Scar Defects (Niche and Isthmocele)
Charles E. Miller
William E. Gibbons
GENERAL PRINCIPLES
Over the past 15 years, a new term for an old condition has appeared in the literature. The term “isthmocele” is used to describe a reservoir-like pouch or “notch” defect in the anterior wall of the uterine isthmus located at the site of a previous cesarean (c/s) scar (1). The incidence reported in the literature varies from 56% to 84% (2). For diagnosis, some report that office hysteroscopy is superior to ultrasound (3). Others suggest that newer 3D ultrasound instruments are very good at making the diagnosis, although the volume of the pouch may be better appreciated when the pouch is full of fluid.
Risk factors have been evaluated in various publications and include a longer duration of labor, stage of labor at the time of c/s, number of previous surgeries, occurrence of a previous vaginal delivery, weeks of gestation at c/s, and a retroverted uterus (4). Some have suggested that a lower position of the c/s incision, incomplete closure of the hysterotomy, early adhesions of the uterine wall, and even a genetic predisposition may play a role (5).
The majority of women with an isthmocele are asymptomatic. The pouch in larger defects may fill with menstrual blood and slowly drain over the days following normal menstrual flow, with resultant postmenstrual bleeding. Therapy to eliminate the pouch is very effective. Chronic pelvic pain is described in some women and evidence of this relationship is strengthened by the effective resolution with therapy (6). More concerning is the possibility that the defect will lead to tissue dehiscence, a pregnancy in the scar, or abnormal placentation such as a placenta accrete (7).
Some authors attribute secondary infertility to isthmoceles, and although there is evidence in the literature of surgical repair being utilized to treat infertility, there is little evidence to support the role of isthmocele surgery and there are no randomized trials to demonstrate that infertility is owing to the isthmocele and that treatment is beneficial (8). As well, a review of the literature does not demonstrate a reduction in fertility after c/s (9).
This chapter reviews the literature and provides a roadmap for the treatment of isthmoceles.
SURGICAL MANAGEMENT
Surgical treatment: There is no general agreement about which surgical approach may be best. Although there are multiple studies evaluating hysteroscopic treatment of symptomatic isthmoceles, there is a paucity of literature evaluating either a laparoscopic or vaginal approach. The following review of the literature suggests guidance but no clear agreement regarding comparative efficacy of a hysteroscopic, laparoscopic, or vaginal approach.
According to an excellent review by Togas Tulandi et al. entitled, “Emerging manifestations of cesarean scar defect in reproductive-aged woman” published in the Journal of Minimally Invasive Surgery in October 2016 (10), successful treatment of abnormal uterine bleeding was noted in 59% to 100% of hysteroscopic repair cases, 89% to 93.5% of vaginal repair cases, and 86% of laparoscopic repair cases. This same article reported that hysteroscopic management yielded pregnancy rates of 78% to 100%, whereas an 86% pregnancy rate was noted with laparoscopic repair.
Hysteroscopic Approach to the Symptomatic Isthmocele
Hysteroscopic treatment when abnormal uterine bleeding is present has been addressed in multiple studies. In 2005, Fabres et al. published a retrospective cohort study involving 24 patients (11). Twenty of the patients (84%) noted improvement in bleeding. Surgical intervention consisted of resection of the lower flap (cervical side of the defect—Figure 2.2.1) and then fulguration of the superficial dilated vessels of the endometrial glands with a monopolar resectoscope at 60 watts. Three years later, a prospective trial was reported by Gubbini et al. (12). All 26 patients (100%) noted correction of postmenstrual bleeding at 12 and 24 months. As in Fabres study, the thickness of the myometrium at the top of the isthmocele defect was not mentioned. In 2009, Chang et al. reported that in 14 of 22 patients (63%), bleeding had normalized (13). In this study, myometrium ≥2 mm was required for a patient to undergo a hysteroscopic approach. A monopolar loop was used at 80 W cutting current to shave the lower flap and 50 W coagulation current to desiccate the vessels and glands within the defect.
In 2011, in the Gynecological Endocrinology Journal, Florio et al. published a retrospective, case-controlled study comparing hysteroscopic resection to hormonal modulation in treating menstrual disorders related to isthmocele (14). Group A (19 patients) was treated via hysteroscopic surgery, and Group B (20 patients) via hormonal manipulation. Both sides of the isthmocele were shaved utilizing a monopolar loop with pure cutting current. The top of the isthmocele was desiccated using a roller ball. Resolution of abnormal bleeding
and pain was significantly greater in group A, whereas all patients noted a reduction of bleeding and pain.
