Spastic colon, also known as irritable bowel syndrome, is a bowel disorder that causes bouts of frequent diarrhea, constipation or both. Spastic colon causes increased spontaneous contractions of the small and large intestines, causing diarrhea.

Spastic colon, now known as irritable bowel syndrome, affects 58 million Americans and represents one of the most common complaints encountered by doctors, according to the Washington University School of Medicine Section of Colon-Rectal Surgery. Pain is considered one of the cardinal symptoms of spastic colon.