Etiology and pathogenesis
With the development of modern treatments for peptic ulcer disease (Peptic Ulcer Disease, PUD), the structural causes of obstruction have changed dramatically. While scarring from ulcers used to be the leading factor, malignant neoplasms have now come to the forefront.
When peptic ulcer disease is the cause, lesions are usually localized in the duodenum, pyloric channel, or distal antrum. Obstruction in these cases develops through several pathophysiological mechanisms:
- Pronounced muscle spasm.
- Formation of dense scar tissue.
- Edema associated with acute inflammation.
- Hypertrophy of the muscular layer.
Less common factors capable of causing impaired patency include pancreatitis, pancreatic cancer, Crohn's disease, as well as granulomatous and infectious processes (sarcoidosis, tuberculosis, syphilis).
Imaging diagnostics of obstruction
To confirm the diagnosis and determine the cause of obstruction, an arsenal of imaging methods is used, each of which has its own limitations and advantages.
- Abdominal X-ray: Allows visualization of the classic picture — a sharply dilated, air-filled stomach. At the same time, the transverse colon is displaced inferiorly due to the mass effect.
- Barium swallow fluoroscopy: In modern practice, this method has lost its former popularity because it does not allow for high-precision determination of the true borders and extent of the obstruction.
- Computed tomography (CT): This is the top imaging modality. CT outperforms all other modalities in visualizing mass lesions and structural anomalies of the gastric wall, which is especially critical when an oncological process is suspected.
Differential diagnosis sometimes requires the exclusion of other submucosal changes. For example, in gastric varices, the radiograph shows nodular serpiginous filling defects in the fundus, while contrast-enhanced CT in the venous phase clearly demonstrates the expanded vascular network.
Non-obstructive dilatation and gastroparesis
The stomach can dilate not only due to a mechanical obstruction, but also against the background of functional disorders.
- Acute dilatation: Occurs suddenly in the form of gastric ileus (paresis). This is a typical complication after abdominal surgery or severe trauma.
- Chronic dilatation: Associated with hypomotility, a classic example of which is gastroparesis.
Gastroparesis is a persistent motility disorder in which gastric emptying is delayed, but there is no physical barrier in the outlet. Patients complain of early satiety, nausea, vomiting, bloating, and pain. Most often the cause remains unknown (idiopathic form), but the condition can also develop due to metabolic disorders (diabetes), infiltrative processes, neuropathies, and certain medications. The role of imaging methods here is twofold: CT or endoscopy is needed to rule out a tumor or scar, and scintigraphy is needed to objectively prove food retention.
Gastric emptying scintigraphy
This is the gold standard for assessing motor function. To ensure reliable results, medications affecting peristalsis are discontinued 48 hours before the procedure. In patients with diabetes mellitus, it is important to correct glycemia — the test is performed only when blood glucose is below 275 mg/dL.
A standard radioactive meal is used for the study: 1 mCi of Tc-99m (sulfur colloid) is mixed with 4 ounces of egg white, served with bread, jam, and water (for egg allergies, oatmeal is substituted). Evaluating liquids alone is impractical, as they can empty normally even with severe paresis.
Evaluation of results: The liquid fraction leaves the stomach monoexponentially. Solid food first undergoes a lag phase (5–20 minutes) during which it is triturated and fermented (no significant emptying occurs during this period), after which it empties linearly.
| Severity | 4-hour retention percentage |
|---|---|
| Normal | Less than 10% (emptying >90%) |
| Mild | 10–15% |
| Moderate | 15–35% |
| Severe | Greater than 35% |
Note: The 4-hour mark is the most sensitive. An alternative criterion for gastroparesis is greater than 60% retention at 2 hours. It is important to remember that the severity of subjective symptoms does not always correlate with the actual retention figures on scintigraphy. Conversely, if less than 30% of the food remains in the stomach after 1 hour, hypermotility is diagnosed.
Briefly: answers to topical questions
What causes the development of gastroparesis?
The development of gastroparesis is idiopathic in most cases. Known causes of this motility disorder include:
- Metabolic diseases — including diabetes mellitus (diabetic gastroparesis).
- Neuropathies — particularly autonomic neuropathy.
- Infiltrative diseases — systemic tissue disorders.
- Medication intake — drug-induced delayed emptying.
Which specific groups of medications must be stopped before gastric emptying scintigraphy?
Before scintigraphy, any medications affecting gastric motility must be discontinued. Specific pharmacological groups are not listed in the sources. Only a strict rule is indicated: such medications must be stopped at least 48 hours before the start of the study to objectively confirm stasis.
What ultrasound signs are characteristic of congenital hypertrophic pyloric stenosis in children?
The main ultrasound sign of hypertrophic pyloric stenosis is an increase in the transverse thickness of the pyloric muscle.
- Transverse thickness of the pyloric muscle — the most reliable criterion, which exceeds 3 mm in true disease.
This parameter is considered diagnostically significant regardless of the patient's age and weight. If measurement results are questionable, a repeat ultrasound is recommended.
To classify gastroparesis, remember the numbers at the 4-hour mark: 10-15-35. Up to 10% — normal. 10–15% — mild delay. 15–35% — moderate. Above 35% — severe.
Class and exam questions
Can gastric scintigraphy be performed in decompensated diabetes?
No. Hyperglycemia must be corrected before the test, as high blood sugar itself inhibits motility. The study is permitted only when blood glucose is <275 mg/dL.
Is it mandatory to assess liquid evacuation when gastroparesis is suspected?
Usually this is not required. The stomach can empty liquids normally in a monoexponential pattern even when solid food retention is already severely pronounced.
What is the «lag phase» in solid-meal scintigraphy?
This is the initial period lasting from 5 to 20 minutes when food undergoes mechanical grinding and chemical digestion. During this time, no significant gastric emptying occurs.
What else to study on this topic
- CT signs of malignant tumors of the distal stomach
- Differential diagnosis of acute paresis (gastric ileus) and mechanical obstruction
- Imaging features of gastric fundus varices in the venous phase
- The role of prokinetics and drug-induced causes in the development of chronic gastroparesis
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