Welcome back. Thanks for joining me for this discussion of gastrinomas in the section of general surgery.
Gastrinomas result in gastric acid hypersecretion. As a result, patients can develop severe
and debilitating acid-related peptic ulcer disease. Remember, when a clinical scenario is presented
to you that has difficult to treat ulcer disease, think gastrinoma. Gastrinoma results in the secretion
of gastrin by duodenal or pancreatic gastrinomas. As a result of the high gastrin levels, there is
increased gastric acid secretion. Here’s a depiction of mechanism of action of gastrin. Gastrin stimulates
increased histamine release through the enterochromaffin like cells or ECL. This is highlighted
in the yellow box. As a result of increased histamine production, the parietal cells then increase
acid secretion. Note however, that acid is actually a negative feedback on gastrin levels.
Our bodies have control mechanisms in place so that with increasing acid or decreasing pH levels,
the G cells actually reduce our gastrin secretion. In patients who have had surgery where this acid
cannot provide the negative feedback to the G cells, we actually have a hypergastrinemia.
What are some physical findings associated with gastrinomas? Patients often complain of diarrhea.
Here’s also a picture of severe peptic ulcer disease. As a reminder, any peptic ulcer disease,
that is difficult to treat once you consider gastrinoma. The etiology of the diarrhea actually
comes from high acid, low pH’s ability to inactivate pancreatic enzymes which are necessary
for fat absorption. As a result of this decreased pancreatic enzyme activity, poor fat absorption
leads to fatty stools and diarrhea. Historically, patients may complain of weight loss, GI bleeding
again associated with a difficult to treat peptic ulcer disease, and as a reminder, the very
high-yield multiple endocrine neoplasia particularly type 1. Type 1 multiple endocrine neoplasia
involves parathyroid tumors, pituitary tumors, and pancreatic tumors including gastrinomas
and insulinomas which is discussed in a different module. Routine laboratory studies are unlikely
to be helpful including chemistries and CBCs. However, unique to gastrinomas is a plasma
gastrin level. Values greater than 1,000 pg/cc is considered significant and almost diagnostic
of gastrinoma. Similarly, an adjunctive secretin stimulation test can also demonstrate
a gastrinoma by a paradoxical increase in the gastrin level. Some imaging study may be helpful
in diagnosis or localizing the gastrinoma. This image demonstrates a cross-sectional CT scan
abdomen/pelvis demonstrating a duodenal or head of the pancreas mass. In the appropriate
clinical setting, this may represent a gastrinoma. Remember, gastrinomas are not limited
to pancreas. It can also occur in the duodenum. Medical therapy of gastrinomas includes
proton pump inhibitors. Unfortunately, because of the continued gastrin secretion,
proton pump inhibitors may provide only transient symptomatic relief. Unfortunately,
the vast majority of patients with gastrinoma will require a surgical resection. Let’s assume
that the mass was in the duodenum. In this situation, the entire duodenal area and including
the head of the pancreas may need to be resected with subsequent reconstruction.
This is the depiction of a pancreaticoduodenectomy or a classic Whipple procedure.
In some instances when the gastrinoma is in the head of the pancreas or even in the duodenum,
common tiers of blood supply mandates that all surrounding tissues be removed. As a result,
multiple reconstructions have to be recreated such as a hepaticojejunostomy, a pancreaticojejunostomy,
and ultimately a gastrojejunostomy. Every pancreaticoduodenectomy has three anastomoses.
Some clinical pearls to remind you of. Remember, when a patient has a difficult to treat peptic
ulcer or peptic ulcer that is not responsive to medical management, consider gastrinoma in your
differential diagnosis. For your examination, it’s also worthwhile to discuss Zollinger Ellison syndrome.
Zollinger Ellison syndrome is a syndrome related to gastrinomas or hypergastric acid secretion.
This is the classic triad of peptic ulcer disease, diarrhea, and high gastrin levels. Again, presenting
symptoms include abdominal pain, diarrhea from the poor fat absorption, and heart burn, chronic
in nature. This may be associated with an MEN syndrome, typically MEN type 1: parathyroid,
pituitary, and pancreatic lesions. Thank you very much for joining me in this discussion of gastrinomas.