Breath Gases, Gut Flora, and Immunity in Children With Constipation

Correlation Study on End-expiratory NO, H2S, H2, CH4, Intestinal Flora and Immune Function in Children With Constipation

Constipation is a common problem in children that can affect their daily life, school performance, and social activities. Researchers have found that the bacteria living in our intestines (called "gut microbiome") may play an important role in constipation. However, we still do not fully understand exactly how these bacteria affect constipation in children.

This study aims to explore whether the gases children breathe out-including nitric oxide (NO), hydrogen sulfide (H₂S), hydrogen (H₂), and methane (CH₄)-can tell us something about the bacteria in their guts. By comparing children with constipation to healthy children, we hope to find out:

Whether the gases in their breath are different Whether the types of bacteria in their guts are different Whether there is a relationship between breath gases and gut bacteria If we find clear connections, this could lead to a simple, non-invasive breath test that doctors can use to understand a child's gut health without the need for more invasive procedures.

Childhood functional constipation (FC) is a multifactorial syndrome with a global prevalence of approximately 9.5% among pediatric populations, accounting for up to 29% of functional gastrointestinal disorders. It significantly affects physical health, academic performance, and psychosocial development, with approximately 25% of affected children continuing to experience gastrointestinal symptoms into adulthood. While conventional factors such as diet, fluid intake, and psychological stress have been implicated, the precise pathophysiological mechanisms remain incompletely understood.

Emerging evidence highlights the critical role of the gut microbiome in regulating intestinal motility and visceral sensitivity through the microbiota-gut-brain axis. Microbial metabolites-including short-chain fatty acids (SCFAs), serotonin, bile acids, and gases (methane, hydrogen, hydrogen sulfide)-serve as key signaling molecules that influence enteric neurotransmission, smooth muscle contraction, and gastrointestinal transit time. Notably, hydrogen (H₂) and methane (CH₄) are exclusively of microbial origin (produced via anaerobic fermentation of carbohydrates by intestinal flora), while hydrogen sulfide (H₂S) is generated both endogenously and by sulfate-reducing bacteria. Nitric oxide (NO), though primarily endogenously produced, may also reflect intestinal inflammatory status and microbial metabolic activity.

The integration of breath gas analysis and metagenomic profiling offers a promising, non-invasive approach to elucidate host-microbe interactions in FC. However, systematic evaluations linking these four exhaled gases (NO, H₂S, H₂, CH₄) to the taxonomic and functional composition of the gut microbiome in constipated children remain scarce. This study is designed to bridge this knowledge gap, providing mechanistic insights and potentially establishing breath testing as a surrogate marker for gut dysbiosis in pediatric constipation.

Inclusion Criteria:

• Children aged 6 to 14 years, male or female.
• Legal guardian provides written informed consent.
• No use of antibiotics, probiotics, lactulose, antacids, or gastrointestinal prokinetic agents within 4 weeks prior to enrollment.
• For the constipation group: Clinical diagnosis of functional constipation according to Rome criteria, defined as meeting at least two of the following criteria for two consecutive months: (a) fewer than two bowel movements per week; (b) at least one episode of fecal incontinence per week; (c) history of massive fecal retention or posturing related to fecal retention; (d) history of painful or difficult defecation; (e) presence of a large fecal mass in the rectum; (f) passage of stools large enough to obstruct the toilet. Additionally, no enema or acute enteritis within 2 weeks prior to enrollment.
• For the healthy control group: No chronic digestive diseases or acute illnesses; no enema or acute enteritis within 2 weeks prior to enrollment.

Exclusion Criteria:

• Use of antibiotics, probiotics, lactulose, antacids, or gastrointestinal prokinetic agents within 4 weeks prior to enrollment (if not already excluded at screening).
• Clinically significant abnormalities in liver, kidney, neurological, respiratory, or coagulation function as determined by the investigator.
• Unstable vital signs.
• Presence of other underlying systemic diseases (e.g., metabolic, endocrine, or organic gastrointestinal disorders).
• Any other condition that, in the investigator's opinion, makes the participant unsuitable for enrollment.