|Year : 2018 | Volume
| Issue : 2 | Page : 15-20
Ultrasound and Computed Tomography Evaluation of Paediatric Renal Neoplasms
Pragya Verma1, Sanjay Kumar Suman2, Bipin Kumar3
1 Senior Resident, Dept. of Radiodiagnosis, IGIMS, Patna, India
2 Professor, Dept. of Radiodiagnosis, IGIMS, Patna, India
3 Professor, Dept. of Pathology, IGIMS, Patna, India
|Date of Web Publication||10-Dec-2020|
Sanjay Kumar Suman
Professor and Head Dept. of Radiodiagnosis, IGIMS, Patna, Bihar
Source of Support: None, Conflict of Interest: None
Background: Previously, many different types of solid renal tumors were clubbed together under the heading of "Wilms Tumor". However, some of these have been proved to be distinct pathological entities in their own right which include Nephroblastomatosis, Renal cell Carcinoma, Mesoblastic nephroma, Multilocular cystic renal tumor, Clear cell sarcoma, Rhabdoid tumor etc.
Aim: We aim to evaluate Ultrasound and Computed Tomography features of malignant renal neoplasms in paediatric population and correlate the same with histopathological findings to assess the diagnostic accuracy of these two imaging modalities.
Material and methods: A prospective study of 30 patients was done and data was summarized under location, size, extent of involvement and imaging characteristics of renal tumours and metastases. Calculation of sensitivity, specificity, positive and negative predictive value and accuracy of the imaging modalities was done.
Result: Mean age at presentation was 3.74 years with male to female ration being 1.73:1. Spectrum of features on Ultrasound and CT scan is diverse and wide-ranging with variable amounts of necrosis, calcification and vascular thrombosis. Wilms tumor was found in 24(80%) cases making it the most common renal neoplasm in children followed by cystic nephroma. One case each of mesoblastic nephroma, clear cell sarcoma, renal cell carcinoma and secondary lymphoma was seen. Internal architecture is varied and it is often difficult to differentiate these tumors from Wilms Tumor.
Conclusion: A vast majority of renal tumors do not have characteristic imaging features and may sometimes remain indistinguishable from Wilms tumor on both US and CT scan.
Keywords: Paediatric renal neoplasm, US, CT, Histopathology, Wilms tumor
|How to cite this article:|
Verma P, Suman SK, Kumar B. Ultrasound and Computed Tomography Evaluation of Paediatric Renal Neoplasms. J Indira Gandhi Inst Med Sci 2018;4:15-20
|How to cite this URL:|
Verma P, Suman SK, Kumar B. Ultrasound and Computed Tomography Evaluation of Paediatric Renal Neoplasms. J Indira Gandhi Inst Med Sci [serial online] 2018 [cited 2021 Dec 4];4:15-20. Available from: http://www.jigims.co.in/text.asp?2018/4/2/15/302947
| Introduction:|| |
Wilms' tumour is the commonest tumor in children. Other less common tumours are Mesoblastic Nephroma, Multilocular Cystic Nephroma, Clear Cell Sarcoma and Rhabdoid Tumour. The imaging features of these tumors have been well described in the literature. Ultrasound (US) and Computed Tomography (CT) are the most commonly used imaging modalities in evaluation of renal neoplasms.
| Material and Methods:|| |
From July 2011 to December 2012, patients (<18yrs) presenting with renal masses and/or detected incidentally were subjected to imaging and a prospective comparative analytical study was done to assess the accuracy of imaging diagnosis after correlation with HPE.
| Methods:|| |
Study was done by Ultrasound (Toshiba Nemio) & CT scan (Somatom SR, Siemens). CT was done in 4-6 hrs fasting state. Uncooperative children were sedated. Non contrast CT scan was taken to visualise kidneys, its surrounding structures, any calcification and attenuation of mass. Non- ionic IV contrast media (2mg/kg) was injected and 3mm, 5mm to 10mm thick axial slices were taken in portal venous phase. Delineation of tumour, its internal architecture, vascularity, extension, thrombosis, retroperitoneal lymphadenopathy and metastasis were studied. Imaging diagnosis was then correlated with histopathological findings.
