Original Article
113
Experience with Retroperitoneal Partial Nephrectomy in Bilateral Wilms Tumor Irene Isabel P. Lim1 Joshua N. Honeyman1 Elizabeth A. Fialkowski1 Jennifer M. Murphy1 Anita P. Price2 Sara J. Abramson2 Michael P. La Quaglia,1 Todd E. Heaton1 1 Division of Pediatric Surgical Service, Department of Surgery,
Memorial Sloan Kettering Cancer Center, New York, United States 2 Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, United States
Address for correspondence Todd E. Heaton, MD, Pediatric Surgical Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, NY 10065, United States (e-mail: [email protected]).
Abstract
Keywords
► Wilms tumor ► surgical technique ► kidney resection
received May 15, 2014 accepted June 23, 2014 published online September 2, 2014
Introduction Retroperitoneal partial nephrectomy has not been studied as a surgical approach for children with bilateral Wilms tumor. There are advantages to this technique, including isolation of urine leaks to the retroperitoneum, decreased risk of bowel injury, and decreased time to resuming a diet. Presently, all bilateral Wilms tumors are treated with neoadjuvant chemotherapy and attempted nephron-sparing surgery. In this study, we compare the outcomes of the retroperitoneal and transabdominal approaches in doing partial nephrectomy for bilateral Wilms tumor. Methods With the institutional review board approval, we reviewed records of 14 pediatric patients with metachronous or synchronous bilateral Wilms tumors who underwent surgery after chemotherapy between 1994 and 2014. Only operative procedures with the intent to cure were included (n ¼ 15) and of these, 5 procedures were retroperitoneal and 10 were transabdominal in approach. Individual kidneys operated upon (n ¼ 26) were analyzed using the preoperative radius exophytic/ endophytic nearness anterior/posterior location nephrometry score to ensure that resected tumors were comparable between the two surgical groups. Charts were retrospectively analyzed for intraoperative parameters and postoperative course. Differences between parameters were evaluated using Mann-Whitney and chi-square tests. Results Resected tumors in both surgical treatment groups had comparable sizes, nephrometry scores, and rates of anaplasia. Operative time, blood loss, and transfusion requirement were similar between the two groups. The extent of lymph node sampling and rates of R0 resection were equivalent. One adverse intraoperative event, a bowel enterotomy, was seen in the transabdominal group. Patients after retroperitoneal partial nephrectomy required half the time to return to an oral diet as compared with those after a transabdominal surgery, approaching statistical significance (p ¼ 0.08). Rates of the postoperative urine leak were similar, though two in the transabdominal group required reoperation for drainage. There were four recurrences, all in the transabdominal group. Conclusion Our experience demonstrates that the retroperitoneal approach is equivalent to the transabdominal technique with regards to intraoperative complications,
© 2015 Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1387944. ISSN 0939-7248.
Downloaded by: NYU. Copyrighted material.
Eur J Pediatr Surg 2015;25:113–117.
Retroperitoneal Partial Nephrectomy in BWT
Lim et al.
lymph node dissection, and R0 resection. Advantages include less time to resumption of oral feeding, decreased risk of bowel injury, and isolation of urine leaks to the retroperitoneum. It should be considered a viable surgical option in the treatment of bilateral Wilms tumors.
Introduction Around 5 to 8% of Wilms tumors are bilateral and usually present as multifocal, synchronous lesions at an earlier age than a unilateral Wilms tumor.1–3 The challenge in treating bilateral Wilms tumor (BWT) is achieving a cure while preserving renal function, because these patients are at an increased risk of end-stage renal disease, even in the absence of associated renal anomalies.1 Recent studies in BWT have shown that preoperative chemotherapy followed by resection preserves more renal parenchyma,1,4 and this management strategy is now the standard of care. The retroperitoneal approach to the resection of Wilms tumor was abandoned in unilateral disease because of higher complication rates and the increased risk of intraoperative rupture and subsequent upstaging seen with a flank incision.5,6 In contrast, patients with BWT presents with smaller multifocal tumors and receive preoperative chemotherapy with a subsequent reduction in tumor size. Until now, studies on nephron-sparing surgery in BWT have described the use of the transabdominal approach.7,8 This technique, however, is merely a holdover from the management of unilateral tumors. Retroperitoneal partial nephrectomy has been gaining popularity over the transabdominal approach as the standard for resection of renal tumors in adults, because resection margins and complications are generally equivalent, but the retroperitoneal approach is associated with decreased operative time and blood loss.9,10 In addition, the retroperitoneal approach provides better access to the posterior face of the kidney, containment of urine leaks to the retroperitoneum, and avoidance of bowel injury and postoperative ileus. However, this approach to renal tumor resections has not yet been studied in children. Here, we retrospectively compare the perioperative outcomes of the transabdominal approach and the retroperitoneal approach for the resection of BWT.
