The role of preoperative endo-rectal coil magnetic resonance imaging in predicting surgical difficulty for robotic prostatectomy

Objectives: To determine whether pelvimetry on endo-rectal coil magnetic resonance imaging (eMRI) predicts surgical difficulty of robot-assisted laparoscopic prostatectomy (RALP).

Methods: Patients' records with preoperative eMRI in our RALP database from April 2008 thru May 2009 were reviewed. Demographic, preoperative clinical data, and eMRI anatomic measurements, including calculated prostate volume (PV) and the pelvic cavity index (PCI), were recorded. PCI is the pelvic inlet multiplied by the interspinous distance and divided by the pelvic depth; PCI estimates the robotic working space. Correlative and multiple regression analyses of clinical and pelvimetric data were performed for prediction of estimated blood loss (EBL), operative time (OT), positive surgical margin (PSM), and transfusion rate as surrogates of surgical difficulty.

Results: Prostatic transverse diameter, PV, and the PV-to-PCI ratio were significantly correlated with both OT and EBL (P < .05). Body mass index also correlated with EBL (P < .05). Multiple linear regression analysis demonstrated that the PV-to-PCI ratio significantly predicts OT and EBL. No factor significantly predicted PSM status or transfusion rate on regression analysis. Analysis within the PSM group revealed that those with an apical PSM had statistically narrower and deeper pelvises.

Conclusions: Patients with larger prostates and with narrow, deep pelvises are predicted to have a more difficult RALP. The PV-to-PCI ratio statistically predicts lengthier and bloodier procedures. However, that ratio does not predict PSM or transfusion risk on regression analysis. The eMRI predicts the level of surgical difficulty and is a valuable adjunctive study to obtain before RALP.