A number of approaches have been used in the past to assess gut transit. These methods include radiologic techniques (bismuth subnitrate, barium sulfate) as well as the use of insoluble colored powders (e.g., carmine or charcoal) or markers that can be chemically measured (chromium sesquioxide, copper thiocyanate, or sodium chromate).1-7
In 1924, investigators at the Mayo Clinic used colored glass beads to study transit times.8 This method, however, required liquefaction of stools for recovery of markers by sieving.
Clearly, none of these techniques meets current guidelines on acceptable radiation exposure for healthy subjects or patients. Most are also inconvenient due to the laborious stool analytical procedures involved. Nevertheless, these approaches provide interesting landmarks in this field and illustrate the concept that assessment of gut transit has been deemed an important goal for the clinician.
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