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Friday, 27 July 2012

Barium follow-through

Some investigators record the orocecal transit time in an upper gastrointestial and small-bowel follow- through examination, timing the smallbowel transit time from the second cup of barium, whereas others begin the timing from when sufficient barium fills the proximal two loops of jejunum. Although barium normally enters the duodenum within 15 min of ingestion, in patients with dysmotility of the esophagus or stomach, measurement of orocecal transit time will interfere with a true measurement of small-bowel transit time. For the purist, it seems, small-bowel transit time should be measured from the moment barium enters the duodenum.
As with blood pressure measurements, “normal” comprises a range of values. Ideally, one would compare the small-bowel study in question with the patient’s previous study during a period of good health to determine whether the small-bowel transit time is normal.
Small-bowel transit time depends on many factors including density and temperature of the barium preparation and presence of chemical additives, stress, patient age, patient positioning during the study, and the use of pharmacologic agents. However, the most important factors, which inversely correlate with small-bowel transit time, are the volume of barium ingested and maintenance of a full stomach.
The diseases accounting for rapid smallbowel transit time (e.g., giardiasis, carcinoid syndrome,
graft-versus-host disease) or prolonged small-bowel transit time (e.g., hypothyroidism, scleroderma, intestinal pseudoobstruction). 

_In the largest radiologic study of small-bowel transit time that comprised 315 normal small-bowel
examinations, a mean small-bowel transit time of 84 min (range, 15 min to 5 hr) was found. In 83% (261/315) of these examinations, the small-bowel transit time was less than or equal to 2 hr, whereas 97% (304/315) reached the terminal ileum within 3 hr. Small-bowel transit time was less than 30 min in only 5% (17/315). In two other radiologic studies, comprising 87 patients, small-bowel transit time ranged from 33 to 167 min, and from 15 to 105 min.

Most patients have a small-bowel transit time of between 30 min and 3 hr. The minority of cases, in which the small-bowel transit time lies outside of this range, should not absolutely be diagnosed as abnormal without correlation with associated radiographic and clinical findings.



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