SIR J.C.BOSE MEMORIAL ORATION-1999
Year : 2000 | Volume
: 10 | Issue : 3 | Page : 137--146
Sir J C Bose Memorial Oration - 1999: Imaging in renal masses
4-Talkatora Lane, New Delhi 110 001, India
S S Doda
4-Talkatora Lane, New Delhi 110 001
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Doda S S. Sir J C Bose Memorial Oration - 1999: Imaging in renal masses.Indian J Radiol Imaging 2000;10:137-146
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Doda S S. Sir J C Bose Memorial Oration - 1999: Imaging in renal masses. Indian J Radiol Imaging [serial online] 2000 [cited 2020 May 31 ];10:137-146
Available from: http://www.ijri.org/text.asp?2000/10/3/137/30601
Honorable President IRIA Dr. Kakarla Subba Rao, Secretary-General Dr. Anand Abkari, Respected Teachers, Distinguished Guests, My Dear Colleagues and Students
It is a matter of pride for me to speak in the honor of one ,of the greatest scientists born in this country during last century. I am extremely thankful to you all, the members of IRIA and especially to the members of the credential committee for providing me this opportunity.The year was 1990 and the place, Paris. The International Congress of Physics held at that time was attended by the great saint of India, Swami Vivekananda , who in his speech said, "Here in Paris have assembled the great of every land, each to proclaim the glory of their country. Savants will be acclaimed here, reverberations will glorify their countries. Where is the representative of the country of my birth?" And there stood the young man Jagdish Chandra Bose.
Sir J.C. Bose was one of the greatest scientists of our country. His major contributions include separation of electromagnetic waves from light. For the first time in the history, he demonstrated the propagation of, electromagnetic waves across two rooms situated 75 feet apart. This almost coincided with Roentgen's discovery of x-rays in the year 1895. Bose also demonstrated similarity of response to stimulation in the plant and animal tissues. He established through his experiments that the plants are also living beings. His other works included common physiological laws obeyed by certain living and non-living systems and he presented this work in 1900 in Paris. I pay my sincere tribute to the great man in the form of my talk - "Imaging in Renal Masses". Like a Swiss knife, which has a number of tools, we as radiologists have a number of imaging modalities, viz., Ultrasound, conventional radiology, CT, MR, PET and radionuclide scanning. A number of small and large masses are incidentally detected when US and CT are performed for other reasons ,. CT is more sensitive for the detection of renal masses than US and intravenous urography (IVU) ,. Whatever imaging modality is used to evaluate a renal mass, our approach should be to come to a conclusion as to whether the mass is cystic or solid. If it is not possible to do so, we call it indeterminate.
SIMPLE CYST/ SOLID / INDETERMINATE MASS
A simple cyst has definite criteria and these are - sharp outline, homogenous fluid contents and through transmission on ultrasound. An occasional septum does not make it complicated. Absence of enhancement on CT or MR with contrast makes it a simple cyst. On CT, a hypodense fluid attenuation lesion, sharply demarcated with a typical beak sign [Figure 1], is a classical example of a simple cyst. A solid mass is clearly solid. Even if it has fluid attenuation areas, it is solid in the majority of its portion. It lacks two of the criteria of the simple cyst. The indeterminate mass is usually a complicated cystic mass [Figure 2]. It generally lacks at least one criterion of a simple cyst and in such cases one has to resort to either FNAC or one of the additional modalities to evaluate it further.
The common examples in this category include renal abscess and necrotic renal cell carcinoma.
The other thing that helps in the evaluation of renal masses is the age group of the patient. The masses common in new-borns and young infants are hydronephrosis and Wilms' tumor. These two form more than 50% of abdominal masses at this age. Multicystic dysplastic kidney, polycystic disease of infantile type, renal vein thrombosis commonly infective in origin, mesoblastic nephroma and an ectopic kidney may present clinically as a renal mass. The pediatric age group has the Wilms' tumor as the commonest entity and the less common masses at this age, include clear cell carcinoma, rhabdoid tumor, mesoblastic nephroma, rarely renal cell carcinoma, lymphoma and leukemia.
In adults, the cystic masses include simple cyst, complicated cyst, polycystic disease and rarely multicystic dysplastic kidney and cystic neoplasms such as renal cell carcinoma, multilocular cystic nephroma and inflammatory cystic masses such as renal abscess and hydatid cyst. Amongst the neoplastic lesions, the common solid lesions in the kidneys in adults are renal cell carcinoma, transitional cell carcinoma, oncocytoma and angiomyolipoma.
