One possible cause of severe constipation and sticky stool is irritable bowel syndrome or IBS. Individuals suffer different symptoms with IBS, but severe constipation and passing mucus in the stool often affect sufferers. Other causes include negative-side effects of medications, such as oral antihistamine-decongestant combinations, according to Mayo Clinic. Individuals suffering from chronic constipation often require a medical consultation for a proper diagnosis.
Irritable bowel syndrome affects 20 percent of the population, but it is undiagnosed in more than half the sufferers, according to the National Digestive Diseases Information Clearinghouse. While some individuals experience severe constipation, others suffer with severe diarrhea. Still others have alternating constipation and diarrhea. The condition sometimes causes weight loss and anemia. Doctors use tests such as stool samples, lower-gastrointestinal series of exams and a colonoscopy to further diagnose the condition.
WebMD reports an update to the care guidelines for IBS and chronic constipation, as published in the August 2014 American Journal of Gastroenterology. The new guidelines support dietary changes, the use of probiotics to increase good bacteria and new medicines that work in the digestive tract.
Mayo Clinic reports a side effect of the oral medication promethazine as causing black, sticky stools. When prescribed a new medication, doctors must discuss possible side effects with their patients. Over-the-counter medications also have the potential to affect the gastrointestinal tract.