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CT Features of Adnexal Torsion

¹ Department of Radiology, Hadassah-Hebrew University Medical Center, PO Box 12227, Jerusalem, Israel, 91121.
² Department of Gynecology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
³ Department of Radiology, Shaare Zedek Medical Center, Jerusalem, Israel.

Received January 15, 2006; accepted after revision October 31, 2006.

 
Address correspondence to T. Sella (tamarse{at}hadassah.org.il).

Abstract

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OBJECTIVE. Adnexal torsion is most commonly a clinical diagnosis, often aided by sonographic findings. At times, the clinical presentation can mimic nongynecologic causes of acute lower abdominal pain. In these cases, CT may be the initial imaging study. The purpose of this study was to define the CT features associated with adnexal torsion.

CONCLUSION. On CT, a well-defined adnexal mass abnormally located in the pelvis with ipsilateral deviation of the uterus in a woman or girl with lower abdominal pain should raise the suspicion of adnexal torsion. Inflammatory signs on CT suggest the presence of necrosis.

Keywords: adnexa • adnexal torsion • CT • pelvic imaging • women's imaging

Introduction

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Adnexal torsion is a gynecologic emergency caused by partial or complete twisting of the mesovarium. Early surgical intervention is needed to save the ovary. The diagnosis is most commonly a clinical one aided by sonography. However, because the clinical presentation of adnexal torsion can mimic other causes of acute abdominal pain, CT sometimes is performed in equivocal cases. In addition, if the clinical presentation is unclear, CT may be the initial diagnostic imaging examination performed. Thus familiarity with the spectrum of CT characteristics of adnexal torsion is essential for prompt recognition of this potentially serious condition. Our review of the literature revealed descriptions of the CT characteristics of adnexal torsion in only a few small series of patients [1-3]. The goal of our study was to define the CT features associated with adnexal torsion and to correlate these features with the clinical, sonographic, surgical, and pathologic findings. To our knowledge, our series is the largest described in the literature.

Materials and Methods

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A search of two university hospital registries for the years 1995-2005 identified the records of 328 patients with surgically proven adnexal torsion. Thirty-five (10.7%) of these patients underwent CT as part of a preoperative evaluation. CT examinations were performed with one of the following scanners: 2400 Elite scanner (Elscint), helical Twin Flash scanner (Philips Medical Systems), 4-MDCT MX 8000 scanner (Philips Medical Systems). The standard parameters for abdominal CT for each machine were used, that is, 5-mm slice thickness with a table increment of 5 mm and a pitch of 1-1.5. Tube current and kilovoltage were adjusted to the type of machine and size of the patient. Oral contrast material (1,000 mL meglumine ioxithalamate, Telebrix 3%, Guerbet) was administered to all patients 90 minutes before CT. Intravenous contrast material (100 mL meglumine ioxithalamate, Telebrix 30, Guerbet) was administered to all but four patients according to a standard injection protocol at an injection rate of 2.5 mL/s.

Clinical information obtained from the patients' medical records included age, medical history, and clinical signs and symptoms at presentation. Fever was defined as body temperature exceeding 37.5°C. Abdominal pain was defined as lower abdominal pain, flank pain, or both. The onset of abdominal pain was defined as acute when occurring up to 24 hours before admission, subacute if it had lasted up to 1 week, and chronic if it had persisted for more than 1 week before admission. Laboratory values were reviewed with emphasis on inflammatory markers. An elevated WBC count was defined as greater than 10,000/mm³. Sonographic findings were extracted from the charts, and images were reviewed when available. Hospital institutional review board approval was obtained for this retrospective study.

