As economic improvement and advances in medical technology have lengthened the human lifespan, there are growing interests in increasing the quality of life.¹ As a result of an increased lifespan, people may also experience diseases that had not been previously detected. With the growing awareness of the need for health screening for prevention and early detection of diseases, many hospitals are offering various personal health checkup programs in addition to national health screenings. Traditionally, health screening aims to lower the burden and mortality of a particular disease among individuals who do not have relevant symptoms.

With an increase in the elderly population, the incidence of prostate diseases also rises, which consequently increases the demands for prostate diseases screening.

Prostatic enlargement resulting in benign prostatic hyperplasia (BPH) is a chronic, progressive disease which is common in male population mostly after the sixth decade.² Lower urinary tract symptoms (LUTS) are also common conditions in middle-age or older men.³ LUTS are not only influenced by the size of the prostate but also by age, body weight, hormone changes, lifestyle, and chronic diseases, such as diabetes and stroke. The International Prostate Symptom Score (IPSS) is a useful and validated questionnaire to evaluate LUTS.⁴ Transrectal ultrasonography (TRUS) is often used as a diagnostic means for patients who present urinary symptoms and to facilitate prostate biopsy. When TRUS was performed for screening, it is often the patients' symptoms are not assessed and only the total prostate volume is measured. Some study showed the reliability of prostate volume measurement by TRUS seems to be questionable for the determination of the severity of LUTS.⁵ There are concerns about the accuracy and usefulness of TRUS in screening to evaluate the prostate disease. Thus, in this study, we measured the central gland volume as well as the total prostate volume using TRUS performed for health screening and also surveyed the IPSS. This study aimed to evaluate the relationship between prostate volume and lower urinary symptom (LUTS) in subjects undergoing health checkup and to know the usefulness of TRUS in health screening.

Among men aged ≥20 years who underwent TRUS for health screening at a health promotion center in Jeju between May 2015 and August 2017, those who completed the IPSS survey were enrolled in this study. Patients with prostate cancer, bladder cancer, cerebral infarction and history of prostate surgery or transurethral surgery and those who were taking male sex hormones and BPH medication were excluded.

All participants completed a self-reported questionnaire regarding their medical histories, highest educational attainment, income, marital status, smoking history, drinking history, and exercise history. The participants who drink at least 7 standard alcohol drinks at one time more than twice a week were classified into the high-risk alcohol user and those who exercise at least 3 times a week into the regular exercise group. The prostate volume was measured by 1 radiologist using TRUS, including total prostate volume, central gland volume and ratio of central gland volume to total prostate volume. The prostate volume was automatically measured using the following ellipsoid volume equation: height (cm)×width (cm)×length (cm)×0.523. The main lesions detected on TRUS and prevalence of BPH were investigated in each age group, and the prevalence of BPH was subclassified by prostate volumes of ≥25 mL and ≥30 mL. Furthermore, the differences in the IPSS by prostate volume and differences in the prostate volume by LUTS were analyzed. The correlation between the prostate volume and IPSS was analyzed by dividing the IPSS into the storage score and voiding score; the correlation was also analyzed for each item of IPSS. Statistical analyses were performed using the IBM SPSS Statistics ver. 20.0 (IBM Co., Armonk, NY, USA), and p-value of ＜0.05 was considered statistically significant.

The present study protocol was reviewed and approved by the Institutional Review Board (IRB) of Jeju National University Hospital (Reg. No. 2016-0803) and ensured that individuals were not identifiable by providing linkable anonymous data to the researchers. Waiver of informed consent for this study was approved by the IRB.

The prostate tends to increase in volume with age, and symptoms, such as urinary frequency, nocturia, weak stream, and intermittency occur because of the elevated concentration of prostatic stromal or epithelial cells. LUTS are caused by various factors, one of which is BPH. The definition of BPH varies by study; it is sometimes defined as a prostate volume of ≥25 mL or ≥30 mL on TRUS.⁴ The prevalence of BPH tends to increase with age. In a cross-sectional study on adults living in the Jeju island, the prevalence was approximately 21%; the rates were 11.6%, 18.1%, 30.8%, and 50.8% in patients in their 50s, 60s, 70s, and 80s, respectively.⁶ In this study, the prevalence of BPH also tended to rise with age; particularly, the prevalence was 47.9% when BPH was defined as a volume of ≥25 mL and 25.3% when defined as a volume of ≥30 mL. The prevalence of BPH for prostate volumes of ≥25 mL and ≥30 mL in the 60s group was 72.9% and 45.3%, respectively; that in the 70s group was 72.5% and 50.0%, respectively, showing a prevalence higher than those reported in previous studies. This is speculated to reflect the high demands for prostate screening of individuals with urinary symptoms. The causes of BPH include aging and male sex hormones, and it is also associated with race, obesity, hypertension, and smoking.^7-9 The previous our study also found that the prostate volume is significantly correlated with body mass index (BMI), waist circumference, and visceral fat area.¹⁰ In a retrospective cohort study in Korea, abdominal obesity is positively associated with prostate enlargement.¹¹ But in other study, LUTS was not significantly associated with BMI, waist circumference, blood pressure and glucose level¹² and our study showed similar results. LUTS could be caused by various factors not only prostate volume.

