Black, Tarry Stools: A Potential Sign of Advanced Colorectal Cancer
When colorectal cancer reaches its later stages, it can lead to bleeding in the upper gastrointestinal area. This bleeding, combined with the effects of digestive enzymes and intestinal bacteria, causes the hemoglobin in the blood to gradually darken as it travels through the long passage to the rectum. Consequently, stools may appear black in color and have a sticky, tar-like consistency. In the medical field, this condition is referred to as melena.
Obstruction: When the Gastrointestinal Passage is Narrowed
When the gastrointestinal passage is narrowed due to tumor growth or strictures, it can result in a condition called obstruction. This narrowing can significantly limit bowel movements if left untreated, eventually leading to bowel obstructions. In severe cases, the rectum may visibly balloon due to the blockage. It is crucial to seek medical attention when experiencing severe constipation or a pattern of alternating diarrhea and constipation, as untreated obstructions can be potentially life-threatening.