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Differentiation between right tubo-ovarian abscess and appendicitis using CT—A diagnostic challenge
Clinical Radiology 66 (2011) 1030e1035
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.elsevierhealth.com/journals/crad
Original Paper
Differentiation between right tubo-ovarian abscess and appendicitis using CTdA diagnostic challenge I. Eshed a, *, O. Halshtok a, Z. Erlich b, R. Mashiach c, M. Hertz a, M.M. Amitai a, O. Portnoy a, L. Guranda a, N. Hiller d, S. Apter a a
Department of Diagnostic Imaging, The Sheba Medical Center, Tel-Hashomer, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel b Computer Science Department, Open University, Tel Aviv, Israel c Department of Obstetrics and Gynecology, The Sheba Medical Center, Tel-Hashomer, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel d Department of Radiology, Hadassah-Hebrew University Medical Center, Mount Scopus, Israel
article in formation Article history: Received 10 March 2011 Received in revised form 2 May 2011 Accepted 10 May 2011
AIM: To determine CT features that can potentially differentiate right tubo-ovarian abscess (TOA) from acute appendicitis (AA; including abscess formation). MATERIALS AND METHODS: The abdominal computed tomography (CT) images of 48 patients with right-sided TOA (average age 39.3 9.8 years) and 80 patients (average age 53.5 19.9 years) with AA (24 with peri-appendicular abscess) were retrospectively evaluated. Two experienced radiologists evaluated 12 CT signs (including enlarged, thickened wall ovary, appendix diameter and wall thickness, peri-appendicular fluid collection, adjacent bowel wall thickening, fat stranding, free fluid, and extraluminal gas) in consensus to categorize the studies as either TOA or AA. The diagnosis and the frequency of each of the signs were correlated with the surgical and clinical outcome. RESULTS: Reviewers classified 92% cases correctly (TOA ¼ 85%, AA ¼ 96.3%), 3% incorrectly (TOA ¼ 6.3%, AA ¼ 1.3%); 5% were equivocal (TOA ¼ 8.3%, AA ¼ 2.5%). In the peri-appendicular abscess group reviewers were correct in 100%. Frequent findings in the TOA group were an abnormal ovary (87.5%), peri-ovarian fat stranding (58.3%), and recto-sigmoid wall thickening (37.5%). An abnormal appendix was observed in 2% of TOA patients. Frequent findings in the AA group were a thickened wall (32.5%) and distended (80%) appendix. Recto-sigmoid wall thickening was less frequent in AA (12.5%). The appendix was not identified in 45.8% of the TOA patients compared to 15% AA. CONCLUSIONS: In the presence of a right lower quadrant inflammatory mass, peri-ovarian fat stranding, thickened recto-sigmoid wall, and a normal appearing caecum, in young patients favour the diagnosis of TOA. An unidentified appendix does not contribute to the differentiation between TOA and peri-appendicular abscess. Ó 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction * Guarantor and correspondent: I. Eshed, Department of Diagnostic Imaging, The Sheba Medical Center, Tel Hashomer, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Tel.: þ972 3 5302498; fax: þ972 3 5302220. E-mail address: [email protected] (I. Eshed).
Tubo-ovarian abscess (TOA) is a late complication of pelvic inflammatory disease, usually detected by ultrasonography. In women with equivocal ultrasound findings further evaluation is made by computed tomography (CT).
0009-9260/$ e see front matter Ó 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2011.05.005
I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
The majority of TOA are unilateral, the most common CT finding being a multilocular septated mass in the adnexal location with fluid density and a thick, uniformly enhancing wall.1 In the case of a right-sided TOA, this process may mimic the CT appearance of acute appendicitis (AA), especially when the latter is complicated by a peri-appendicular abscess (PAA).2,3 Clinical findings of right pelvic pain, fever, and leukocytosis are key features suggesting TOA, but can also be found in AA. It is important to differentiate these entities early in the course of the disease, preferably in the emergency room. An incorrect diagnosis precludes proper management as TOA is treated by the gynaecologist and AA by the general surgeon, often using different treatment protocols. The sequelae and follow-up of these two entities is also different. Hence CT has a major role in establishing the correct diagnosis, which is essential in avoiding unnecessary surgery3 or determining the ability to drain the TOA. To the authors’ knowledge, the CT features differentiating right TOA from AA (including abscess formation) have not been systematically investigated. Thus the aim of the present study was to determine the CT signs that can potentially differentiate these two entities.
Materials and methods Patients A total of 50 patients with right-sided TOA (mean age 39.9 11 years) and 84 patients (52 20 years) with AA (including 24 with PAA) were identified through the hospital computerized archive. They were selected by pursuing the medical records of all female patients with a diagnosis (surgical and clinical) of either TOA or AA including PAA, treated at our medical centre over a 6 year period (January 2002 through December 2007). CT protocols in all patients included oral bowel contrast medium and intravenous contrast administration. Subjects with a unilateral left-sided TOA were excluded.
Image interpretation Based on the literature1,4e6 and our CT experience, 12 CT signs were chosen that were felt potentially crucial to the differential diagnosis. The 12 CT signs chosen were 1: a complex adnexal mass d a fluid-filled cavity that includes the ovary with a thickened, enhancing wall 2; peri-ovarian fat stranding 3; diameter of the appendix (<6 mm, 6 mm) 4; appendicular wall thickness (<3 mm, 3 mm) 5; appendix not identified 6; peri-appendicular fluid collection 7; thickened recto-sigmoid wall (>3 mm) 8; thickened caecal wall (>3 mm) 9; thickened small bowel wall (>3 mm) 10; peri-caecal fat stranding 11; free fluid in pelvis 12; extraluminal gas. Using these signs the CT studies were then categorized as either TOA or AA, sub-grouped as with and without abscess formation. This categorization was performed by two experienced radiologists, who reviewed the CT examinations of the entire sample without knowledge of
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the original CT reports or of the clinical and surgical outcome. All diagnoses were made in consensus. A TOA was diagnosed when a complex adnexal mass d a fluid-filled cavity that includes the ovary with a thickened, enhancing wall and peri-ovarian fat stranding dwas present. AA was diagnosed when a dilated thickened wall appendix with peri-caecal fat stranding and/or thickening of the caecal wall was observed. A PAA was subclassified in the presence of a thickened wall and fluid collection in the right pelvis in addition to the above AA signs. The diagnosis noted in the original radiological report, where present, was also documented. The medical files of women diagnosed with TOA were reviewed by a senior gynaecologist who was blinded to the CT interpretation. Medical files were reviewed for clinical presentation and outcome, results of laboratory examinations, diagnostic tests, such as ultrasound, and interventional procedures.