CYSTIC RENAL MASSES
A simple cyst is the commonest cystic lesion of the kidney. Its margins are sharp, and contents usually homogeneously fluid showing the unique feature of sound transmission on US. It can be very large and can cause displacement of the kidney. On T2W images on MR, one finds a simple cyst as a bright signal area. The cyst may be located in the parapelvic region where it can cause some confusion on IVU. A simple cyst is perhaps the commonest renal mass and one or more simple cysts after the age of 50 are found in more than 50% individuals. Things may not always be straightforward. A simple cyst may become complicated as a result of hemorrhage, infection or other processes that thicken part or all of the wall , may show increased density of its contents ,,, cause calcification within the wall or may develop a septum . One can have a lesion, which looks like a cyst on CT but is much denser, the so-called hyperdense cyst [Figure 3]. This may appear solid because of higher attenuation values, which are actually due to bleeding in the cyst or inspissated material similar to milk of calcium or high protein levels ,,. Hyperdense cysts are common in autosomal dominant polycystic disease . Follow up of hyperdense cysts other than polycystic disease is prudent as renal cell carcinoma may mimic this appearance ,.
Bosnaik worked out a categorization of cystic masses of the kidney largely based on CT  [Table 1]. He put uncomplicated benign cysts in Category I where generally follow up is not required. Category II lesions are those where there is minimal complication in the form of thin septae or minimal calcification without any enhancement. Usually these cases may be followed up on imaging and one need not resort to surgery or any major intervention. Category III lesions are moderately complicated, where the margins of the lesion are irregular. There may be nodularity, thickened septa or contrast enhancement on CT or MR. These lesions usually require surgery but the decision is individual based. Category IV lesions are clearly malignant cystic lesions and they have irregular thick margins, solid elements and surgery is mandatory in such cases.
Calyceal diverticula may be incidentally detected as cystic, lesions on both CT and US. These may become complicated with formation of calculi, debris or milk of calcium, the latter seen as layered high density. These cystics spaces are lined by transitional epithelium and communicate with the collecting system through a narrow opening.
MULTILOCULATED CYSTIC MASSES
Multilocular cystic nephroma
These lesions involve a part of kidney, which is replaced with a focal area of multiple septa and cystic components. It may be difficult to differentiate from renal hydatid cyst. Multilocular cystic nephroma occurs either at a very young age towards middle age in women. On CT, the septa are relatively thin with no enhancement , calcification being present in about 10% cases  and hemorrhage being uncommon. The septa are normally better differentiated on ultrasound [Figure 4]. On angiography, one finds a space-occupying lesion splaying the vessels, but no definite signs of malignancy in the form of neovascularity.
MULTIPLE CYSTIC LESIONS
The common conditions are multiple simple cysts, polycystic disease of infantile, childhood or adult varieties, multicystic dysplastic kidney and an interesting condition, uremic cystic disease. In Dolycvstic disease, the kidneys are enlarged with multiple cysts of varying sizes [Figure 5]. Generally, there is a family history. In upto 50% of patients, cysts may also be seen in the liver, in five percent of patients in the spleen and in a smaller percentage in the pancreas, pituitary gland, lungs, seminal vesicles and ovaries . Fluid-fluid levels are due to repeated hemorrhages. In contrast, multicystic dysplastic kidney shows almost complete replacement of renal parenchyma by cysts. These are usually seen in neonates or infants and if unilateral, may persist in adults as a small to moderate sized cystic structure .
In chronic renal failure, repeated dialysis leads to uremic cystic disease with formation of multiple cysts in small contracted kidneys [Figure 6]. The incidence of renal cell carcinoma developing in these cysts is quite high and therefore one has to look for additional changes in the cysts.
Many a times, in a patient undergoing repeated lithotripsy for a hard stone, a large subcapsular hematoma / urinoma presenting as a cystic renal mass may develop [Figure 7].
INFECTIVE CONDITIONS OF THE KIDNEY
A focal renal abscess appears as a fluid containing lesion spouting on one side, about to leak [Figure 8]. There is a zone of transition around it, representing inflammation (a sort of nephroma) where the necrosis is yet to take place.
