Ascaris lumbricoides is a common nematode infesting a major percentage of human beings worldwide. It grows to a maximum length of 35 cm. This species is host specific to human beings and lives longer (1-2 years) with in the small intestine.
However, as the bowel loops are just under the abdominal wall, the detection of intestinal ascariasis is difficult by routine abdominal probes. It demands the use of a higher frequency high-density probe of 5 - 10 MHz. The live worm on longitudinal section appears as a writhing tubular shadow having brighter margins described by some as 'strip sign'. There is a hypoechoic core producing the 'inner tube sign'. The coiled worm appears as 'spaghetti'. The cross-sectional picture is also characteristic of a tubular body described as the ring sign or bull's eye sign if seen with in the CBD or a narrow lumen.
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K BALAKUMAR
Ind J Radiol Imag 2005 15:1:107-108
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