The study aimed to compare the effects of bowel preparation methods of a normal diet for 1 day, a low residue diet for 1 day, and laxative bowel cleaning on the image quality of magnetically controlled capsule endoscopy, and to assess the rate of completion of the examination, small intestine transit time, lesion detection, patient tolerance, and safety of the three regimens.

Inclusion Criteria:

1. Age ≥ 18 years, male or female
2. One of the following examination indications:

(1) Unexplained gastrointestinal bleeding; (2) Unexplained iron deficiency anaemia; (3) Suspected Crohn's disease or monitoring and directing treatment for Crohn's disease; (4) Suspected small bowel tumour; (5) Monitoring the development of small bowel polyposis syndrome; (6) Suspected or difficult to control malabsorption syndromes (e.g., celiac disease, etc.); (7) Detection of NSAID-associated small bowel mucosal damage; (8) Those with a clinical need to exclude small bowel disease.

Exclusion Criteria:

1. People who are ineligible for surgery or refuse to undergo any abdominal surgery (once the capsule is retained it cannot be removed surgically);
2. Known or suspected gastrointestinal obstruction, stenosis, and fistula;
3. People with implanted cardiac pacemakers or other electronic devices;
4. People with swallowing disorders;
5. Women during pregnancy;
6. People who are unable or unwilling to provide informed consent.