- Email: [email protected]
Chyluria After Radiofrequency Ablation of Renal Tumors
CLINICAL STUDY
Chyluria After Radiofrequency Ablation of Renal Tumors Harmeet Kaur, MD, Surena F. Matin, MD, Sanaz Javadi, MD, Valen E. Johnson, PhD, Haesun Choi, MD, Carl Sandler, MD, and Kamran Ahrar, MD
ABSTRACT Purpose: To assess the incidence of chyluria after radiofrequency (RF) ablation of renal tumors and attempt to identify predictors of this phenomenon. Materials and Methods: Over a 3-year period, 62 consecutive patients with renal tumors were treated by percutaneous computed tomography (CT)– guided or laparoscopic RF ablation, of which 41 underwent at least three posttreatment CT studies and were evaluated in this study. Three radiologists reviewed the pretreatment and posttreatment CT images for the presence or absence of fat-fluid levels in the bladder, the location of the tumor, and the size of the postablation defect. A logistic regression model was used to assess whether ablation defect size or tumor location predicted chyluria. Results: Chyluria was detected at a mean time of 44.5 weeks in 17 (41%) of 41 patients with renal tumors treated by RF ablation. A pretreatment biopsy specimen showed renal cell carcinoma in 74%. Mean tumor size was 2.77 cm, and mean initial ablation size was 4.2 cm. Chyluria persisted in seven patients. Zone of ablation defect size and tumor location were not significant predictors of chyluria (P ⫽ .64 and P ⫽ .42). Mean follow-up was 77 weeks. Conclusions: Chyluria is a common and asymptomatic finding in a significant proportion of patients undergoing RF ablation for renal tumors. Tumor location and zone of ablation defect size were not predictors of chyluria. The presence of a fat-fluid level should not be mistaken for an air-fluid level.
Chyluria, the passage of lymphatic fluid into the urine, results from the development of a communication between lymphatic channels and the pelvicalyceal system (1). The appearance on computed tomography (CT) is of a fat-fluid level in the urinary bladder that can be mistaken for an air-fluid level. Chyluria is most commonly seen secondary to parasitic infections such as Wuchereria bancrofti, retroperitoneal malignancies, and chronic infections such as tuberculosis (1). Miller et al (2) reported chyluria in 4 of 125 patients who had undergone partial nephrectomy for renal tumors. We encountered chyluria in a patient who had undergone radiofrequency (RF) ablation for renal call carcinoma. This case prompted us to review our experience
From the Departments of Diagnostic Radiology (H.K, S.J., H.C., C.S., K.A.), Urology (S.F.M.), and Biostatistics (V.E.J.), The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 1373, Houston, TX 77030. Received November 17, 2010; final revision received February 9, 2011; accepted February 14, 2011. Address correspondence to S.F.M.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2011 J Vasc Interv Radiol 2011; 22:924 –927 DOI: 10.1016/j.jvir.2011.02.014
with RF ablation of renal cell carcinoma to determine the incidence of chyluria and possible predictive factors.
MATERIALS AND METHODS Patients We retrospectively reviewed the records of 62 consecutive patients with solitary renal tumors who had undergone RF ablation at our institution over a 3-year period. Our technique of CT-guided and laparoscopic RF ablation has been previously described (3). A minimum of three posttreatment CT scans was required to be included in this review. Patients undergoing ablative therapy at our institution undergo a systematic and regimented follow-up schedule based on published recommendations (4). Patients are asked to return 4 – 6 weeks after ablation, then every 6 months for at least 2 years, then annually or biannually thereafter depending on imaging findings (4). A history and physical examination, in addition to laboratory serum and urine tests, is documented during these follow-up visits along with the required abdominal axial imaging. Patients with a history of renal cell carcinoma also undergo chest imaging annually as part of the standard follow-up for stage
Volume 22 䡲 Number 7 䡲 July 䡲 2011
T1 tumors. This retrospective study was performed under approval by our institutional review board.
