the estimated incidence of bnc after open retropubic radical prostatectomy ( rrp ) ranges from 3% to 26% [ 1 - 8 ] .
robot - assisted laparoscopic radical prostatectomy ( ralp ) is becoming a more frequently performed procedure because it clearly has a lower rate of postoperative complications than rrp . in particular , the incidence of bnc after ralp ranges from 0.6% to 3% [ 9 - 12 ] .
several case reports have suggested that rrp , pure laparoscopic radical prostatectomy ( lrp ) , and ralp are associated with complications related to the use of surgical clips , including bnc and the formation of bladder stones [ 13 - 19 ] .
the purpose of this study was to evaluate the surgical clip - related complications that occurred after rrp , lrp , and ralp in our institution .
in our institution , rrp was the method of choice for radical prostatectomy until august 2005 , when the first case of lrp was performed .
thereafter , lrp was frequently performed between august 2005 and april 2008 . from may 2008
we retrospectively reviewed a database that has been maintained in our institution of the clinical , surgical , and pathological parameters of these procedures .
we reviewed a total of 641 cases who underwent radical prostatectomy at our institution between january 2006 and april 2009 .
of the 641 patients , 439 , 49 , and 153 underwent rrp , lrp , and ralp , respectively . in all cases ,
the median follow - up time for the entire cohort was 19.0 months ( range , 1 - 42 months ) .
of the rrp , lrp , and ralp patients , 25 ( 5.7% ) , 1 ( 2.0% ) , and 2 ( 1.3% ) had bnc , respectively , and 2 of the rrp patients developed a bladder stone . in total , 6 patients with complications related to the use of surgical clips were identified in the cohort .
cystoscopic examination of patient 2 indicated bnc and the presence of a metal clip protruding into the urethra through the urethrovesical anastomosis at 4 o'clock ( fig .
patients 3 and 4 were both found to have a hem - o - lok clip in the bladder neck ( fig .
their bncs were resolved after a single urethral dilatation , after which the symptoms disappeared .
patients 5 and 6 were found to have a bladder stone that had formed around the metal clip in the bladder ( fig .
retrospective re - evaluation of the kidney , ureter and bladder x - ray ( kub ) revealed the metal clip in the bladder region ( patient 5 : fig .
4 ) . during the follow - up , neither patient exhibited signs of bladder stone recurrence . in all patients ,
one study based on a patient self - reported questionnaire , which revealed that 25.9% of rrp patients reported at least one episode of bnc that required treatment , was unable to identify factors that could predict the occurrence of bnc .
in contrast , surya et al reported that many factors promote the occurrence of bnc after rrp , including urinary extravasation , excessive blood loss , and previous bladder neck surgery .
similarly , thiel et al found that 17.5% of rrp patients required stricture dilatation by a mean time of 6 months after surgery and revealed that increased age and increased blood loss were statistically associated with stricture formation .
recently , erickson et al suggested that improved surgical technique and increased surgeon experience appear to be the most important factors that reduce the incidence of bnc .
huang and lepor added a history of previous transurethral resection of the prostate , pelvic external beam radiotherapy , and a hypertrophic healing response to the risk factors for bnc after rrp .
another study found that of the 11.1% of patients who developed bnc after rrp , the biggest risk factor was current smoking ( 26% ) , with comorbidities such as hypertension , coronary artery disease , and diabetes also being significantly associated with the formation of bnc .
the investigators hypothesized that local ischemia of the urethra and bladder neck caused by microvascular disease may lead to poor anastomotic healing and scar formation .
similarly , the incidence of bnc in our cohort of 153 consecutive ralp patients was 1.3% .
it is not clear why the rate of bnc after ralp is significantly lower than that quoted in the rrp literature , but msezane et al suggested that it may be due to the running anastomosis , better visualization , improved instrument maneuverability , and decreased blood loss .
moreover , a comprehensive review of the literature comparing rrp , lrp , and ralp revealed that higher estimated blood loss was a significant factor in the development of bnc .
recently , a study comparing rrp and ralp suggested that the predisposing causes of bnc are likely to be the combination of a fixed circular bladder stomatization with the subsequent healing of the stoma anastomosis to the urethra .
the present study shows that bnc may also arise as a result of clip migration .
