Feline colon to L5 ratio calculator
Enter the maximum colon diameter and L5 length in mm, then copy the summary.
For educational purposes only. This is not veterinary advice and does not replace clinical judgment. Check every result against the source guideline.
Lateral view, serosa to serosa at the widest point between the ileocolic junction and the pelvic inlet.
Length along the spine, not height.
Enter both measurements to see the ratio.
The calculator runs in your browser, and the numbers you enter are never sent anywhere.
Where the bands come from
Trevail and colleagues measured 50 normal, 13 constipated and 26 megacolon cats. Their bands are under 1.28 for a normal colon diameter, 1.28 to 1.48 for constipation and over 1.48 for megacolon. The calculator counts 1.28 and 1.48 as constipation.
Common questions
- How do you measure the colon to L5 ratio in a cat?
- On a lateral abdominal radiograph, measure the colon from serosa to serosa at its widest point between the ileocolic junction and the pelvic inlet, at right angles to the colon. Divide by the length of the L5 vertebral body.
- What ratio suggests megacolon?
- Trevail and colleagues found that a ratio over 1.48 suggests megacolon, 1.28 to 1.48 suggests constipation, and under 1.28 suggests a normal colon diameter. At 1.28, the ratio separated normal from distended colons with a sensitivity of 96.2 percent and a specificity of 87.3 percent.
- Why L5 length and not height?
- The study divided by L5 length. Using height gives a larger ratio and puts cats in the wrong band.
- Does a high ratio mean the colon will not recover?
- No. One measurement does not show whether colonic dysfunction is reversible. The study came from a referral population with 13 constipated and 26 megacolon cats, so read the ratio with the history and examination.
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