**Core Concept**
Morrison's pouch is an anatomical structure in the liver that plays a crucial role in the formation of ascitic fluid. It is a peritoneal recess located between the liver and the diaphragm, which can accumulate fluid due to various pathological conditions.

**Why the Correct Answer is Right**
Morrison's pouch is a potential space where fluid can collect due to increased pressure or decreased lymphatic drainage. This fluid accumulation can lead to the formation of ascites, which is a common complication in patients with liver cirrhosis, heart failure, or other conditions that impair lymphatic drainage. The fluid in Morrison's pouch can be reabsorbed or drained through the lymphatic vessels, but in cases of severe fluid accumulation, it can lead to respiratory complications due to the pressure exerted on the diaphragm.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Morrison's pouch is not a part of the gallbladder's anatomy.
**Option B:** This option is incorrect because the hepatoduodenal ligament is not a peritoneal recess, but rather a fibrous structure that supports the liver's blood vessels and bile ducts.
**Option C:** This option is incorrect because the omental bursa is a larger peritoneal cavity located behind the stomach and the liver, but it is not the specific structure referred to as Morrison's pouch.

**Clinical Pearl / High-Yield Fact**
Morrison's pouch is an important anatomical landmark in the diagnosis and management of ascites, and its presence can be confirmed through imaging studies such as ultrasound or CT scans.

**Correct Answer: C. Omental bursa (also known as the lesser sac).**