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Diagnosis of Retroperitoneal Tumours using Computed Tomography- A Cross-sectional Study |
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Umamaheshwari K Basavaraju, Narasipur Lingaiah Rajendrakumar, P Sanjay, Nanjaraj Chakenalli Puttaraj, Prathibha PShivadas, Mahesh Seetharam, Rashmi K Nagaraju, Supraja Moorthy 1. Associate Professor, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 2. Professor and Head, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 3. Assistant Professor, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 4. Professor and Dean & Director, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 5. Senior Resident, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 6. Senior Resident, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 7. Resident, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. 8. Resident, Department of Radiology, Mysore Medical College and Research Institute, Mysuru, Karnataka, India. |
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Correspondence Address : Prathibha P Shivadas, HIG-A, #7, Ashwath Road Kalyanagiri Nagar, 570029, Mysuru, Karnataka, India. E-mail: prathibhapshivadas@gmail.com |
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| ABSTRACT |  | |||||||||||||||||||||||||||||||||||||||||||||||||||
: Introduction: Retroperitoneum is one of the largest and complex anatomical spaces in the body where, even before the clinical presentation, the tumours often grow silently to large sizes. Therefore, an early and accurate diagnosis is crucial. Among the various imaging modalities, Computed Tomography (CT) is the preferred imaging technique for the evaluation of retroperitoneal tumours. It plays an important role in determining the epicenter of tumour, size, tumour composition, extent, vascularity and effects on adjacent structures, and thus aids in treatment planning. Aim: The study aimed to evaluate various CT imaging findings of retroperitoneal tumours and to associate it with histopathological findings. Materials and Methods: A cross-sectional study was done at Department of Radiology in the tertiary care hospital for a duration of 12 months from 1st January 2019 to 31st December 2019. The study included 30 patients. Each patient was subjected to plain and contrast enhanced CT to characterise the retroperitoneal tumour. The results were tabulated and evaluated descriptively by Microsoft Excel 2016 and presented in figures, tables, frequency graphs and pie charts. Results: Out of 30 patients, 17 (56.6%) were males and 13 (43.3%) were females. Most commonly affected age group was seventh decade, followed by sixth decade. Histopathology confirmed the radiologic diagnosis in 26 cases. A total of 80% of the lesions were malignant and 20% were benign. Primary retroperitoneal tumours were the most common tumours (11 cases) accounting for 36.6% of cases. Among primary retroperitoneal tumours, lymphoma (four cases) was the most common tumour followed by lymph nodal metastases (three cases). Other four tumours were liposarcoma, extra-adrenal neuroblastoma, paraganglioma and lymphangioma. Majority of the tumours were solid (29 cases) and only one case was cystic. Heterogeneous enhancement was the most common pattern of enhancement which was seen in 23 cases. Infiltration of adjacent organ was seen in five cases, vascular encasement in seven cases and distant metastasis in six cases. Conclusion: The collective evaluation of various CT imaging findings of retroperitoneal tumours which includes the epicentre of lesion, tumour composition (solid, cystic, fat, calcification, necrosis), enhancement pattern, size, effect on adjacent organs (displacement or infiltration), vascular encasement and distant metastasis helps to arrive at an accurate radiologic diagnosis and thus guides in therapeutic planning. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Keywords : Adrenal metastases, Beak sign, Lymph nodal metastases, Lymphoma, Neuroblastoma, Renal cell carcinoma | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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DOI and Others :
DOI: 10.7860/IJARS/2021/44895:2598
Date of Submission: May 04, 2020 Date of Peer Review: Jun 18, 2020 Date of Acceptance: Aug 24, 2020 Date of Publishing: Jan 01, 2021 b#bAuthor Declaration:b?b • 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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| INTRODUCTION |
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Retroperitoneal tumours constitute diverse pathologic types of lesions, arising in the retroperitoneal spaces and pose a diagnostic challenge for the radiologists (1). Malignant retroperitoneal tumours occur more commonly than the benign ones (2). Knowledge of retroperitoneal anatomy and imaging characteristics of various retroperitoneal tumours provides important clues to narrow down the differential diagnosis and guides in clinical management. Several diagnostic modalities can be used for the evaluation of retroperitoneal tumours which include conventional methods (plain radiography, intravenous urography, retroperitoneal lymphography and angiography), Ultrasonography (USG), CT and Magnetic Resonance Imaging (MRI). USG is the initial imaging modality since it is inexpensive, easily available and easy to perform with lack of ionising radiation but the evaluation remains incomplete because of the large size of tumours which does not allow to precisely define the epicenter and relations with adjacent organs. MRI has the drawbacks of high cost, longer scan time and limited availability. Even before the clinical presentation, the retroperitoneal tumours can have widespread extension due to the loose connective tissue (3). Hence while imaging, the initial step is to confirm if the tumour is situated within the retroperitoneal space though it is difficult to determine when the lesion has reached a large size. However, this can be decided on the basis of displacement of normal anatomic structures (1),(4). Anterior displacement of the retroperitoneal organs firmly indicates that the tumour is of retroperitoneal origin. The retroperitoneal tumours are further classified into those originating from retroperitoneal organs and primary retroperitoneal tumours which arise independent of retroperitoneal organs. Before a tumour can be ascertained as primarily retroperitoneal, the possibility of its origin from a retroperitoneal organ needs to be excluded. The radiologic signs which aid in determining the organ of origin include the “beak sign,” “embedded organ sign,” “phantom (invisible) organ sign,” and “prominent feeding artery sign” (1),(5). The diagnosis of primary retroperitoneal tumour is considered when there is no definite sign to suggest an organ of origin. Among the primary retroperitoneal tumours, 70-80% is malignant which constitute 0.1-0.2% of all malignant tumours in the body (6). CT is the appropriate tool in imaging of the retroperitoneum as the difference in attenuation between the retroperitoneal fat and organs helps in the detection of retroperitoneal diseases and increases its diagnostic accuracy (7). Thus, the study was aimed to evaluate various CT imaging findings of retroperitoneal tumours and to associate it with histopathological findings. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Material and Methods |
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A cross-sectional study was done at Department of Radiology in Krishnarajendra Tertiary Care Hospital for a duration of 12 months from 1st January 2019 to 31st December 2019. Institute Ethics Committee approval was obtained (EC REG: ECR/134/Inst/KA/2013/RR-19). The patients of either sex, of any age group, who presented with clinically diagnosed retroperitoneal mass or ultrasound detected retroperitoneal mass were included. Clinical history was obtained with thorough physical examination and routine blood investigations including haemogram, urine analysis, random blood sugar, blood urea, serum creatinine, liver function tests, HBsAg and HIV serology. The patients who had history of allergy to iodinated contrast agents, deranged renal function tests, pregnant women, patients with unstable general condition and postoperative cases with residual or recurrent retroperitoneal tumours were excluded from the study. Based on the inclusion and exclusion criteria, a total of 30 patients were included in the study after obtaining the informed written consent from the patients. CT of abdomen and pelvis was performed with 128 slice single source dual energy Somatom Definition Edge Siemens MDCT (Multidetector CT) machine. Preprocedure preparation included that the patients should be nil per oral for about six hours before conducting the study, with normal renal function tests. Initially, unenhanced study was done followed by intravenous contrast study and the iodinated contrast agents namely Iopromide (Ultravist) or Iohexol (Omnipaque) were used at 2ml/kg body weight. Scans were obtained in portal phase. Arterial and delayed scans were also obtained whenever necessary. Scanning protocol: Region from both domes of diaphragm to pubic symphysis was included. Patients were asked to lie in supine position with arms above head and following parameters were used: 300 mA, 100 kV, pitch: 0.8, tube rotation time: 0.5s, slice thickness: 5 mm, scan orientation: craniocaudal, scan delay: 45s and FOV: 350 mm. The images were reconstructed to obtain 1mm sections in sagittal and coronal planes. All sections were evaluated for the exact location and origin of retroperitoneal tumours, its extent, tumour composition, enhancement pattern, displacement of adjacent structures, local invasion, vascular encasement and distant metastases. Patients were further evaluated by fine needle aspiration cytology, biopsy, and/or other operative procedure for histopathological examination wherever possible. STATISTICAL ANALYSIS The results of the study were tabulated and evaluated descriptively using Microsoft Excel 2016. Also, the results were presented in figures, tables, frequency graphs and pie charts. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Results |
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In present study, the total number of patients were 30. Of these, 17 (56.6%) were males and 13 (43.3%) were females. Most commonly affected age group was 61-70 years (Table/Fig 1). Youngest patient was aged nine months whereas the oldest patient aged 88 years 33and the mean age was 51.8 years (SD 23.85). A total of 80% of the lesions were malignant and 20% of the lesions were benign. The most common clinical symptom was pain abdomen, with duration of pain varying from one week to three months. Other symptoms included loss of weight, mass per abdomen, loss of appetite, jaundice, haematuria with either frank blood or just few drops with urine and low grade fever. Most of the patients presented with two or more clinical symptoms (Table/Fig 2). Primary retroperitoneal tumours were the most common tumours (11 cases). Among primary retroperitoneal tumours, lymphoma (four cases) was the most common tumour followed by lymph nodal metastases (three cases). Other four tumours were liposarcoma, neuroblastoma, paraganglioma and lymphangioma. Among adrenal tumours, metastases (three cases) were the most common tumours with lung carcinoma being the primary in all the three cases. Among renal tumours, Renal Cell Carcinoma (RCC) (three cases) was the most common tumour. Periampullary carcinoma (five cases) was the most common overall retroperitoneal tumour in present study (Table/Fig 3). In this study, tumour in 19 cases measured <10 cm in greatest dimension and 11 cases measured >10 cm. Paraspinal location was the most common epicentre of the tumours (11 cases). Majority of the tumours were solid (29 cases) and only one case was cystic. Four cases showed areas of fat attenuation, five cases showed calcification and necrosis was found in 18 cases. Heterogeneous enhancement was the most common pattern of enhancement which was seen in 23 cases. Displacement of adjacent organ was seen in 12 cases and infiltration of adjacent organ was seen in five cases. Vascular encasement was seen in seven cases and distant metastasis was seen in six cases (Table/Fig 4). Out of 30 cases, histopathological examination was obtained in 26 cases which showed similar findings as in CT diagnosis (Table/Fig 5). | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Discussion |
