Sexually Transmissible Infections in Clinical Practice

10. Vaginal Discharge (2)

Alexander McMillan1, 2  


Department of Genitourinary Medicine, NHS Lothian, Edinburgh Royal Infirmary, Edinburgh, Uk


University of Edinburgh, Edinburgh, Uk

Alexander McMillanFormerly, Consultant Physician, part-time Senior Lecturer



Mary is a 26-year-old woman who attends a Sexual Health clinic. For the preceding 2 weeks she has noticed a profuse, yellow vaginal discharge that has a rather musty smell. She also has noted mild irritation on the vulva and she has had some discomfort on passing urine. She is otherwise symptomless. Her menstrual periods are regular; the most recent began 21 days previously and was of usual character. Her general health is good and there is no past history of any sexually transmissible infections.

Mary is a 26-year-old woman who attends a Sexual Health clinic. For the preceding 2 weeks she has noticed a profuse, yellow vaginal discharge that has a rather musty smell. She also has noted mild irritation on the vulva and she has had some discomfort on passing urine. She is otherwise symptomless. Her menstrual periods are regular; the most recent began 21 days previously and was of usual character. Her general health is good and there is no past history of any sexually transmissible infections.

You elicit a sexual history as described in Case 2Four weeks before she attends you she had returned to the United Kingdom from India where she had taught English in a rural school. She had had unprotected vaginal intercourse with a local man with whom she had had a 2-month relationship. Her most recent sexual contact with him had been 2 days prior to her departure from India.

10.1 What Conditions Would You Consider in the Differential Diagnosis?

The causes of increased vaginal discharge are shown in Table 9.1. Bacterial vaginosis is usually associated with a white vaginal discharge, and unless there is concurrent infection with, for example, Candidaspp., pruritus vulvae is not a feature. Pruritus vulvae is the cardinal symptom of candidiasis, and as Mary has noticed only mild vulval irritation, this is not the most likely diagnosis. Gonococcal and chlamydial infections can cause increased vaginal discharge and dysuria, but the profuse discharge that Mary describes would be unusual. Trichomoniasis, caused by the flagellated protozoan Trichomonas vaginalis, may be associated with an increased yellow vaginal discharge and dysuria. Primary genital herpes usually causes marked vulval pain and dysuria and is therefore an unlikely diagnosis here. The symptoms of recurrent genital herpes, however, are usually less severe and can include vulval irritation and dysuria; the profuse discharge described by Mary would, however, be unusual. The presence of a foreign body such as a retained tampon is often associated with a profuse foul-smelling vaginal discharge, and this needs to be excluded.

When you examine Mary you find that there is marked reddening of the introitus, but there is no ulceration. There is no foreign body in the vagina, but the walls are inflamed and a frothy yellow discharge pools in the posterior fornix.

10.2 What Investigations Would You Undertake?

Although the clinical appearance is strongly suggestive of trichomoniasis, this is not pathognomic, and laboratory tests are required to confirm the diagnosis (see Case 2). On microscopy of a wet preparation Trichomonas vaginalis, which is larger than a polymorphonuclear leucocyte but smaller than an epithelial cell, is readily recognized by its usually rapidly moving flagella, the rippling movement of the undulating membrane, and the jerky movements of the organism. Ideally the specimen should be examined immediately but if this is impracticable the swab should be placed preferably in transport medium such as Amies’.

Ideally, a vaginal specimen should be sent to the laboratory for culture. Cultivation for T. vaginalis, however, is regarded by many as expensive and time consuming, and it is not widely available. The detection of specific DNA by polymerase chain reactions appears to be more sensitive than wet smear microscopy and culture, and nucleic acid amplification tests (NAATs) for the diagnosis of vaginal trichomoniasis are available in some UK clinics.

A Gram-stained smear of vaginal exudate is also prepared for microscopical examination for Candida spp. Material from the endocervical canal is obtained for Gram-smear microscopy and culture or NAAT for Neisseria gonorrhoeae, and a sample is also obtained for the detection of Chlamydia trachomatis (see Case 2).

The urethra should be sampled using a 10 μL plastic inoculating loop for the detection of N. gonorrhoeae by Gram-smear microscopy and culture or NAAT.

Syphilis is more prevalent in India than in the United Kingdom, and serological tests, for example, the anti-treponemal enzyme immunoassay, should be undertaken. As the pre-patent period of syphilis is up to 90 days, a further blood sample should be tested 3 months after the most recent sexual contact in India, if the initial test is negative. At least 50% of individuals with infectious syphilis are symptomless and have no signs of infection. These infected persons can only be identified by serological testing.

As the incidence of HIV is increasing in India, it is worth counseling Mary about this infection and the advantages of having an HIV antibody test at an appropriate time (see Case 1).

The saline-mount preparation of vaginal exudate shows T. vaginalis. When you examine the Gram-stained smear of vaginal material you find many polymorphonuclear leucocytes (Fig.10.1 ), lactobacilli are absent, and no fungal hyphae are seen. Gram-negative diplococci suggestive of Neisseria gonorrhoeae are not identified in Gram-stained smears from the endocervical canal and urethra.


