ROCHESTER, Minn., July 21-A rare complication of gastric bypass surgery leaves its victims virtually disabled, Mayo Clinic researchers here reported today.
But others said the complication, called nesidioblastosis, a hyperfunction of insulin-producing beta cells, may also point the way to new treatments for diabetes.
The complication leads to a potentially life-threatening deficiency of sucrose in the central nervous system, says Fred Service, M.D., a Mayo endocrinologist and colleagues reported in the July 21 issue of the New England Journal of Medicine.
Action Points
- Inform patients contemplating a weight-reduction operation that, although it is a rare complication, nesidioblastosis is more frequent among patients who have had Roux-en-Y gastric bypass than in the general population.
- Note also that while the cause of the nesidioblastosis remains unclear, a partial removal of the pancreas appears to resolve the condition.
- Advise interested patients that the so-called "dumping syndrome," whose symptoms include flushing, dizziness, profuse sweating, and weakness, is commonly seen in gastric bypass patients; however, central nervous system glucose deficiency is not part of the dumping syndrome.
They described six patients who were referred to Mayo between 2000 and 2004 because of severe neurological symptoms -- including confusion and loss of consciousness -- after eating.
The symptoms were so severe, Dr. Service said in an interview, that patients couldn't drive or work, and "had to be babysat" for fear they could have a potentially deadly episode.
The diagnosis was hypoglycemia, caused by excess insulin production, leading to a severe deficiency of glucose in the central nervous system (i.e., neuroglycopenia).
One patient had insulin-producing pancreatic tumors that were surgically removed, but the rest had enlarged and overactive islets without cancer. The mean size was significantly larger than in obese controls (214 micrometers versus 151, p=0.001).
When the first patient was referred, the researchers considered the Roux-en-Y gastric bypass to be coincidental, especially because the patient also had insulin-producing pancreatic tumors. But "subsequent experience…led us to raise the possibility of a link between the islet hyperfunction and the bypass surgery," Dr. Service and colleagues wrote.
Over the same time period, nine people who had not had gastric bypass surgery were shown to have nesidioblastosis at the Mayo Clinic, meaning that the gastric bypass patients formed 40% of the total caseload.
However, only about a tenth of 1% of the U.S. population has had a gastric bypass.
The treatment was partial removal of the pancreas, Dr. Service said, which appeared to ameliorate the problem in all but one of the patients. That patient had a recurrence of symptoms, possibly because not enough of his pancreas was removed.
The cause of the nesidioblastosis is less clear, but it seems "possible that beta-trophic factors may be brought into play after bypass surgery," causing the growth of beta cells and islets, excess insulin production, and post-meal hypoglycemia, the authors argued.
"There is some scientific evidence that gut hormones could be mediating this," Dr. Service said.
If that's the case, said University of Washington endocrinologist David Cummings, M.D., in an accompanying editorial, it should spur research to identify the mediators "so that their physiological effects can be harnessed" against diabetes.
"On the face of it, the paper is a report of a novel adverse consequence of gastric bypass surgery," Dr. Cummings said in an interview, adding that the condition remains quite rare. "It's hardly a public health crisis."
One of the effects of gastric bypass surgery is to cure type 2 diabetes, he said, and it may be that "the same physiology is melting away the diabetes most of the time and occasionally goes too far."
He added, "I see this a hopeful finding that there's something about gastric bypass surgery that causes beta cells to regrow -- and rarely overgrow -- and if we can find that thing we have the potential of bottling it and using it treat diabetes."
Dr. Service said he's not entirely comfortable with that view: "I think Dr. Cummings may be looking at this through rose-colored glasses."
If there is an upside to the finding, he said, it's that surgeons who perform Roux-en-Y surgery will be alerted to the possibility of nesidioblastosis in their patients.
"The follow-up of (gastric bypass surgery) patients hasn't been as assiduous as it should have been," Dr. Service said.
He said the symptoms should not be mistaken for those of the so-called "dumping syndrome" -- flushing, dizziness, profuse sweating, and weakness -- that is commonly seen in gastric bypass patients.
Related articles:
- Bariatric Surgery, a Growth Market, Quadruples in Five Years
- Experience Counts for Laparoscopic Gastric Bypass Surgery
Primary Source
New England Journal of Medicine
Source Reference: Service, GJ et al. Hyperinsulinemic Hypoglycemia with Nesidioblastosis after Gastric-Bypass Surgery. N Engl J Med 2005;353:249-54.
Secondary Source
New England Journal of Medicine
Source Reference: Cummings, DE et al. Gastric Bypass and Nesidioblastosis -- Too Much of a Good Thing for Islets? N Engl J Med 2005; 353:300-1.