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Bacterial vaginosis: don't miss the most common cause of vaginal discharge

In the second of our series on sexual health, Dr Olwen Williams advises

on the commonest ­ but least diagnosed ­ cause of vaginal discharge

Vaginal discharge is such a common problem that many practices have set up nurse 'vaginal discharge' clinics that work to protocols and patient group directives. Although superficially it may appear to be easy to diagnose and manage, the condition can become a challenge when the symptom becomes recurrent.

In an endeavour to shed light on the variety of causes of this symptom and aid in the management of the recurrent problem, let's consider bacterial vaginosis (BV) as it is by far the commonest, but possibly the least diagnosed, in primary care.

Prevalence has been estimated as between 10-30 per cent of women in the UK, rising to 24-37 per cent of women attending genitourinary medicine clinics, and 5-26 per cent in pregnant women.

Such high prevalence rates are of concern, particularly the pregnancy figures, as it puts women at greater risk of acquiring HIV and developing complications. BV may also be involved in pelvic inflammatory disease.

How it presents

It is a chronic recurrent condition, which is characterised by a grey watery vaginal discharge, which can have an offensive smell especially after intercourse (fishy) but with no vulval itching or soreness. It may be the woman's sexual partner who notices the odour and presents himself.

Up to 50 per cent of women may be entirely asymptomatic. Recurrence rates of 15-30 per cent within three months have been reported in women previously deemed to have been successfully treated. Some cases spontaneously resolve while others alternate between episodes of BV and vulvo-vaginal candidiasis.

Diagnosing BV

Relying on symptoms alone does not allow clinicians to confidently distinguish the condition.

Diagnosis is based on taking a thorough sexual history, speculum examination, pH paper test (pH>4.5), amine or 'whiff' test ­ release of a fishy odour on adding alkali (10%KOH) to a sample of discharge and high vaginal swab. Also request microscopy and, if there is access to a microscopy, direct visualisation of a gram stained specimen of discharge for the presence of 'clue cells', Gardnerella or Mobiluncus morphotypes.

Consider endocervical swabs for chlamydia, gonorrhoea, and high vaginal swab for trichomoniasis and candida.

Those at risk

Risk factors associated with BV include some associated with bacterial sexually transmitted infections such as chlamydia, such as more than one sexual partner in the past three months, past history of STI, black Caribbean ethnic origin and lower socio-economic class.

It is worth noting though that women with BV tend to be over 30 years of age. There is also a direct correlation with douching/vaginal cleansing and IUCD use.

There are many questions about the aetiology of BV. Despite the associations with STI, there is no evidence that the condition itself is sexually transmitted. Treating the male partner has no impact on recurrences in the female, although a change of partner does!

What we are aware of is the upset in vaginal flora with a reduction of lactobacilli and an increase of BV-associated organisms. There is a change in vaginal pH, but the trigger remains a mystery.

BV may appear to be a trivial condition but the recognised increased risk of HIV acquisition is important, as is the known association with premature rupture of membranes in pregnancy.

The GIFT study identified BV as being a significant factor in the development of pelvic inflammatory disease giving a three-fold increased risk but only when either chlamydia or gonorrhoea or both organisms were present.

Managing BV

Management should involve advising women not to douche, and to curtail the use of shower gel, antiseptic agents or shampoo in the bath. Antimicrobial intervention is recommended in symptomatic women, women undergoing termination of pregnancy and some pregnant women.

Treatment has traditionally been with oral metronidazole 400mg bd for seven days, or a single dose 2g metronidazole. Topical vaginal preparations are popular and effective. Metronidazole vaginal gel 0.75% nightly for five days or clindamycin vaginal cream nightly for seven days can be used.

Intercourse may be messy with the vaginal preparations and the metronidozole gel tastes bitter, so is best avoided. Cure rates at one week are 80-90 per cent. Recurrence rates are similar regardless of which therapy used. There is no superior therapy and combinations of these therapies offer no advantage.

Women should be advised that the condition is a recurrent phenomenon and eventually will remit spontaneously. Reassurance that it is not a sexually transmitted infection is essential.

Treating pregnant women

The presence of bacterial vaginosis during the second trimester increases the risk of miscarriage significantly, and should be treated with the appropriate antimicrobials. Some clinicians recommend clindamycin 300mg bd for five days as clinical trials have shown a decrease in the incidence of miscarriage. However, there is concern about its safety in the neonate.

An alternative regimen is metronidazole 400mg twice daily for seven days. No fetal abnormalities have been reported in humans and clinicians are advised it is safe to use in pregnancy.

Recent research

Attempts at improving the management of BV have been based on what is currently known about its aetiology.

Recolonisation of the vagina with lactobaciili through both oral and vaginal lactobacilli preparations have been unsuccessful using yoghurt products, but oral Lactobaciili acidophilus and vaginal pessaries containing Lactobaciili crispartus have shown a 57 per cent and 40 per cent clearance of BV in asymptomatic women. The condition

recurred after menstruation in the trial with

L. acidophilus. More trials are in progress.

Rebalancing the vaginal pH using lactate gel per vagina three days immediately after menstruation for six months resulted in

88 per cent of women in the active arm of a small study being BV free compared with

10 per cent on placebo.

Lactate gel is well tolerated, but is currently not available outside clinical

trials.

Prophylactic antimicrobial treatment to prevent overgrowth of BV-associated organisms has been evaluated. Intermittent therapy with either oral or vaginal metronidazole on the first three days of the menstruation for three-six months may benefit some women.

This troublesome condition for both the patient and doctor alike will persist until the underlying mechanisms of its aetiology is elucidated. In the meantime, reassurance and use of conventional therapies are the mainstay of management.

Olwen Williams, consultant genitourinary physician,Wrexham Maelor Hospital, and chair of the British Association for Sexual Health and HIV's adolescent and sexual health special interest group

Take-home points

·Bacterial vaginosis is not a sexually transmitted infection

·It's the commonest cause of vaginal discharge in the UK

·Diagnosis is made on microscopy

·Recurrence rates are similar regardless of the therapy used

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