Bacterial Vaginosis (BV): This condition is characterized by an imbalance in the normal vaginal flora, leading to an overgrowth of anaerobic bacteria. It is a common cause of foul-smelling vaginal discharge in women of all ages, including the elderly. The symptoms and age of the patient make BV a highly plausible diagnosis.

Vaginal Candidiasis: Although more commonly associated with a thick, white discharge, some cases of vaginal candidiasis can present with a foul odor, especially if there is a secondary bacterial infection.
Atrophic Vaginitis: This condition, resulting from the thinning and drying of the vaginal walls due to decreased estrogen levels, can lead to vaginal discharge. While the discharge is typically not foul-smelling, the condition can increase the risk of infections that might cause a foul odor.
Urinary Tract Infection (UTI): UTIs can sometimes present with vaginal discharge, especially if the infection has spread to the kidneys or if there is an associated condition like incontinence. The foul smell could be from the infection itself or from incontinence.

Cervical or Endometrial Cancer: Although less common, these cancers can present with abnormal vaginal discharge, which may have a foul odor. Given the potential severity of these conditions, it is crucial not to miss them, even if they are less likely.
Foreign Body: The presence of a foreign body in the vagina, such as a retained tampon, can cause a foul-smelling discharge. This is a medical emergency and must be ruled out.
Pelvic Inflammatory Disease (PID): PID is an infection of the female reproductive organs that can cause a range of symptoms, including foul-smelling vaginal discharge. It is essential to diagnose and treat PID promptly to prevent long-term complications.

Vaginal Tumors (Benign or Malignant): While rare, tumors of the vagina can cause abnormal discharge, which might be foul-smelling.
Rectovaginal Fistula: An abnormal connection between the rectum and vagina can lead to the passage of fecal material into the vagina, resulting in a foul-smelling discharge. This condition is rare but requires surgical intervention.
Diverticulitis or Other Gastrointestinal Conditions: In rare cases, conditions affecting the gastrointestinal tract, such as diverticulitis, can lead to symptoms that might be mistaken for a gynecological issue, including foul-smelling discharge if there is a fistula involved.