Statistical analysis The readers’ diagnoses were compared with the surgical and clinical outcomes, using the latter as the reference standard. The accuracy of the reviewed diagnoses and level of agreement by Kappa coefficients were calculated. Furthermore, the frequency of the presence of each of the 12 CT signs in the surgical and clinical TOA and AA with and without PAA were calculated. The association of each sign with the surgical and clinical diagnosis was tested using Chi-square test.
Ethics Institutional review board permission was given for the retrospective evaluation of the CT and clinical files of patients with TOA and acute or perforated appendicitis.
Results Two patients from the initial 50 TOA group and four from the initial 84 AA group had a normal CT examination with no signs of inflammation or other disease. Diagnosis in these TOA patients was made clinically and they improved after antibiotic treatment. The four patients from the AA group underwent surgery. In three, AA was not identified at surgery. In the fourth, the Table 1 Concordance of reviewers and clinical diagnosis. Reviewed diagnosis Clinical diagnosis All AA TOA
AA without PAA TOA PAA only TOA
All AA (n ¼ 80) 77 (96.3%) 3 (3.7%) AA without PAA (n ¼ 56) 53 (94.6%) 3 (5.4%) PAA only (n ¼ 24) 24 (100%) 0 (0%)
Kappa p-Value TOA (n ¼ 48) 7 (14.6%) 0.83 41 (85.4%) TOA (n ¼ 48) 7 (14.6%) 0.81 41 (85.4%) TOA (n ¼ 48) 7 (14.6%) 0.80 41 (85.4%)
<0.001
<0.001
<0.001
AA, acute appendicitis; PAA, peri-appendicular abscess; TOA, tubo-ovarian abscess.
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I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
Table 2 Patients with incorrect or equivocal reviewer diagnosis. Patient No Age Clinical Readers diagnosis diagnosis
CT findings
1
50
TOA
PAA
2
47
TOA
PAA
3
30
TOA
PAA
4
30
TOA
Equivocal
5
29
TOA
Equivocal
6
41
TOA
Equivocal
7
34
TOA
Equivocal
8
21
AA
TOA
9
30
AA
Equivocal
10
80
AA
Equivocal
Pelvic phlegmonous mass including right ovary and bowel loop. Thickened and inflamed appendix. Pelvic abscess, involving ovary. Not “classic” TOA. Appendix not identified. Normal caecum Pelvic abscesses, involving ovary. Not “classic” TOA. Appendix not identified. Abnormal caecum. Pelvic phlegmonous mass including right ovary and bowel loop. Appendix not identified. Normal caecum. Abnormal ovaries. Not “classic” TOA. Normal appendix. Abnormal ovaries. Not “classic” TOA. Normal appendix. Slightly enlarged ovary, no fat stranding. Not “classic” TOA. Normal appendix. Enlarged ovary, thickened wall but not “classic” TOA. Normal app. Normal caecum. Normal appendix. Normal ovaries. Thickened large bowel with colitis signs. Appendix not identified. Mild peri-caecal fat stranding. Normal for age ovaries.
AA, acute appendicitis; PAA, peri-appendicular abscess; TOA, tubo-ovarian abscess.
appendix was suspected to be inflamed at surgery; however, this was not confirmed at the histopathology examination. These six patients were excluded from the study. The final group consisted of 128 patients, 48 with rightsided TOA (age 18e56 years, mean 39.3 9.8 years) and 80 with AA, including 24 with PAA (age 19e92 years, mean 53.5 19.9 years). The presence of TOA was confirmed either by ultrasound, surgery, or drainage. The original radiological reports were available for 65 patients (26 with clinical diagnosis of TOA and 37 with AA). Detailed files of 31 of the 48 patients (64%) with TOA, available in the gynaecological department, were reviewed by a senior gynaecologist. Patients in the TOA group were significantly younger than in the AA group (p < 0.01). Only eight of the 48 patients (16.7%) of the TOA group were older than 50 years, whereas 45 of the 80 patients (56.3%) of the AA group were older than 50 years (p < 0.01). The reviewers classified 118/128 cases (92%) correctly, and four (3%) incorrectly. Reviewers’ diagnosis was equivocal in six (5%) patients. The accuracy of the reviewers’ diagnosis and the Kappa measurements of agreement between reviewed and clinical diagnosis are presented in Table 1. In the TOA group (n ¼ 48 patients), reviewers were correct in 41 cases (85.4%), wrong in three (6.3%), and equivocal in 4 (8.3%). In the original radiological report
Figure 1 A 50-year-old woman with a clinical diagnosis of TOA mistakenly diagnosed as PAA. (a) A CT image showing a multilocular pelvic mass (black arrow), with a thickened enhancing wall, perilesional fat stranding (*), and a small amount of ascites (arrowhead) as well as a thickened wall appendix (white arrow). (b) The coronal reformatted CT image clearly shows the abnormal appendix.