Imaging Technique CT scans were obtained on a multidetector scanner (LightSpeed 16, GE Healthcare, Milwaukee, Wisconsin). Precontrast scans through the abdomen were obtained using 5-mm contiguous cuts, and 125 mL of Optiray 350 (Mallinckrodt, Hazelwood, Missouri) was injected at a rate of 5 mL/s. Postcontrast scans were obtained at 25 seconds, 60 seconds, 110 seconds, and 180 seconds and through the pelvis at 85 seconds and 180 seconds, using 5-mm contiguous cuts.
Data Collection Pretherapy CT scans and all available CT scans after RF ablation were reviewed for the presence of chyluria by three radiologists (C.S., H.K., and K.A.). Chyluria was defined as the presence of a fat-fluid level in the urinary bladder. The presence of fat was confirmed by region-of-interest measurements or use of lung windows to distinguish fat from air. Pretreatment scans were reviewed for the location of the renal tumors. Tumor locations were classified as exophytic, parenchymal, central, and mixed on the basis of definitions in the interventional radiology literature (5). The initial posttreatment scans after RF ablation were reviewed to determine the size of the ablation defect. These scans were obtained a mean of 4.5 weeks (range 2–12 weeks) after ablation therapy. The maximum diameter of the ablation defect within the kidney was measured on the final set of delayed images; posttreatment changes in the perinephric fat were not included in the measurements. Three radiologists reviewed the CT scans, and consensus was reached through discussion on the extent of postablation change. Patient charts were reviewed for any metabolic, urinary, or symptom-related abnormalities potentially relevant to chyluria.
Statistical Analysis A logistic regression model was used to assess whether tumor location or maximum zone of ablation defect diameter predicted occurrence of chyluria. Maximum likelihood procedures were used to estimate the regression coefficients of maximum ablation defect diameter and the four-level factor representing tumor location. Statistical tests were performed using open source software (6).
RESULTS Among 62 consecutive patients who had RF ablation for renal tumors during the period reviewed, 41 were identified who had at least three CT scans after treatment. Demographic, tumor, treatment, and follow-up data are summarized in the Table. Pretreatment CT scans were available in 37 patients; none of these patients had evidence of chyluria before therapy. The remainder had pretreatment imaging that either did not include the pelvis or was not archived into our
925
Table. Demographic, Tumor, and RF Ablation Summary Data for Renal Tumors During the Study Period Variable Age (y) Male Female Biopsy No Yes Renal cell carcinoma Benign Nondiagnostic Tumor size (cm) Tumor depth Exophytic Central Mixed Parenchymal No. tumors treated 1 2 3 Initial ablation size (cm) Approach Percutaneous Laparoscopic Time to detection of chyluria (wk) Follow-up time (wk)
No. 41 25 16 2 39 29 5 5 46
Mean 67.8
Range 27–87
% 61 39
92.7 74.4 12.8 12.8 2.7
1.2–4.8
24 2 16 4
52.2 4.3 34.8 8.7
37 3 1 41
90.2 7.3 2.5 4.2
2.2–7.0
30 11
73.2 26.8 44.5
3.0–84.0
77
32–152
electronic medical record and was unavailable for retrospective review. Of the 41 patients, 17 (41%) were found to have chyluria on at least one posttreatment CT scan. Chyluria was observed 3 weeks to 20 months after ablation. The mean time of detection was 11 months after ablation. In 4 of the 17 patients, chyluria was a transient finding observed on one or more CT scans and resolving on a subsequent scan. In seven patients, chyluria persisted on two or more CT scans (Fig 1a– c) obtained over 7–12 months after detection (mean 10 months). In the remaining six patients, chyluria was noted on the last available scans. There were 17 renal masses in the chyluria group; pretreatment scans were available for 14 of these. Seven lesions (50%) were exophytic, three (21%) were parenchymal, and four (29%) were central in location. Among the 11 patients with chyluria, 10 had evaluable pretreatment studies. Six lesions (60%) were exophytic, one (10%) was parenchymal, and three (30 %) were central. No mixed lesions were identified. There was no statistically significant effect of tumor location (P ⫽ .42) on the presence or absence of chyluria. There was also no significant effect of maximum ablation defect diameter (P ⫽ .64) for predicting occurrence of chyluria. Review of patient medical charts with chyluria did not reveal any specific signs. symptoms, or laboratory abnormal-
926 䡲 Chyluria After RF Ablation of Renal Tumors
Kaur et al 䡲 JVIR
Figure 1. (a) Axial contrast-enhanced CT scan through the pelvis in a 78-year-old man with a solitary renal cell carcinoma. A fat-fluid level was detected 17 months after RF ablation. (b) CT scan after 24 months shows a persistent and greater amount of chyluria. (c) Use of a lung window through the pelvis confirms the absence of air in the bladder.
