| Keywords
Insulinoma, bariatric surgery, EUS
Introduction
Insulinoma is a rare condition associated
with severe hypoglycemia and occasionally with hyperphagia.
This is the first case report that we are aware of in which
an insulinoma was unmasked by gastric bypass surgery.
Methods for EUS Capture
SVHS recording was digitally captured using
Dazzle Movie Star software. EUS was performed with a Pentax
EG3630UR solid state radial EUS at 7.5 Mhz.
Case/Body
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Video
Clip 1: EUS movie of insulinoma. |
A 48-year-old woman with chronic obesity
underwent bariatric surgery with creation of a stapled gastric
pouch and roux-en-y gastroenterostomy. Prior to her surgery,
she had a craving for sweets but could sleep through the night
without eating. She had otherwise felt well prior to her surgical
procedure.
The surgery was uncomplicated. However,
on the sixth postoperative day, she developed hemiparesis.
A neurological and vascular evaluation was performed, and
a patent foramen ovale was found. The patient was anticoagulated.
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Figure
1A |
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Figure
1B |
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Figure
1C |
The patient had two similar events in the
two following weeks, and, during an emergency room evaluation,
after an overnight fast, was found to have a blood sugar of
24 mg/dl. A simultaneous insulin level was 6.2 micro IU/ml
(nl 1.4-14) and C-peptide was 740 pmol/l (nl 170-900). She
was given intravenous glucose with resolution of her hemiparesis.
She was transferred to our hospital for
further evaluation.
The patient had no prior medical problems.
Her only medications at the time of evaluation were aspirin
and coumadin. She had no exposure to oral hypoglycemic agents.
Family history was significant for a brother
with a prolactinoma. Her review of systems was only significant
for early satiety since her gastric surgery. Her physical
exam was unremarkable. A CT scan of the abdomen was normal
other than postoperative changes.
The patient was fasted for four hours and found to have a
blood sugar of 28 mg/dl. Her insulin level was 11 micro IU/ml
(levels greater than 6 with simultaneous blood sugars of less
than 45 are suspicious for insulinoma). Her C-peptide was
1032 pmol/l (normal less than 200 for glucose less than 45);
her proinsulin level was 64 pmol/l (normal less than 5 for
glucose less than 45); her Beta hydroxybutarate was 0.43 millimolar
(less than 2.7 during hypoglycemia are suspicious for insulinoma;
and her serum sulfonurea screen was negative.
The patient underwent EUS. The forward viewing
Pentax solid-state instrument was advanced to the gastric-jejunal
anastomosis but could not be passed through this narrowed
area. Therefore, scanning was done through the gastric remnant
at 7.5 mHz. A 1.1 cm by 1.1 cm hypoechoic mass was found in
the pancreas adjacent to the splenic artery (Video: Video
Clip 1; Images: Figures 1A and 1B). Representative Visible
Human images and an entry into the Visible Human database
are shown in Figures 2A-2C.
The patient was taken to surgery, and her
pancreas explored. The tumor was not initially palpable but
was ultimately found underneath the retrogastric Roux-en-y
limb using intraoperative ultrasonography (Figure 3). It was
removed by enucleation uneventfully. Pathology revealed a
completely resected insulinoma. Histology and chromogrannin
stains are shown in Figure 4A and 4B.
The patient's symptoms have totally resolved,
and postoperative blood sugar measurements have remained normal.
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Figure
3 |
Figure
4A |
Figure
4B |
Discussion/Summary
Statement
Insulinomas are rare tumors which are usually
benign but often quite symptomatic (1, 2). Although some subjects
with insulinoma have normal body habitus (3), hyperphagia
can result from the patient’s attempts to alleviate
symptomatic hypoglycemia. This causes some subjects with insulinoma
to gain weight (4, 5).
The evaluation of subjects in which insulinomas
are considered generally begins with biochemical screening.
Laboratories suggestive of insulinoma include hypoglycemia
with inappropriately elevated insulin and C-peptide levels
as well as a negative evaluation for oral hypoglycemic agents
(1-5).
Our case report has the typical biochemical
features that suggest insulinoma.
As part of the initial evaluation, CT scanning
was performed to look for a mass. Although this is often done,
CT is notoriously poor at localizing insulinomas (6). EUS
has become the preferred method to image the pancreas when
insulinoma is suspected, and in this case, EUS identified
the tumor after a normal CT scan, despite the limitations
imposed from previous anti-obesity surgery. At the time of
surgical resection, the addition of intraoperative ultrasonography
(11) made surgical removal possible with minimal morbidity
despite the altered anatomy.
The most interesting aspect of this case
was the manner of presentation. The patient presented with
significant neurologic symptoms following anti-obesity surgery.
This suggests to us that the insulinoma had been effectively
palliated by the patient through overeating, and only when
her caloric intake was curtailed, did she suffer the effects
from her tumor. As far as we are aware, this is the first
case in which anti-obesity surgery unmasked an insulinoma
and suggests that evaluation for hypoglycemia may be useful
in the evaluation of subjects with morbid obesity.
References
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198.
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