Most 15-year-old patients with blood in their stools are triggered by anal fissures and possibly hemorrhoids, as follows: 1. Anal fissures: 15-year-old people with irregular diets or irregular bowel movements can suffer from constipation and dry stools. Constipation and dry stools can cause the skin of the anal canal to crack, triggering anal fissures and leading to symptoms of blood in the stool. The patient needs to pay attention to diet and ensure smooth bowel movements in the next life to prevent constipation and dry stool from re-emerging and aggravating the symptoms of anal fissure. 2. Hemorrhoids: It may be hemorrhoids, which can occur at any age, and it is possible to get hemorrhoids at the age of 15. The symptoms.