minimally invasive partial nephrectomy for small renal masses was reported to have excellent functional and oncologic outcomes , with 5 to 10 years cancer - specific survival rates of 95% to 100% [ 1 - 4 ] . among the various factors that are important for preserving renal function after partial nephrectomy , the most important factors are to maximize the amount of functional renal parenchyma , and to reduce warm ischemia time . in october 2010
, the zero ischemia technique was introduced to eliminate global renal ischemia during rapn . according to the protocol ,
dedicated renal protocol computed tomographic ( ct ) scan with 0.5 mm slice thickness was essential to delineate tumor location , intrarenal extension , and proximity to collecting system .
in addition , reconstruction of renal tumors were performed manually using mainly arterial phase images with the corresponding venous phases , and required the joint interpretation by an experienced urologist and a radiology technician .
furthermore , placement of a disposable neurovascular aneurysm microsurgical bulldog clamp ( occlusion power , 0.39 n ) on the targeted arterial branch was needed to confirm tumor devascularization .
zero ischemia rapn was a novel technique developed to bring about a paradigm shift from conventional partial nephrectomy .
however , 2 years had lapsed since zero ischemia rapn was first reported and there was a paucity of literature reporting on this technique .
this may be attributed to the technically challenging nature of the procedure and the need for specialized instruments and equipment , making this approach less readily adopted by other centers . in our present study , kidney donor ct angiography which is widely available in many centers is used to distinguish the tumor with its arterial anatomy from the surrounding normal parenchyma .
conventional laparoscopic bulldog clamps were applied to tertiary arteries supplying the tumour instead of disposable microsurgical clamps .
the purpose of this study was to evaluate the safety and feasibility of a simplified zero ischemia technique using kidney donor ct angiography and conventional laparoscopic bulldog clamps in patients with renal hilar tumors .
a total of seven consecutive patients with enhancing renal masses with preoperatively reconstructed 3-dimentional ( 3d ) ct images underwent robot - assisted partial nephrectomies ( rapns ) by a single experienced surgeon in a tertiary institution between january 2012 and may 2012 . institutional review board approval was obtained .
preoperative imaging was done using a 64 slice multidetector - row ct scanner ( ge medical systems , milwaukee , wi , usa ) .
triphasic ct scanning consisting of non - contrasted , arterial , and cortico - medullary phases , with 1 mm slice thickness was performed . using the standard commercial workstation of the ct scanner ( aw volume - share 2 , ge medical systems ) , the radiologist reconstructed 3d images to identify the renal arterial anatomy and the relationship between the renal artery and the tumor within the renal parenchyma .
we reconstructed three components using a surface rendering technique and then fused them into a 3d volume data set : the renal artery , renal parenchyma , and tumor .
the renal artery and tumor were reconstructed from images during the arterial phase . the total time required for reconstruction was one hour per case .
the fused 3d volume - rendered data - set was viewable at all angles during preoperative planning ( figs .
after the colon was taken down , the perirenal fat was meticulously dissected to reveal the renal hilar vessels in the retroperitoneal space . except for clamping the higher order renal artery ,
the operative procedures of zero ischemia rapn procedures were basically identical to those of conventional rapn .
after hilar dissection , the artery feeding the tumor that was revealed by the 3d reconstruction images was carefully dissected and isolated using small silicone vessel loops ( aspen surgical products , caledonia , mi , usa ) ( fig .
with traction of small silicone vessel loop on the tumor feeding artery , the absence of blood flow in the tumour and the tumour depth were confirmed with intraoperative doppler ultrasonography .
the tertiary renal artery was selectively clamped with small conventional laparoscopic bulldog clamps ( atraumatic endo vessel clips , braun aesculap , germany ) ( fig .
2b ) . in all seven cases , clamping of the main renal artery was not performed .
radial incision of the parenchyma was not needed to locate the tertiary branches , and there was little venous backflow during tumor excision . in cases where there were bleeding from cut vessels on dissection of the renal parenchyma , compression of the vessel with the suction tip
the exposed collecting system and vessels were repaired with running 3 - 0 vicryl sutures .
second layer renorrhaphy was performed using the sliding hemolok technique described by benway et al . .
surgical bolster was not interposed , but the suture line was covered with surgicel ( ethicon , somerville , nj , usa ) and floseal ( baxter inc . , deerfield , il , usa ) .
all statistical analyses were performed using the pasw ver . 18.0 ( ibm co. , armonk , ny , usa ) and a p - value<0.05 was considered statistical significant .
preoperative imaging was done using a 64 slice multidetector - row ct scanner ( ge medical systems , milwaukee , wi , usa ) .