Figure 10.1.

Polymorphonuclear leucocytes in Gram-stained vaginal smear.

As trichomonads cannot be identified reliably in a Gram-stained smear, this is not a useful diagnostic test. Women with trichomoniasis often show similar vaginal pH changes and alteration to the vaginal microflora as found in bacterial vaginosis (see Case 9).

10.3 What Treatment Would You Provide, and What Follow-Up Would You Offer?

Metronidazole is the treatment of choice. Recommended treatment regimens for adults are shown in Table 10.1

Table 10.1.

Drug regimens for the treatment of trichomoniasis.

Metronidazole as a single oral dose of 2 g, given either in tablet form (four, 400 mg tablets) and taken during or after a meal or in suspension taken at least 1 h before a meal


Metronidazole 400–500 mg twice daily, during or after a meal, for 5–7 days

At the dose generally used for trichomoniasis, metronidazole is well tolerated and during more than 30 years of its widespread use, it has earned a reputation of being remarkably safe. Occasional side effects at these doses include nausea, an unpleasant taste in the mouth, furring of the tongue and gastrointestinal upsets; headache, dizziness, anorexia, depression, and skin eruptions have been reported but rarely.

Mild-to-moderate disulfiram-like effects have been described (e.g., facial flushing, headache, nausea, and sweating) with metronidazole, following alcohol ingestion. Adverse effects of concurrent metronidazole and alcohol are infrequent but patients should be advised about these possibilities in the event of alcohol being ingested during metronidazole therapy and for at least 48 h after its completion.

There is no evidence that metronidazole is teratogenic or associated with birth defects. It is recommended, however, that high doses of the drug should be avoided in pregnancy.

You arrange to see Mary 1 week later to ensure that treatment has been successful and to provide the results of the other laboratory tests. You also suggest that her partner be treated for trichomoniasis.

10.4 What Are the Clinical Features of Trichomoniasis in Men, and How Is the Condition Diagnosed?

About 50% of men with trichomoniasis are symptomless. When there are symptoms, urethral discharge that is usually small to moderate in amount is the most common feature. Frequency of micturition and mild dysuria may also be features. Balanoposthitis, which may rarely be ulcerative, may be associated with. T. vaginalis infection.

If a urethral discharge is present, this can be collected with a 10 μL inoculating loop, otherwise a scraping should be taken gently from the urethra before the patient passes the first morning urine. A saline-mount preparation is made as in the female and examined microscopically for T. vaginalis. If possible, urethral material should be cultured for the organism, or tested by a NAAT. A centrifuged deposit (600g) of a 20 mL urine sample taken preferably after the patient has held his urine overnight may also be examined microscopically, by culture or by a NAAT.

As re-infection of the sexual partner is almost invariable if he is not treated, the man should be given metronidazole, irrespective of the laboratory findings if tests are undertaken (empirical therapy is often given without the undertaking of tests).

When Mary attends for follow-up she states that her vaginal discharge persists. You now have the results of the other laboratory tests. Although Gram-smear microscopy for N. gonorrhoeae was negative, the organism was cultured from the endocervical canal and urethra. Chlamydia trachomatis was also detected in the endocervical canal. Serological tests for syphilis and for HIV were negative. Saline-mount microscopy of vaginal exudate once again shows T. vaginalis. You treat the gonococcal and chlamydia infections with the appropriate antimicrobial drugs and arrange the necessary follow-up (seeCase 8 ). She has telephoned her partner in India, and he has sought treatment there.

The importance of screening for other sexually transmitted infections (STIs) in individuals in whom one is detected is shown in this case. In the past, trichomoniasis was associated with other STIs in up to 40% of women attending sexually transmitted diseases clinics in the United Kingdom during the 1960s.

Treatment failure is more often the result of failure to adhere to the treatment regimen, vomiting of the drug, or re-infection than to drug resistance. Inability to produce trichomonicidal concentrations in vaginal tissue of fluid may contribute to treatment failure. Sometimes persistent infection may result from inactivation of metronidazole by vaginal aerobic and anaerobic bacteria, and treatment with a course of amoxicillin or erythromycin before re-treatment with metronidazole may be effective. Resistance to the 5-nitroimidazoles, of which metronidazole is one such drug, does occur, but facilities to test for susceptibility to these drugs are unavailable outwith a research setting. As metronidazole resistance is relative rather than an all-or-one phenomenon, many women infected with resistant stocks of T. vaginaliscan be cured by increasing doses of metronidazole. For example, metronidazole can be given in an oral dose of 400 mg three times daily, with the insertion of a 1 g suppository rectally once daily, for at least 7 days. The intravenous route can be used if the woman cannot tolerate the oral formulation. The drug can also be given in a daily oral dose of 2 g for 3–5 days. Alternatively, as this drug may be more active against some stocks of T. vaginalis, high doses of tinidazole (2 g daily for 14 days) may affect cure in women with refractory trichomoniasis.