Methods After obtaining the institutional review board approval, we searched our database for pediatric patients with BWT treated with nephron-sparing surgery after chemotherapy at our institution between 1994 and 2014. After identifying 14 patients, we reviewed their charts and collected pertinent data on demographics, synchronicity of tumors, preoperative imaging, operative technique, operative time, blood loss, transfusion volume, intraoperative complications, margin status, lymph node harvest, and postoperative complications. To ensure that the complexity of resection was equivalent between the two groups, we calculated the preoperative European Journal of Pediatric Surgery
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radius exophytic/endophytic nearness anterior/posterior location (RENAL) nephrometry score for the dominant lesion in each kidney operated upon (n ¼ 26), taking into account size, endophytic properties, location, and relationship to the collecting system.11 We also compared the individual kidneys across techniques with respect to mean tumor size and presence of anaplasia on pathology. For the operative technique, the retroperitoneal approach was initiated with flank incisions along the Langer lines midway between the costal margin and the iliac crest. The retroperitoneum and Gerota fascia were entered along the lateral aspect. Tumors were excised after identification by both intraoperative ultrasound and manual palpation, all within the confines of the retroperitoneal space. The anterior abdominal approach was performed using a midline incision. The colon was reflected medially and Gerota fascia was entered on the anterior aspect. As with the retroperitoneal approach, tumors were identified via manual palpation and intraoperative ultrasound. In both surgical approaches, negative margins were confirmed by intraoperative frozen section. The surgical approaches were compared in terms of operative time, estimated blood loss, volume of transfusion, bilaterality, adverse intraoperative events, extent of lymph node sampling, and margin status. R0 resection was determined by examining the margins on final pathology. Postoperative courses were compared with regard to the time to resuming an oral diet, oral intolerance greater than 5 days, and length of intensive care unit (ICU) and hospital stays. Postoperative complications, including prolonged urine leaks and urinomas were also compared between the two groups, with particular attention to the need for intervention or reoperation. Statistical analyses were performed with SPSS software (version 16.0.1, IBM Corporation, Armonk, New York, United States). Categorical and continuous variables were compared by chi-square and Mann-Whitney tests, respectively. All p values are two-tailed with p < 0.05 indicating statistical significance.
Results Overall, 14 patients underwent 15 procedures; 5 of these were retroperitoneal and 10 were transabdominal in approach. One patient developed a unilateral recurrence 2 years after R0 resection for BWT, and therefore underwent two surgeries at our institution. A total of 26 kidneys were operated upon, as some patients underwent partial or complete nephrectomy before presenting to our institution. All surgical procedures were performed by a single surgeon
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Table 1 Patient and tumor characteristics at time of operation Characteristics
Retroperitoneal approach a
Transabdominal approach
p-Value
a
n ¼5
n ¼ 10
Median age (range, y)
2.9 (2.3–3.8)
3.7 (1.4–4.9)
0.39
Male sex
1
3
0.68
Synchronous bilateral tumors
5
7
0.17
History of abdominal surgery
2
6
0.46
Patient parameters at time of surgery
b
b
Tumor parameters
n ¼ 11
n ¼ 15
Median tumor size (range, cm)
4.0 (0.9–7.4)
2.9 (0.8–11)
0.53
Median numerical score (range)
9 (4–11)
10 (4–12)
0.19
Posterior location
6
6
0.12
Nephrometry score
a
Involvement of main renal artery or vein
5
8
0.43
Anaplasia
2
1
0.36
Number of surgical procedures. Number of resected kidneys.
