Hypothesis / aims of study
Lower urinary tract symptoms (LUTS), such as nocturia and urinary incontinence, are common and interfere with quality of life (QOL) in elderly men. Most male LUTS patients report overactive bladder (OAB) symptoms including frequency, urgency and urinary incontinence. The pathophysiology of LUTS, particularly in the elderly, is multifactorial. Attention has recently focused on the vesical adaptation response to diuresis (VARD). High diuresis increases the voided volume at each voiding, and low diuresis decreases the voided volume at each voiding. Voided volume at each void is thus constantly changing according to diuresis. This is generally understood as the VARD. VARD could be considered a physiological reaction of a living organism with normalization of lower urinary tract function. In OAB, VARD has been shown to be lacking1). We have reported that improvement of LUTS was seen with acquisition of VARD after robot-assisted laparoscopic radical prostatectomy (RARP)2) .VARD is important to maintain lower urinary tract function, and a lack of VARD might contribute to LUTS. However, the mechanisms causing a lack of VARD remain unclear. The aim of this study was to determine whether patient characteristics affect VARD.
Study design, materials and methods
Male patients with LUTS who attended our hospital between 2013 and 2017 were included in this study. Exclusion criteria were diabetes mellitus, neoplasm, urinary stone, neurological disorder and history of abdominal and pelvic surgery, including transurethral resection surgery. Uroflowmetry, ultrasonography to measure prostate volume, prostate specific antigen (PSA), Overactive Bladder Symptom Score (OABSS) and 24-h frequency-volume charts (FVCs) were evaluated. The 24-h FVC recorded volumes voided, as well as the time of each micturition. Urine output rate was calculated by dividing the volume voided by the interval between 2 successive micturitions. VARD was defined as the presence of a significant correlation between urine output rate and voided volume at each voiding (R2 > 0.4). OABSS evaluated OAB as a total score >3 and an urgency score >2. According to presence or absence of VARD, patients were divided into two groups: a presence of VARD group; and an absence of VARD group. Age, uroflowmetry, prostate volume, PSA and OAB were compared between groups, with values of P<0.05 considered significant.
A total of 43 patients entered the study (presence of VARD group: 22 patients; absence of VARD group: 21 patients). Age, maximum urinary flow rate, voiding volume, residual urine volume and PSA did not differ significantly between groups (presence of VARD vs absence of VARD: Age; 72.0 ± 7.2 years vs 75.7 ± 5.4 yeras, P=0.056. maximum urinary flow rate; 9.3 ± 4.1 mL/sec vs 7.7 ± 3.3 mL/sec, P=0.537. voiding volume; 167 ± 54 mL vs 138 ± 50 mL, P=0.120. residual urine volume; 38 ± 30 mL vs 43 ± 32 mL, P=0.562.PSA; 2.4 ± 1.9 ng/mL vs 2.9 ± 2.7 ng/mL, P=0.537). A significant relationship existed between VARD and OAB (P = 0.035). Fifteen patients in the absence of VARD group had OAB. Prostate volumes were significantly larger in the absence of VARD group then in the presence of VARD (presence of VARD vs absence of VARD: 34.1 ± 10.4 mL vs 43.1 ± 15.6 mL, P=0.040) (Table 1).
Interpretation of results
According to these results, male patients without VARD demonstrated OAB and large prostate. Previously, we have demonstrated that VARD was acquired after RARP in patients with LUTS, following the improvement of LUTS and lower urinary tract dysfunction2). We considered that the effect of the prostate on bladder, including decreased bladder blood flow, is important to keep VARD. Benign prostatic enlargement might contribute to the lack of VARD.