Thickening of Gerota's fascia and inflammatory strands are common in acute infections and these are usually due to increased vascularity and edema . A perinephric abscess may have air-fluid levels. This is because of gas forming organisms. In diabetics, emphysematous pyelonephritis may occur due to E.coli infection and result in impaired vascular supply with production of carbon dioxide from necrotic tissue . Plain radiographs, CT and US are all characteristic and show gas in the renal parenchyma. A predominant solid lesion with some necrosis and enhancement can also be seen in tuberculosis. It is not always possible to differentiate a malignant tumor from renal abscess ,
We also had one patient for whom the initial diagnosis was an abscess, but the presence of nodular calcification made us advise follow up, and eventually proved to be a hypernephroma [Figure 9].
In pyonephrosis, there is infection in a dilated pelvicalyceal system. US is not only diagnostic, demonstrating internal echoes [Figure 10] but also provides guidance for aspiration and placement of a nephrostomy tube. Fluid-fluid levels, debris inside an obstructed kidney with a calculus, and extension into the perinephric space occur in xanthogranulomatous pyelonephritis [Figure 11]. Where the inflammatory response is relatively inadequate as compared to a pyogenic abscess. The causative agent is Proteus. Apart from the dilated pelvicalyceal system, cavitation and destruction of the renal parenchyma may also be present.
Renal vein thrombosis is another condition, usually secondary to septicemic states, presenting as sudden development of a renal lump, basically representing an engorged kidney. Contrast studies on CT or MR show a thrombus in the vein that may continue into the IVC.
The kidney is an uncommon site for hydatid disease. Nevertheless, it may be involved and a multilocular cystic mass with mural calcification is characteristic .
HYDRONEPHROSIS AND RELATED CONDITIONS
Gross hydronephrosis is simple to detect with US and may be associated with a calculus. In addition to US, IVP, plain CT, MR pyelogram (HASTE sequence) is also being used to evaluate hydronephrosis. One of the advantages of MR pyelogram is that no contrast is required. A hydronephrotic sac may develop a soft tissue mass within itself, which may represent a hematoma or mesenchymal malignant tumor [Figure 12]. A urinoma may occur in an already obstructed hydronephrotic kidney secondary to calculus, trauma and posterior urethral valve  [Figure 13]. Sometimes these urinomas may persist for years after the trauma.
RENAL NEOPLASIC LESIONS -Benign and Malignant
Amongst benign tumors, angiomyolipoma (AML) is the most common. Generally there is no problem in diagnosis, particularly on CT . The fatty, soft tissue and angiomatous components are fairly clear in a majority of these cases. Occasionally, the lesion is very large, with associated hemorrhage [Figure 14] which may extend into the perinephric space. A small pure lipoma may not be differentiated from AML. The lesions are hyperechoic on US, hypodense on CT and hyperintense on T1 W images on MR. The differential diagnosis also includes renal cell carcinoma. Occasionally fat has also been demonstrated in oncocytoma, metastases and pararenal space liposarcomas engulfing the kidney.
SMALL/ VERY SMALL RENAL MASSES
It is possible to miss a subcentimeter renal mass on ultrasound. Even on CT, the likely pick up rate for renal masses of less than 1 cm size is about fifty percent. A small renal mass means that the lesion is 1.5 to 3cm in size. A very small mass is less than 1.5 cm. The sensitivity of CT in detecting lesions 3 cm or less is 94%
Compared to that of US (79%) or IVU (67%) ,[ 8], . In older patients, most lesions are cysts and one need not do anything. In very old patients with a solid mass which is very small, follow up is recommended at about six months interval initially and after that every year till the lesions is 2 cm or more at which time intervention may be needed. MRI is useful where there is renal insufficiency and history of contrast allergy.
RENAL CELL CARCINOMA (RCC)
The most common malignant tumor, renal cell carcinoma accounts for 3% of all malignancies . The tumor is fairly big and solid with some necrotic components. A portion of the kidney may be well preserved or sometimes the lesion may completely replace the kidney. An age-old staging system is still relevant, and that is the Robson's classification  [Table 2]. A small Stage-I tumour is very well confined although may be protruding outside the renal outline. Stage-I tumors can be very large yet still confined to renal capsule. The size of the tumor generally does not make it more lethal. Renal cell carcinoma may be almost completely cystic, with solid components difficult to appreciate [Figure 15]. In such cases it may be difficult to differentiate them from a complicated large cyst.
