Gastrointestinal and Abdominal: Bariatric Surgery Flashcards
Bariatric Surgery
Bariatric surgery, or weight loss surgery, limits the
amount of food the stomach can hold by reducing
the stomach’s capacity to a few ounces. In addition to
reducing food intake, some weight loss surgeries also
alter the digestive process, which curbs the amount
of calories and nutrients absorbed.
Bariatric Surgery: Anatomy
The relevant anatomy involves the stomach and prox-
imal small bowel. These are well-vascularized organs,
and although they can withstand significant transec-
tions and bypass, it remains critical not to compro-
mise the blood supply. See Chapter 3, Stomach and
Duodenum, and Chapter 4, Small Intestine.
Morbid Obesity: Epidemiology
The increased risk for morbidity and mortality is pro-
portional to the degree of a person’s excess weight. The
most common way to quantify obesity is by the body
mass index (BMI), which is calculated as [weight (kilo-
grams)/height (meters)2]. The BMI associated with
lowest mortality is between 20 and 25 kg/m2. An adult
with a BMI greater than 25 kg/m2 is considered overweight; an adult with BMI greater than 30 kg/m2 is considered obese.
Morbid obesity, approximately equivalent to a person
being 100 pounds overweight, can be a life-threatening
condition. A person is classified as being morbidly
obese if he or she has a BMI greater than or equal to 40 kg/m2
, or a BMI of greater than or equal to 35 kg/m2
with an obesity-related disease, such
as type 2 diabetes, heart disease, or sleep apnea.
Approximately 100 million Americans are obese,
and 15 million are morbidly obese. Obesity is rapidly
becoming an epidemic in the United States, with preva-
lence rates of 15% in 1980, and increasing to 33%
in 2004. Obesity costs the U.S. healthcare system an
estimated $117 billion annually, according to the
National Institute of Diabetes and Digestive and
Kidney Diseases. After tobacco, obesity is the second
leading cause of preventable death in the United States.
Morbid Obesity: Pathophysiology
The ultimate biologic basis of obesity is unknown. A
sedentary lifestyle and the availability of high-caloric
foods certainly contribute to this disease process. This
disorder, nevertheless, is accompanied by a reduction
in life expectancy, which is due in large part to the
complications associated with diabetes, hypertension,
and sleep apnea.
Morbid Obesity: History
The approach to the morbidly obese patient has to
take into account the weight history, dietary habits,
lifestyle, exercise tolerance, and medical comorbidi-
ties of the individual. Previous attempts at nonsurgi-
cal weight loss should be documented. The dietary
and weight history should focus on identifying eating
disorders, as well as any emotional or psychiatric con-
ditions that may be linked. Counseling a patient to
engage in an active exercise regimen is also critical.
The medical history should aim at ruling out any
metabolic causes of obesity, such as hypothyroidism
and Cushing’s syndrome. Obesity is also related to a host
of medical comorbidities that should be identified and
stabilized preoperatively. These are listed in Table 10-1.
As with any other major operation, surgical risk should
be individually assessed on the basis of the medical
history.
Morbid Obesity: Physical Examination
A general physical examination should be performed
preoperatively. Specific to the bariatric population,
the airway should be evaluated for difficulty of intu-
bation as well as risk for obstructive sleep apnea. The
abdomen should be assessed for the degree of central
obesity, as well as prior surgical incisions, which may
make laparoscopic surgical approaches difficult.
Morbid Obesity: Diagnostic Evaluation
Patients are considered suitable candidates for bariatric
surgery if they meet criteria set by the 1991 National
Institutes of Health consensus conference on bariatric
surgery. Patients must:
• Have a BMI greater than 40, or a BMI greater than 35 with significant
weight-related comorbidities, such as diabetes,
hypertension, or sleep apnea.
• Have no metabolic abnormalities that could cause
weight gain.
• Have attempted and failed at nonsurgical weight
loss.
• Be psychologically stable with no identifiable eating
disorders.
As for any major surgical procedure, the preopera-
tive workup should include an ECG and possibly
stress testing to rule out cardiac disease. A chest radio-
graph may show an enlarged heart or pulmonary
congestion. A sleep study may be necessary to evalu-
ate for sleep apnea, which may necessitate the use of
a continuous positive airway pressure machine during
sleep. Patients with a significant history of heartburn
or reflux should undergo an upper gastrointestinal
radiograph to rule out a hiatal or paraesophageal her-
nia, which may alter the surgical plan.
Morbid Obesity: Treatment: Nonsurgical Options
Before surgery, all potential candidates should have
attempts at lifestyle modifications, including supervised
diet and exercise plans. Pharmacologic options include
sympathomimetic drugs, such as phentermine or sibu-
tramine (Meridia), or drugs that alter fat digestion, such
as orlistat (Xenical). However, most studies have shown
that medical management of obesity fails in up to 95%
of cases and that most patients regain a substantial por-
tion of their excess weight as soon as medications are
discontinued.