Figure 2. Photograph taken during cystoscopy in a 67-year-old man after RF ablation showing multiple fat globules. The indication for cystoscopy was microhematuria on urinalysis. The urinalysis was otherwise negative. (Available in color online at www.jvir.org.)
ities attributable to chyluria. Chyluria was seen during cystoscopy in patients who were incidentally evaluated for other conditions, such as work-up of microhematuria found during their routine follow-up (Fig 2). Routine urinalysis dipstick tests are not designed to detect the presence of fat or chyle.
DISCUSSION RF ablation for renal masses is used primarily to treat patients with multiple comorbidities, advanced age, prior nephrectomy or partial nephrectomy, and multifocal renal
cell carcinoma. The reported incidence of complications ranges from 7%–18% (3,5). Complications are usually minor, requiring minimal or no intervention. To our knowledge, there is a single report of two cases of chyluria after RF ablation (7). In a retrospective review of 125 patients with renal tumors, Miller et al (2) reported 4 asymptomatic patients who developed chyluria after partial nephrectomy. In each case, chyluria manifested as a fat-fluid level in the bladder detected by CT. The authors speculated that the surgical procedure created a communication between the collecting system and lymphatic vessels of the kidney. The incidence of chyluria was much higher in our group of patients (17 of 41 [41%]) than in the patients with partial nephrectomy reported by Miller et al (2). Although these differences may be explained by study design or patient variables, it hypothetically may also be related to the nature of tissue damage caused by RF ablation permitting the fistulization of lymphatics in the zone of ablation into the urinary collecting system. Our study is limited by retrospective bias. This study design did not allow use of specific, nonroutine testing of urine for the presence of chyle or fat. Very subtle symptoms or signs may have been present and were not reflected in the patient medical record; however, given the available literature on chyluria showing this phenomenon to be largely asymptomatic, we think that is unlikely. It is also possible that chyluria is an intermittent event that was erroneously characterized as persistent but was detected by chance during every follow-up imaging examination. Regarding treatment, most of the literature is centered on chyluria resulting from parasitic infections. In these circumstances, chyluria has been described as having little effect on the general health of patients. The condition may remit spontaneously, and treatment is reserved for the few patients with symptomatic chyluria. The indications for therapy are weight loss, hypoproteinemia, anemia, anasarca, clot retention, and altered immune status. Treatment for chyluria of renal origin includes surgery to disconnect lymphorenal connections or use of glues for ureteral occlu-
Volume 22 䡲 Number 7 䡲 July 䡲 2011
sion (8 –10). However, in all of our cases, the chyluria seemed to be clinically silent. We do not believe the occurrence of chyluria to be clinically relevant at this time, and it does not seem to warrant intervention. The presence of chyluria in 41% of our patients undergoing RF ablation is an important observation that may have implications for accurate radiologic interpretation as well as a finding that that may prove informative with longer follow-up or to help avoid a misdiagnosis in patients undergoing scans for other conditions. The bladder fat-fluid interface may be confused in some cases for air in the bladder. The two can be easily differentiated by switching to lung windows or placing a region of interest over the fat level.