(M.P.L.). Our analysis comparing patients across the two surgical techniques revealed no significant differences in age, gender, synchronicity of disease, or a history of abdominal surgery (►Table 1). The largest tumors in each operated kidney were similar in size, RENAL nephrometry score, and presence of anaplasia on pathology (►Table 1) between the groups. All 5 retroperitoneal procedures and 6 of 10 transabdominal procedures were bilateral resections. In the comparison of intraoperative variables, we found that operative times, estimated blood loss, and need for transfusion were similar between the two groups. The incidence of adverse intraoperative events did not differ significantly (p ¼ 0.10); however, the only major complication, a transverse colon enterotomy, occurred in the transabdominal group. Importantly, the number of lymph nodes sampled and rate of R0 resection were also equivalent (►Table 2). Overall 8 tumors in the retroperitoneal group and 10 in the transabdominal group were of favorable histology (p ¼ 0.81). Two patients had evidence of tumor thrombus
in the inferior vena cava on pathology, both in the transabdominal group. Comparative analysis of postoperative course between the groups demonstrated no significant differences in length of ICU and overall hospital stay (p ¼ 0.90 and 0.54, respectively). The length of time to oral intake after surgery approached statistical significance (p ¼ 0.08), with patients requiring twice as many days after the transabdominal approach to tolerate a diet (mean, 2.2 vs. 4.4 days). Similarly, only one patient experienced prolonged nausea and vomiting requiring continued hydration with maintenance intravenous fluids after undergoing retroperitoneal resection, compared with six patients after transabdominal resection (p ¼ 0.13). The incidence of postoperative complications, including urine leaks and urinomas, as well as the length of drainage, were equivalent between the groups. Only two patients developed urine leaks that required reoperation, both of whom were in the transabdominal group. One patient required exploratory laparotomy for washout of urinary ascites
Table 2 Comparison of intraoperative and postoperative variables
a
Retroperitoneal approach n ¼5
Transabdominal approach n ¼ 10
p-Value
Bilateral resection
5
6
0.10
Adverse intraoperative events
0
1
0.46
Number of lymph nodes removed
6.8 2.6
7.6 9.4
0.27
R0 resection
4
9
0.59
Mean time to per os tolerance (d)
2.2 1.3
4.4 1.4
0.08
Prolonged per os intolerance
1
6
0.14
Number of postoperative urine leak or urinoma
2
4a
1.00
Two of the four patients in the transabdominal group who developed urine leaks postoperatively required reoperation for management of the urine leak. European Journal of Pediatric Surgery
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Lim et al.
and drain placement, while the other underwent drain placement by an interventional radiologist. All patients were alive at the time of analysis. There were four recurrences and all occurred after transabdominal resection (p ¼ 0.10). Median follow-up was 11 months (range, 0.33–165.7 months). Mean serum creatinine at follow-up was 0.57 mg/dL (standard deviation 0.27). Only one patient required permanent hemodialysis; 4 months after partial nephrectomy at our institution, the patient developed anuria secondary to an obstructing recurrence and underwent emergency completion nephrectomy at another institution.
Discussion Nephron-sparing surgery has evolved to become the standard of care for BWT because of the importance of preserving renal function.7 While well studied in the adult population, the most appropriate approach for bilateral nephron-sparing surgery in children has not been established. Our study directly compares the outcomes of the traditional anterior abdominal approach to the retroperitoneal approach in children with BWT. Our study benefits from being a single-institution, single-surgeon study; however, it is limited by its retrospective nature and small sample size. Despite our limited numbers, our patient populations were similar in demographics and tumor characteristics across the two groups. The largest tumors in each operated kidney were compared using the RENAL nephrometry score. The score incorporates the tumor’s maximal diameter, exophytic and endophytic properties, proximity to the collecting system, and location relative to polar lines.10 While useful in characterizing the largest tumors, the RENAL nephrometry score does not account for the multiple tumors resected per patient, which may explain why it did not correlate with the postoperative complications in this study. Existing systems such as the RENAL nephrometry score and the preoperative aspects and dimensions used for anatomic classification12,13 were developed to predict surgical complexity and risk of perioperative complications for solitary renal tumors