(available for 26 patients with a clinical diagnosis of TOA), readers were correct in 18 cases (69%), wrong in three (11%) and equivocal in five (19%). Of the entire AA group (n ¼ 80 patients), reviewers correctly identified 77 cases (96.3%), erred in one case (1.3%), and were equivocal in two cases (2.5%). The three
I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
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Table 3 Frequency of radiological signs in tubo-ovarian abscess (TOA) and acute appendicitis (AA) subgroups. CT sign
Clinical diagnosis
Abnormal ovarya Peri-ovarian fat stranding Extraluminal gas Small bowel wall thickening Recto-sigmoid wall thickening Appendix diameter 6 mm Appendix wall thickness 3 mm Appendix not identified Peri-appendiceal fluid collection Caecal wall thickening Peri-caecal fat stranding Free pelvic fluid
TOA (n ¼ 48)
AA (n ¼ 80) All (n ¼ 80)
Without PAA (n ¼ 56)
PAA only (n ¼ 24)
42 (87.5%) 28 (58.3%) 6 (12.5%) 15 (31.3%) 18 (37.5%) 1 (2%) 1 (2%) 22 (45.8%) 7 (14.6%) 8 (16.7%) 6 (12.5%) 21 (43.8%)
11 (13.8%)b 3 (3.8%)b 9 (11.3%) 20 (25%) 10 (12.5%)b 64 (80%)b 26 (32.5%)b 12 (15%)b 24 (30%)c 69 (86.2%)b 70 (87.5%)b 23 (28.8%)
6 (10.7%)b 2 (3.6%)b 0 (0%)b 9 (16.1%) 7 (12.5%)b 50 (89.3%)b 18 (32.1%)b 7 (12.5%)b 0 (0%)b 47 (83.9%)b 48 (85.7%)b 13 (23.2%)c
5 (20.8%)b 1 (4.2%)b 9 (37.5%)c 11 (45.8%) 3 (12.5%)c 14 (58.3%)b 8 (33.3%)b 5 (20.8%)c 24 (100%)b 22 (91.7%)b 22 (91.7%)b 10 (41.7%)
PAA, peri-appendicular abscess. a Thickened, enhancing ovarian wall with fluid density. b p < 0.01. c p < 0.05.
latter cases were in the AA without abscess formation group (n ¼ 56). In the PAA group (n ¼ 24), reviewers were correct in all cases (100%). In the original radiological report (available for 37 patients with a clinical diagnosis of AA), readers were correct in all cases. The CT findings in the 10 patients with an incorrect or equivocal reviewed diagnosis are presented in Table 2. Three patients with TOA were incorrectly diagnosed as having PAA (Fig 1), and one patient with AA was incorrectly diagnosed as having TOA. The values of Kappa measurement of agreement between reviewed and clinical diagnosis, 0.77e0.80,
obtained were high and significantly different from zero (Table 1). The comparison of the prevalence of each of the 12 CT signs, including the Chi-square test for the associations of each sign with the surgical and clinical diagnosis, are presented in Table 3; Fig 2 illustrates the percentage of patients showing each of the 12 CT signs in TOA and in AA (subdivided into AA without and with PAA). The most frequent findings in TOA were an abnormal ovary, peri-ovarian fat stranding, and bowel wall thickening, most often observed in the recto-sigmoid (Fig 3). The
Figure 2 Percentage of patients showing each of the 12 signs in the TOA group and in the AA with and without PAA group.
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I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
Figure 3 A 43-year-old woman with a clinical diagnosis of TOA. The CT image shows a right-sided multilocular mass (black arrow), perilesional fat stranding (*), and a thickened wall sigmoid colon (arrowhead). The appendix is normal (white arrow).
appendix was not identified in nearly half of TOA (45.8%) cases compared to in 15% of the cases of AA. A dilated appendix was seen in 2% of TOA compared to 80% in AA patients. A thickened appendiceal wall was
Figure 4 A 55-year-old woman with a clinical diagnosis of PAA. The CT images show (a) a pelvic abscess containing air bubbles (black arrow) with peri-lesional fat stranding (*) and (b), which is proximal to (a), shows a thickened wall appendix (white arrow).
observed in 2% of TOA. In the AA group, the appendiceal wall could be measured in 37 patients only; a thickened appendiceal wall was seen in 26 patients (70%). In the other 43 the wall was not clearly identified. Thickening of the caecal wall and peri-caecal fat stranding were statistically less frequent (p < 0.01) in TOA patients (16.7% and 12.5%, respectively) than in the AA group (86.2% and 87.5%, respectively). The most frequent findings in the AA group were a distended appendix with a thickened wall. The ovary and periovarian fat were normal in most patients with appendicitis. Involvement of the small bowel was similar to that seen in TOA; recto-sigmoid wall thickening was, however, less frequent in AA compared to TOA. Extraluminal intralesional gas was much more frequent in patients with PAA (Fig 4) compared to TOA patients.
