Techniques and Clinical Outcomes of Catheter-Directed Sclerotherapy Using Ethanol for Ovarian Endometriomas

Ovarian endometriomas are cystic structures surrounded by endometrial tissue that often contain old menstrual blood and other debris. They are present in up to 44% of females with endometriosis and can cause symptoms such as dysmenorrhea, pelvic pain, abnormal uterine bleeding, and infertility ( 1 2 ). A recent meta-analysis reported that medical therapies, such as combined oral contraceptives, progestins, and gonadotropin-releasing hormone agonists, can manage pain and reduce endometrioma volume by an average of 55% (95% confidence interval, 40%–71%) ( 3 ), although the effects vary among individuals. However, endometrioma recurrence is common after the discontinuation of medical therapy ( 4 ). Surgical cystectomy, often laparoscopic, is the standard treatment for ovarian endometriomas. However, this procedure can lead to a decline in ovarian reserve, with a reduction rate of 39.5% in unilateral cases and 57.0% in bilateral cases ( 5 ), due to excessive electrocoagulation of normal ovarian tissues surrounding the cyst ( 6 ). Ultrasonography-guided aspiration and sclerotherapy were introduced as alternative ovarian endometrioma treatment in 1988 ( 7 ). This combined technique aims to destroy the epithelial lining of the cyst, leading to inflammation, fibrosis, and eventual cyst regression ( 6 ). However, the recurrence rate following needle-directed sclerotherapy is relatively high at 13.8% ( 6 ), primarily due to insufficient aspiration of cyst content through 16–19 G needles. To address this limitation, catheter-directed sclerotherapy was introduced in 2018 ( 8 ). This technique utilizes an 8 Fr catheter with a lumen cross-sectional area at least four times larger than that of 16–19 G needles, allowing for more sufficient aspiration and potentially more effective sclerotherapy.

The rate of technical success—defined as successful insertion of the catheter, drainage of the content, and filling and draining of alcohol for the prescribed time—has been reported to reach 100% ( 8 9 10 ). However, the success rate may be slightly lower in the case of a two-session procedure ( 2 ). Most cases show a reduction in volume, with an average volume reduction ratio of 96.4% at 6 months ( 2 ). Several studies have demonstrated that catheter-directed sclerotherapy effectively preserves ovarian function, as measured by serum AMH levels ( 2 8 9 10 11 12 ). AMH levels have been shown to remain stable after the procedure, even in patients with already diminished ovarian reserve and those with recurrence, large cysts, or bilateral lesions ( 2 8 9 10 11 12 ). These results support the use of sclerotherapy in various clinical scenarios, including those in which repeat surgery poses a risk of further compromising ovarian function. Collectively, these findings suggest that catheter-directed sclerotherapy not only achieves meaningful cyst volume reduction but also minimizes damage to the ovarian cortex, making it a favorable option for women seeking to preserve their reproductive potential. A meta-analysis reports a 13.8% recurrence rate after needle-directed sclerotherapy ( 6 ), and a recurrence rate of 11.36% after needle-directed sclerotherapy is observed in a retrospective study comparing the procedure with laparoscopic cystectomy ( 13 ). In contrast, a recurrence rate of 0% is reported in other studies of catheter-directed sclerotherapy ( 2 8 9 10 ). This discrepancy is likely due to the effective destruction of the cyst epithelial lining that is induced by the complete evacuation of the cyst content, followed by alcohol sclerotherapy. Despite the lack of studies specifically evaluating the efficacy of sclerotherapy in recurrent endometriomas are limited, most existing evidence does not suggest a significant difference in outcomes between primary and recurrent cases. In contrast, repeat surgical intervention for recurrent endometriomas can be challenging due to concerns regarding postoperative adhesions and further declines in ovarian function ( 9 ). Therefore, sclerotherapy may be favorable for these patients, offering a minimally invasive alternative with a potentially lower risk of ovarian reserve decline. Pain may occur when alcohol is injected; it varies significantly among patients, ranging from no pain at all to extreme pain that necessitates suspension of the procedure. Given the primary mechanism of pain, which is inflammatory response due to cell damage caused by alcohol, pain is generally not considered a procedure-related complication ( 14 ). In a large cohort study involving 323 patients, transient hypotension and bradycardia were observed in 3.4% of patients and were successfully managed with conservative treatment ( 15 ). Another possible complication following needle-directed sclerotherapy is infection, with a reported incidence of up to 2.3% ( 6 10 13 ). Bleeding is another potential complication reported in studies on needle-directed sclerotherapy ( 6 ).

