Ultrasound examination in bowel pathologies
Ultrasound diagnostics is actively used for the initial assessment of gastrointestinal tract changes and mesenteric lymph nodes.
- Mesenteric lymphadenitis: In grayscale (B-mode), multiple lymph nodes are visualized with preserved echogenic fatty hilum. Color Doppler mapping shows a normal vascular pattern within them.
- Terminal ileitis: Characterized by marked wall thickening of the terminal ileum, increased echogenicity, and decreased peristalsis. Doppler ultrasound shows pronounced hyperemia of the inflamed wall segment.
The role of magnetic resonance imaging in IBD assessment
Magnetic resonance imaging has high diagnostic value in Crohn's disease and requires special preparation, including a 3-day diet and fasting for 24 hours prior to the procedure.
- MR enteroclysis helps determine the exact localization, extent of the process, as well as intraluminal and extraluminal disorders.
- Specialized protocols include pelvic MR fistulography to search for perianal fistulas and abscesses, as well as dynamic MRI to identify strictures.
- Diffusion-weighted imaging (DWI) demonstrates high sensitivity and specificity, allowing for reliable detection of lesions often without the use of contrast agents.
MRI signs and complications of inflammatory processes
When evaluating the MRI picture of inflammatory bowel diseases, specialists analyze the morphological features of bowel loops and the structure of the organ wall.
- Appearance of bowel loops: Loops can be fixed, dilated, and show signs of pseudosacculations and strictures.
- Wall changes: Thickening, ulcerations, intramural abscesses, restricted diffusion, and various contrast enhancement patterns are noted.
- Extramural manifestations: These include fibro-fatty proliferation, dilated mesenteric vessels, fistulas, and enlarged lymph nodes.
Features of computed tomography
CT enteroclysis and CT enterography methods are widely used in adult patients for detailed visualization of the small intestine.
- Due to high radiation exposure, the use of CT in children is strictly limited, and the technique is avoided whenever possible.
- In pediatric and routine practice, computed tomography retains the status of a reserve method and is prescribed primarily for assessing acute conditions.
Briefly: answers to topical questions
What contrast enhancement patterns in the bowel wall are distinguished on MRI in Crohn's disease?
Magnetic resonance imaging identifies several specific patterns of contrast enhancement in the bowel wall. These include:
- Mucosal only — isolated enhancement of the inner lining.
- Layered (layered) — contrast enhancement in a layered pattern, which is a sign of active inflammatory disease.
- Global (global) — uniform contrast accumulation throughout the entire thickness of the bowel wall.
- Serosal hypervascularization — accumulation of the agent in the outer layer of the bowel.
How does the technique of CT enteroclysis differ from CT enterography?
The main difference of CT enteroclysis lies in the method of enteral contrast administration: in CT enteroclysis, the contrast is administered directly into the small intestine through a nasojejunal tube.
| Characteristic | CT enteroclysis (CT enteroclysis) | CT enterography |
|---|---|---|
| Contrast administration | Via an 8–10 Fr nasojejunal tube directly into the small intestine | Indicated in the source as the comparative method |
| Contrast volume | 1.5–2 L of enteral contrast | Not specified |
| Pump administration | Initial rate 100–150 ml/s, then 150–200 ml/s after the first 0.5–1 L | Not specified |
| Tolerability | Worse tolerated compared to CT enterography | Most studies show that patients tolerate CT enterography significantly better |
The diagnostic accuracy of CT enteroclysis and CT enterography does not significantly differ.
What classic radiological symptoms of Crohn's disease are detected during barium follow-through radiography?
Barium follow-through radiography reveals specific changes in the mucosal relief of the stomach and duodenum. Classic symptoms include:
- Aphthous erosions — multiple superficial defects located predominantly in the antrum of the stomach.
- Cobblestone appearance (cobblestone mucosa) — nodular structure and marked thickening of the duodenal folds.
What ultrasound criteria are used for differential diagnosis between Crohn's disease and ulcerative colitis?
Differential diagnosis can be based on the assessment of bowel wall thickness and signs of extraintestinal manifestations.
| Criterion | Crohn's disease (Crohn disease) | Ulcerative colitis (Ulcerative colitis) |
|---|---|---|
| Bowel wall thickness | Pronounced thickening, average 11 ± 5.1 mm; generally greater than in UC | Usually 5–8 mm, average 7.8 ± 1.9 mm |
| Extraintestinal manifestations | Phlegmon, abscess, and fistula formation indicate Crohn's disease | For UC, the source states that small bowel involvement is limited to backwash ileitis |
| Small bowel involvement | May be detected in Crohn's disease | In UC, it is limited to reflux ileitis (reflux ileitis) |
MRI requires preparation (24-hour fasting), DWI replaces contrast in IBD, and CT is contraindicated in children due to radiation.
Class and exam questions
What type of blood flow is characteristic of unchanged mesenteric lymph nodes on ultrasound?
Color Doppler mapping shows normal blood flow in the lymph node hilum.
Why are diffusion-weighted images (DWI) particularly valuable in bowel MRI?
DWI increases the sensitivity and specificity of detecting lesions in IBD and is often so sensitive that intravenous contrast administration becomes unnecessary.
What are the main limitations of computed tomography in children?
CT enteroclysis and CT enterography in children should be avoided due to the high dose of ionizing radiation, so CT is used as a backup method.
What else to study on this topic
- Patient preparation for bowel MRI
- Differential diagnosis of bowel strictures
- MR fistulography in perianal complications
- Features of MR hydrographic cine images
- Diagnostic imaging of pediatric intussusception
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