Key differential diagnoses for a patient presenting with abnormal vaginal discharge include infectious, inflammatory, and neoplastic causes. The most common infectious causes are bacterial vaginosis, candidiasis, and sexually transmitted infections such as trichomoniasis, chlamydia, and gonorrhoea. Bacterial vaginosis typically presents with a thin, greyish discharge and a fishy odour, while candidiasis is associated with thick, white, curd-like discharge and itching. Trichomoniasis often causes a frothy, yellow-green discharge with vaginal irritation. Other causes include non-infectious inflammatory conditions such as atrophic vaginitis, especially in postmenopausal women, and foreign bodies. Neoplastic causes, including cervical or vaginal cancer, should be considered particularly if discharge is persistent, bloody, or associated with other symptoms such as pelvic pain or weight loss NICE NG201 Sheeley 2004.
In addition, pelvic inflammatory disease (PID) can present with abnormal discharge alongside pelvic pain and systemic symptoms. Less common causes include cervicitis from non-sexually transmitted pathogens and dermatological conditions affecting the vulva. A thorough history, examination, and appropriate investigations are essential to differentiate these causes and guide management NICE NG201 Sheeley 2004.