Magnetically controlled capsule endoscopy (MCE) is a noninvasive technique (90.4% sensitivity, 94.7% specificity and 93.4% accuracy) without requiring sedation or air insufflation, which makes it welcomed by most of participants. However, due to the large size of the stomach, clear views are obtained with the stomach distended. Participants were asked to drink 1000ml water for gastric preparation in a short time according to the standard procesure. It is hard for some participants especially the old and can cause discomfort. If the capsule stays in the stomach for a long time (>4 hours), it will affect the completion rate of small intestine examination and be inconvient to both of the endoscopist and patient.

It is a promising way to fill the stomach with carbonated drinks in some diagnosis and treatment methods. A study using carbonated drinks for gastric filling in the procedure of multi slice spiral computed tomography (MSCT) showed higher diagnostic rate for gastric cancer (85%VS80%). Rapid filling and absorption, greater comfort feeling and little pressure changes lead to higher acceptance of participants.

So, researchers have a novel idea using soda water to take place of pure water in the gastric preparation. The combination of gas and liquid in gastric filling greatly reduces the amount of fluid that participants need to drink, which makes the shorter preparation time and less feeling of fullness. In a pilot study before, investigators found the usage of soda water obtained similar gastric distention score and shorter gastric transit time (GTT) than standard preparation method.

This prospective, single blind, randomized controlleds trial aimed to prove the safety and efficiency of soda water in the process of gastric preparation and explore the impact on the follow-up small bowel examination.

This is a prospective, single blind, randomized controlled clinical study approved by the Endoscopy Center of Changhai Hospital in Shanghai from July, 2020 to September,2020. Approval to carry out this study was granted by the Ethics Committee, Changhai Hospital, Naval Medical University.

According to the results of our pilot study, 252 participants(with 20% withdrawal rate) aged 18-75 will accept standard gastric preparation or gastric preparation with soda water randomly (ratio 1:1).All patient will provid written informed consent for this study before undergoing baseline MCE.

Investigators evaluated the feasibility of a novel gastric preparation methods regimens on gastric distention,gastric cleansing, feeling of fullness, diagnostic yield, satisfaction questionnaire, gastric transit time, small bowel transit time and completion rate. The safety were evaluated at two week after procedure for the occurance of adverse events. Investigators also plan to explore whether soda water can affect the subsequent examination of the small intestine, and the difficulty in intervention under special circumstances.

All participants underwent a bowel preparation that consisted of a low-residue diet for 24 hours, fluid intake, and ingestion of 2L polyethylene glycol-based electrolyte solution 12 hours before the examination. On the examination day, participants arrived at hospital in the morning after an over night fast (>8hours). Then they would be randomly assigned to controll group or soda group.

Control group:40 minutes before capsule ingestion, all participants swallowed 100ml clear water containing 50mg simethicone. During the period, participants were asked to have a proper walk to wash out bubbles. An additional 900ml clear water was drunk to obtain good vision before undergoing MCE examination.

Soda water group：Control group:40 minutes before capsule ingestion, all participants swallowed 100ml clear water containing 50mg simethicone. During the period, participants were asked to have a proper walk to wash out bubbles. An additional 400ml soda water was drunk to obtain good vision before undergoing MCE examination.

Then, the patient enter the examination room to finish the examination.

Inclusion Criteria:

• Over 18 years and below 75 years of age
• Plan to undergo MCCG examination in Changhai Hospital

Exclusion Criteria:

• dysphagia or symptoms of gastric outlet obstruction, suspected or known intestinal stenosis, overt gastrointestinal bleeding, fistulas and strictures;
• history of gastrointestinal surgery or suspected delayed gastric emptying;
• Implanted metallic devices such aspacemakers, defibrillators, artificial heart valves or joint prostheses;
• Allergic to high molecular materials such as simethicone and streptozyme;
• Pregnancy or mentally ill person;
• currently participating in another clinical study;