On US, the demonstration of an unilaterally enlarged ovary is the most common finding in case of AT [1, 11, 14] (Fig. 24.2). Oltmann et al. [15] has reported that, in a pediatric population older than 1 year, the presence of a pelvic mass larger than 5 cm diameter has the highest diagnostic sensitivity for the diagnosis of ovarian torsion. Servaes et al. have reported the interest of a volume ratio: the size of the twisted ovary was compared with that of the contralateral ovary; the median ratio between the twisted side and the normal side was 12. The median volume ratio was significantly greater (>20) when an adnexal mass was present [1]. The torsed adnexa determines the visualization (in up to 70% of cases) of a complex adnexal or abdomino-pelvic mass, that can predominantly be cystic, solid/echogenic or both [11, 16].

In addition to the ovarian enlargement, a peripheral displacement of the follicles secondary to stromal edema and venous congestion can be visualized in up to 70% of patients with AT [3, 17].

A “whirlpool” sign or the “nipple” sign has been reported in case of AT; it appears as a pseudo-mass of concentric stripes with a beaked center. This can also be visualized as an ellipsoid or tubular mass with internal heterogeneous echoes, depending on the plane of scanning. This sign corresponds to the torsion of the vascular pedicle, tubal structures and supporting ligaments. In a study by Lee et al., a twisted vascular pedicle was detected in 88% of cases of AT. When present, this finding is pathognomonic of AT [18].

Another potentially helpful sonographic sign is the medialization of the adnexal structures with sometimes a complete controlateral position of the twisted ovarian. As torsion occurs, the twisting of the adnexal structures adjacent to the broad ligament creates a centrifugal force that attracts the adnexal structures closer to the uterus [19].

The rates of the various US findings such as adnexal enlargement, adnexal edema, or ovarian or paraovarian cysts are reported similar between the pre- and the post-menarchal girls [13].

Ipsilateral deviation of the uterus (IDU) was found to be frequent in AT. This results from the displacement of the abnormal adnexa toward the midline with the broad ligament acting as a fulcrum pulling the uterus towards the affected side. The contralateral fallopian tube is straightened as well [20]. This sign is insufficient by itself. In the absence of supporting clinical and imaging findings of torsion, the identification of IDU in the routine clinical setting of an adnexal mass is not a strong predictor of AT.

Thickened or enlarged fallopian tube: fallopian tube torsion associated with a hydrosalpinx has been reported in approximately 9% of AT. Additional findings such as a thickened, echogenic fallopian wall and the presence of internal tubal debris or hemorrhage may render difficult the differentiaton between a fallopian tube torsion and hydro/pyosalpinx in relation with pelvic inflammatory disease. The clinical context and the search of a pelvis surgical history are essential for the differentiation.

In addition, free pelvic fluid in the cul-de-sac has been detected with US in up to 87% of cases of ovarian torsion [11, 16].

The classic color Doppler sonographic sequence in adnexal torsion is first, the absence of venous flow followed by the absence of arterial flow. Noteworthy, the ovaries have a dual supply from both ovarian and uterine arteries, which can result in detection of arterial flow even when the ovary is found to be partially necrotic at surgery. Some authors have reported arterial or venous blood flow abnormalities in two-thirds of patients [4] while others report much higher rates [5, 21]. Conversely, in another study, 60% of patients with AT had normal color Doppler flow findings [11, 22]. Absence of Doppler flow does not occur in every case of AT and may occur only as a late finding [23]. So, the sensitivity of absent arterial flow can be as low as 40% [17]. However, some authors insist on a high negative predictive value [24].

Therefore, neither the presence nor the absence of Doppler flow can be used to definitively confirm or exclude torsion; still the degree of vascularization and the presence of flow might be useful for predicting the viability of the ovary following detorsion. Fleischer et al. [25] have reported that the presence of central venous flow in a twisted ovary was associated with increased likelihood of ovarian viability post detorsion.

Noteworthy, in post-pubertal girls, hemorrhagic cysts can have a similar appearance to twisted ovaries [26]. Both entities may have a complex US appearance and a reduced or absent arterial flow. Large hemorrhagic cysts may be responsible of a mass effect on the adjacent ovarian tissue and on the blood flow.

If a AT on tumor is diagnosed by US, detorsion must be made in emergency by laparascopy after dosage of tumoral markers. MR imaging will be performed after surgery, to fully assess the mass.

In an acute clinical setting, after confirmatory US, no complementary examination should delay exploring laparoscopy.

