The urinary tract and its relationship to gynaecology

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Chapter 39 The urinary tract and its relationship to gynaecology

CHAPTER CONTENTS

Mechanics of voluntary micturition 308
Urinary incontinence (involuntary micturition) 309

Urge incontinence (overactive bladder syndrome) 309
Urethral sphincter incontinence 310
Diagnostic measures to determine the cause of the incontinence 310
Treatment 311
Urinary tract infection 312

Clinical aspects 312
Investigations 312
Treatment 313
The urethral syndrome 313
Urethral problems 313

Urethral prolapse 313
Urethral caruncle 313

The close connection of the bladder to the vagina and the short urethra give rise to more problems in a woman’s urinary tract than in a man’s. The anatomy of the urinary tract is described on page 343. The function of the urinary tract is to permit waste products of metabolism to be removed from the body in the urinary flow. For this reason the mechanics of micturition will be discussed first.

MECHANICS OF VOLUNTARY MICTURITION

The bladder fills as urine trickles down the ureters. To accommodate the urine the bladder distends, and it can accommodate 300–400 mL of urine without any increase in the resting intravesical pressure, which remains below 10 cmH2O. In the resting state the urethrovesical junction is flat and there is an angle of about 90° between the bladder and the urethra (the urethrovesical angle) (Fig. 39.1A).

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Fig. 39.1 Tracing from radiographs of the bladder and urethra. (A) At rest; (B) during micturition.

Continence is maintained because of the inherent tone of the urethra and by the muscles that envelop the urethrovesical junction and the proximal urethra, which keep the intraurethral pressure 7–10 cmH2O higher than the pressure within the bladder.

When more than 350 mL of urine distends the bladder, cholinergic muscarinic stretch receptors in the bladder wall are stimulated. This causes the detrusor muscle to contract and the intravesical pressure rises. Paradoxically, the extension of the detrusor muscle, which surrounds the proximal urethra in a spiral fashion, relaxes, with the result that the intraurethral pressure falls below the intravesical pressure. By the age of 5 most children have learned to inhibit the detrusor contractions and to keep the urethra closed, so that micturition can be delayed until an appropriate time. In some women, this higher centre control cannot be maintained and micturition occurs inappropriately. A second line of defence against involuntary micturition is provided by the muscles forming the external urethral sphincter and the fibres of the pubococcygeal muscle that surround and support the distal urethra.

When the person is ready to pass urine the detrusor muscle is permitted to contract strongly, which raises the intravesical pressure above the intraurethral pressure. The detrusor contractions also cause funnelling of the bladder base and obliterate the urethrovesical angle (Fig. 39.1B).

At the same time, the person contracts the abdominal muscles, which raises the intravesical pressure further. These changes and the relaxation of the proximal urethral muscle permit urine to pass into the urethra. The person now relaxes the muscles surrounding the distal urethra, and urine is voided until the bladder is empty. When this occurs the detrusor ceases to be stimulated and relaxes, and the urethrovesical angle is restored. The proximal urethra contracts from its distal end to the urethrovesical junction, ‘milking’ back a few drops of urine into the bladder. Finally, the external sphincter closes.

URINARY INCONTINENCE (INVOLUNTARY MICTURITION)

As women grow older the incidence of urinary incontinence increases, often causing social isolation or psychological problems. In the 35–50-year age group 5% of women are incontinent at least once each week. By the age of 60, 15–20% of women complain of urinary incontinence, and by the age of 80 one woman in four is incontinent.

In women two main and two subsidiary forms of urinary incontinence occur. The two main forms are:

• Urge incontinence
• Urethral sphincter incontinence (genuine stress incontinence).

The two subsidiary forms are:

• Reflex incontinence
• Overflow incontinence.

Of the subsidiary forms, reflex incontinence is an involuntary loss of urine due to abnormal reflex activity in the spinal cord in the absence of a desire to pass urine. Overflow incontinence (urinary retention with overflow) occurs in:

• Motor neurone disease
• Urethral obstruction, which is rare in women
• Cases of chronic bladder distension.

The proportion of women complaining of the two main forms of incontinence is not known. The best estimates are shown in Table 39.1.

