It's a busy Monday morning in the pharmacyand you are at the counter giving advice to a patient who has just collected his inhaler. As you finish and the patient turns to leave, a woman steps forward, saying: "Excuse me, I know you're very busy but could I have a word? In private, if possible."

The woman sits down in the consulting room and says: "I'm sorry to make a fuss, it's just I've got this awful discharge - you know, down below - and it really smells. I'm a married mum of two with another on the way, and I'm mortified. What can I do?"

Symptoms

Vaginal discharge is usually nothing to worry about. All menstruating women - though not those on hormonal contraceptives - will experience discharge that changes throughout their menstrual cycle. For most of the month, it will be thick and sticky, but around ovulation it becomes clearer, thinner and stretchy.

Abnormal vaginal discharge is characterised by a change in colour, odour, consistency or quantity, and may be accompanied by other symptoms, such as itching, soreness, pain, dysuria, and abnormal vaginal bleeding.

Causes

The causes of abnormal vaginal discharge fall into two categories: infections and non-infective causes. Infections are by far the most common cause, with bacterial vaginosis (BV) the most common culprit in women of childbearing age.

BV is caused by an overgrowth of anaerobic bacteria (particularly Gardnerella vaginalis, but also Prevotella and Mobiluncus species, and Mycoplasma hominis) and a loss of the lactobacilli usually present in the vagina, which in turn results in the pH rising from its usual 4.5 to as high as seven.

About half of women suffering from BV will be asymptomatic, but those who do have symptoms are likely to report a fishy-smelling discharge.

Other infective causes of abnormal vaginal discharge include the sexually transmitted infections chlamydia, trichomoniasis and gonorrhoea. However, these are more common in younger women and those who have recently changed their sexual partner, and are distinguished from BV by the accompanying symptoms of itching, soreness or irritation, all of which are generally absent in BV, and a different type of discharge.

Vaginal candidiasis (thrush) can cause abnormal vaginal discharge, but - as with the STIs listed above - is easily distinguishable from BV by accompanying symptoms and the type of discharge, which tends to be thick, white and yeasty-smelling.

Non-infective causes of abnormal vaginal discharge include a retained foreign body such as a tampon or condom, inflammation due to irritation or allergy (eg to soaps or lubricants), tumours of the vulva, vagina, cervix or endometrium, cervical erosion or polyps, and atrophic vaginitis, which can occur in post-menopausal women.

Back in the pharmacy, the woman tells you she has no symptoms other than the vaginal discharge, which she describes as more watery than usual and "smelling like old fish," particularly after sexual intercourse. You explain these are classic symptoms of BV, adding - when she asks in horror if she has an STI - that it is the most common cause of vaginal discharge in women of childbearing age and that the reason why it occurs is uncertain, but it is certainly not sexually transmitted and can occur in women who are not having sex.

Risk factors

Although BV isn't an STI, it is more common in women who are sexually active. It is also more common in those who have recently changed their sexual partner, black women, smokers and those who use an intrauterine device or system. Hormonal changes during the menstrual cycle and having unprotected sex also seem to increase the risk of developing BV, as do certain lifestyle factors such as using highly scented soaps or bath products, using vaginal deodorants or douches, and detergent residues on underwear.

Your patient says she recently started using a vaginal wash as she was worried that she might smell because she had more vaginal discharge than normal. On gentle questioning, you discover that this was around a month or so ago, and at the time the discharge wasn't smelly, just present in larger quantities than usual. You explain that increased discharge is entirely normal during pregnancy - particularly the second trimester - and add that vaginal deodorants and washes are not generally recommended (and certainly not during pregnancy).

Diagnosis

If there are no symptoms other than the characteristic fishy-smelling vaginal discharge, a diagnosis of BV is generally made, as long as the woman is considered at low risk of an STI (aged over 25 years and with no new sexual partners in the last 12 months), has not recently had a gynaecological procedure (including childbirth, miscarriage or termination), has not suffered BV recently or recurrently, and is not pregnant. If these criteria are not met, a speculum examination should be performed, and a vaginal swab taken for testing for infections and pH.

All pregnant women with suspected BV should undergo vaginal swabbing and pH testing to confirm the diagnosis before treatment is started.

The patient in front of you is five months pregnant, so you advise her to see her GP as soon as possible for testing. She says she will ask to be examined or referred when she sees the midwife the next day.

Management

Only women who have symptoms need to be treated, unless a pregnant woman is discovered to have BV during other tests (see Complications). Non-pregnant women who are asymptomatic but are diagnosed with BV (again, usually during other tests) should be allowed to opt for treatment if they wish.

