This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders in Menstruation, Subject name: Gynaecology & Obstetrics
A 14-year-old girl presents with primary amenorrhea and monthly lower abdomen pain. She has good secondary sexual characteristics with axillary and pubic hair. Examination of the external genitalia reveals a bulging bluish membrane. Most appropriate next step in diagnosis: 
Select and explain. 
A. Perform a hormonal profile, B. Perform a karyotype, C. Perform a laparoscopy, D. Perform an USG
D: Perform an USG
Answer: D: Perform an USG 
Explanation: Ans. is d, i.e. Perform an USGThis patient has imperforate hymen as she has monthly abdominal pain, good secondary sexual characteristics and a bulging bluish membrane (due to collection of blood in vagina) is seen.Most appropriate next step is to do an USG to confirm the presence of uterus, cervix and vagina.