostatin). Streptozocin and lanreotide (a somatostatin analogue) have also been used to treat VIPomas.
Once the dehydration and diarrhea are under control, doctors have a few options to attempt to cure the disease. If the tumor hasn’t become a metastatic disease (meaning that it hasn’t spread to other organs), surgery can be an effective option; through surgical resection, the tumor is removed from the pancreas and results in a cure for about 50% of patients. If metastasis has already occurred, some types of radiotherapy can also be effective. While some chemotherapies are being explored, thus far none of them have been curative.
When to See a Doctor
The good news is that VIPomas are extremely rare, so it’s unlikely that any of the gastrointestinal symptoms noted above are an indicator of the condition. However, since the symptoms are shared by other digestive diseases and disorders, it is good to be mindful of your bowel health. If you have been experiencing chronic diarrhea or any of the other symptoms of a VIPoma, it might be time to get checked out. At Cary Gastro, our board-certified physicians and skilled staff are dedicated to providing excellent healthcare. Contact us today if you would like to request an appointment.