The prevalence of LUTS is generally above 50%, but ranges widely from 23% to 83% in South Korea.^13-16 In a study on Chinese, Taiwanese, and Korean adults, more than 60% of the total population had such symptoms; the prevalence was higher among men than among women and increased with age.¹⁷ In a study on adults aged ≥40 years, the prevalence of symptoms related to storage was 16.2% in men and 30.5% in women; that of nocturia, frequency, and weak stream was 36%, 30%, and 29%, respectively and LUTS prevalence was not affected by education level or marital status in the overall population and associated with marital status in only women.¹² There were no associations between marital status, education, incomes with LUTS in our study. In our study, subjects who took antihypertensive medication or diabetes were slightly higher in severe LUTS group, but it was not statistically significant. In one study on patients with BPH and LUTS, men with hypertension are more likely to have a higher IPSS and large prostate volume than men without hypertension.¹⁸ But there was no significant difference of variables between subjects with diabetes mellitus, smoking or dyslipidemia and without car-diovascular risk factors.

In our study total IPSS, storage score, and voiding score significantly differed when the cutoff of the prostate volume was set to 30 mL. However, when analyzed according to each symptom, there were significant differences only for urgency and weak stream. When the cutoff of the prostate volume for BPH was set to 25 mL, there was difference only for nocturia. By comparison of the prostate volume after dividing into 3 groups according to LUTS, the volume of the severe symptom group differed from those of the mild and moderate symptom groups however, the prostate volumes between the mild and moderate symptom groups did not significantly. There was no difference of the TZI among groups divided by the severity of the prostate symptoms. The severity of LUTS can increase in relation to the prostate volume. But it showed only comparing with the severe symptom group. If LUTS was mild or moderate it is needed to assess the additional causes. With regard to the correlation between the prostate volume and IPSS, the central gland volume was correlated with nocturia, but not with other factors. Choi et al.¹⁹ reported that the association between the TZI and LUTS among whites, Hispanics, and Koreans, and Koreans showed a higher TZI and higher prevalence of LUTS. In this study, the TZI tended to increase with increasing severity of LUTS; however, the association was not significant. Hence, there may be other factors except increased transitional zone volume that affect voiding symptoms. Although the size of the prostate gland and urinary symptom are somewhat related, the only TRUS in health screening does not completely reflect the urinary symptom. Tatar et al.⁵ analyzed the value of prostate gland volume measurement by TRUS in prediction of severity of LUTS. The study showed low correlation between IPSS and prostate volume measurement by TRUS. So they insisted prostate volume measurement by TRUS is a poor predictor for the determination of the severity of LUTS therefore IPSS should be primarily considered for the determination of the severity of LUTS. Their results were similar with our study.

It is necessary to fully understand the symptoms of the patient through questionnaires on urinary symptom. Therefore, it should be able to resolve urinary symptom through accurate diagnosis by performing TRUS, uroflowmetry, questionnaires for urinary symptom, such as IPSS, overactive bladder (OAB) symptoms score, OAB questionnaire, and King's Health Questionnaire.

TRUS can be also used to diagnose calcifications, cysts, and nodules. The prevalence of prostate calcification varies widely from 13.8% to 100%, and it is often discovered with BPH and prostate cancer.^20-24 Large or diffuse calcifications within adenomata produce acoustic shadowing. Prostatic adenomata are arising more commonly in hypoechoic nodule and mixed echogenicity.²⁵ Cystic lesions identified with TRUS include müllerian duct cyst, prostatic utricle cyst, ejaculatory duct cyst, cystic degeneration in BPH, prostatic retention cyst, cavitary prostatitis, and prostatic abscess.²⁶ In the study on patients visiting a health promotion center and urology outpatients, the prevalence of prostate calcification was 36.1% and 48.3%, respectively, showing a higher prevalence among the latter. However, there were no differences in the size, location, and number, and the urology outpatients showed more frequent LUTS.²⁷

In this study, the prevalence of prostate calcification was 54.1%, which increased with age; the prevalence increased to 61.2% in the 60s group and 72.5% in the ≥70s group. The incidence of midline prostatic cyst ranges from 1% to 14% among patients with voiding symptoms.^28-32 In one study, the incidence was approximately 28% among healthy adults, 29.5% among adults in their 40s, and 31.4% among adults in their 60s.³³ In this study, the overall incidence of prostatic cysts was 8.6% and 10.8% in the 60s group and 20.0% in the 70s group, showing that it increases with age.

This study has some limitations. This study was conducted in a single health screening center; thus, the data cannot represent Korea's entire population. Although there were strengths as basic data and distribution by analyzing all age groups including asymptomatic people, it might affect the reliability of results that range of variables was wide and heterogeneous such as age (20-87 years) or prostate volume (11-87 mL). Further, the quality of life item was missed in the IPSS survey and did not perform digital rectal examination. Lastly, the uroflowmetry was not included. Complicated and invasive studies are not necessary for health screening, but survey about voiding symptoms is basically recommended in company with TRUS because prostate volume measurement by TRUS is a poor predictor for the determination of the severity of LUTS.

The relationship between prostate volume and urinary symptoms showed significant but low correlation and found only in some components. Thus, the TRUS alone in health screening does not completely reflect the urinary symptoms. It is necessary to fully understand the symptoms of the patient through questionnaires on urinary symptoms because LUTS may be caused by various factors. When the IPSS is high, additional tests should be performed to differentiate BPH from other urologic diseases that may cause LUTS. It would be more useful to accompany various voiding-related surveys in addition to TRUS during health screening.

The authors claim no conflicts of interest.