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Computed tomography plays an important role in the characterisation of retroperitoneal tumours by determining its location, origin, extent, composition (fat, calcification, and necrosis), enhancement pattern, effect on adjacent structures 34and distant metastases. The characteristic imaging findings can help narrow down the differential diagnosis and therefore aids in treatment planning (8). Malignant lesions were more common than the benign lesions. Similar findings were also seen in the studies conducted by Chaudhari A et al., and Stephens DH et al., (Table/Fig 6) (9),(10). But the number of benign cases in Stephens DH et al., was less compared to our study (10). This is because 10 recurrent cases were included in the Stephens DH et al., study which were all malignant, while no recurrent cases were included in current study. Both the above studies concluded that CT has a major role in the diagnosis of retroperitoneal tumours and their recurrences. Even in cases of advanced tumours, the knowledge provided by CT has been invaluable in developing a rational approach for its management. Primary retroperitoneal tumours constituted maximum cases in this study accounting for 36.6% (11/30) of cases with lymph nodal mass being the maximum accounting for 63.63% (7/11) of cases. Similar findings were seen in the study conducted by Chinwan D et al., in which most common retroperitoneal masses encountered were primary retroperitoneal masses accounting for 43.3% (13/30) of cases with lymph nodal mass (23%) being the maximum (11). This similarity could be due to similar number of total cases studied and demographic factors. The identification of fat and calcification in the retroperitoneal tumours significantly shortens the list of differential diagnoses. In this study, four cases showed areas of fat attenuation within the lesion, among which three cases were benign and one case was malignant (Table/Fig 7). Thus, presence of fat was more commonly found in the benign lesions. Similar finding was seen in the study conducted by Bosniak M et al., which reported that angiomyolipoma was diagnosed by detecting fat in the renal lesion and presence of fat is the only radiologic finding that can differentiate angiomyolipoma from RCC (12). Adrenal adenoma and myelolipoma showed areas of fat attenuation and the key feature which differentiates benign from malignant adrenal tumours is presence of significant intracellular cytoplasmic lipid (13). The presence of necrosis which appears as low attenuation with no contrast enhancement is an important finding most commonly found in the malignant tumours [1,9]. In this study, 18 cases showed necrosis, out of which 16 were malignant and two cases were benign which included pheochromocytoma and paraganglioma (Table/Fig 8). RCC, on non-enhanced scan was seen as hypodense lesion and showed heterogeneous postcontrast enhancement with central necrosis (Table/Fig 9). Calcifications were seen in 33.3% of cases and necrosis was seen in all the cases of RCC. Similar findings were seen in the studies conducted by Zagoria RJ et al., which reported that calcifications were visible in 31% and necrosis was noted in 87.5% (7/8) of cases and Hatimota P et al., which showed that necrosis was found in 94% cases of RCC (14),(15). Vascular encasement is also a feature of malignant tumour and determines the surgical resectability of the tumour. In this study, all the seven cases which showed vascular encasement were malignant tumours which included lymphoma (Table/Fig 10), neuroblastoma and periampullary carcinoma. Among the cases with periampullary carcinoma, three out of five cases had vascular involvement. Similar findings were seen in the study conducted by Lee ES et al., which reported that Multidetector CT is best for the assessment of vascular involvement, which is the crucial factor for predicting the surgical resectability of the tumour (16). In this study, there was one case of lymphangioma which was the only cystic lesion and appeared as non-enhancing multiloculated hypodense lesion of fluid attenuation (Table/Fig 11). Similar finding was also seen in the study conducted by Hayasaka K et al., which stated that lymphangioma showed fluid attenuation (17). In this study, there were three cases of neuroblastoma (median age 1.5 years) in which one of the cases showed intrathoracic extension (Table/Fig 12). Hugosson C et al., reviewed 31 children with abdominal neuroblastomas (median age 2 years), with USG and CT (18). They observed that CT and MRI were superior to USG. There was no significant difference between CT and MRI, in the assessment of the location or size of tumour. Intraspinal extension was more distinctly demonstrated with MRI. They concluded that either CT or MRI was best to assess the local disease while CT was best to assess the metastatic disease. Thus, imaging may be valuable for clinical assessment and pretreatment staging of abdominal neuroblastomas. Limitation(s) Limitations of this study were the small sample size and the inability to perform histopathological examination in four cases with adrenal lesions. The sample size was 30, since other studies on retroperitoneal tumours (Chaudhari A et al., Stephens DH et al., and Chinwan D et al.,) had similar sample size which could be due to less prevalence of the retroperitoneal tumours [9-11]. Also, the case with CT diagnosis of pheochromocytoma was not subjected to biopsy due to the risk of hypertensive crisis. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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