Comparison of Ultrasound and CT Findings of Pelvic Masses with Histopathology: A Cross-sectional Study

1. Assistant Professor, Department of Radiology, Gautam Buddha Chikitsa Mahavidyalaya, Subharti Medical College, Dehradun, Uttarakhand, India. 2. Professor and Head, Department of Radiology, Government Medical College, Patiala, Punjab, India. 3. Associate Professor, Department of Obstetrics and Gynaecology, Government Medical College, Patiala, Punjab, India. 4. Senior Resident, Department of Obstetrics and Gynaecology, Government Medical College, Patiala, Punjab, India.

Abstract

Introduction: Benign and malignant pelvic masses can occur in different age groups, primary diagnosis and choosing the appropriate surgical procedure is very important. Ultrasound (USG) is the diagnostic test of choice in evaluating pelvic masses, while Computed Tomography (CT) scan is most helpful as a second-line study, for in-depth evaluation of the abdomen and pelvis.

Aim: To compare the findings of ultrasound and CT scans of pelvic masses with definitive histopathological or laboratory findings.

Materials and Methods: A cross-sectional study was conducted at Government Medical College and Rajindra Hospital, Patiala, Punjab, India, from December 2014 to September 2015. Sixty patients from Outpatient and Inpatient Department, with clinical suspicion of pelvic pathology, were evaluated sonographically and then by CT scan. Ultrasound characterisation of mass as high or low risk was done based on septae and solid part echogenicity. CT findings used to diagnose malignancy were cystic solid mass, necrosis in a solid lesion, cystic lesion with thick, irregular walls or septa, and/or papillary projections. The presence of ascites, lymphadenopathy, omental cake, peritoneal deposits, mesenteric deposits was noted to diagnose metastasis. Data was analysed using Statistical Package for Social Sciences (SPSS) version 16.0. A p-value was calculated using Chi-square test. For finding, the level of agreement between USG/CT scan and histopathology, Kappa statistic was applied.

Results: Ultrasound had sensitivity of 73.7%, specificity of 80.3%, Positive Predictive Value (PPV) of 53.8% and Negative Predictive Value (NPV) of 90.7%. Computed tomography scan had a sensitivity of 78%, specificity of 95.08%, PPV of 83.3%, and NPV of 93.5%. Kappa statistics showed moderate level of agreement between USG and histopathological findings (k=0.47,p-value=0.017) and good level of agreement between CT scan and histopathological findings (k=0.68, p-value=0.001).

Conclusion: Ultrasound with its good sensitivity can be used as an effective screening modality for pelvic masses. Computed tomography scan has better specificity than USG and should be used as a confirmatory investigation.

Benign, Computed tomography, Malignant, Mass, Pathology, Radiology

It has always been difficult to venture into the complex anatomical region of the pelvis. Hence, pelvic masses are difficult to evaluate. As benign and malignant pelvic masses can occur in different age groups, primary diagnosis and choosing the appropriate surgical procedure is very important. Clinically, these masses are detected in the advanced stage when they become large enough to cause pressure symptoms and symptoms like pain in the abdomen, and bleeding per vaginum or per rectum (1).

Ultrasound is the diagnostic test of choice in evaluating pelvic masses and may diagnose >90% of the pelvic masses. In the study conducted by Raju P et al., the overall sensitivity of Ultrasound (USG) was 79.2% and specificity was 85.5% (2). In the study conducted by Karthikeyan B et al., the sensitivity of USG was 89%, and specificity was 84% (3). In the study conducted by Liu Y et al., the sensitivity, specificity, and accuracy of ultrasound were determined to be 52.8%, 86.7%, and 68.75%, respectively (4). Beyond 7 cm, the diagnostic performance of ultrasound decreases (5). Transabdominal ultrasound gives an overall assessment of organ size and anatomy, whereas transvaginal ultrasound with its higher image resolution gives more detailed information about pelvic structures and masses (6).

Computed Tomography (CT) scan is not recommended for the initial evaluation of pelvic masses because ultrasound is less expensive and results in no radiation exposure. In the study conducted by Raju P et al., the sensitivity of CT scan was 97.6%, specificity 91.4% (2). In the study conducted by Karthikeyan B et al., CT was found to have 98% sensitivity, 91% specificity, and an accuracy of 96% in the differentiation of benign and malignant ovarian masses (3). In the study conducted by Liu Y et al., the sensitivity, specificity, and accuracy of CT scan were determined to be 80.3%, 90.3%, and 85%, respectively (4).The novelty of the present study is that, various types of pelvic masses have been studied, whereas in studies by Raju P et al.,(2) and Karthikeyan B et al., (3), only ovarian masses were studied. Computed tomography is helpful as a second line of investigation, for in-depth evaluation of the abdomen and pelvis when malignancy is suspected (7). Reimaging of mass with USG can be done in case of abnormal CT findings for better clarification of vascularity of mass and indications uniquely suited to USG like pregnancy (8).