Discussion CT has an important role in the diagnosis of TOA, exhibiting complex fluid-attenuation collections with thickened and irregular walls.7,8 Yet, differentiation of rightsided TOA from AA, particularly when complicated by abscess formation, continues to be problematic, especially in young women.2,3 Patients in the TOA group were significantly younger than patients in the AA group. The average age reported for patients with TOA was 40e46 years,1,9 whereas AA can occur in almost every age.10,11 To the authors’ knowledge, the present study is the first to compare the CT findings of right-sided TOA and AA and PAA. In 118 out of 128 women, several non-specific CT signs appeared to correctly differentiate the two entities, in addition to the specific CT appearance of the ovary and the appendix. Peri-ovarian fat stranding and thickening of the rectosigmoid wall were CT features favouring the diagnosis of TOA, as these were rare in the cases of AA. These CT signs appeared with statistically significantly higher frequency in TOA compared to AA, without and with a PAA. These features probably represent reactivity of the neighbouring organs.1,12,13 A thickened caecal wall and peri-caecal fat stranding were signs favouring the diagnosis of AA and PAA. These CT signs are well established as typical for appendiceal disease.3,4 However, a dilated appendix with a thickened wall, a thickened caecal wall, and peri-caecal fat stranding were also found in patients with TOA. These finding were present less frequently in TOA compared to AA patients. The occurrence of these signs in TOA is less well documented in the literature. Bennett et al.2 stated that in patients with TOA, the inflammatory process may extend to involve the appendix or colon and greater omentum. Kim et al.3 recently described diffuse or focal wall thickening of the appendix in 10 women with pelvic inflammatory disease and called it “appendiceal serositis”. Radiologists should be aware of such findings as they may mimic appendicitis in women suffering from pelvic inflammatory disease, as in one of the present patients and in the 10 patients reported by Kim et al.3
I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
Extra-luminal gas bubbles were less often observed in TOA compared to PAA; however, this finding was not statistically significant. Indeed it was already reported that extraluminal gas is less frequent in TOA2 compared to PAA.14 Thus, the presence of air bubbles favours the diagnosis of a PAA. Ascites was seen in 43.8% of TOA patients; ascites is commonly found with pelvic inflammatory disease.2,3,12 However, it was seen with a similar frequency (41.7%) in the PAA group, and was not helpful in the differentiation between the two conditions. A non-visualized appendix at CT, in the absence of secondary inflammatory changes, in patients with right lower-quadrant pain has been reported as a reliable sign to exclude appendicitis.15,16 However, in the present study, a non-visualized appendix did not aid the differentiation of TOA from AA. This may have resulted from the relatively small cohort of TOA patients. In the present study, the diagnosis by two experienced radiologists had a significantly greater accuracy for the AA group than for the TOA group. The same tendency was seen in the readings of the original radiological reports. TOA was missed in seven patients. It was mistakenly assumed that the inability to visualize the appendix in the presence of a right-sided pelvic abscess indicated PAA. This assumption proved incorrect as the appendix was not seen in nearly half of the TOA patients compared with only 20.8% of the PAA patients. Therefore a non-visualized appendix is not a helpful sign in the differentiation of TOA from appendicitis, especially when the latter is associated with a PAA. Another reason for the incorrect diagnosis of TOA was the assumption that in TOA the surrounding tissues are usually inflamed. However, as these features may appear only in the later stages of TOA, this assumption led to an equivocal diagnosis in four cases. The same tendency for equivocal diagnosis was seen in the original radiological reports probably for the same reason. AA was missed in three patients; in one the ovary was enlarged and the appendix looked normal. In the other two instances the significance of thickening of the large bowel wall was underestimated in one, and the mild peri-caecal fat stranding was underestimated in the other. The limitations of the study include the retrospective nature of the study and the fact that nearly a third of the patients with TOA were only clinically confirmed and lacked pathological confirmation. A prospective evaluation of a larger cohort, specifically of female patients with rightsided abscess with a surgically proven diagnosis would strengthen the statistical analysis. Also, as reviewers had to choose between two possible pathological diagnoses (TOA and AA), the overall diagnostic accuracy might be skewed. However, the same tendency of results was seen in the
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original radiological reports in which the diagnosis was not restricted. In conclusion, in the presence of a right lower-quadrant inflammatory mass in women, several secondary CT findings were helpful in the differentiation between TOA and AA. Peri-ovarian fat stranding, thickened wall of the rectosigmoid, as well as a normal-appearing caecum, in young patients favoured the diagnosis of TOA. Extraluminal air favoured the diagnosis of a PAA abscess rather than TOA. A non-visualized appendix did not contribute to the differentiation between TOA and PAA. Differentiating some cases of TOA from acute or perforated appendicitis will probably remain a diagnostic challenge even for the experienced radiologist. Further studies with pathological correlation are needed to evaluate the changes in the right ovary in the presence of appendicitis and especially in PAA.
References 1. Hiller N, Sella T, Lev-Sagi A, et al. Computed tomographic features of tuboovarian abscess. J Reprod Med 2005;50:203e8. 2. Bennett GL, Slywotzky CM, Giovanniello G. Gynaecologic causes of acute pelvic pain: spectrum of CT findings. RadioGraphics 2002;22:785e801. 3. Kim MY, Lee YM, Suh CH, et al. Computed tomographic features of appendiceal serositis in pelvic inflammatory disease: comparison with pathological findings. J Comp Assist Tomogr 2007;31:104e8. 4. Ellis JH, Francis IR, Rhodes M, et al. CT findings in tuboovarian abscess. J Comp Assist Tomogr 1991;15:589e92. 5. Rao PM, Wittenberg J, McDowell RK, et al. Appendicitis: use of arrowhead sign for diagnosis at CT. Radiology 1997;202:363e6. 6. Rybkin AV, Thoeni RF. Current concepts in imaging of appendicitis. Radiol Clinics North Am 2007;45:411e22. vii. 7. Potter AW, Chandrasekhar CA. US and CT evaluation of acute pelvic pain of gynecologic origin in nonpregnant premenopausal patients. RadioGraphics 2008;28:1645e59. 8. Sam JW, Jacobs JE, Birnbaum BA. Spectrum of CT findings in acute pyogenic pelvic inflammatory disease. RadioGraphics 2002;22:1327e34. 9. Jeong WK, Kim Y, Song SY. Tubo-ovarian abscess: CT and pathological correlation. Clin Imaging 2007;31:414e8. 10. Unlu C, de Castro SM, Tuynman JB, et al. Evaluating routine diagnostic imaging in acute appendicitis. Int J Surg 2009;7:451e5. 11. van Randen A, Bipat S, Zwinderman AH, et al. Acute appendicitis: metaanalysis of diagnostic performance of CT and graded compression US related to prevalence of disease. Radiology 2008;249:97e106. 12. Phillips JC. A spectrum of radiologic abnormalities due to tubo-ovarian abscess. Radiology 1974;110:307e11. 13. Wilbur AC, Aizenstein RI, Napp TE. CT findings in tuboovarian abscess. AJR Am J Roentenol 1992;158:575e9. 14. Horrow MM, White DS, Horrow JC. Differentiation of perforated from nonperforated appendicitis at CT. Radiology 2003;227:46e51. 15. Ganguli S, Raptopoulos V, Komlos F, et al. Right lower quadrant pain: value of the nonvisualized appendix in patients at multidetector CT. Radiology 2006;241:175e80. 16. Nikolaidis P, Hwang CM, Miller FH, et al. The nonvisualized appendix: incidence of acute appendicitis when secondary inflammatory changes are absent. AJR Am J Roentenol 2004;183:889e92.
