Hydrodissection of the Neurovascular Bundles in Laparoscopic Radical Prostatectomy: Impact on Positive Surgical Margins

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Background: We have previously reported the use of hydrodissection as an aid in the surgical dissection of the neurovascular bundles (NVB) during open radical retropubic prostatectomy and have applied this technique more recently to laparoscopic radical prostatectomies (LRP). Here, we wished to determine whether hydrodissection of the NVB can reduce the rate of positive surgical margin (PSM) after LRP.
Methods: We performed a retrospective review of all patients with localized prostate cancer (pT2a- pT3b N0M0) treated by LRP by a single surgeon at a tertiary care center between October, 2001 and December, 2005. Preoperative clinical data, operative technique and pathologic data were evaluated for 532 cases. Patient age, BMI, operative time, preoperative PSA, surgical case number, pathologic prostate volume (Pr vol), pathologic stage (pstage), extracapsular extension (Ec ext), seminal vesicle invasion (SV inv), Gleason score, and use of nerve sparing technique (nspare) were all evaluated as potential covariates to the predictor, hydrodissection. All potential covariates were analyzed in a univariate fashion using t-tests for continuous variables and chi-square tests for binary and ordinal variables. Univariate logistic regression analyses were used to assess all potential variables and then a multivariate logistic regression model was developed including the predictor, hydrodissection and all significant or clinically relevant covariates and confounders. The outcome of our model was surgical margin status.
Results: The overall positive surgical margin rate in the 532 patient cohort was 18.8%. On univariate analysis age, BMI, and operative time did not significantly correlate with PSM, while prostate volume (p=0.0392), Gleason sum (p<0.0001), EC ext (P<0.0001), SV inv (p=0.0005) and stage (pTa → pT3b)(p<0.0001) were found to be significant. PSA approached significance with a p value of 0.053. Only 1.1% of patients had non-nerve sparing and 6.4%had unilateral nerve sparing. Due to these incomparable sample sizes, nspare was not included in our analysis. The predictor of interest, hydrodissection was used in 398/532 (74.8%) of the cases and the rate of use increased with surgical case number. For this reason we included case number in our multivariate model. By univariate analysis, the use of hydrodissection was not a significant predictor of surgical margin status. However, when corrected for surgical case number, Gleason score, pstage, Pr vol, and PSA, the use of hydrodissection demonstrated a decreased risk of having a positive surgical margin (Odds Ratio [OR]: 0.43, [95% CI 0.19-0.96]), Likelihood Ratio p<0.0001). By this model, Gleason sum (OR = 1.6, [95% CI 1.03-2.52]), pathologic stage (OR=1.9, [95% CI 1.44-2.49]) and prostate volume (OR= 0.98 [95% CI 0.97-0.99]) also remained significant predictors of surgical margin status.
Conclusions: We demonstrate that hydrodissection of the NVB during LRP can significantly reduce the risk of a positive surgical margin. In addition to better identification of the NVB, hydrodissection may aid in clear identification of the avascular plane between the prostatic capsule and peri-prostatic fascia, opening the potential space and reducing the likelihood of positive surgical margins during LRP.

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