A stage-II tumor extends into the perinephric space and stage III tumor may be associated with regional lymph node enlargement or may have an extension into the renal vein, IVC  and right atrium. CT has an accuracy of 80% and specificity of 96% for the diagnosis of venous extension ,. In such situations, MRI is superior because of its multiplanar capability and one can also perform an MR angiogram , [Figure 16].
Ultrasound and color Doppler are also very useful'. Ultrasound is considered to be the best modality to look for the intra-hepatic portion of IVC in such cases [Figure 17]. The extent of IVC invasion determines the need to involve a cardio-thoracic surgeon. On color Doppler, apart from venous extension, presence of blood flow may be seen in the tumor thrombus, thus enabling its differentiation from a bland thrombus. Low resistance flow may be seen in the vessels in the malignant tumor. A mass in the hydronephrotic kidney may represent just a clot or actual mesenchymal tumor; in such a situation the presence of vessels in the lesion within the hydronephrotic kidney indicates a mass.
Ultrasound is not useful in staging of renal cell carcinoma because of its problems in diagnosing small masses and difficulty in evaluating retroperitoneal extension. CT is the main modality for staging with an accuracy of about 90%. However, the problem areas in CT include the demonstration of tumor thrombus in the right renal vein because of its small length. Also, the presence of an additional renal vein may be difficult to ascertain. CT angiography enables us to overcome this problem to some extent. The differentiation between stage I and II neoplasms, is difficult and likely to be incorrect at least 50% of the times on both CT and MR. This is normally not important because the surgical approach is the same for both stages. In the presence of a solitary functioning kidney, it becomes extremely important however because a decision about partial nephrectomy may have to be taken. The accuracy of MR staging is somewhat the same. Its advantages include better demonstration of venous extension and differentiation of malignant from bland thrombus. MR may not require any contrast. The problems are again difficulty in the differentiation of stage I and I I neoplasms and differentiation of lymph nodes from bowel loops.
ONCOCYTOMA [Figure 18]
Oncocytoma is a sharply defined mass, which may show central satellite scar when large. On catheter angiography, oncocytomas show a classical spoke-wheel appearance, but diagnosis is seldom made with confidence and is usually after nephrectomy. When compared, 82% of oncocytomas less than 3 cm are homogenous and 42% of RCC of similar size are homogeneous 
TRANSITIONAL CELL CARCINOMA (TCC)
Uro-epithelial malignancy is the second commonest type of malignancy in the kidney and 85-90% are TCCs and 10%, squamous cell carcinomas . Traditionally, IVU has been used to diagnose TCC by showing an indirect filling defect, which could also be due to a clot. A careful ultrasound examination can pick up the mass causing splitting of collecting system echoes [Figure 19]. CT combines the advantages of IVU and ultrasound, i.e., the mass as well as the filling defect is seen in the renal pelvis. An advanced case of TCC invading renal parenchyma, may be difficult to differentiate from an RCC invading the renal pelvis  [Figure 20]. Stippled calcification may occur on the surface of the mass . Squamous cell carcinoma of renal pelvis is associated with calculus and related inflammation and infection ,.
Renal sarcomas are rare highly malignant tumors, usually very large with their appearance being indistinguishable from RCC.
PEDIATRIC RENAL MASSES
Wilm's tumor is the commonest primary malignant renal tumor of childhood representing 20% of all abdominal masses with affected children being less than four years old. A large spherical, partly intra-renal mass [Figure 21] is common, though complete replacement of the kidney may occur. About 15% contain calcification or fat. Perinephric extension (20%), venous invasion (5-10%) and retroperitoneal nodes (20%) may be seen . Metastases to lungs and liver, are seen in about 10% children at the time of presentation.
Nephroblastomatosis is due to persistence of fetal renal blastema and may act as a precursor of Wilm's tumor. Low attenuation subcapsular nodules with poor corticomedullary differentiation may be seen on imaging.
The commonest solid mass in the first month of life is mesoblastic nephroma. There is no way one can differentiate it from a Wilm's tumor. They are generally benign tumors. Rarely, they have been reported to metastasize and patients have died of metastases.
BILATERAL SOLID LESIONS
Bilateral solid lesions can be due to three conditions. Non-Hodgkin lymphoma is the commonest followed by metastases in the older age and Von-Hippel-Lindau disease in the younger age group. Lymphoma usually appears as multiple hypodense masses in both the kidneys. The presence of lymph nodes in the retroperitoneum provides an additional clue to the diagnosis. A solitary lymphoma deposit can not be differentiated the from oncocytoma or renal cell carcinoma.
