Gastric bypass: surgical treatment of morbid obesity

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摘要

Morbid obesity is a major health concern in so many countries. It is associated with severe life-threatening co-morbidities. Unfortunately, many studies have proven that non-surgical approaches to lose weight are doomed to fail. There is good evidence that bariatric surgery is the most enduring and efficacious means of tackling morbid obesity with regards to long-term weight loss.

Roux-en-Y gastric bypass is today one of the gold standard surgeries. It is based on several mechanisms: restriction, malabsorption, and changes in gut hormones secretions.
In this chapter, all aspects of this bariatric procedure such as anatomical details, indications, contraindications, surgical setting and technical details are carefully presented.

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2009-05

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WeBSurg.com, May 2009;9(05).
URL: http://www.websurg.com/doi-ot02en336.htm

Gastric bypass: surgical treatment of morbid obesity

1. Introduction

The main operative steps in performing a gastric bypass are:
1) the creation of an isolated 25 mL proximal gastric pouch,
2) the creation of a Roux-en-Y gastroenterostomy to the pouch. The length of the duodenojejunal limb usually measures 30 to 50 cm (up to 75 cm if the BMI >50). The length of the gastrojejunal limb (or Roux limb) ranges from 100 cm for a Body Mass Index (BMI = weight in kg/square of the height in meters) <50 to 150 cm for a BMI >50.

This procedure results in a combination of 2 weight-loss mechanisms:
- the primary mechanism is mechanical restriction, by virtue of the creation of the 25 mL upper gastric pouch;
- the secondary mechanism is malabsorption: the Roux limb delays the mixing of the nutrients with the biliary and pancreatic juices while preserving the entero-hepatic cycle of the bile salts.

2. Anatomy

• Local anatomy

1. Lesser omentum
2. Enlarged left lobe of the liver
3. Esophageal hiatus
4. Diaphragm
5. Spleen
6. Right crus
7. Left crus

• Vasculature

1. First vascular arcade
2. Second vascular arcade

• Infra-mesocolic region

1. Ligament of Treitz

3. Indications and contraindications

Indications
- BMI greater than 40;
- BMI between 35 and 40 associated with significant comorbidity: hypertension, diabetes, degenerative joint disease or arthritis, sleep apnea (National Institute of Health Consensus Conference, 1991).

Absolute contraindications
- BMI <35;
- contraindication to general anesthesia;
- pregnancy;
- severe psychiatric disorders;
- drug or alcohol addiction;
- untreated esophagitis.

4. Preoperative evaluation

Laboratory evaluation: basic chemistry panel, complete blood count, thyroid function tests, serum cortisol, urine cortisol, serum cholesterol, serum triglycerides.

Upper endoscopy:
- rule out inflammatory ulcerous gastric pathology, which would no longer be accessible by gastroscopy after the bypass procedure;
- search for and treat H pylori infection when present.

Ultrasound of the abdomen:
- rule out cholelithiasis, which would necessitate cholecystectomy along with the gastric bypass procedure. Some authors recommend that a cholecystectomy be routinely performed in the setting of a gastric bypass, even in the absence of cholelithiasis.

Cardiovascular evaluation: exclude any contraindications to anesthesia.

Psychiatric evaluation: rule out any behavioral abnormalities that would contraindicate limited food intake.

Endocrine evaluation: rule out an endocrine abnormality as the etiology of morbid obesity.

Echocardiography: assess left ventricle function.

Dental evaluation: the small diameter of the gastrojejunal anastomosis makes it necessary for all food to be properly chewed.

5. Operating room set-up

• Patient

• Standard position

- supine position with both legs abducted;
- both arms extended;
- reverse Trendelenburg position: a system to secure the patient to the table must be used in order to prevent slipping (45° tilt test);
- stirrups for feet positioning;
- all contact zones are carefully checked and padded to avoid nerve and arterial compression or pressure sores.

• Variation

Supine position with the legs together and the arms apart. The patient remains in this position throughout the procedure.

• Team

• Standard position

For the gastric dissection and gastrojejunal anastomosis:
1. The surgeon stands between the patient’s legs.
2. The first assistant stands on the patient’s right.
3. The second assistant stands on the patient’s left.
4. The scrub nurse stands on the surgeon’s right.

• Variation

1. The surgeon stands on the patient’s right.
2. The first assistant stands on the surgeon’s right.
3. The second assistant stands on the patient’s left.
4. The nurse stands opposite the surgeon.

• Equipment

1. Operating table: conventional operating tables can accommodate a weight of 140 to 170 kg. For weights in excess of 170 kg, a special table with adequate width is required.
2. Anesthetic equipment
3. Laparoscopic video unit
4. Two high-resolution monitors
5. A power generator (for electrocautery device, vessel sealing device, ultrasonic scissors)
The operating room must be spacious enough to accommodate the anesthetic equipment, the laparoscopic unit, and an operating table properly adapted to the size and weight of the patients.