The present study was conducted with objectives:

• Detection of pelvic mass suspected on clinical examination using USG and CT scan and to find its site of origin.
• To classify the detected pelvic masses as benign or malignant.
• To compare the findings of USG and CT scan with definitive histopathological or laboratory findings.

Material and Methods

A cross-sectional study was conducted at Government Medical College and Rajindra Hospital, Patiala, Punjab, India, from December 2014 to September 2015. Permission from the Institution’s Ethics Committee was taken {Trg 9(310)2022/17861}. Informed written consent was obtained from all the selected patients. A total of 60 patients with clinically suspected pelvic masses (age 2-81 years, 57 females and three males) who visited the hospital during the stated duration of the study form the sample population and they were evaluated sonographically first and then by CT scan.

Inclusion criteria: Patients with clinically suspected pelvic mass, and patients with sonographically diagnosed pelvic mass were included in the study.

Exclusion criteria: All pregnant female and patients with deranged renal function tests were excluded from the study.

A total number of masses was 80, as some of the patients had more than one mass. History, clinical findings, and biochemical investigations including routine investigations (complete blood count, renal function tests, liver function tests, urine complete examination) and tumour markers, relevant to the suspected tumour were recorded in performa.

Study Procedure

Ultrasound: USG was performed with Philips envisor or Philips US unit HD3 and Wipro GE Logic 200 alpha machines. Ultrasound scanning was done in supine position, with urinary bladder physiologically distended to provide an acoustic window in pelvis for Transabdominal Sonography (TAS). Transvaginal sonography and Transrectal ultrasound were performed on an empty bladder. Evaluation was limited to TAS in virgins, and for large masses which exceed the maximum field of view of the transvaginal transducer. No specific preparation was given prior to the examination, only unco-operative patients (mostly paediatric age group) were studied after mild sedation. Ultrasound characterisation of mass as high or low risk was done based on septae and solid part echogenicity.

Computed tomography: CT scan was performed on Siemenssomtam Emotion 6 slice third generation spiral CT. The patient was scanned from base of the lungs to symphysis pubis in supine position after intravenous injection of non ionic contrast (like ioversol) in portovenous phase with a scanning delay of 60-90 seconds. Oral or rectal contrast was given, if the patient’s clinical condition permitted. Image slices of 8 mm thickness were obtained followed by reconstruction in sagittal and coronal sections. CT findings used to diagnose malignancy were, cystic solid mass, necrosis in a solid lesion, cystic lesion with thick, irregular walls or septa, and/or papillary projections. CT abdomen-pelvis protocol was used. The presence of ascites, lymphadenopathy, omental cake, peritoneal deposits, and mesenteric deposits was noted to diagnose metastasis.

Histopathological examination: The histopathological examination was the gold standard for diagnosis. Biopsy material included resected specimen or biopsy from the lesion. All the specimens were fixed in 10% formalin, sectioned, and subjected to macroscopic and microscopic examination. Thin sections were prepared from the area of growth, adjoining areas and any separate tissue received like omentum and lymph nodes. Tissue sections were stained with routine Haematoxylin and Eosin (H&E) stain. The slides were then subjected to the histopathological examination, under both low power (100X) and high power (400X), serial sections were examined wherever required.

The study outcome was considered in the following ways:

• True positive: A mass with ultrasound findings or CT findings of malignancy getting confirmed on histopathology.
• False positive: A mass with ultrasound findings or CT scan diagnosis of malignancy turned out to be benign in nature on histopathology.
• True negative: A mass which was described as benign on USG or CT scan, proved to be benign on histopathology.
• False negative: A mass which was diagnosed as benign on USG or CT scan was diagnosed as malignant on histopathology.

Statistical analysis

Data was analysed using Statistical Package for Social Sciences (SPSS) version 16.0 software. A p-value was calculated using Chi-square test and a p-value <0.05 was considered statistically significant. Sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV) were calculated. For finding the level of agreement between USG/CT scan and histopathology, the Kappa statistic was applied.

Results

Both USG and CT diagnosed 30 cases of uterine masses, one pelvic abscess and two cases of carcinoma bladder. Adnexal masses diagnosed on ultrasound were 44 and on CT scan were 46. On USG, three masses remained indeterminate about their origin (Table/Fig 1). On CT scan, two out of these three indeterminate masses, were diagnosed as adnexal masses and one was diagnosed as sacrococcygeal teratoma on CT. Indeterminate masses are the ones that cannot be definitively characterised as probably benign or possibly malignant, and they are considered indeterminate at USG. These sonographically indeterminate masses have avascular internal components, such as internal irregular thick septations or solid-appearing nodules without blood flow, or they are otherwise benign-appearing entities, such as haemorrhagic cyst, endometrioma, or mature teratoma, that cannot be entirely assessed with USG due to their large size and/or atypical features.