Two radiologists, each with more than 10 years of experience in body imaging, retrospectively reviewed all CT scans. For each adnexal mass found on CT scans, the size, nature (cystic, solid, or combined), borders, and location within the pelvis were assessed. For adnexal findings with a cystic component, mural thickness was measured and defined as abnormal when greater than 3 mm. Uterine location, visualization of the contralateral ovary, and changes in the adjacent pelvic fat and blood vessels also were assessed. Surgical and pathologic findings were recorded separately, and the radiologists evaluating the CT scans were blinded to these findings. Data were collected and analyzed with descriptive statistics.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1 —26-year-old woman with torsion of right ovarian dermoid. Unenhanced CT scan shows well-defined fat-containing mass (M) to left of uterus (U). Uterus is deviated to right. Infiltration of fat (arrow) anterior to twisted mass is evident. Pathologic examination revealed necrosis.

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Sonographic Findings
Sonography was performed on 33 (94%) of the 35 patients, revealing an adnexal mass in 31 patients. The size range of the lesions was 3-20 cm (mean, 9.5 cm). Findings were solid on sonography in seven (23%), simple cyst in three (10%), multiloculated cystic in 10 (32%), and mixed solid and cystic in 11 (35%) of the 31 cases. In 25 patients, the sonographic study preceded CT. Torsion was not diagnosed in 16 of these 25 patients. The sonographic findings were interpreted as hemorrhagic corpus luteum cyst in three patients, pedunculated necrotic myoma in two patients, uncomplicated dermoid cyst in two patients, benign cyst in two patients, pelvic mass unrelated to the adnexa in one patient, and endometrioma in one patient. In the other five patients, the adnexa appeared abnormal on sonography, but a specific diagnosis was not made, and patients were referred for CT for further evaluation. The correct diagnosis of adnexal torsion was made on sonography before CT in nine cases and was later confirmed on CT. Doppler sonography was performed on only 11 (33%) of 33 patients, revealing abnormal adnexal vascular flow in six (55%) and normal flow in five (45%) of the patients. On the basis of clinical and sonographic findings, the diagnosis of adnexal torsion was made before CT in only nine (26%) of 35 cases.

Surgery
Twenty-five (71%) of the 35 patients underwent laparotomy, and 10 (29%) underwent laparoscopic surgery. The surgical finding was full torsion (at least 360°) in 29 (83%) and partial torsion (90-270°) in six (17%) of the patients. Torsion of the ovary and fallopian tube was found in 21 (60%), torsion of the ovary alone in 13 (37%), and isolated tubal torsion in only one (3%) of the patients. The surgical procedure included total abdominal hysterectomy and bilateral salpingo-oophorectomy in 11 (31.5%), unilateral salpingo-oophorectomy in 13 (37%), removal of a benign ovarian tumor with preservation of the ovary in three (8.5%), adnexal detorsion and cyst aspiration in four (11.5%), and adnexal detorsion with no further intervention in four (11.5%) of the patients.

Pathology
Pathologic examination revealed an ovarian cyst or mass in 25 (71%) of the 35 patients. The mean age of patients with an underlying ovarian lesion was 44 years (median, 45 years); the mean age of patients with no underlying lesion was 25 years (median, 19 years). Two patients with an ovarian mass were premenarchal, and both had a mature teratoma. The most common histologic diagnosis was mature teratoma (Fig. 1), found in eight (32%) of the 25 patients. Additional histologic diagnoses included benign cystadenoma in six (24%), simple cyst in three (12%), cystadenofibroma in three (12%), fibroma in three (12%), fibrothecoma in one (4%), and Brenner tumor in one (4%) of the patients. Necrosis of the torsed adnexa was encountered at pathologic examination in 20 (57%) of the 35 cases.

CT Findings
For 32 patients, CT was performed up to 1 week after admission, the interval ranging from less than 24 hours to 1 week (mean, 1.7 days; median, 1.5 days). Three patients underwent CT before admission to the hospital for further evaluation of the CT finding. Adnexal enlargement was found on CT of all patients, the maximal diameter ranging from 4 to 20 cm (mean, 9.5 cm; median, 10 cm). Abnormalities were found equally on the right and left sides (on the right in 18 and on the left in 17 patients). All of the torsed adnexa had well-defined smooth margins on CT. In 28 (80%) of the cases, the torsed adnexa had at least a partially cystic component on CT (Figs. 2A and 2B), and in one half of these cases mural thickening was present. The adnexal structure involved was found in an abnormal location in the pelvis in 22 (63%) of the patients. One half of these abnormalities were on the contralateral side of the pelvis (Fig. 3), and the other half were found in a midline position. Five of the 11 midline lesions were in a far posterior location, in the pouch of Douglas, and three were in a far anterior position, abutting the anterior pelvic fascia (Fig. 4). The uterus was deviated to the side of the involved adnexa in 16 (46%) of the 35 patients (Fig. 5).

