A 40 years old multi gravida woman comes to the hospital with two months history of worsening right pelvic pain. She experiences the pain daily. The intensity does not vary with menstruation. The patient’s waist size was increased despite her poor appetite. The pelvic examination shows irregularly shaped fixed adnexal mass. One week later, the patient undergoes surgery for removal of large ovarian neoplasm. Within the true pelvis, the surgeon can most likely palpate the right ureter immediately anterior to

## **Core Concept**
The question tests the knowledge of pelvic anatomy, specifically the relationship between the ureters and surrounding structures within the true pelvis, which is crucial during surgical procedures like the removal of ovarian neoplasms to avoid ureteral injury.

## **Why the Correct Answer is Right**
The correct answer, **C. Internal iliac artery**, is based on the anatomical relationship of the ureters with the pelvic vasculature. As the ureters enter the pelvis, they are located anterior to the internal iliac arteries (also known as hypogastric arteries) and lateral to the uterosacral ligaments and the cervix. During a surgical procedure in the pelvis, such as the removal of an ovarian neoplasm, identifying these anatomical landmarks is essential to prevent ureteral damage. The ureters pass under the uterine arteries (which are branches of the internal iliac arteries) and then continue laterally along the pelvic sidewall, anterior to the internal iliac arteries.

## **Why Each Wrong Option is Incorrect**
- **Option A: External iliac artery** - The ureters do pass near the external iliac arteries as they exit the abdominal cavity and enter the pelvis, but within the true pelvis, they are more closely associated with the internal iliac artery branches.
- **Option B: Uterosacral ligament** - While the ureters do pass under or near the uterosacral ligaments as they approach the cervix, they are not described as being immediately anterior to these ligaments.
- **Option D: Obturator nerve** - The obturator nerve is located more laterally in the pelvis and is not directly anterior to the path of the ureters as they course through the true pelvis.

## **Clinical Pearl / High-Yield Fact**
A key point to remember during pelvic surgeries, such as the removal of ovarian neoplasms, is that the ureters are most at risk near the uterine arteries (where they pass underneath) and along the pelvic sidewalls. Surgeons often use specific techniques, like dissecting the ureters away from the surgical site or using ureteral stents, to minimize the risk of ureteral injury.

## **Correct Answer: C. Internal iliac artery**

✓ Correct Answer: C. Internal iliac artery