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.elsevierhealth.com/journals/crad
Original Paper
Differentiation between right tubo-ovarian abscess and appendicitis using CTdA diagnostic challenge I. Eshed a, *, O. Halshtok a, Z. Erlich b, R. Mashiach c, M. Hertz a, M.M. Amitai a, O. Portnoy a, L. Guranda a, N. Hiller d, S. Apter a a
Department of Diagnostic Imaging, The Sheba Medical Center, Tel-Hashomer, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel b Computer Science Department, Open University, Tel Aviv, Israel c Department of Obstetrics and Gynecology, The Sheba Medical Center, Tel-Hashomer, Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel d Department of Radiology, Hadassah-Hebrew University Medical Center, Mount Scopus, Israel
article in formation Article history: Received 10 March 2011 Received in revised form 2 May 2011 Accepted 10 May 2011
AIM: To determine CT features that can potentially differentiate right tubo-ovarian abscess (TOA) from acute appendicitis (AA; including abscess formation). MATERIALS AND METHODS: The abdominal computed tomography (CT) images of 48 patients with right-sided TOA (average age 39.3 9.8 years) and 80 patients (average age 53.5 19.9 years) with AA (24 with peri-appendicular abscess) were retrospectively evaluated. Two experienced radiologists evaluated 12 CT signs (including enlarged, thickened wall ovary, appendix diameter and wall thickness, peri-appendicular fluid collection, adjacent bowel wall thickening, fat stranding, free fluid, and extraluminal gas) in consensus to categorize the studies as either TOA or AA. The diagnosis and the frequency of each of the signs were correlated with the surgical and clinical outcome. RESULTS: Reviewers classified 92% cases correctly (TOA ¼ 85%, AA ¼ 96.3%), 3% incorrectly (TOA ¼ 6.3%, AA ¼ 1.3%); 5% were equivocal (TOA ¼ 8.3%, AA ¼ 2.5%). In the peri-appendicular abscess group reviewers were correct in 100%. Frequent findings in the TOA group were an abnormal ovary (87.5%), peri-ovarian fat stranding (58.3%), and recto-sigmoid wall thickening (37.5%). An abnormal appendix was observed in 2% of TOA patients. Frequent findings in the AA group were a thickened wall (32.5%) and distended (80%) appendix. Recto-sigmoid wall thickening was less frequent in AA (12.5%). The appendix was not identified in 45.8% of the TOA patients compared to 15% AA. CONCLUSIONS: In the presence of a right lower quadrant inflammatory mass, peri-ovarian fat stranding, thickened recto-sigmoid wall, and a normal appearing caecum, in young patients favour the diagnosis of TOA. An unidentified appendix does not contribute to the differentiation between TOA and peri-appendicular abscess. Ó 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction * Guarantor and correspondent: I. Eshed, Department of Diagnostic Imaging, The Sheba Medical Center, Tel Hashomer, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Tel.: þ972 3 5302498; fax: þ972 3 5302220. E-mail address: [email protected] (I. Eshed).
Tubo-ovarian abscess (TOA) is a late complication of pelvic inflammatory disease, usually detected by ultrasonography. In women with equivocal ultrasound findings further evaluation is made by computed tomography (CT).
0009-9260/$ e see front matter Ó 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.crad.2011.05.005
I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
The majority of TOA are unilateral, the most common CT finding being a multilocular septated mass in the adnexal location with fluid density and a thick, uniformly enhancing wall.1 In the case of a right-sided TOA, this process may mimic the CT appearance of acute appendicitis (AA), especially when the latter is complicated by a peri-appendicular abscess (PAA).2,3 Clinical findings of right pelvic pain, fever, and leukocytosis are key features suggesting TOA, but can also be found in AA. It is important to differentiate these entities early in the course of the disease, preferably in the emergency room. An incorrect diagnosis precludes proper management as TOA is treated by the gynaecologist and AA by the general surgeon, often using different treatment protocols. The sequelae and follow-up of these two entities is also different. Hence CT has a major role in establishing the correct diagnosis, which is essential in avoiding unnecessary surgery3 or determining the ability to drain the TOA. To the authors’ knowledge, the CT features differentiating right TOA from AA (including abscess formation) have not been systematically investigated. Thus the aim of the present study was to determine the CT signs that can potentially differentiate these two entities.
Materials and methods Patients A total of 50 patients with right-sided TOA (mean age 39.9 11 years) and 84 patients (52 20 years) with AA (including 24 with PAA) were identified through the hospital computerized archive. They were selected by pursuing the medical records of all female patients with a diagnosis (surgical and clinical) of either TOA or AA including PAA, treated at our medical centre over a 6 year period (January 2002 through December 2007). CT protocols in all patients included oral bowel contrast medium and intravenous contrast administration. Subjects with a unilateral left-sided TOA were excluded.
Image interpretation Based on the literature1,4e6 and our CT experience, 12 CT signs were chosen that were felt potentially crucial to the differential diagnosis. The 12 CT signs chosen were 1: a complex adnexal mass d a fluid-filled cavity that includes the ovary with a thickened, enhancing wall 2; peri-ovarian fat stranding 3; diameter of the appendix (<6 mm, 6 mm) 4; appendicular wall thickness (<3 mm, 3 mm) 5; appendix not identified 6; peri-appendicular fluid collection 7; thickened recto-sigmoid wall (>3 mm) 8; thickened caecal wall (>3 mm) 9; thickened small bowel wall (>3 mm) 10; peri-caecal fat stranding 11; free fluid in pelvis 12; extraluminal gas. Using these signs the CT studies were then categorized as either TOA or AA, sub-grouped as with and without abscess formation. This categorization was performed by two experienced radiologists, who reviewed the CT examinations of the entire sample without knowledge of
1031
the original CT reports or of the clinical and surgical outcome. All diagnoses were made in consensus. A TOA was diagnosed when a complex adnexal mass d a fluid-filled cavity that includes the ovary with a thickened, enhancing wall and peri-ovarian fat stranding dwas present. AA was diagnosed when a dilated thickened wall appendix with peri-caecal fat stranding and/or thickening of the caecal wall was observed. A PAA was subclassified in the presence of a thickened wall and fluid collection in the right pelvis in addition to the above AA signs. The diagnosis noted in the original radiological report, where present, was also documented. The medical files of women diagnosed with TOA were reviewed by a senior gynaecologist who was blinded to the CT interpretation. Medical files were reviewed for clinical presentation and outcome, results of laboratory examinations, diagnostic tests, such as ultrasound, and interventional procedures.
