Overview
Definition:
One anastomosis gastric bypass (OAGB), also known as single anastomosis gastric bypass (SAGB), is a laparoscopic bariatric surgical procedure that involves creating a smaller gastric pouch and connecting it directly to a segment of the small intestine, bypassing a significant portion of the stomach and duodenum
It is a restrictive and malabsorptive procedure aimed at significant weight loss and improvement of obesity-related comorbidities.
Epidemiology:
OAGB has gained popularity globally due to its efficacy, technical simplicity, and favorable outcomes compared to traditional Roux-en-Y gastric bypass (RYGB)
It is increasingly being adopted by bariatric surgeons in India for managing severe obesity, especially in the context of DNB and NEET SS examinations where knowledge of evolving bariatric techniques is crucial.
Clinical Significance:
OAGB offers a powerful tool for managing severe obesity and its associated metabolic disorders, such as type 2 diabetes mellitus, hypertension, and dyslipidemia
Understanding its principles, indications, surgical technique, and potential complications is essential for surgical residents preparing for postgraduate examinations, as it represents a significant advancement in bariatric surgery.
Indications
Indications For Surgery:
Primary indication is severe obesity (BMI ≥ 40 kg/m²) or moderate obesity (BMI ≥ 35 kg/m²) with significant comorbidities like type 2 diabetes, hypertension, sleep apnea, or dyslipidemia that are refractory to medical management
OAGB is particularly considered for patients with super-obesity (BMI > 50 kg/m²) due to its high efficacy and simpler reconstruction compared to RYGB.
Contraindications:
Absolute contraindications include active peptic ulcer disease, inflammatory bowel disease, severe coagulopathy, and inability to tolerate general anesthesia or major surgery
Relative contraindications may include severe malnutrition, uncontrolled psychiatric disorders, or inability to adhere to postoperative dietary and lifestyle changes
Careful patient selection is paramount.
Patient Selection Criteria:
Comprehensive evaluation by a multidisciplinary team including surgeons, dietitians, psychologists, and endocrinologists
Patients should undergo thorough preoperative assessment to identify risks and ensure suitability for bariatric surgery
Informed consent regarding the procedure, its benefits, risks, and potential long-term sequelae is mandatory.
Surgical Technique
Preoperative Preparation:
Routine preoperative workup including blood tests (CBC, electrolytes, LFTs, RFTs, coagulation profile, HbA1c), ECG, chest X-ray, and potentially upper GI endoscopy
Nutritional counseling and initiation of a low-calorie diet may be recommended for patients with super-obesity
Prophylactic antibiotics and deep vein thrombosis prophylaxis are standard.
Operative Procedure Steps:
Typically performed laparoscopically
A small gastric pouch (approximately 30-50 ml) is created along the lesser curvature of the stomach, sparing the pylorus
The jejunum is transected approximately 150-200 cm from the duodenojejunal flexure (alimentary limb)
The distal end of the alimentary limb is then anastomosed to the gastric pouch
The biliopancreatic limb is anastomosed to the jejunum at approximately 100-150 cm distal to the gastrojejunal anastomosis, creating a common limb
The length of the alimentary and biliopancreatic limbs can be adjusted based on BMI and the desired degree of malabsorption.
Anastomotic Techniques:
Gastrojejunal anastomosis can be performed using staplers or hand-sewing techniques
Jejunojejunal anastomosis is typically done with staplers or hand-sewing
Careful attention is paid to achieve tension-free and leak-proof anastomoses
The position of the gastrojejunal anastomosis relative to the gastric pouch and the length of the bypassed segments are critical factors influencing outcomes.
Postoperative Care
Immediate Postoperative Management:
Patients are typically monitored in a recovery room for vital signs and pain
Intravenous fluids are administered
Early mobilization is encouraged to prevent VTE
Pain management is crucial, often involving multimodal analgesia.
Dietary Advancement:
A stepwise progression from clear liquids to full liquids, pureed foods, soft foods, and finally a regular diet is followed over several weeks
Patients receive detailed dietary instructions and counseling on portion control, chewing habits, and hydration
Nutritional supplements (vitamins, minerals, protein) are prescribed lifelong.
Monitoring And Follow Up:
Regular follow-up appointments are scheduled to monitor weight loss, nutritional status, and resolution of comorbidities
This includes regular blood tests to check for deficiencies (e.g., iron, vitamin B12, vitamin D, calcium)
Patients are monitored for potential complications such as leaks, strictures, or nutritional deficiencies
Long-term follow-up, often lifelong, is essential.
Complications
Early Complications:
Bleeding from staple lines or anastomoses
Anastomotic leaks at the gastrojejunal or jejunojejunal sites, which can lead to peritonitis or abscess formation
Strictures at the gastrojejunal anastomosis
Injury to adjacent organs
Venous thromboembolism (VTE)
Pneumonia.
Late Complications:
Marginal ulcers at the gastrojejunal anastomosis, often associated with H
pylori infection or NSAID use
Bile reflux into the gastric pouch or esophagus, leading to esophagitis or gastritis
Internal hernias, which can lead to bowel obstruction
Nutritional deficiencies (e.g., iron deficiency anemia, vitamin B12 deficiency, vitamin D deficiency, calcium deficiency)
Dumping syndrome, characterized by rapid gastric emptying causing nausea, vomiting, diarrhea, abdominal pain, and vasomotor symptoms.
Prevention And Management Of Complications:
Meticulous surgical technique to minimize leaks and bleeding
Careful patient selection and preoperative optimization
Prophylactic measures for VTE
Close postoperative monitoring for signs of complications
Early diagnosis and management of leaks (surgical intervention, antibiotics)
Management of marginal ulcers with PPIs and H
pylori eradication
Management of bile reflux with medications and, in severe cases, revision surgery
Prompt diagnosis and surgical management of internal hernias
Lifelong nutritional supplementation and regular monitoring for deficiencies.
Prognosis
Weight Loss Outcomes:
OAGB is associated with significant and sustained weight loss, typically achieving 60-80% excess weight loss within the first 1-2 years postoperatively
The procedure leads to a high rate of remission or improvement in obesity-related comorbidities, particularly type 2 diabetes mellitus.
Improvement In Comorbidities:
Remission or significant improvement in type 2 diabetes is observed in up to 80-90% of patients
Marked improvement in hypertension, dyslipidemia, obstructive sleep apnea, and joint pain is also common
These improvements contribute significantly to enhanced quality of life.
Long Term Follow Up And Recurrence:
Long-term follow-up is crucial to monitor weight maintenance, nutritional status, and manage potential late complications
While OAGB is highly effective, some weight regain can occur over time, necessitating continued lifestyle modifications
Revisional surgery may be considered for significant weight regain or persistent complications.
Key Points
Exam Focus:
Understand the OAGB as a single anastomosis procedure, differentiating it from RYGB
Key surgical steps include creation of a small gastric pouch and a long biliopancreatic limb
Be aware of common complications like marginal ulcers and bile reflux, and their management.
Clinical Pearls:
Pylorus sparing is a hallmark of OAGB, which may contribute to less dumping syndrome compared to some RYGB configurations
However, bile reflux is a notable concern
Accurate measurement of limb lengths is crucial for efficacy and to minimize malabsorptive complications.
Common Mistakes:
Inadequate gastric pouch creation leading to insufficient restriction
Incorrect measurement or positioning of limb lengths leading to poor weight loss or excessive malabsorption
Neglecting lifelong nutritional supplementation and follow-up, leading to severe deficiencies
Delays in diagnosing and managing anastomotic leaks or internal hernias.