The ‘whirlpool sign’ is recognized in the literature as a pathognomonic sonographic sign of small-intestinal volvulus (secondary to malrotation of the midgut) and is used in the pre- and postnatal diagnosis of this pathology1, 2. The term denotes the widened intestinal loops spiraling around a central axis composed of the mesentery and superior mesenteric arteries, with the superior mesenteric vein twisted around them. This pathology is characterized by mechanical bowel obstruction with secondary venous engorgement of the intestinal wall.
The sonographic appearance of a tissue mass twisted around a central axis has also been described in cases of acute scrotum with twisted testicle3 and was once mentioned in the literature as a useful sign for diagnosis of ovarian torsion4. In that report4 the sonographic whirlpool sign was visualized in all of the 21 symptomatic patients with suspected ovarian torsion presenting with intermittent pain and a sonographically defined ovarian mass. Torsion was confirmed in all patients, with a strong correlation between the absence of color Doppler flow in the twisted pedicle and viability of the ovary.
The whirlpool sign is visualized by moving the ultrasound probe back and forth along the axis of suspected torsion (either along the ovarian ligament, when torsion of all the adnexa is suspected, or along the pedicles of paraovarian masses, such as paraovarian cyst or sactosalpinx, when torsion involves only some adnexal structures, such as the Fallopian tube) (Figure 1a and b and Videoclip S1 online). Characteristic gray-scale features of the twisted pedicle are evaluated together with color Doppler assessment (Figure 1c and Videoclip S2). Three-dimensional (3D) power Doppler may also be useful as an adjunct tool to improve visualization of the pathology in cases in which normal flow is maintained (Figure 2).
In cases in which the management of suspected ovarian torsion is complicated, for example in pregnant patients, symptomatic patients with normal ovary on ultrasound, asymptomatic patients with ovarian mass with suspected torsion or patients with high operative risk, confirmation or exclusion of torsion is especially important. We present the application of the whirlpool sign and describe its utility in three cases of suspected torsion with atypical presentation managed in our center. The women, who presented with symptoms suggestive of ovarian torsion, were evaluated using two-dimensional (2D) and 3D ultrasound techniques for assessment of common sonographic signs such as abnormal ovarian position, edema, ovarian or adnexal masses, fluid in the pouch of Douglas, decreased blood flow in the ovaries and presence of the whirlpool sign.
Case 1: torsion of the Fallopian tube in a mildly symptomatic woman with apparently normal ovary on ultrasound
A 46-year-old woman, gravida 4 para 4, presented to the emergency room with lower left abdominal pain that had begun the day before admission, without other gastrointestinal or genitourinary symptoms. She had undergone laparoscopy 8 years previously for a pelvic cystic mass and suspected left adnexal torsion, which revealed left sactosalpinx without torsion.
On clinical examination the abdomen was soft with slight lower left abdominal tenderness and a palpable left adnexal mass. Blood tests were normal. Transvaginal ultrasound examination showed normal ovaries, normal Doppler flow in the left ovarian ligament (Figure 3a) and the known sactosalpinx on the left side (Figure 3b). The only new abnormal finding was the presence of the whirlpool sign in the left proximal part of the Fallopian tube (Figure 1b). Flow was not detected in the pedicle. Laparoscopy revealed torsion of the left Fallopian tube and sactosalpinx with necrotic areas, which was removed after detorsion (Videoclip S3). The uterus and ovaries were normal.
Case 2: torsion in pregnancy
A 16-year-old primigravida with unremarkable medical history presented to the emergency room in the 12th week of gestation with lower right abdominal pain. On physical examination there was slight tenderness in the lower right quadrant, the uterus had normal tonus and no bleeding was observed. Bimanual examination revealed a normal cervix and tenderness of the right adnexa. Routine blood tests were normal. Transvaginal ultrasound examination demonstrated a viable fetus and normal left ovary. The right ovary was slightly enlarged, edematous and included a simple cyst measuring 50 × 34 mm. Color Doppler imaging showed normal ovarian flow. Adjacent to the ovary a long edematous mass measuring 60 × 20 mm was observed (ovarian pedicle).
Adnexal torsion was suspected but, because of the operative risk associated with the woman's pregnancy and her relatively mild clinical symptoms, further evaluation was carried out. Detailed ultrasound examination clearly demonstrated the whirlpool sign, which confirmed the diagnosis of torsion (Figure 4 and Videoclip S4).
