Although the sight of green stools may be alarming, they do not usually indicate a serious intestinal problem, explains Dr. Michael Picco of the Mayo Clinic. Most cases of green stools in kids are temporary. Long-lasting changes that are not obviously due to diet or medications require medical evaluation to rule out potentially serious causes.
Stool color is heavily influenced by diet. A high intake of green vegetables, such as broccoli or cabbage, can cause green stools, as can foods artificially colored with green dye, including some ice creams, fruit juices, sodas and breakfast cereals. Oddly, purple and blue food coloring may also cause green stools in children. Limiting intake of green foods and artificial dyes for a few days can determine if dietary causes are responsible for your child's green stools.
Medications and Supplements
Iron supplements are a common cause of green stools, and artificially colored vitamin supplements, as well as those that contain sorbitol or fructose may also cause a temporary change in stool color. Laxatives may cause green stools due to their speeding up of bowel activity. MayoClinic.com notes that indomethacin, a non-steroidal anti-inflammatory medication, and antibiotic-induced diarrhea are other possible causes of green stool color in kids.
Excess Mucus and Bile
Digestive problems that cause bile to pass more quickly through the intestines trigger green stools because the bile does not have time to transition from green to yellow to brown. Some disorders that may cause shortened bowel transit time include gastroesophageal reflux disease, thyrotoxicosis associated with hyperthyroidism, diarrhea due to food poisoning, infection, allergies, malabsorption, celiac disease, ulcerative colitis and Crohn's disease. Impaired re-absorption of bile due to intestinal inflammation or removal of the terminal ileum, and any disorder that increases the amount of mucus in the stool can also cause greenish bowel movements.