The right ovary is markedly enlarged and predominantly solid. A cystic area corresponding to a hemorrhagic corpus luteum cyst was noted. No flow was seen utilizing color Doppler flow imaging. Normal blood flow was seen in the contralateral ovary. At surgery a torsed right ovary was idenitified and removed.
Twisting or torsion of the ovary or fallopian tube (adnexal torsion) is an uncommon event. Unfortunately, it is not often considered initially when a patient presents with abdominal pain. (Diagnostic accuracies range from 18% to 64%). Adnexal torsion occurs predominantly in women of reproductive age. Pregnant women have a greater risk of torsion of the adnexa than nonpregnant women (12% - 18% of ovarian torsion occurs during pregnancy). Torsion usually occurs when a cystic mass is present within the ovary acting as focal point about which the twisting may occur. It may however also occur in a normal ovary, particularly in young girls. It is postulated that in these patients the adnexal structures are extremely mobile, allowing torsion of the mesosalpinx in response to movement or trauma. A 'hypermobile' adnexa may also be caused by a mobile hydrosalpinx, an elongated fallopian tube or previous tubal ligation, allowing torsion of the mesosalpinx. Women treated with fertility drugs who develop ovarian hyperstimulation syndrome have a greater risk of torsion with pregnancy ( 16% ) than those who do not become pregnant. The overall prevelance of torsion as the presenting sign of an adnexal mass, most commonly benign cystic teratoma is 7%.
Most authors have reported a low incidence of malignant adnexal tumors associated with adnexal torsion ( <5%). Lee and Welch reported a 15% malignancy rate of torsed adnexa (this high rate is unusual) In the study by Koonings et al over a 10 year period, no patient with a malignant neoplasm had torsion of the affected adnexa. In a study by Sommerville et al, also over a 10 year period, 11% of patients with an ovarian neoplasm had adnexal torsion. 95% of these patients with torsion had benign ovarian neoplasms, 3% had neoplasms of low malignant potential and 2% had malignant ovarian neoplasms. Among the benign ovarian neoplasms there was no single tumor type that had a predilection over others for undergoing torsion. The most common explanation for the lack of torsion in the group with malignant disease is that malignancy causes inflammation and decreased mobility of the adnexa due to adhesion formation and locally invasive tumor growth.
While twisting of the ovary or tube may each occur in isolation, torsion most often involves both structures, because the broad ligament acts as a fulcrum. Torsion of the just the fallopian tube alone is an extremely rare event. Provost and Filtenborg and Hertz have summarized the possible causative factors for isolated tubal torsion, dividing them into intrinsic factors: tortuosity, hydrosalpinx, prior tubal ligation, tubal neoplasm and extrinsic factors: ovarian masses, parovarian masses, pregnancy, extratubal adhesions, pelvic congestion or sudden body movement or trauma.
Patients presenting with adnexal torsion often have the acute onset of lower abdominal pain, often accompanied by nausea and vomiting. Half of the patients may relate a previous history of similar episodes, likely due to torsion and untorsion of the affected ovary. There is a right sided predominance of adnexal torsion, with a 3:2 ratio, possibly due to the decreased space on the left side of the lower abdomen and pelvis, occupied by the sigmoid colon.
The pathology of ovarian torsion is related to the initial circulatory stasis which is at first venous and lymphatic. The continued arterial perfusion of the ovary often leads to diffuse enlargement and edema of the ovarian parenchyma and to follicular distention due to the transudation of fluid into the cysts. Ultimately, with time, arterial thrombosis and hemorrhagic infarction of the ovary will occur. Free intraperitoneal fluid is seen in most patients and is likely a transudate from the ovarian capsule secondary to obstructed veins and lymphatic vessels.
The sonographic signs often mirror the pathologic findings described above. The "classic" sonographic appearance is that of a unilaterally enlarged ovary with multiple follicles of uniform size, approximately 8-12 mm in diameter in the cortical portion of the ovary. While this appearance of the hyperechoic central ovarian area with periperally placed follicles is often described, it was not seen in a recent study by Albayram and Hamper. They postulated that these are earlier signs of torsion and may be obscured by necrosis. If the ovarian parenchyma demonstrates either a cystic or complex mass it may be due to hemorrhage and or infarction. Most false positive diagnoses are due to hemorrhagic corpus luteum cysts or tubo-ovarian abscesses.
As one might imagine, color Doppler flow imaging is often quite useful in arriving at the correct diagnosis. Typcially no documented parenchymal perfusion will be seen in a completely torsed ovary. In one study by Willms et al in 3 out of 4 cases of ovarian torsion no flow was seen with Doppler flow imaging. All three cases required removal and could not be salvaged. The case in which flow was seen could be untwisted and salvaged at surgery. Arterial Doppler flow may be found in patients with ovarian torsion. In a study by Rosado et al, all three cases of ovarian torsion demonstrated arterial flow. They postulated two possible explanations: 1) venous thrombosis due to torsion leads to symptoms and ovarian necrosis before arterial thombosis occurs and 2) persistent adnexal arterial flow is related to the dual ovarian blood supply (one branch derived from the adnexal branch of the uterine artery and one as a branch directly from the aorta). In the study by Albayram and Hamper, they observed abnormal color Doppler flow in 14 of 15 patients (93%). The most common pattern was absence of flow in 40% of cases. The second most common abnormal flow pattern in their study was decreased venous flow with absent arterial flow in 5 patients (33%). Normal ovarian flow was seen in one patient in their series. One should be careful to not misinterpret the vessels in the pelvic side wall as representing blood flow to the mass. These vessels arise from the internal iliac artery and have high resistance waveforms without significant diastolic flow.
If either computed tomography (CT) or magnetic resonance imaging (MRI) are performed they may demonstrate a non-enhancing pelvic mass with engorged blood vessels that are straightened and drape around the ovarian lesion. There is often a small amount of ascites.
Tubal torsion may be seen sonographically as an elongated convoluted cystic mass which tapers as it nears the uterine cornua.
Clinically, a variety of gynecologic and surgical conditions may mimic adnexal torsion. These include: tubo-ovarian abscesses, endometriomas, appendicitis and ruptured ovarian cysts.
Sonographically, in addition to hemorrhagic corpus luteum cysts and tubo-ovarian abscesses, solid ovarian neoplasms and polycystic ovarian disease may also present with enlarged solid adnexal masses that at first might simulate a torsed ovary.
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