Statistical analysis The readers’ diagnoses were compared with the surgical and clinical outcomes, using the latter as the reference standard. The accuracy of the reviewed diagnoses and level of agreement by Kappa coefficients were calculated. Furthermore, the frequency of the presence of each of the 12 CT signs in the surgical and clinical TOA and AA with and without PAA were calculated. The association of each sign with the surgical and clinical diagnosis was tested using Chi-square test.
Ethics Institutional review board permission was given for the retrospective evaluation of the CT and clinical files of patients with TOA and acute or perforated appendicitis.
Results Two patients from the initial 50 TOA group and four from the initial 84 AA group had a normal CT examination with no signs of inflammation or other disease. Diagnosis in these TOA patients was made clinically and they improved after antibiotic treatment. The four patients from the AA group underwent surgery. In three, AA was not identified at surgery. In the fourth, the Table 1 Concordance of reviewers and clinical diagnosis. Reviewed diagnosis Clinical diagnosis All AA TOA
AA without PAA TOA PAA only TOA
All AA (n ¼ 80) 77 (96.3%) 3 (3.7%) AA without PAA (n ¼ 56) 53 (94.6%) 3 (5.4%) PAA only (n ¼ 24) 24 (100%) 0 (0%)
Kappa p-Value TOA (n ¼ 48) 7 (14.6%) 0.83 41 (85.4%) TOA (n ¼ 48) 7 (14.6%) 0.81 41 (85.4%) TOA (n ¼ 48) 7 (14.6%) 0.80 41 (85.4%)
<0.001
<0.001
<0.001
AA, acute appendicitis; PAA, peri-appendicular abscess; TOA, tubo-ovarian abscess.
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Table 2 Patients with incorrect or equivocal reviewer diagnosis. Patient No Age Clinical Readers diagnosis diagnosis
CT findings
1
50
TOA
PAA
2
47
TOA
PAA
3
30
TOA
PAA
4
30
TOA
Equivocal
5
29
TOA
Equivocal
6
41
TOA
Equivocal
7
34
TOA
Equivocal
8
21
AA
TOA
9
30
AA
Equivocal
10
80
AA
Equivocal
Pelvic phlegmonous mass including right ovary and bowel loop. Thickened and inflamed appendix. Pelvic abscess, involving ovary. Not “classic” TOA. Appendix not identified. Normal caecum Pelvic abscesses, involving ovary. Not “classic” TOA. Appendix not identified. Abnormal caecum. Pelvic phlegmonous mass including right ovary and bowel loop. Appendix not identified. Normal caecum. Abnormal ovaries. Not “classic” TOA. Normal appendix. Abnormal ovaries. Not “classic” TOA. Normal appendix. Slightly enlarged ovary, no fat stranding. Not “classic” TOA. Normal appendix. Enlarged ovary, thickened wall but not “classic” TOA. Normal app. Normal caecum. Normal appendix. Normal ovaries. Thickened large bowel with colitis signs. Appendix not identified. Mild peri-caecal fat stranding. Normal for age ovaries.
AA, acute appendicitis; PAA, peri-appendicular abscess; TOA, tubo-ovarian abscess.
appendix was suspected to be inflamed at surgery; however, this was not confirmed at the histopathology examination. These six patients were excluded from the study. The final group consisted of 128 patients, 48 with rightsided TOA (age 18e56 years, mean 39.3 9.8 years) and 80 with AA, including 24 with PAA (age 19e92 years, mean 53.5 19.9 years). The presence of TOA was confirmed either by ultrasound, surgery, or drainage. The original radiological reports were available for 65 patients (26 with clinical diagnosis of TOA and 37 with AA). Detailed files of 31 of the 48 patients (64%) with TOA, available in the gynaecological department, were reviewed by a senior gynaecologist. Patients in the TOA group were significantly younger than in the AA group (p < 0.01). Only eight of the 48 patients (16.7%) of the TOA group were older than 50 years, whereas 45 of the 80 patients (56.3%) of the AA group were older than 50 years (p < 0.01). The reviewers classified 118/128 cases (92%) correctly, and four (3%) incorrectly. Reviewers’ diagnosis was equivocal in six (5%) patients. The accuracy of the reviewers’ diagnosis and the Kappa measurements of agreement between reviewed and clinical diagnosis are presented in Table 1. In the TOA group (n ¼ 48 patients), reviewers were correct in 41 cases (85.4%), wrong in three (6.3%), and equivocal in 4 (8.3%). In the original radiological report
Figure 1 A 50-year-old woman with a clinical diagnosis of TOA mistakenly diagnosed as PAA. (a) A CT image showing a multilocular pelvic mass (black arrow), with a thickened enhancing wall, perilesional fat stranding (*), and a small amount of ascites (arrowhead) as well as a thickened wall appendix (white arrow). (b) The coronal reformatted CT image clearly shows the abnormal appendix.
