how to tell if your bowel is clean prior to colonoscopy


How can you tell if your colon is clean and ready for colonoscopy? Your last rectal effluent (stool after finishing your bowel prep agent) can act as a guide. Your stool should be clear, yellow, light and liquid. The presence of dark particles or thick brown or black stool means you are not ready for colonoscopy.

If your stool is not clear after taking your entire bowel prep agent, you may need additional prep agent. Therefore, contact your physician if your stool is still brown or has dark particles hours after finishing your bowel cleansing agent.


Stool ColorDescriptionReadiness
Dark, thick, particlesNOT READY
Brown, thick, particlesNOT READY
Dark orange, semi- clearNOT READY
Light orange, mostly clearALMOST READY
Yellow, light, clearREADY

Whereas previous studies suggest that patients’ assessments of bowel preparation are not reliable, a study suggests that photographic examples of rectal effluents may help predict the quality of bowel preparation.

A clear yellow rectal effluent (diluted urine) is the goal for your bowel prep color.  The yellow color is from bile stain.


When do you start to poop after taking your bowel cleansing agent?

Poop usually starts within 2-3 hours after taking your bowel cleansing agents. It can take longer in some people. No two persons are the same. Diseases, medications and differences in bodily functions affect bowel preparation. Therefore, it takes different times for different individuals to achieve a clear yellow rectal effluent.

People that are likely to have an inadequate bowel prep during colonoscopy have been identified in multiple studies.


Different poop stages during bowel preparation for colonoscopy

  1. Solid stool: This may be the first poop you have after taking the bowel cleansing agent.
  2. Semi-solid stool: This may be the first poop in some patients.
  3. Watery stool: This is very common in the early phase of purging the bowel.
  4. Liquid with small amount of feces: This is the mid-phase of bowel cleansing.
  5. Yellow liquid with particulate materials: This is the late phase of bowel cleansing.
  6. Turbid yellow liquid without particulates: This means you are near ready.
  7. Clear yellow liquid: This means you are ready. If you have not finished your bowel cleansing agent, you should still finish it as instructed. Also, the intestine continues to produce fecal material so rinse out the colon with the remaining bowel cleansing agent.


How much poop before colonoscopy

  • Multiple studies show that to have an clean prep, you need 3.0-3.5 liters of rectal effluent. This means you need at least 3 liters of fluid (bowel cleansing agent and clear liquid diet) to be clear. The more the fluids you consume the better your chances of being clean.
  • How much poop you have before colonoscopy depends on many factors.

3 signs you are ready for your colonoscopy 

  1. Your stool is clear yellow liquid without dark particles.
  2. Your stool comes out like an open tap.
  3. You feel like having a bowel movement but nothing comes out.


Suggested Reading Before your Colonoscopy

  1. How to use your bowel cleansing agents for colonoscopy. 
  2. The cost of an inadequate bowel preparation for colonoscopy [Video].
  3. My colonoscopy is tomorrow. What should I expect? 
  4. How to hack your colonoscopy.