Most common site of obstruction in chronic dacryocystitis in adults is:
**Core Concept**
Chronic dacryocystitis is an inflammatory condition of the lacrimal sac, often resulting from nasolacrimal duct obstruction. The lacrimal sac is a small, mucosal-lined pouch located in the medial orbit, and its drainage is facilitated by the nasolacrimal duct.
**Why the Correct Answer is Right**
The most common site of obstruction in chronic dacryocystitis in adults is the **distal end of the nasolacrimal duct**. This area is prone to stenosis or blockage due to chronic inflammation, scarring, or anatomical variations. The distal end of the nasolacrimal duct is surrounded by the nasal mucosa, which can cause irritation and lead to obstruction. The lacrimal sac, being the reservoir for tears, becomes distended and inflamed, leading to symptoms of chronic dacryocystitis.
**Why Each Wrong Option is Incorrect**
* **Option A:** The proximal end of the nasolacrimal duct is less likely to be obstructed in adults, as it is closer to the lacrimal sac and less prone to scarring or stenosis.
* **Option B:** The lacrimal canaliculi are small, mucosal-lined channels that collect tears from the eye and drain into the lacrimal sac. While they can be obstructed, they are not the most common site of obstruction in chronic dacryocystitis.
* **Option C:** The lacrimal sac itself can become distended and inflamed in chronic dacryocystitis, but it is not the most common site of obstruction.
**Clinical Pearl / High-Yield Fact**
The distal end of the nasolacrimal duct is a common site of obstruction in chronic dacryocystitis due to its proximity to the nasal mucosa, which can cause chronic inflammation and scarring.
**Correct Answer: C. The lacrimal sac itself can become distended and inflamed in chronic dacryocystitis, but it is not the most common site of obstruction.**