(available for 26 patients with a clinical diagnosis of TOA), readers were correct in 18 cases (69%), wrong in three (11%) and equivocal in five (19%). Of the entire AA group (n ¼ 80 patients), reviewers correctly identified 77 cases (96.3%), erred in one case (1.3%), and were equivocal in two cases (2.5%). The three
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Table 3 Frequency of radiological signs in tubo-ovarian abscess (TOA) and acute appendicitis (AA) subgroups. CT sign
Clinical diagnosis
Abnormal ovarya Peri-ovarian fat stranding Extraluminal gas Small bowel wall thickening Recto-sigmoid wall thickening Appendix diameter 6 mm Appendix wall thickness 3 mm Appendix not identified Peri-appendiceal fluid collection Caecal wall thickening Peri-caecal fat stranding Free pelvic fluid
TOA (n ¼ 48)
AA (n ¼ 80) All (n ¼ 80)
Without PAA (n ¼ 56)
PAA only (n ¼ 24)
42 (87.5%) 28 (58.3%) 6 (12.5%) 15 (31.3%) 18 (37.5%) 1 (2%) 1 (2%) 22 (45.8%) 7 (14.6%) 8 (16.7%) 6 (12.5%) 21 (43.8%)
11 (13.8%)b 3 (3.8%)b 9 (11.3%) 20 (25%) 10 (12.5%)b 64 (80%)b 26 (32.5%)b 12 (15%)b 24 (30%)c 69 (86.2%)b 70 (87.5%)b 23 (28.8%)
6 (10.7%)b 2 (3.6%)b 0 (0%)b 9 (16.1%) 7 (12.5%)b 50 (89.3%)b 18 (32.1%)b 7 (12.5%)b 0 (0%)b 47 (83.9%)b 48 (85.7%)b 13 (23.2%)c
5 (20.8%)b 1 (4.2%)b 9 (37.5%)c 11 (45.8%) 3 (12.5%)c 14 (58.3%)b 8 (33.3%)b 5 (20.8%)c 24 (100%)b 22 (91.7%)b 22 (91.7%)b 10 (41.7%)
PAA, peri-appendicular abscess. a Thickened, enhancing ovarian wall with fluid density. b p < 0.01. c p < 0.05.
latter cases were in the AA without abscess formation group (n ¼ 56). In the PAA group (n ¼ 24), reviewers were correct in all cases (100%). In the original radiological report (available for 37 patients with a clinical diagnosis of AA), readers were correct in all cases. The CT findings in the 10 patients with an incorrect or equivocal reviewed diagnosis are presented in Table 2. Three patients with TOA were incorrectly diagnosed as having PAA (Fig 1), and one patient with AA was incorrectly diagnosed as having TOA. The values of Kappa measurement of agreement between reviewed and clinical diagnosis, 0.77e0.80,
obtained were high and significantly different from zero (Table 1). The comparison of the prevalence of each of the 12 CT signs, including the Chi-square test for the associations of each sign with the surgical and clinical diagnosis, are presented in Table 3; Fig 2 illustrates the percentage of patients showing each of the 12 CT signs in TOA and in AA (subdivided into AA without and with PAA). The most frequent findings in TOA were an abnormal ovary, peri-ovarian fat stranding, and bowel wall thickening, most often observed in the recto-sigmoid (Fig 3). The
Figure 2 Percentage of patients showing each of the 12 signs in the TOA group and in the AA with and without PAA group.
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Figure 3 A 43-year-old woman with a clinical diagnosis of TOA. The CT image shows a right-sided multilocular mass (black arrow), perilesional fat stranding (*), and a thickened wall sigmoid colon (arrowhead). The appendix is normal (white arrow).
appendix was not identified in nearly half of TOA (45.8%) cases compared to in 15% of the cases of AA. A dilated appendix was seen in 2% of TOA compared to 80% in AA patients. A thickened appendiceal wall was
Figure 4 A 55-year-old woman with a clinical diagnosis of PAA. The CT images show (a) a pelvic abscess containing air bubbles (black arrow) with peri-lesional fat stranding (*) and (b), which is proximal to (a), shows a thickened wall appendix (white arrow).
observed in 2% of TOA. In the AA group, the appendiceal wall could be measured in 37 patients only; a thickened appendiceal wall was seen in 26 patients (70%). In the other 43 the wall was not clearly identified. Thickening of the caecal wall and peri-caecal fat stranding were statistically less frequent (p < 0.01) in TOA patients (16.7% and 12.5%, respectively) than in the AA group (86.2% and 87.5%, respectively). The most frequent findings in the AA group were a distended appendix with a thickened wall. The ovary and periovarian fat were normal in most patients with appendicitis. Involvement of the small bowel was similar to that seen in TOA; recto-sigmoid wall thickening was, however, less frequent in AA compared to TOA. Extraluminal intralesional gas was much more frequent in patients with PAA (Fig 4) compared to TOA patients.
