Why do you need EUS after a Gastroscopy? Answers from a Gastroenterologist

What is Endoscopic Ultrasound (EUS)?

Endoscopic Ultrasound (EUS) is a technique that combines endoscopy and ultrasound to examine the digestive tract. This method places a high-frequency ultrasound probe at the end of an endoscope or inserts a mini ultrasound probe through the endoscope channel. When the endoscope is inserted into the digestive tract, it allows direct visualization of the digestive tract lesions while using ultrasound to scan the structure of the digestive tract wall and surrounding tissues in real-time.

EUS can provide detailed images of the layers of the gastrointestinal tract and surrounding organs, helping to differentiate the nature of digestive tract lesions, assess their invasion depth and extent, and distinguish between benign and malignant changes. EUS is highly sensitive, with an accuracy rate of over 95% in diagnosing biliary and pancreatic diseases. It has unique advantages over CT, MRI, and MRCP, especially in detecting small lesions such as those in the pancreas, ampulla <1cm, and common bile duct <0.5mm.

In recent years, EUS has become the preferred diagnostic method for patients with biliary and pancreatic diseases. It can also guide the biopsy of deeper tissues and organs, and even provide treatment for biliary and pancreatic diseases through techniques such as puncture, drainage, injection, and particle implantation.

Clinical Applications of EUS

1. Diagnosing Submucosal Lesions of the Digestive Tract

The digestive tract can be divided into five layers from the inside out: mucosa, muscularis mucosa, submucosa, muscularis propria, and serosa. Traditional endoscopy only visualizes the mucosal layer, but some lesions originate from deeper layers. EUS combines endoscopy and ultrasound to better observe and diagnose submucosal structures or lesions.

▲ Stomach Wall Structure, Gastric Fundus Elevation, Muscularis Propria

2. Staging of Digestive Tract Tumors

▲ Gastric Cancer, Ultrasound Image of Gastric Cancer

By placing the probe on the surface of a tumor, EUS can determine the depth and extent of tumor invasion and its relationship with nearby organs, blood vessels, and lymph nodes, providing critical information for treatment planning.

3. Diagnosing Gastrointestinal Lymphoma

Gastrointestinal lymphomas often infiltrate the submucosa or muscularis propria. EUS can assess the affected layers, measure the thickness of the involved wall, guide deep biopsy sampling, and evaluate the condition of surrounding lymph nodes.

▲ Gastric Lymphoma, Ultrasound Image of Gastric Lymphoma

4. Diagnosing Pancreatic Diseases

EUS can scan the pancreatic parenchyma to detect small lesions that B-ultrasound and CT cannot identify. It can also perform fine-needle aspiration (EUS-FNA) for biopsy of the lesion, aiding in disease staging by evaluating surrounding lymph nodes and organs.

▲ Pancreatic Head Cyst EUS-FNA, Mediastinal Lymph Node EUS-FNA

5. Diagnosing Liver, Biliary, and Ampullary Lesions

For patients with obstructive jaundice, EUS can accurately locate the obstruction site and determine whether the cause is a stone, tumor, or other disease by examining the morphology and echo characteristics of the obstruction and evaluating the involvement of surrounding organs.

▲ Gallstones, Common Bile Duct Stones

6. Diagnosing Peptic Ulcers

EUS can observe the structural destruction and rupture of the digestive tract wall at the ulcer site. After medical treatment, EUS can monitor the healing of ulcers by assessing the integrity of the wall layers.

▲ Gastric Body Ulcer, Ultrasound Image of Gastric Body Ulcer

7. Diagnosing Mediastinal Lesions

EUS can scan the mediastinum through the esophagus, assessing the echo characteristics and relationships of lesions with surrounding organs, guiding fine-needle aspiration (FNA) for pathological diagnosis.

▲ Mediastinal Mass Biopsy

8. Minimally Invasive Treatments

With advances in endoscopic equipment, EUS can guide the placement of drainage tubes and stents for internal drainage of pancreatic pseudocysts and abscesses, or administer treatments such as drug injections into cysts.

▲ Cyst Puncture and Drainage Process

Indications for EUS

1. Diagnosis of suspected gastrointestinal cancer and assessment of invasion depth.
2. Diagnosis of submucosal tumors such as leiomyomas, stromal tumors, and lipomas.
3. Staging of malignant gastrointestinal tumors to assess invasion depth and metastasis.
4. Differential diagnosis of ulcerative lesions.
5. Diagnosis of pancreatic diseases such as chronic pancreatitis, pancreatic tumors, and pancreatic cysts.
6. Diagnosing biliary system diseases like common bile duct stones, gallstones, and biliary tumors.
7. Assessing esophageal and gastric varices and the effectiveness of embolization treatment.
8. Diagnosing mediastinal lesions.

Absolute Contraindications

1. Severe cardiopulmonary diseases that preclude endoscopy.
2. Critical conditions such as shock.
3. Suspected gastric perforation.
4. Uncooperative patients with mental illness or severe intellectual disability.
5. Acute oral, pharyngeal, esophageal, or gastric inflammation, especially corrosive inflammation.
6. Other conditions such as significant aortic aneurysm or cerebrovascular disease.

Pre-exam Preparation for EUS

1. Patients should fast for at least 6-8 hours. Eat a low-residue, easy-to-digest meal the night before the exam.
2. Upper GI exams require local anesthesia with lidocaine gel and lubrication. Lower GI exams require bowel preparation with a cleansing agent.
3. Patient positioning for EUS is similar to that for standard endoscopy.
4. During EUS, the endoscope is inserted into the digestive tract to scan submucosal lesions, tumors, and adjacent organs.

Post-exam Care

Routine EUS does not require special care. Generally, patients should refrain from eating or drinking for 2 hours post-exam. If fine-needle aspiration (FNA) or other treatments were performed, follow the doctor's post-operative instructions for observation and care.