Comprehensive Assessment System for Fallopian Tube Function and Clinical Study on Individualized Treatment Strategies

. Background and Rationale Tubal factor infertility (TFI) accounts for approximately 25%-35% of female infertility cases worldwide, predominantly caused by hydrosalpinx, tubal obstruction, peritubal adhesions, and structural abnormalities. Although assisted reproductive technologies (ART) have advanced considerably, tubal pathology-particularly hydrosalpinx-compromises IVF outcomes through embryotoxic fluid backflow and reduced endometrial receptivity. Concurrently, shifting demographic trends and fertility policy changes have increased patient demand for surgical restoration of natural fertility as an alternative to ART.

Recent innovations in reproductive surgery, including refined four-step fimbrioplasty and modified tubotubal anastomosis, have improved pregnancy rates. However, two major challenges persist: (1) high postoperative recurrence of adhesions and hydrosalpinx, and (2) significant ectopic pregnancy risk. More critically, the lack of a standardized, objective, and comprehensive system for evaluating tubal functional reserve severely limits appropriate surgical candidate selection and outcome prediction. Current clinical practice relies heavily on hysterosalpingography (HSG), which provides only anatomical patency information without assessing mucosal health, peritubal environment, or functional integrity.

This study addresses these gaps by proposing a multi-dimensional, multi-temporal assessment framework integrating imaging, molecular biomarkers, and intraoperative findings. It further aims to optimize surgical techniques using a novel anti-adhesion biomaterial and to develop machine learning-based predictive models to guide individualized treatment decisions for TFI patients.

Study Design Overview

The investigation comprises three integrated components:

Component 1 (Diagnostic Accuracy Study) : A prospective, single-center diagnostic trial enrolling 120 TFI patients. Each participant serves as their own control, undergoing both the novel multi-dimensional assessment strategy (Strategy A) and conventional HSG-only strategy (Strategy B), with intraoperative laparoscopy with chromopertubation as the reference standard.

Component 2 (Interventional Trial with Historical Control) : A single-arm interventional trial with historical controls, enrolling 120 patients receiving optimized laparoscopic surgery with chitosan hydrogel application (experimental group), compared with 120 historical controls who underwent conventional surgery without the novel anti-adhesion intervention. The primary endpoint is the 12-month natural pregnancy rate.

Component 3 (Prediction Model Study) : A bidirectional cohort study comprising a retrospective development cohort (~650 patients, 2010-2024) and a prospective validation cohort (~200 patients, 2026-2028), developing and validating logistic regression and XGBoost machine learning models for predicting 12-month natural pregnancy following tubal surgery.

Component 1: Tubal Function Assessment System-Technical Details 3.1 Preoperative Multi-Modal Imaging and Biomarkers

Quantitative HSG Scoring: All participants undergo standardized oil-based contrast HSG (Lipiodol). Beyond patency assessment, systematic scoring includes: (a) fimbrial morphology (mucosal bridges, accessory ostia); (b) ampullary morphology (diverticula, dilatation, strictures); and (c) contrast spillage pattern (uniform vs. localized peritoneal dispersion) as an indirect adhesion indicator. A 0-3 graded scoring system is applied, incorporating hydrosalpinx diameter, tubal wall rigidity, and adhesion extent.

Three-Dimensional Vascular Ultrasound: Transvaginal 3D power Doppler ultrasound quantifies tubal vascularization and perfusion. Color Doppler flow imaging parameters-peak systolic velocity (PSV), end-diastolic velocity (EDV), resistance index (RI), and pulsatility index (PI)-are measured at the tubal wall and fimbrial regions. Fimbrial blood flow is semi-quantitatively graded as Grade 0 (no flow), Grade 1 (sparse punctate), or Grade 2 (abundant linear/reticular).

Molecular Biomarkers: Fasting venous blood samples are collected preoperatively. Serum CA125, VEGF, and IL-6 levels are measured using standardized ELISA protocols, selected for their established roles in peritoneal inflammation, angiogenesis, and endometriosis-associated tubal pathology.

3.2 Intraoperative Reference Standard and Integrated Scoring

Laparoscopic Evaluation: Systematic pelvic inspection is performed, with pelvic adhesions quantified using the revised American Fertility Society (r-AFS) classification. Tubal assessment includes serosal status, morphology (dilatation, tortuosity, hydrosalpinx degree), and fimbrial architecture. Chromopertubation with methylene blue classifies fimbrial efflux patterns as free flow, impaired flow, or no flow.

Hysteroscopic and Salpingoscopic Evaluation: Diagnostic hysteroscopy assesses uterine cavity and tubal ostia. For tubes with abnormal chromopertubation, fiberoptic salpingoscopy evaluates mucosal fold architecture, intraluminal adhesions, polyps, vasculature, and staining patterns, generating an intraluminal pathology score.