in adults, and thus are inadequate for multifocal tumors. A new system that incorporates the characteristics of multiple tumors would allow for a more informed comparison of outcomes, and perhaps better perioperative risk stratification, for BWT. In a recent meta-analysis, Ren et al compared the transabdominal and retroperitoneal approaches for partial nephrectomy in patients with renal cell carcinoma and found that resection with the retroperitoneal approach was associated with shorter operating times, lower estimated blood loss, and shorter length of hospital stay.14 In our cohort, results with the retroperitoneal approach were similar to those of the transabdominal approach in terms of blood loss, transfusion requirement, and hospital stay. Operative times were also equivalent; however, the time required to reposition the patient during a bilateral retroperitoneal resection was included, so the actual period of open incision is shorter than noted. Critics of the retroperitoneal approach argue that the surgeon is limited to a smaller, less familiar working space, which may result in less adequate resection, higher risk of European Journal of Pediatric Surgery
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inadvertent injury,15 and limited lymph node sampling. Our study, however, shows equivalent rates of R0 resection and lymph node dissection achieved by the two approaches. Moreover, the only inadvertent injury, a colon enterotomy, occurred with the transabdominal approach. There are several benefits associated with limiting dissection to the retroperitoneal space: any urine leak is contained within the retroperitoneum and bowel manipulation is avoided, which consequently prevents future adhesions and shortens the time to oral intake postoperatively.16 Patients in our cohort who developed urine leaks after retroperitoneal resection were managed as outpatients, while two of the four patients who developed urine leaks after transabdominal resection required reoperation. After retroperitoneal resection, our patients were able to tolerate an oral diet in half the time as those who underwent transabdominal surgery, a difference which approached statistical significance.
Conclusions Retroperitoneal resection of the BWT is equivalent to the transabdominal approach in terms of R0 resection, lymph node sampling, and intraoperative and postoperative complications. Although, the study is limited by its sample size, our analysis shows that the retroperitoneal approach may provide clinically valuable benefits over its transabdominal counterpart, namely, the avoidance of bowel injuries, decreased time to resuming an oral diet, and containment of urine leaks. It should be considered a viable surgical option for the treatment of BWT. Prospective studies are needed to increase the experience with retroperitoneal partial nephrectomy in children and further define its potential benefits. Current classification systems of renal tumors are inadequate for the characterization of multifocal BWT in children. Retrospective imaging analysis of a larger cohort of BWT might facilitate the development of a grading system that would correlate with operative and postoperative outcomes.
Conflict of Interest None.
References 1 Breslow NE, Collins AJ, Ritchey ML, Grigoriev YA, Peterson SM,
Green DM. End stage renal disease in patients with Wilms tumor: results from the National Wilms Tumor Study Group and the United States Renal Data System. J Urol 2005;174(5): 1972–1975 2 Aronson DC, Slaar A, Heinen RC, de Kraker J, Heij HA. Long-term outcome of bilateral Wilms tumors (BWT). Pediatr Blood Cancer 2011;56(7):1110–1113 3 Kieran K, Williams MA, Dome JS, McGregor LM, Krasin MJ, Davidoff AM. Margin status and tumor recurrence after nephron-sparing surgery for bilateral Wilms tumor. J Pediatr Surg 2013;48(7): 1481–1485 4 Cooper CS, Jaffe WI, Huff DS, et al. The role of renal salvage procedures for bilateral Wilms tumor: a 15-year review. J Urol 2000;163(1):265–268
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11 Kutikov A, Uzzo RG. The R.E.N.A.L. nephrometry score: a compre-
Breslow NE. Surgical complications after primary nephrectomy for Wilms’ tumor: report from the National Wilms’ Tumor Study Group. J Am Coll Surg 2001;192(1):63–68, quiz 146 Shamberger RC, Guthrie KA, Ritchey ML, et al. Surgery-related factors and local recurrence of Wilms tumor in National Wilms Tumor Study 4. Ann Surg 1999;229(2):292–297 Davidoff AM, Giel DW, Jones DP, et al. The feasibility and outcome of nephron-sparing surgery for children with bilateral Wilms tumor. The St Jude Children’s Research Hospital experience: 1999-2006. Cancer 2008;112(9):2060–2070 Fuchs J, Szavay P, Seitz G, Handgretinger R, Schäfer JF, Warmann SW. Nephron sparing surgery for synchronous bilateral nephroblastoma involving the renal hilus. J Urol 2011;186(4):1430–1436 Hughes-Hallett A, Patki P, Patel N, Barber NJ, Sullivan M, Thilagarajah R. Robot-assisted partial nephrectomy: a comparison of the transperitoneal and retroperitoneal approaches. J Endourol 2013; 27(7):869–874 Zhang X, Li HZ, Ma X, Zheng T, Li LC, Ye ZQ. Retroperitoneal laparoscopic nephron-sparing surgery for renal tumors: report of 32 cases. Urology 2005;65(6):1080–1084, discussion 1084–1085