Figure 2.2.1. A: Pre. Shave cervix side of isthmocele. B: Post. This increases efflux of fluid from the cervix, rather than the collection in the endometrium.
Raimondo et al. noted that of the 120 patients studied, 104 (84%) had a significant reduction of abnormal uterine bleeding (6). This prospective study included 116 patients complaining of postmenstrual bleeding. To be a candidate for hysteroscopic surgery, a patient had to have myometrium ≥4 mm. The monopolar resectoscope was used to shave the lower edge of the defect with the base desiccated with the monopolar loop. One month after the surgery, 96 patients (80%) had complete symptom relief.
With regard to fertility concerns, studies of the hysteroscopic treatment of the isthmocele are less numerous and robust. Fabres et al. in their 2005 study reported nine pregnancies in 11 patients (11). Gubbini et al. published two prospective cohort studies, reporting on 9 patients in 2008 (12) and 41 patients in 2011 (15). All women underwent treatment with the monopolar resectoscope. Shaving of both the superior and inferior edges with a cutting loop using pure cut current was followed by roller ball desiccation of the top of the isthmocele. In the initial study, 73% achieved pregnancy whereas all 41 patients in the latter study were successful in achieving pregnancy. It must be noted that none of these studies described the size of the isthmocele, whether fluid was noted in the cavity, or what percentage of patients had fertility issues prior to pregnancy.
In the July-September 2019 issue of the International Journal of Fertility and Sterility, Vegas Carrillo de Albornoz et al. described a prospective case series involving 38 women (16). All patients had abnormal uterine bleeding, 42% reported pelvic pain, and 29% reported secondary infertility. If the myometrial thickness at the base of the isthmocele was <2.5 mm, a hysteroscopic approach was not performed. In appropriate candidates, a 9-mm loop resectoscope was utilized to shave the lower wall of the isthmocele to the level of the cervix followed by desiccation of the base. Within 1 month, 87.5% had normalized bleeding. Three of seven women completed the first year of follow-up and achieved pregnancy [43%].
Vaginal Approach to the Symptomatic Isthmocele
The vaginal approach to isthmocele appears to be more often performed in Asia than elsewhere. In 2012, Luo et al. published a retrospective study involving 42 patients undergoing vaginal isthmocele repair secondary to abnormal uterine bleeding (17). After injection of the vesicocervical space with adrenaline (1:2,000), the mucosa of the vaginal wall was incised and the vesicocervical space opened. Consistent with vaginal hysterectomy, the bladder was mobilized off the uterus. The uterine sound is used to confirm proper closure and to be certain that no sutures incorporated the posterior wall. Three or four interrupted Polydioxanone “O” sutures (PDS—Ethicon, Somerville, NJ). A second layer of continuous or interrupted sutures was now placed. Approximation of bladder peritoneum was then performed, as was a final layer approximating the cervix and vagina. Nearly 93% (39 patients) noted a significant reduction of abnormal uterine bleeding. In a subsequent retrospective study, Zhang compared the transvaginal repair in 65 patients with a laparoscopic approach in 59 patients performed because of abnormal bleeding (18). An 89% success rate was noted in the transvaginal repair group versus 86% in the laparoscopic repair group. Shorter operative time, as well as a reduced time of hospitalization, was noted in the vaginal group. The technique of vaginal repair was similar to that of Luo, except the initial repair of absorbable “O” interrupted figure-of-eight sutures was followed by a layer of mattress absorbable sutures. The initial steps in the laparoscopic approach involved an incision into the vesicouterine fold of the peritoneum with the ultrasound knife; the bladder was then mobilized off the anterior uterine wall and cervix. Hysteroscopy was performed to localize the size and location of the isthmocele. Under the guidance of the hysteroscope, the defect was visualized and subsequently resected with the ultrasound knife. The uterus was repaired in three layers utilizing absorbable sutures placed continuously. Layer 1 was a full-thickness closure of the uterus. Layer 2 consisted of an imbricating suture. Finally, the third layer repaired the vesicouterine peritoneum.
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