Fecal Pellet Output

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A simple and noninvasive means of evaluating gastrointestinal function involves measuring fecal pellet output over a given time period(s).  This can involve not only pellet counts but also measuring total wet weight, total dry weight and descriptive observations.  In turn these measures can be used to calculate average weight / pellet and wet versus dry ratio which provides a measure of moisture content while also serving as a colonic transit test.

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The study illustrated below shows how the inhibition of colonic motility by morphine results in reduced fecal pellet output

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Blood glucose changes of mice responding to an exogenous insulin challenge.

Fecal pellet output as a colonic transit test. C57Bl/6 mice were fed ad libitum until the acclimation period at approximately 9:00 AM. Then mice were weighed, dosed with vehicle or 10 mg/kg morphine SC, singly housed in polyurethane cages without access to food, and acclimated to the procedure room for 30 minutes prior to the study, with free access to water. With a study start at approximately 9:30 AM, at each subsequent hour after administration up to 4 hours, the number of fecal pellets (A) and weights (B) was recorded.  Data are mean ± SEM and evaluated using unpaired t-test (N=10).  *p<0.05, **p<0.01, ***p<0.001.

Frequently Asked Questions

How is the fecal pellet output quantified (e.g., number, weight, water content, consistency), and what is the collection period and frequency?

The primary endpoints for the fecal pellet output assay are the total number of pellets expelled and their total weight (wet weight). We typically collect pellets during a defined post-dosing period, most commonly a 2- to 4-hour window. Collection can be performed continuously and totaled at the end, or in shorter, sequential time bins (e.g., every 60 minutes) to assess time-course. If requested, we can incorporate secondary measurements such as dry weight or consistency scoring.

What is the typical duration of a study using this endpoint, and what positive control compound is routinely used to demonstrate efficacy in your system?

The duration of the treatment phase is flexible but is often a single acute dose for a pilot or proof-of-concept study. For chronic effects, we recommend a study of 3 to 7 days of repeat dosing, following a 3-5 day acclimatization period. The choice of positive control depends on the desired effect: we commonly use Loperamide to induce an anti-motility/constipating effect, or a prokinetic agent like Prucalopride if a laxative/pro-motility effect is being tested.

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Interested in running a Fecal Pellet Output study?

If you are interested in learning more about evaluating gastrointestinal function using a colonic transit test such as measuring fecal pellet output, please contact us to start the conversation today!

Discuss your project with us