Brief Answer:
You might need some tests done to see if blood is present in your stools (FOB test) and if, so which is the cause (colonoscopy).

Detailed Answer:

Hello,

Irritable bowel syndrome can cause ongoing problems with diarrhea and / or constipation and fibers (Metamucil in you case) is a choice for many doctors and is well recommended in the treatment of IBS.

It is unlikely though that you would get brown diarrhea with either IBS or Metamucil meaning that the brown color in your stools seems to not be caused by IBS and not by Metamucil.
The concern you have of a blockage or other conditions in the bowel is understanding and is important to have tests to find out if this is the case or not.

First of all, it is important to clarify if the brown color is related to presence of blood with stools or not. In this case, stool occult blood test is the one recommended and you need 3 negative tests done in 3 different days to increase the chance that no blood is present in stools. If the test comes out positive in even 1 case out of 3 than it means you have blood in stools and further investigation is needed to be done as soon as possible to find out why you have blood in stools.

Another test that would help a lot find out the cause of your symptoms is the test called colonoscopy. This is a test you do with a camera entering the rectal area and that explores the bowel for tumors, ulcers or other conditions that need to be ruled out as the cause of your symptoms. It also allows material to be taken to be seen in microscope if a lesion is identified and increases the chances of diagnosis.

To conclude I would say:
1. first of all check your stools for occult blood (Fecal Occult Blood test), you need 3 negative results to be sure at least 90% you do not have blood with stools. This is the first test as it is generally easy, noninvasive and straightaway test. Negative results do not mean you do not need the next test (colonoscopy)

2. if you have not have colonoscopy in the last 2 years you might need to have it done. Literature recommends it in each patient 50 years or above as a screening test, meaning even if the patient has no symptoms. If the FOB test comes negative in 3 occasions and you had a normal colonoscopy in the last 2 years than it might still be ok to not do it but it is your doctor that has to decide this after examining you.

3. as mentioned above you need a visit with your doctor to discuss all these and also have a detailed examination to make sure which is the cause of your symptoms and get the proper help.

I hope this is helpful and answers to your questions but please feel free to contact me in case anymore clarification is needed on this.

Regards,
Dr. Zotaj Antoneta
General & Family Physician

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