Table 39.1 Percentage prevalence of the types of urinary incontinence

Type of Incontinence Age (Years)
  <70 >70
Urethral sphincter 50 26
Urge incontinence 20 33
Mixed 30 41

Urge incontinence (overactive bladder syndrome)

In this disorder the detrusor muscle contracts involuntarily. There are two categories of urge incontinence. In the first, sensory incontinence, the woman passes urine, not because of involuntary detrusor activity but because it hurts if she does not empty her bladder. The woman has to micturate frequently, often several times at night as well as during the day, and may have dysuria. In some cases there is obvious urinary tract infection. In others no evidence of this is found.

In the second category, motor urgency (detrusor instability), the urge to micturate before the bladder is full occurs at variable intervals and variable amounts of urine are voided. This may be accompanied by urinary frequency and incontinence if the woman is unable to reach a toilet. At night she may wet the bed. Pain on micturition is not a feature.

Urethral sphincter incontinence

In urethral sphincter incontinence, involuntary loss of urine occurs when the intravesical pressure exceeds the intraurethral pressure in the absence of detrusor activity. Two defects are thought to be present. The first is that the proximal urethra has been displaced downwards through the urogenital diaphragm. When the abdominal pressure rises, as occurs when a woman sneezes, coughs or is jolted, the pressure is not transmitted to the urethra, with the result that the intravesicular pressure rises although the intraurethral pressure does not. The second mechanism is that, either because of defective development of the urethral supporting muscles or damage to the bladder neck supports during childbirth, when the bladder is at rest its base is funnelled, not flat. This impairs the normal closure mechanism at the urethrovesical junction.

The combined effect of these mechanisms is to increase the intravesical pressure above the intraurethral pressure in the absence of a voluntary pressure increase. This results in a leak of urine into the urethra when only a small increase in intra-abdominal pressure occurs.

Clinical findings

The mechanisms explain the clinical findings, which are that the woman complains that a small amount of urine leaks if she laughs, coughs or jumps. The leak can be confirmed if her doctor asks her to cough when she has a full bladder.

Diagnostic measures to determine the cause of the incontinence

A woman presenting with a complaint of urinary incontinence requires careful examination. The social inconvenience caused by the incontinence should be evaluated. The woman should be asked if she is taking any medications, as some drugs (for example tricyclics, prazosin and lithium) may cause symptoms of urinary incontinence. General medical conditions, such as parkinsonism, multiple sclerosis and diabetic neuropathy, must be looked for and excluded, as should local bladder causes, such as bladder stone or pressure on the bladder from a myoma. The physical examination should include assessment of the perineal reflexes of segments S1–S4, and the anal sphincter tone should be tested. A specimen of midstream urine should be obtained and sent to a laboratory to exclude the possibility of bladder infections.

To try to identify the main (or the only cause) of the incontinence, tests should be arranged.

Pad test

The woman is asked to place a weighed pad (with a waterproof backing) over her vulva. Then she drinks 500 mL of sodium-free liquid over a 15-minute period. For the next 30 minutes she performs a range of activities, such as climbing a flight of stairs, walking, standing up from sitting, and washing her hands under running water. The pad is then removed and weighed again, any weight difference being urinary loss.

Urinary diary

If urge incontinence is suspected, the woman is asked to record her daily fluid intake and output each time she drinks or passes urine.

Urodynamic studies

Because the history gives a poor discrimination between the two main types of incontinence, urodynamic studies are used to provide a definitive diagnosis. This is especially important if a woman has had previous surgery for urinary incontinence. Urge incontinence and urethral sphincter incontinence can coexist, and urodynamic studies allow an assessment of which is dominant and hence whether treatment should be primarily medical or surgical. Inappropriate surgery which obstructs urinary outflow will cause even greater detrusor instability, hence the importance of reaching the right diagnosis before embarking on any form of surgery.

Urodynamic studies measure the change in intravesical and intraurethral pressure as fluid is instilled into the bladder. In urge incontinence the intravesical pressure rises early and the capacity of the bladder is diminished; in urethral sphincter incontinence the bladder capacity is usually normal and the pressure does not rise until just before capacity is reached.

Treatment

Urge incontinence/overactive bladder syndrome

Several strategies are recommended but the success rate is variable. Behavioural therapy and pelvic floor exercises are helpful. The aim of treatment is to help the woman to increase the time between episodes of micturition, no matter how difficult she finds it. The objective is to retrain her bladder to contain more urine before detrusor activity is stimulated. Considerable support and help, preferably from a trained person, is needed.

