What is a Sitz Marker Test?
Also known as a radiopaque marker (ROM) study, the Sitz marker test is a non-invasive diagnostic procedure used to evaluate colonic transit time, or how quickly food moves through the colon. It is a valuable tool for physicians when investigating the cause of chronic constipation, particularly to determine if the issue is a motility disorder (like slow-transit constipation) or an obstruction.
During the test, a patient swallows a capsule containing small, harmless rings made of a radiopaque material. These markers are visible on an X-ray. A standard capsule, such as SITZMARKS®, contains 24 rings. The capsule dissolves, releasing the markers into the digestive tract, and an abdominal X-ray is typically taken five days later to track their progress.
Interpreting Your Day 5 X-ray Results
After five days, a healthcare provider will take a single abdominal X-ray, also known as a KUB, to determine the number and location of any remaining markers. The interpretation is based on a simple count and observation of their distribution within the colon. The results help to categorize the patient's colonic transit as either normal or abnormal, with abnormal results further classified by marker location.
Normal Colonic Transit
For a patient with a standard 24-marker capsule, the benchmark for normal transit is the expulsion of at least 80% of the markers by the fifth day. This translates to a finding of five or fewer markers remaining on the Day 5 X-ray. The remaining markers may be scattered, but a low count indicates that the colon is functioning within the normal range.
Abnormal Colonic Transit: What to Look For
If a patient retains six or more markers after five days, the colonic transit is considered abnormal. The pattern of the remaining markers is crucial for further diagnosis, as it can help distinguish between different types of constipation.
- Colonic Inertia (Slow Transit Constipation): If the retained markers are scattered diffusely throughout the colon, it suggests that the colon's muscles are not effectively moving waste along. This condition, also known as colonic hypomotility, means the entire large intestine is moving slowly.
- Functional Outlet Obstruction: When the markers accumulate predominantly in the rectum or rectosigmoid area, it indicates an issue with the final stage of elimination. This suggests a functional or structural problem, such as anismus or internal rectal prolapse, rather than a whole-colon motility problem.
Comparison of Sitz Marker Results
This table outlines the key differences in findings based on the distribution and quantity of retained markers.
| Result | Markers Retained (from 24) | Distribution on X-ray | Indicated Condition | Key Insight |
|---|---|---|---|---|
| Normal | 5 or fewer | Markers mostly absent or scattered minimally. | Grossly normal colonic transit | Bowel movement is efficient. |
| Abnormal (Scattered) | 6 or more | Evenly scattered throughout the colon. | Slow-transit constipation (colonic inertia) | Generalized slow movement of the entire colon. |
| Abnormal (Clustered) | 6 or more | Accumulated in the rectosigmoid region. | Functional outlet obstruction | Difficulty with elimination from the rectum. |
The Role of the Healthcare Provider
While the Sitz marker test provides objective data, it is not the sole determinant of a diagnosis. It is a complementary tool that helps a physician correlate a patient's symptoms with physiological evidence. Studies have shown that the number of markers retained does not correlate with the severity of a patient's symptoms or their quality of life, so clinicians must be careful not to over-interpret the test results. The ultimate diagnosis and treatment plan must be determined in consultation with a medical professional who considers the full clinical picture.
It is also important to note that certain dietary changes or medications can influence the test's outcome. Patients are typically instructed to avoid laxatives, enemas, and suppositories during the test period to ensure accurate results. For more information on the diagnostic process, you can visit the official SITZMARKS® website.
Conclusion
For most individuals, a day 5 Sitz marker test showing five or fewer retained rings points toward normal colonic function. The presence of six or more markers, however, is considered abnormal and warrants further investigation into the specific type of constipation. The pattern of marker distribution—whether scattered throughout the colon or clustered near the rectum—provides critical information that helps a physician pinpoint the underlying issue. The Sitz marker test is a simple yet powerful diagnostic tool that, when properly interpreted alongside a patient's full medical history, guides an effective and targeted treatment strategy for chronic constipation.