Transvaginal and transabdominal accesses are the two main approaches for sclerotherapy. Transabdominal access may not be possible if intervening structures such as the bowel, bladder, or blood vessels are present and passing through the peritoneum increases peritonitis or catheter dislodgement risks; thus, transvaginal access is generally preferred. However, in cases where high-risk structures such as blood vessels exist between the endometrioma and US probe, or if the patient refuses transvaginal access because of concerns about virginity, transabdominal access can be considered ( Fig. 1 ). The technical steps involved in transvaginal access are summarized in Fig. 2 . Intravenous sedoanalgesia with 25 mg pethidine hydrochloride (Hana Pharm. Co., Seoul, Korea) and 50 µg fentanyl (Hanlim Pharm. Co., Seoul, Korea) is administered. After placing the patient in the lithotomy position, the vagina is sterilized using a 0.5% chlorhexidine gluconate solution (Hexitane 0.5%; Firson, Cheonan, Korea). A US probe, equipped with an in-plane endocavitary needle guide (EVN4-9, Aspen Surgical, Caledonia, MI, USA) for accurate targeting, is then inserted into the vagina. After locating the endometrioma, the cyst is punctured using an 18 G, 20-cm Chiba biopsy needle (Cook, Bloomington, IN, USA). A 0.035-inch hydrophilic guidewire (Terumo, Tokyo, Japan) is advanced into the lesion under fluoroscopic guidance, and the needle is replaced with a 7 or 8.5 F pigtail catheter (Dawson–Mueller Drainage Catheter, Cook). After complete aspiration of the chocolate-colored content, saline irrigation is performed to ensure thorough removal of the cyst material. The cyst is then filled with 5–20 mL of a water-soluble nonionic contrast medium (Iobitridol, Xenetix 300 [300 mg I/mL], Guerbet, Villepinte, France), depending on the size of the endometrioma, to rule out potential spillage into the pelvic cavity. After aspirating the contrast medium, the cyst is irrigated with lidocaine to alleviate discomfort during sclerotherapy. When multiple endometriomas are present, catheters can be inserted individually into each endometrioma during a single session, allowing for simultaneous treatment ( Fig. 3 ). Subsequently, 99% ethanol is introduced (25%–50% of the aspirated volume, up to a maximum of 100 mL for patient safety), depending on the patient’s pain tolerance. The patient is instructed to change position (i.e., supine, bilateral decubitus, and prone) every 5 minutes with the catheter clamped to maximize ethanol contact with the endometrioma wall. After 20 minutes, the ethanol is aspirated as thoroughly as possible. If the procedure is planned for a single session, the catheter is removed, and the area is sterilized. However, for a two-session procedure, the catheter is clamped and left in place overnight for the second session the following day, with the patient monitored in the ward. On the second day, after confirming the absence of leakage, the same procedure is repeated, instilling the same volume of ethanol for 20 minutes. After the second session, the catheter is removed, and the area is sterilized. If contrast medium spillage is detected ( Fig. 4 ) or if the patient experiences significant pain during the procedure, sclerotherapy is immediately suspended. To rule out malignancy, the aspirated fluid is sent for cytological examination to detect any atypical cells.

The most appropriate indications for sclerotherapy are reduced ovarian reserve, as indicated by anti-Müllerian hormone (AMH) levels <2 mg/mL, or recurrent endometriomas following surgery. Endometriomas ≥3 cm in diameter are recommended since the size allows a smoother insertion of the guidewire and subsequent catheter placement. If a solid lesion is observed within the cyst on ultrasonography, the risk of malignancy should be evaluated before the procedure. Additionally, the procedure should be contraindicated in patients with a history of gynecologic malignancy, active inflammation or infection, or an abnormal coagulation profile.