REFERENCES 1. Koehler R, Chiang T, Lin T. Lymphography in chyluria. AJR Am J Roentgenol 1968; 102:455– 465.
927
2. Miller F, Keppke A, Yaghmai V, et al. CT diagnosis of chyluria after partial nephrectomy. AJR Am J Roentgenol 2007; 188:W25–W28. 3. Ahrar K, Matin S, Wood CG, et al. Percutaneous radiofrequency ablation of renal tumors: technique, complications and outcomes. J Vasc Interv Radiol 2005; 16:679 –288. 4. Matin, SF, Ahrar K, Cadeddu JA, et al. Residual and recurrent disease following renal energy ablative therapy: a multi-institutional study. J Urol 2006; 176:1973–1977. 5. Gervais DA, McGovern FJ, Arellano RS, McDougal WS, Mueller PR. Renal cell carcinoma: clinical experience and technical success with radiofrequency ablation of 42 tumors. Radiology 2003; 226:417– 424. 6. The R Foundation for Statistical Computing. 2007. Available at: http:// www.R-project.org. Accessed January 21, 2011. 7. Schneider J, Zaid UB, Breyer BN, et al. Chyluria associated with radiofrequency ablation of renal cell carcinoma. J Comput Assist Tomogr 2010; 34:210 –212. 8. Punekar SV, Kelkar AR, Prem AR, Deshmukh HL, Gavande PM. Surgical disconnection of lymphorenal connections for chyluria—a 15 year experience. Br J Radiol 1997; 80:858 – 863. 9. Tuck J, Pearce I, Pantelides M. Chyluria after radical nephrectomy treated with N-butyl-2-cyanoacrylate. J Urol 2000; 164:778 –779. 10. Zhang XU, Zhu QG, Ma X, et al. Renal pedicle lymphatic disconnection for chyluria via retroperitoneoscopy and open surgery: report of 53 cases with follow up. J Urol 2005; 174:1828 –1831.
Chyluria After Radiofrequency Ablation of Renal Tumors Harmeet Kaur, MD, Surena F. Matin, MD, Sanaz Javadi, MD, Valen E. Johnson, PhD, Haesun Choi, MD, Carl Sandler, MD, and Kamran Ahrar, MD
ABSTRACT Purpose: To assess the incidence of chyluria after radiofrequency (RF) ablation of renal tumors and attempt to identify predictors of this phenomenon. Materials and Methods: Over a 3-year period, 62 consecutive patients with renal tumors were treated by percutaneous computed tomography (CT)– guided or laparoscopic RF ablation, of which 41 underwent at least three posttreatment CT studies and were evaluated in this study. Three radiologists reviewed the pretreatment and posttreatment CT images for the presence or absence of fat-fluid levels in the bladder, the location of the tumor, and the size of the postablation defect. A logistic regression model was used to assess whether ablation defect size or tumor location predicted chyluria. Results: Chyluria was detected at a mean time of 44.5 weeks in 17 (41%) of 41 patients with renal tumors treated by RF ablation. A pretreatment biopsy specimen showed renal cell carcinoma in 74%. Mean tumor size was 2.77 cm, and mean initial ablation size was 4.2 cm. Chyluria persisted in seven patients. Zone of ablation defect size and tumor location were not significant predictors of chyluria (P ⫽ .64 and P ⫽ .42). Mean follow-up was 77 weeks. Conclusions: Chyluria is a common and asymptomatic finding in a significant proportion of patients undergoing RF ablation for renal tumors. Tumor location and zone of ablation defect size were not predictors of chyluria. The presence of a fat-fluid level should not be mistaken for an air-fluid level.
