What is the diagnosis for a patient with a likely right ovarian corpus luteum, small pelvic fluid, an unremarkable partially visualized appendix, and mildly prominent mesenteric nodes?

From the Guidelines

The patient's findings are most consistent with a normal corpus luteum and physiologic pelvic fluid, and thus, no immediate intervention is required, but a follow-up ultrasound is recommended for further evaluation, as suggested by the O-RADS guidelines 1. The presence of a likely right ovarian corpus luteum, as indicated in the final results, is a normal finding, especially in pre-menopausal women, and aligns with the O-RADS classification of a normal ovary, which includes a corpus luteum less than 3 cm 1. The small fluid in the pelvis, described as possibly physiologic, is also a common finding and does not immediately suggest a pathological condition. According to the O-RADS guidelines, simple cysts less than 3 cm are considered almost certainly benign, and larger simple cysts up to 5 cm may also be benign but warrant follow-up, especially in post-menopausal women 1. Given the information provided:

• The appendix appears unremarkable, which is reassuring and suggests no acute appendicitis.
• The mildly prominent mesenteric nodes are considered possibly reactive, which is a common response to minor infections or inflammation and not typically indicative of a serious condition. Key points to consider from the O-RADS guidelines include:
• The use of a color score (CS) in risk stratification, particularly for lesions in the higher-risk categories.
• The classification of lesions into risk categories (O-RADS 0-5) to guide management, with O-RADS 2 being almost certainly benign and O-RADS 3 indicating a low risk of malignancy.
• The recommendation for follow-up or specialist referral based on the size and characteristics of the ovarian lesions, as well as the patient's menopausal status. In this case, a follow-up ultrasound, as recommended, would be the most appropriate next step to further evaluate the pelvic fluid and confirm the benign nature of the findings, aligning with the principles outlined in the O-RADS guidelines for managing adnexal lesions 1.

From the Research

Ultrasound Findings

• The ultrasound findings indicate a likely right ovarian corpus luteum, which is a normal post-ovulatory structure seen in the ovaries through the second half of the menstrual cycle and the first trimester of pregnancy 2.
• The presence of a small fluid in the pelvis is possibly physiologic, but further evaluation with ultrasound can be performed to confirm this finding.
• The partially visualized appendix appears unremarkable, which suggests that there is no significant abnormality in the appendix.

Differential Diagnosis

• The ultrasound findings of a corpus luteum cyst can be mimicked by other conditions such as endometrioma, ectopic pregnancy, tuboovarian abscess, red degeneration of a fibroid, and ovarian neoplasia 2.
• The presence of a hemorrhagic ovarian cyst can be diagnosed with high confidence if specific sonographic features such as fibrin strands and a retracting clot are present 3.

Management

• The American College of Obstetricians and Gynecologists (ACOG) recommends that simple cysts found on ultrasound may be safely followed without intervention, even in postmenopausal women 4.
• For patients with ovarian cysts, ovarian cancer screening and follow-up include a CA-125 blood test and transvaginal ultrasonography (TVU) at baseline, an annual TVU for three additional years, and annual CA-125 tests for five years beyond baseline 4.

Imaging Modalities

• Ultrasound is the ideal non-invasive first-line technique for diagnosing acute gynaecologic disorders, but multidetector computed tomography (CT) and magnetic resonance imaging (MRI) can also be used for further characterization of gynaecologic abnormalities 5.
• MRI is superior to CT for further characterization of gynaecologic abnormalities due to its excellent soft-tissue contrast, intrinsic multiplanar capabilities, and lack of ionizing radiation 5.