Patients with morbid obesity provide a special challenge for the diagnostic radiologist. Large size, decreased mobility, and variable postoperative anatomy make imaging procedures more difficult to perform and interpret. Tailored protocols and a good knowledge of surgical anatomy and complications, such as those described herein, are required to achieve optimal results in the bariatric patient.
Patients with morbid obesity provide a special challenge for the
diagnostic radiologist. Large size, decreased mobility, and
variable postoperative anatomy make imaging procedures more
difficult to perform and interpret. Tailored protocols and a good
knowledge of surgical anatomy and complications are required to
achieve optimal results in the bariatric patient.
Indications for surgery
Five percent of males and seven percent of females in the United
States are morbidly obese, weighing more than one hundred pounds
over ideal body weight.1 Medical complications of severe obesity
include coronary artery disease, heart failure, respiratory
insufficiency, diabetes, hypertension, venous stasis disease, and
degenerative arthritis.2 The mortality rate is 11 times higher in
the morbidly obese than in non-obese persons of the same age and
sex.3 Medical and dietary treatments fail to achieve a sustained
weight loss, making surgery the only viable treatment option in
most of these patients.
Bariatric surgery for weight reduction is considered in patients
whose body mass index (BMI, kg/m2) exceeds 40 (100 pounds over or
160% of ideal weight). Surgery is also recommended in patients with
a BMI of 35 to 40 who have high-risk complications, such as
cardiopulmonary disease, sleep apnea, uncontrolled diabetes, and
hypertension.2,4 The goal of surgery is to produce sufficient
weight loss to reduce medical complications, not necessarily to
achieve an ideal body weight.5 Psychological and dietary counseling
are an integral part of bariatric treatment.
Overview of surgical techniques
Surgical approaches to weight reduction have evolved over the
last 30 years based on three concepts: 1) malabsorption of
nutrients due to bypass of a portion of intestine, as in
jejunoileal bypass (JIB); 2) mechanical restriction of caloric
intake, exemplified by vertical banded gastroplasty (VBG); and 3) a
combination of mechanical restriction and malabsorption, typified
by the Roux-en-Y gastric bypass (RYGB).6
A variety of other bariatric techniques exist, including those
that have been discontinued (gastric wrapping, intragastric
balloons, horizontal gastroplasty)5 and others which are preferred
by fewer surgeons (pancreaticobiliary bypass,7 long limb gastric
bypass,8 or combined VBG/RYGB).6 The newest methods use
laparoscopic techniques, including placement of a restrictive
gastric band, which is adjustable, using fluoroscopic guidance.9 It
is best to become familiar with the techniques used by the surgeons
who refer to your radiology practice.
This review will focus on JIB, VBG, and RYGB because they
account for the majority of bariatric surgeries performed to date
and are most likely to be encountered in a general radiology
Jejunoileal bypass (JIB)
JIB was the first popular bariatric surgery, performed in over
100,000 patients from 1954 until the mid-1970s.1 In this procedure,
the proximal jejunum was divided 30 cm from the ligament of Treitz
and anastomosed to the distal ileum 10 cm from the ileocecal
valve.10 The long, defunctionalized segment of jejunum and ileum
was left as a blind limb or anastomosed to the colon. Weight loss
from malabsorption after JIB was dramatic, but late metabolic
complications occurred in 50 to 80% of patients, necessitating
takedown surgery in one-third.1 Although JIB surgery has been
abandoned, a large number of patients still have an intact bypass
and may be referred for imaging of complications or prior to JIB
Fluoroscopy in JIB shows rapid transit of contrast from the
proximal jejunum to the anastomosis with the distal ileum (figure
lA). The functional bowel segment may be dilated with thickened
folds to compensate for malabsorption (figure lB). When the blind
limb is anastomosed to the colon, it may be opacified during a
barium enema. CT can be used to image the bypassed bowel
Roux-en-Y gastric bypass (RYGB)
Gastric bypass replaced JIB and has a number of technical
variations. Staple lines are placed obliquely in the proximal
stomach to separate a 10- to 15-cc proximal gastric pouch from the
bypassed distal stomach. This is achieved by stapling alone
(gastric bypass in continuity, figure 2A) or by stapling and
transection of the stomach (divided or isolated gastric bypass,
figure 2B).11 The proximal pouch is drained by a gastrojejunostomy
with Roux-en-Y jejunal anastomosis to reduce bile reflux gastritis.
The small proximal gastric pouch and 10- to 11-mm outflow channel
restrict food intake, and malabsorption occurs due to bypass of the
stomach, duodenum, and a variable length of jejunum.6 Dumping
syndrome leads to avoidance of dairy products and sweets, including
ice cream.12 RYGB produces better sustained weight reduction than
VBG and is currently preferred by many surgeons.5,6,12
Scout films will show oblique or mixed gastric staple lines and
a staple line at the Roux-en-Y anastomosis in the left mid-abdomen.