hensive standardized system for quantitating renal tumor size, location and depth. J Urol 2009;182(3):844–853 Ficarra V, Novara G, Secco S, et al. Preoperative aspects and dimensions used for an anatomical (PADUA) classification of renal tumours in patients who are candidates for nephron-sparing surgery. Eur Urol 2009;56(5):786–793 Kobayashi K, Saito T, Kitamura Y, et al. The RENAL nephrometry score and the PADUA classification for the prediction of perioperative outcomes in patients receiving nephron-sparing surgery: feasible tools to predict intraoperative conversion to nephrectomy. Urol Int 2013;91(3):261–268 Ren T, Liu Y, Zhao X, et al. Transperitoneal approach versus retroperitoneal approach: a meta-analysis of laparoscopic partial nephrectomy for renal cell carcinoma. PLoS ONE 2014;9(3):e91978 McAllister M, Bhayani SB, Ong A, et al. Vena caval transection during retroperitoneoscopic nephrectomy: report of the complication and review of the literature. J Urol 2004;172(1):183–185 Wright JL, Porter JR. Laparoscopic partial nephrectomy: comparison of transperitoneal and retroperitoneal approaches. J Urol 2005;174(3):841–845
6
7
8
9
10
12
13
14
15
16
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European Journal of Pediatric Surgery
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113
Experience with Retroperitoneal Partial Nephrectomy in Bilateral Wilms Tumor Irene Isabel P. Lim1 Joshua N. Honeyman1 Elizabeth A. Fialkowski1 Jennifer M. Murphy1 Anita P. Price2 Sara J. Abramson2 Michael P. La Quaglia,1 Todd E. Heaton1 1 Division of Pediatric Surgical Service, Department of Surgery,
Memorial Sloan Kettering Cancer Center, New York, United States 2 Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, United States
Address for correspondence Todd E. Heaton, MD, Pediatric Surgical Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, NY 10065, United States (e-mail: [email protected]).
Abstract
Keywords
► Wilms tumor ► surgical technique ► kidney resection
received May 15, 2014 accepted June 23, 2014 published online September 2, 2014
Introduction Retroperitoneal partial nephrectomy has not been studied as a surgical approach for children with bilateral Wilms tumor. There are advantages to this technique, including isolation of urine leaks to the retroperitoneum, decreased risk of bowel injury, and decreased time to resuming a diet. Presently, all bilateral Wilms tumors are treated with neoadjuvant chemotherapy and attempted nephron-sparing surgery. In this study, we compare the outcomes of the retroperitoneal and transabdominal approaches in doing partial nephrectomy for bilateral Wilms tumor. Methods With the institutional review board approval, we reviewed records of 14 pediatric patients with metachronous or synchronous bilateral Wilms tumors who underwent surgery after chemotherapy between 1994 and 2014. Only operative procedures with the intent to cure were included (n ¼ 15) and of these, 5 procedures were retroperitoneal and 10 were transabdominal in approach. Individual kidneys operated upon (n ¼ 26) were analyzed using the preoperative radius exophytic/ endophytic nearness anterior/posterior location nephrometry score to ensure that resected tumors were comparable between the two surgical groups. Charts were retrospectively analyzed for intraoperative parameters and postoperative course. Differences between parameters were evaluated using Mann-Whitney and chi-square tests. Results Resected tumors in both surgical treatment groups had comparable sizes, nephrometry scores, and rates of anaplasia. Operative time, blood loss, and transfusion requirement were similar between the two groups. The extent of lymph node sampling and rates of R0 resection were equivalent. One adverse intraoperative event, a bowel enterotomy, was seen in the transabdominal group. Patients after retroperitoneal partial nephrectomy required half the time to return to an oral diet as compared with those after a transabdominal surgery, approaching statistical significance (p ¼ 0.08). Rates of the postoperative urine leak were similar, though two in the transabdominal group required reoperation for drainage. There were four recurrences, all in the transabdominal group. Conclusion Our experience demonstrates that the retroperitoneal approach is equivalent to the transabdominal technique with regards to intraoperative complications,
© 2015 Georg Thieme Verlag KG Stuttgart · New York
DOI http://dx.doi.org/ 10.1055/s-0034-1387944. ISSN 0939-7248.
