Surgical Treatment of Obesity: Analysis of Weight Loss Efficacy and Complications of Small Bowel Bypass

Surgical Treatment of Obesity:

Some severely obese patients fail to achieve effective weight loss despite strict diet, exercise, and medication. In such cases, surgical methods may be considered. Surgical treatments for obesity include gastrointestinal bariatric surgery, liposuction, and liposuction. The former, through methods such as small bowel bypass or gastrectomy, creates malabsorption of nutrients or restricts diet to achieve weight loss and alleviate complications. The latter removes locally accumulated fat through resection or liposuction to improve body appearance.

Small Bowel Bypass:
Payne et al. first successfully treated obesity clinically with jejunocolonic bypass in 1956. This surgery bypasses most of the small intestine, affecting the absorption of most nutrients.

1. Surgical Method

The jejunum is cut 36 cm proximal and closed distally. The proximal jejunum is anastomosed to the transverse colon end-to-side in the middle of the transverse colon. Although this surgery is quite effective for weight loss, it is currently prohibited due to liver failure and death in some cases. Generally, the jejunum is cut approximately 36 cm proximal to the ileum, and the distal end is closed. About 10 cm from the cecum, the proximal jejunum is anastomosed with the terminal ileum via an end-to-side anastomosis.

Clinically, it has been found that after an end-to-side jejunoileostomy, a large amount of digested food refluxes into the ileum, leading to nutrient reabsorption. Therefore, some researchers have designed an end-to-end jejunoileostomy based on the side-jejunoileostomy, where the proximal jejunum and terminal ileum are anastomosed end-to-end. The remaining segment of jejunum is closed at the jejunal end, and the ileal end is anastomosed end-to-side to the cecum, transverse colon, or sigmoid colon to facilitate drainage of small intestinal secretions.

There is no uniform standard for the length ratio of the retained proximal jejunum to the terminal ileum, and different clinical reports exist. For example, Scott retained 30 cm of proximal jejunum and 20 cm of terminal ileum; while Buchwald retained 40 cm of jejunum and 4 cm of terminal ileum, both achieving ideal weight loss results. However, Weismann demonstrated a direct correlation between the amount of small intestine preserved and weight loss; if the total length of the small intestine preserved exceeds 64cm, the weight loss effect is not significant.

2. Surgical Outcomes
Clinically, most surgeons perform end-to-end jejunostomy with a total small intestine preservation of 55cm. 80% of patients experience significant weight loss, with an average reduction of 45kg. The more severe the obesity, the greater the weight loss; younger patients experience more weight loss than middle-aged patients. The weight loss effect mainly occurs in the first year post-surgery, accompanied by improvements in insulin resistance, hypertension, heart failure, lung function, and hyperlipidemia. Weight stabilizes in the second to third year post-surgery. Due to the good compensatory absorption capacity of the small intestine, many patients experience weight regain later.

3. Surgical Complications
The incidence of complications after small bowel bypass surgery is high. Clinically manifested complications include:

(1) Death
Death can occur in both the early and late stages post-surgery, with an incidence of approximately 3%. Causes of death include liver failure, pulmonary embolism, heart failure, anastomotic leakage, and sepsis. (2) Diarrhea: Almost all patients experience uncontrollable diarrhea. Diarrhea usually begins on the 5th day post-surgery, quickly leading to 12-20 watery stools per day, later decreasing to 6-10 semi-formed stools.

(3) Metabolic Disorders: Approximately 40%–100% of patients experience metabolic disorders. Due to diarrhea, significant mineral loss occurs, leading to hypocalcemia, hypokalemia, hypomagnesemia, and iron and zinc deficiencies. Vitamin B₁₂ and folic acid deficiencies are also common.

(4) Hypoproteinemia: Due to diarrhea and malabsorption, at least 40% of patients have hypoproteinemia.

(5) Urinary and Biliary Stones: Approximately 8% of patients develop urinary and biliary stones. This may be due to increased synthesis of bile salts and glyceric acid, as well as hyperoxaluria.

(6) Hepatic Steroidosis: It has been reported that 95% of patients weighing over 113 kg had preoperative hepatic steatosis, which became more pronounced during rapid weight loss in the early postoperative period. Within 4 years post-surgery, 95% of patients had liver biopsies confirming fatty infiltration in the liver.

(7) Abnormal Liver Function: 40% of patients experienced abnormal liver function post-surgery. The earliest onset was 3 weeks post-surgery, and the latest was 2 years post-surgery. The main manifestations of abnormal liver function were nausea, vomiting, jaundice, and hepatomegaly. Approximately 1% of patients experienced hepatic coma and death. 3% of patients had significant liver fibrosis. Liver failure was believed to be due to the presence of large numbers of Bacteroides in the abandoned small intestine, producing hepatotoxic endotoxins that severely damaged the liver.

(8) Failed Weight Loss: Approximately 20% of patients were unsatisfied with post-operative weight loss. Some patients required a second surgery to remove a section of the small intestine to achieve the desired weight loss.