Question
A 52-year-old man with long-standing acid reflux develops persistent diarrhoea, weight loss, and epigastric discomfort. Imaging detects a suspicious lesion, and blood tests show markedly elevated fasting gastrin levels.
Where are these hormone-secreting tumours most commonly found?
a. Distal ileum
b. Second part of duodenum
c. Gastric body
d. First part of duodenum
e. Jejunum
Answer
First part of the duodenum
Detailed Explanation
This is a classic presentation of Zollinger-Ellison syndrome, caused by a gastrinoma (gastrin-secreting neuroendocrine tumour).
- Gastrin → ↑ gastric acid secretion →
- Multiple peptic ulcers
- Diarrhoea (acid inactivates pancreatic enzymes → malabsorption)
- Weight loss
Location (Very High-Yield)
- Most common site → First part of duodenum (D1)
- Second most common → Pancreas
- These tumours arise in the “gastrinoma triangle”:
- D1–D2 of duodenum
- Pancreatic head
- Porta hepatis
Why D1?
- High concentration of G cells (gastrin-producing cells)
- Tumours originate from these cells → hence location specificity
Why NOT other options?
- Ileum / jejunum → No G cells → very rare
- Stomach (pylorus/body) → G cells mainly in antrum, but gastrinomas here are uncommon
- Distal duodenum → fewer G cells
Important associations
- ~25–30% associated with Multiple Endocrine Neoplasia type 1
- Parathyroid + pancreatic NETs + pituitary
Cheat Sheet (Exam Gold)
- Zollinger-Ellison = gastrinoma → ↑ gastrin → ↑ acid
- Classic triad:
- Refractory ulcers
- Diarrhoea
- Weight loss
- Most common site → D1 (first part of duodenum)
- Second → pancreas
- Think MEN1
- Diagnosis:
- ↑ fasting gastrin
- Secretin stimulation test
Flash Cards
Q1: Most common site of gastrinoma?
A: First part of duodenum
Explanation: Highest density of G cells
Q2: Why diarrhoea occurs in Zollinger-Ellison?
A: Acid inactivates pancreatic enzymes → malabsorption
Q3: What syndrome is gastrinoma associated with?
A: MEN1
Q4: Best initial diagnostic test?
A: Fasting gastrin level
Q5: Second most common location of gastrinoma?
A: Pancreas
MCQs
1. A patient with refractory peptic ulcers and diarrhoea most likely has a tumour in which location?
a. Ileum
b. First part of duodenum
c. Jejunum
d. Sigmoid colon
Answer: b
Explanation: Gastrinomas most commonly arise in D1
2. Which of the following is FALSE regarding gastrinomas?
a. Commonly occur in duodenum
b. Associated with MEN1
c. Common in ileum
d. Cause hyperacidity
Answer: c
Explanation: Ileum lacks G cells
3. Mechanism of diarrhoea in Zollinger-Ellison syndrome?
a. Increased motility only
b. Fat malabsorption due to bile deficiency
c. Acid inactivation of pancreatic enzymes
d. Villous atrophy
Answer: c
Explanation: Excess acid denatures enzymes
4. Which test best screens for gastrinoma?
a. Endoscopy
b. Serum amylase
c. Fasting gastrin level
d. Stool fat analysis
Answer: c
Explanation: Most sensitive initial test
5. A gastrinoma is most likely located within which anatomical region?
a. Gastric fundus
b. Ileocaecal junction
c. Gastrinoma triangle
d. Splenic hilum
Answer: c
Explanation: Includes D1, pancreas, porta hepatis
6. Which of the following is FALSE about Zollinger-Ellison syndrome?
a. Causes multiple ulcers
b. Causes hypochlorhydria
c. Associated with diarrhoea
d. May be part of MEN1
Answer: b
Explanation: Causes hyperchlorhydria, not hypo
Summary for Quick Exam Revision
Zollinger-Ellison syndrome is caused by a gastrin-secreting neuroendocrine tumour leading to excessive gastric acid production. Patients present with recurrent, treatment-resistant peptic ulcers, diarrhoea due to malabsorption, and weight loss. The most common location of gastrinomas is the first part of the duodenum, followed by the pancreas, both lying within the gastrinoma triangle. These tumours arise from G cells, explaining their typical anatomical distribution. Around one-third are associated with MEN1 syndrome, so screening for endocrine abnormalities is important. Diagnosis is primarily made using fasting gastrin levels, often followed by a secretin stimulation test for confirmation. The excessive acid leads to enzyme inactivation, resulting in steatorrhoea and diarrhoea. Recognising the location and pathophysiology is crucial for exam success, with “D1 duodenum = most common site” being a key high-yield fact.