Final histopathological characterisation of the masses revealed that out of total 80 masses, 61 (76.3%) masses were benign in nature while 19 (23.7%) masses were malignant.

The number of females presenting with pelvic mass was 57 (95%) while that of males was 3 (5%), total patients were 60. Most of the subjects with benign pelvic masses (56.1%) were seen in age group of 20-39 years. Subjects with malignant pelvic masses (52.6%) were more common in age group of 60 and above (Table/Fig 2). In the age group <10 years, there were total three children and all of them had a benign mass. In the age group between 10-19 years, there were two adolescents and both of them also had a benign mass.

Amongst the 46 adnexal masses, a total of 19 masses (including both benign and malignant) were found to have cystic consistency both on USG and CT scan (Table/Fig 3).

On CT scan, metastatic deposits were absent in all the benign masses but were present among 11 (58%) of malignant masses (n=19) which was statistically significant (p-value <0.05). Presence of ascites, lymphadenopathy, omental cake, peritoneal deposits, mesenteric deposits was noted to diagnose metastasis. Ascites and lymphadenopathy were seen in few subject with malignant masses, as described in (Table/Fig 4). However, omental caking, peritoneal deposits and mesenteric deposits were not found in any of the subjects with malignant masses.

On USG, metastasis were detected only in two cases of malignant group. Adnexal masses were unilateral in 38 (82.6%) cases and bilateral in 8 (17.4%) cases. The CT scan had higher sensitivity (78%),specificity (95.08%), positive predictive value (83.3%) and negative predictive value (93.5%) as compared to ultrasound (Table/Fig 5). Patient presented with discharge per vaginum and loss of weight. Both USG and CT scan diagnosed it accurately, as a case of carcinoma cervix. Diagnosis was confirmed on histopathology [Table/Fig-(6),(7). A four and half year old female child, presented with pelvic pain and fever. It was diagnosed as pelvic abscess on both USG and CT scan. However, organ of origin could not be identified. It proved to be an abscess on aspiration [Table/Fig-(8),(9).

Patient presented with abdominal distension and pelvic mass. USG described it as cystic mass with presence of a small mural nodule and provisionally diagnosed it as a carcinoma of ovary. CT scan diagnosed it correctly based on no enhancement of the mural nodule. On histopathology, it was confirmed as serouscystadenoma [Table/Fig-(10),(11). A 23-year-old female presented with menstrual disturbances and dysmenorrhoea. USG and CT diagnosed it as serous cystadenocarcinoma, however it was confirmed as serous cystadenoma on histopathology [Table/Fig-(12),(13).

Discussion

In present study, maximum number of cases i.e. 36 (45%) were in 20-39 age group. In the current study, age range was 2-81 years, the mean age was 40.±16.7 years. Similarly, the age range in study by Firoozbadi RD et al., and Alcazar JL et al., were 17-75 and 17-79,respectively (9),(10). The mean age in studies by Gatreh-Samani F et al., and Hafeez S et al., Mubarak F et al., were 48.63 years, 40.95 yrs and 60 years, respectively (11),(12),(13). Most of the benign pelvic masses (52.6%) were seen in the age group of 20-39 years while malignant pelvic masses (47.4%) were more common in the age group of
60 and above. Bren JL and Maxon WS, reported that 35% of all ovarian neoplasms in childhood and adolescent were malignant, but this was not the case in current study, because there was a wide range of patients (14). In the present study, 95% cases were females while 5% while were males. According to Moore RG and Bast RC, approximately 20% of women will develop a pelvic mass at some time in their lives (15).

In the present study, 32 patients (53.3%) presented with pain in abdomen and pelvis, 31 (51.7%) cases had menstrual disturbance, 17 cases (28.3%) presented with complaint of mass inabdomen or abdominal distension, 10 (16.7%) had urinary symptoms, 17 (28.4%) had loss of weight and appetite. In the study conducted by Munir SS et al., 68 (63.6%) patients had pain, 25 (4%) presented with self-diagnosed tumour, 11 (0.9%) had dyspepsia, 8 (3.71%) had abdominal distension (16). Givens et al., stated that patients with an adnexal mass, may present with varying symptoms (17). Abdominal fullness and pressure, back pain, and lack of energy may be prominent symptoms as studied by Stenchever MA, (18), Goff BA et al., (19), Friedman GD et al., (20). These vague symptoms are present for months in up to 93 % of persons with ovarian cancer Olson SH et al., (21).

