Ovarian torsion: Case–control study comparing the sensitivity and specificity of ultrasonography and computed tomography for diagnosis in the emergency department

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Abstract

Objective

Evaluate the sensitivity and specificity of pelvic ultrasound (US) and abdominopelvic computed tomography (CT) for the identification of ovarian torsion in women presenting to the emergency department with acute lower abdominal or pelvic pain.

Materials and methods

This is a retrospective study of 20 cases of ovarian torsion and 20 control patients, all of whom had both US and CT performed in the emergency department. Two radiologists who were blinded to clinical data interpreted all studies as (1) demonstrating an abnormal ovary or not, and (2) suggestive of torsion or not. Sensitivity, specificity and interobserver variation were calculated for each imaging modality.

Results

Pelvic US was interpreted as demonstrating an abnormal ovary in 90.0% of ovarian torsion cases by reader 1, and in 100.0% by reader 2, whereas CT was interpreted as revealing an abnormal ovary in 100.0% of torsion cases by both readers. Pelvic US for ovarian torsion was 80.0% sensitive (95% CI, 58.4–91.9%) and 95.0% specific (95% CI, 76.4–99.1%) for reader 1, while 80.0% sensitive (95% CI, 58.4–91.9%) and 85.0% specific (95% CI, 64.0–95.0%) for reader 2. Interobserver agreement for pelvic US was fair (Kappa = 0.60). Abdominopelvic CT for ovarian torsion was 100.0% sensitive (95% CI, 83.9–100.0%) and 85.0% specific (95% CI, 64.0–94.5%) for reader 1, while 90.0% sensitive (95% CI, 69.9–97.2%) and 90.0% specific (95% CI, 69.9–97.2%) for reader 2. Interobserver agreement was excellent (Kappa = 0.85).

Conclusion

The diagnostic performance of CT is not shown to be significantly different from that of US in identifying ovarian torsion in this study. These results suggest that when CT demonstrates findings of ovarian torsion, the performance of another imaging exam (i.e. US) that delays therapy is unlikely to improve preoperative diagnostic yield.

Introduction

Ovarian torsion is a rare but serious cause of acute abdominal and pelvic pain in women, accounting for 2.7% of gynecologic emergencies [1]. Associated clinical signs and symptoms of torsion are nonspecific, overlapping an extensive range of gynecologic, genitourinary, and gastrointestinal etiologies of pain [2], [3], [4], [5], [6], [7]. Therefore, the workup for women presenting to the emergency department (ED) with acute lower abdominal or pelvic pain often involves diagnostic imaging with either ultrasound (US) or computed tomography (CT) [4], [6], [8].

Pelvic US has traditionally been considered the optimal imaging modality for diagnosing ovarian torsion due to its ability to directly evaluate both ovarian anatomy and perfusion, as well as its low cost and lack of radiation. However, US can be limited by inter-operator variability, limited nighttime availability in smaller community hospitals, and limited utility for diagnosing non-gynecologic etiologies of pain. Further, the sensitivity of pelvic US for torsion is suboptimal, with false negative rates as high as 45–61% when Doppler evaluation is relied upon for evaluating blood flow [4], [6], [7].

Abdominopelvic CT frequently precedes pelvic US in the workup of women presenting with acute undifferentiated lower abdominal or pelvic pain [4], [8], [9], [10]. While findings of ovarian torsion have been described on CT [4], [5], [10], [11], [12], numerous studies and review articles maintain that pelvic US is superior for this indication [5], [10], [13], [14], [15]. Nevertheless, some authors have proposed that if CT demonstrates normal morphology of the ovaries then torsion can be excluded, thus obviating the need for further imaging work-up or surgical exploration [8]. These authors still recommend that pelvic US be performed in indeterminate cases, or when the adnexae are abnormal and there is persistent clinical concern for ovarian torsion.

In light of the imperfect diagnostic performance of pelvic US, and given the suggestion that CT can exclude torsion, the primary aim of this study was to compare the diagnostic performance of pelvic US and CT in women presenting to the ED with acute lower abdominal or pelvic pain related to ovarian torsion.

Section snippets

Materials and methods

This multicenter, retrospective, case–control study was approved by our institutional review board, and the need for informed consent was waived. It was conducted in accordance with the Health Insurance Portability and Accountability Act. Subjects were identified through query of the electronic medical record (EMR) at two urban hospitals from 3/1/2005 through 7/31/2010. The start date corresponds to the introduction of electronic medical records. The first site is a large urban academic level I

Results

Patient clinical characteristics are presented in Table 1. The cases and controls were age-matched, with mean age of 40.1 years (range, 18.0–59.0). The distribution of pain was similar between cohorts, as were rates of fever, leukocytosis, and nausea. The only statistically significant difference was the presence of vomiting in patients with ovarian torsion, which nevertheless is unlikely to be of clinical significance in differentiating torsion from other causes of acute pain in women. In

Discussion

Ovarian torsion is a rare but serious gynecologic emergency. Urgent surgical detorsion successfully preserves ovarian function in over 90% of cases [18], whereas delayed diagnosis may lead to necrosis, rupture, infection, peritonitis, and possibly death [2], [12], [15], [18], [19]. Currently, laparoscopic surgical evaluation of the ovaries remains the gold standard for diagnosis because diagnostic imaging has been considered unreliable [1], [3], [4], [6], [10], [20]. To our knowledge, this is

Conflict of interest statement

None of the authors has any conflict of interest.

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