Bacterial Vaginosis (BV): Although BV typically presents with a malodorous discharge, some cases may not have a noticeable smell. The thick, brown, copious nature of the discharge, along with some discomfort, could still align with BV, especially if other symptoms like itching are present.

Trichomoniasis: This sexually transmitted infection can cause a copious, frothy, yellow-green or brown vaginal discharge. The absence of a smell does not rule out trichomoniasis, as the discharge's characteristics can vary.
Vaginal Candidiasis (Yeast Infection): While typically associated with a white, cottage cheese-like discharge, some cases of candidiasis can present with a brownish discharge, especially if there's bleeding or if the infection is complicated. Discomfort and itching are common.
Cervicitis: Inflammation of the cervix can lead to an abnormal vaginal discharge, which might be brown and copious. The discomfort could be related to the inflammation or to associated conditions like pelvic inflammatory disease (PID).

Cervical Cancer: Although rare, cervical cancer can cause abnormal vaginal bleeding or discharge, which might appear brown due to the presence of blood. Any abnormal discharge, especially in the context of other risk factors (e.g., HPV infection, abnormal Pap smear), warrants further investigation.
Pelvic Inflammatory Disease (PID): PID can cause a variety of symptoms, including abnormal vaginal discharge, pelvic pain, and discomfort. It's a critical diagnosis not to miss due to its potential for long-term complications like infertility and chronic pelvic pain.
Gonorrhea or Chlamydia: These sexually transmitted infections can cause cervicitis and abnormal discharge. While they might not always present with symptoms, when they do, it's crucial to diagnose and treat them promptly to prevent complications like PID.

Foreign Body: A retained foreign body in the vagina, such as a forgotten tampon, can cause a malodorous discharge. However, if the discharge is described as brown and without a significant smell, this might be less likely. Nonetheless, it's an important consideration, especially in cases where the discharge is accompanied by other symptoms like fever or severe pelvic pain.
Desquamative Inflammatory Vaginitis (DIV): A rare condition characterized by a purulent vaginal discharge, which can sometimes appear brown, and significant vaginal inflammation. It's often associated with discomfort and can be challenging to diagnose due to its rarity and similarity to other conditions.