A 30-year-old presents with profuse, foul-smelling vaginal discharge. What is the most likely diagnosis?

The correct diagnosis in this scenario is trichomoniasis, especially given the presentation of profuse and foul-smelling vaginal discharge. Trichomoniasis is a sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis. A hallmark of this condition is the characteristic discharge, which is often described as being copious and malodorous, typically presenting a yellow-green color.

In addition to the discharge, patients may experience associated symptoms such as itching, burning, and discomfort during intercourse or urination. The presence of the foul smell differentiates it from other conditions, as bacterial vaginosis, while it does cause a fishy odor, usually has a less copious discharge than trichomoniasis.

In contrast, vulvovaginal candidiasis often presents with a thick, white discharge that resembles cottage cheese and lacks the foul odor. Atrophic vaginitis is usually seen in postmenopausal women and presents with dryness, irritation, and sometimes minimal discharge, but not with a profuse or malodorous discharge. Thus, trichomoniasis aligns closely with the symptom of profuse and foul-smelling discharge, making it the most likely diagnosis.