Ovarian Masses and O-RADS

A Systematic Approach to Evaluating and Characterizing Adnexal Masses With Ultrasound

Ana Mitchell, MD; Austin Kwong, MD; Simran Sekhon, MD; John P McGahan, MD, FACR

Appl Radiol. 2021;50(3):24-31.

Abstract and Introduction

Introduction

Clinical presentation and pertinent laboratory analysis often determine the appropriate imaging differential diagnostic considerations in evaluating anyone with ovaries presenting with pelvic symptoms. In patients with a positive pregnancy test, sonography is the modality of choice to evaluate the pregnancy and any complications. Sonography is also the modality of choice for evaluating patients who present with pelvic pain or a mass but are not pregnant. Pelvic sonography is the preferred imaging modality when an obstetrical or gynecologic etiology is suspected under American College of Radiology (ACR) Appropriateness Criteria.^[1]

Sonography is useful in evaluating for the presence of an adnexal mass as well as for mass characterization.^[2] For example, the sonographic appearance of a retracting clot and/or a reticular pattern without Doppler flow/vascularity is diagnostic of a hemorrhagic cyst (Figure 1).^[3] Most adnexal cysts are benign and are easily characterized by ultrasound. However, evaluation of indeterminate adnexal masses by an ultrasound expert is highly valuable.^[3] Published data supports the use of pattern recognition by an experienced ultrasound examiner as a highly accurate method of discriminating between benign and malignant adnexal masses without the need for MRI.^[3] In particularly challenging cases, contrast-enhanced MRI may be helpful in differentiating between benign and malignant ovarian masses.

(Enlarge Image)

Figure 1.

Hemorrhagic ovarian cyst. Typical reticular pattern of fine, thin intersecting lines representing fibrin strands with no central flow is one pattern of a hemorrhagic cyst (O-RADS 2).

This two-part review describes a stepwise approach to evaluating and characterizing adnexal masses in non-pregnant patients. Here in part 1, we will review the utilization of ultrasound in this endeavor. In part 2, we will review the use of MRI.

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Next Section

Table 1. Common Differential Diagnoses for Adnexal Masses in Non-pregnant Patients
• Physiologic ovarian cyst/follicle • Other ovarian cysts • Hemorrhagic cyst • Endometrioma • Tubo-ovarian abscess • Pyo/hydrosalpinx • Abdominal abscess • Paraovarian cyst • Dermoid cyst/Teratoma • Serous/mucinous cystadenoma or CA and other epithelial neoplasms • Fibromas/Thecomas • Ovarian metastases • Ovarian torsion • Pedunculated fibroid • Peritoneal inclusion cysts

Table 2. O-RADS Ultrasound Risk Stratification and Management System
O-RADS Score	Risk Category [IOTA Model]	Lexicon Descriptors		Management
O-RADS Score	Risk Category [IOTA Model]	Lexicon Descriptors		Pre-menopausal	Post-menopausal
0	Incomplete Evaluation [N/A]	N/A		Repeat study or alternate study
1	Normal Ovary [N/A]	Follicle defined as a simple cyst ≤ 3 cm		None	N/A
1	Normal Ovary [N/A]	Corpus luteum ≤ 3cm		None	N/A
2	Almost Certainly Benign [< 1%]	Simple cyst	≤ 3 cm	N/A	None
			> 3 cm to 5 cm	None	Follow up in 1 year. *
			> 5 cm but < 10 cm	Follow up in 8 - 12 weeks	Follow up in 1 year. *
		Classic benign lesions	See Table 3 for descriptors and management strategies
		Non-simple unilocular cyst, smooth inner margin	≤ 3 cm	None	Follow up in 1 year * If concerning, US specialist or MRI
		Non-simple unilocular cyst, smooth inner margin	> 3 cm but < 10 cm	Follow-up in 8 - 12 weeks If concerning, US specialist	US specialist or MRI
3	Low Risk Malignancy [1-<9%]	Unilocular cyst (simple or non-simple) ≥ 10 cm		US specialist or MRI management by gynecologist
		Typical dermoid cysts, endometriomas, hemorrhagic cysts ≥ 10 cm
		Unilocular cyst, with irregular inner wall (<3 mm height), any size
		Multilocular cyst with smooth inner walls/septations, < 10 cm, CS = 1–3
		Solid lesion with smooth outer contour, any size, CS = 1
4	Intermediate Risk [10-< 50%]	Multilocular cyst, no solid component	Smooth inner wall, ≥ 10 cm, CS = 1–3	US specialist or MRI Management by gynecologist with gyno-oncologist consultation or solely by gyno-oncologist
			Smooth inner wall, any size, CS = 4
			Irregular inner wall ± irregular septation, any size, CS = any
		Unilocular cyst with solid component	1–3 papillary projections (pp), or solid component that is not a pp, any size, CS= any
		Multilocular cyst with solid component	Any size, CS = 1–2
		Solid lesion	Smooth outer contour, any size, CS = 2–3
5	High Risk [≥ 50%]	Unilocular cyst, ≥ 4 papillary projections, any size, CS = any		Gyno-oncologist
		Multilocular cyst with solid component, any size, CS = 3–4
		Solid lesion with smooth outer contour, any size, CS = 4
		Solid lesion with irregular outer contour, any size, CS = any
		Ascites and/or peritoneal nodules**

