Ovarian endometriomas are common cystic lesions that can cause chronic pelvic pain and infertility. While laparoscopic cystectomy is the standard surgical treatment, it often leads to a significant decline in ovarian reserve due to the removal of healthy ovarian tissue and excessive electrocoagulation. Catheter-directed sclerotherapy (CDS) with ethanol has emerged as an effective, minimally invasive alternative that achieves high technical success while preserving ovarian function [1,2].

CDS is particularly indicated for patients with a reduced ovarian reserve, typically indicated by anti-Müllerian hormone (AMH) levels <2 ng/mL. It is also highly recommended for patients with recurrent endometriomas following previous surgery [1]. Cysts ≥3 cm in diameter are ideal to facilitate smoother guidewire insertion and catheter placement [2]. Contraindications include suspected gynecologic malignancy, active pelvic infection, or abnormal coagulation profiles.

While recent literature suggested that transvaginal access may be a risk factor for technical failure due to the inherent complexity of deep-seated lesions and the operator's learning curve [3], we still prefer this route as the primary approach. Its proximity to the pelvic floor and superior image resolution allow for precise targeting, provided the operator is sufficiently experienced in endocavitary procedures [1,4].

This alternative is considered if high-risk structures like blood vessels lie between the endometrioma and the vaginal probe, or if the patient prefers it for personal reasons (e.g., preservation of virginity). However, this route may be technically challenging or contraindicated if there is no safe window; for instance, when the bowel or other vital organs are positioned along the needle path, increasing the risk of peritoneal or visceral injury.

Intravenous sedoanalgesia is administered using 25 mg pethidine hydrochloride (Hana Pharm. Co. Ltd., Seoul, Korea) and 50 μg fentanyl (Hanlim Pharmaceutical Co. Ltd., Seoul, Korea). Following placement in the lithotomy position, the vagina is disinfected with 0.5% chlorhexidine gluconate solution (Hexitane 0.5%, Firson, Cheonan, Korea). Following the insertion of a vaginal speculum, an ultrasound probe equipped with an in-plane endocavitary needle guide (EVN4-9, Aspen Surgical, Caledonia, MI, USA) is inserted to facilitate precise targeting. The use of a 7-F or 8.5-F catheter (Dawson-Mueller Drainage Catheter, Cook Medical, Bloomington, IN, USA) is crucial, as it provides a lumen cross-sectional area significantly larger than conventional needles, allowing for the effective aspiration of thick, highly viscous "chocolate" contents often found in these cysts [1,2]. To further optimize the drainage efficiency, the existing side holes of the catheter are occasionally enlarged using surgical scissors prior to insertion. For example, in cases showing T2 dark signal intensity on pre-procedural MRI, which is a significant risk factor for technical failure due to extremely high viscosity [3], this technical modification is combined with repeated saline irrigation to dilute the thick chocolate content, eventually allowing for the complete aspiration of even the most tenacious materials.

1. Puncture and catheterization: Under ultrasound guidance, the cyst is punctured with an 18-gauge Chiba needle (Cook Medical). A 0.035-inch hydrophilic guidewire (Terumo, Tokyo, Japan) is then advanced into the lesion [2]. To minimize resistance, the metal inner stylet is first advanced alone over the guidewire to pre-dilate the track through the tough vaginal wall or adherent tissues. Its superior stiffness ensures more effective penetration than plastic dilators. The pigtail catheter is then assembled with the stylet and introduced as a unit, preventing kinking and ensuring seamless placement despite significant tissue resistance. Notably, CDS enables the mechanical breakdown of internal septa via guidewire manipulation, converting multiloculated cysts into a single cavity. This maneuver maximizes ethanol contact, thereby enhancing the efficacy of sclerotherapy for complex, multiseptated lesions [4].

2. Aspiration and irrigation: The content is completely aspirated, followed by saline irrigation until the return is clear [1].

3. Contrast injection: Before injecting the sclerosant, 5–20 mL of a nonionic contrast medium is instilled under fluoroscopy to rule out any leakage into the pelvic cavity [1,2].

4. Ethanol sclerotherapy: 99% ethanol (Taiwan Biotech Co., Ltd., Taoyuan, Taiwan) is instilled, typically 50% of the aspirated volume. While conventional protocols often suggest a maximum of 100 mL for safety, there is no strictly defined upper limit, and up to 150 mL can be administered without significant complications based on the operator's experience and cyst size. The patient changes position every 5 minutes for 20 minutes to maximize ethanol contact with the cyst wall. After the dwell time, the ethanol must be completely re-aspirated [2].

5. Two-session protocol: Although not a universal standard, a two-session protocol can be performed to minimize recurrence, particularly for large cysts (e.g., ≥10 cm) or those with internal septa where a single session may be insufficient. In this approach, the catheter is clamped and left in situ overnight after the first session. The same sclerotherapy procedure (ethanol instillation, positioning, and re-aspiration) is repeated the following day. The catheter is finally removed under fluoroscopic guidance to prevent catheter kinking only after the completion of the last re-aspiration in the final session [1,2].

– Volume reduction: CDS demonstrates a high-volume reduction ratio, reaching an average of 96.4% at 6 months post-procedure [2].

– Ovarian reserve preservation: Studies have shown that post-procedural AMH levels remain stable without significant decline, confirming that CDS spares the healthy ovarian cortex [2,5].

– Low recurrence: While needle-directed sclerotherapy has a reported recurrence rate of around 13.8%, CDS has achieved recurrence rates as low as 0% in prospective cohorts [1,2].

CDS with ethanol is a safe and effective treatment for ovarian endometriomas. Its ability to provide superior cyst drainage and prolonged ethanol contact makes it highly effective in reducing recurrence while successfully preserving the ovarian reserve.

The supplementary data are available with this article at https://doi.org/10.64961/kjir.2026.00017.

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