There are two peculiar tendencies of lymphoma, one is to invade the renal sinus region and the second, to spread around the kidney in a carpet like fashion, without affecting renal function , [Figure 22].
Von Hippel Lindau's disease (VHL) is associated with cysts, adenomas and adenocarcinomas in the kidneys and also cysts in the pancreas [Figure 23]. RCC can be expected to develop in about 45% of patients .
Radionuclide scan has its role in a group of conditions put together under the heading of pseudo-tumors. These include prominent column of Berlin, dromedary hump and focal prominence of cortical contour near a scar. In such situations, a radionuclide scan is helpful, like it shows flattening of the lateral surface of the kidney in dromedary hump.
A suspected renal mass should undergo an ultrasound as the first line of imaging. A confident diagnosis of simple cyst should make one stop from further imaging. A solid or indeterminate mass should be further evaluated on CT, which is able to sort out the problem in the majority of cases and is also able to provide a complete staging of malignant tumors. In cases with clear hydronephrosis on US, an IVP is useful to look for calculus, renal function, and anatomy of the urinary tract and TCC. In some of these cases, CT or MR will also be required. If there is a problem in CT about venous invasion or any other query, an MR should be of further help.
|1||Afsar H, Yagci F, Meto S, Aybasti N. Hydatid disease of the kidney: evaluation and features of diagnostic procedures. J Urol 1994; 151:567-570.|
|2||Amendola MA, Bree RL, Pollack H, et al. Small renal cell carcinomas: resolving a diagnostic dilemma. Radiology 1988; 166:637-641.|
|3||Aso Y, Homma Y. A survey on incidental renal cell carcinoma in Japan. J Urol 1992; 147: 340-343.|
|4||Bosniak MA. Angiomyolipoma (hamartoma) of the kidney; a pre-operative diagnosis is possible in virtually every case. Urol Radiol 1981; 3:135-142.|
|5||Bosniak MA. The current radiological approach to renal cysts. Radiology 1986; 158:1-10.|
|6||Choyke PL, Glenn GM, Walther MM, Patronas NJ, Linehan WM, Zbar B. Von Hippel Lindau disease: Genetic, clinical and imaging features, Radiology 1995; 194:629-642.|
|7||Curry NS, Brock JG, Metcalf JS. Sens MA. Hyperdense renal mass: unusual CT appearance of a benign renal cyst. Urol Radiol 1982; 4:33-36.|
|8||Curry NS, Schabel SI, Betsill WL Jr. Small renal neoplasms: diagnostic imaging, pathologic features, and clinical course. Radiology 1986; 158:113-117.|
|9||Curry NS. Small renal masses (lesions smaller than 3 cm): Imaging evaluation and management. AJR 1995; 164:355368.|
|10||Dalla-Palma L, Pozzi-Mucelli F, Di Donna A. Cystic renal tumors: US & CT findings. Urol Radiol 1990; 12:67-73.|
|11||Davidson AJ, Hayes WS, Hartman DS, McCarthy WF, Davis CJ. Renal oncocytoma and carcinoma: failure of differentiation with CT. Radiology 1993; 186:693-696.|
|12||Dinsmore BJ, Pollack HM, Banner MP. Calcified transitional cell carcinoma of the renal pelvis. Radiology 1988; 167:401404.|
|13||Dunnick NR, Korobkin M. Clark WM. CT demonstration of hyperdense renal carcinoma. J Comput Assist Tomogr 1984; 8:1023-1024.|
|14||Ferris RA, Kirschner LP, Mero JH, McCabe DJ, Moss ML. Computed tomography in the evaluation of inferior vena caval obstruction. Radiology 1979; 130:7-10.|
|15||Fishman MC, Pollack HM, Arger PH, Banner MD. High protein content: another cause of CT hyperdense benign renal cysts. J Comput Assist Tomogr 1983; 7:1103-1106.|
|16||Fowler JE, PerkinsT. Presentation, diagnosis and treatment of renal abscesses; 1972-1988. J Urol 1994; 151:847-851.|
