Lower urinary tract symptoms (LUTS) represent one of the most common and bothersome conditions seen in daily urologic practice, affecting at least one in every four men older than 40 years.1) The prostate volume and morphological features of the prostate are well known to be associated with LUTS in the male patients. However, whether microscopic structural changes of prostate contribute to LUTS and lower urinary tract dysfunction (LUTD) has not been established. Recently, the field of quantifying tissue microscopic structural change with magnetic resonance imaging (MRI) has been gaining increasing attention, with the number of publications growing exponentially. The apparent diffusion coefficient (ADC), which is a non-invasive functional MRI technique, can assess changes in diffusion of water molecules due to microscopic structural changes. We considered that the ADC can provide the quantitative information about the microscopic structural changes of the prostate. The aim of this study was to evaluate the effect of microscopic structural changes of prostate on LUTS and LUTD by evaluating the association between ADC values and LUTS and lower urinary tract function.

Patients who underwent MRI before random transrectal ultrasonography–guided prostate biopsy and had a diagnosis of benign by the biopsy at our hospital between May 2019 and January 2021 were included in this study. Before the biopsy, uroflowmetry parameter, bladder voiding efficiency (BVE); (voided volume/total bladder capacity) × 100, International Prostate Symptom Score (IPSS) and overactive bladder symptom score (OABSS) were evaluated. The voiding and storage IPSS sub-score (IPSS-V and IPSS-S, respectively) were recorded separately. We measured mean ADC value at the base of the prostate by MRI. The relationship between the mean ADC value and parameters evaluated before the biopsy was analyzed. All values were expressed as mean ± standard deviation. A linear regression analysis was used for continuous variables. P-values of <0.05 were considered to be statistically significant.

A total of 111 patients (68.9 ± 6.3 years) entered the study. The OABSS (3.8 ± 2.5 points) was mild. The total IPSS (8.6 ± 6.3 points) and QOL index (3.1 ± 1.5 points) were moderate. The IPSS-V was 4.0 ± 3.9 points and IPSS-S was 3.9 ± 2.7 points. The prostate volume was 41.0 ± 18.7 mL. The maximum flow rate was 13.1 ± 7.1 mL/sec and the bladder capacity was 250 ± 129 mL. The BVE was 82.0 ± 16.8 %. The ADC value at the base of prostate was 1,468 ± 190 mm2/sec. The ADC value was significantly positively correlated with OABSS (C.C = 0.25, P=0.02) and IPSS-S (C.C = 0.22, P=0.03). The mean ADC value was significantly negatively associated with BVE (C.C = -0.22, P=0.04). The IPSS-V (C.C = 0.18, P=0.07), maximum flow rate (C.C = -0.15, P=0.19) and bladder capacity (C.C = 0.04, P=0.70) were not significantly associated with the mean ADC value.

In our study, the high ADC value at the base of prostate caused storage symptoms and decreased the BVE. BVE is a product of bladder contractility against urethral resistance and is measured to the degree of bladder emptying. BVE is used to evaluate bladder outlet obstruction (BOO). The microscopic structural changes of prostate reflected by high ADC value may worsen BOO. BOO is well known to be a major cause of DO in male LUTS patients. The microscopic structural changes of prostate reflected by high ADC value might contribute to storage symptoms through worsened BOO. On the other hands, some studies reported that inflammation affects prostate ADC value.2) It is reported that inflammation of prostate is one cause of LUTS in male patients.3) The high ADC value may also reflect the inflammation of prostate which affects storage symptoms.

We demonstrated that high ADC value at the base of prostate was associated with LUTS and LUTD. It is possible that the microscopic structural changes of prostate reflected by high ADC value affect lower urinary tract function through the different mechanism from the prostate volume and morphological features of prostate. The evaluating ADC value of prostate may provide individualized treatment options for patients.

Robertson C, Link CL, Onel E, Mazzetta C, Keech M, Hobbs R, et al. The impact of lower urinary tract symptoms and comorbidities on quality of life: The BACH and UREPIK studies. BJU Int. 2007;99:347–54.
Inflammation appears as high Prostate Imaging-Reporting and Data System scores on prostate magnetic resonance imaging (MRI) leading to false positive MRI fusion biopsy. Rourke E, Sunnapwar A, Mais D, Kukkar V, DiGiovanni J, Kaushik D, Liss MA. Investig Clin Urol. 2019 Sep;60(5):388-395.
Inflammation is a target of medical treatment for lower urinary tract symptoms associated with benign prostatic hyperplasia. De Nunzio C, Salonia A, Gacci M, Ficarra V. World J Urol. 2020 Nov;38(11):2771-2779.