laparoscopic surgery has developed to a standard of care in patients with small ( < 6 cm ) adrenal masses . recently , numerous authors reported on minimally invasive adrenalectomies also in patients with larger tumors , but significant concerns regarding the adequacy of laparoscopic surgery in potentially malignant adrenal tumors still exist . therefore , minimally invasive surgery of large adrenal tumors has to follow oncological principles : 
 sufficient resection margins , intact tumor capsule , no tumor cell dissemination , andno risk for port site metastases . sufficient resection margins , intact tumor capsule , no tumor cell dissemination , and no risk for port site metastases . in the present study , intra- and postoperative morbidity were analysed retrospectively in patients with tumor size 6 cm and compared to patients with tumors larger than 6 cm undergoing minimally invasive trans- or retroperitoneal adrenalectomy . all 279 patients undergoing laparoscopic trans- or retroperitoneal adrenal surgery between 1994 and 2012 were included in this retrospective analysis . patients were separated in 2 groups : patients with tumor size 6 cm ( group 1 ) , and patients with larger tumors ( group 2 ) . intra- and postoperative morbidity after adrenal surgery was analysed for the two groups . between 1994 and 2003 , after 2003 , the decision to perform an adrenalectomy by a trans- or by a retroperitoneal approach was guided by the size of the tumor and by the body - mass - index ( bmi ) . patients with tumors larger than 6 cm and a bmi of > 40 kg / m underwent a transperitoneal adrenalectomy ; all others underwent adrenalectomy by a retroperitoneoscopic approach . patients with aldosterone - producing adenomas had been treated preoperatively with 200 - 400 mg / d of spironolactone for 6 weeks . patients with pheochromocytoma had received alpha - receptor inhibitor during the last 10 preoperative days . three trocars are used for left adrenalectomy , an additional trocar is used to retract the liver for right adrenalectomy . for left adrenalectomy , the left colonic flexure is mobilized along the gerota fascia . dissecting through the avascular plain between the pancreatic tail and the kidney , the spleen and the pancreatic tail the liver is mobilized along the lateral border of the inferior vena cava to control potential bleeding . the fat tissue surrounding the adrenal gland is left in place to avoid tumor manipulation . dorsal mobilization of the tumor is performed , and followed by lateral and cranial mobilization . the adrenal gland and the surrounding fat tissue are removed en bloc with a retrieval bag . subsequently , fibers of the quadratus lumborum muscle are spread digitally and the perirenal fascia is opened from dorsal . after reaching the retroperitoneal space , this area is dilated with the forefinger . after blunt preparation of the retroperitoneal space , the operation is continued by dissection of the retrorenal fat tissue from the renal capsule at the upper renal pole . after visualization of the inferior vena cava at the right side and identification of the renal vein at the left side , the adrenal vein is divided . the adrenal gland and the surrounding fat tissue are removed en bloc with a retrieval bag . using the t - test , p - value of < 0.05 were regarded as statistically significant . three trocars are used for left adrenalectomy , an additional trocar is used to retract the liver for right adrenalectomy . dissecting through the avascular plain between the pancreatic tail and the kidney , the spleen and the pancreatic tail are moved medially . in right adrenalectomy , the liver is mobilized along the lateral border of the inferior vena cava to control potential bleeding . the fat tissue surrounding the adrenal gland is left in place to avoid tumor manipulation . dorsal mobilization of the tumor is performed , and followed by lateral and cranial mobilization . the adrenal gland and the surrounding fat tissue are removed en bloc with a retrieval bag . subsequently , fibers of the quadratus lumborum muscle are spread digitally and the perirenal fascia is opened from dorsal . after reaching the retroperitoneal space , after blunt preparation of the retroperitoneal space , the operation is continued by dissection of the retrorenal fat tissue from the renal capsule at the upper renal pole . after visualization of the inferior vena cava at the right side and identification of the renal vein at the left side , the adrenal vein is divided . the adrenal gland and the surrounding fat tissue are removed en bloc with a retrieval bag . the wilcoxon signed rank test was employed for the evaluation of the distribution patterns . using the t - test , between 1/1994 and 7/2012 , 279 patients underwent laparoscopic trans- and retroperitoneal adrenalectomies : tumor size was 6 cm in 227 cases ( group 1 ) and > 6 cm in 52 cases ( group 2 ) . patients and tumor characteristics are shown in [ table 1 ] . in group 1 , significantly more patients presented with aldosterone - producing adenomas ( 25% vs. 2% , p = 0.001 ) . the incidence of the adrenocortical carcinoma was higher in group 2 patients ( 6.3% vs. 0.4% , p = 0.039 ) . patients and tumor characteristics pathological characteristics significantly more patients underwent transperitoneal adrenalectomy in group 2 than in group 1 ( 71% vs. 32% , p = 0.023 , table 3 ) . single - incision laparoscopic adrenalectomies ( sils ) were performed only in group 1 patients . duration of surgery was significantly longer ( 105 min vs. 88 min , p = 0.03 ) and the estimated blood loss was significantly higher ( 470 ml vs. 150 ml ) in group 2 patients . surgical procedures and operative outcomes three intraoperative bleedings occurred in group 2 patients ( 5.7% ) as opposed to two bleedings in group 1 ( 0.8% , p = 0.041 , table 4 ) leading to one conversion in a group 2 patient . intra- and postoperative complications the conversion rate was significantly higher in group 2 than in group 1 ( 5.7% vs. 1.3% , p = 0.011 , table 4 ) . also , postoperative complication rate was significantly higher in group 2 than in group 1 ( 11.5% vs. 3.0% , p = 0.022 ) . however , only two major complications occurred : an acute cardiac failure in a group 1 patient and one pancreatic fistula treated conservatively in a group 2 patient . the current study presents a large patient population undergoing laparoscopic adrenalectomy for large ( > 6 cm ) tumors . as it might have been expected , intra- and postoperative morbidity was slightly higher in patients with larger tumors , however , the complication rate of 11.5% was still acceptable . moreover , morbidity and complication rates of up to 27% were observed following open adrenalectomy and this was accompanied by prolonged hospital stay , more pain at the incision site and an increased risk of postoperative hernias . due to a close anatomical relation to spleen , kidney , liver and inferior caval vein , laparoscopic adrenal surgery for large tumors is technically demanding . injury to the adrenal capsule is associated with increased probability of relevant consequences in patients with larger tumors : 23% of group 2 patients presented with pheochromocytoma and 12% had a malignant disease . therefore , surgeons undertaking laparoscopic adrenalectomy in this particular population should have a large experience in laparoscopic adrenal surgery . experience with other , particularly with gastrointestinal laparoscopic procedures might shorten the learning curve . in the present study , 86.5% of the adrenalectomies for tumors > 6 cm were performed by the first author of the study ( a.a . ) after an experience of 127 laparoscopic adrenalectomies and already twelve years experience in laparoscopic colorectal surgery . retroperitoneoscopic adrenalectomy in patient with very large tumors might pose serious additional technical difficulties because of a limited operative field . in obese patients , the prone positioning will lead to even more compression of the retroperitoneal space in spite of high insufflation pressure . thus , laparoscopic transperitoneal adrenalectomy by a lateral approach is preferred in case of tumors larger than 8 cm and in patients with bmi > 40 kg / m at our institution . conventional adrenalectomy is reserved for cases with clear radiological signs of malignancy ( invasion of surrounding structures , evidence of metastases ) and was performed only in 8 cases since 2005 . in our study , duration of surgery was longer and blood loss was slightly larger in patients with tumors > 6 cm as compared to patients with smaller adrenal masses . some recent publications indicated that laparoscopic adrenalectomy can be performed safely for tumors up to 15 cm .. tsuru et al . found no statistically significant difference regarding blood loss , time of surgery and complication rate between patients with tumors < 5 cm ( n = 155 ) and patients with larger tumors ( n = 23 ) , however , their study was smaller . the authors of the latter study recommended that invasion of adjacent structures should serve as an only indication for conventional adrenalectomy . however , it should be weighed against the fact that almost 95% of patients with large adrenal tumors still benefited from the laparoscopic approach . nevertheless , one should not hesitate to convert to conventional adrenalectomy if oncological principles can not be maintained safely . increased risk of intraoperative bleeding is a serious concern when laparoscopic adrenalectomy is performed in a patient with large tumor . causes of bleeding can be : injuries to adrenal capsule , problems to close the adrenal vein or tears in the inferior cava or renal vein [ table 4 ] . we recommend to dissect the adrenal gland together with the adjacent fat instead of preparation beneath the adrenal capsule . this strategy might prevent injury to and bleeding from the adrenal capsule and diminish the risk of organ manipulation in patients with pheochromocytoma . possible presence of a second adrenal vein should be kept in mind during medial dissection . in case of serious bleeding during a retroperitoneoscopic adrenalectomy , insufflation pressure can safely be increased to 25 mm hg without any risk of co2 -emboly . endoscopic suction should be avoided : significant drop of the retroperitoneal pressure might increase the bleeding . the recent study of the german adrenocortical carcinoma registry group including 152 patients with adrenocortical carcinoma of 10 cm ( 35 laparoscopic and 117 open adrenalectomies ) showed a comparable frequency of tumor capsule laceration and peritoneal carcinomatosis in both groups . also , adjusted recurrence - free survival was not different between laparoscopic and open surgery . other retrospective studies showed enhanced quality of life without impairment of overall survival in patients with adrenocortical carcinoma ( acc ) undergoing laparoscopic surgery . also , local recurrences of acc have been described both , after open and after laparoscopic adrenalectomy . however , some studies reported on worse oncological outcome in patients with acc undergoing laparoscopic adrenalectomy as compared to open surgery . miller et al . compared 17 laparoscopic ( mean tumor size 7 cm ) with 71 open adrenalectomies ( mean tumor size 12.3 cm ) in patients