Blood in a child's stool, however small the quantity, tends to produce immediate parental alarm. In most cases in children, the cause is benign and treatable, but blood in the stool should not be dismissed without assessment because the range of possible causes includes some that are serious.
Understanding what the blood looks like (where it is, what colour it is, how much there is) gives useful information about where in the digestive tract the bleeding is coming from and helps guide how urgently assessment is needed.
Healthbooq (healthbooq.com) covers digestive health through the early years, including symptoms that warrant prompt medical review.
Reading the Blood
Bright red blood on the surface of the stool or on toilet paper, with no blood mixed through the stool itself, is consistent with bleeding from the lower end of the digestive tract: the anus or the rectum. This is the most common pattern in children and usually reflects an anal fissure (a small tear), a polyp, or inflammation of the rectal mucosa.
Blood mixed through the stool suggests bleeding higher up, in the colon or beyond. This may be darker red or maroon. Infectious gastroenteritis, particularly from Campylobacter, Salmonella, or E.coli, can cause bloody diarrhoea with blood mixed through loose stools.
Dark or tarry stool (melaena) suggests bleeding from the stomach or upper small intestine, where the blood has been partially digested before reaching the stool. Melaena has a distinctive smell. This requires urgent assessment.
Red-coloured stool without actual blood is a common source of confusion. Beetroot, red food dye in sweets, tomato-based food, and some other foods can colour stool red without any bleeding. A dietary history and a GP assessment can usually clarify this.
Common Causes by Age
In newborns, a common benign cause of blood in the stool is swallowed maternal blood during delivery or breastfeeding (from a cracked nipple). The Apt test, which a midwife or paediatrician can perform, distinguishes fetal from maternal blood: maternal blood contains adult haemoglobin and behaves differently from newborn blood when treated with sodium hydroxide. If the blood is maternal, no treatment is needed.
Necrotising enterocolitis (NEC) in premature or sick newborns is a serious cause of blood in the stool and is managed in the neonatal unit.
In infants, cow's milk protein allergy (CMPA) is a common cause of small streaks of blood in the stool, often with mucus and diarrhoea. The blood is bright red. Switching to an extensively hydrolysed formula, or eliminating cow's milk from the breastfeeding mother's diet, usually resolves it.
Anal fissures are small tears at the anal margin caused by hard stools. They cause bright red blood on the outside of the stool or on the nappy, and sometimes pain on defecation. They are very common at all ages and are treated by softening the stool and using emollient cream around the anal margin.
Intussusception, as discussed separately, causes redcurrant jelly stool in infants and toddlers and is a surgical emergency.
Infectious gastroenteritis, particularly from Campylobacter, can cause bloody diarrhoea. This typically involves blood mixed through loose, frequent stools and usually accompanies fever and abdominal pain. Most cases resolve without antibiotics, though Campylobacter is sometimes treated with azithromycin in severe or prolonged cases.
Juvenile polyps are benign growths on the colon wall that are relatively common in children. They cause painless bright red rectal bleeding. They are not pre-cancerous in children (unlike adult colonic polyps) but should be identified and removed by endoscopy.
In older children, Crohn's disease and ulcerative colitis (inflammatory bowel disease) can cause blood in the stool, typically with diarrhoea, abdominal pain, and weight loss. These are less common than the above causes but warrant consideration in a child with persistent or recurrent symptoms.
When to Seek Urgent Help
Go to A&E or call 999 if there is a large quantity of blood, if the child is pale and lethargic, if there is significant abdominal pain alongside the bleeding, if the stool is black and tarry, or if the child is a newborn.
See a GP the same day or next day for any blood in the stool that you cannot explain, for blood mixed through the stool (rather than only on the surface), for repeated episodes, or for blood with other symptoms including diarrhoea, fever, or abdominal pain.
A small streak of bright red blood on the surface of a hard stool in a child who is well and has no other symptoms can be assessed at a non-urgent GP appointment.
Key Takeaways
Blood in a child's stool is alarming for parents and warrants assessment, though most causes in children are benign. The most common causes by age group are: in newborns, swallowed maternal blood (Apt test distinguishes this from infant bleeding) or anal fissure; in infants, cow's milk protein allergy or anal fissure; in toddlers, anal fissure, polyps, or intussusception; in older children, constipation with fissures, infectious gastroenteritis, or rarely inflammatory bowel disease. Bright red blood on the surface of the stool or on toilet paper suggests an anal source (fissure or polyp). Dark or black tarry stool suggests bleeding higher in the digestive tract. Any significant quantity of blood, blood mixed through the stool, or blood with systemic symptoms (pallor, lethargy, significant abdominal pain) requires same-day assessment.
