benign prostatic hyperplasia ( bph ) is the most common disorder originating in the lower urinary tract in men over the age of 50 . in the last 20 years a number of modern methods of surgical treatment have been developed to treat this common condition . for years the gold standard procedure for treatment of bph has been the transurethral resection of the prostate ( turp ) . however , this method is associated with a variety of complications affecting > 18% of patients . bleeding during and after the procedure , post - turp syndrome , secondary urethral strictures and repeated reoperations resulting from urinary incontinence are a select few , which , along with its steep learning curve , have necessitated the search for and development of alternative methods of therapy . the application of laser for the treatment of bph was first attempted in the 1980s . since then the popularity of this method has grown continuously , along with the advancement of associated interventional devices ( from coagulation to cutting and vaporization methods ) . currently , two different laser systems have come to dominate urological surgery : holmium laser  holmium - yttrium - aluminium - garnet ( ho : yag )  applied primarily in ablation , enucleation and resection of prostatic tissue ( including the breakdown of deposits in the urinary tract ) and green laser  potassium - titanyl - phosphate ( ktp )  serving exclusively the vaporization of prostate adenoma . the treatment of bph using the 80-w potassium - titanyl - phosphate laser ( ktp ) was first reported in 1997 . the first procedure in poland was carried out in 2013 by professor jeromin in d . in comparison to previous technology ( nd : yag laser ) , the wavelength of the ktp laser ( 532 nm ) has been halved , placing it in the green electromagnetic spectrum ( greenlight - laser ) . the result is a completely different optical and energetic interaction in contrast to other laser types . combing the high average power of a quasi - continuous wave laser ( 80 w ) with the high peak power delivery within each micro - pulse ( up to 280 w ) offers efficient vaporization of prostate tissue . the short duration of each laser beam pulse ( 0.25 s ) limits the thermal effect on deeper - lying tissue . ktp laser energy is selectively absorbed by hemoglobin ( and not by water ) , which , at this wavelength , has a very high absorption coefficient and therefore penetrates prostate tissue to a maximal depth of 0.7 mm . this leads to immediate vaporization of prostatic tissue [ 4 , 5 , 6 , 7 ] . though the laser energy penetrates to a tissue depth of only 0.8 mm , the thermal effect spreads within a 510 mm radius from the point of vaporization . thermal damage of the external sphincter is a distinct risk , especially when the prostate adenoma is considerably enlarged beyond the verumontanum , approaching the above - mentioned sphincter . numerous authors have suggested that the degree and frequency of postoperative urinary incontinence is strongly dependent on the age of the patient , but also , and perhaps more significantly , on prostate size , forcing the operator to intervene in the proximity of the external sphincter muscle . the goal of this study was to assess the risk of thermal damage to the external sphincter of the urethra in men undergoing greenlight laser vaporization of bph . 98 consecutive men with lower urinary tract symptoms due to bph were qualified for photoselective ktp laser vaporization of the prostate ( pvp ) . inclusion criteria were as follows : clinical symptoms of boo progressing or refractory to conservative treatment , international prostate symptom score ( ipss ) of > 10 or urinary retention , prostate volume of 4080 ml measured by transabdominal ultrasound , the presence of enlarged prostate adenoma at the level of verumontanum confirmed at urethroscopy directly before pvp . exclusion criteria were as follows : active urinary tract infection , suspicion of prostate cancer , urethral stricture , previous urethral surgery , neurological disorders , lack of informed consent to participate in the study . local review board approved study protocol . among 98 initially screened men , inclusion criterion of enlarged prostate adenoma at the level of verumontanum eventually 66 consecutive patients were assigned into two study groups , based on consecutive patient numbers . patients with even and odd numbers were assigned to the study group a and the study group b , respectively . in the group a , patients underwent vaporization prostatectomy , seemingly incomplete , with the termination of the procedure at the level of the verumontanum . the remaining fragments of the lateral lobes extending in various degrees beyond the seminal colliculus / veromontanum were left intact . in the group b , the vaporization procedure was also discontinued at the level of the verumontanum , however , the remaining fragments of the lateral lobes of the adenoma were resected by means of the standard turp method ( of course after changing endoscopic equipment ) . all procedures were performed by the same surgeon , using a single 80-w green light laser fiber ( american medical systems ) , water - cooled , emitting a monochromatic light source , operating at a 532 nm wavelength . all patients undergone full urological evaluation before treatment , including transabdominal ultrasound ( trus ) measurement of prostate volume performed by the same radiologist , accounting for median ( iii ) prostate lobe and retention , determination of prostate - specific antigen ( psa ) , measurement of maximum flow rate qmax ( except in patients with complete urinary retention ) and digital rectal examination ( dre ) . all patients were also asked to complete the ipss and ql questionnaire , and gave their informed consent to participate in the study . primary end - points of the study were change in continence status , urinary flow ( qmax ) , post void urine retention ( pvr ) , international prostate symptom score ( ipss ) , including 7-scale ( 0-delighted , 6-terrible ) quality of life assessment ( qol ) . secondary study end - points were surgery time , bleeding rate , catheterization time , storage symptoms in postoperative course and surgical complications . the data , obtained during the course of the study , were analyzed using statistica 10.0 . normal distribution of all quantitative variables was confirmed with the use of the shapiro - wilk test , while homogeneity of variance was tested according to levene s formula . the student s t - test was used to compare the results between the groups , when achieving a positive outcome of both afore - mentioned tests . in case of a negative outcome , per protocol analysis was eventually performed in 60 patients , including 32 and 28 patients in group a and b , respectively . from the group of 66 randomized men 5 patients were lost in follow - up ( 1 patient from group a and 4 patients from group b ) and one patient from group b died from cardiac insufficiency not related to urological procedure . mean psa was 2.47 