Inside-Out Mechanism of Referred Visceral Pain: Protocol for a Systematic Review of Cutaneous Neurogenic Inflammation in Preclinical Animal Models of Visceral Diseases

Background Visceral diseases often lead to referred pain, but clinical management is challenging due to poor understanding of the underlying mechanisms. Prior preclinical studies have shown that experimental induction of visceral diseases in animal models can cause cutaneous neurogenic inflammation, as assessed by Evans Blue dye extravasation. Neurogenic inflammation is associated with increased pain sensitivity. Thus, these preclinical findings may provide important mechanistic insights into the relationship between visceral diseases and referred somatic pain. Objective The objective of this systematic review is to synthesize evidence on cutaneous neurogenic inflammation and corresponding somatic pain sensitivity in preclinical animal models of visceral diseases, to lay out the current state of knowledge, and to identify any gaps or limitations to be addressed in future research on this topic. Methods This systematic review will be conducted, following the PRISMA-P (Preferred Reporting Items for Systematic Review and Meta-Analysis Protocol) guidelines. The literature search will be conducted in MEDLINE (Ovid), Embase, and Web of Science, using search terms related to cutaneous neurogenic inflammation and animal models of visceral diseases. Two investigators will independently screen and select studies meeting the eligibility criteria. For each included study, a predefined template will be used to extract relevant information, including the details of animal species and strains, visceral disease models, outcomes related to the distribution and extent of Evans Blue dye extravasation, and other pertinent findings and methodologies. Quality assessments will be independently performed by two investigators using the Risk of Bias tool from the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE). A qualitative summary of the findings will be provided for outcomes related to the extent and distribution of Evans Blue dye extravasation. Results As of August 2025, a total of 536 records were identified from database search, and 13 studies met the eligibility criteria to be included in the review. Results from data extraction and quality assessments are expected to be published in fall 2026. Conclusions Prior preclinical animal studies have investigated cutaneous neurogenic inflammation as a potential mechanistic outcome of referred visceral pain. The proposed review will be the first to summarize research findings and study quality on this topic. This will be an important step toward gaining insights into one of the potential mechanisms underlying referred visceral pain and informing future research in this area. International Registered Report Identifier (IRRID) DERR1-10.2196/67852