Sitz marker study

The Sitz marker study is an older technique to estimate colonic transit time. 

In constipation, it can help distinguish between slow colonic transit and a defecation disorder.

The patient ingests a number of radio-opaque markers (plastic rings containing radio-opaque material) in a meal and abdominal radiographs are obtained to monitor the clearance of the rings from the colon.

Normal colonic transit time is 20-56 hours, and most adults will clear all the markers in 4-5 days.

Laxatives (and possibly GI-active medications) should be temporarily discontinued, otherwise no special preparation is needed.

Three main techniques are used:

  • 20 or 24 markers are ingested in a single dose, and then serial daily abdominal radiographs are obtained (more common)


  • 20 or 24 markers are ingested and a single abdominal radiograph is obtained six days later


  • 10 markers are ingested every day for three days and an abdominal radiograph is obtained on days four, seven, and ten

Most define <20% of the original rings at five days as normal. For instance, if 24 rings are used, then <5 rings should be present in five days. 

If using 20 rings and daily radiographs, some use the schedule:

  • day 1: ≤16 rings
  • day 2: ≤8 rings
  • day 3: ≤4 rings
  • day 4: ≤2 rings
  • day 5: ≤1 ring
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Article information

rID: 37753
Section: Radiography
Tag: refs, colon
Synonyms or Alternate Spellings:
  • Sitzmark colon transit test
  • Sitz marker study
  • Colon motility Test
  • Sitzmark Study
  • Colon transit time study
  • Colon transit study
  • Sitz markers
  • Colonic transit study (Sitz markers)

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Cases and figures

  • In this patient, ...
    Case 1: first day
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  • A zoomed-in view ...
    Case 1: the Sitz markers (zoomed in)
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  • Case 2
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  • Case 3: normal transit study
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