An adnexal mass is a common finding during a pelvic examination or ultrasound. This term describes a growth or lump that develops in the tissues adjacent to the uterus. Understanding how ultrasound evaluates these masses is the first step in clarifying the diagnosis and subsequent management plan. This article will explain what an adnexal mass is, detail the specific features examined during an ultrasound, and outline the various causes and next steps in care.
What is an Adnexal Mass?
The term “adnexa” refers to the structures located near the uterus, which primarily include the ovaries, the fallopian tubes, and the surrounding ligaments and connective tissue. An adnexal mass is any growth found in this specific anatomical region. The mass can be fluid-filled, solid, or a mixture of both components, and its size can vary significantly.
Most adnexal masses are benign, particularly in women of reproductive age, but they require careful evaluation to exclude malignancy. Because the adnexa are located deep within the pelvis, transvaginal ultrasound is the most effective initial tool for visualization and characterization.
Interpreting Ultrasound Features
Transvaginal ultrasonography is the preferred method for evaluating an adnexal mass because it provides high-resolution images of the pelvic organs. The sonographer and radiologist systematically analyze several features of the mass to help determine its likely cause and potential risk.
The composition of the mass is a primary characteristic, categorized as simple or complex. A simple mass is typically a unilocular cyst, a single, smooth, thin-walled sac filled with clear fluid, which appears anechoic, or black, on the ultrasound screen. Conversely, a complex mass contains internal structures like solid components, thick internal walls called septations, or small projections extending from the wall, which are concerning features.
The size and shape of the mass also influence the assessment and subsequent management decisions. Masses larger than 10 centimeters are less likely to resolve spontaneously and have an increased risk of complications, such as ovarian torsion. Irregular or lobulated borders are another feature that may raise suspicion compared to a mass with a smooth, well-defined contour.
Color Doppler ultrasound is utilized to assess the blood supply within the mass or its septations. Increased blood flow within the solid components, particularly if the vessels show high flow velocity, can be an indicator of potential malignancy. The presence of flow in septa greater than 2 to 3 millimeters thick may suggest a need for further investigation.
Common Causes of Adnexal Masses
The ultrasound characteristics help narrow down the differential diagnosis. The most frequent causes are benign ovarian cysts, which are often related to the menstrual cycle. Functional cysts, such as follicular cysts and corpus luteum cysts, form during ovulation and usually resolve on their own within a few weeks or months.
Other benign ovarian causes include non-functional cysts like endometriomas, which contain old blood from endometriosis. Mature cystic teratomas, also known as dermoid cysts, are also common and may contain various tissues like hair, fat, or teeth, often appearing with distinct echogenic features and acoustic shadowing on ultrasound.
Causes that originate outside the ovary must also be considered, especially when an ovary is seen separate from the mass. A hydrosalpinx is a benign condition where a fallopian tube becomes blocked and filled with clear fluid, creating a sausage-shaped cystic mass. Uterine fibroids may sometimes grow on a stalk and present as an adnexal mass. An ectopic pregnancy, where a fertilized egg implants outside the uterus, is a serious, urgent cause that must be ruled out in reproductive-age women.
Masses that display highly complex features, such as multiple thick septations, large solid components, or papillary projections, raise the concern for a malignant tumor, which may originate in the ovary or fallopian tube. The risk of malignancy increases in postmenopausal women and in those with specific symptoms like abdominal bloating or difficulty eating. These concerning features prompt immediate referral to a specialist for advanced evaluation.
Management and Follow-Up
Once an adnexal mass is identified and characterized by ultrasound, the next step involves determining the appropriate management strategy. For small, simple, asymptomatic cysts found in premenopausal women, the standard approach is often watchful waiting. This involves a repeat ultrasound, typically in six to twelve weeks, to confirm if the mass has resolved or remained stable.
If the mass is large, symptomatic, or has concerning features, further testing may be necessary. Blood tests like the Cancer Antigen 125 (CA-125) are sometimes used to assess risk, particularly in postmenopausal patients. CA-125 levels can be elevated by various benign conditions, including endometriosis and fibroids, and are not always elevated in early-stage cancers. Advanced imaging, such as Magnetic Resonance Imaging (MRI), may be ordered to better characterize indeterminate solid components seen on the initial ultrasound.
Intervention is generally reserved for masses that are highly suspicious for malignancy, are causing severe symptoms, or have a significant size. Surgical options range from minimally invasive laparoscopy to open surgery, depending on the size and complexity of the mass. The goal of surgery is to remove the mass for definitive diagnosis while preserving the ovary if possible, especially in younger patients.