Transabdominal and Laparoscopic Ultrasound in a Bariatric Setting

1. TITLE Transabdominal and Laparoscopic Ultrasound in a Bariatric Setting 2. BACKGROUND AND RATIONALE

2.1 Clinical Background Bariatric surgery is an established and effective treatment for severe obesity. In Denmark, approximately 2,000 bariatric procedures are performed annually. These procedures result in significant and intended weight loss and improvement in metabolic comorbidities. However, rapid weight loss is associated with an increased risk of gallstone formation.

Gallstone disease is one of the most common postoperative complications following bariatric surgery. Approximately 10% of patients undergo cholecystectomy within two years after surgery, increasing to up to 20% within ten years. Importantly, cholecystectomy in patients who previously underwent bariatric surgery is associated with:

• Increased risk of surgical complications

• Higher rates of reoperation * More technically complex procedures * Increased risk of bile duct injury In patients with Roux-en-Y gastric bypass, management of biliary tract disease is particularly challenging due to altered gastrointestinal anatomy, which complicates endoscopic access (e.g., ERCP).

2.2 Preventive Treatment and Diagnostic Challenge Prophylactic treatment with ursodeoxycholic acid (Ursochol) has been shown to significantly reduce the risk of symptomatic gallstone disease in the first two years after bariatric surgery.

However:

• Ursochol is only effective in patients who do not already have gallstones.

• Therefore, accurate preoperative detection of gallstones is essential.

Conventional transabdominal ultrasound (TAUS) is the standard imaging modality for gallbladder evaluation. However, in patients with severe obesity: * Ultrasound penetration is limited * Image quality may be reduced * Small stones and sludge may be overlooked * Sensitivity may be as low as 62-68%

Thus, diagnostic uncertainty may lead to:

• Under-treatment (missed stones)

• Over-treatment (inappropriate prophylaxis)

• Inconsistent national implementation

2.3 Rationale for Laparoscopic Ultrasound (LUS)

Laparoscopic ultrasound (LUS) allows:

• Direct placement of the probe on the liver surface

• Shorter acoustic distance

• Higher image resolution

• Potentially improved detection of subtle pathology

• Fewer hospital visits for the patients prior to surgery

Only one prior study has directly compared TAUS and LUS in this population. That study suggested higher overall pathology detection with LUS, but lacked:

• Histological confirmation

• Sample size justification * Assessment of microlithiasis * Gallbladder wall measurements * Formal evaluation of interobserver agreement within each ultrasound modality

Therefore, a well-designed prospective paired diagnostic study is warranted. 3. OBJECTIVES

3.1 Primary Objective To compare the diagnostic detection rate of gallbladder pathology between transabdominal ultrasound (TAUS) and laparoscopic ultrasound (LUS) in patients undergoing bariatric surgery.

3.2 Secondary Objectives

1. To evaluate interobserver agreement within TAUS and LUS examinations 2. To compare examination time between modalities 3. To assess image quality 4. HYPOTHESES

1\. Laparoscopic ultrasound detects significantly more gallbladder pathology than transabdominal ultrasound.

2\. LUS has lower interobserver variability compared to TAUS.

5\. STUDY DESIGN Prospective observational diagnostic comparative study with paired within-patient design.

Each participant undergoes:

* Two independent TAUS examinations * Two independent LUS examinations

All examinations are performed blinded and independently.

No randomization is performed.

No experimental interventions are introduced.

6\. STUDY PROCEDURES

6.1 Preoperative Phase

Participants undergo:

• Two transabdominal ultrasounds

• Interobserver variability [Срок оценки: From preoperative ultrasound (within 31 days before surgery) to laparoscopic ultrasound during bariatric surgery]