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From the RSNA Refresher Courses

A Practical Approach to the Cystic Renal Mass¹

¹ From the Department of Radiology, Milton S. Hershey Medical Center, Penn State University School of Medicine, HO66, 500 University Dr, Hershey, PA 17033 (D.S.H.); the Department of Radiology, Clinical Center, National Institutes of Health, Bethesda, Md (P.L.C.); and the Department of Radiology, Emory University School of Medicine, Atlanta, Ga (M.S.H.). Presented as a refresher course at the 2003 RSNA scientific assembly. Received March 29, 2004; revision requested April 28 and received May 14; accepted May 25. All authors have no financial relationships to disclose. Address correspondence to D.S.H. (e-mail: dhartman@psu.edu).

View larger version (96K): [in a new window]   Figure 1a.  Similarity of the gross features of complicated renal cysts and cystic renal cell carcinoma. Photographs show a hemorrhagic cyst (a) and cystic renal cell carcinoma (b). Both cystic lesions (arrows) contain fluid, which is described as resembling motor oil. Both have a thick, irregular cyst wall. Definitive diagnosis is dependent on microscopic examination.

View larger version (120K): [in a new window]   Figure 1b.  Similarity of the gross features of complicated renal cysts and cystic renal cell carcinoma. Photographs show a hemorrhagic cyst (a) and cystic renal cell carcinoma (b). Both cystic lesions (arrows) contain fluid, which is described as resembling motor oil. Both have a thick, irregular cyst wall. Definitive diagnosis is dependent on microscopic examination.

View larger version (78K): [in a new window]   Figure 2a.  Use of MR imaging to evaluate the relative enhancement of a hyperattenuating and high-signal-intensity cyst in a 53-year-old asymptomatic man. CT demonstrated a 3-cm-diameter hyperattenuating (40 HU) lesion in the left kidney. (a-c) Serial precontrast (a), corticomedullary phase (b), and nephrographic phase (c) T1-weighted breath-hold gradient-echo MR images show no significant enhancement of the lesion, with relative signal intensities of 138, 138, and 139, respectively. (d) Longitudinal sonogram also shows that the mass is cystic.

View larger version (87K): [in a new window]   Figure 2b.  Use of MR imaging to evaluate the relative enhancement of a hyperattenuating and high-signal-intensity cyst in a 53-year-old asymptomatic man. CT demonstrated a 3-cm-diameter hyperattenuating (40 HU) lesion in the left kidney. (a-c) Serial precontrast (a), corticomedullary phase (b), and nephrographic phase (c) T1-weighted breath-hold gradient-echo MR images show no significant enhancement of the lesion, with relative signal intensities of 138, 138, and 139, respectively. (d) Longitudinal sonogram also shows that the mass is cystic.

View larger version (102K): [in a new window]   Figure 2c.  Use of MR imaging to evaluate the relative enhancement of a hyperattenuating and high-signal-intensity cyst in a 53-year-old asymptomatic man. CT demonstrated a 3-cm-diameter hyperattenuating (40 HU) lesion in the left kidney. (a-c) Serial precontrast (a), corticomedullary phase (b), and nephrographic phase (c) T1-weighted breath-hold gradient-echo MR images show no significant enhancement of the lesion, with relative signal intensities of 138, 138, and 139, respectively. (d) Longitudinal sonogram also shows that the mass is cystic.

View larger version (125K): [in a new window]   Figure 2d.  Use of MR imaging to evaluate the relative enhancement of a hyperattenuating and high-signal-intensity cyst in a 53-year-old asymptomatic man. CT demonstrated a 3-cm-diameter hyperattenuating (40 HU) lesion in the left kidney. (a-c) Serial precontrast (a), corticomedullary phase (b), and nephrographic phase (c) T1-weighted breath-hold gradient-echo MR images show no significant enhancement of the lesion, with relative signal intensities of 138, 138, and 139, respectively. (d) Longitudinal sonogram also shows that the mass is cystic.

View larger version (86K): [in a new window]   Figure 3a.  Benign calcification in a 50-year-old man with abdominal pain. (a) Axial unenhanced CT scan shows a cystic lesion in the left kidney. The dependent calcification was freely moveable with change of position and represents milk of calcium. There is a second small fleck of calcium in the cyst wall at the 10-o’clock position. (b) Contrast-enhanced CT scan shows no irregularity, nodularity, or enhancement of the cyst wall.