At fluoroscopy, oral contrast traverses the esophagus into a small
proximal gastric pouch and exits the gastrojejunostomy (figure 2C).
The distal stomach does not opacify when the staple line is intact
(figure 2D). Retrograde filling of the Roux-en-Y limb can occur
later in the examination, opacifying the Roux limb and duodenum and
refluxing into the bypassed distal stomach, though the latter is
CT after RYGB shows the proximal gastric pouch superomedially
and gastrojejunostomy anteriorly, with no oral contrast in the
bypassed distal stomach (figure 2E).
Vertical banded gastroplasty (VBG)
VBG was introduced in 1980 and has been the most widely used
gastric restrictive surgery.12 Vertical staples are placed along
the lesser curvature of the stomach to create a 10- to 15-cc
proximal gastric pouch with a 10- to 11-mm outflow tract. The
outflow channel is reinforced by non-opaque marlex mesh through a
gastric window2 or an opaque silastic ring13 (figure 3A). Intake of
a small volume of food into the proximal pouch triggers early
satiety, and weight loss is due to decreased caloric intake. VBG is
proposed as a simpler bariatric procedure with a lower complication
rate than gastric bypass,2 but it is less successful at producing
sustained weight loss.5,12
Scout films show a vertical staple line, with or without an
opaque ring. In fluoroscopy, contrast traverses the small proximal
pouch along the lesser curvature and exits through a single outflow
channel to opacify the distal stomach (figures 3B, 3C). CT shows a
staple line with oral contrast in both the proximal pouch and
distal stomach (figure 3D).
Practical tips for imaging the bariatric patient
Fluoroscopy/radiography-Fluoroscopy is the best way to define
surgical anatomy, leaks, staple line dehiscence, and pouch
obstruction.1,14 Contrast studies complement endoscopy, which has
greater sensitivity for diagnosis of gastritis and ulcers.1 The
following tips are suggested for fluoroscopic examinations:
1) Obtain a good patient history. Date and type of surgery and
current patient complaints influence how the study is performed
2) Evaluate staple lines with a plain radiograph before giving
oral contrast. The configuration of the staple line determines the
optimal patient position for demonstrating anatomy:15 (a) Vertical
staples = VBG, best shown in the right posterior oblique position,
(b) horizontal or mixed staple line = horizontal gastroplasty or
gastric bypass, best shown in the left posterior oblique (LPO)
3) Study the stomach first! The first swallow of contrast is
often key to defining anatomy, presence of staple line dehiscence,
and size of the gastric outlet.14 Take immediate spot images to
document the proximal pouch and outflow channel. The esophagus can
be evaluated after gastric anatomy is defined.
4) For early complications (e.g., postoperative leak,
obstruction) use water soluble contrast and videofluoroscopy.
5) For late complications (e.g., weight gain, dehiscence, pouch
enlargement, ulcer), use high density barium for initial swallows
to establish anatomy. If there is no outlet obstruction, a
half-dose of effervescent granules and high-density barium will
provide distension and mucosal detail. A double-contrast esophagram
should be performed before recumbent views are taken. An esophagram
in the RAO position using low-density barium will demonstrate
esophageal motility, herniation of the gastric pouch, and the
diameter of the outflow channel post gastric bypass.
6) A final overhead radiograph will demonstrate global
tomy, Roux-en-Y anastomosis, distal small bowel loops, and
presence of contrast in surgical drains when a leak is
7) In patients who are too large for the fluoroscopy equipment,
a limited contrast study can be obtained by properly positioning
the patient and taking overhead films of the upper abdomen while
oral contrast is given.
Computed tomography (CT)-When patient size permits, CT is used
to investigate postoperative abscess, hematoma, bowel obstruction,
bypassed bowel segments, and to guide interventional
procedures.14,16 CT supplements fluoroscopy in localizing the
extent of gastrointestinal leaks. To optimize CT diagnosis, the
following tips are recommended:
1) Obtain an adequate surgical and clinical history. As the
radiologist is less likely to see the patient in the CT suite, this
must be done by the technical staff.
2) Use abundant oral contrast (2% iodinated contrast), including
a dose while the patient is being positioned on the table.
3) Identify the staple lines and
configuration of the stomach and jejunum on CT images to verify
that they match expected operative anatomy. Correlate fluoroscopic
studies with CT examination.
4) Evaluate bypassed stomach and small bowel loops for
obstruction, inflammation, intussusception, or other
Complications of bariatric surgery
Surgery in morbidly obese patients is difficult, having higher
complication rates than in patients at a normal weight. Operative
mortality for VBG and RYGB is less than 1%.2 Infection due to
gastrointestinal leak is the most common cause of perioperative
mortality after bariatric surgery. Pulmonary embolism is the second
most common cause, occurring with an incidence of nearly 1% in the
morbidly obese population.1 Perioperative antibiotics and low dose
heparin therapy are used routinely to reduce risk of infection and
Gastrointestinal leak occurs in 0.6% of patients after VBG2 and
in 1 to 2% of patients after RYGB.5 Tachycardia is the first sign
of leak and may be accompanied by fever, abdominal pain, or
referred shoulder pain. Fluoroscopy is performed with water soluble
contrast to localize the leak (figures 4A, 5A). CT with dilute
iodinated contrast also can be used to further localize leaks and
abscesses (figures 5B, 5C). Gastric perforation is most often due
to ischemia from the stapling procedure,4 but can be secondary to
trauma from nasogastric or gastrostomy tubes, hyperacidity,14 or
interventional procedures (figure 6).
