What are the typical urodynamics findings in patients with Benign Prostatic Hyperplasia (BPH)?

From the Guidelines

Urodynamic findings in patients with Benign Prostatic Hyperplasia (BPH) typically include bladder outlet obstruction characterized by increased detrusor pressure with decreased urinary flow rate, as evidenced by the 2003 AUA guideline on management of BPH 1. The typical urodynamics findings in BPH patients can be summarized as follows:

• Maximum flow rates (Qmax) below 15 mL/second
• Detrusor pressures at maximum flow (PdetQmax) exceeding 40 cmH2O
• High bladder outlet obstruction index
• Prolonged voiding time
• Increased post-void residual urine volume (often >50-100 mL)
• Decreased bladder compliance
• Detrusor overactivity as a secondary phenomenon, manifesting as involuntary detrusor contractions during the filling phase These findings are supported by the AUA guideline, which suggests that pressure-flow urodynamic studies can predict the response to surgery and, less so, minimally invasive therapies 1. The guideline also recommends uroflowmetry for all men who choose invasive or minimally invasive therapy, followed by pressure-flow studies in those men with a maximal urinary flow rate (Qmax) greater than 10 ml/sec when surgery is being considered 1. The use of pressure-flow urodynamic studies is considered optional in men prior to invasive therapy, but it can provide valuable information on the relative contribution of the bladder and bladder outlet to lower urinary tract function, dysfunction, or symptoms 1.

From the FDA Drug Label

Effect on Maximum Urinary Flow Rate In the patients in A Long-Term Efficacy and Safety Study who remained on therapy for the duration of the study and had evaluable urinary flow data, finasteride tablets increased maximum urinary flow rate by 1.9 mL/sec compared with 0. 2 mL/sec in the placebo group.

The typical urodynamics findings in patients with Benign Prostatic Hyperplasia (BPH) include:

• Decreased maximum urinary flow rate: BPH patients often have a lower maximum urinary flow rate compared to healthy individuals.
• Increased post-void residual volume: BPH patients may have a higher post-void residual volume due to incomplete bladder emptying.
• Obstructive symptoms: BPH patients often experience obstructive symptoms such as impaired size and force of stream, sensation of incomplete bladder emptying, and delayed or interrupted urination.
• Irritative symptoms: BPH patients may also experience irritative symptoms such as nocturia, daytime frequency, and need to strain or push the flow of urine.

Treatment with finasteride tablets has been shown to improve urodynamics findings in BPH patients, including an increase in maximum urinary flow rate of 1.9 mL/sec compared to 0.2 mL/sec in the placebo group 2.

From the Research

Urodynamics Findings in BPH

Urodynamics findings in patients with Benign Prostatic Hyperplasia (BPH) can vary, but some common characteristics include:

• Obstruction of the bladder outlet, which can be objectively documented using modern urodynamic methods 3
• Decreased maximum urinary flow rate (Qmax) and increased postvoid residual volume 4
• Abnormal bladder capacity, low compliance, and indeterminate detrusor contractions may be present in some patients, particularly those with small prostates 4
• Detrusor underactivity and poor bladder contractility index may also be observed in patients with BPH 4

Prostate Size and Urodynamic Characteristics

Prostate size can influence urodynamic characteristics and clinical outcomes in BPH:

• Patients with small prostates (≤30 mL) may have lower Qmax, higher incidence of abnormal bladder capacity, and lower voiding efficiency compared to those with large prostates (>30 mL) 4
• Small prostates may also be associated with higher failed voiding trials postsurgery and poor urodynamic parameters 4
• The relationship between prostate size and urodynamic characteristics is complex, and further research is needed to fully understand the underlying mechanisms 4

Diagnostic and Therapeutic Implications

Urodynamics findings in BPH have important implications for diagnosis and treatment:

• Urodynamic studies can help distinguish between obstructive and non-obstructive symptomatic BPH, guiding treatment decisions 3
• Medical therapies, such as alpha-blockers and 5-alpha reductase inhibitors, can be effective in managing BPH symptoms, and combination strategies may offer synergistic benefits 5
• Surgical interventions, such as transurethral resection of the prostate (TURP), may be necessary in some cases, but the success rate can vary depending on the presence of obstruction and other factors 6, 3