View larger version (147K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —58-year-old woman with torsion of left adnexa manifesting as left flank pain. Contrast-enhanced CT scan (A) and transabdominal sonogram (B) show large midline well-defined cystic mass with thickening of posterior wall (straight arrow, A) and internal septations (curved arrows). Pathologic examination revealed necrotic adnexa with no underlying tumor.

View larger version (145K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —58-year-old woman with torsion of left adnexa manifesting as left flank pain. Contrast-enhanced CT scan (A) and transabdominal sonogram (B) show large midline well-defined cystic mass with thickening of posterior wall (straight arrow, A) and internal septations (curved arrows). Pathologic examination revealed necrotic adnexa with no underlying tumor.

View larger version (147K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3 —41-year-old woman with left adnexal torsion. Contrast-enhanced CT scan shows abnormally located left ovary (LO) on contralateral side of pelvis in far posterior location. Ipsilateral fallopian tube (arrow) is distended. Right ovary (asterisk) is in normal position. Uterus (U) is deviated anteriorly. At surgery, ovary and fallopian tube were found to be torsed, and underlying mass was found. Pathologic examination revealed necrotic cystadenofibroma of ovary.

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4 —42-year-old woman with torsion of right ovary manifesting as chronic right lower abdominal pain that gradually increased in severity. Contrast-enhanced CT scan shows enlarged right cystic ovary (RO) crossing midline of pelvis anterior to uterus (U). Spiral appearance of adnexal vascular pedicle (arrow) is whirl sign. Pathologic examination revealed serous cystadenoma without necrosis.

View larger version (145K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5 —50-year-old woman with torsion of left adnexa manifesting as acute left abdominal pain. Contrast-enhanced CT scan shows left ovarian mass (LO) crossing midline to right side. Twisted vascular pedicle and dilated fallopian tube (arrow) are evident to left of mass. Uterus (U) is deviated to side of torsed adnexa. Right ovary, which contains small simple cyst (asterisk), is in normal location. At surgery, ovary and fallopian tube were found to be torsed, and underlying mass was found. Pathologic examination revealed necrosis of left ovary and fallopian tube with ovarian mucinous cystadenoma.

View larger version (145K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6 —20-year-old woman with acute lower abdominal pain. Contrast-enhanced CT scan shows torsion of left ovary (LO) in right side of pelvis. Right ovary (RO) is in normal location, and uterus (U) is markedly deviated to involved left side. Mild fat stranding (arrow) anterior to torsed ovary is evident. Pathologic examination revealed necrotic adnexa with no underlying mass. B = bladder.

View larger version (144K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7 —49-year-old woman with torsion of right ovary manifesting as subacute right lower abdominal pain. Contrast-enhanced CT scan shows enlarged myomatous uterus (U). Right ovary is in normal position but is cystic in appearance with plasma-erythrocyte level (straight arrow) suggestive of internal hemorrhage. Thickened twisted pedicle (curved arrow) is posterior to mass. Pathologic examination revealed torsed right ovary with hemorrhagic necrosis.

Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Twisting of the adnexal vascular pedicle results in venous compromise followed by arterial occlusion and ischemia of the adnexa with subsequent necrosis. Although this condition is a surgical emergency, the diagnosis is often missed [4]. The clinical presentation is nonspecific and can mimic other abdominal conditions, such as tuboovarian abscess, acute appendicitis, torsion of epiploic appendix, diverticulitis, and rupture of a corpus luteum. Findings at physical examination are nonspecific, and the examination is often limited by pain. Although it is generally considered an acute condition, adnexal torsion occasionally takes a subacute or intermittent chronic course, further complicating the diagnosis [5].