Downloaded by: NYU. Copyrighted material.
Eur J Pediatr Surg 2015;25:113–117.
Retroperitoneal Partial Nephrectomy in BWT
Lim et al.
lymph node dissection, and R0 resection. Advantages include less time to resumption of oral feeding, decreased risk of bowel injury, and isolation of urine leaks to the retroperitoneum. It should be considered a viable surgical option in the treatment of bilateral Wilms tumors.
Introduction Around 5 to 8% of Wilms tumors are bilateral and usually present as multifocal, synchronous lesions at an earlier age than a unilateral Wilms tumor.1–3 The challenge in treating bilateral Wilms tumor (BWT) is achieving a cure while preserving renal function, because these patients are at an increased risk of end-stage renal disease, even in the absence of associated renal anomalies.1 Recent studies in BWT have shown that preoperative chemotherapy followed by resection preserves more renal parenchyma,1,4 and this management strategy is now the standard of care. The retroperitoneal approach to the resection of Wilms tumor was abandoned in unilateral disease because of higher complication rates and the increased risk of intraoperative rupture and subsequent upstaging seen with a flank incision.5,6 In contrast, patients with BWT presents with smaller multifocal tumors and receive preoperative chemotherapy with a subsequent reduction in tumor size. Until now, studies on nephron-sparing surgery in BWT have described the use of the transabdominal approach.7,8 This technique, however, is merely a holdover from the management of unilateral tumors. Retroperitoneal partial nephrectomy has been gaining popularity over the transabdominal approach as the standard for resection of renal tumors in adults, because resection margins and complications are generally equivalent, but the retroperitoneal approach is associated with decreased operative time and blood loss.9,10 In addition, the retroperitoneal approach provides better access to the posterior face of the kidney, containment of urine leaks to the retroperitoneum, and avoidance of bowel injury and postoperative ileus. However, this approach to renal tumor resections has not yet been studied in children. Here, we retrospectively compare the perioperative outcomes of the transabdominal approach and the retroperitoneal approach for the resection of BWT.
Methods After obtaining the institutional review board approval, we searched our database for pediatric patients with BWT treated with nephron-sparing surgery after chemotherapy at our institution between 1994 and 2014. After identifying 14 patients, we reviewed their charts and collected pertinent data on demographics, synchronicity of tumors, preoperative imaging, operative technique, operative time, blood loss, transfusion volume, intraoperative complications, margin status, lymph node harvest, and postoperative complications. To ensure that the complexity of resection was equivalent between the two groups, we calculated the preoperative European Journal of Pediatric Surgery
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No. 1/2015
radius exophytic/endophytic nearness anterior/posterior location (RENAL) nephrometry score for the dominant lesion in each kidney operated upon (n ¼ 26), taking into account size, endophytic properties, location, and relationship to the collecting system.11 We also compared the individual kidneys across techniques with respect to mean tumor size and presence of anaplasia on pathology. For the operative technique, the retroperitoneal approach was initiated with flank incisions along the Langer lines midway between the costal margin and the iliac crest. The retroperitoneum and Gerota fascia were entered along the lateral aspect. Tumors were excised after identification by both intraoperative ultrasound and manual palpation, all within the confines of the retroperitoneal space. The anterior abdominal approach was performed using a midline incision. The colon was reflected medially and Gerota fascia was entered on the anterior aspect. As with the retroperitoneal approach, tumors were identified via manual palpation and intraoperative ultrasound. In both surgical approaches, negative margins were confirmed by intraoperative frozen section. The surgical approaches were compared in terms of operative time, estimated blood loss, volume of transfusion, bilaterality, adverse intraoperative events, extent of lymph node sampling, and margin status. R0 resection was determined by examining the margins on final pathology. Postoperative courses were compared with regard to the time to resuming an oral diet, oral intolerance greater than 5 days, and length of intensive care unit (ICU) and hospital stays. Postoperative complications, including prolonged urine leaks and urinomas were also compared between the two groups, with particular attention to the need for intervention or reoperation. Statistical analyses were performed with SPSS software (version 16.0.1, IBM Corporation, Armonk, New York, United States). Categorical and continuous variables were compared by chi-square and Mann-Whitney tests, respectively. All p values are two-tailed with p < 0.05 indicating statistical significance.
