**Question:** Most common cause of pyometra is:

A. Ovarian torsion
B. Ovarian cyst rupture
C. Cervical stenosis
D. Endometrial cancer

**Core Concept:**
Pyometra is a medical condition characterized by the accumulation of pus in the uterine cavity, typically caused by a failure in the normal process of uterine emptying after childbirth or menses. Pyometra can lead to severe complications if left untreated.

**Why the Correct Answer is Right:**
The correct answer is **D. Endometrial cancer**. Endometrial cancer is the most common cause of pyometra in postmenopausal women. This is because postmenopausal women have a reduced risk of uterine contractions due to the lack of estrogen stimulation. As a result, the uterine cavity remains filled with blood and secretions, leading to the formation of pus (pyometra).

**Why Each Wrong Option is Incorrect:**

A. **Ovarian torsion (ovarian cyst rupture)**: These conditions are not directly related to the uterine cavity. Ovarian torsion and rupture can lead to acute abdominal pain and potential complications, but they do not explain the accumulation of pus in the uterine cavity.

B. **Ovarian cyst rupture**: Similar to option A, ovarian cyst rupture does not directly cause pyometra in the uterine cavity. Although it can lead to acute abdominal pain, it does not account for the pus accumulation in the uterine cavity.

C. **Cervical stenosis**: Cervical stenosis would lead to an obstructed cervical canal, potentially causing infertility but does not explain pyometra in the uterine cavity.

**Clinical Pearl:**

Pyometra is a critical medical condition that requires prompt attention and intervention. In postmenopausal women, it is essential to consider endometrial cancer as the primary cause, as it results in reduced uterine contractions and subsequent pus accumulation. In contrast, the other options do not directly explain the formation of pyometra in the uterine cavity.