triphasic ct scanning consisting of non - contrasted , arterial , and cortico - medullary phases , with 1 mm slice thickness was performed . using the standard commercial workstation of the ct scanner ( aw volume - share 2 , ge medical systems ) , the radiologist reconstructed 3d images to identify the renal arterial anatomy and the relationship between the renal artery and the tumor within the renal parenchyma .
we reconstructed three components using a surface rendering technique and then fused them into a 3d volume data set : the renal artery , renal parenchyma , and tumor .
the renal artery and tumor were reconstructed from images during the arterial phase . the total time required for reconstruction was one hour per case .
the fused 3d volume - rendered data - set was viewable at all angles during preoperative planning ( figs .
after the colon was taken down , the perirenal fat was meticulously dissected to reveal the renal hilar vessels in the retroperitoneal space . except for clamping the higher order renal artery ,
the operative procedures of zero ischemia rapn procedures were basically identical to those of conventional rapn .
after hilar dissection , the artery feeding the tumor that was revealed by the 3d reconstruction images was carefully dissected and isolated using small silicone vessel loops ( aspen surgical products , caledonia , mi , usa ) ( fig .
with traction of small silicone vessel loop on the tumor feeding artery , the absence of blood flow in the tumour and the tumour depth were confirmed with intraoperative doppler ultrasonography .
the tertiary renal artery was selectively clamped with small conventional laparoscopic bulldog clamps ( atraumatic endo vessel clips , braun aesculap , germany ) ( fig .
2b ) . in all seven cases , clamping of the main renal artery was not performed .
radial incision of the parenchyma was not needed to locate the tertiary branches , and there was little venous backflow during tumor excision . in cases where there were bleeding from cut vessels on dissection of the renal parenchyma , compression of the vessel with the suction tip
the exposed collecting system and vessels were repaired with running 3 - 0 vicryl sutures .
second layer renorrhaphy was performed using the sliding hemolok technique described by benway et al . .
surgical bolster was not interposed , but the suture line was covered with surgicel ( ethicon , somerville , nj , usa ) and floseal ( baxter inc . , deerfield , il , usa ) .
18.0 ( ibm co. , armonk , ny , usa ) and a p - value<0.05 was considered statistical significant .
seven cases of rapn were performed by a single experienced surgeon who had previous experience in more than 150 rapn cases .
there was a high proportion high padua ( preoperative aspects and dimensions used for an anatomical )   scored ( > 10 ) cancer ( 57.1% ) and the mean radius , exophytic / endophytic , nearness to collecting system or sinus , anterior / posterior and location relative to polar lines ( r.e.n.a.l . )
the unclassified rcc was reported as likely clear cell papillary type rcc , but was not perfectly compatible with the criteria by using various immunohistochemical stains .
4 renal tumors were of high fuhrman grades and 1 tumor had invaded the perirenal fat .
repair of the pelvocalyceal system was performed in 6 cases and a bolster was not used in all seven cases .
however , there were minor complications including one drain site wound infection , one urine leak and one postoperative fever that spontaneously subsided ( clavien classification i ) .
the mean estimated glomerular filtration rate ( egfr ) percent change at 3 months postoperative was 5.8% ( range , -17.1% to 15.27% ) which was not statistically significant ( p=0.393 ) . as reported in table 3 , comparing to preoperative egfr , the egfr changes during each follow - up were not significantly different .
, our series seemed to have shorter total operative time and better egfr , but higher estimated blood loss and hospital stay ( table 1 ) .
nephron sparing surgery has been accepted as the gold standard treatment for clinical stage t1 renal tumors .
several studies reported that local recurrence and distant metastasis were not related to the width of resection margin .
currently , minimally invasive techniques have been developed to reduce warm ischemic time and to preserve functional renal volume in partial nephrectomy .
these techniques include nonclamping method for exophytic small masses , early unclamping after excision of mass and suture techniques with nonhilar clamping .
two years ago , gill et al .   presented a technically challenging zero ischemia technique in an attempt to maximize renal function postoperatively .
zero ischemia rapn is based on anatomical vascular microdissection of tertiary and higher order tumor feeding arterial branches . by scrutinizing 3d reconstructed images of the renal tumor , a neurosurgical aneurysm microbulldog ( bear disposable vascular clamp )
was placed on the tumor specific arterial branch to selectively devascularize the tumor . however , acquiring the 3d reconstruction images was labor - intensive and time - consuming and had to be manually performed by an experienced urologist and a radiology technician and typically taking three hours .
in addition , the application of the disposable microsurgical clamps was difficult and required technical expertise in laparoscopy .
in addition , these clamps were easily mishandled and can be easily lost in the abdominal space .
our vascular microdissection techniques were similar to the zero ischemia technique reported by gill et al .
however , we modified our techniques and protocol to overcome two challenges of gill et al .
firstly , we utilized a conventional kidney donor ct angiography which is readily available in many centers to provide 3d images and video clips using 1 mm slices ( fig .
