Hysteroscopic niche resection can effectively reduce the niche volume, increase residual myometrial thickness, and improve postmenstrual spotting symptoms

To compare the anatomical changes of the uterine niche in women before and after hysteroscopic niche resection (HNR) and to investigate the correlation between these changes and the improvement in postoperative spotting symptoms by thin-slice MRI.

This prospective observational study enrolled women with symptomatic uterine niches between June 2019 and February 2024. All participants underwent thin-slice magnetic resonance imaging (MRI) before and after HNR. We assessed the effective rate of postoperative spotting at the 6-month follow-up (effective treatment was defined as a reduction of at least 50% in spotting days relative to baseline during the 6-month follow-up period) and the pre- and post-HNR anatomical indicators.

A total of 108 women were included in the study. Six months after HNR, 70.4% (76/108) of women experienced at least a 50% reduction in spotting days from baseline. Residual myometrial thickness (RMT) significantly increased by 1.9 ± 2.2 mm (p < 0.01). The volume of niche significantly decreased, with a median reduction rate of 38.5% (IQR 8.5–88.2%) (p < 0.01). Based on the ROC curve, a cut-off value of 50 mm² for volume was identified as an optimal threshold for subclassifying large niches and small niches, according to treatment efficacy. The reduction in niche volume was more pronounced in the small niche group compared to the large niche group, with median reduction rates of 51.9% (IQR 13.5–100.0%) and 12.4% (IQR −15.4–43.9%), respectively (p < 0.01). There is an interesting finding that most cases in the anatomical failure group (those with an enlarged niche) had a preoperative volume of ≥ 50 mm² (19.2%, p < 0.01). Furthermore, the effective treatment group exhibited a more significant increase in RMT and a greater reduction in niche volume after HNR compared to the ineffective group. Multivariate logistic regression analysis indicated that small niches [OR 16.85 (3.36–84.47), p < 0.01] and greater reductions in niche volume [OR 1.14 (1.07–1.21), p < 0.01] were associated with effective treatment.

HNR is a promising approach for managing postmenstrual spotting, especially in treating small uterine niches (volume < 50 mm²). After HNR, RMT increases, and niche size decreases slightly.