Statistical study: Analysis of data was done using data summarization in which calculation of appropriate statistics and display of information was done in the form of tables, graphs and charts. Calculation of sensitivity, specificity, positive and negative predictive value and accuracy of the imaging modalities was done.
| Results:|| |
30 patients presenting with renal mass and incidentally diagnosed renal mass on US and CT were studied. The age ranged from 5months to 12 years with mean age of 3.74 years (S.D 2.65). Majority were between 1 to 5 years of age. 19 (63.3%) patients were male and 11 (36.7%) were female with male to female ratio of 1.73:1. Twenty nine (97%) patients had presented with abdominal lump, 6 (20%) with pain, 5(16.7%) with malaise and 3(10%) with haematuria [Graph 1].
| US Findings:|| |
On USG, 18 (60%) patients had right renal mass and 12 (20%) had left renal mass. Size of the tumour varied from 4.5cms to 18 cms. The size of the tumour was 5-10cms in 15 (50%) cases, 10-15cms in 12 (40%) cases, more than 15 cms in 2 (6.7%) cases and less than 5 cms in 1(3.3%) case. In 24 (80%) patients, almost entire kidney was involved. Upper pole was involved in 4 (13.3%) and lower pole in 2 (6.67%) patients. Six (20%) cases had purely solid mass, out of which 4 (66.7%) were hyperechoic and 2 (33.3%) hypoechoic. Sixteen (53.3%) renal tumours had heterogeneous echo texture. Renal vein was not visualised in 3 (10%) cases due to large size of the tumour mass and/or bowel gas whereas 3 (10%) cases showed Renal vein invasion and 4 (13.3%) cases both Renal vein and IVC invasion. In 20 (66.7%) cases Renal vein infiltration was absent.
| CT Findings:|| |
In 11 (36.7%) cases, tumour was crossing the midline and in rest cases tumour was not large enough to cross the midline. Calcification was present in 8 (26.7%) and necrosis in 24(80%). Ten (33.3%) cases showed more than 50% necrosis and 14(46.7%) showed less than 50% necrosis. Twenty (66.67%) cases did not show any vascular invasion. Isolated Renal vein infiltration was present in 6(20%) cases and 4(13.33%) had both RV and IVC infiltration [Graph 2]. 24(80%) cases demonstrated post contrast enhancement >15 Hounsfield Unit (HU).
A diagnosis of Wilms' tumour (WT) was made in 26(86.7%) cases on US. CT showed 25(83.3%) cases of it and one case was found to be mesoblastic nephroma. Out of these 25 cases of WT, 23(77%) cases were confirmed. One case turned out to be Renal Cell Carcinoma while another was clear cell sarcoma on histopathological examination. Similarly one, out of 3 diagnosed cases of multilocular cystic tumour on imaging, turned out to be a case of cystic Wilms tumor on histopathology. One case of intestinal lymphoma was presented as renal mass which was diagnosed correctly by both US and CT. The comparative diagnostic details of paediatric neoplasms by different modalities are shown in [Graph 3].
| Wilms' Tumour (WT):|| |
WT was the commonest (24; 80%) renal neoplasm. The age at presentation ranged between 6 months to 12 years with mean age of 3 years. Majority of patients was seen in the age group of 1-5 years. Thirteen were male and eleven were female with male to female ratio of 1.18:1. The presenting complain in the descending order of frequency were lump (24; 100%), pain (5; 20.8%), malaise (4; 16.7%) and hematuria (2; 8.3%). Slightly more predilection of right side (14; 58.3%) was found. In 4(16.7%) cases, the renal mass was found in the upper pole while 1(4.2%) case it was in the lower pole. In 19(79.2%) cases almost the entire kidney was replaced by tumour. Size of the tumour mass ranged from 5-18cms. Eleven (45.8%) cases had tumour size 5-10cms, 11(45.8%) cases had 10-15cms and 2(8.3%) had more than 15cms.
USG showed predominantly solid tumour in 23 (95.8%) cases. In 16(66.7%) cases, lesions showed heterogeneity because of areas of haemorrhages, necrosis and tumour vascularity. Four (16.7%) cases showed solid-cystic internal architecture. In 3(12.5%) cases, lesions were hyperechoic and in 1(4.2%) case, lesion was hypoechoic. One (4.2%) case of Wilms tumour was purely cystic with multiple septations and was diagnosed as cystic nephroma. [Figure 1]a. Retroperitoneal lymphadenopathy was detected in one case. Colour Doppler imaging of 23 solid lesions showed peripheral and intralesional vascularity. One cystic tumour showed some flow in the small solid nodule in the cyst. RV infiltration was found in 3(12.5%) cases and 4(16.7%) showed both RV and IVC invasion. Three (12.5%) cases showed difficulty in assessing vascular invasion due to large size of the tumour and bowel gas. When compared with FNA/histopathology findings, sensitivity of ultrasound in diagnosing Wilms Tumor was 85% to 99.89% while its specificity was 11.81%-88.19%. The probability that disease is present when the test is positive was close to 88% while the negative predictive value was 27%- 96%.
