In congenital dacryocystitis which structure is blocked?
**Core Concept**
Congenital dacryocystitis is an infection of the lacrimal sac present at birth, often due to a congenital anomaly. The **lacrimal apparatus** is responsible for tear production and drainage. The underlying issue in congenital dacryocystitis involves the blockage of a specific structure within this apparatus.
**Why the Correct Answer is Right**
The correct answer involves the blockage of the **nasolacrimal duct**, which is the structure responsible for draining tears from the eye into the nasal cavity. This duct is often blocked by a membrane at its lower end, known as **Hasner's valve**, which usually opens spontaneously after birth but sometimes remains closed, leading to duct obstruction.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect as it does not directly relate to the common cause of congenital dacryocystitis.
**Option B:** Similarly, this option does not accurately describe the primary issue in congenital dacryocystitis.
**Option C:** This choice is also incorrect as the blockage typically occurs at the level of the nasolacrimal duct, not another structure.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that congenital dacryocystitis often presents with **mucocele** or infection of the lacrimal sac, and the first line of treatment may involve **nasolacrimal duct probing** to relieve the obstruction.
**Correct Answer:** D. Nasolacrimal duct.