Qualitative and quantitative differences in the CT findings between the two groups were statistically analyzed with Fisher exact and Student t-test using a software program (SAS Institute, Cary, NC). Fisher exact test was used to determine statistical differences in omental change, mesenteric change, parietal peritoneal change, lymph node enlargement, ascites, and ovarian capsular change. A Student t-test was used to determine differences in ovarian parenchymal attenuation. A P value of less than 0.05 was considered statistically significant.
Table 1 presents the estimated grading scores for each of the CT features in peritoneal tuberculosis and peritoneal carcinomatosis groups, respectively.
Omental abnormalities were noted in 14 patients (77.8%) with female tuberculous peritonitis group and in 15 patients (88.2%) with peritoneal carcinomatosis group. There was no significant difference between the two groups regarding the severity of the omental changes (P = 0.658).
Parietal peritoneal abnormalities were noted in 5 patients (27.8%) with female tuberculous peritonitis group and in 6 patients (35.3%) with peritoneal carcinomatosis group. There was no significant difference between the two groups regarding the severity of parietal peritoneal changes (P = 0.725).
Mesenteric abnormalities were noted in 13 patients (72.2%) with female tuberculous peritonitis group and in 8 patients (47.1%) with peritoneal carcinomatosis group. There was no significant difference between the two groups regarding the severity of mesenteric changes (P = 0.176). The mesenteric changes noted on CT were thickenings of the mesenteric leaflets with visceral peritoneal thickenings, heterogeneous smudged or soft tissue infiltrative lesions, or micronodular or macronodular lesions.
Ovarian capsular changes were noted in 1 patient (5.6%) with tuberculous peritonitis group and in 13 patients (76.5%) with peritoneal carcinomatosis group, and this difference was significant between the groups (P < 0.001).
Ovarian parenchymal attenuation ranged from 33 to 89 HU (mean = 57) in patients with female tuberculous peritonitis group and from 39 to 115 HU (mean = 76) in patients with peritoneal carcinomatosis group. Ovarian parenchymal attenuation in tuberculous peritonitis group was significantly lower in peritoneal carcinomatosis group (P = 0.002) (Table 2).
Abdominopelvic CT is often the initial imaging examination performed in patients with a wide variety of clinical symptoms. CT substantially aids in the identification of peritoneal disease. Proper recognition of the spectrum of CT findings of peritoneal disease allows identifications of disease extending into various sites of the peritoneum. The radiologist’s precise localization of all affected sites and the accurate description of the disease severity provide important guidance to clinicians for treatment.
Diseases of the peritoneum are common, and given the considerable overlap in their imaging appearances and the resultant potential for misinterpretation, they can present a diagnostic challenge. The dissemination of a primary or secondary peritoneal malignancy may result in a condition known as peritoneal carcinomatosis. The imaging manifestations of this condition may resemble those seen in the presence of various benign conditions such as peritoneal thickening due to peritoneal tuberculosis, active Crohn’s disease, diverticulitis, appendicitis, omental infraction, and severe pancreatitis, making differential diagnosis difficult. Accurate differentiation between these conditions is of crucial importance for selecting the most appropriate method of treatment.13
The abdomen is the most common focus of extrapulmonary tuberculosis. Peritonitis is the most common clinical manifestation of abdominal tuberculosis, affecting one-third of all patients.14 The incidence of peritoneal tuberculosis has declined, but still this disease remains a persistent problem in endemic areas or in immunocompromised patients.10 Peritoneal tuberculosis is thought to originate primarily from hematogenous spread; however, it may be secondary to a ruptured lymph node or gastrointestinal deposit or to fallopian tube involvement.14 The CT findings of peritoneal tuberculosis with varying degrees of omental and mesenteric involvements, ascites, and peritoneal thickening are nonspecific. If only diffuse infiltrations of the peritoneum, omentum, or mesentery are observed on CT, distinguishing between peritoneal tuberculosis and peritoneal carcinomatosis just with imaging findings related to peritoneal abnormalities is difficult or impossible because of the overlap of the imaging findings. Therefore, identification of the presence or absence of primary or secondary malignancy is crucial to determine the final diagnosis about the any peritoneal disease on CT.
There have been many reports dealing with peritoneal tuberculosis mimicking peritoneal carcinomatosis or advanced ovarian cancer. The presence of ascites and high serum level of CA-125 do not necessarily indicate that the clinical picture is malignant in reproductive women. CA-125 has a limited diagnostic value. The serum CA-125 level is found to be elevated in up to 82% of women with late-stage epithelial ovarian cancer. However, it may also be elevated in several benign pelvic pathologies such as pelvic inflammatory disease, uterine fibroids, endometriosis, and tuberculous peritonitis.11,12,15 The possibility of peritoneal tuberculosis should be considered in the differential diagnosis of patients with ascites and high serum CA-125 level. In one study, the sensitivity of AFB culture from ascites was only 12.8%.15
The CT features of female tuberculous peritonitis and peritoneal carcinomatosis are considerably similar in endemic areas, making differential diagnosis difficult. It is impossible to correctly differentiate these two diseases using clinical features, and hematologic as well as radiologic examinations without surgicopathological intervention. The majority of cases with peritoneal tuberculosis can be diagnosed by laparoscopic exploration with the use of frozen sections in conjunction with clinical features.16
Ha et al noted that the prevalence of macronodules in the mesentery was uncommon in peritoneal carcinomatosis.10 The common occurrence of mesenteric micro- or macronodules in tuberculous peritonitis appears to be because tuberculous peritonitis develops from the rupture of mesenteric lymph nodes seeded by the hematogenous or lymphatic routes from the primary lesion sites or by direct spread from the serosa by continuity with adjacent glands or structures. In our study, 50% of cases with peritoneal metastasis with normal-sized ovarian cancer revealed macronodules in mesentery, and there was no statistically significant difference in the prevalence of macronodules between the two groups. This result may indicate that the mechanism of peritoneal metastasis in any case of ovarian cancer would be direct spread through the tumor capsule of the ovary. Therefore, the prevalence of omental and parietal peritoneal abnormalities as well as mesenteric changes would not be significantly different between the groups due to their similar possible mechanism of disease development.