View larger version (126K): [in a new window]   Figure 3b.  Benign calcification in a 50-year-old man with abdominal pain. (a) Axial unenhanced CT scan shows a cystic lesion in the left kidney. The dependent calcification was freely moveable with change of position and represents milk of calcium. There is a second small fleck of calcium in the cyst wall at the 10-o’clock position. (b) Contrast-enhanced CT scan shows no irregularity, nodularity, or enhancement of the cyst wall.

View larger version (108K): [in a new window]   Figure 4a.  Surgical calcification in a 67-year-old asymptomatic man. (a) Axial unenhanced CT scan shows an irregular nodular calcification (large arrow) in a cystic mass of the left kidney. In addition, there is septal calcification (small arrow) and nephrolithiasis. (b) Contrast-enhanced CT scan shows focal nodular enhancement (arrow) adjacent to the irregular calcification.

View larger version (108K): [in a new window]   Figure 4b.  Surgical calcification in a 67-year-old asymptomatic man. (a) Axial unenhanced CT scan shows an irregular nodular calcification (large arrow) in a cystic mass of the left kidney. In addition, there is septal calcification (small arrow) and nephrolithiasis. (b) Contrast-enhanced CT scan shows focal nodular enhancement (arrow) adjacent to the irregular calcification.

View larger version (101K): [in a new window]   Figure 5a.  Follow-up calcification. Unenhanced (a) and contrast-enhanced (b) CT scans show an incidentally detected calcified mass. Despite the density of the calcification, the lesion does not enhance after intravenous administration of contrast material. This lesion could have been managed with follow-up; however, surgery was performed and revealed a heavily calcified and septated cystic lesion with no evidence of tumor.

View larger version (125K): [in a new window]   Figure 5b.  Follow-up calcification. Unenhanced (a) and contrast-enhanced (b) CT scans show an incidentally detected calcified mass. Despite the density of the calcification, the lesion does not enhance after intravenous administration of contrast material. This lesion could have been managed with follow-up; however, surgery was performed and revealed a heavily calcified and septated cystic lesion with no evidence of tumor.

View larger version (122K): [in a new window]   Figure 6a.  Hyperattenuating, septated benign cyst in an 84-year-old man with mild renal insufficiency. (a) Unenhanced CT scan shows a 4-cm-diameter lesion with high attenuation (68 HU). (b) Contrast-enhanced CT scan shows no significant enhancement (70 HU). (c) Longitudinal sonogram shows that the lesion is cystic and has one delicate septation (arrow). Although this lesion meets the criteria for a benign hyperattenuating cyst, some recommend follow-up of all hyperattenuating lesions larger than 3 cm in diameter (6).

View larger version (118K): [in a new window]   Figure 6b.  Hyperattenuating, septated benign cyst in an 84-year-old man with mild renal insufficiency. (a) Unenhanced CT scan shows a 4-cm-diameter lesion with high attenuation (68 HU). (b) Contrast-enhanced CT scan shows no significant enhancement (70 HU). (c) Longitudinal sonogram shows that the lesion is cystic and has one delicate septation (arrow). Although this lesion meets the criteria for a benign hyperattenuating cyst, some recommend follow-up of all hyperattenuating lesions larger than 3 cm in diameter (6).

View larger version (132K): [in a new window]   Figure 6c.  Hyperattenuating, septated benign cyst in an 84-year-old man with mild renal insufficiency. (a) Unenhanced CT scan shows a 4-cm-diameter lesion with high attenuation (68 HU). (b) Contrast-enhanced CT scan shows no significant enhancement (70 HU). (c) Longitudinal sonogram shows that the lesion is cystic and has one delicate septation (arrow). Although this lesion meets the criteria for a benign hyperattenuating cyst, some recommend follow-up of all hyperattenuating lesions larger than 3 cm in diameter (6).

View larger version (119K): [in a new window]   Figure 7a.  Surgical hyperattenuating mass in a 63-year-old asymptomatic man. (a-c) Unenhanced (a), nephrographic phase (b), and excretory phase (c) CT scans show a well-defined, homogeneous, 3-cm-diameter lesion. The region of interest for measurement was in the center of the mass. The mass enhances 13 HU on the nephrographic phase image (b), then de-enhances 7 HU on the excretory phase image (c). If nephrographic phase images had not been obtained, the apparent enhancement would have been 6 HU. (d) Longitudinal sonogram shows that the lesion (arrows) is solid. (e) Gross photograph of the excised mass shows a well-defined 3-cm-diameter mass, which was a papillary renal cell carcinoma.

