especially­ to better determine the exact site of origin of the ectopic pregnancy (Filhastre et al. 2005).

3\ Nongynecological Causes

of Pelvic Pain

3.1\ Pelvic Congestion Syndrome

Pelvic congestion syndrome or pelvic venous incompetence (PVI) is a common cause of chronic non-cyclical pelvic pain that affects most often multiparous women of reproductive age. The symptoms of chronic dull pelvic pain, pressure, and heaviness have been attributed to dilated, tortuous, and congested veins that are produced by retrograde flow through incompetent valves in ovarian veins, although the causal relationship between PVI and chronic pelvic pain is not established (Champaneria et al. 2016). Patients with pelvic congestion syndrome may also suffer from dyspareunia (71%), dysmenorrhea (66%), and postcoital ache (65%) (Kuligowska et al. 2005). The prevalence of pelvic congestion syndrome is closely related to the frequency of ovarian varices, which occur in 10% of the general population of women. Within this group of patients, up to 60% may develop pelvic congestion syndrome (Lopez 2015). The pathogenesis of pelvic congestion syndrome is most likely multifactorial and influenced by hormonal effects, multiparity, and previous surgery. Pelvic congestion syndrome may also result from obstructing anatomic anomalies such as a retro-aortic left renal vein or right common iliac vein compression (Kuligowska et al. 2005). It may be associated with asymptomatic hematuria in the nutcracker phenomenon, which is caused by left ovarian vein congestion secondary to compression of the left renal vein by the superior mesenteric artery (Umeoka et al. 2004). Dilated veins include veins in the broad ligaments, ovarian plexus, and pelvic sidewalls. Varices within the para-vaginal plexus, vulva, or the lower extremities may

also be found (Umeoka et al. 2004). Polycystic changes in ovaries are associated in approximately 40% of cases (Park et al. 2004).

3.1.1\ Imaging Findings

The typical imaging findings are dilated and tortuous vascular structures engorging the uterus and ovaries, which may extend to the pelvic sidewalls or communicate with paravaginal veins. Ultrasound and MR imaging are noninvasive methods used to diagnose pelvic varices. The diagnosis of pelvic varicosities may also be made on CT by the demonstration of at least four ipsilateral dilated para-uterine veins of varying caliber, with a width of at least one vein larger than 4 mm or a diameter of the ovarian vein of more than 8 mm (Fig. 14) (Rozenblit et al. 2001). On T1-weighted MR images, pelvic varices display low signal intensity because of flow-void artifacts. On T2WI, the signal intensity depends on the velocity of blood flow. Contrast-enhanced magnetic resonance venogram (MRV) displays enhancing veins with maximal opacification in a venous phase. On gradient echo MR images, the varices typically display high signal intensity. MRV has been shown to have high sensitivity for pelvic venous congestion when using phlebography as a reference standard (Asciutto et al. 2008).

3.1.2\ Differential Diagnosis

Incompetent and dilated ovarian veins are frequently seen on CT in asymptomatic parous women (Fig. 15) (Rozenblit et al. 2001). Congenital or acquired vascular malformations of the uterus or parametria present also as vascular lesions. Contrast-enhanced CT or MRI may aid in the differentiation by the early enhancement of arteriovenous malformations in contrast to a more delayed enhancement in varicosities (Gulati et al. 2000). Adnexal masses with torsion or rare uterine tumors, especially choriocarcinomas, may also be surrounded by thick, tortuous, well-enhanced vessels. The clinical background and imaging findings of an adnexal or uterine mass aid in the differential diagnosis.

Fig. 14  Pelvic congestion syndrome. Transaxial CT at the level of the cervix uteri (a) and coronal scans in the pelvis and retroperitoneum (b, c). Multiple dilated tortuous pelvic vascular structures are demonstrated within the parametria and pelvic sidewalls (a). The coronal images

demonstrate engulfment of the uterus (U) by these vascular structures (b, c). Dilatation of both ovarian veins (arrows), which display a diameter of more than 8 mm, is shown in (c). U uterine corpus, C cervix