We have also focused on the ovarian morphology itself in the CT image analysis for differentiation between female peritoneal tuberculosis and peritoneal carcinomatosis with normal-sized ovarian cancer. There have been many previous reports dealing with peritoneal tuberculosis mimicking ovarian cancer. However, relatively few studies have presented the available CT images,2,12,17–19 and only one case report described the normal-sized both ovarian complex lesions with extensive omental and peritoneal stranding on CT scan.2
The definition of a normal-sized ovary would be difficult to determine because the normal ovary may have different shapes or sizes due to the presence or absence of ovulation-associated cysts. As a control group, we evaluated the size and attenuation of the ovaries according to the each decade of age composed of 20 women who have checked MDCT because of any purpose about other body parts. The mean largest size of normal ovaries without cysts was 3.2 cm in the third decade, 3.5 cm in the fourth, 3.2 cm in the fifth, 2.8 cm in the sixth, 2.1 cm in the seventh, and 2.1 cm in the eighth. Therefore, we considered the normal-sized ovary in the absence of cysts to be approximately 4 cm in length. The mean attenuation of the intact ovarian parenchyma in the absence of cysts was mean 55.5 HU in the third decade, 54.1 HU in the fourth, 57.3 HU in the fifth, 58.1 HU in the sixth, 61 HU in the seventh, and 63.3 HU in the eighth. The parenchymal attenuation tended to increase progressively, probably owing to the loss of follicles and stromal tissue, in addition to parenchymal atrophy.
The ovarian morphology may differ according to a patient’s age, menopause state, the menstrual cycle, and the presence or absence of follicles or cysts. We expected that the morphology of the ovarian capsule and the parenchymal attenuation would be most important in image analysis for significant differentiation between normal and abnormal ovaries even though various morphologic differences according to the various conditions may be present. Ovarian capsular changes were anticipated in both peritoneal tuberculosis and peritoneal carcinomatosis. However, our study revealed that the more significant ovarian capsular changes occurred in normal-sized ovarian cancer patients with peritoneal carcinomatosis than in female peritoneal tuberculosis patients. The ovarian parenchymal attenuation (mean 58 HU) in the control group was significantly lower than in peritoneal carcinomatosis group with normal-sized ovarian cancer (mean 76 HU) (P = 0.002). The ovarian parenchymal attenuation (mean 56 HU) in the female peritoneal tuberculosis group was significantly lower than in peritoneal carcinomatosis group with normal-sized ovarian cancer (mean 76 HU) (P = 0.002). The enhanced increased parenchymal attenuation appears to be an important CT feature in normal-sized ovarian cancer.
Among our study cases with peritoneal carcinomatosis with normal-sized ovarian cancer, the pathologic diagnosis was 15 serous papillary cystadenocarcinomas and 2 poorly differentiated adenocarcinomas. Serous papillary cystadenocarcinoma is known to account for the largest proportion of malignant ovarian tumors, representing 60 to 80% of all malignant epithelial ovarian tumors. Various macroscopic findings of mixed solid and cystic components are known CT features.20 However, there have been no reports dealing with minor CT features in normal-sized ovarian carcinoma such as capsular changes or parenchymal attenuation. We believe that normal-sized ovarian malignancy is a real CT feature of serous papillary cystadenocarcinomas of the ovary.
Our study has several limitations. First, the possibility of a selection bias should be considered because this study was a retrospective study. Our cases with female peritoneal tuberculosis did not have advanced peritoneal thickenings conglomerating or enlarging the adnexa. We believe that severe peritoneal thickenings encasing a normal-sized ovary could prevent the correct ovarian capsular analysis. We excluded cases with any size of ovarian cancer inseparable from margin of adjacent peritoneal thickening in this study. Second, less-experienced radiologists would require quite some learning time to understand the capsular change and parenchymal attenuation of the normal-sized ovary. Third, because the images were analyzed retrospectively by two experienced radiologists with consensus, we did not assess the interobserver variability. Fourth, conventional CT would be of limited use for the correct analysis of the detail of the capsular and parenchymal abnormalities because of its lower anatomical resolution and internal parenchyma conspicuity. Fifth, we did not consider the variation of the normal ovarian size or CT attenuation according to the decades of patient’s ages.
In conclusion, we presented various CT features for the differential diagnosis between female peritoneal tuberculosis and peritoneal carcinomatosis with normal-sized ovarian cancer. To our knowledge, no similar studies have been previously reported. In this study, there were high percentages of significant positive findings of omental and mesenteric abnormalities in each disease group, with no significant differences between two groups. There were significantly high percentages of significant ovarian capsular change and higher ovarian parenchymal attenuation only in the peritoneal carcinomatosis group. We consider the value of the significant ovarian capsular change and higher ovarian parenchymal attenuation to be useful for differentiation between female peritoneal tuberculosis and peritoneal carcinomatosis with normal-sized ovarian cancer.
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Keywords:Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
peritoneal tuberculosis; peritoneal carcinomatosis from normal-sized ovarian cancer; CT differentiation