View larger version (124K): [in a new window]   Figure 7b.  Surgical hyperattenuating mass in a 63-year-old asymptomatic man. (a-c) Unenhanced (a), nephrographic phase (b), and excretory phase (c) CT scans show a well-defined, homogeneous, 3-cm-diameter lesion. The region of interest for measurement was in the center of the mass. The mass enhances 13 HU on the nephrographic phase image (b), then de-enhances 7 HU on the excretory phase image (c). If nephrographic phase images had not been obtained, the apparent enhancement would have been 6 HU. (d) Longitudinal sonogram shows that the lesion (arrows) is solid. (e) Gross photograph of the excised mass shows a well-defined 3-cm-diameter mass, which was a papillary renal cell carcinoma.

View larger version (131K): [in a new window]   Figure 7c.  Surgical hyperattenuating mass in a 63-year-old asymptomatic man. (a-c) Unenhanced (a), nephrographic phase (b), and excretory phase (c) CT scans show a well-defined, homogeneous, 3-cm-diameter lesion. The region of interest for measurement was in the center of the mass. The mass enhances 13 HU on the nephrographic phase image (b), then de-enhances 7 HU on the excretory phase image (c). If nephrographic phase images had not been obtained, the apparent enhancement would have been 6 HU. (d) Longitudinal sonogram shows that the lesion (arrows) is solid. (e) Gross photograph of the excised mass shows a well-defined 3-cm-diameter mass, which was a papillary renal cell carcinoma.

View larger version (159K): [in a new window]   Figure 7d.  Surgical hyperattenuating mass in a 63-year-old asymptomatic man. (a-c) Unenhanced (a), nephrographic phase (b), and excretory phase (c) CT scans show a well-defined, homogeneous, 3-cm-diameter lesion. The region of interest for measurement was in the center of the mass. The mass enhances 13 HU on the nephrographic phase image (b), then de-enhances 7 HU on the excretory phase image (c). If nephrographic phase images had not been obtained, the apparent enhancement would have been 6 HU. (d) Longitudinal sonogram shows that the lesion (arrows) is solid. (e) Gross photograph of the excised mass shows a well-defined 3-cm-diameter mass, which was a papillary renal cell carcinoma.

View larger version (143K): [in a new window]   Figure 7e.  Surgical hyperattenuating mass in a 63-year-old asymptomatic man. (a-c) Unenhanced (a), nephrographic phase (b), and excretory phase (c) CT scans show a well-defined, homogeneous, 3-cm-diameter lesion. The region of interest for measurement was in the center of the mass. The mass enhances 13 HU on the nephrographic phase image (b), then de-enhances 7 HU on the excretory phase image (c). If nephrographic phase images had not been obtained, the apparent enhancement would have been 6 HU. (d) Longitudinal sonogram shows that the lesion (arrows) is solid. (e) Gross photograph of the excised mass shows a well-defined 3-cm-diameter mass, which was a papillary renal cell carcinoma.

View larger version (151K): [in a new window]   Figure 8.  Benign septation in a 52-year-old woman with right lower quadrant pain. CT scan shows an 8-cm-diameter cystic lesion with a thin, partial septation (arrow).

View larger version (129K): [in a new window]   Figure 9.  Surgical septation in a 58-year-old man with an incidentally discovered cystic lesion of the right kidney. CT scan shows a thick, irregular, enhancing septation (nonenhanced scan not shown). A low-grade renal carcinoma was diagnosed at microscopic evaluation.

View larger version (130K): [in a new window]   Figure 10a.  Septated or multiloculated cystic lesion in a 60-year-old woman being evaluated for an abnormal uterus. Axial CT scan (a) and coronal reformatted image (b) show a well-defined, 3-cm-diameter cystic mass in the upper pole of the left kidney. The lesion appears to contain three or four septations, which are smooth without large nodular elements. At surgery, a multiloculated renal cell carcinoma was removed.

View larger version (132K): [in a new window]   Figure 10b.  Septated or multiloculated cystic lesion in a 60-year-old woman being evaluated for an abnormal uterus. Axial CT scan (a) and coronal reformatted image (b) show a well-defined, 3-cm-diameter cystic mass in the upper pole of the left kidney. The lesion appears to contain three or four septations, which are smooth without large nodular elements. At surgery, a multiloculated renal cell carcinoma was removed.

