Mesenteric lymphadenitis

Ultrasound signs of mesenteric lymphadenitis

The primary tool for detecting this pathology is ultrasonography (Ultrasonography). When scanning the abdomen in such patients, multiple enlarged lymph nodes localized at the root of the mesentery are visualized.

An extremely important criterion for the benign, reactive nature of the process is the preservation of the normal structure of the node. The echogram clearly demonstrates hyperechoic fatty hilum. When using color Doppler imaging (CDI) mode, blood flow within these lymph nodes is unchanged and demonstrates a normal vascular pattern. The presence of these signs combined with the absence of other pathologies (such as an unchanged appendix and normal bowel wall thickness) allows the specialist to lean towards a diagnosis of mesenteric lymphadenitis.

Differential diagnosis: inflammatory bowel disease (IBD)

Since mesenteric lymphadenitis is a diagnosis of exclusion, ultrasound must carefully rule out more serious pathologies presenting with abdominal pain, primarily inflammatory bowel disease (IBD), such as Crohn's disease (Crohn disease) and ulcerative colitis (ulcerative colitis).

IBD arises from a dysregulated immune response to intestinal microflora in genetically predisposed individuals. In young children, these diseases are particularly severe: even in Crohn's disease, the colon is frequently involved, rectal sparing may be absent (no rectal sparing), and fistulas often develop.

Unlike isolated lymphadenitis, IBD reveals specific bowel wall alterations on ultrasound:

• Small bowel wall thickness exceeds 1.5–3 mm.
• Large bowel wall thickness exceeds 2–3 mm.
• Loss of normal wall stratification (lack of bowel stratification) and altered echogenicity are observed.
• CDI shows hyperemia of the inflamed bowel segment.
• Pronounced hyperechoic mesenteric fat is identified around the inflamed bowel.

Although enlarged lymph nodes are also found in IBD, the leading sign remains involvement of the intestinal wall itself. Ileocolonoscopy with biopsy is the gold standard for confirming IBD.

Methods of intestinal imaging in children

For unexplained abdominal pain and suspected intestinal pathology in children, a specific imaging algorithm is applied.

1. Ultrasound examination. Serves as the first-line method due to its speed, availability, and lack of ionizing radiation. However, the method has limitations: it is highly operator-dependent, its diagnostic yield drops with marked pneumatosis (bowel gas) and in obese patients, and its sensitivity in detecting abscesses and fistulas remains low.
2. Magnetic resonance imaging (MRI). The preferred method for in-depth evaluation of the small intestine without radiation exposure. MR enterography (MR enterography) requires adequate bowel distension (bowel distension) with fluid and is well tolerated by children over 6-7 years of age. If the patient cannot drink the required volume, MR enteroclysis (MR enteroclysis) is used.
3. X-ray contrast examinations (barium studies). In modern practice, they have been almost entirely superseded by US and MRI due to high radiation exposure, stress for the child, and the inability to evaluate tissues beyond the bowel lumen. Evaluation of barium transit is sometimes used when obstruction is suspected, but here too the method yields to capsule endoscopy and ultra-low-dose multislice CT.

Differential diagnosis: acute appendicitis

Another critically important pathology to rule out is acute appendicitis. In clinical practice, situations arise where pain in the right iliac fossa is not caused by the appendix.

For instance, during an ultrasound scan in an adolescent, a completely normal vermiform appendix may be visualized, while revealing a thickened terminal ileum with decreased peristalsis (the picture of terminal ileitis). On the other hand, missed acute appendicitis can lead to perforation. In this case, ultrasound reveals appendicolith (a hyperechoic structure with acoustic shadowing) and formidable complications such as subcapsular liver abscesses, which may initially require ultrasound-guided percutaneous drainage, followed by CT monitoring.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Crohn's disease and ulcerative colitis: features of the ultrasound picture of intestinal wall thickness.
• MR enterography and MR enteroclysis: procedure methodology and indications.
• Complications of perforated appendicitis: subcapsular liver abscesses on ultrasound and CT.
• Ultrasound criteria for terminal ileitis and evaluation of peristalsis.

Other Topics in "Pediatric Diagnostic Radiology"

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