ng / ml and 2.68 ng / ml in group a and b , respectively . in the single case of elevated psa ( 25 ng / ml ) , two series of trus - guided prostate biopsies were performed to rule out prostate cancer . prior to the procedure , attention was paid to the presence of an median ( iii ) lobe protruding into the bladder , posing further difficulties in performing vaporization and thus prolonging the operation time . this was observed in a total of 18 patients ( 29% ) across both groups . general characteristics of patients in groups a and b psa  prostate specific antigen ; ipss  international prostate symptom score ; qol  quality of life ; qmax  maximal urinary flow rate during the 8-week follow - up no patient reported urinary incontinence . results in primary end - points of the study are presented in table 2 . in postoperative studies of both 24 hours and 68 weeks after treatment , there was a significant symptomatic decline in accordance to the questionnaire results , and a significant increase in urinary flow . postoperative results ipss  international prostate symptom score ; qol  quality of life ; qmax  maximal urinary flow rate surgery time was 80.3 min ( 60120 ) in group a and 101.3 min ( 85150 ) in group b. the difference in operation times was observable both clinically and statistically ( p = 0.00 ) , attributable to the necessary variation of technique in group b ( apparatus and irrigation fluid change ) . only a few patients required general anesthesia , as a result of the presence of concurrent illness . assessment of bleeding during the procedure was carried out by the operator , according to a self - devised scale : 0  represented no bleeding , 1  bleeding requiring coagulation during the procedure ( without the need for blood transfusion , with no drop in hemoglobin ) , 2  persistent bleeding despite coagulation postoperatively ( without the need for blood transfusion , but with a 12 unit drop in hemoglobin ) and 3  bleeding requiring either plasma extract or re - coagulation and blood transfusion ( where the drop in the hemoglobin exceeds 2 units ) . a , no bleeding ( 0 on the bleeding scale ) was clearly encountered more frequently , whereas group b was evidently more frequently characterized by persistent bleeding despite coagulation attempts , but without the need for further intervention ( p = 0.00 ) . after surgery , an 18 ch foley catheter was inserted and left for 24 hours . in 4 patients from group b , a three - way dufour 20 ch catheter was left due to bleeding . the average holding time , of the catheter after surgery , in group a was significantly shorter in comparison to group b ( 29.1 hours vs. 37.2 hours , p = 0.04 ) . all patients in group a had their catheters removed 24 hours after treatment . however , 4 men required reinsertion of a catheter for another 24 hours due to urine retention . two patients , although urinating independently , required catheter reinsertion due to significant urine retention . a catheter was maintained maximally for 72 hours . 2 patients from group b required re - coagulation due to bleeding within the first 24 hours after surgery . 16 patients had a catheter maintained for a longer period : due to bleeding  9 patients , repeated / significant urine retention  7 patients . all patients who underwent surgery , had urinary flow and retention tests performed before leaving the hospital . maximal urinary flow and retention tests were performed once again , and patients were asked to complete an ipss and ql questionnaire . assessment of bleeding in operated patients the major patient complaints encountered at follow - up ( in some even earlier voluntarily ) were sudden urge to urinate , groin and urethral pain . 12 patients from group a ( 36% ) and 9 ( 31% ) from group b reported the above - mentioned complaints . patients were prescribed alpha - blockers with or without anti - inflammatory medication , as well as cholinolytics . 4 patients ( 6.5% ) ( both groups  under further observation ) were re - admitted to the ward due to urinary bladder neck and/or urethra narrowing . one patient ( from group a ) was reoperated after 14 months , performing turp . none of the patients , from either of the groups , complained of problems with urinary incontinence . the frequency of reporting any of these symptoms did not differ between groups ( p > 0.05 ) . we performed a prospective randomized trial assessing the risk of functional complications related to pvp in the region of urethral external sphincter . the depth of tissue injury is proven to be much deeper than visible during endoscopy , what makes injury to the urethral external sphincter possible [ 6 , 7 ] . the main problem considered by our study , urinary incontinence , following 80w ktp laser vaporization of the prostate , was not observed in any patient . overall , 100% patients were found to be continent postoperatively , regardless of the methodology used . we are aware that our patients were selected on the basis of prostate volume , though all satisfied the criteria of our trial  prostate adenoma reaching or slightly exceeding the level of the verumontanum . some authors highlight the fact that a significantly enlarged prostate , along with the patient s advanced age , are predisposing factors for developing postoperative complications , such as urinary incontinence , associated with the  thermal margins accompanying laser vaporization . in group b patients , the significantly prolonged operation time is attributable to the necessary endoscopic apparatus and irrigation fluid change . following classic turp , even partial , problems with hemostasis the average holding time of the catheter after surgery in this group was consequently longer . the supplementary electroresection had no impact on either urinary flow ( though worse 24 hours postoperatively than in group a , these may be due to greater tissue swelling ) or ipss and qol parameters . these are most likely associated with tissue reactions after laser light exposure and a significant degree of neurological receptor irritation [ 9 , 10 ] . late complications occurred in 5 patients ( 8% ) , resulting in further surgical intervention . in other trials , this percentage was slightly higher , reaching even 14% , but it should be noted that we are well aware of the number and specificity of our patients . where the prostate lobes of a large bph extend beyond the verumontanum , the procedure may be interrupted at the level of the verumontanum without compromising urodynamic parameters or patient s well being . additional resection of the lateral lobes of the prostatic hyperplasia using traditional methods is only associated with an elevated risk of bleeding during and after the procedure , prolongation of operation time , increased urinary catheterization times postoperatively , without affecting patients urodynamic and ipps and ql parameters . laser vaporization for treatment of bph is safe and effective , with no significant effect on the risk of urinary incontinence in comparison to traditional methods .