Morbid Obesity: Treatment: Surgical Options
Bariatric surgery has been recognized by the National
Institutes of Health as the most effective method to
achieve long-term weight loss. A myriad of bariatric
surgical procedures have been devised over the years
and may be classified as either being restrictive, mal-
absorptive, or a combination thereof. Restrictive pro-
cedures include adjustable gastric banding (AGB),
sleeve gastrectomy, and vertical banded gastroplasty.
Malabsorptive procedures such as the jejunal-ileal
bypass or biliopancreatic diversion have largely fallen
out of favor because of issues with malnutrition and
organ failure.
The two most commonly performed bariatric surgi-
cal procedures in modern practice are AGB and the
Roux-en-Y gastric bypass (RYGB). RYGB, the most
popular operation in the United States, is both restric-
tive and malabsorptive. Both AGB and RYGB can be
performed either in traditional open fashion or laparo-
scopically, although the latter approach has significant
advantages in decreasing pain, recovery time, and wound
complications. Performing these procedures laparoscop-
ically is technically challenging and associated with a
significant learning curve.
RYGB involves the creation of a proximal gastric
pouch of approximately 30 mL capacity. Intestinal con-
tinuity is restored by attaching a limb of proximal
jejunum to this gastric pouch with biliopancreatic con-
tinuity established via a jejunojejunostomy (Fig. 10-1).
Patients may experience dumping syndrome post-
operatively with RYGB, especially with consumption
of highly concentrated sweets. Dumping syndrome is
manifested by abdominal cramps, nausea, vomiting,
and flushing. In a way, this may be used as an effec-
tive form of negative reinforcement to limit the con-
sumption of sweets. Other risks of this procedure
include leakage from the intestinal anastomoses, as
well as ulcers, strictures, and internal hernias.
Morbidly obese patients are inherently high risk
given their propensity for deep venous thrombosis
formation and higher incidence of diabetes, hyperten-
sion, obstructive sleep apnea, and undiagnosed heart
conditions. These all have to be taken into consideration
when planning for RYGB. Mortality rate averages 0.5%.
AGB involves placing a silicone band around the
upper portion of the stomach (Fig. 10-2). A catheter
connects the band to an injection chamber, which is
implanted subcutaneously. In the postoperative period,
this chamber is used to inflate the band gradually to
progressively narrow the gastric inlet and limit caloric
intake by controlling portion size. Because no intestines
are bypassed, dumping syndrome does not occur.
Complications of this procedure include slippage of the
stomach around the band, erosion of the band into the
lumen of the stomach, and infection, leakage, and
migration of the band and injection chamber. Mortality
rate averages 0.05%.
Morbid Obesity: Results
Bariatric surgical procedures achieve variable weight loss
results. RYGB, whether performed laparoscopically or
open, is associated with 75% to 80% excess weight loss
(EWL). Excess weight is defined as preoperative weight
minus a person’s ideal body weight. More importantly,
this is associated with resolution of diabetes in approxi-
mately 80% to 85% of patients, hypertension in 70% to
80%, and obstructive sleep apnea in 75%. Significant
improvements are also seen in lipid profiles and other
cardiac risk factors. Long term, there is a 40% decrease
in all causes of mortality. Patients need to be monitored
long term for any signs of mineral and vitamin defi-
ciency. There are case reports of comatose patients as a
result of B-complex vitamin deficiencies, as well as prob-
lems with calcium deficiencies and transient hair loss;
patients usually recover after the first 6 months postop-
eratively. In the long term, up to 50% of patients who
undergo RYGB may have some weight regain, such that
the effective long-term excess weight loss is approxi-
mately 65% EWL.
AGB achieves 30% to 40% EWL within a year.
However, long-term weight loss is approximately 50%
to 55% EWL at 5 to 10 years postoperatively. Diabetes
improves in approximately 60% of patients, as do most
other comorbidities. Good weight loss results with
AGB are particularly dependent on compliance with
healthy dietary habits, as patients will not develop any
dumping syndrome to dissuade them from consuming
inordinate amounts of sweets.
Regardless of the surgical procedure, success in terms
of postoperative weight loss is still highly dependent
upon patient behavior in terms of pursuing healthy
dietary and exercise behavior. Patients who continue to
overeat and disregard restrictions on portion size run the
risk of dilating the gastric pouch in either a RYGB
or AGB. Weight regain in the long term can often be
be attributed not to any technical surgical failure, but to the
fact that patients may revert back to unhealthy lifestyle
habits.
Key Points
Morbid obesity is defined as a body mass index greater than
40 kg/m2, or a body mass index of 35 to 40 kg/m2
with comorbidities such as hypertension, diabetes,
or sleep apnea.
•
Pharmacologic options such as phentermine, sibu-
tramine, or orlistat may result in some weight loss but
rarely achieve sustained results in the long term.
•
Surgical options are generally categorized into
restrictive and malabsorptive options.
•
The two most commonly performed bariatric pro-
cedures are the Roux-en-Y gastric bypass and the
adjustable gastric band.
•
Excess weight loss is approximately 65% to 80%
with Roux-en-Y gastric bypass and 50% with
adjustable gastric band.
•
Both procedures are associated with significant
improvements in medical comorbidities.
