Makindo Medical Notes

Related Subjects: |Achalasia |Oesophageal Carcinoma |Diffuse Oesophageal spasm |Diffuse Oesophageal Perforation - Rupture |Gastro-Oesophageal Reflux |Barrett's oesophagus

Gastrinoma

Gastrinoma is a rare, gastrin-secreting tumour that causes excessive gastric acid production, often leading to recurrent and severe peptic ulcer disease. It is the main cause of Zollinger-Ellison syndrome.

About

• A gastrinoma is a neuroendocrine tumour that secretes excessive gastrin, which stimulates the stomach to produce high levels of gastric acid, resulting in peptic ulcer disease.
• Most gastrinomas are located in the pancreas or the duodenum (known as the "gastrinoma triangle" area), though they can occasionally be found in the stomach or other locations.
• Gastrinoma is the most common cause of Zollinger-Ellison syndrome (ZES).

Aetiology

• Gastrinoma is often sporadic but can be associated with Multiple Endocrine Neoplasia type 1 (MEN-1)), a genetic condition that predisposes individuals to develop multiple endocrine tumours.
• Excessive gastrin secretion from the tumour leads to continuous stimulation of gastric acid production, causing damage to the gastric mucosa and resulting in multiple and severe peptic ulcers.

Clinical Features

• Peptic ulcer disease: Seen in approximately 90% of cases, often presenting with multiple or recurrent ulcers that are resistant to standard ulcer therapies.
• Abdominal pain and dyspepsia: Symptoms often mimic those of regular peptic ulcer disease but are typically more severe and resistant to treatment.
• Diarrhoea and malabsorption: Excess acid can damage the small intestine and interfere with nutrient absorption.
• Complications include gastrointestinal bleeding, ulcer perforation, and gastric outlet obstruction due to extensive ulceration.

Investigations

• Serum gastrin levels: Elevated in gastrinoma but can also be raised in achlorhydria, acid-suppressing drugs, G cell hyperplasia, and gastric outlet obstruction. Levels over 1000 pg/mL with high basal gastric acid secretion are suggestive of gastrinoma.
• Secretin stimulation test: Used to confirm gastrinoma. In gastrinoma, IV administration of secretin paradoxically raises gastrin levels, distinguishing it from other causes of hypergastrinemia.
• Imaging studies:
  • Endoscopic ultrasound (EUS): Highly sensitive for locating tumours in the pancreas and duodenum.
  • CT or MRI: Used for tumour localization and assessing metastasis, particularly to the liver.
  • Somatostatin receptor scintigraphy (Octreoscan): Useful for locating neuroendocrine tumours that express somatostatin receptors, including gastrinomas.
• Additional tests for MEN-1: Screen for MEN-1 in cases of gastrinoma with genetic testing and evaluation of other potential endocrine tumours (e.g., parathyroid and pituitary glands).

Management

• Medications:
  • Proton pump inhibitors (PPIs): High-dose PPIs are the mainstay of treatment to reduce acid secretion and manage symptoms.
  • H2 receptor antagonists: Can also be used but are generally less effective than PPIs for acid suppression.
  • If associated with MEN-1, manage coexisting endocrine conditions such as hypercalcaemia, which can exacerbate acid production.
• Surgical resection: If the tumour is localized and resectable, surgery may be curative. Surgery is more complex when hepatic metastases are present, which occurs in 50% of gastrinomas at diagnosis.
• Vagotomy: In severe or refractory cases, vagotomy (cutting the vagus nerve) may be considered to reduce gastric acid production.
• Palliative care for metastatic disease:
  • Somatostatin analogues (e.g., octreotide): Used to control symptoms and tumour growth in cases of metastatic disease.
  • Targeted therapy and chemotherapy: Options like sunitinib or everolimus may be considered in advanced metastatic cases.

Prognosis

• Prognosis depends on the tumour stage and presence of metastases. Localised gastrinomas without metastasis have a favourable prognosis, whereas metastatic gastrinomas, particularly to the liver, are associated with poorer outcomes.

References

• Zollinger-Ellison Syndrome Overview
• Endocrine Tumors Treatment Guide