fossa navicularis strictures following radical prostatectomy are rare . unlike other anterior urethral strictures , fossa strictures are usually inflammatory or procedure - induced , arising from urethral trauma caused by endoscopic procedures , catheterizations , or subsequent infections . in the literature we describe the incidence of fossa stricture in our rlp series to determine its likely etiologic factors . the data of 424 men undergoing rlp from june 2002 to may 2006 by a single surgeon were prospectively entered into an electronic database . prior to surgery , all men were evaluated , and the following data entered into the database : age , height , weight , american urological association ( aua ) symptom score , urinary bother score , prostate - specific antigen ( psa ) , and pertinent medical history . urinary and functional outcomes were determined on the basis of self - administered questionnaires , including the seven - item international prostate symptom score , and selected questions from the 26-item expanded prostate cancer instrument composite , at the routine 3-month and 9-month follow - up visits . the questionnaire asked whether they wore pads , how many weeks did it take to not need pads , how many weeks needed to return to work , and how many weeks to return to baseline energy levels . a nonclinical research associate ( d.w.s . ) collected the follow - up information . complications were defined by the need for prolongation of hospitalization , the need for a secondary procedure , or rehospitalization within 30  days . all statistical comparisons between the stricture and nonstricture groups as well as between the 18 and 22 french ( f ) catheter groups were two - sided using fisher s exact test and student s t - test for means ( sas ver . multivariate analysis was also performed with a stepwise logistic regression which used the preoperative continuous variables , body mass index ( bmi ) , psa , estimated blood loss ( ebl ) , aua symptom score , bother score , age , and prostate weight ( table  1 ) as independent variables in the prediction of a positive stricture . table  1demographic , clinical , and perioperative data for men reporting strictures versus stricture - free menvariable 
 no stricture 
 standard error ( se)stricture 
 se 
 p - valuepatients ( n)41410age ( year)61.4.0 ( 4379)0.363.8 ( 5171)2.40.29bmi27.0 ( 20.634.9)0.226.3 ( 24.234.0)0.70.52aua symptom score8.6 ( 032)0.47.4 ( 127)1.80.59urinary bother score1.7 ( 06)0.11.6 ( 06)0.50.86preoperative psa ( ng / ml)6.9 ( 0.162.0)0.36.2 ( 1.818.0)1.50.71prostate size ( g)53.1 ( 12.5163.0)1.446.1 ( 20.069.1)3.30.41ebl ( ml)107 ( 25350)2.867.5 ( 25400)16.30.03 

 bmi , body mass index ; aua , american urological association ; psa , prostate - specific antigen ; ebl , estimated blood loss 
 values are the mean , with the range given in parenthesis 
 two - sided fisher s exact test demographic , clinical , and perioperative data for men reporting strictures versus stricture - free men 
 bmi , body mass index ; aua , american urological association ; psa , prostate - specific antigen ; ebl , estimated blood loss 
 values are the mean , with the range given in parenthesis 
 two - sided fisher s exact test all rlps were performed in the same manner with the da vinci surgical system ( intuitive surgical , mountain view , calif . ) . patients are positioned supine in an extreme trendelenburg position and undergo abdominal insufflation with a pneumoperitoneum of 15  mmhg . the standard protocol consists of inserting a silastic urethral catheter at the beginning of the case that is utilized throughout the dissection until completion of the anastomosis . at this point a new 18  f silastic catheter is put in place , and this is generally removed 7  days postoperatively . at case number 35 , however , we switched from an 18 to a 22 f silastic urethral catheter during the dissection as an aid to prevent stapling the urethra . we use a stapling device instead of suturing the dorsal venous complex based on findings from a previous study . in that study , the data demonstrated that the stapler technique provided a more defined apical dissection and a statistically significant reduction in positive margins in patients with organ - confined disease . we switched back to an 18 f catheter at case number 166 due to concerns regarding strictures in the fossa navicularis . fossa strictures were diagnosed based on acute onset of obstructive lower urinary symptoms and bougie a boule calibration . obstructive voiding symptoms included a decreased force of stream , dribbling or splaying , and prolonged voiding . table  1 presents the demographic , clinical , and perioperative