In our study, the clinical presentation of adnexal torsion was not acute in 40% of the patients. The pain was nonspecific, rarely manifesting as flank pain, which is a symptom of renal colic. Gastrointestinal symptoms such as nausea and vomiting were quite common (46%). No correlation was found between these symptoms and the presence of adnexal necrosis. Peritoneal signs were present in 34% of the patients, all of whom had complete torsion and pathologically confirmed necrosis of the adnexa. Laboratory tests are usually not helpful in the diagnosis of adnexal torsion. Imaging therefore plays a central diagnostic role.

Sonography is usually the initial imaging technique performed when adnexal torsion or another gynecologic pathologic condition is suspected. The sonographic findings of adnexal torsion are nonspecific and include the presence of a cystic, solid, or complex pelvic mass with or without mural thickening or the presence of pelvic ascites [6]. A more specific sonographic sign of torsion of a normal ovary is evidence of multiple small homogeneous cysts in the periphery of an enlarged ovary [7]. However, such an appearance in a young fertile women is not sufficient for a diagnosis because a normal ovary with prominent follicles has a similar appearance.

The added value of color Doppler sonography in the diagnosis of adnexal torsion has not been fully established. In several studies with small numbers of patients, investigators [6-9] have concluded that the diagnosis or exclusion of adnexal torsion cannot be reliably based on the absence or presence of flow on color Doppler sonography. Those authors remarked that normal blood flow commonly is seen in torsed adnexa. The identification of a whirlpool sign on Doppler sonography has been suggested pathognomonic of adnexal torsion [10]; however, this sign is not commonly seen. Although 94% of our patients underwent pelvic sonography, Doppler technique was used in only one third of the examinations. Doppler technique was not used in the other cases because a clinical diagnosis of adnexal torsion was not suspected before sonography. Normal adnexal blood flow was documented in almost one half of the patients who underwent Doppler sonography, a finding consistent with previous reports [9]. The presence of normal blood flow can be attributed to partial torsion, torsion and then detorsion of the adnexa, or the presence of collateral blood supply through branches of the uterine artery. The complexity of reaching a correct diagnosis of adnexal torsion is illustrated by the fact that only 26% of the patients in this study were believed to have adnexal torsion on the basis of clinical and sonographic findings.

Our series is, to our knowledge, the largest to date in which the CT findings of surgically proven adnexal torsion have been assessed. In all cases the CT finding was a well-defined enlarged adnexal structure with a smooth border. Deviation of the uterus to the involved side and misplacement of the torsed structure in the pelvis (to the contralateral side or a midline position) proved to be important CT signs of adnexal torsion. The combination of both of these signs was found in 40% of the patients in this study. When present in the appropriate clinical setting, these signs should raise suspicion of adnexal torsion.

To accurately diagnose adnexal misplacement, it is imperative to clearly visualize the normal uninvolved ovary. Another important CT finding in our study was infiltration of the periadnexal fat. In all cases in which this sign was visualized, pathologic examination revealed necrosis. Absence of periadnexal fat stranding, however, does not exclude necrosis. The finding of necrosis at pathologic examination was more common than the associated CT finding.

The largest previous series of CT findings of adnexal torsion included 25 patients and was described by Rha et al. [3]. Those authors concluded that the most important CT findings are tubal thickening, cystic mass with a smooth thickening wall, ascites, and uterine deviation to the twisted side. These findings are consistent with our observations, except for tubal thickening, which we found in only six patients. Visualization of the fallopian tube is challenging when a large complex adnexal mass is present on CT scans. This difficulty may explain why tubal involvement was found in our patients less commonly on CT than at pathologic examination. Adnexal hemorrhage is another previously described feature of adnexal torsion [1, 3]. We found this feature difficult to assess because most of the CT scans in our study were contrast enhanced. On unenhanced images, hemorrhage can manifest as an area of increased attenuation. Contrast enhancement limits the ability to evaluate this sign. MRI may be helpful in the diagnosis of hemorrhage [2, 3] but is not always available in an acute care setting. Our study specifically emphasized the importance of displacement of the involved adnexa as an important clue in the CT diagnosis of adnexal torsion. Ghossain et al. [11] suggested that if serial CT is available, a change in the configuration of internal ovarian elements may aid in the diagnosis of adnexal torsion. Adnexal torsion usually is acute, however; therefore, serial imaging is uncommon.

