Duodenal string test - Tips from Other Journals

Date: Dec, 1990

The duodenal string test is an inexpensive, minimally traumatic and effective method for sampling the contents of the upper gastrointestinal tract. Because this test is less traumatic than alternative procedures, it is well suited for the pediatric population. In a review article, Korman describes the string test and its uses as an outpatient diagnostic aid.

The device for the string test consists of a dissolvable gelatin capsule that contains a nylon string (which protrudes from the capsule) and silicone weight. The capsules are available in adult and pediatric sizes. After a four-hour (or overnight) fast, the patient swallows the capsule, with the protruding string attached firmly to the patient's cheek by a piece of adhesive tape. Additional reinforcing tape should be used for small children to prevent removal of the string. The capsule's transit through the pylorus may be aided by the patient drinking water frequently for the first one or two hours. After the string has been in place for a minimum of three to four hours, the string is then pulled out.

An assistant is needed when the string test is performed in an infant or a child too young to swallow the capsule. The assistant holds the child, with the child's neck extended over the assistant's shoulder. With the aid of a padded spatula to prevent the child from biting, the capsule is positioned in the posterior pharynx, initiating a gag followed by a swallow. Alternatively, a syringe is used to place 2 to 5 mL of water in the mouth, which usually initiates swallowing.

The most widely accepted indication for the string test is for confirmation of suspected giardiasis. The string test has also been used in the diagnosis of other enteric parasitic infections, including ascariasis, strongyloidiasis and hookworm infection. The string test may also be used to diagnose bacterial or fungal overgrowth in the small intestine, to isolate Salmonella typhi or Salmonella paratyphi, to differentiate between intrahepatic cholestatic disease and extrahepatic biliary atresia, to screen for gastroesophageal reflux and to localize the site of upper gastrointestinal hemorrhage. (American Journal of Diseases of Children, July 1990, vol. 144, p. 803.)

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