Hemorrhage due to bleeding vessels at staple lines or
anastomoses is an uncommon complication in the perioperative
period. When imaging is required in patients with a decreasing
hematocrit and suspected hemorrhage, CT is the best modality
Stomal stenosis after gastric restrictive surgery causes
vomiting, gastroesophageal reflux, and enlargement of the proximal
pouch.17 It occurs in 12% of patients following gastric bypass,
usually within the first two months after surgery.17 Early outlet
obstruction is due to edema and will resolve without intervention.
Stomal stenosis developing after six weeks is due to fibrosis.
Treatment with balloon dilatation, performed endoscopically or with
fluoroscopic guidance, is successful in about two-thirds of
patients. Those who do not respond to initial dilatation usually
require surgical revision.17,18
Staple line dehiscence, VBG
Dehiscence of the staple line after VBG increases outflow from
the proximal pouch, reducing the effect of early satiety and
allowing increased food intake. Unsatisfactory weight loss or
weight gain results.1 Staple dehiscence develops in 30 to 48% of
patients who undergo VBG, and revision surgery may be required.6,19
To detect VBG dehiscence at fluoroscopy, it is essential to image
the stomach first, with the patient in RPO position to document the
proximal gastric pouch, outflow channel, and exit of contrast
through areas of staple line dehiscence before the distal stomach
opacifies (figure 8).15
Staple dehiscence and ulcer, RYGB
Staple line dehiscence after RYGB causes both weight gain and
ulcer formation. Ulcers occur because dehiscence creates a
gastrogastric fistula, allowing acid from the distal stomach to
enter the proximal pouch and jejunostomy. Stomal ulceration occurs
on the jejunal side of the anastomosis (figure 10) and generally
responds to medical therapy with H2 blockers.11 Revision surgery to
correct the gastrogastric fistula is required in patients with
The surgical anatomy influences the incidence of ulcers. When
RYGB is performed in continuity, the incidence of staple line
disruption is 29%, with stomal ulceration occurring in 16%. When
the stomach is stapled and transected in divided gastric bypass,
the incidence of gastrogastric fistula and stomal ulcer is 3%.11
Interposing the jejunal limb between the proximal pouch and distal
stomach further reduces the risk of gastrogastric fistula.6
Complications in bypassed bowel segments
After the performance of RYGB there is a 0.3% incidence of
significant bleeding from the bypassed distal stomach or duodenum
which frequently does not respond to H2 blockers, necessitating
distal gastrectomy.20,21 Gastritis also is relatively common in the
distal stomach, perhaps due to altered motility and bile reflux.22
Acute gastric dilatation after RYGB causes a closed loop
obstruction2 (figure 10) which can be prevented by placing a
temporary gastrostomy tube at the time of surgery. However, after
the gastrostomy tube is removed, access to the distal stomach in
the symptomatic patient is difficult, requiring either endoscopy
using a long pediatric colonoscope22 or percutaneous access to the
distal stomach by fluoroscopic23 or CT guidance.24
Intussusception, adhesive obstruction, and internal herniation
may occur in bypassed loops post-JIB or RYGB.1,10 Internal
herniation of the small bowel post-RYGB predisposes the patient to
closed loop obstruction and bowel infarction (figure 11). Plain
radiography and CT are most useful for detecting these
complications in bypassed bowel segments.16
Gallstones occur in up to 33% of bariatric patients due to
mobilization of cholesterol during weight loss. Protein calorie
malnutrition develops in 20% of patients who undergo gastric
restrictive surgery because of avoidance of meats.1
By far, the most severe metabolic disturbances result from
malabsorptive procedures. After JIB, late complications include
diarrhea (58%), nephrolithiasis (21%) (figure 1A), cholelithiasis
(20%), liver dysfunction (29%), liver cirrhosis (7%), and
malnutrition.10 After RYGB, metabolic effects include anemia and
Radiology is essential in the management of the bariatric
patient. Fluoroscopy is the best examination available for defining
operative anatomy, gastrointestinal leak, and staple line
dehiscence, and it can supplement endoscopy in the evaluation of
ulcer disease. CT is an excellent tool for diagnosing extraluminal
pathology, imaging bypassed bowel segments, and guiding
interventional procedures. Successful imaging of the bariatric
patient is achievable when steps are taken to correctly document
the surgical anatomy and to recognize the variety of postoperative
complications that can occur. AR
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Dr. Burton is with the Department of Radiology at the University
of Florida College of Medicine in Gainesville, FL.