Table shows ovarian-adnexal reporting and O-RADS risk stratification and management system adapted from American College of Radiology O-RADS for Ultrasound.
CS=color score; GYN = gynecologic; N/A = not applicable
*At least one-year follow-up showing stability or decrease in size is recommended with consideration of annual follow-up of up to 5 years, if stable. However, there is currently a paucity of evidence for defining the optimal duration or interval of timing of surveillance.
**Presence of ascites with category 1–2 lesion, must consider other malignant or nonmalignant etiologies of ascites.

Table 3. Classic Benign Lesions (O-RADS 2)
Lexicon Descriptor	Definition	Management
Lexicon Descriptor	Definition	Premenopausal	Postmenopausal
Typical hemorrhagic cyst	Reticular pattern: Fine thin intersecting lines representing fibrin strands Retracting clot: An avascular echogenic component with angular, straight, or concave margins	≤ 5 cm None	US specialist, gynecologist, or MRI
Typical hemorrhagic cyst		>5 cm but < 10 cm Follow-up in 8–12 weeks If it persists or enlarges, referral to US specialist, gynecologist, or MRI	US specialist, gynecologist, or MRI
Typical dermoid cyst < 10 cm	▪ Hyperechoic component with acoustic shadowing ▪ Hyperechoic lines and dots ▪ Floating echogenic spherical structures	Optional initial follow-up in 8–12 weeks based upon confidence in diagnosis If not removed surgically, annual US follow-up should be considered * US specialist or MRI if there is enlargement, changing morphology, or a developing vascular component	US specialist, gynecologist, or MRI With confident diagnosis, if not removed surgically, annual US follow-up should be considered * MRI if there is enlargement, changing morphology, or a developing vascular component
Typical endometriomas < 10 cm	Ground-glass/homogeneous low-level echoes
Simple paraovarian cyst/any size	Simple cyst separate from the ovary that typically moves independent of the ovary when pressure is applied by the transducer	None If not simple, manage per ovarian criteria	Optional single follow-up study in 1 year
Typical peritoneal inclusion cyst/any size	Follows the contour of the adjacent pelvic organs or peritoneum, does not exert mass effect, and typically contains septations. The ovary is either at the margin or suspended within the lesion.	Gynecologist	Gynecologist
Typical hydrosalpinx/any size	▪ Incomplete septation ▪ Tubular ▪ Endosalpingeal folds: Short round projections around the inner wall of a fluid distended tubular structure	Gynecologist	Gynecologist

Table shows O-RADS US risk stratification and management system for classic benign lesions and associated descriptors (O-RADS 2), adapted from source reference No.3 with permission of the American College of Radiology. *There is currently a paucity of evidence for defining the optimal duration or interval of timing for surveillance. Evidence does support an increasing risk of malignancy in endometriomas following menopause

Table 4. Ovarian Neoplasms
Origin	Surface epithelium	Germ cells	Parenchyma (sex cord-stroma)	Metastases
Frequency	65 – 70%	15 – 20%	5 – 10%	5%
% of malignant	90%	3 – 5 %	2 – 3%	5%
Age	20+	0 – 25+	All	Variable
Types	Serous	Teratoma	Fibroma
	Mucinous	Dysgerminoma	Granulosa-theca cell tumor
	Endometrioid	Endodermal sinus	Sertoli-Leydig cell tumor
	Clear Cell	Choriocarcinoma	Cystadenofibroma
	Brenner