Differential Diagnosis for Lower Abdominal Pain in an 18-Year-Old Woman
Single Most Likely Diagnosis
- Dysmenorrhea: This condition is characterized by recurrent, crampy lower abdominal pain that occurs during menstruation, often radiating to the lower back and thighs. The patient's symptoms of pain during menses, worsening on the second day, and associated nausea and fatigue are classic for dysmenorrhea. The fact that her symptoms improved while on oral contraceptives, which are known to reduce menstrual cramps, further supports this diagnosis.
Other Likely Diagnoses
- Menorrhagia: Although the primary complaint is pain, the patient mentions heavy bleeding (requiring a pad change every 4 hours) and longer duration of bleeding, which could suggest menorrhagia. This condition often coexists with dysmenorrhea and could be contributing to her overall symptomatology.
- Endometriosis: Although less common in younger women, endometriosis can cause dysmenorrhea, dyspareunia, and heavy bleeding. The absence of pain with intercourse and no palpable adnexal masses makes this less likely, but it remains a consideration given her significant menstrual pain.
Do Not Miss Diagnoses
- Ectopic Pregnancy: Given the patient's history of inconsistent condom use, ectopic pregnancy must be considered, even though her symptoms are cyclic and suggest a menstrual cause. A pregnancy test should be performed to rule out this life-threatening condition.
- Pelvic Inflammatory Disease (PID): Although the patient does not report intermenstrual bleeding or pain with intercourse, PID can present with a range of symptoms, including lower abdominal pain. Her sexual activity with inconsistent condom use increases her risk for sexually transmitted infections, which can lead to PID.
Rare Diagnoses
- Adenomyosis: This condition, where endometrial tissue grows into the uterine wall, can cause dysmenorrhea and menorrhagia. However, it is less common in younger women and typically presents in older reproductive-aged women.
- Uterine Fibroids: While fibroids can cause heavy bleeding and pain, they are less common in women as young as 18 and would likely be palpable on a pelvic exam, especially if causing significant symptoms.