1228 MRI ANALYSIS OF ANATOMICAL LANDMARKS WITH RESPECT TO INFLATABLE PENILE PROSTHESIS RESERVOIR PLACEMENT

Abstract

INTRODUCTION AND OBJECTIVES: Insertion of a threepiece inflatable penile prosthesis (IPP) reservoir is a “blind procedure”. The traditional reservoir placement in the space of Retzius can result in damage to bladder, bowel and femoral blood vessels. A single cadaveric study has delineated pertinent anatomic relationships. We have attempted to evaluate similar anatomical measurements in an in vivo model using magnetic resonance imaging (MRI). METHODS: Endorectal MRI studies in men being evaluated for prostate cancer were reviewed. Prior pelvic surgery, radiation or an in situ urinary catheter were exclusions. Endorectal MRI was performed on a 3 Tesla system with T1 and T2 weighted images reviewed usingboth axial and sagittal planes. Pertinent anatomical landmarks were evaluated by 2 independent readers, blinded to clinical and pathological data. All measurements were defined by an experienced radiologist. Measurements included (i) distance from external inguinal ring(EIR) to external iliac vein(EIV) (ii) superior aspect of pubic symphysis (PS) to bladder and (iii) EIR to nearest bladder point. Correlation was measured between bladder volume and (iii). For distances (i) and (iii) bilateral measurements were obtained and data averaged as no significant differences were observed. Means and standard deviations are presented. Pearson correlations were used to assess the relationship between variables, and regression analysis use to predict changes in (iii) with respect to bladder volume. RESULTS: 24 MRI studies were reviewed. Mean distances: EIR to EIV 3.09cm (2.23-3.84);superior aspect of PS to nearest point of bladder (midline) 0.86cm (0.37-1.24); EIR to the nearest point of the bladder 1.76cm (0.08-3.66). Correlation between EIR-bladder distance and bladder volume was r -0.36, p 0.9. Average bladder volume was 93.04cm3 (34.5-177.6),(SD 36). On regression analysis as bladder volume increases by 10 cm3 the distance to the EIR decreased by 1mm. CONCLUSIONS: This is the first attempt to analyse anatomical landmarks with respect to IPP reservoir placement in an in vivo model. The close proximity of the external iliac vein and bladder should alert surgeons to the potential for damage to these structures during this procedure. This also emphasizes the importance of decompressing the bladder during reservoir placement.