PMC8008195_01
A.
Ultrasound of the abdomen in the axial plane showing a lesion (solid arrow) in the umbilical region with multiple concentric hyperechoic and hypoechoic rings - target sign or doughnut sign appearance (B, C). On tracing the lesion further, eccentric hyperechoic mesentery (solid arrow) appears
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fig1
USG was performed after obtaining written informed consent, by using both 6-10 MHz linear probe and 4-6 MHz curvilinear probe, by a single radiologist with four years of experience. USG findings revealed a lesion in the umbilical region with a target sign appearance, showing multiple concentric rings representing the multiple layers of the bowel wall (Fig. 1A). On tracing this lesion further, an eccentrically located hyperechoic focus was noted, representing the mesentery, with a hypoechoic outer ring producing the crescent-in-doughnut sign (Fig. 1B, Fig. 1C).
Diameter of the lesion - 28 mm (long solid arrow), outer wall diameter - 5.5 mm (dashed arrow) and mesenteric fat core - 4.6 mm (short solid arrow). The fat core-to-outer wall index is 0.84
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fig2
The measurement technique is demonstrated in Fig. 2.
Ultrasound image in the longitudinal plane showing the pseudokidney appearance of the lesion with the hyperechoic mesentery (solid arrow) located eccentrically to the central limb (dashed arrow) of the intussusceptum
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fig3
On the longitudinal view, the mesentery was noted on one side of the central limb of the intussusceptum, giving a pseudokidney appearance to the lesion (Fig. 3).
Colour Doppler ultrasound image in the axial plane showing intact vascularity in the bowel wall within the intussusception
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fig4
No trapped peritoneal fluid or loss of bowel wall vascularity was noted (Fig. 4), which if present would have been suggestive of bowel wall necrosis.