M/c cause of B/L cornual block seen on HSG:
**Core Concept**
The question is testing the understanding of the most common cause of bilateral cornual block seen on hysterosalpingography (HSG), which is a diagnostic imaging technique used to evaluate the shape of the uterus and fallopian tubes. Cornual block refers to the obstruction of the fallopian tubes at the cornual region, where they connect to the uterus.
**Why the Correct Answer is Right**
The most common cause of bilateral cornual block is _endometriosis_. Endometriosis is a condition in which tissue similar to the lining of the uterus grows outside the uterus, leading to inflammation and scarring in the fallopian tubes, particularly at the cornual region. This scarring can cause a blockage of the fallopian tubes, preventing the egg from traveling through to the uterus. Other causes of cornual block, such as Asherman's syndrome, are less common.
**Why Each Wrong Option is Incorrect**
**Option A:** Tuberculosis is a common cause of tubal blockage, but it typically affects one tube at a time, rather than causing bilateral cornual block.
**Option B:** Adenomyosis is a condition in which tissue from the uterine lining grows into the muscular wall of the uterus, but it is not typically associated with cornual block.
**Option C:** Uterine fibroids are benign growths in the uterus, but they are not typically associated with cornual block.
**Clinical Pearl / High-Yield Fact**
It's worth noting that endometriosis is a common cause of infertility, and HSG can be a useful diagnostic tool in evaluating the shape of the uterus and fallopian tubes in patients with suspected endometriosis.
**Correct Answer:** D.