6. Pneumoperitoneum

• Open laparoscopy

The thickness of the fatty subcutaneous tissue and the weight of the abdominal wall render access to the peritoneal cavity difficult.
Ideally, the pneumoperitoneum should be established under visual control before placement of the first trocar. To do the puncture, some authors prefer to use either a Veress or a Palmer needle, which is introduced in the left hypochondrium.
After dissection of the subcutaneous tissue, the use of long and adequate retractors allows for the incision of the aponeurosis under direct vision. The peritoneum is then visualized and opened. This approach, which can be difficult considering the thickness of the abdominal wall, can be learned easily.

• Insufflation pressure

Due to the thickness of the wall, it may be necessary to increase the pressure of the pneumoperitoneum to 14 or even 16 mm Hg. The anesthesiologist should be warned of the increase in insufflation pressure and asked to monitor the capnograph.

7. Trocar placement

• Trocars

Trocar placement is of paramount importance in this procedure due to the thickness of the abdominal wall and the depth of the surgical field.
This procedure is usually performed using 6 trocars.
The first trocar is placed a handbreadth’s and a half underneath the xiphoid process in a slightly reverse Trendelenburg (with a 10 degree tilt).
The other trocars will be placed under visual control.

• Optical trocar

The camera is introduced in the 12mm trocar A.

• Reverse Trendelenburg

The jejunojejunal anastomosis is performed almost flat. The gastric division and the gastrojejunal anastomosis are performed using a reverse Trendelenburg position, with a tilt ranging from 30 and 45 degrees.

• Retractors

Two 5mm trocars are introduced:
- C on the anterior axillary line as proximal to the costal margin as possible in order to retract the stomach;
- D in the epigastric position to retract the liver.

• Operators

Three 12 mm trocars are introduced:
- B on the left midclavicular line midway between trocars A and C;
- E on the right midclavicular line, at the same level than trocar B;
- F on the left midclavicular line, at the level of the umbilicus.

8. Instruments

• Optical

The whole procedure can be carried out with a 30 degree scope.

• Operators

The optical trocar, which is not being used, may become an operating trocar.
Operating trocars B, E, and F accommodate the following instruments:
1. Bipolar grasper
2. Hook dissector
3. Scissors
4. Grasper
5. Suction-irrigation device
6. Linear stapler
7. Circular stapler with tiltable anvil
8. Ultrasonic scalpel
9. Needle holder
10. Vessel sealing system / Ligasure device

• Retractors

Two 5 mm retractor trocars (C and D) accommodate the following instruments:
1. Liver retractor
2. Grasper to expose or retract the stomach or small bowel

• Others

Additional necessary instruments include:
1. Extraction bag
2. Protective plastic sheath covering the circular stapler during its introduction. Because of the large diameter of the circular stapler, it is introduced directly into the abdomen by enlarging trocar site D.
3. 34 French orogastric tube if manual gastro-entero-anastomosis

9. Exposure

• Retraction of the liver

During the maneuvers in the upper part of the abdomen, the left lobe of the liver is retracted cephalad and laterally to visualize the hiatus. This must be performed carefully: the contact area with the liver must be large in order to avoid hepatic capsular tears.
Retractor liver injuries are rarely deep, but the bleeding impairs the visualization of the operative field and absorbs part of the light intensity.

• Greater omentum

During the maneuvers in the lower part of the abdomen, all of the fatty tissue of the greater omentum and the transverse colon are retracted cephalad. The retractor can then be positioned below the transverse colon, which is pulled cephalad with the omentum.

10. Submesocolic steps

Division of omentum:
Once the trocars have been placed, the procedure begins with the division of the omentum in order to prepare for the Roux limb. The omental division also helps to prepare the exposure of the colon in order to identify the duodenojejunal flexure. The omentum is lifted upward in order to be divided using either the Ligasure device or the ultrasonic scissors introduced in trocar F.
1. Identification of Treitz’ flexure and measurements:
The division of the omentum has contributed to the exposure of the transverse mesocolon. It helps to easily identify the Treitz’s (duodenojejunal) flexure. The biliary limb is measured by being placed entirely in the left hypochondrium. It is measured over 75cm and it will be attached to the stomach by a stitch, which is used as a landmark.
Jejunojejunal limb measurement:
The alimentary limb is measured over 150cm. It is fixed to the biliary loop by a stitch to prepare for the anastomosis at the foot of the loop.
Jejunojejunal anastomosis:
A forceps introduced into trocar D is used to grasp this landmark and pulls it into the left hypochondrium in order to expose the two loops to be anastomosed. The two loops are opened 60mm from the landmark stitch. A 60mm linear stapler, white cartridge, is then introduced to perform the anastomosis. The opening hole of the automatic linear stapling device is closed by placing two stitches on each end of this opening and using a running suture.
Closure of the mesenteric gap:
The mesenteric gap originating from the jejunojejunal anastomosis is re-approximated using a running non-absorbable suture.