When the diagnosis of AT is unclear, as in case of subacute or intermittent ovarian torsion, MR imaging can be useful to further delineate the anatomy, particularly in a preoperative setting. MR imaging can also characterize an underlying mass.

MR imaging protocol includes T2-Weighted sequences, T1-weighted fat-suppressed sequences to detect hemorrhage and fat in germinal masses, as well as T1-Weighted fat-suppressed post-contrast sequences. The latter are aimed to detect compromized vascular supply, which would suggest infarction or necrosis (Fig. 24.3).

As with US, an enlarged ovary is the most common finding on MR imaging [14]. It is more specific when it is associated with an edematous central stromal area and peripherally displaced follicles. This finding is best seen on T2-weighted sequences, appearing as a central hypersignal.

Performing CT is not recommended in the evaluation of suspected ovarian torsion in children, mainly because of ionizing radiation hazards and poor cost-efficiency when compared to US. It could be performed when the clinical presentation is unclear. Whenever performed, only a venous acquisition after contrast injection should be obtained. Noteworthy, a CT is useful as it can identify other causes of the acute pelvic symptoms such as appendicitis or urolithiasis, both may clinically mimic AT.

A further contribution of CT is its ability to demonstrate calcifications within germinal tumors.

CT and MR imaging were also found to be useful in delineating the twisted vascular pedicle, similarly to the sonographic whirpool sign (Fig. 24.2). The twisted lombo-ovarian pedicle can itself be visualized as inflamed and thickened.

A decreased or absent enhancement of the ovarian parenchyma after contrast injection confirms ovarian necrosis.

Further CT and MR imaging features include ascites, fallopian tube thickening, displacement of the uterus towards the twisted ovary, and change in position of the involved adnexa toward either the midline (medialization) or the contralateral side of the pelvis.

Finally, hemorrhagic infarct will appear as a T1 hypersignal and lack of enhancement.

Rarely, torsion can be limited to the Fallopian tube itself, leaving the ovary undamaged. The etiologies of fallopian tube torsion includes both intrinsic fallopian tube abnormalities and extrinsic causes like pelvic post-surgical or infectious adhesions, para-adnexal—para-tubal or para-ovarian—cysts, the latter are the most common cause for fallopian tube torsion in the pediatric population [27–29].

The clinical picture is the same as for a complete AT but it may be more subtle. Imaging may show tubal changes, such as dilated thick-walled tube or a pseudomass between the uterus and the ovary, whereas the ovary appears normal (Fig. 24.4). Tubal dilatation can be global or segmental with an appearance of a cyst. The visibility of plicae tubariae is useful and confirms the diagnosis of tubal dilatation. A paratubal or paraovarian mass is often associated as reported in the literature [30, 31]. The whirpool sign is difficult to detect.

MRI may be useful to establish the diagnosis. It is more specific when it is associated with hemorrhagic content in the fallopian tube, the whirlpool sign, lack of enhancement after contrast injection of the tube. MRI can also visualize an underlying mass like para tubal cyst [30, 31].

Asynchronous bilateral torsion is defined as torsion of both ovaries but at different periods; asynchronous torsion is rare, but can be devastating in terms of fertility especially if repeated oophorectomy has to be performed. The risk of recurrent ipsilateral or asynchronous contralateral AT is unknown, though estimated figures range from 2% to 5% [32] to as high as 10% in the absence of apparent ovarian disease [5]. It is likely that these patients have underlying anatomic variations that render them at increased risk of AT.

Though paratubal and paraovarian cysts are rare in adolescent females, the influence of post-menarchal hormonal stimulation on these tubal derivates could favor asynchronous AT [33].

The inclusion of an ovary in an inguinal hernia is “classic” and the diagnosis can be confirmed easily by US [34]. It is usually not painful; when uncomplicated, the treatment should not an emergent but a programmed surgery.

AT may occur within an indirect inguinal hernia that will become incarcerated. It occurs more often in pre-menarchal girls [13]. Merriman reviewed 71 cases of irreducible hernias in girls and report that 82% the hernias contained an ovary; 11 ovaries had twisted [35]. Very rarely the hernia may contain the fallopian tube and the uterus (Fig. 24.5). All these conditions require emergency treatment, usually surgery.

Precocious puberty, large bilateral polycystic ovaries and premature menarche can develop in a context of severe hypothyroidism, facilitating a twist of the adnexa [36].

Uterine torsion is considered exceedingly rare in children and very rare reports have been published. The diagnosis is rarely made preoperatively and necrosis of the uterus is a dramatic complication [37].