String sign

String sign is a medical term used in diagnosing Hypertrophic Pyloric Stenosis (HPS). Specifically, it is a radiographic finding on an Upper GI series in which the infant is given a radio-opaque material, such as barium, to drink. X-rays are then taken of the infant's stomach and intestines.

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If the infant has pyloric stenosis, the pylorus is narrowed and the barium will take on the appearance of a thin string as it passes through this narrowed channel. Often, there are several of these strings seen (called the "railroad track sign"). The use of the Upper GI series for the diagnosis of HPS, which was the primary diagnostic tool for this condition in the 1980's and 1990's, has been largely replaced by the use of ultrasound, which is less invasive and can visualize the thickened pylorus, giving actual measurements of this thickening.

String sign is also used to describe a narrowed segment in regional ileitis. Among the inflammatory bowel disease, string sign appears in Crohn disease and not Ulcerative colitis making this sign of significance.

References

"Nelson's Textbook of Pediatrics," Twelfth Edition. Richard Behrman, M.D. and Victor Vaughan, III, M.D. Editors, p. 904.