Why do niches develop in Caesarean uterine scars? Hypotheses on the aetiology of niche development

Abstract

Caesarean section (CS) results in the occurrence of the phenomenon ‘niche’. A ‘niche’ describes the presence of a hypoechoic area within the myometrium of the lower uterine segment, reflecting a discontinuation of the myometrium at the site of a previous CS. Using gel or saline instillation sonohysterography, a niche is identified in the scar in more than half of the women who had had a CS, most with the uterus closed in one single layer, without closure of the peritoneum. An incompletely healed scar is a long-term complication of the CS and is associated with more gynaecological symptoms than is commonly acknowledged. Approximately 30% of women with a niche report spotting at 6–12 months after their CS. Other reported symptoms in women with a niche are dysmenorrhoea, chronic pelvic pain and dyspareunia. Given the association between a niche and gynaecological symptoms, obstetric complications and potentially with subfertility, it is important to elucidate the aetiology of niche development after CS in order to develop preventive strategies. Based on current published data and our observations during sonographic, hysteroscopic and laparoscopic evaluations of niches we postulate some hypotheses on niche development. Possible factors that could play a role in niche development include a very low incision through cervical tissue, inadequate suturing technique during closure of the uterine scar, surgical interventions that increase adhesion formation or patient-related factors that impair wound healing or increase inflammation or adhesion formation.

Small Size Resectoscope in Isthmocele Repair: Case Report

“…Several hypotheses may explain CSD development: a very low incision through the cervical tissue, impaired wound healing, adhesion formation, inadequate suturing or incomplete closure of the uterine scar due to endometrial closure technique [8]. A recent meta-analysis reported a similar incidence of CSD in women who received single-layer closure (25.5% vs 43.0%; RR 0.77, 95% CI 0.36 to 1.64; 5 trials; 350 participants; low quality of evidence) compared to women who received double-layer closure [9].…”

Repair of a First Trimester Uterine Dehiscence with Continuation of Pregnancy: Case Report

“…15 While the number of the cases in women who become pregnant after the repair of post-growing niches, is limited, previa and dehiscence wasn't reported. 13 As the repair of the niches presenting abnormal uterine bleeding symptoms, is being suggested, the pre-pregnancy repair should also be considered in terms of pregnancy complications in larger niches.…”

When and how should we treat cesarean scar defect — isthmocoele?

“…First, concerns the location of the incision that was made too low in the cervical part of uterus, that contains mucous glands. Mucus produced in the time of wound healing may dilate the sutured edges of the myometrial tissue [18]. The confirmation for this theory was the study which stated that isthmocoele was found more frequently in patients who had caesarean section performed on maximal dilation, when finding proper place between uterus and cervix is more difficult [19].…”

“…The authors also state that it may be the reason for recurrence of isthmocoele in 5% of patients after repairing surgery [20,21]. There are some other theories involving obesity as a risk factor, but the mechanism of action is unknown [18,22].…”