Melanosis coli is a dark brown discoloration (pigmentation) of the lining of the colon walls. Melanosis coli is harmless, does not cause symptoms and is usually observed during routine colonoscopy.
The most common cause of melanosis coli is the chronic use of anthranoid laxatives such as Senna.
If a person stops using anthranoid laxatives, the changes associated with melanosis coli lessen over time and may disappear.