CHAPTER 6 Voiding disorders and bladder outlet obstruction

INTRODUCTION

Due to the high prevalence of bladder outflow obstruction (BOO) secondary to benign (and malignant) prostatic disease, voiding difficulties are the commonest reason for men to present to a urologist. However, recent evidence shows that a large population of men have a storage disorder such as OAB either as a primary diagnosis or secondary to BOO. Since, voiding disorders frequently are associated with storage LUTS such as nocturia and daytime frequency, this may well lead to a confusing mix of symptoms. With this in mind, men with LUTS should not be assumed to have a voiding disorder/prostatic disease and if there is any doubt as to the diagnosis then pressure/flow cystometry is necessary to differentiate definitively between voiding and storage disorders.

Figure 6.4 Typical cystometry appearances for bladder outlet obstruction. In this case the screening schematic shows obstruction at the level of the prostate.

Figure 6.5 Pressure/flow trace in patient with both detrusor overactivity during filling and BOO during voiding. This is a common pattern as many patients have both conditions coexisting.

Causes of voiding difficulty in men are:

• Anatomical outflow obstruction:

obstruction at the level of the prostate (commonest)

obstruction at the level of the bladder neck

obstruction due to a urethral stricture

extrinsic compression of bladder or urethra, e.g. from a tumour.

• Functional obstruction:

overactivity of the bladder neck/urethral muscles causing dyssynergy with the detrusor contraction.

• Detrusor muscle failure (poor contractility):

primary

secondary to outflow obstruction or a neurogenic disorder.

Voiding difficulty is far less common in females and when it occurs it should be thoroughly investigated with anatomical and functional investigations. Most female patients with voiding difficulty have a neuropathic disorder affecting the bladder, but a functional obstruction of the bladder outlet/urethra or detrusor muscle failure must be excluded. Causes of voiding difficulty in women are:

• Anatomical outflow obstruction:

overcorrection following cystourethropexy

extrinsic compression of bladder/neck urethra, e.g. from a tumour or pelvic organ prolapse (POP)

obstruction at the level of the bladder neck

urethral stenosis (stricture).

• Functional obstruction:

overactivity of the bladder neck/urethral muscles causing dyssynergy with the detrusor contraction.

• Detrusor muscle failure (poor contractility):

primary

secondary to outflow obstruction or a neurogenic disorder.

• Small volume urinary frequency:

many women with bladder overactivity report poor flow, hesitancy, etc. as a result of voiding prematurely at low bladder urine volumes.

ANATOMICAL BLADDER OUTLET OBSTRUCTION

Bladder outflow obstruction (BOO) is a generic term for obstruction during voiding, and is characterized by increased detrusor pressure and reduced urine flow rate. It is usually diagnosed definitively during pressure/flow cystometry although history, physical evaluation and simple urodynamic tests (voiding diaries, uroflowmetry and PVR) often point to the correct diagnosis; the majority of patients do not receive pressure/flow cystometry until initial treatment has failed, or if there are other complicating factors.

Most patients present with predominant voiding LUTS, but some present with complications of the BOO including:

• Acute urinary retention (AUR).

• Chronic urinary retention.

• Renal impairment and hydronephrosis.

• Urinary tract infections (UTIs).

• Bladder calculi.

• Haematuria.

• Secondary detrusor overactivity (occurs in up to 70% of men with prostatic BOO; it resolves in up to two-thirds of patients following surgical relief of the obstruction, although this suggests a causal relationship between BOO and detrusor overactivity in many patients; recent work has challenged this apparent causal link.)

Benign prostatic obstruction

TERMINOLOGY: ENLARGEMENT OF THE PROSTATE

Benign prostatic hyperplasia (BPH) A histological diagnosis and present in up to 50% of men over 60 years of age and nearly 88% by 80 years of age – the extent to which prostatic enlargement and symptoms secondary to BPH manifest themselves is variable.

Benign prostatic enlargement (BPE) Prostatic enlargement due to histological BPH. This term should be used when clinically detectable prostatic enlargement is evident, in the absence of a known histological diagnosis of BPH.

Benign prostatic obstruction (BPO) Obstruction to urinary flow demonstrable on pressure/flow cystometry secondary to the prostate gland. This may be due to enlargement of the prostate gland (Figure 6.1a) or to increased prostatic smooth muscle tone causing contraction of the prostate gland around the prostatic urethra (therefore the prostate does not need to be particularly enlarged to cause obstruction!).

