Brief Answer:
Can be suggestive of a mild tear or perforation.

Detailed Answer:
Hello,
Thank you for choosing HealthcareMagic for your query.
I am a Gastroenterologist and would be answering your query.
I've gone through your question in detail and I appreciate your concerns.

As per your query answers are-

Colonoscopy is a very safe procedure with complications occurring in less than 1% of patients. The procedure is done using a long colonoscope. The tube has a light and tiny camera on one end. It is put in your rectum and moved into your colon.The movement of this long tube might cause mild erosion of the lining of rectal or anal canal causing a mild bleed or blood streaks on the stool.

However, 3 weeks is more than enough time for small mucosal breeches to heal themselves up.

In the same way, colonoscopy preparation involves thorough gastric lavage with an electrolyte solution which irritates the mucosa causing increased secretions of mucous however again it has already been 3 weeks.

So to be on a serious note this mild bleeding with yellow mucous could be suggestive of a small tear in the intestine (perforation). Sometimes during the procedure, a small hole is punched through the intestinal wall.Small perforations most intuitively result from direct mechanical trauma, such as the result of the forceful passage of the tip of the endoscope through a diverticulum (misidentified as a lumen). This is rare but is possible.

Perforation has been estimated to occur in approximately 0.2% of diagnostic colonoscopies and 0.6% of colonoscopies where biopsy is also performed.

A small hole in the intestine could explain both yellow color of mucous(incompletely formed stool ) and layers of blood on stool.

Though this is rare, yet rare things do occur.
To be on a safer side a CT scan abdomen should be done. If it's normal then there is no need to worry.

Suggestion-
Go for a CT abdomen.
ALCA antibody has nothing to do with it.

Please follow up with reports.

I wish you an early recovery.
Thanks.

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