Results Overall, 14 patients underwent 15 procedures; 5 of these were retroperitoneal and 10 were transabdominal in approach. One patient developed a unilateral recurrence 2 years after R0 resection for BWT, and therefore underwent two surgeries at our institution. A total of 26 kidneys were operated upon, as some patients underwent partial or complete nephrectomy before presenting to our institution. All surgical procedures were performed by a single surgeon
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Table 1 Patient and tumor characteristics at time of operation Characteristics
Retroperitoneal approach a
Transabdominal approach
p-Value
a
n ¼5
n ¼ 10
Median age (range, y)
2.9 (2.3–3.8)
3.7 (1.4–4.9)
0.39
Male sex
1
3
0.68
Synchronous bilateral tumors
5
7
0.17
History of abdominal surgery
2
6
0.46
Patient parameters at time of surgery
b
b
Tumor parameters
n ¼ 11
n ¼ 15
Median tumor size (range, cm)
4.0 (0.9–7.4)
2.9 (0.8–11)
0.53
Median numerical score (range)
9 (4–11)
10 (4–12)
0.19
Posterior location
6
6
0.12
Nephrometry score
a
Involvement of main renal artery or vein
5
8
0.43
Anaplasia
2
1
0.36
Number of surgical procedures. Number of resected kidneys.
(M.P.L.). Our analysis comparing patients across the two surgical techniques revealed no significant differences in age, gender, synchronicity of disease, or a history of abdominal surgery (►Table 1). The largest tumors in each operated kidney were similar in size, RENAL nephrometry score, and presence of anaplasia on pathology (►Table 1) between the groups. All 5 retroperitoneal procedures and 6 of 10 transabdominal procedures were bilateral resections. In the comparison of intraoperative variables, we found that operative times, estimated blood loss, and need for transfusion were similar between the two groups. The incidence of adverse intraoperative events did not differ significantly (p ¼ 0.10); however, the only major complication, a transverse colon enterotomy, occurred in the transabdominal group. Importantly, the number of lymph nodes sampled and rate of R0 resection were also equivalent (►Table 2). Overall 8 tumors in the retroperitoneal group and 10 in the transabdominal group were of favorable histology (p ¼ 0.81). Two patients had evidence of tumor thrombus
in the inferior vena cava on pathology, both in the transabdominal group. Comparative analysis of postoperative course between the groups demonstrated no significant differences in length of ICU and overall hospital stay (p ¼ 0.90 and 0.54, respectively). The length of time to oral intake after surgery approached statistical significance (p ¼ 0.08), with patients requiring twice as many days after the transabdominal approach to tolerate a diet (mean, 2.2 vs. 4.4 days). Similarly, only one patient experienced prolonged nausea and vomiting requiring continued hydration with maintenance intravenous fluids after undergoing retroperitoneal resection, compared with six patients after transabdominal resection (p ¼ 0.13). The incidence of postoperative complications, including urine leaks and urinomas, as well as the length of drainage, were equivalent between the groups. Only two patients developed urine leaks that required reoperation, both of whom were in the transabdominal group. One patient required exploratory laparotomy for washout of urinary ascites
Table 2 Comparison of intraoperative and postoperative variables
a
Retroperitoneal approach n ¼5
Transabdominal approach n ¼ 10
p-Value
Bilateral resection
5
6
0.10
Adverse intraoperative events
0
1
0.46
Number of lymph nodes removed
6.8 2.6
7.6 9.4
0.27
R0 resection
4
9
0.59
Mean time to per os tolerance (d)
2.2 1.3
4.4 1.4
0.08
Prolonged per os intolerance
1
6
0.14
Number of postoperative urine leak or urinoma
2
4a
1.00
Two of the four patients in the transabdominal group who developed urine leaks postoperatively required reoperation for management of the urine leak. European Journal of Pediatric Surgery
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No. 1/2015
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b
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and drain placement, while the other underwent drain placement by an interventional radiologist. All patients were alive at the time of analysis. There were four recurrences and all occurred after transabdominal resection (p ¼ 0.10). Median follow-up was 11 months (range, 0.33–165.7 months). Mean serum creatinine at follow-up was 0.57 mg/dL (standard deviation 0.27). Only one patient required permanent hemodialysis; 4 months after partial nephrectomy at our institution, the patient developed anuria secondary to an obstructing recurrence and underwent emergency completion nephrectomy at another institution.