Chyluria, the passage of lymphatic fluid into the urine, results from the development of a communication between lymphatic channels and the pelvicalyceal system (1). The appearance on computed tomography (CT) is of a fat-fluid level in the urinary bladder that can be mistaken for an air-fluid level. Chyluria is most commonly seen secondary to parasitic infections such as Wuchereria bancrofti, retroperitoneal malignancies, and chronic infections such as tuberculosis (1). Miller et al (2) reported chyluria in 4 of 125 patients who had undergone partial nephrectomy for renal tumors. We encountered chyluria in a patient who had undergone radiofrequency (RF) ablation for renal call carcinoma. This case prompted us to review our experience
From the Departments of Diagnostic Radiology (H.K, S.J., H.C., C.S., K.A.), Urology (S.F.M.), and Biostatistics (V.E.J.), The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 1373, Houston, TX 77030. Received November 17, 2010; final revision received February 9, 2011; accepted February 14, 2011. Address correspondence to S.F.M.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2011 J Vasc Interv Radiol 2011; 22:924 –927 DOI: 10.1016/j.jvir.2011.02.014
with RF ablation of renal cell carcinoma to determine the incidence of chyluria and possible predictive factors.
MATERIALS AND METHODS Patients We retrospectively reviewed the records of 62 consecutive patients with solitary renal tumors who had undergone RF ablation at our institution over a 3-year period. Our technique of CT-guided and laparoscopic RF ablation has been previously described (3). A minimum of three posttreatment CT scans was required to be included in this review. Patients undergoing ablative therapy at our institution undergo a systematic and regimented follow-up schedule based on published recommendations (4). Patients are asked to return 4 – 6 weeks after ablation, then every 6 months for at least 2 years, then annually or biannually thereafter depending on imaging findings (4). A history and physical examination, in addition to laboratory serum and urine tests, is documented during these follow-up visits along with the required abdominal axial imaging. Patients with a history of renal cell carcinoma also undergo chest imaging annually as part of the standard follow-up for stage
Volume 22 䡲 Number 7 䡲 July 䡲 2011
T1 tumors. This retrospective study was performed under approval by our institutional review board.
Imaging Technique CT scans were obtained on a multidetector scanner (LightSpeed 16, GE Healthcare, Milwaukee, Wisconsin). Precontrast scans through the abdomen were obtained using 5-mm contiguous cuts, and 125 mL of Optiray 350 (Mallinckrodt, Hazelwood, Missouri) was injected at a rate of 5 mL/s. Postcontrast scans were obtained at 25 seconds, 60 seconds, 110 seconds, and 180 seconds and through the pelvis at 85 seconds and 180 seconds, using 5-mm contiguous cuts.
Data Collection Pretherapy CT scans and all available CT scans after RF ablation were reviewed for the presence of chyluria by three radiologists (C.S., H.K., and K.A.). Chyluria was defined as the presence of a fat-fluid level in the urinary bladder. The presence of fat was confirmed by region-of-interest measurements or use of lung windows to distinguish fat from air. Pretreatment scans were reviewed for the location of the renal tumors. Tumor locations were classified as exophytic, parenchymal, central, and mixed on the basis of definitions in the interventional radiology literature (5). The initial posttreatment scans after RF ablation were reviewed to determine the size of the ablation defect. These scans were obtained a mean of 4.5 weeks (range 2–12 weeks) after ablation therapy. The maximum diameter of the ablation defect within the kidney was measured on the final set of delayed images; posttreatment changes in the perinephric fat were not included in the measurements. Three radiologists reviewed the CT scans, and consensus was reached through discussion on the extent of postablation change. Patient charts were reviewed for any metabolic, urinary, or symptom-related abnormalities potentially relevant to chyluria.
Statistical Analysis A logistic regression model was used to assess whether tumor location or maximum zone of ablation defect diameter predicted occurrence of chyluria. Maximum likelihood procedures were used to estimate the regression coefficients of maximum ablation defect diameter and the four-level factor representing tumor location. Statistical tests were performed using open source software (6).