1 ) . the reconstruction took an hour and was performed only by a radiology technician , decreasing the radiologist 's and urologist 's workloads .
secondly , we used standard conventional laparoscopic bulldog clamps which were applied by the patient - side assistant for the super - selective clamping of tertiary arteries . for the safety reason , these were also tagged with threads so that they will not be lost in the abdomen in the event of accidental slippage .
these changes made the technique more readily accessible for most centers already performing robotic partial nephrectomies . to prove the feasibility and safety of our technique
, this study analysed seven cases of simplified zero ischemia rapn in a high volume tertiary institution .
the main goal of zero ischemia technique is to avoid global renal ischemia and reperfusion injury , which causes renal function deterioration .
rogers et al .   reported their rapn series for hilar tumors in 11 patients with a mean warm ischemia time of 28.9 minutes and mean postoperative egfr change of -8 ml / min/1.73 m. abreu et al .  
reported their robotic partial nephrectomy series of 7 patients with hilar tumours , with mean r.e.n.a.l .
the postoperative egfr change was 1.3 ml / min/1.73 m , mean hospital stay was 4.1 days and the total operation time was 237 minutes . in our present study , we reported better total operation time and absolute renal function change , but longer hospital stay and lower nephrometry scores . in comparing length of hospitalization , the practical effect of korean national health insurance system
as most of the patients ' medical expenses during hospitalization were reimbursed , the majority of patients in korea do not return home until they could resume normal activities . despite the small numbers , this study showed that our simplified zero ischemia technique offered good perioperative outcomes .
in addition , there were no severe complications and positive surgical margins in our series .
we showed that zero ischemia rapn can be safely performed in patients with hilar tumors , even in highly complex ( padua scores9 ) tumours .
patients with compromised renal function and young patients who have long life expectancy are good candidates for zero ischemia rapn .
selective clamping of the tumor feeding artery could prevent bleeding from the resected margins and reduces global reperfusion injuries .
however the technical skills involved in skeletonizing the renal artery branches and selectively occluding them are challenging .
the purpose of this paper is to provide a simplified and more easily adoptable version of the zero ischemia technique .
even though the present study comprises of a small number , we showed that our simplified technique is safe and feasible . the time and expertise needed for the acquisition of the 3d reconstructed images
is reduced and can be reproduced in many centers as the donor ct angiography , which we used in our protocol , is widely available .
furthermore , we showed that our simplified zero ischemia technique could be successfully performed in highly complex hilar tumors ( padua score 11 ) with well - preserved postoperative renal functions and minimal complications .
our zero ischemia technique can be used by most surgeons who are already performing rapn .
longer term and larger randomized studies will be needed before consensus for the indications and benefits of zero ischemia partial nephrectomy can be established .
this study demonstrated the safety and feasibility of a simplified zero ischemia rapn technique . in cases of complex renal hilar tumors , our initial experience revealed no intraoperative complications , as well as optimally preserving post - operative renal functions compared to contemporary series .
zero ischemia is a valuable technique that can shift the current paradigm of partial nephrectomy . starting with the present study , this technically challenging procedure requires more simplification and availability .
 purposeto evaluate the safety and feasibility of a simplified zero ischemia technique using kidney donor computed tomographic ( ct ) angiography and conventional laparoscopic bulldog clamps.materials and methodswe conducted a review of seven robot - assisted partial nephrectomies ( rapns ) performed by a single surgeon from january 2012 to may 2012 . using a simplified protocol of 3-dimentional reconstruction , tertiary arterial branches supplying the tumor 
 were selectively clamped prior to resection . 
 we used conventional laparoscopic bulldog clamps instead of microsurgical vessel clamps . 
 the patients ' demographic information , perioperative outcomes , pathologic outcomes and pre- and postoperative renal functions up to 3 months follow - up were analyzed.resultsrapn were successfully performed for seven complex renal hilar tumors . 
 there were no significant differences in the total operation time , estimated blood loss or postoperative outcomes compared with published literature on standard rapn . 
 negative surgical margins were reported in all cases.conclusionswe presented a simplified - zero ischemia technique using kidney donor ct angiography and conventional laparoscopic bulldog clamps . we have also demonstrated its safety and feasibility in patients with complex renal hilar tumors . 
 this modified technique can be easily adopted by most surgeons who are currently performing rapn . 
INTRODUCTION
MATERIALS AND METHODS
1. 3D reconstruction procedure
2. Surgical procedures
3. Statistical analysis
RESULTS
DISCUSSION
CONCLUSIONS
Supplementary Material