data for men reporting strictures versus stricture - free men . the mean follow - up was 26.4  months for stricture patients versus 22.1  months for stricture - free patients and 22.8  months ( range : 3.645.6 months ) for all patients . the groups were comparable for the standard clinical factors , such as age , bmi , aua symptom score , urinary bother score , and preoperative psa level . there was also no difference between the groups in reference to operative time , prostate size , and cardiovascular disease . the stricture - free group , however , had a higher ebl than the stricture group ( p  =  0.03 ) . in addition , none of the patients in the stricture group had any history of a previous endoscopic procedure . multivariate analysis also demonstrated that none of the preoperative continuous variables predicted the presence of strictures ( all p  >  0.18 ) . table  2 outlines the demographic , clinical , and perioperative data for men stratified by catheter size . the 18 and 22 f catheter groups were also comparable for age , bmi , baseline aua symptom score , urinary bother score , preoperative psa , operative time , prostate size , ebl , and complications . the 22 f catheter group , however , had a significantly higher rate of stricture formation . a total of 6.9% of patients developed a stricture using a 22 f catheter versus 0.3% of patients using an 18  f catheter during the intra - operative dissection ( p  <  0.01 ) . the mean length of urethral catheterization was 7.1  days ( range : 78 days ) in the stricture group , with a mean time to stricture development of 50  days ( range : 3493 days ) . one patient in the stricture group developed a bladder neck contracture and another went into acute urinary retention . table  2demographic , clinical data , and perioperative data for 18 and 22 f catheter groupsvariable 
 18 f 
 se22 f 
 se 
 p - valuepatients ( n)293131age ( year)61.1(4679)0.462.2 ( 4378)0.70.14bmi27.0 ( 20.640.0)0.226.80.30.49aua symptom score8.7 ( 035)0.48.2 ( 031)0.60.54urinary bother score1.7 ( 06)0.11.7 ( 06)0.10.93preoperative psa ( ng / ml)6.7 ( 1.131.0)0.37.3 ( 0.162.0)0.60.30prostate size ( g)54.1 ( 12.5163.0)1.850.5 ( 15.0135.0)1.90.21ebl ( ml)109.3 ( 25350)3.298.9 ( 25400)5.50.10fossa stricture190.0002 

 bmi , body mass index ; aua , american urological association ; psa , prostate - specific antigen ; ebl estimated blood loss 
 values are the mean , with the range given in parenthesis 
 two - sided fisher s exact test demographic , clinical data , and perioperative data for 18 and 22 f catheter groups 
 bmi , body mass index ; aua , american urological association ; psa , prostate - specific antigen ; ebl estimated blood loss 
 values are the mean , with the range given in parenthesis 
 two - sided fisher s exact test in addition , urethral reconstruction was required in two of nine patients ( 22% ) who developed strictures with the larger 22 f catheter . only one subject developed a stricture using an 18 f catheter ; he required only soft dilation as treatment . in the present series , all comparisons made by the student s t - test were also examined using the nonparametric wilcoxon rank sum test , with similar conclusions . a thorough review of the literature revealed an absence of papers specifically focused on fossa strictures ; most information relating to these strictures are a secondary thought to more common strictures of the bulbar urethra . it has been reported that , in general , strictures involving the fossa have three distinct etiologic factors : inflammatory , procedure - related , or catheter - induced . inflammatory conditions include balanitis xerotica obliterans ( bxo ) , lichen sclerosis , and an inflammatory variant of vitiligo [ 1 , 36 ] . procedure - related causes are most commonly associated with transurethral resection of the prostate , which has a reported rate of approximately 2.6% . however , we could find no information suggesting that a larger caliber resectoscope was responsible for a greater risk of fossa strictures . the incidence of urethral stricture following cardiovascular surgery in the early 1980s prompted much investigation and was thought to arise from catheter toxicity and urethral ischemia [ 9 , 10 ] . however , these strictures usually affected the anterior urethra and none solely involved the fossa navicularis . abdel - hakim and elhilali [ 11 , 12 ] found some evidence for urethral ischemia in stricture cases utilizing strain gauge plethysmography to determine penile - brachial indexes . in addition , nacey   demonstrated a significantly increased incidence of urethral strictures following catheterization with silastic catheters compared to