View larger version (166K): [in a new window]   Figure 11a.  Multiloculated renal mass evaluated with different imaging modalities. (a) Longitudinal sonogram of a 42-year-old man shows a multiloculated mass, which was diagnosed as renal cell carcinoma. GB = gallbladder. (b) Axial T2-weighted MR image of the same patient shows the 11-cm-diameter, sharply marginated, multiloculated renal cell carcinoma. (c) Multilocular cystic nephroma in a 49-year-old woman in whom a renal cyst was aspirated 20 years earlier. CT scan shows an 11-cm-diameter multiloculated mass. Note that a portion of the mass projects into the renal pelvis (arrow), a feature suggestive of multilocular cystic nephroma.

View larger version (157K): [in a new window]   Figure 11b.  Multiloculated renal mass evaluated with different imaging modalities. (a) Longitudinal sonogram of a 42-year-old man shows a multiloculated mass, which was diagnosed as renal cell carcinoma. GB = gallbladder. (b) Axial T2-weighted MR image of the same patient shows the 11-cm-diameter, sharply marginated, multiloculated renal cell carcinoma. (c) Multilocular cystic nephroma in a 49-year-old woman in whom a renal cyst was aspirated 20 years earlier. CT scan shows an 11-cm-diameter multiloculated mass. Note that a portion of the mass projects into the renal pelvis (arrow), a feature suggestive of multilocular cystic nephroma.

View larger version (156K): [in a new window]   Figure 11c.  Multiloculated renal mass evaluated with different imaging modalities. (a) Longitudinal sonogram of a 42-year-old man shows a multiloculated mass, which was diagnosed as renal cell carcinoma. GB = gallbladder. (b) Axial T2-weighted MR image of the same patient shows the 11-cm-diameter, sharply marginated, multiloculated renal cell carcinoma. (c) Multilocular cystic nephroma in a 49-year-old woman in whom a renal cyst was aspirated 20 years earlier. CT scan shows an 11-cm-diameter multiloculated mass. Note that a portion of the mass projects into the renal pelvis (arrow), a feature suggestive of multilocular cystic nephroma.

View larger version (126K): [in a new window]   Figure 12a.  Localized cystic disease of the kidney in a 43-year-old man being evaluated for abdominal trauma. The localized cystic disease was an incidental finding. Axial contrast-enhanced CT scans show a cluster of cysts separated by normal enhancing renal parenchyma in the upper pole of the right kidney. There is no pseudocapsule surrounding the cysts. Note that the small cyst at the 6-o’clock position (arrow in a) is clearly separate from the aggregate of cysts.

View larger version (109K): [in a new window]   Figure 12b.  Localized cystic disease of the kidney in a 43-year-old man being evaluated for abdominal trauma. The localized cystic disease was an incidental finding. Axial contrast-enhanced CT scans show a cluster of cysts separated by normal enhancing renal parenchyma in the upper pole of the right kidney. There is no pseudocapsule surrounding the cysts. Note that the small cyst at the 6-o’clock position (arrow in a) is clearly separate from the aggregate of cysts.

View larger version (181K): [in a new window]   Figure 13a.  Cystic renal cell carcinoma in a 71-year-old man undergoing follow-up for esophageal carcinoma. (a) Unenhanced CT scan shows an appearance suggestive of a thick wall. (b) Contrast-enhanced CT scan clearly shows the thick wall (arrow).

View larger version (164K): [in a new window]   Figure 13b.  Cystic renal cell carcinoma in a 71-year-old man undergoing follow-up for esophageal carcinoma. (a) Unenhanced CT scan shows an appearance suggestive of a thick wall. (b) Contrast-enhanced CT scan clearly shows the thick wall (arrow).

View larger version (164K): [in a new window]   Figure 14.  Cystic inflammatory mass in a 26-year-old woman with abdominal pain. Contrast-enhanced CT scan shows a thick-walled (arrows) cystic mass of the left kidney. Note that the cyst wall enhances less than the normal renal parenchyma but more than the cyst fluid.

View larger version (153K): [in a new window]   Figure 15a.  Cyst with apparent wall thickening due to normal parenchyma in an asymptomatic 68-year-old woman. (a) Contrast-enhanced CT scan shows a cystic mass with apparent wall thickening. (b) CT scan obtained immediately superior to a shows a fluid-filled mass without a perceptible wall. (c) Coronal MR image shows that the apparent wall thickening is due to the normal parenchymal beak. Lines A and B indicate the respective levels where a and b were obtained.

