## **Core Concept**
The coeliac plexus block is a procedure used to manage abdominal pain, particularly for patients with chronic pancreatitis or other conditions causing severe abdominal pain. The coeliac plexus, also known as the solar plexus, is a complex network of nerve fibers located in the upper abdomen, playing a crucial role in transmitting pain signals from the abdominal organs.

## **Why the Correct Answer is Right**
The most common complication of a coeliac plexus block is **hypotension**. This occurs because the block affects the sympathetic nerves that innervate the abdominal organs, leading to vasodilation of the splanchnic vessels. As a result, there's a decrease in systemic vascular resistance, which can cause a drop in blood pressure. The coeliac plexus block involves injecting a local anesthetic or neurolytic agent near the coeliac plexus, which can temporarily or permanently disrupt the transmission of pain signals but also affects the sympathetic outflow, leading to hypotension.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While diarrhea could potentially occur due to the effects on the autonomic nervous system, it is not the most common complication of a coeliac plexus block.
- **Option B:** Infection is a potential complication of any invasive procedure, including a coeliac plexus block, but it is not the most common complication specifically associated with this procedure.
- **Option C:** While various gastrointestinal symptoms could occur, they are not as commonly associated with the immediate effects of a coeliac plexus block as hypotension.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that patients undergoing a coeliac plexus block should be monitored for hypotension, and the procedure often requires a period of post-procedure observation to manage potential blood pressure changes. Pre-procedure hydration and possibly the use of vasopressors are considered to mitigate this risk.

## **Correct Answer:** D. Hypotension