11. Gastrojejunal anastomosis

• Supramesocolic steps

Hiatal exposure:
Following adequate hiatal exposure, the future gastric pouch is calibrated at 25 mL to determine the first line of transection.
1. This first line is perpendicular to the axis of the esophagus.
2. The second line is parallel.
Gastric pouch calibration:
The dissection of the gastric pouch begins between the first and second vascular arcades on the lesser curvature.
Transection:
The dissection begins on the right edge of the stomach. The lesser omentum is incised, and the posterior gastric surface is dissected over 3 to 4 cm, perpendicular to the axis of the esophagus. The lesser sac is often opened. The linear stapler (60 mm cartridge, 3.5 mm staples) is introduced through the right hypochondrium trocar (E). The stomach is retracted caudally, the gastric tube removed, and the stapler fired.
The dissection is then pursued cephalad, towards the angle of His, along the posterior surface of the stomach. The left margin of the left crus is exposed. A linear stapler (60 mm cartridge, 3.5 mm staples) is introduced through trocar B into this posterior space and fired. An additional application may be necessary to completely divide the remainder of the stomach.

• Dangers

• Injury of the pancreas

If the dissection is too deep, it can cause injury of the anterior surface of the pancreas or the splenic artery.

• Splenic injury

A dissection performed too laterally can lead to injury of the spleen.

• Esophagus division

Longitudinal division of the esophagus:
A medial application of the stapler can divide the esophagus. This can be avoided with the placement of a calibration tube.

• Gastrojejunal anastomosis

• Technique

The anesthesiologist pushes the orogastric tube through the esophagus down to the proximal gastric pouch.
An incision just over the bulging tip of the orogastric tube at the gastric staple line is made a few millimeters in length at the corner between the horizontal and vertical staple line. The tube is then retrieved into the abdominal cavity and extracted through trocar B until the center rod of the anvil appears. The anvil is freed from the orogastric tube.

• Anvil characteristics

We use the DST Series™ EEA ™ OrVil™ device 25mm stapling device manufactured by Covidien Autosuture, which is a DST Series™ 25mm anvil assembly, with the anvil head secured in the tilted position.

• Variation

If the DST Series™ EEA ™ OrVil™ device 25mm stapling device is not available, a 25mm circular stapler with a tiltable anvil (Covidien) is used, instead of a rigid 21mm circular stapler, which can injure the esophagus. Specific steps must be followed:
1. A monofilament suture is threaded through the 2 eyelets of the anvil.
2. The spring in the anvil is removed.
3. The mechanism to tilt the anvil head is activated. This step makes a clicking noise when correctly done.
4. The anvil tip is then inserted into an 18 French orogastric tube.
5. A monofilament suture is used to keep the head of the anvil in a tilted vertical position secured to the orogastric tube.

• Variation

Transabdominal passage of the anvil:
1. After the first gastric stapler is fired, an incision is made for the point of the anvil.
2. A gastrotomy is performed outside of the gastric division line.
3. The anvil is not prepared as previously described but passed directly into the gastrotomy with the point forward.
4. The gastrotomy is stapled closed.
5. The gastric division is then completed.

12. End of procedure

Closure of Petersen’s defect:
The space of Petersen is formed by the Roux limb anteriorly, the mesenteric fold caudally and posteriorly, and the transverse colon cephalad. This defect must be closed using a non-absorbable suture in order to avoid internal hernias.

The space above (Petersen’s space) is limited by the transverse mesocolon and the transverse colon itself.
It is limited exteriorly by the jejunal limb, which is brought up either ante-colic or retro-colic.
It is limited posteriorly by the root of the mesentery.
This space has to be closed to prevent the duodenal jejunal limb from becoming occluded or strangulated, which is very hard to diagnose.
Closure of the mesenteric defect
Closure of the mesocolon defect for retro-colic passage.

Trocar wounds >5 mm
A lavage of the upper area of the abdomen is performed. A drain may be left adjacent to the gastrojejunal anastomosis. If so, it can be removed after 24 to 48 hours. All trocar wounds measuring over 5 mm in diameter are closed with an aponeurotic suture.

13. Postoperative management

The nasogastric tube is removed at the end of the procedure.

A water-soluble contrast examination is performed on POD1 to confirm the absence of anastomotic leakage. If the examination reveals no anomalies, the patient is allowed to drink water.

From POD2 to POD9, the patient remains on a liquid diet. During the 3 weeks following surgery, food must be soft or chopped. After these 3 weeks, the patient may progressively start consuming small bites of food. The patient consults a dietician before discharge and 3 weeks after surgery.

The patient can leave the hospital on or after POD3. Follow-up is performed 1 week after discharge, when sutures or clips are removed.

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