Drugs may also be helpful. As detrusor activity is under cholinergic control, anticholinergic drugs are chosen e.g. oxybutynin (2.5–5.0 mg three times a day) or tolterodine 1–2 mg twice a day. Both have been shown to be more effective than non-drug treatments, A number of women cannot take oxybutynin because of the anticholinergic effects of dry mouth, dry skin, blurred vision or constipation. These women may find relief if they take imipramine 10 mg twice a day plus 25 mg nocte. Bladder retraining programmes for urge incontinence have a success rate of 80–90%. Adrenergic agents, such as phenylpropanolamine, are more effective than placebo, but the definitive treatment is still being sought.

Urethral sphincter incontinence

Unless the incontinence is severe, the choice of medical or surgical treatment should be offered to the patient. Obese women should try to reduce their weight, as this has been found to relieve incontinence in some cases. A chronic cough should also be treated. Postmenopausal women need additional treatment, especially if they have recurrent urinary tract symptoms. These symptoms occur because of atrophy of the urethral mucosa. The women should be treated for 2–3 months with an oestrogen vaginal pessary, ovoid or cream, as well as antibiotics if indicated. Pelvic floor exercises should be initiated (Box 39.1). The exercises must be continued for several months. An alternative, which many women may find more convenient, is the use of vaginal cones. Weighted vaginal cones (in sets of five weighing 20–90 g) are purchased. The woman inserts the lightest cone into her vagina. It is kept in by contraction of the levator ani muscle. She progresses from the lightest cone to the heaviest.

Box 39.1 Pelvic floor exercises

These exercises help a woman strengthen the muscles which act as a sling to keep the bladder, the genital organs and the rectum in their correct position. She should try to do the exercises at least once a day, for the rest of her life.

At first the exercises may be a little tiring but with perseverance she will find them easy to do. The pelvic floor exercises only take about 2 minutes of each day and relieve urinary problems.

The exercises are easy to learn. No one can detect that a woman is doing them so they may be done in company, when watching TV, while travelling on a bus or in a car while stopped at the ‘stop’ lights, at work, etc.

The exercises have three components:

1. When she is sitting down the woman should contract the pelvic floor muscles, as if trying to lift the genital organs from the seat. The contraction should be held for a slowly counted 5 seconds. After each contraction relax. Repeat the exercise 10 times.
2. The woman should stand up and contract the pelvic floor muscles as if she were trying to stop the flow of urine midstream, or if she were tightening her vagina. Hold the contraction for 5 seconds, then relax. Repeat the exercise 10 times.
3. Finally do a fast version of the exercise, contracting and relaxing every second, 20 times.

Women can check their progress if they wish and can make sure that they are contracting the right muscles by inserting a finger into the vagina and feeling the strength of the contraction.

If the exercises are followed as described, after a week or two she will be pleased with the improvement of the grip.

These measures effectively relieve urinary sphincter incontinence in up to 60% of affected women. If they fail, or the woman chooses surgery, several surgical approaches are possible. Most gynaecologists prefer an operation that elevates the bladder neck so that it lies within the abdominal pressure zone (Fig. 39.2) and provides support under the urethrovesical junction. One example is shown in Figure 39.3. Another option is tension-free vaginal tape (TVT), which can be inserted under regional or local anaesthesia as a same-day procedure. The operations have similar success rates of over 90% in the immediate postoperative years, but long-term studies show that 6 years after the operation only 75% of women are continent and 15–20% have detrusor instability. Uterovaginal prolapse is increased in some treated women. Whether this is due to the operation or to a general weakness of the uterovaginal supports, which also caused the incontinence, is not known.

image

Fig. 39.2 The effect of the position of the bladder neck on stress incontinence. In (A) the urethrovesical junction occupies a normal position. An increase in abdominal pressure acts equally on the detrusor pressure and on the bladder neck pressure, with the result that the pressure gradient is maintained and a positive ‘closure’ pressure is present. In (B) the urethrovesical junction lies outside the effects of abdominal pressure as the junction is below the pelvic floor. An increase in abdominal pressure is transmitted only to the detrusor pressure, which exceeds momentarily the intraurethral pressure. The positive closure pressure is lost and the patient passes a small amount of urine.

image

Fig. 39.3 Modified colposuspension (retropubic approach). Sutures are placed between the paravaginal fascia and the ileopectineal ligaments. These sutures elevate the bladder neck. The sutures on the right have been tied; those on the left are ready to be tied. During exertion the intra-abdominal pressure rises and presses the urethra against the symphysis pubis, thus controlling the incontinence.

