Finding blood in a child’s stool can be unsettling for any parent, raising concerns about their child’s health. This symptom, broadly defined as rectal bleeding, is medically categorized based on its appearance. Hematochezia refers to bright red blood, while melena describes dark, tarry stools that indicate digested blood. While prompt medical attention is required, the majority of cases are caused by conditions that are not life-threatening and are relatively simple to manage.
Decoding the Appearance of Blood
The visual characteristics of the blood are important clues for a doctor to determine the source of the bleeding within the gastrointestinal (GI) tract. Bright red blood (hematochezia) typically suggests a bleed in the lower GI tract, meaning the rectum or anus. This color indicates the blood has not been significantly altered by digestive enzymes or stomach acid.
Conversely, black, sticky, and foul-smelling stools (melena) are a sign of digested blood, suggesting a source in the upper GI tract, such as the stomach or esophagus. The digestive process converts the red hemoglobin into hematin, which gives the stool its characteristic tarry appearance. Stools that appear dark red or maroon usually indicate bleeding from the small intestine or the upper part of the colon.
Common Causes of Bright Red Blood
The most frequent reason a parent notices bright red blood is an anal fissure, a small tear in the lining of the anus. These tiny cuts are overwhelmingly caused by the passage of a hard or large stool, a common occurrence when a child is constipated. The blood from a fissure is typically seen as a small streak on the outside of the stool or on the toilet paper after wiping. Severe constipation often leads to straining, which can cause the fissure or, less commonly in young children, result in minor hemorrhoids that bleed.
Infectious diarrhea, often caused by certain viruses or bacteria, can irritate the colon lining enough to cause mild bleeding. This irritation is termed colitis and results in bloody diarrhea, though the amount of blood may be small and mixed with the loose stool. In infants, a common cause of bright blood and mucus in the stool is allergic colitis, often triggered by a cow’s milk protein allergy. The immune system reacts to the protein, causing inflammation in the colon lining. Removing the dietary irritant, such as cow’s milk from formula or the mother’s diet, usually resolves the bleeding.
Serious Conditions Requiring Diagnosis
Some causes of blood in the stool are less common but represent serious medical concerns that require definitive diagnosis and intervention. Intussusception is a condition where one segment of the intestine telescopes into the adjacent section, causing an obstruction and potentially cutting off the blood supply. This condition most commonly occurs in infants and toddlers and can present with severe, intermittent abdominal pain, vomiting, and a classic “currant jelly” stool—a mix of dark blood and mucus.
Another possibility is Meckel’s diverticulum, a congenital pouch on the wall of the small intestine. This outpouching can contain ectopic gastric tissue, which secretes acid and causes ulcers in the adjacent intestinal lining. The resulting bleed is often painless and can manifest as bright red blood or dark, maroon-colored stools. Chronic bloody diarrhea, especially in older children, may be a symptom of Inflammatory Bowel Disease (IBD), which includes conditions like Crohn’s disease and Ulcerative Colitis.
IBD involves chronic inflammation and ulceration of the GI tract, leading to persistent symptoms like abdominal pain, weight loss, and blood mixed in the stool. Severe bacterial infections, such as those caused by E. coli O157:H7 or Salmonella, can cause an acute, severe colitis. These infections often result in profuse, bloody diarrhea, accompanied by high fever and significant abdominal cramping.
Urgent Symptoms Requiring Immediate Care
While many causes of blood in the stool are benign, certain associated symptoms indicate a medical emergency and require immediate care. A child who passes a large volume of blood needs urgent attention due to the risk of significant blood loss. Signs suggesting shock, such as lethargy, pale or clammy skin, a rapid heart rate, or dizziness, signal a life-threatening situation. Severe, persistent abdominal pain or cramping, especially coupled with bloody diarrhea, is a red flag for serious conditions like intussusception or severe infection. A high fever, persistent vomiting, or signs of severe dehydration—including sunken eyes or a lack of urination—accompanying the bloody stool also warrant immediate medical evaluation. If a child appears very sick or is inconsolably irritable, seek help immediately.