intraoperative blood loss is one the most commonly used parameters to assess the safety of surgical procedures . available data regarding laparoscopic radical prostatectomy ( lrp ) indicates unambiguously that the surgery is safe , also in terms of blood loss [ 1 , 2 ] . what is more , reduced blood loss remains one of crucial advantage of lrp when compared with open radical prostatectomy [ 3 , 4 , 5 ] . many investigators confirmed all facts mentioned above since 1997 when schuessler performed the first lrp in history . 250 ml is reported in recent studies enrolling a large series of patients . however , traditionally we base blood loss on blood volume collected intraoperatively in the suction device bottles . we already know that both anesthesiologists and urologists tend to underestimate blood loss during open retropubic prostatectomy and that the underestimation is relatively important . the little accuracy of visual estimation of blood loss had been clearly proven by gynecologists and obstetricians [ 9 , 10 , 11 ] . in this setting , we decided to answer the question whether intraoperative blood loss during lrp assessed clinically corresponds with changes in blood cell count ( bcc ) . the aim of this study was to analyze changes in bcc resulting from lrp and to compare them with clinical blood loss estimation . there were 71 men submitted to extraperitoneal lrp due to organ confined prostate cancer in our institution from september 2009 to march 2011 . based on a surgeon 's subjective assessment reported in their surgical protocol , we isolated the group of 61 men with clinically minimal intraoperative blood loss , which was defined as loss of less then 200 ml . for the final analysis we included 60 men with full data regarding surgery and laboratory findings in perioperative period . mean age of the cohort was 62.8 years . we performed retrospective analysis of medical documentation with special interest in laboratory findings . according to standard management with patients submitted to lrp in our institution , all the group had blood tests performed a day before ( test 1 ) and 6 hours after the surgery ( test 2 ) . we registered results of all bcc parameters , creatinine serum concentration and estimated glomerular filtration rate ( egfr ) at these two time intervals . an automated hematology analyzer was used for bcc and the colorimetric jaffe reaction for creatinine serum concentration measurement . estimated gfr was calculated using the mdrd ( modification of diet in renal disease ) formula . paired t - test was used for comparing results of tests 1 and 2 for each parameter . normal distribution was confirmed by the shapiro - walk test while the equality of variances was assessed using levene 's test before all the t - tests were performed . the differences were considered to be statistically significant when the p - value was lower than 0.02 . there were 71 men submitted to extraperitoneal lrp due to organ confined prostate cancer in our institution from september 2009 to march 2011 . based on a surgeon 's subjective assessment reported in their surgical protocol , we isolated the group of 61 men with clinically minimal intraoperative blood loss , which was defined as loss of less then 200 ml . for the final analysis we included 60 men with full data regarding surgery and laboratory findings in perioperative period . mean age of the cohort was 62.8 years . we performed retrospective analysis of medical documentation with special interest in laboratory findings . according to standard management with patients submitted to lrp in our institution , all the group had blood tests performed a day before ( test 1 ) and 6 hours after the surgery ( test 2 ) . we registered results of all bcc parameters , creatinine serum concentration and estimated glomerular filtration rate ( egfr ) at these two time intervals . an automated hematology analyzer was used for bcc and the colorimetric jaffe reaction for creatinine serum concentration measurement . estimated gfr was calculated using the mdrd ( modification of diet in renal disease ) formula . paired t - test was used for comparing results of tests 1 and 2 for each parameter . normal distribution was confirmed by the shapiro - walk test while the equality of variances was assessed using levene 's test before all the t - tests were performed . the differences were considered to be statistically significant when the p - value was lower than 0.02 . we noticed statistically and clinically significant differences regarding all bcc parameters measured at the two time intervals . the measurement results are expressed as mean values and standard deviations rbc  red blood cells ; hb  hemoglobin concentration ; hct  hematocrit ; wbc  white blood cells ; pct  platelet crit simultaneously , renal function , assessed by creatinine serum concentration measurement and egfr calculation , was stable . the measurement results are expressed as mean values and standard deviations creat  creatinine serum concentration ; egfr  estimated glomerular filtration rate our retrospective investigation was aimed at critical analysis of the value of clinical assessment of blood loss during lrp . to the best of our knowledge , such an analysis has never been done before , while its clinical importance remains obvious . based on previous studies we can calculate the effect of blood loss on hemoglobin concentration . using the same formulas taking the results of a study performed by davies et al . , we may assess the real blood loss in our group of patients to be as high as 8 ml / kg , hence 600 ml in a typical 75 kg male prostate cancer patient . at the same time , clinically assessed blood loss was calculated by the surgeon to be not more than 200 ml . our study shows discrepancies between clinical estimation and laboratory results using the laparoscopic approach , which occurred to be much more significant . while the differences in open prostate surgery do not exceed 30% , we noticed differences of 300% in our group . finally , it is also worth remembering that laboratory tests are imperfect . showed that when assessing blood loss based on a decrease in hemoglobin concentration , we can underestimate it by more than 30% . it means that real blood loss in our group of patients might even exceed 800 ml , hence we found a four - fold clinical underestimation of blood loss . we can summarize that clinical and laboratory methods of blood loss estimation are neither practical nor reliable . this important statement is supported by schorn 's critical review of methods of blood loss measurement . the reason for such important differences between clinical and laboratory estimation of blood loss during lrp should be indicated . in general , bleeding during laparoscopic procedures may be reduced following insufflation of the appropriate cavity and the associated tamponade effect [ 1518 ] . in this setting , venous bleeding is more likely to occur shortly after the procedure than during the surgery . we suppose that visual underestimation of blood loss may result from early postoperative formation of perivesical , perineal , or obturator hematomas , while direct measurement of blood loss does not consider it . first , it is its retrospective character , which is supported by archival medical documentation . this fact may affect results , however , obtained results are clearly unambiguous . whether we under- or overestimate the significance of the problem second , being a pilot study , this analysis covers only 60 cases of lrp with clinically minimal blood loss . based on our preliminary results , it may be justified to collect the data prospectively in order to finally confirm our findings . the accuracy of clinical estimation of blood loss during lrp is low . while clinically insignificant , blood loss seems to be as high as approx . bcc seems to be a more accurate method of intraoperative blood loss estimation compared to measurement of blood volume collected intraoperatively in the suction device bottles .