Women who are frail or who do not want surgery may be helped by using a bladder-neck support prosthesis. The device has two prongs, which elevate the urethrovaginal junction to its normal anatomic position (Fig. 39.4) without compressing the urethra. The device is removed at intervals for cleaning or if the woman has sexual intercourse. The appropriate size of prosthesis must be fitted by a doctor. A success rate of more than 80% is claimed.

image

Fig. 39.4 A bladder neck support prosthesis.

URINARY TRACT INFECTION

The short urethra and its intimate relationship with the vagina increases the chance that a woman will develop urinary tract infection. When the woman becomes sexually active, penile thrusting may move bacteria that have colonized the lower urethra upwards to infect the bladder. This may lead to symptomatic infection or to asymptomatic bacteriuria (>100 000 organisms per mL of urine), which affects 3–8% of sexually active women. Provided that the woman empties her bladder regularly the condition is without consequence, but should urinary stasis occur, as in pregnancy, the bacteria may grow in the urine, causing clinical acute infection. Initially, the infection is confined to the bladder, causing cystitis, but may spread either along the ureter or via the lymphatics to infect the kidney, causing pyelonephritis.

Clinical aspects

The symptoms of lower urinary tract infection (UTI) are frequency of micturition and dysuria; if the kidneys are involved, the woman will be febrile and may have rigors and loin pain.

Investigations

The woman should be asked if she has had previous attacks of UTI and whether she has an irritating vaginal discharge which, if present, should be investigated. Her recent sexual activity should be explored and a urethral discharge looked for. A midstream specimen of urine should be obtained and sent for examination and culture.

Treatment

Antibiotics are prescribed. The antibiotic chosen depends on local conditions. Norfloxacin 800 mg in a single dose, or Augmentin, is currently recommended. If the patient has pyelonephritis aggressive treatment is needed. Parenteral cefalexin 1 g, followed by 500 mg 6-hourly, is appropriate therapy.

THE URETHRAL SYNDROME

In this syndrome the woman complains of dysuria, frequency and pain, which usually start 12–36 hours after sexual intercourse. The symptoms last for 1–4 days and recur when sexual intercourse is resumed, although not every time. If the symptoms are severe and recur frequently they can cause a considerable disruption to the relationship, and often sexual frustration.

Investigation includes taking a careful history and examination. Vaginal swabs should be taken, as some women with the syndrome are found to have vaginitis. A midstream specimen of urine is also taken. This either fails to show any bacterial growth, or shows a concentration of bacteria of less than 100 organisms per mL. Some women are cured if they drink 500 mL of water before intercourse, and empty the bladder completely 20–30 minutes after having sex. If this simple measure fails to cure the condition, pelvic floor exercises in combination with antibiotics may be tried.

URETHRAL PROBLEMS

Urethral prolapse

In the acute form, the entire circumference of the urethra suddenly everts and becomes engorged, as the venous return is impeded (Fig. 39.5A). The woman, who is usually elderly, complains of pain, dysuria and frequency. The immediate treatment is to reduce the prolapse and insert a catheter. Surgery may be offered later.

image

Fig. 39.5 Urethral prolapse and urethral caruncle.

In the chronic form, atrophy of the urethral tissues may permit the external urinary meatus to gape and allow the posterior urethral wall to prolapse (Fig. 39.5B). The prolapse appears as a small red swelling and is painless. If it becomes infected, it becomes larger and painful. Treatment consists of applying an antiseptic ointment and an oestrogen cream. If the symptoms persist, surgery should be suggested.

Urethral caruncle

This is a pedunculated polyp arising from the posterior margin of the urinary meatus (Fig. 39.5C). It is vascular, dull red and tender. The patient complains of pain, frequency and dysuria. Treatment consists of excising the caruncle and cauterizing its bed.

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