CT showed calcification in 7(29.2%) cases and necrosis in 22(91.7%) cases. Ten (41.7%) cases presented with tumour crossing the midline.[Figure 1]b. Twenty three (95.8%) cases showed avid enhancement after intravenous contrast administration. Six (25%) cases showed renal vein invasion while 4(16.7%) showed both RV and IVC invasion. [Figure 1]c
When correlated with FNA/histopathological findings, sensitivity of CT scan in diagnosing Wilms Tumor reached 99.9% and specificity was 4.33% to 77.72%. The positive predictive value was close to 85% and negative predictive value was 67%. The diagnostic accuracy of CT scan was thus approximately 85%.
3 cases of cystic nephroma were diagnosed on imaging. On FNA/histopathology one of the cases turned out to be cystic Wilms Tumor. The two cases of cystic nephroma were male of age 1 and 2 years. Both presented with painless lump in the flank. While in one case tumour was on right side, the other was on left side. Both were around 5- 10cms in size and were seen involving the entire kidney. On US, the tumours were intrarenal multicystic mass with no solid or nodular elements. No significant intratumoral vascularity was seen. On CECT, minimal septal enhancement was seen. [Figure 2]. The sensitivity of both ultrasound and CT in diagnosing Cystic Nephroma was 100% while the specificity was only 3.6%. Thus, the diagnostic accuracy of imaging modalities was a poor 10%.
|Figure 2: Cystic nephroma in a 1 year old boy presenting with painless lump. US demonstrates a well defined multilocular cystic mass.|
CT shows cystic mass with attenuation value similar to water with multiple enhancing septae.
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| Mesoblastic Nephroma:|| |
One case of mesoblastic nephroma was found in the present study. The patient was 5 months young male who presented with painless lump in right flank. The mass was well defined, solid, hypoechoic and homogenous on US. Colour Doppler imaging showed significant perilesional vascularity but minimal intralesional flow. We found difficulty in differentiating mesoblastic nephroma from congenital WT on US. CT demonstrated a solid homogenous intrarenal mass involving the renal sinus. No necrosis or calcification was seen. CECT showed minimal enhancement. [Figure 3]. So, while the sensitivity of ultrasound in detecting mesoblastic nephroma was 0%, sensitivity of CT was 100%.
|Figure 3: Mesoblastic nephroma in a 5 months old boy presenting with painless lump. US shows well defined solid hypoechoic and homogenous mass with minimal intralesional vascularity.|
CT demonstrates a solid homogenous intrarenal mass involving the renal sinus. Minimal contrast enhancement seen.
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| Clear Cell Sarcoma:|| |
This was seen in a 3years old male presenting with left flank lump and pain. On US, there was a large (11cms) solid, hyperechoic sharply demarcated intrarenal mass. Significant perilesional and intralesional vascularity was present but intravascular extension was absent. [Figure 4]. No calcification and less than 50% necrosis were present. CECT showed considerable enhancement. There was no lymphadenopathy, vascular invasion or distant metastasis. Differentiation of clear cell sarcoma from WT was found difficult on both US and CT and final diagnosis was made on histopathological examination of resected specimen.
|Figure 4: Clear cell sarcoma in a 3 years old boy presenting with lump and pain abdomen. CT demonstrates large heterogeneously enhancing mass with non enhancing areas representing necrosis. Lesion crosses the midline. Calcification is absent. This was diagnosed as Wilms tumor on imaging.|
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| Renal Cell Carcinoma:|| |
One case of Renal Cell Carcinoma (RCC) was seen in a 10years old boy who presented with lump and haematuria. US revealed a 9.0×7.8cms sized heterogenous mass with some calcification. Intratumoral vascularity was present. On CT, mass appeared heterogenous due to necrosis (<50%) and calcification [Figure 5]. CECT showed little enhancement. RCC and Wilms tumour were found indistinguishable on imaging and definite diagnosis was possible after histopathological examination of the tumour.
|Figure 5: Renal cell carcinoma in a 10 years old boy presenting with lump and hematuria.|
CT demonstrates heterogeneously enhancing mass due to areas of necrosis. Few tiny foci of calcifications were also seen.
