Fu's Subcutaneous Needling for Digestive System Diseases and Digestive–System–Related Symptoms: A Narrative Review of Clinical Evidence and Hypothesised Mechanisms

Floating needle therapy, also known as Fu’s subcutaneous needling (FSN), is a shallow subcutaneous needling technique that has been explored as an adjunctive approach for digestive system diseases and digestive-system-related symptoms. This narrative review summarizes current clinical evidence and discusses plausible but incompletely validated mechanisms. Existing clinical reports suggest that FSN, either alone or more commonly combined with conventional medication, moxibustion, biofeedback, massage, or rehabilitation therapy, is associated with improvement in symptom scores, gastrointestinal hormones, gut microbiota indicators, intestinal barrier-related markers, and postoperative gastrointestinal recovery in selected conditions. However, most available studies are small, single-center, short-term, and lack credible sham controls or blinded outcome assessment. Therefore, the independent contribution of FSN cannot be separated from co-interventions in many studies. Mechanistic evidence specific to FSN remains limited. Pathways involving subcutaneous mechanotransduction, Aβ/Aδ afferents, the brain–gut axis, vagal anti-inflammatory signalling, Piezo1/TRPV4, and α7 nicotinic acetylcholine receptors should be regarded as hypotheses extrapolated from related acupuncture, connective-tissue, and neurogastroenterology research rather than mechanisms directly confirmed in FSN studies. Current evidence supports cautious consideration of FSN as an investigational adjunctive therapy, but it is insufficient to support guideline-level recommendations. Future studies should use preregistered multi-centre randomized trials, credible sham-FSN controls, blinded outcome assessment, longer follow-up, and mechanism-linked endpoints.