目的 总结乳果糖氢甲烷呼气试验（LHMBT）在消化道不适患儿中的应用，分析LHMBT阳性患儿的临床特征及内镜特点。方法 回顾性分析上海市儿童医院消化科2021年8月至2022年10月因消化道不适住院患儿的临床资料。根据LHMBT结果，患儿被归入LHMBT阳性组和LHMBT阴性组，比较两组患儿的临床特征。其中63例患儿完善胃肠镜检查，分析其内镜以及病理组织学特点。结果 纳入124例消化道不适患儿，男62例、女62例，中位年龄10.0（7.5~12.7）岁。85例（68.5%）患儿LHMBT阳性，其中小肠细菌过度生长（SIBO）的阳性率为24.2%（30/124）、产甲烷菌过度生长（IMO）的阳性率为63.7%（79/124），SIBO和IMO共同阳性为19.4%（24/124）。LHMBT阳性组（n=85）与阴性组（n=39）之间年龄分布差异有统计学意义（P<0.05），LHMBT阳性组>12~18岁占比较低。患儿消化道不适症状中腹痛最为常见（67.7%，84/124），其次为腹胀（25.0%，31/124）、便秘（18.5%，23/124）。与LHMBT阴性组相比，LHMBT阳性组患儿腹泻症状占比更低，差异有统计学意义（P<0.05）。63例患儿进行了胃肠镜检查，与LHMBT阴性组（n=16）患儿相比，LHMBT阳性组（n=47）回肠末端黏膜组织病理学提示绒毛短平以及隐窝减少的占比更高，差异有统计学意义（P<0.05）。结论 消化道不适患儿的LHMBT阳性率高，IMO的发生率高于SIBO。LHMBT阳性者回肠末端黏膜绒毛短平及隐窝减少更为常见。

Objective To summarize the application of the lactulose hydrogen-methane breath test (LHMBT) in children with gastrointestinal discomfort, and to analyze the clinical and endoscopic features of children with positive LHMBT. Methods A retrospective analysis was conducted on the clinical data of children hospitalized due to gastrointestinal discomfort in the Department of Gastroenterology of Shanghai Children's Hospital from August 2021 to October 2022. According to the LHMBT results, the children were classified into the LHMBT positive group and the LHMBT negative group, and the clinical characteristics of the two groups were compared. Among them, 63 children underwent gastrointestinal endoscopy, and their endoscopic and histopathological characteristics were analyzed. Results A total of 124 children with gastrointestinal discomfort were included, including 62 boys and 62 girls, with a median age of 10.0 (7.5-12.7) years. LHMBT was positive in 85 (68.5%) children. Among them, the positive rate of SIBO was 24.2% (30/124), the positive rate of IMO was 63.7% (79/124), and the co-positive rate of SIBO and IMO was 19.4% (24/124). The age distribution between the LHMBT positive and negative groups was statistically significant (P<0.05). The proportion of those aged 12-18 years in the LHMBT positive group was relatively low. Among the gastrointestinal discomfort symptoms of the children, abdominal pain was the most common (67.7%, 84/124), followed by abdominal distension (25.0%, 31/124) and constipation (18.5%, 23/124). Compared with the LHMBT-negative group, the proportion of children with diarrhea in the LHMBT-positive group was lower, and the difference was statistically significant (P<0.05). Among the 63 children who underwent gastrointestinal endoscopy, villous blunting and crypt loss in the terminal ileum were more frequently observed in the LHMBT positive group (n=47) than that in the LHMBT negative group (n=16), and the difference was statistically significant (P<0.05). Conclusions The positive rate of LHMBT in children with gastrointestinal discomfort is high, and the incidence of IMO is higher than that of SIBO. LHMBT positivity might correlates with villous blunting and crypt loss in the terminal ileum.