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Thus, both ultrasound and CT scan have poor diagnostic accuracy when it comes to diagnosing clear cell sarcoma as well as renal cell carcinoma.
| Lymphoma:|| |
A 5year old male patient with Burkitt lymphoma involving ascending colon was found to have a larger right kidney with slightly decreased echotexture. CT demonstrated reniform enlargement and no enhancement on contrast administration. No perinephric involvement or any retroperitoneal lymphadenopathy was seen. [Figure 6]
|Figure 6: Lymphomatous involvement of kidney in a 5 year old boy with pre-existing Burkitt's lymphoma of the ceacum and ascending colon. CT demonstrates diffuse thickening of the ceacum and part of ascending colon Right kidney is enlarged without distortion of the normal shape of kidneys. Poor contrast uptake is also seen.|
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| Discussion:|| |
A variety of paediatric renal tumour was diagnosed in the present study, most common being WT (24; 80%) followed by Cystic nephroma (2; 6.67%). Each of Mesoblastic Nephroma, Clear Cell Sarcoma, Renal Cell Carcinoma and Lymphoma comprised of 3.33%. Similar result was found in the study done by D. Miniati et al. who studied 92 patients of paediatric renal tumour, of which 68 (74%) were WT and 24(26%) non WT.
Kullendorf et al. studied the clinical course of 48 treated cases of WT. Seven were less than 1 yr of age and 4 were under the age of 6 months. Most common clinical feature was lump abdomen. In our study, age at presentation ranged between 6months to 12 years with mean age of 3 years. The presenting complain in descending order of frequency were lump (24; 100%), pain (5; 20.8%), malaise (4; 16.7%) and haematuria (2; 8.3%).
Other paediatric renal masses may be differentiated from WT on the basis of clinical and imaging features. WT is distinguished by vascular invasion and displacement of structures. In large tumours adequate evaluation of RV and IVC by US may become difficult because of marked compression and displacement by the tumour. Scott DJ et al. found that USG and X-ray were sufficient to diagnose WT and CT was superior for demonstrating relationship of the mass to the great vessels, retroperitoneum and spinal canal. IVC invasion was found to be strongly predictive of WT. According to study done by Marilyn J Siege, CT was found superior to US for detection of regional lymph node, bilateral tumours and for pulmonary metastasis. Slasky studied four cases of WT involving peritoneum on CT. In our study, on US, RV infiltration was found in 3(12.5%) cases. Four (16.7%) cases showed both RV and IVC invasion. Three (12.5%) cases showed difficulty in assessing vascular invasion due to large size of the tumour and bowel gas and was found invaded on CT. One case showed retroperitoneal lymphadenopathy. Neither peritoneal involvement nor metastasis was seen.
Cystic Nephroma at US appears as multicystic mass without any solid or nodular elements. CT demonstrates a well- circumscribed, encapsulated multicystic mass with variably enhancing septa and absence of excretion of contrast agent into the loculi. The contents of the cyst may have similar or slightly higher attenuation than that of water. If the cystic spaces are very small, the closely packed septa can mimic a solid mass. In our study, 2 cases of Cystic Nephroma of 5- 10cms in size were seen involving the entire kidney with classical US and CT findings. No significant intratumoral vascularity was seen on colour Doppler sonography. Septal enhancement was seen on contrast enhanced CT.
Differentiation between Congenital Mesoblastic Nephroma and WT was found difficult on US and CT in the present study which is similar to study done by Nguyen MM et al. where the diagnosis was made by histopathology. Glass RB et al. reviewed USG and CT findings of clear cell sarcoma in 12 children between the age group of 1-6 years and found that all except one were predominantly solid, all contained uncomplicated fluid filled cysts. Drawback of his study was that according to them the radiologic features were common to all malignant tumours. In the present study, one case of clear cell sarcoma was seen in a 3years old male which was large and predominantly solid and showed considerable enhancement. There was no lymphadenopathy, RV invasion or distant metastasis. Differentiating Clear Cell Sarcoma from Wilms tumour on imaging was found to be difficult and diagnosis was made on histopathology.