Discussion Nephron-sparing surgery has evolved to become the standard of care for BWT because of the importance of preserving renal function.7 While well studied in the adult population, the most appropriate approach for bilateral nephron-sparing surgery in children has not been established. Our study directly compares the outcomes of the traditional anterior abdominal approach to the retroperitoneal approach in children with BWT. Our study benefits from being a single-institution, single-surgeon study; however, it is limited by its retrospective nature and small sample size. Despite our limited numbers, our patient populations were similar in demographics and tumor characteristics across the two groups. The largest tumors in each operated kidney were compared using the RENAL nephrometry score. The score incorporates the tumor’s maximal diameter, exophytic and endophytic properties, proximity to the collecting system, and location relative to polar lines.10 While useful in characterizing the largest tumors, the RENAL nephrometry score does not account for the multiple tumors resected per patient, which may explain why it did not correlate with the postoperative complications in this study. Existing systems such as the RENAL nephrometry score and the preoperative aspects and dimensions used for anatomic classification12,13 were developed to predict surgical complexity and risk of perioperative complications for solitary renal tumors in adults, and thus are inadequate for multifocal tumors. A new system that incorporates the characteristics of multiple tumors would allow for a more informed comparison of outcomes, and perhaps better perioperative risk stratification, for BWT. In a recent meta-analysis, Ren et al compared the transabdominal and retroperitoneal approaches for partial nephrectomy in patients with renal cell carcinoma and found that resection with the retroperitoneal approach was associated with shorter operating times, lower estimated blood loss, and shorter length of hospital stay.14 In our cohort, results with the retroperitoneal approach were similar to those of the transabdominal approach in terms of blood loss, transfusion requirement, and hospital stay. Operative times were also equivalent; however, the time required to reposition the patient during a bilateral retroperitoneal resection was included, so the actual period of open incision is shorter than noted. Critics of the retroperitoneal approach argue that the surgeon is limited to a smaller, less familiar working space, which may result in less adequate resection, higher risk of European Journal of Pediatric Surgery
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inadvertent injury,15 and limited lymph node sampling. Our study, however, shows equivalent rates of R0 resection and lymph node dissection achieved by the two approaches. Moreover, the only inadvertent injury, a colon enterotomy, occurred with the transabdominal approach. There are several benefits associated with limiting dissection to the retroperitoneal space: any urine leak is contained within the retroperitoneum and bowel manipulation is avoided, which consequently prevents future adhesions and shortens the time to oral intake postoperatively.16 Patients in our cohort who developed urine leaks after retroperitoneal resection were managed as outpatients, while two of the four patients who developed urine leaks after transabdominal resection required reoperation. After retroperitoneal resection, our patients were able to tolerate an oral diet in half the time as those who underwent transabdominal surgery, a difference which approached statistical significance.
Conclusions Retroperitoneal resection of the BWT is equivalent to the transabdominal approach in terms of R0 resection, lymph node sampling, and intraoperative and postoperative complications. Although, the study is limited by its sample size, our analysis shows that the retroperitoneal approach may provide clinically valuable benefits over its transabdominal counterpart, namely, the avoidance of bowel injuries, decreased time to resuming an oral diet, and containment of urine leaks. It should be considered a viable surgical option for the treatment of BWT. Prospective studies are needed to increase the experience with retroperitoneal partial nephrectomy in children and further define its potential benefits. Current classification systems of renal tumors are inadequate for the characterization of multifocal BWT in children. Retrospective imaging analysis of a larger cohort of BWT might facilitate the development of a grading system that would correlate with operative and postoperative outcomes.
Conflict of Interest None.
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