this has also been observed in the literature ( table 2 ) , although it should be noted that most reported complications with surgical clips relate to hemorrhage .
long et al reported the first case of metal clip migration - induced bnc after rrp in a patient who had suffered multiple episodes of urinary retention and had undergone several failed urethrotomies .
later , blumenthal et al reported the first case report of hem - o - lok migration into the vesicourethral anastomosis after ralp .
those authors believe that the relationship between surgical clip migration into the anastomosis and bnc formation is not coincidental ; they postulated that the physical disruption of the anastomosis by the surgical clip contributed to poor healing and may have elicited an inflammatory reaction .
tunnard et al then described a case of a hem - o - lok clip - related complication following lrp : during bladder neck dilatation for a tight bladder neck , a hem - o - lok was found in the bladder , having migrated from the urethrovesical anastomosis .
it was removed successfully but a repeat cystoscopy 3 months later revealed another hem - o - lok device that had eroded through the vesicourethral anastomosis .
this was removed successfully with the aid of a holmium laser . in the present study , stones developed around the surgical clip in 2 patients after rrp .
other studies have also reported surgical clip - related complications other than bnc ( table 2 ) .
these include the case described by palou et al of severe perineal pain after rrp due to the protrusion of a metal clip into the urethra at the urethrovesical anastomosis , and the case of banks et al , in which the migration of a hem - o - lok clip into the bladder led to stone formation after lrp .
there was also a recent report by kadekawa et al of a case in which a metal clip had migrated into the urinary bladder after rrp .
it was hypothesized that inflammation had arisen around the urinary bladder or vesicourethral anastomosis and that this also involved the metal clip , which then eroded the bladder wall and eventually migrated into the bladder .
in addition , mora et al reported a case of intravesical migration and subsequent calculus formation with the spontaneous expulsion of a hem - o - lok clip after lrp .
these findings suggest that foreign bodies in the bladder can act as a nidus for bladder stone formation owing to the presence of persistent chronic inflammation .
the mechanism underlying the migration of a surgical clip into the urinary tract is unclear . in our series , the rate of bnc after ralp was significantly lower than that after rrp .
because improvements in outcomes are related to temporal improvements in particular procedures , this trend might account for some improvement in outcome in the ralp group .
it appears that surgical clips are prone to migration and may cause , or significantly contribute to , bnc or the formation of bladder stones after radical prostatectomy .
these findings raise questions regarding the use of foreign bodies in close proximity to the vesicourethral anastomosis during radical prostatectomy . at the very least ,
they indicate that care must be taken with the surgical clips used for inducing hemostasis near the apex of the prostate in radical prostatectomy .
in addition , because the incidence of bnc after ralp is low , when unexplained voiding difficulty occurs after ralp , one should suspect that a hem - o - lok clip has migrated , especially because hem - o - lok clips can not be detected on x - rays .
 purposethe aim of this study was to describe the surgical clip - related complications that can occur after open retropubic prostatectomy ( rrp ) , pure laparoscopic prostatectomy ( lrp ) , and robot - assisted laparoscopic radical prostatectomy ( ralp).materials and methodsa database of 641 patients who underwent rrp ( n=439 ) , lrp ( n=49 ) , and ralp ( n=153 ) at our institution between january 2006 and april 2009 was reviewed to identify patients with complications related to the use of surgical clips . 
 the median follow - up time for the entire cohort was 19.0 months ( range , 1 - 42 months).resultsof the 641 patients , 25 ( 5.7% ) , 1 ( 2.0% ) , and 2 ( 1.3% ) had a bladder neck contracture after rrp , lrp , and ralp , respectively . 
 two rrp patients had a bladder stone . in total , 
 6 patients had surgical clip - related complications . 
 metal clip migration was associated with 2 ( 8% ) of the 25 rrp cases of bladder neck contracture and both ( 100% ) of the rrp cases of bladder stone . moreover , 
 both ( 100% ) of the ralp cases of bladder neck contractures were associated with hem - o - lok clip migration into the anastomotic site.conclusionssurgical clips are prone to migration and may cause , or significantly contribute to , bladder neck contracture or the formation of bladder stones after radical prostatectomy . 
 these findings also suggest that because the incidence of bladder neck contracture after ralp is low , the migration of hem - o - lok clips should be suspected when voiding difficulty occurs after ralp . 