**Core Concept**
Gastric diverticulum is a true diverticulum of the stomach wall, usually occurring in the upper portion of the stomach. The pathophysiology of gastric diverticulum involves the weakening of the gastric wall, often due to chronic inflammation, which can lead to symptoms such as epigastric pain.

**Why the Correct Answer is Right**
The most frequent symptom of gastric diverticulum is epigastric pain, which is caused by the irritation of the gastric wall and surrounding tissues. This irritation can lead to inflammation and scarring, resulting in chronic pain. The location of the diverticulum, typically in the upper stomach, is also a contributing factor, as it can irritate nearby structures such as the diaphragm and abdominal muscles, causing referred pain.

**Option A:**
* **Option A:** Epigastric pain is indeed a common symptom of gastric diverticulum, as it is a direct result of the irritation and inflammation caused by the diverticulum.

**Option B:**
* **Option B:** Haematemesis, or vomiting blood, is not a typical symptom of gastric diverticulum, as it is more commonly associated with conditions such as peptic ulcer disease or gastric cancer.

**Option C:**
* **Option C:** Vomiting is not a primary symptom of gastric diverticulum, although it may occur in some cases due to associated conditions such as gastritis or obstruction.

**Option D:**
* **Option D:** Pain relieved by food is not characteristic of gastric diverticulum, as the pain is typically constant and not alleviated by eating.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that gastric diverticulum is often asymptomatic, and symptoms may only arise when the diverticulum becomes inflamed or irritates surrounding structures.

**Correct Answer:**
✓ Correct Answer: A. Epigastric pain