silicone catheters in a controlled randomized prospective study of patients undergoing elective cardiac surgery . other experimental and clinical studies demonstrated that latex catheters were more toxic than non - latex catheters [ 1418 ] . as noted above , there were essentially no published reports of fossa strictures following rlp and very little information regarding its etiology . we initially looked at factors such as age , medical diseases , bmi , ebl , operative length , among others . although ebl was noted to be significantly higher in stricture - free men , its association with stricture formation is unclear since the ebl between the two different catheter groups was essentially the same . with no obvious factor we were concerned that the electrical current leaving the monopolar tip might potentially be transmitted down the catheter in the urethra and injure the fossa . in response to this potential source of injury , the grounding pad was moved from the upper thigh ( i.e. , adjacent to the penis ) to the thorax . however , the fossa strictures continued . we next turned to the possibility that the 22 f caliber of the urethral catheter might be responsible . at case number 35 we had switched from our standard 18 f catheter to a 22 f caliber in an attempt to avoid inadvertent stapling of the urethra . at case number 166 remarkably , our data suggest  and continued experience supports the data  that the 22 f silastic urethral catheter is the likely etiology . the use of a 22 f silastic urethral catheter during the intra - operative dissection would appear to have increased the risk for fossa stricture 20-fold relative to the 18 f catheter . however , definitive empirical proof that the larger sized catheter is the etiological factor is absent ; it may be that in addition to catheter size , the combination of extreme trendelenburg position and the pneumoperitoneum associated with rlp are other contributing factors . this combination of factors may account for the lack of reports on similar stricture experiences among the large volume of articles published on rlp and cystectomy . the mean time to fossa the strictures were not equally distributed over time , with the majority of strictures diagnosed by postoperative day 50 . we do not have an explanation why some men developed strictures after one month and others after 3  months . as table  1 demonstrates , there were no other obvious differences between the two groups . two of ten strictures ( both in the 22 f group ) subsequently required open reconstruction , whereas 80% resolved with soft dilations continued over a 3- to 6-month interval following the development of the fossa stricture . in summary , an 18 f catheter is sufficient to drain the bladder safely . a larger urethral catheter size during the intra - operative dissection in rlp appears to increase the risk for fossa navicularis stricture .
fossa navicularis strictures following radical prostatectomy are reported infrequently . 
 we recently experienced a series of fossa strictures following robotic - assisted laparoscopic prostatectomy ( rlp ) . we describe herein our experience to prevent fossa strictures and to determine its etiologic factors . from june 2002 
 to may 2006 , 424 patients underwent robotic - assisted laparoscopic prostatectomy with the da vinci surgical system . 
 fossa strictures were diagnosed based on the acute onset of obstructive voiding symptoms and bougie calibration . during our series , we switched from the intra - operative use of an 18 french ( f ) catheter to that of a 22 f one to avoid inadvertent stapling of the urethra when dividing the dorsal venous complex . after we observed a high incidence of fossa strictures , we reverted back to 18 f catheters during surgery . 
 all patients had an 18 f catheter indwelling for 1  week after surgery . 
 parameters were evaluated using fisher s exact test and student s t - test for means . 
 the 18 f catheter group of patients ( n  =  293 ) developed one fossa stricture , whereas the 22 f catheter group ( n  =  131 ) developed nine fossa strictures ( p  <  0.01 ) . 
 the fossa stricture rate in the 18 f group was 0.3% versus 6.9% in the 22 f group . 
 the two groups had no differences in age , body mass index , cardiovascular disease , american urological association symptom score , urinary bother score , preoperative prostate - specific antigen , operative time , estimated blood loss , cautery use , prostate size , or catheterization time . based on these results , a larger urethral catheter size  20 f versus 18 f  during the intra - operative dissection would appear to increase the risk for fossa stricture by more than 20-fold .