with acc . mean disease - free survival was shorter after laparoscopic adrenalectomy ( 9.6 months vs. 19.2 months ) and local recurrence rate was higher ( 35% vs. 28% ) . thus , long - term outcome in laparoscopically treated patients with acc should be assessed cautiously . patients with preoperatively suspected acc should be informed thoroughly about potential risks and benefits of both surgical techniques . due to a close anatomical relation to spleen , kidney , liver and inferior caval vein , laparoscopic adrenal surgery for large tumors is technically demanding . injury to the adrenal capsule is associated with increased probability of relevant consequences in patients with larger tumors : 23% of group 2 patients presented with pheochromocytoma and 12% had a malignant disease . therefore , surgeons undertaking laparoscopic adrenalectomy in this particular population should have a large experience in laparoscopic adrenal surgery . experience with other , particularly with gastrointestinal laparoscopic procedures might shorten the learning curve . in the present study , 86.5% of the adrenalectomies for tumors > 6 cm were performed by the first author of the study ( a.a . ) after an experience of 127 laparoscopic adrenalectomies and already twelve years experience in laparoscopic colorectal surgery . retroperitoneoscopic adrenalectomy in patient with very large tumors might pose serious additional technical difficulties because of a limited operative field . in obese patients , the prone positioning will lead to even more compression of the retroperitoneal space in spite of high insufflation pressure . thus , laparoscopic transperitoneal adrenalectomy by a lateral approach is preferred in case of tumors larger than 8 cm and in patients with bmi > 40 kg / m at our institution . conventional adrenalectomy is reserved for cases with clear radiological signs of malignancy ( invasion of surrounding structures , evidence of metastases ) and was performed only in 8 cases since 2005 . in our study , duration of surgery was longer and blood loss was slightly larger in patients with tumors > 6 cm as compared to patients with smaller adrenal masses . some recent publications indicated that laparoscopic adrenalectomy can be performed safely for tumors up to 15 cm .. tsuru et al . found no statistically significant difference regarding blood loss , time of surgery and complication rate between patients with tumors < 5 cm ( n = 155 ) and patients with larger tumors ( n = 23 ) , however , their study was smaller . the authors of the latter study recommended that invasion of adjacent structures should serve as an only indication for conventional adrenalectomy . however , it should be weighed against the fact that almost 95% of patients with large adrenal tumors still benefited from the laparoscopic approach . nevertheless , one should not hesitate to convert to conventional adrenalectomy if oncological principles can not be maintained safely . increased risk of intraoperative bleeding is a serious concern when laparoscopic adrenalectomy is performed in a patient with large tumor . causes of bleeding can be : injuries to adrenal capsule , problems to close the adrenal vein or tears in the inferior cava or renal vein [ table 4 ] . we recommend to dissect the adrenal gland together with the adjacent fat instead of preparation beneath the adrenal capsule . this strategy might prevent injury to and bleeding from the adrenal capsule and diminish the risk of organ manipulation in patients with pheochromocytoma . possible presence of a second adrenal vein should be kept in mind during medial dissection . in case of serious bleeding during a retroperitoneoscopic adrenalectomy , insufflation pressure can safely be increased to 25 mm hg without any risk of co2 -emboly . endoscopic suction should be avoided : significant drop of the retroperitoneal pressure might increase the bleeding . the recent study of the german adrenocortical carcinoma registry group including 152 patients with adrenocortical carcinoma of 10 cm ( 35 laparoscopic and 117 open adrenalectomies ) showed a comparable frequency of tumor capsule laceration and peritoneal carcinomatosis in both groups . also , adjusted recurrence - free survival was not different between laparoscopic and open surgery . other retrospective studies showed enhanced quality of life without impairment of overall survival in patients with adrenocortical carcinoma ( acc ) undergoing laparoscopic surgery . also , local recurrences of acc have been described both , after open and after laparoscopic adrenalectomy . however , some studies reported on worse oncological outcome in patients with acc undergoing laparoscopic adrenalectomy as compared to open surgery . miller et al . compared 17 laparoscopic ( mean tumor size 7 cm ) with 71 open adrenalectomies ( mean tumor size 12.3 cm ) in patients with acc . mean disease - free survival was shorter after laparoscopic adrenalectomy ( 9.6 months vs. 19.2 months ) and local recurrence rate was higher ( 35% vs. 28% ) . thus , long - term outcome in laparoscopically treated patients with acc should be assessed cautiously . patients with preoperatively suspected acc should be informed thoroughly about potential risks and benefits of both surgical techniques . minimally invasive adrenalectomy for large adrenal tumors is a technically demanding procedure necessitating appropriate expertise in laparoscopic and oncologic surgery . even in patients with large tumors ( > 6 cm ) , laparoscopic adrenal surgery can be performed by an experienced surgeon at large volume centers with an increased but still acceptable intra- and postoperative morbidity .