Colonscopy performed on a 25 year old woman with eating disorder showed dark brown to black pigmentary deposit in the lining of the large intestine. Histopathology of biopsy revealed pigment laden macrophages within the lamina propria The woman on probing revealed use of laxatives for the 9 months to lose weight. What could be the probable laxative agent that could have caused these findings?

**Core Concept**
The question is testing the ability to identify a specific laxative agent causing melanosis coli, a condition characterized by the deposition of pigment in the colon lining. Melanosis coli occurs due to the chronic use of certain laxatives that contain anthraquinones.

**Why the Correct Answer is Right**
The chronic use of laxatives containing anthraquinones leads to the accumulation of these compounds in the colon, which are then phagocytosed by macrophages in the lamina propria. This results in the formation of pigment-laden macrophages, characteristic of melanosis coli. The most common anthraquinone laxatives are senna and cascara sagrada.

**Why Each Wrong Option is Incorrect**
* **Option A:** Bisacodyl is a stimulant laxative that works by increasing peristalsis, but it does not contain anthraquinones and is not associated with melanosis coli.
* **Option B:** Polyethylene glycol (PEG) is an osmotic laxative that works by drawing water into the colon, but it does not contain anthraquinones and is not associated with melanosis coli.
* **Option C:** Docusate is a stool softener that works by increasing the water content of the stool, but it does not contain anthraquinones and is not associated with melanosis coli.

**Clinical Pearl / High-Yield Fact**
Beware of the "hidden" laxative use in patients with eating disorders, as it can lead to unsuspected complications like melanosis coli.

**Correct Answer:** C. Cascara sagrada.

✓ Correct Answer: A. Senna