Adnexal cysts or pseudocysts are a common finding on transvaginal ultrasound, especially in premenopausal women. Due to the size of some cysts, they may cause discomfort. Moreover, a genuine risk of ovarian torsion presents when these lesions grow.

During the last decades, great advancements have been made in the correct differentiation of benign from malignant lesions. However, there still is controversy concerning the optimal treatment approach of symptomatic adnexal cysts with a low risk of malignancy, consisting of both surgery or ultrasound-guided transvaginal aspiration. Factors such as comorbidities and lesion characteristics need to be considered when counselling patients, as well as the possibility of short term recurrence.

Surgically removing them may result in longer hospital stays and recovery, with higher costs, while transvaginal needle aspiration techniques can be performed during a consultation. Additional benefits in avoiding surgery, particularly in women of reproductive age, are fertility preservation and less pelvic adhesions.

On the other hand, the main arguments against cyst aspiration are the relatively high recurrence rate of cysts, the minimal risk of malignant cell dissemination (In case of a false negative diagnosis) and the cytological instead of a histopathological examination.

With this in mind, it is important to base management decisions on the sonographic features of the lesions.

In addition, cyst aspiration can also be considered in large symptomatic cysts with a high risk of malignancy, but where curative treatment with surgical or chemotherapeutical intervention cannot be considered due to poor general condition of the patient. Especially in the absence of large volume ascites or peritoneal carcinomatosis, but with significant symptoms due to lesion size, cyst aspiration may give short term symptom alleviation. Given the risk of cancer cell dissemination, this intervention is always discussed in a multidisciplinary team discussion, to balance risk and benefits for patients with no other treatment options, Transvaginal needle aspiration is also being used in pelvic abscesses. The study of K. Gjelland et al. found that transvaginal aspiration combined with antibiotic treatment of pelvic abscesses is equally effective as surgically removing them. They state that this should be first-line treatment for abscesses, as it is minimally invasive, leading to better patient tolerance and avoiding the risks associated with anesthesia and surgery.

Saline irrigation of the abscess cavity can be performed, making the process of pus aspiration easier when the consistency is too viscous.

The literature still lacks studies about the symptom relief in patients receiving treatment for pelvic cystic lesions. Given that this is an important outcome parameter in determining the feasibility of performing procedures, more research in this area is needed.

The main aim of this prospective study is to evaluate the patient's symptom relief and cyst recurrence rate after ultrasound-guided transvaginal aspiration of pelvic cystic lesions or abscess drainage. Secondly, the safety and the patient's overall experience during as well as immediately after the procedure will be assessed.

Participants eligible for inclusion in this study must meet all of the following criteria:

1. Lesion criteria applicable for therapeutic intervention

   1. Safe accessibility of the lesion (within reach of aspiration needle; visible on ultrasound; transvaginal access; no interposition of bowel or blood vessels)
   2. Lesion types included: cystic lesions (adnexal cysts), pelvic inclusion cysts (pseudocysts), pelvic abscesses

2. Indications

   1. Pain relief in symptomatic cystic lesions with benign appearance.
   2. Symptomatic treatment in probably malignant lesions (only in non-curative setting).

Exclusion Criteria:

1. Patients <18 years
2. Poor performance status contra-indicating the procedure
3. Vaginal stenosis (severe atrophy - virgo - vaginismus)
4. Purely solid lesions
5. Cystic lesions with a presumed malignant diagnosis and a risk of tumor dissemination in a curative setting
6. Physiological cysts in asymptomatic patients (in case of doubt the patient is reassessed after 3-6 months)

All patients elligible based on the above mentioned criteria in University Hospitals Leuven.

All IPD that underlie results in a publication will be added in the journal submission, and will be made available to other investigators on reasonable request.