Figure 6.1 Screening appearances of bladder outlet obstruction. (A) Normal appearance of male lower urinary tract during voiding. (B) Prostatic obstruction: lengthening and thinning of prostatic urethra, prostatic indentation of the bladder neck. (C) Bladder neck obstruction: bladder neck shut or narrow during voluntary voiding contraction. (D) DSD: Narrow membranous urethra, bulging of prostatic urethra. (E) Urethral stricture.

Treatment options include:

• Conservative measures:

Fluid intake advice

Improve mobility/dexterity/mental state.

• Phytotherapy (alternative medications from plant extracts; not recommended by World Health Organization (WHO) consensus).

• α1-adrenoceptor antagonists:

Alfuzosin

Doxazosin

Tamsulosin

Terazosin.

• 5 Alpha reductase inhibitors:

Finasteride

Dutasteride.

• Combination therapy of α1-adrenoceptor antagonists and 5 alpha reductase inhibitors.

• Emerging potential medication choices for male LUTS:

Anticholinergics, alone or in combination with α1-adrenoceptor antagonists

Phosphodiesterase type 5 inhibitors, alone or in combination with α1-adrenoceptor antagonists.

• Invasive treatments:

Prostatectomy (usually trans-urethral prostatectomy [TURP]). Usage has declined in recent years due to the efficacy of medications in reducing symptoms and preventing progression. A variety of methods of performing prostatectomy or ablation of the prostate gland have been described including high intensity ultrasound, microwave thermotherapy, needle ablation, electro-vaporization and laser therapy. Open retropubic prostatectomy is also used in particularly large prostates where the open operation is quicker and safer than TURP. Prostatectomy is more successful in patients with demonstrable BOO on pressure/flow cystometry than in patients without documented obstruction

Trans-urethral incision of the prostate. Generally used for smaller prostates, the procedure has less associated morbidity than prostatectomy

Prostatic stents. Have been used in elderly men not fit for surgery, who do not wish to be long term catheterized, but stents have a very limited role.

Catheterization to drain the bladder either with an indwelling catheter or CISC may be required in patients who are refractory to conservative or medical treatments and also in those who are not fit or are unwilling to undergo an invasive procedure.

CLINICAL NOTE: BENIGN PROSTATIC DISEASE

• Evaluation of a male patient includes obtaining an appropriate history and, physical examination, in addition to urinalysis, laboratory tests and uroflowmetry.

• Treatment is directed at improving quality of life, relieving BOO and resolving BOO complications.

• Watchful waiting and pharmacotherapy tend to be the choice of therapy for mild to moderate symptoms.

• TURP remains the ‘gold standard’ technique but there has been a dramatic decline in the number of procedures performed, due to the increasing use of effective medication.

Malignant prostatic obstruction

Benign and malignant prostatic diseases often co-exist, but the relationship appears to be coincidental, although both conditions are under the influence of the male hormone testosterone:

• carcinoma usually originates in the peripheral zone

• benign prostatic enlargement usually originates in the central peri-urethral zone.

Prostatic carcinoma must be ruled out in middle-aged and elderly men who present with storage or voiding LUTS, if carcinoma is discovered then it must be treated appropriately depending on the grade and stage of the disease and the medical condition of the patient, as per relevant guidelines. Initial screening during assessment of LUTS is usually with digital rectal examination (DRE) and serum prostate specific antigen (PSA); followed by trans-rectal ultrasound and prostatic biopsy if there is any suspicion of carcinoma.

Bladder neck obstruction

In this condition the bladder neck does not open completely during voiding and there is little or no flow during a well sustained detrusor contraction. Video urodynamics is necessary in order to make the diagnosis (Figure 6.1c). The condition is especially prevalent in younger men and also occurs occasionally in women; currently the aetiology of primary bladder neck obstruction is unknown. Theories for the cause include fibrosis, neurogenic dysfunction (detrusor/bladder neck dyssnergia) and smooth muscle hypertrophy, amongst others. On screening there may be trapping of contrast during the stop test (Figures 4.20 and 6.2).

Figure 6.2 Bladder neck obstruction/dyssynergia, showing trapping of contrast in the prostatic urethra during a stop test. During voiding the patient is instructed to stop his urinary stream: normally the contrast located in the prostatic urethra quickly milks back into the bladder; however, in patients with bladder neck dyssynergia, the tighter bladder neck resists retrograde flow, resulting in ‘ballooning’ of the prostatic urethra.

Treatment of bladder neck obstruction includes:

• Watchful waiting.

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Paediatric urodynamics Clinical evaluation of the lower urinary tract Urodynamic procedures Basic structure, function and control of the lower urinary tract Pressure/flow cystometry Storage disorders and incontinence

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