RESULTS Among 62 consecutive patients who had RF ablation for renal tumors during the period reviewed, 41 were identified who had at least three CT scans after treatment. Demographic, tumor, treatment, and follow-up data are summarized in the Table. Pretreatment CT scans were available in 37 patients; none of these patients had evidence of chyluria before therapy. The remainder had pretreatment imaging that either did not include the pelvis or was not archived into our
925
Table. Demographic, Tumor, and RF Ablation Summary Data for Renal Tumors During the Study Period Variable Age (y) Male Female Biopsy No Yes Renal cell carcinoma Benign Nondiagnostic Tumor size (cm) Tumor depth Exophytic Central Mixed Parenchymal No. tumors treated 1 2 3 Initial ablation size (cm) Approach Percutaneous Laparoscopic Time to detection of chyluria (wk) Follow-up time (wk)
No. 41 25 16 2 39 29 5 5 46
Mean 67.8
Range 27–87
% 61 39
92.7 74.4 12.8 12.8 2.7
1.2–4.8
24 2 16 4
52.2 4.3 34.8 8.7
37 3 1 41
90.2 7.3 2.5 4.2
2.2–7.0
30 11
73.2 26.8 44.5
3.0–84.0
77
32–152
electronic medical record and was unavailable for retrospective review. Of the 41 patients, 17 (41%) were found to have chyluria on at least one posttreatment CT scan. Chyluria was observed 3 weeks to 20 months after ablation. The mean time of detection was 11 months after ablation. In 4 of the 17 patients, chyluria was a transient finding observed on one or more CT scans and resolving on a subsequent scan. In seven patients, chyluria persisted on two or more CT scans (Fig 1a– c) obtained over 7–12 months after detection (mean 10 months). In the remaining six patients, chyluria was noted on the last available scans. There were 17 renal masses in the chyluria group; pretreatment scans were available for 14 of these. Seven lesions (50%) were exophytic, three (21%) were parenchymal, and four (29%) were central in location. Among the 11 patients with chyluria, 10 had evaluable pretreatment studies. Six lesions (60%) were exophytic, one (10%) was parenchymal, and three (30 %) were central. No mixed lesions were identified. There was no statistically significant effect of tumor location (P ⫽ .42) on the presence or absence of chyluria. There was also no significant effect of maximum ablation defect diameter (P ⫽ .64) for predicting occurrence of chyluria. Review of patient medical charts with chyluria did not reveal any specific signs. symptoms, or laboratory abnormal-
926 䡲 Chyluria After RF Ablation of Renal Tumors
Kaur et al 䡲 JVIR
Figure 1. (a) Axial contrast-enhanced CT scan through the pelvis in a 78-year-old man with a solitary renal cell carcinoma. A fat-fluid level was detected 17 months after RF ablation. (b) CT scan after 24 months shows a persistent and greater amount of chyluria. (c) Use of a lung window through the pelvis confirms the absence of air in the bladder.
Figure 2. Photograph taken during cystoscopy in a 67-year-old man after RF ablation showing multiple fat globules. The indication for cystoscopy was microhematuria on urinalysis. The urinalysis was otherwise negative. (Available in color online at www.jvir.org.)
ities attributable to chyluria. Chyluria was seen during cystoscopy in patients who were incidentally evaluated for other conditions, such as work-up of microhematuria found during their routine follow-up (Fig 2). Routine urinalysis dipstick tests are not designed to detect the presence of fat or chyle.
