A stomach ulcer, also known as a peptic ulcer, is an open sore that develops on the inner lining of the stomach or the first part of the small intestine, the duodenum. When patients experience symptoms like gnawing abdominal pain, a computed tomography (CT) scan is often used to investigate the cause. While a CT scan provides detailed cross-sectional images of internal organs, it is generally not the most effective method for detecting a simple, non-complicated ulcer. Although it can rule out other serious conditions, a standard CT scan often misses the ulcer itself due to imaging limitations.
Understanding Stomach Ulcers
A stomach ulcer occurs when the protective mucus lining of the gastrointestinal tract is compromised. This allows digestive acids to erode the tissue underneath, creating a break in the lining and forming a sore. Peptic ulcers are classified as gastric ulcers (in the stomach) or duodenal ulcers (in the duodenum).
Ulcer development is primarily linked to two factors: infection with the bacterium Helicobacter pylori (H. pylori) or the long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs). Common NSAIDs that cause damage include ibuprofen and naproxen. The most recognizable symptom is a burning or gnawing pain in the upper abdomen, often worse when the stomach is empty. Other symptoms include bloating, nausea, and uncomfortable fullness after eating.
CT Scan Limitations in Ulcer Diagnosis
A CT scan uses X-rays and computer processing to create detailed images based on density differences between tissues like bone and solid organs. This makes it effective for visualizing solid structures but less effective for detecting subtle changes in the soft, thin mucosal lining of the stomach. An uncomplicated ulcer is a superficial mucosal lesion, essentially a small crater on the interior surface of the organ.
It is difficult for the CT scanner to distinguish this small crater from the normal, undulating folds of the stomach wall. The mucosal detail required to identify a shallow ulcer is not adequately captured by the CT imaging process. While deep ulcers may sometimes appear as a focal outpouching, smaller, non-penetrating ulcers are frequently missed. Studies show that ulcers visible on CT scans are often significantly larger, averaging around 25 millimeters, while smaller ones go undetected.
The Role of Endoscopy in Diagnosis
Due to the limitations of cross-sectional imaging, upper endoscopy, also known as esophagogastroduodenoscopy (EGD), is the standard for diagnosing peptic ulcers. This procedure involves inserting a thin, flexible tube equipped with a camera through the mouth, down into the esophagus, stomach, and duodenum. The camera provides a direct, magnified, and high-definition visual inspection of the entire mucosal lining.
The physician can assess the precise location, size, depth, and appearance of the ulcer crater in real-time. Endoscopy also offers the advantage of performing a biopsy. Small tissue samples can be collected directly from the ulcer site to test for H. pylori bacteria. Biopsies are also necessary for gastric ulcers to rule out malignancy, as some gastric cancers can present with an ulcerated appearance.
Using CT to Identify Ulcer Complications
While a CT scan is ineffective for primary diagnosis, it is an invaluable tool when an ulcer leads to a complication requiring immediate surgical or medical intervention. In these acute scenarios, the CT scan identifies the consequence of the ulcer, not the crater itself. The scan is primarily used to assess damage caused by the ulcer’s penetration through the stomach wall.
Perforation
One scenario is a perforation, where the ulcer creates a hole through the entire wall of the stomach or duodenum. A CT scan easily detects the presence of free air, or pneumoperitoneum, which has leaked into the abdominal cavity. The presence of free fluid and surrounding inflammation, known as fat stranding, are also clear signs of this serious complication.
Active Bleeding
Active gastrointestinal bleeding, a common complication, can be identified on a contrast-enhanced CT scan. During the scan, intravenous contrast material is administered, and the radiologist looks for signs of contrast extravasation, which indicates active hemorrhage from a damaged blood vessel.
Gastric Outlet Obstruction
Finally, chronic ulceration, particularly in the duodenum, can cause scarring and swelling leading to obstruction of the stomach outlet, known as gastric outlet obstruction. The CT scan can visualize the resulting thickening and edema of the gastric wall and pylorus, confirming the cause of the patient’s persistent vomiting and inability to empty the stomach.