5α reducatase inhibitors (5-ARIs) is most frequently used drug for benign prostatic hyperplasia. In previous studies, it is known that  5-ARIs can decrease prostate volume as 30% and reduce international prostatic symptoms score (IPSS) after 2 year treatment . However, there is a few studies for analyzing   morphologic changes and intravesical prostate protrusion after treatment of 5-ARIs.
This study was conducted to analyze morphologic changes and intravesical prostate protrusion after treatment of 5-ARIs.

Fom 2013 to 2018, among the 13,000 cases of trans-rectal ultrasonography (TRUS) performed, 210 cases who were administered with 5α reducatase inhibitors for the first time with a follow up period of at least a year, were comprised in this retroprospective study. 
Patients, diagnosed as prostatitis and prostate cancer, were excluded. Prostate volume (PV), trasitional zone volume (PV), intravesical prostatic protrusion length (IPP), prostatic urethral angle (PUA) and prostatic urethra length (PUL) were measured before and after treatment of 5-ARIs.

Mean age was 51±7.7 years old, and mean follow up period was 23.8±3 months. Before 5-ARIs treatment, mean values of PV, Tz volume, IPP length, and prostatic urethral length were 46.7±24.9cc, 26.0±19.7cc, 3.8±6.4mm, and 56.6±9.2mm, repectively. After the treatment, mean values of PV, TV, IPP length, and prostatic urethral length were 38.9±20.2cc, 20.7±15.3cc, 3.3±5.1mm and 46.5±13.8mm. PV and Tz volume have showed statistically significant reductions of 16.7% and 20.2% (p<0.001), respectively, after taking 5-ARIs. IPP length and prostatic urethral length were redused by 17.8% and 16.0%, but they did not show statistical significance (p=0.248, p0.287, respectively). Before 5-ARIs treatment, mean length, width and height of prostate were 47.1mm, 50.2mm and 36.0mm and after taking 5-ARIs, they were all reduced by 4.7%, 8.3% and 19.8%. After treatment of 5-ARIs, PV and Tz volume showed significant reduction. However, IPP length and prostatic urethral length did not show significant reduction.

After treatment of 5-ARIs, PV and Tz volume showed significant reduction. However, IPP length and prostatic urethral length did not show significant reduction. 
Prostate length was reduced by 4.7%, whilst prostate height was reduced by 19.8%. Since effect on prostate length by 5-ARIs is relatively minimal, we can assume that changes in IPP length and prostatic urethral length were minimal after treatment of 5-ARIs. Further prostective studies are needed to confirm these findings.

This result assumed that  that changes in IPP length and prostatic urethral length were minimal after treatment of 5-ARIs. Further prostective studies are needed to confirm these findings.