Discussion CT has an important role in the diagnosis of TOA, exhibiting complex fluid-attenuation collections with thickened and irregular walls.7,8 Yet, differentiation of rightsided TOA from AA, particularly when complicated by abscess formation, continues to be problematic, especially in young women.2,3 Patients in the TOA group were significantly younger than patients in the AA group. The average age reported for patients with TOA was 40e46 years,1,9 whereas AA can occur in almost every age.10,11 To the authors’ knowledge, the present study is the first to compare the CT findings of right-sided TOA and AA and PAA. In 118 out of 128 women, several non-specific CT signs appeared to correctly differentiate the two entities, in addition to the specific CT appearance of the ovary and the appendix. Peri-ovarian fat stranding and thickening of the rectosigmoid wall were CT features favouring the diagnosis of TOA, as these were rare in the cases of AA. These CT signs appeared with statistically significantly higher frequency in TOA compared to AA, without and with a PAA. These features probably represent reactivity of the neighbouring organs.1,12,13 A thickened caecal wall and peri-caecal fat stranding were signs favouring the diagnosis of AA and PAA. These CT signs are well established as typical for appendiceal disease.3,4 However, a dilated appendix with a thickened wall, a thickened caecal wall, and peri-caecal fat stranding were also found in patients with TOA. These finding were present less frequently in TOA compared to AA patients. The occurrence of these signs in TOA is less well documented in the literature. Bennett et al.2 stated that in patients with TOA, the inflammatory process may extend to involve the appendix or colon and greater omentum. Kim et al.3 recently described diffuse or focal wall thickening of the appendix in 10 women with pelvic inflammatory disease and called it “appendiceal serositis”. Radiologists should be aware of such findings as they may mimic appendicitis in women suffering from pelvic inflammatory disease, as in one of the present patients and in the 10 patients reported by Kim et al.3
I. Eshed et al. / Clinical Radiology 66 (2011) 1030e1035
Extra-luminal gas bubbles were less often observed in TOA compared to PAA; however, this finding was not statistically significant. Indeed it was already reported that extraluminal gas is less frequent in TOA2 compared to PAA.14 Thus, the presence of air bubbles favours the diagnosis of a PAA. Ascites was seen in 43.8% of TOA patients; ascites is commonly found with pelvic inflammatory disease.2,3,12 However, it was seen with a similar frequency (41.7%) in the PAA group, and was not helpful in the differentiation between the two conditions. A non-visualized appendix at CT, in the absence of secondary inflammatory changes, in patients with right lower-quadrant pain has been reported as a reliable sign to exclude appendicitis.15,16 However, in the present study, a non-visualized appendix did not aid the differentiation of TOA from AA. This may have resulted from the relatively small cohort of TOA patients. In the present study, the diagnosis by two experienced radiologists had a significantly greater accuracy for the AA group than for the TOA group. The same tendency was seen in the readings of the original radiological reports. TOA was missed in seven patients. It was mistakenly assumed that the inability to visualize the appendix in the presence of a right-sided pelvic abscess indicated PAA. This assumption proved incorrect as the appendix was not seen in nearly half of the TOA patients compared with only 20.8% of the PAA patients. Therefore a non-visualized appendix is not a helpful sign in the differentiation of TOA from appendicitis, especially when the latter is associated with a PAA. Another reason for the incorrect diagnosis of TOA was the assumption that in TOA the surrounding tissues are usually inflamed. However, as these features may appear only in the later stages of TOA, this assumption led to an equivocal diagnosis in four cases. The same tendency for equivocal diagnosis was seen in the original radiological reports probably for the same reason. AA was missed in three patients; in one the ovary was enlarged and the appendix looked normal. In the other two instances the significance of thickening of the large bowel wall was underestimated in one, and the mild peri-caecal fat stranding was underestimated in the other. The limitations of the study include the retrospective nature of the study and the fact that nearly a third of the patients with TOA were only clinically confirmed and lacked pathological confirmation. A prospective evaluation of a larger cohort, specifically of female patients with rightsided abscess with a surgically proven diagnosis would strengthen the statistical analysis. Also, as reviewers had to choose between two possible pathological diagnoses (TOA and AA), the overall diagnostic accuracy might be skewed. However, the same tendency of results was seen in the
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original radiological reports in which the diagnosis was not restricted. In conclusion, in the presence of a right lower-quadrant inflammatory mass in women, several secondary CT findings were helpful in the differentiation between TOA and AA. Peri-ovarian fat stranding, thickened wall of the rectosigmoid, as well as a normal-appearing caecum, in young patients favoured the diagnosis of TOA. Extraluminal air favoured the diagnosis of a PAA abscess rather than TOA. A non-visualized appendix did not contribute to the differentiation between TOA and PAA. Differentiating some cases of TOA from acute or perforated appendicitis will probably remain a diagnostic challenge even for the experienced radiologist. Further studies with pathological correlation are needed to evaluate the changes in the right ovary in the presence of appendicitis and especially in PAA.
References 1. Hiller N, Sella T, Lev-Sagi A, et al. Computed tomographic features of tuboovarian abscess. J Reprod Med 2005;50:203e8. 2. Bennett GL, Slywotzky CM, Giovanniello G. Gynaecologic causes of acute pelvic pain: spectrum of CT findings. RadioGraphics 2002;22:785e801. 3. Kim MY, Lee YM, Suh CH, et al. Computed tomographic features of appendiceal serositis in pelvic inflammatory disease: comparison with pathological findings. J Comp Assist Tomogr 2007;31:104e8. 4. Ellis JH, Francis IR, Rhodes M, et al. CT findings in tuboovarian abscess. J Comp Assist Tomogr 1991;15:589e92. 5. Rao PM, Wittenberg J, McDowell RK, et al. Appendicitis: use of arrowhead sign for diagnosis at CT. Radiology 1997;202:363e6. 6. Rybkin AV, Thoeni RF. Current concepts in imaging of appendicitis. Radiol Clinics North Am 2007;45:411e22. vii. 7. Potter AW, Chandrasekhar CA. US and CT evaluation of acute pelvic pain of gynecologic origin in nonpregnant premenopausal patients. RadioGraphics 2008;28:1645e59. 8. Sam JW, Jacobs JE, Birnbaum BA. Spectrum of CT findings in acute pyogenic pelvic inflammatory disease. RadioGraphics 2002;22:1327e34. 9. Jeong WK, Kim Y, Song SY. Tubo-ovarian abscess: CT and pathological correlation. Clin Imaging 2007;31:414e8. 10. Unlu C, de Castro SM, Tuynman JB, et al. Evaluating routine diagnostic imaging in acute appendicitis. Int J Surg 2009;7:451e5. 11. van Randen A, Bipat S, Zwinderman AH, et al. Acute appendicitis: metaanalysis of diagnostic performance of CT and graded compression US related to prevalence of disease. Radiology 2008;249:97e106. 12. Phillips JC. A spectrum of radiologic abnormalities due to tubo-ovarian abscess. Radiology 1974;110:307e11. 13. Wilbur AC, Aizenstein RI, Napp TE. CT findings in tuboovarian abscess. AJR Am J Roentenol 1992;158:575e9. 14. Horrow MM, White DS, Horrow JC. Differentiation of perforated from nonperforated appendicitis at CT. Radiology 2003;227:46e51. 15. Ganguli S, Raptopoulos V, Komlos F, et al. Right lower quadrant pain: value of the nonvisualized appendix in patients at multidetector CT. Radiology 2006;241:175e80. 16. Nikolaidis P, Hwang CM, Miller FH, et al. The nonvisualized appendix: incidence of acute appendicitis when secondary inflammatory changes are absent. AJR Am J Roentenol 2004;183:889e92.