Laparoscopic findings included torsion of the right adnexa and discolored ovary with areas of hemorrhagic necrosis. After detorsion and ovarian cyst aspiration the ovarian appearance returned to normal on ultrasound imaging. The patient's pregnancy continued uneventfully.
Case 3: torsion in an asymptomatic woman
A 30-year-old woman, gravida 5 para 3 abortions 2, presented to the emergency room several hours after the abrupt onset of lower left abdominal pain associated with nausea, which resolved at the time of examination. On physical examination the lower abdomen was soft, with slight tenderness of the left adnexa. Ultrasound examination revealed a slightly enlarged left ovary with normal appearance on Doppler imaging (Figure 5a and b and Videoclip S5). Torsion was suspected but the diagnosis was not conclusive because her pain had resolved. Ultrasound examination was repeated the following day and whirlpool sign of the left ovarian pedicle was seen (Videoclip S6). Despite the lack of clinical symptoms and absence of abdominal tenderness, laparoscopy was performed within hours. The left adnexa were hyperemic and edematous with black foci of hemorrhagic necrosis, compatible with very recently torsed ovary (Figure 5c and Videoclip S7).
Adnexal torsion is a common gynecological emergency with a highly variable clinical presentation, ranging from severe intractable pain accompanied by nausea and vomiting, to asymptomatic presentation, which might signal either necrotic adnexa or non-compromized vascularly twisted ovary. Sonographic signs of torsion include abnormal ovarian position (ovary in the pouch of Douglas, anterior to the uterus or in the contralateral side), ovarian enlargement with edema, ovarian or adnexal mass, free fluid in the cul de sac and decreased or absent Doppler flow in the ovary. These signs are indirect, yet when the clinical suspicion of adnexal torsion is raised in young fertile women, the common attitude is in favor of surgical intervention, in view of the potential for irreversible damage to the adnexa and the low operative risk. However, when a diagnosis of torsion is made based on these sonographic and clinical signs, some series have reported a correlation between preoperative diagnosis and surgical findings of less than 50%5.
In contrast, the whirlpool sign is a unique, direct, sonographic sign which represents the twisted pedicle—the torsion itself. While sonographic identification of the whirlpool sign requires some expertise, it seems to be more accurate for diagnosis of torsion and may be especially valuable in cases with atypical clinical presentation, when a definitive preoperative diagnosis of adnexal torsion is important.
The following are examples of clinical situations in which a preoperative diagnosis of torsion should be confirmed.
Torsion in pregnancy: in this challenging situation the diagnosis is difficult as the clinical symptoms—lower abdominal pain, vomiting, leukocytosis and palpable mass—could relate to the pregnancy even in cases with a known ovarian mass. In pregnancy the operative risk to the mother and fetus is higher and the procedure is more technically complicated, making the risk of unnecessary intervention weigh heavier against the possible benefit.
Sonographic findings common to torsion without the classical clinical presentation (i.e. asymptomatic women).
Typical clinical symptoms with normal sonographic appearance of the ovaries, when only some adnexal elements are involved, such as the Fallopian tube in a torsed paraovarian cyst.
Expected complicated surgery, for example in patients with previous abdominal surgical procedures, hysterectomy or severe endometriosis.
In such cases the sonographic whirlpool sign could be the key for decision-making regarding the management of the patient. Further studies are needed to establish the routine application of the whirlpool sign in the diagnosis of torsion and to ascertain its sensitivity and specificity.
SUPPORTING INFORMATION ON THE INTERNET
The following supporting information may be found in the online version of this article:
Videoclip S1 Gray-scale imaging of a twisted ovarian ligament; carets indicate the twists in the sagittal plane. WS, whirlpool sign.
Videoclip S2 The characteristic spiral whirlpool sign on color Doppler imaging.
Videoclip S3 The whirlpool sign showing torsion of the pedicle of a sactosalpinx. WS, whirlpool sign; Ut, uterus; OvL, ovarian ligament; OV, ovary.
Videoclip S4 Ultrasound imaging of a case of torsion with a simple cyst in early pregnancy; carets indicate the twists of the pedicle. Ut, uterus; WS, whirlpool sign.
Videoclip S5 The slightly enlarged edematous left ovary with flow visible on power Doppler imaging.
Videoclip S6 Whirlpool sign of the left ovarian pedicle on ultrasound imaging.
Videoclip S7 Torsion of the ovarian ligament involving the Fallopian tube and the edematous ovary with areas of necrosis, as seen during laparoscopy.