Causes of Brown Vaginal Discharge
Brown vaginal discharge most commonly represents old blood that has oxidized, arising from either physiologic menstrual shedding (spotting at cycle start/end), endometrial pathology, cervical lesions, or atrophic vaginitis in postmenopausal women; any postmenopausal brown discharge mandates urgent referral to exclude endometrial or cervical cancer. 1
Age-Stratified Differential Diagnosis
Reproductive-Age Women
Physiologic causes:
- Intermenstrual spotting at the beginning or end of menses, representing residual endometrial shedding that oxidizes to brown before expulsion 2
- Midcycle ovulatory bleeding due to estrogen withdrawal at ovulation 2
- Implantation bleeding in early pregnancy, though any bleeding in reproductive-age women must exclude pregnancy complications (threatened abortion, ectopic pregnancy, trophoblastic disease) 3
Pathologic reproductive tract disease:
- Cervical lesions: polyps, erosion, cervicitis, or cervical malignancy—all identifiable on speculum examination 4, 3
- Endometrial polyps or submucosal leiomyomas causing irregular shedding 3
- Endometritis or chronic pelvic inflammatory disease 3
- Adenomyosis or endometriosis 3
Iatrogenic causes:
- Hormonal contraceptives (oral contraceptives, intrauterine devices, progestins) causing breakthrough bleeding 3
- Anticoagulant therapy 3
Postmenopausal Women
Brown discharge in this population is endometrial or cervical cancer until proven otherwise and requires urgent referral. 1
- Endometrial carcinoma (present in ~10% of postmenopausal bleeding cases, peak incidence 65–75 years) 1
- Cervical carcinoma 1
- Vaginal atrophy (the most common benign cause, due to estrogen deficiency causing friable mucosa) 1
- Endometrial hyperplasia ± polyp 1
- Cervical polyps 1
- Hormone-producing ovarian tumors 1
Adolescents
- Anovulatory cycles are common in the first 1–2 years post-menarche, causing irregular brown spotting 4
- Coagulopathies (von Willebrand disease) should be considered in adolescents with menorrhagia or persistent irregular bleeding 3
Diagnostic Approach
History must identify:
- Timing relative to menstrual cycle, duration, and associated symptoms (pain, odor, pruritus) 4
- Pregnancy risk and last menstrual period 3
- Medication history: hormonal contraceptives, HRT, tamoxifen, anticoagulants 1
- Risk factors for endometrial cancer: obesity, nulliparity, PCOS, unopposed estrogen 1
Physical examination:
- Speculum examination to visualize the cervix and identify polyps, erosion, friability, malignancy, or atrophic changes 4, 1
- Assess for cervical motion tenderness or adnexal masses suggesting infection or ectopic pregnancy 3
- Bimanual examination to detect uterine enlargement (fibroids, adenomyosis) or adnexal masses 1
Laboratory and imaging:
- Urine or serum β-hCG in all reproductive-age women to exclude pregnancy 3
- Transvaginal ultrasound in postmenopausal women: endometrial thickness <5 mm with normal examination and resolved bleeding requires no further workup; thickness ≥5 mm mandates endometrial biopsy 1
- Endometrial biopsy for histologic diagnosis in postmenopausal women or those with risk factors for hyperplasia/cancer 1
- Cervical cytology and/or biopsy if cervical lesions are visualized 1
- Coagulation studies (PT, aPTT, von Willebrand panel) in adolescents with menorrhagia or women with refractory bleeding 3
Critical Pitfalls to Avoid
- Never assume brown discharge is benign in postmenopausal women—10% harbor endometrial cancer and all require urgent evaluation 1
- Always exclude pregnancy in reproductive-age women before attributing bleeding to other causes 3
- Do not overlook coagulopathies in adolescents with heavy or prolonged bleeding; von Willebrand disease is underdiagnosed 3
- Recognize that normal vaginal discharge can vary in color and quantity across the menstrual cycle; physiologic discharge at cycle extremes may appear brown without pathology 5
- Distinguish vaginal bleeding from urethral (hematuria) or rectal sources during speculum examination 1