|17||Gatewood OMB, Goldman SM, Marshal FF, Siegelman SS. Computerized tomography in the diagnosis of transitional cell carcinoma of the kidney. J Urol 1982; 127:876-887.|
|18||Gibson RJ, Meanock Cl, Torrie EPH, Walker TM. An assessment of Gd-DTPA as a CT contrast agent in the renal tract. Clin Radiol 1993; 47:278-279.|
|19||Hartman DS, Davis CJ, Sanders RC, Johns TT. Smirniotopoulos J, Goldman SM. The multiloculated renal mass: Considerations and differential features. Radiographics 1987; 7:29-52.|
|20||Hartman DS, Weatherby E III, Laskin WB, Brody JM, Corse W, Baluch JD. Cystic renal cell carcinoma: CT findings simulating a benign hyperdense cyst. AJR 1992; 159:1235-1237.|
|21||Higashihara E, Aso Y, Shimazaki J, Ito H, Koiso K, Sakai O. Clinical aspects of polycystic kidney disease. J Urol 1992; 147:329-332.|
|22||Johnson CD, Dunnick NR, Cohan RH, Illescas FF. Renal adenocarcinoma: CT findings of 100 tumors. AJR 1987; 148:59-63.|
|23||Kabala JE, Gillatt DA, Persad RA, Penry JB, Gingell JC, Chadwick D. Magnetic resonance imaging in the staging of renal cell carcinoma. Br J Radiol 1991; 64:683-689.|
|24||Kallman DA, King BF, Hattery RR, et al. Renal vein and inferior vena cava tumor thrombus in renal cell carcinoma: CT, US, MRI, and venacavography. J Comput Assist Tomogr 1992 ;16:240-247.|
|25||Levine E, Grantham JJ, High-density renal cysts in autosomal dominant polycystic kidney disease demonstrated by CT. Radiology 1985; 154:477-482.|
|26||Madewell JE, Goldman SM, Davis CJ Jr, Hartman DS, Feigin DS, Lichtenstein JE. Multilocular cystic nephroma: a radiographic pathologic correlation of 58 patients. Radiology 1983; 146:309-321.|
|27||McClennan BL. Computed tomography in the diagnosis and staging of renal cell carcinoma. Semin Urol 1985;3:111-131.|
|28||McMillin KI, Gross BH. CT demonstration of peripelvic and periureteral non-Hodgkin lymphoma. AJR 1985;144: 945-946.|
|29||Michaeli J, Mongle P, Perlberg S, Heiman S, Caine M. Emphysematous pyelonephritis. J Urol 1984; 131:203-208.|
|30||Mitty HA. CT for diagnosis and management of urinary extravasation. AJR 1980; 134:497-501.|
|31||Munechika H, Kushihashi T, Gokan T, Hasimoto T,Higaki Y, Ogawa Y. A renal cell carcinoma extending into the renal pelvis simulating transitional cell carcinoma. Urol Radiol 1990;12:11-14.|
|32||Reznek RH, Mootoosamy I, Webb JAW, Richards MA. CT in renal and perirenal lymphoma: a further look. Cllin Radiol 1990; 42:233-238.|
|33||Robson CJ. The results of radical nephrectomy for renal cell carcinoma. J. Urol 1969; 101:297-301.|
|34||Rosenberg ER, Korobkin M, Foster W, Silverman PM, Bowie JD, Dunnick NR. The significance of septations in a renal cyst. AJR 1985; 144:593-596.|
|35||Segal AJ, Spitzer RM. Pseudo thick-walled renal cyst by CT. AJR 1979; 132:827-828.|
|36||Soulen MC, Fishman EK, Goldman SM, Gatewood OMB. Bacterial renal infection: role of CT. Radiology 1989;171:703-707.|
|37||Takao R, Amamoto Y, Matsunaga N. et al. Computed tomography of multicystic kidney. J. Comput Assist Tomogr 1980;4:548-549.|
|38||Vas W, Salimi Z, Tang Barton P, Vargas F. Sidarthan AS. Computed tomography and ultrasound demonstration of squamous cell carcinoma. Comput tomogr 1985; 9:87-89.|
|39||Warshauer DM, McCarthy SM, Street L, et al. Detection of renal masses: Sensitivities and specificitis of excretory urography / linear tomography, US & CT. Radiology 1988;169:363-365.|
|40||Wimbish JK, Sanders MM, Samuels BI, Francis IR. Squamous cell carcinoma of the renal pelvis: case report. Urol Radiol 1983; 5:267-269.|