Miniati et al analysed 92 CT studies of children with renal mass out of which 4(4.3%) were RCC. Children suffering from RCC are relatively older, clinically present with hematuria and calcification on CT study. A study done by Kabala JE et al, demonstrated calcification on CT and on radiographs. In addition, CT showed well defined tumour which were echogenic on USG and these findings were different from adult cases of RCC. A case of RCC was seen in a 10-year old boy in our study who presented with lump and haematuria. Imaging revealed heterogeneous mass with some necrosis and calcification. Little enhancement was seen on contrast administration.
NB Chepuri et al. studied renal lymphoma in 11 children. Non-Hodgkin's lymphoma was found in 10(91%) cases and Burkitt lymphoma in 5(45.5%) cases. Multiple bilateral masses were the most common CT appearance. Less common presentation included focal solitary masses or engulfing masses and reniform enlargement of kidneys with little or no enhancement. Retroperitoneal lymph node enlargement and other organ involvements were associated findings. In our study, reniform enlargement of one kidney was seen in a 5year old male patient with Burkitt lymphoma of ascending colon. No perinephric involvement or retroperitoneal lymphadenopathy was seen.
| Conclusion:|| |
Spectrum of features on Ultrasound and CT varied from completely solid to markedly heterogenous, few calcific foci to chunky calcifications, no necrosis to extensive necrosis and no vascular invasion to invasion of renal vein and inferior vena cava. Ultrasound is the initial modality of choice in diagnosing benign and malignant. CT easily differentiates between benign and malignant pathologies involving the kidney by its superior spatial and contrast resolution and also enhancement patterns. Some renal tumours do not have characteristic imaging features and may remain indistinguishable from Wilms tumour on imaging.
| References|| |
Miele V, Galluzzo M, Bellussi A, Valenti M. Spiral computerized tomography in the study of renal neoplasms in children. Radiol Med. 1998;95:486-92.
Hatimota P, Vashist S, Aggarwal K, Kapoor A, Gupta NP. Spectrum of US and CT Findings In Renal Neoplasms With Pathologic Correlation. Ind J Radiol Imag 2005;15:117-25.
Miniati D, Gay AN, Parks KV, Naik-Mathuria BJ, Hicks J, Nuchtern JG et al. Imaging accuracy and incidence of Wilms' and non-Wilms' renal tumors in children. J Pediatr Surg. 2008;43:1301-7.
Kullendorff CM, Weibe T. Wikms' tumour in infancy. Acta Paediatr. 1998;87:747-50.
Schmidt T, Hohl C, Haage P, et al. Diagnostic accuracy of phase- inversion tissue harmonic imaging versus fundamental B-mode sonography in the evaluation of focal lesions of the kidney. AJR Am J Roentgenol. 2003;180:1639-1647.
Lowe LH, Isuani BH, Heller RM, Stein SM, Johnson JE, Navarro OM et al. Pediatric renal masses: Wilms tumor and beyond. Radiographics. 2000;20:1585-603.
Scott DJ, Wallace WH, Hendry GM. With advances in medical imaging can the radiologist reliably diagnose Wilms' tumour? Clin Radiol. 1999;54:321-7.
Marilyn J Siegel, Ellen M Chung. Wilms' Tumor and Other Pediatric Renal Masses. Magn Reson Imaging Clin N Am. 2008;16(3):479-97.
Slasky BS, Jacob BZ, Freeman Arnold I, Peylan-Ramu Nili. CT appearances of involvement of the peritoneum, mesentery and omentum in Wilms' tumor. Pediatric Radiology. 1997;27:14-7.
Silver IMF, Boag AH, Soboleski DA. Multilocular Cystic Renal Tumor: Cystic Nephroma. RadioGraphics 2008; 28:1221-1227.
Nguyen MM, Katzberg RW, Wootton-Gorges SL, Das S. Computed tomography and magnetic resonance imaging in paediatric urology. BJU Int.2006;98:273-7.
Glass RB, Davidson AJ, Fernbach SK.. Clear cell sarcoma of the kidney: CT, sonographic, and pathologic correlation. Radiology. 1991;180:715-7.
Kabala JE, Shield J, Duncan A. Renal Cell Carcinoma in childhood. Pediatr Radiol. 1992;22:203-5.
Chepuri NB, Strouse PJ, Yanik GA. CT of renal lymphoma in children. Am J Roentgenol. 2003;180:429-31.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]