DISCUSSION RF ablation for renal masses is used primarily to treat patients with multiple comorbidities, advanced age, prior nephrectomy or partial nephrectomy, and multifocal renal
cell carcinoma. The reported incidence of complications ranges from 7%–18% (3,5). Complications are usually minor, requiring minimal or no intervention. To our knowledge, there is a single report of two cases of chyluria after RF ablation (7). In a retrospective review of 125 patients with renal tumors, Miller et al (2) reported 4 asymptomatic patients who developed chyluria after partial nephrectomy. In each case, chyluria manifested as a fat-fluid level in the bladder detected by CT. The authors speculated that the surgical procedure created a communication between the collecting system and lymphatic vessels of the kidney. The incidence of chyluria was much higher in our group of patients (17 of 41 [41%]) than in the patients with partial nephrectomy reported by Miller et al (2). Although these differences may be explained by study design or patient variables, it hypothetically may also be related to the nature of tissue damage caused by RF ablation permitting the fistulization of lymphatics in the zone of ablation into the urinary collecting system. Our study is limited by retrospective bias. This study design did not allow use of specific, nonroutine testing of urine for the presence of chyle or fat. Very subtle symptoms or signs may have been present and were not reflected in the patient medical record; however, given the available literature on chyluria showing this phenomenon to be largely asymptomatic, we think that is unlikely. It is also possible that chyluria is an intermittent event that was erroneously characterized as persistent but was detected by chance during every follow-up imaging examination. Regarding treatment, most of the literature is centered on chyluria resulting from parasitic infections. In these circumstances, chyluria has been described as having little effect on the general health of patients. The condition may remit spontaneously, and treatment is reserved for the few patients with symptomatic chyluria. The indications for therapy are weight loss, hypoproteinemia, anemia, anasarca, clot retention, and altered immune status. Treatment for chyluria of renal origin includes surgery to disconnect lymphorenal connections or use of glues for ureteral occlu-
Volume 22 䡲 Number 7 䡲 July 䡲 2011
sion (8 –10). However, in all of our cases, the chyluria seemed to be clinically silent. We do not believe the occurrence of chyluria to be clinically relevant at this time, and it does not seem to warrant intervention. The presence of chyluria in 41% of our patients undergoing RF ablation is an important observation that may have implications for accurate radiologic interpretation as well as a finding that that may prove informative with longer follow-up or to help avoid a misdiagnosis in patients undergoing scans for other conditions. The bladder fat-fluid interface may be confused in some cases for air in the bladder. The two can be easily differentiated by switching to lung windows or placing a region of interest over the fat level.
REFERENCES 1. Koehler R, Chiang T, Lin T. Lymphography in chyluria. AJR Am J Roentgenol 1968; 102:455– 465.
927
2. Miller F, Keppke A, Yaghmai V, et al. CT diagnosis of chyluria after partial nephrectomy. AJR Am J Roentgenol 2007; 188:W25–W28. 3. Ahrar K, Matin S, Wood CG, et al. Percutaneous radiofrequency ablation of renal tumors: technique, complications and outcomes. J Vasc Interv Radiol 2005; 16:679 –288. 4. Matin, SF, Ahrar K, Cadeddu JA, et al. Residual and recurrent disease following renal energy ablative therapy: a multi-institutional study. J Urol 2006; 176:1973–1977. 5. Gervais DA, McGovern FJ, Arellano RS, McDougal WS, Mueller PR. Renal cell carcinoma: clinical experience and technical success with radiofrequency ablation of 42 tumors. Radiology 2003; 226:417– 424. 6. The R Foundation for Statistical Computing. 2007. Available at: http:// www.R-project.org. Accessed January 21, 2011. 7. Schneider J, Zaid UB, Breyer BN, et al. Chyluria associated with radiofrequency ablation of renal cell carcinoma. J Comput Assist Tomogr 2010; 34:210 –212. 8. Punekar SV, Kelkar AR, Prem AR, Deshmukh HL, Gavande PM. Surgical disconnection of lymphorenal connections for chyluria—a 15 year experience. Br J Radiol 1997; 80:858 – 863. 9. Tuck J, Pearce I, Pantelides M. Chyluria after radical nephrectomy treated with N-butyl-2-cyanoacrylate. J Urol 2000; 164:778 –779. 10. Zhang XU, Zhu QG, Ma X, et al. Renal pedicle lymphatic disconnection for chyluria via retroperitoneoscopy and open surgery: report of 53 cases with follow up. J Urol 2005; 174:1828 –1831.