The recommended first-line treatment is metronidazole 400mg tablets, twice daily for seven days. The drug is around 80 per cent effective, well-tolerated and inexpensive. If treatment adherence is likely to be an issue, a single dose of metronidazole 2g may be used, though this is not thought to be as effective as the week's antibiotic course.

The main side effects are gastro-intestinal including nausea, vomiting, an unpleasant taste and furred tongue. Metronidazole enhances the effects of coumarin anticoagulants, fluorouracil, phenytoin and lithium. The main caution to patients is to avoid alcohol, which produces a disulfiram-like reaction.

For women who cannot tolerate oral metronidazole, intravaginal metronidazole gel (0.75 per cent, once daily for five days) or intravaginal clindamycin cream (2 per cent, once daily for seven days) may be used. Both are as effective as a weekly course of oral metronidazole but are considerably more expensive. Oral alternatives to metronidazole include clindamycin 300mg twice daily for seven days or tinidazole 2g as a single dose, though again neither is considered first-line because they are considerably more expensive than oral metronidazole, and there is less evidence supporting their use in BV.

The same treatments may be used in both pregnant and non-pregnant women, though topical clindamycin is considered safer during pregnancy than systemic, a metronidazole course is preferable to a single high dose, and tinidazole is not recommended during the first trimester.

Testing is not generally recommended to ensure treatment has worked - patient reporting of symptom resolution is considered sufficient.

The only exception is pregnant women, who should be examined and tested one month after treatment to ensure the infection has cleared. Symptoms that do not resolve are usually due to poor treatment adherence or misdiagnosis.

You advise the woman that - if your diagnosis of BV is confirmed - she is likely to need a course of metronidazole. She says she has taken it in the past for a dental problem, but is worried it may harm her unborn baby.

Complications

BV is generally a straightforward condition - easy to diagnose and treat in symptomatic women, with low risk of complications or treatment failure. However, the exception is when BV occurs in pregnancy, when it is associated with late miscarriage, pre-term labour and birth, low birthweight and postpartum endometriosis. Similarly, BV has been found in some women who have had a miscarriage, gone into labour prematurely or had a low birthweight baby, though it is not known whether the infection was the cause of these events. For these reasons, women who have previously had a premature birth or recurrent miscarriages will usually be offered testing for BV (alongside other conditions, such as several STIs).

You reassure the patient that a course of metronidazole is considered safe for use in pregnancy and state that the benefits of treating the condition outweigh the risks of leaving it untreated (though you opt not to expand on the reasons why, deciding that this could cause her distress and is better dealt with by the midwife or GP once BV has been definitely diagnosed).

Recurrence

Although certain factors put women at a higher risk of BV, its onset and resolution can be spontaneous, hence the rationale for not treating asymptomatic sufferers. However, some women may suffer recurrent symptoms, and are considered to have recurrent BV if they suffer four times a year or more despite adhering to the recommended treatments as outlined above.

Such women should be referred to a gynaecologist or genito-urinary specialist, who may recommend using metronidazole 0.75 per cent gel twice weekly for four to six months (after initial treatment with oral metronidazole for 10 days) to suppress symptoms, or regular three-day courses of metronidazole 400mg tablets twice daily every menstrual cycle for a number of months. There is a lack of published evidence on treating women with recurrent BV.

Further information

• NHS Clinical Knowledge Summaries www.cks.nhs.uk/bacterial_vaginosis/management

• British Association for Sexual Health and HIV
www.bashh.org/documents/62/62.pdf

Asha Fowells MRPharmS is a practising community pharmacist and a training development manager at C+D.

Reflect

Which bacteria are responsible for bacterial vaginosis? How do the symptoms of BV differ from those of thrush? Why should pregnant women with BV be treated even if they are asymptomatic?

Act

This article describes the symptoms and treatment of bacterial vaginosis, with information about causes, risk factors, complications and the treatment of pregnant women.

Plan

Find out more about BV from the Patient UK website, including advice about preventing recurrence, at http://tinyurl.com/y9ppsjl.

More advice about BV can also be found at the Women’s Health Concern website at http://tinyurl.com/ydqpyzc.

Read more about the treatment of BV in pregnancy at the NHS Clinical Knowledge Summaries website at http://tinyurl.com/ya4wy5b.

From the Patient UK website, revise your knowledge of other conditions that may cause a vaginal discharge at http://tinyurl.com/yce8ocp.

Evaluate

Are you now confident in your knowledge of the symptoms and treatment of bacterial vaginosis? Could you advise patients about this condition and how to prevent recurrence?