Integrated Composite Score: All quantitative data (HSG score, ultrasound PI/RI/flow grade, biomarkers, r-AFS score, salpingoscopy score) are entered into a unified electronic case report form. A weighted composite tubal function score is derived via exploratory factor analysis, categorizing dysfunction into Grades I-V (mild to severe), with diagnostic performance evaluated against intraoperative laparoscopy as the reference standard.

Component 2: Surgical Technique Optimization-Technical Details 4.1 Anti-Adhesion Biomaterial: Chitosan Hydrogel

The investigational device is medical-grade chitosan hydrogel (NMPA Class III-approved). Its multi-mechanistic action includes:

Physical Barrier: Forms a transparent, flexible gel film over surgical surfaces, mechanically isolating traumatized tissue planes to prevent fibrin deposition.

Mild Hemostasis: Positively charged chitosan interacts with negatively charged erythrocyte membranes, promoting platelet aggregation and reducing hematoma formation-a key adhesion initiator.

Biological Modulation: Selectively promotes epithelial and endothelial cell proliferation while inhibiting fibroblast overgrowth via downregulation of TGF-β1 and other pro-fibrotic cytokines, reducing pathological scar formation.

Mucosal Regeneration: Degradation products (N-acetylglucosamine and glucosamine) serve as substrates for normal tissue growth, promoting tubal mucosal epithelial repair.

4.2 Optimized Surgical Procedure (Experimental Group)

The procedure is performed under combined laparoscopic and hysteroscopic guidance, with the following key modifications:

Pelvic Adhesiolysis: Precise adhesiolysis using electrosurgery or cold scissors restores normal tubo-ovarian anatomy, with meticulous hemostasis.

Fimbrioplasty/Salpingostomy: A modified "four-step" fimbrioplasty is performed for hydrosalpinx, with chromopertubation confirming patency.

Combined Laparoscopic-Hysteroscopic Recanalization: Under hysteroscopic guidance, a hydrophilic-coated guidewire is advanced through the tubal lumen under direct laparoscopic visualization until the tip is visible at the fimbrial end. Critical modification: Prior to insertion, chitosan hydrogel is uniformly applied to the distal 10-15 cm of the guidewire, enabling direct intraluminal deposition of the anti-adhesion agent during recanalization.

Comprehensive Anti-Adhesion Application: (a) 3-5 mL of injectable chitosan hydrogel is infused through the guiding catheter to fully distend the tubal lumen; (b) chitosan hydrogel is uniformly sprayed over the reconstructed fimbrial end, the entire tubal serosal surface, and all other pelvic surgical surfaces (ovaries, uterine wall, pelvic sidewall).

4.3 Control Group Procedure (Historical)

Control patients underwent conventional tubal surgery (salpingostomy or recanalization) without the guidewire-mediated intraluminal chitosan application. Anti-adhesion material, if used, was applied only to the peritoneal cavity and peri-tubal surfaces, without targeted intraluminal instillation.

Component 3: Prediction Model Development and Validation 5.1 Candidate Predictors

Candidate predictors are selected based on biological plausibility and clinical relevance, encompassing five domains:

① Demographic and baseline characteristics (age, BMI, infertility type and duration);

② Ovarian reserve (baseline AMH);

③ Tubal pathology characteristics (preoperative HSG score, 3D ultrasound parameters [PI, RI, flow grade], intraoperative composite tubal function score, r-AFS pelvic adhesion score);

④ Molecular biomarkers (serum VEGF, IL-6, CA125);

⑤ Surgical factors (procedure type: salpingostomy vs. recanalization vs. combined).

5.2 Model Development and Validation Strategy

Model Development: The development cohort (n=650) is randomly partitioned into training (70%) and internal test (30%) sets.

Logistic Regression: Variable selection proceeds via univariate analysis (P<0.1 for entry) followed by LASSO regression with 10-fold cross-validation to select the optimal penalty parameter (λ), yielding the most parsimonious model.

XGBoost Machine Learning Model: Implemented using all candidate variables, with grid search and cross-validation for hyperparameter tuning, and built-in feature importance ranking.

Model Validation:

Internal Validation: Bootstrap resampling (1,000 iterations) is performed on the training set to correct for optimism and assess stability.

External Validation: Temporal validation using the prospective single-center cohort (n=200) and spatial validation using multi-center prospective data assess generalizability across time and institutions.

Performance Evaluation: Discrimination is assessed by AUC with 95% CIs, along with accuracy, sensitivity, specificity, and predictive values at the optimal Youden-index threshold. Calibration is evaluated via calibration plots with loess smoothing and the Hosmer-Lemeshow test. Clinical utility is quantified using decision curve analysis (DCA) across a range of threshold probabilities.