An underlying ovarian lesion is commonly the cause of adnexal torsion and is usually benign. In our study, as reported earlier by Rha et al. [3], these lesions were invariably benign, most commonly mature teratoma. This finding may be related to the fact that most ovarian lesions are benign. In addition, fixation of the ovaries by a malignant tumor theoretically can limit their mobility and prevent torsion. Further studies are needed to evaluate this hypothesis.

CT appearance was insufficient for accurate detection and prediction of the nature of an underlying pathologic process causing torsion. In our series 80% of torsed adnexa were deemed at least partially cystic on CT; pathologic examination, however, showed that only 48% of the lesions were cystic. In some cases, necrosis was the cause of a cystic appearance on CT.

Our study had a number of limitations, most of them inherent to the nature of the study. Although we present the largest, to our knowledge, series of cases of CT depiction of adnexal torsion to date, the number of patients was still relatively small. Adnexal torsion has an uncommon occurrence, estimated as the cause of only 2.7% of gynecologic emergencies in the United States [12], and most of the patients do not undergo CT. It therefore is difficult to collect a larger series of cases. Our observations were subject to selection bias because only patients referred for CT were included, and these patients usually posed a complicated diagnostic challenge. The retrospective nature of this study also was a limiting factor, especially in view of the major technical advancements in CT and sonography over the long study period. Further examination of this topic with a large prospective study based on modern imaging technology may be warranted.

Evaluation of adnexal torsion with CT is infrequent; however, recognition of the CT findings of this potentially serious condition is extremely important. In cases of lower abdominal pain in a woman or girl, the CT finding of a smooth adnexal mass abnormally located in the pelvis with ipsilateral deviation of the uterus should raise suspicion of adnexal torsion.

References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Ghossain MA, Buy JN, Bazot M, et al. CT in adnexal torsion with emphasis on tubal findings: correlation with US. J Comput Assist Tomogr 1994; 18:619 -625[Medline]
2. Kimura I, Togashi K, Kawakami S, et al. Ovarian torsion: CT and MR imaging appearance. Radiology 1994;190 : 337-341[Abstract/Free Full Text]
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7. Graif M, Itzchak Y. Sonographic evaluation of ovarian torsion in childhood and adolescence. AJR 1988;150 : 647-649[Abstract/Free Full Text]
8. Rosado WM Jr, Trambert MA, Gosink BB, et al. Adnexal torsion: diagnosis by using Doppler sonography. AJR1992; 159:1251 -1253[Free Full Text]
9. Pena JE, Ufberg D, Cooney N, Denis AL. Usefulness of Doppler sonography in the diagnosis of ovarian torsion. Fertil Steril 2001; 75:1041 -1042[CrossRef][Medline]
10. Vijayaraghavan SB. Sonographic whirlpool sign in ovarian torsion. J Ultrasound Med 2004;23 : 1643-1649[Abstract/Free Full Text]
11. Ghossain MA, Buy JN, Sciot C, Jacob D, Hugol D, Vadrot D. CT findings before and after adnexal torsion: rotation of a focal solid element of a cystic adjunctive sign in diagnosis. AJR1997; 169:1343 -1346[Free Full Text]
12. Schraga ED, Kulkarni R, Blanda M. Ovarian torsion. eMedicine Web site. Available at: www.emedicine.com/emerg/topic353.htm. Updated January 29, 2007. Accessed March 14, 2007

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This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hiller, N. Articles by Sella, T. Search for Related Content PubMed PubMed Citation Articles by Hiller, N. Articles by Sella, T. Social Bookmarking                      What's this?