ACOG Classification of Dysmenorrhea
ACOG classifies dysmenorrhea into two distinct categories: primary dysmenorrhea (menstrual pain without pelvic pathology) and secondary dysmenorrhea (menstrual pain resulting from underlying pelvic disease such as endometriosis). 1
Primary Dysmenorrhea
Primary dysmenorrhea is defined as cramping pain in the lower abdomen and/or pelvis that occurs just before or during menstruation, in the absence of identifiable pelvic pathology, typically lasting 1-3 days with a negative physical examination. 2, 3
Key diagnostic features include:
- Pain caused by prostaglandin production (specifically prostaglandins F2α and E2) leading to increased uterine contractility 4, 5
- Onset shortly before or at the start of menses 5
- Duration of 1-3 days 2
- Normal pelvic examination findings 2, 6
- Affects 50-90% of adolescent girls and women of reproductive age 3
Secondary Dysmenorrhea
ACOG specifically describes secondary dysmenorrhea in the context of endometriosis as pain that commences before the onset of the menstrual cycle, often accompanied by deep dyspareunia that is exaggerated during menses, or sacral backache with menses. 1
Key distinguishing features that suggest secondary dysmenorrhea include:
- Progressive worsening of pain over time 3
- Abnormal uterine bleeding 3, 6
- Dyspareunia (painful intercourse) 3, 6
- Noncyclic pain patterns 6
- Changes in intensity and duration of pain 6
- Abnormal pelvic examination findings 6
- Vaginal discharge 3
Common causes of secondary dysmenorrhea:
- Endometriosis (most common cause) 6, 4
- Adenomyosis (presents with dysmenorrhea, menorrhagia, and uniformly enlarged uterus) 6, 4
- Uterine fibroids 2
- Pelvic anatomic abnormalities 3
- Pelvic infection 3
Clinical Approach to Classification
When evaluating dysmenorrhea, ACOG's framework requires ruling out secondary causes before diagnosing primary dysmenorrhea. 7, 6 The presence of any red flag features (progressive pain, abnormal bleeding, dyspareunia, abnormal examination) mandates further investigation with transvaginal ultrasonography and potentially hysteroscopy. 7, 6
Important caveat: The depth of endometriosis lesions correlates with severity of pain, but the pain associated with endometriosis has little relationship to the type of lesions seen by laparoscopy. 1 This means that even minimal endometriosis can cause significant secondary dysmenorrhea, making the distinction between primary and secondary dysmenorrhea clinically challenging without definitive diagnostic procedures.