View larger version (152K): [in a new window]   Figure 15b.  Cyst with apparent wall thickening due to normal parenchyma in an asymptomatic 68-year-old woman. (a) Contrast-enhanced CT scan shows a cystic mass with apparent wall thickening. (b) CT scan obtained immediately superior to a shows a fluid-filled mass without a perceptible wall. (c) Coronal MR image shows that the apparent wall thickening is due to the normal parenchymal beak. Lines A and B indicate the respective levels where a and b were obtained.

View larger version (136K): [in a new window]   Figure 15c.  Cyst with apparent wall thickening due to normal parenchyma in an asymptomatic 68-year-old woman. (a) Contrast-enhanced CT scan shows a cystic mass with apparent wall thickening. (b) CT scan obtained immediately superior to a shows a fluid-filled mass without a perceptible wall. (c) Coronal MR image shows that the apparent wall thickening is due to the normal parenchymal beak. Lines A and B indicate the respective levels where a and b were obtained.

View larger version (147K): [in a new window]   Figure 16a.  Enhancement of a traumatic hemorrhagic cyst in a 43-year-old tae kwon do enthusiast who was kicked in the left side 6 months earlier. (a) Unenhanced CT scan shows a multiloculated renal lesion with a perinephric component. (b) Contrast-enhanced CT scan shows that the lesion is thick walled with a markedly enhancing nodule (arrow). At surgery, a posttraumatic, intrarenal and perirenal, partially liquefied hematoma simulating a cyst was found. The enhancing nodule proved to be residual normally functioning renal tissue.

View larger version (159K): [in a new window]   Figure 16b.  Enhancement of a traumatic hemorrhagic cyst in a 43-year-old tae kwon do enthusiast who was kicked in the left side 6 months earlier. (a) Unenhanced CT scan shows a multiloculated renal lesion with a perinephric component. (b) Contrast-enhanced CT scan shows that the lesion is thick walled with a markedly enhancing nodule (arrow). At surgery, a posttraumatic, intrarenal and perirenal, partially liquefied hematoma simulating a cyst was found. The enhancing nodule proved to be residual normally functioning renal tissue.

View larger version (177K): [in a new window]   Figure 17a.  Discordant imaging findings in an 82-year-old man with a 13-cm-diameter cystic mass in the upper renal pole. (a) Unenhanced CT scan obtained through the mass shows two irregular nodular regions of calcification (arrows). (b) Contrast-enhanced CT scan obtained at the same level shows no enhancement near the calcifications, the wall, or the center of the mass. There were no suspicious areas on other scans. On the basis of the CT findings, the mass could have been managed with follow-up. (c) Longitudinal sonogram obtained through the mass shows that the lesion (arrows) is complex and solid appearing with several central, irregular hypoechoic areas. The mass was excised and diagnosed as a "burned-out" renal cell carcinoma without viable tumor cells. K = kidney.

View larger version (167K): [in a new window]   Figure 17b.  Discordant imaging findings in an 82-year-old man with a 13-cm-diameter cystic mass in the upper renal pole. (a) Unenhanced CT scan obtained through the mass shows two irregular nodular regions of calcification (arrows). (b) Contrast-enhanced CT scan obtained at the same level shows no enhancement near the calcifications, the wall, or the center of the mass. There were no suspicious areas on other scans. On the basis of the CT findings, the mass could have been managed with follow-up. (c) Longitudinal sonogram obtained through the mass shows that the lesion (arrows) is complex and solid appearing with several central, irregular hypoechoic areas. The mass was excised and diagnosed as a "burned-out" renal cell carcinoma without viable tumor cells. K = kidney.

View larger version (120K): [in a new window]   Figure 17c.  Discordant imaging findings in an 82-year-old man with a 13-cm-diameter cystic mass in the upper renal pole. (a) Unenhanced CT scan obtained through the mass shows two irregular nodular regions of calcification (arrows). (b) Contrast-enhanced CT scan obtained at the same level shows no enhancement near the calcifications, the wall, or the center of the mass. There were no suspicious areas on other scans. On the basis of the CT findings, the mass could have been managed with follow-up. (c) Longitudinal sonogram obtained through the mass shows that the lesion (arrows) is complex and solid appearing with several central, irregular hypoechoic areas. The mass was excised and diagnosed as a "burned-out" renal cell carcinoma without viable tumor cells. K = kidney.