GI transit time and segment timing
GI transit time describes how long food or intestinal contents spend moving through the stomach, small intestine, and colon. A GI transit time model estimates total transit duration, segment-by-segment timing, and possible arrival times when a start time is provided. This helps connect motility with digestion, absorption opportunity, water recovery, and stool timing.
Core formulas
Total GI transit time is the sum of the main segment durations:
\[
\begin{aligned}
T_{\text{GI}} &= t_{\text{stomach}} + t_{\text{small}} + t_{\text{colon}}
\end{aligned}
\]
Each segment can also be expressed as a percentage of the total transit time:
\[
\begin{aligned}
\%t_{\text{segment}} &= \frac{t_{\text{segment}}}{T_{\text{GI}}} \cdot 100
\end{aligned}
\]
When total-time split mode is used, the total time is distributed across segments by selected weighting factors:
\[
\begin{aligned}
t_{\text{segment}} &= T_{\text{GI}} \cdot w_{\text{segment}}
\end{aligned}
\]
Here, \(T_{\text{GI}}\) is total gastrointestinal transit time, \(t_{\text{stomach}}\) is gastric emptying time, \(t_{\text{small}}\) is small intestine transit time, \(t_{\text{colon}}\) is colon transit time, and \(w_{\text{segment}}\) is the selected weighting fraction for a segment.
How to interpret results
A shorter total transit time suggests rapid movement through the digestive tract, which may reduce contact time for digestion, absorption, and water recovery. A longer total transit time suggests delayed movement, often dominated by prolonged colon residence and slower stool timing. Typical, rapid, delayed, and strongly delayed classifications are teaching categories, not clinical diagnoses.
- Use hours consistently for all segment inputs.
- Do not enter negative transit times.
- Use total-time split mode only when the total transit duration is known.
- Remember that meal type can change gastric emptying and overall timing.
Example: if gastric emptying is 3 h, small intestine transit is 4 h, and colon transit is 36 h, then total GI transit is 43 h.
This model is useful for physiology learning, meal-type comparisons, motility scenarios, and visualizing how stomach, small intestine, and colon timing combine. It should not replace clinical evaluation, because real transit depends on hydration, fiber intake, medications, disease states, microbiome effects, and individual motility patterns.