In the present study, on histopathological findings; 61 (76.3%) and 19 (23.7%) masses were benign and malignant, respectively. Stein SM et al., reported similar findings with 123 (71.8%) benign masses and 46 (28.2%) malignant masses (22). Rehn M et al., found 259 masses to be benign while 51 cases were malignant (23). Luxman D et al., reported 72% subjects had benign tumours and 28% had malignant tumours (24). Firoozabadi RD et al., found 44% cases to be benign while 55.4% masses were malignant (9). In the current study, 82.6% of the subjects had unilateral masses and 17.4% had bilateral masses. Similarly, in a study by Prabhakar BR and Maingi K, 90.89% subjects had unilateral mass and 9.11% had bilateral masses (25).

Out of total 80 cases of pelvic masses, majority 46 (57.5%) were of adnexal origin on CT and 36 cases were benign according to CT findings. USG detected 44 cases of adnexal masses and characterised 22 of them as benign. Similarly, Brown D, concluded that most pelvic masses arise from ovarian tissue and most intraovarian masses are benign, especially in premenopausal women (26).

Adnexal masses: In present study, the difference among the benign and malignant group regarding consistency of masses were statistically significant on CT but not on USG. The findings suggest that USG was unable to differentiate between a benign and malignant mass on the basis of consistency which got revealed on CT scan. The present study findings are supported by work of Wani S et al., who stated that it is possible to suspect malignancy on the basis of ultrasonic image but a definite diagnosis cannot always be made (27). Granberg S et al., concluded that complexity of an ovarian cyst can be a predictor of malignancy (6). Abbas AM et al., found that multilocular-solid mass was the most common pattern of ovarian malignancy (30.4%) followed by solid mass (28.3%) (28).

In the current study, 42.1% malignant adnexal masses had thick septae and 57.9% showed thin septae or no septae on USG. Thin septae or no septae were seen in 84.8% of the benign adnexal masses while 15.2% showed thick septae. Abbas AM et al., concluded that the malignant cystic masses often had papillary projections (42.4% vs 4.3%, p-value <0.001) and thick septae (68% vs 6.3%, p-value <0.001) than benign masses (28). However, Kinkel K et al., concluded that both transvaginal ultrasound and transvaginal ultrasonography, have low specificity for detecting malignancy, owning to overlap in the imaging appearances of benign, borderline and malignant diseases (29).

Ascites is an indirect indicator of malignancy and ascites occurs due to peritoneal spread of tumour, studied by Brown DL et al., (30). In study conducted by Timmerman D et al., it was reported that there was an increased risk of malignancy, if fluid in cul de sac measures more than 15 mm in anteroposterior dimension on ultrasound (31). In the current study, ascites and lymphadenopathy were more commonly associated with malignant masses compared to benign masses and this difference was significantly (p-value <0.05) detected by USG as well as CT scan.

In the present study, sensitivity of ultrasound in predicting malignancy in pelvic masses was 73.7%. However, sensitivity and specificity were higher in studies conducted by Alcazar JL et al., (10) Timmerman D et al., (31) Buy JN et al., (35) and Jacobs et al., (36) ascompared to the current study (Table/Fig 14) (10),(11),(13),(16),(29),(31),(32),(33),(34),(35),(36),(37),(38),(39),(40),(41),(42),(43).

A meta-analysis conducted by Kinkel K et al., (29) described that CT showed sensitivity and specificity of 81% and 87%, respectively when used for indeterminate masses seen on USG. For differentiating benign and malignant ovarian masses, CT had a higher sensitivity and lower specificity in studies conducted by Gatreh-Samani F et al., (11) Mubarak F et al., (13), Tsili AC et al., (41), Zhang J et al., (42), as compared to our study, probably due to higher number of participants in these studies; however Liu Y et al., (43) reported lower sensitivity and higher specificity than the current study (Table/Fig 14).

The strength of this study is that various types of pelvic masses have been studied, unlike many other studies where only ovarian masses have been studied. Also in the current study, wide range of age groups have been included. Future recommendations of study include, studying sensitivity and specificity of imaging techniques (ultrasound and CT scan) in diagnosing pelvic pathologies in a larger population. Role of other imaging techniques like magnetic resonance imaging and positron emission tomography scan in diagnosing aetiologies of pelvic masses should be studied.

Limitation(s)

Limitation of this study was small sample size. As study was conducted over a predecided period of time, so only the number of patients who reported to hospital during that time period could be included in the study. Wall thickness was not studied on ultrasound.

Conclusion

Both CT and USG are sensitive and specific to categorise pelvic masses into benign and malignant groups. However, interpreting an ultrasound is much more subjective than interpreting a CT scan. USG with its good sensitivity can be used as an effective screening modality for pelvic masses. CT scan has better specificity than USG and should be used as a confirmatory investigation.

DOI and Others

DOI: 10.7860/JCDR/2022/56592.17140

Date of Submission: Apr 03, 2022
Date of Peer Review: May 10, 2022
Date of Acceptance: Aug 26, 2022
Date of Publishing: Nov 01, 2022

Author declaration:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

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