CT as triangular or bandlike soft tissue structures that show low or moderate contrast enhancement (Figs. 7 and 8). Punctate dystrophic calcifications or identification of small cysts, typically presenting inclusion cysts, or follicles at early menopause aids in the detection of the ovaries.

In MRI, postmenopausal ovaries can be visualized as oval structures most commonly of uniformly intermediate to low signal intensity on T1

and T2WI (Fig. 8) (Outwater and Mitchell 1996). They can be identified in most postmenopausal women despite their small size and nonspecific characteristics by their location in relationship to the uterus and ovarian vessels. Due to the superior soft tissue contrast, small ovarian cysts are more commonly identified in MRI than in CT in postmenopausal women (Fig. 8). As these present common findings, ovarian cysts of ≤1 cm in size are now considered as normal finding and do not require a follow-up (Levine et al. 2010). Neither diffusion restriction is found in MRI nor FDG/PET uptake in postmenopausal ovaries (Lerman et al. 2004).

Fig. 7  Postmenopausal ovaries in CT. The ovaries (arrows) appear as bandlike soft tissue structures and are located between the iliac vessels and the bowel loops. Without bowel opacification, identification of normal postmenopausal ovaries is usually not possible. Uterus (U) with a calcified fibroid of the fundus

1.4\ Pelvic Fluid

Small amounts of pelvic fluid are best identified in the cul-de-sac or with increasing volume as tiny fluid pockets outlining bowel loops ­throughout the pelvis (Welt 2016; Lee et al. 2003). Pelvic free fluid is a common finding throughout the menstrual cycle and peaks in the secretory phase (Davis and Gosink 1986). Although some fluid may be related to ovarian cyst rupture, it seems that most of the fluid is not related to cyst rupture. Pelvic free fluid is a common sequelae after pelvic

Fig.8  Normal postmenopausal ovaries in MRI and in CT in a 74-year-old female. Transaxial T2 WI (a) and corresponding CT (b) show normal small ovaries (arrowheads) that are located adjacent to the external iliac vessels and

display tiny calcifications. Small cystic structures (arrows) are seen on MRI, likely presenting inclusion cysts are a normal finding (a)

radiotherapy (Addley et al. 2010). In postmenopausal age, presence of pelvic free fluid is uncommon and further assessment is warranted. In premenopausal age, only larger amounts of pelvic fluid should alert to scrutinize the peritoneum for signs of peritoneal spread (Diop et al. 2014). Normal peritoneum does not enhance after the application of iv contrast media and shows no restricted diffusion on DWI. Diffuse enhancement, however, is not specific and is found in benign, mostly inflammatory and in malignant diseases (Diop et al. 2014).

1.5\ Ovarian Attachments

and Vascular Supply

The broad ligament is formed by two layers of peritoneum which drape over the uterus and extend laterally to the pelvic sidewalls (Foshager and Walsh 1994). Its caudal margin is defined by the cardinal ligament. The superior free margin is formed by the fallopian tube medially and the suspensory ligament of the ovary laterally. Between these peritoneal folds lies the parametrium which contains the fallopian tube, round ligament, ovarian ligament, uterine and ovarian blood vessels, nerves, lymphatics, mesonephric remnants, and the parts of the ureter (Foshager and Walsh 1994).

Each ovary is suspended in the peritoneal cavity by three supporting structures: the mesovarium which anchors the ovary to the posterior aspect of the broad ligament; the ovarian ligament which attaches the ovary to the uterine cornu; and the suspensory ligament or infundibulopelvic which anchors the ovary to the pelvic sidewall (Clement 2002).

The ovarian ligament and the suspensory ligament are not tight supporting structures but more comparable to a mesentery (Saksouk and Johnson 2004). The ovarian blood vessels and lymphatics course within the peritoneal folds of the mesovarium and enter and exit the ovary through the ovarian hilum. Anastomosing branches of the ovarian and uterine vessels in close relationship with lymphatics are located within the mesovarium (Clement 2002).

The suspensory ligament of the ovary is located at the superior lateral aspect of the broad

ligament (Clement 2002). It extends from the ovary anterolaterally over the external and common iliac vessels and blends with connective tissue over the psoas muscle (Foshager and Walsh 1994). Ovarian blood vessels and lymphatics traverse the suspensory ligament to reach the ovarian hilum along the mesovarium.

The ovarian ligament is a rounded fibromuscular band extending from the ovary to the uterine cornu (Clement 2002). Its position varies with that of the ovary. It is located immediately posterior and inferior to the fallopian tube and round ligament (Foshager and Walsh 1994). The ovarian branches of the uterine artery pass through the ovarian ligament and anastomose with branches of ovarian artery in the mesovarium.

The ovarian artery originates from the lumbar aorta near the renal hilum. It is accompanied along its retroperitoneal course by the ovarian vein and the ureter on the anterior surface of the psoas muscle. It then crosses the ureter and common iliac vessels near the pelvic brim to enter the suspensory ligament of the ovary. The ovarian artery courses inferiorly and medially between the two layers of the broad ligament near the mesovarian border (Saksouk and Johnson 2004). It forms multiple branches that enter the ovarian hilum via the mesovarium. It has a tortuous course that is most evident near the ovary.

The ovarian vein is typically single, but may also be multiple and accompanies the ovarian artery. The venous drainage is into the left renal vein, and into the inferior vena cava on the right side. At the pelvic level, they can be identified at the medial aspect of the external iliac vessels. The ovarian lymphatics ascend with the ovarian vessels along the psoas muscle and drain almost exclusively into the para-aortal lymph nodes at the level of the lower pole of the kidneys. In some patients, accessory channels pass the broad ligament and drain into the internal and common iliac and interaortic lymph nodes, or course along the round ligament to the external iliac and inguinal lymph nodes (Clement 2002). In the fallopian tube, additional lymphatic channels to presacral nodes, and occasionally from the ampulla, to gluteal nodes may exist (Clement 2002).