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How to work up a patient with bloody diarrhoea

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In the emergency department, we are often shown photos of poo – poo in nappies, poo in toilets. In our experience, most of the photos are taken because the carers have seen blood. The differential diagnosis is huge and depends a lot on age and clinical features. We’ll use some common clinical cases to help guide you for the next time you’re faced with a child with blood in their stool.

We’re not going to cover the times when blood is present in streaks on the surface of a formed stool. These may indicate an anal fissure due to constipation. We’re also not going to cover painless PR bleeding or those times when blood is only detected microscopically, such as in some cases of Meckel’s diverticulum. And we’re not talking about black, tarry stool – melaena – due to the presence of digested blood. This suggests upper GI bleeding. Instead, we’re going to think about cases where children present with blood mixed through their stool.

Case 1 – Infective diarrhoea

You’re chasing the micro results and coming across a stool sample positive for verotoxin-producing Escherichia coli (VTEC).

You pull the notes. The sample was from a 6-year-old boy.

They had attended the ED three days prior with a short history of bloody diarrhoea. The family have just returned from a fun-filled holiday on the West coast of Ireland. The highlight was a bracing swim in the Atlantic. The waves were high, and the craic was great, but as they were towelling off on the beach, the child’s father spotted a sign warning that the beach was contaminated with run-off water from a local farm.

The next day, it seems, the child started vomiting, then quickly developing diarrhoea, which became bloody. He had tolerated oral fluids in the ED and so had been discharged with oral hydration and hand hygiene advice.

What are you going to do now, armed with the knowledge that the bloody diarrhoea was secondary to VTEC?

Gastroenteritis and enterocolitis can cause bloody diarrhoea in any child or young person. Many organisms are capable of causing acute, bloody diarrhoea. Most tend to be caused by Campylobacter jejuniEscherichia coli O157:H7, other Shiga-toxin-producing E. coli, Salmonella species, Shigella species, and Yersinia species. Infection with Entamoeba histolytica and less common parasites can also cause bloody diarrhoea. Bloody diarrhoea associated with intestinal infection usually lasts three to eight days, though it may persist for up to three weeks in the case of Salmonella or Yersinia. Stool cultures help make the diagnosis, though clinical suspicion should be high if there’s been recent travel abroad, contact with known cases of gastroenteritis or possible ingestion of contaminated food or water. If the patient has been taking antibiotics recently, looking for C difficile toxin is worth considering.

10–15% of children with verocytotoxin-producing Escherichia coli (VTEC) may develop haemolytic uraemic syndrome (HUS). This usually occurs within 3 to 16 days of the onset of symptoms. HUS comprises a triad of haemolytic anaemia, thrombocytopenia and renal injury.

Should you give oral antibiotics in culture-positive bacterial gastroenteritis, such as salmonella or campylobacter? Generally, they’re not indicated except in children with severe symptoms, who are immunocompromised or if the stool microscopy shows Entamoeba histolytica or Shigella species. These are uncommon in the UK and Ireland (don’t forget to take that travel history).

Management of bloody diarrhoea associated with intestinal infection is supportive. If a child can drink and has no signs of moderate or severe dehydration, they can be looked after at home. They should return to the ED if blood persists in the stool for three weeks or more or if they develop any signs that may suggest HUS. These include new bleeding from the nose or mouth, blood in the urine, unusual bruising, a non-blanching rash, severe abdominal pain, severe headache, failure to pass urine for 12 hours, irritability, or puffiness of the face or ankles. If these symptoms develop or VTEC is isolated from the stool, they need a workup for HUS. This includes examination for signs or symptoms of renal failure plus blood work.

Haemolytic anaemia – Hb <10g/dL, positive schistocytes or fragmented red blood cells

Thrombocytopenia – platelets <150 x 103/mL

Acute kidney injury – elevated urea or creatinine

If the clinical exam is normal (no hypertension, abdominal pain or puffy ankles) and they only have one of the three HUS criteria, then what? Your management will depend on your local resources, but they need monitoring if they develop any of the other two criteria. This can happen as an inpatient or with sequential outpatient blood and assessments. If they don’t appear to have HUS, then a follow-up review by the child’s GP. If all three criteria are present, the child has HUS. You can read more about the pathophysiology and management of HUS in this review post.

Case 2 – Allergic enterocolitis

A 3-month-old infant is brought in. Mum has noticed streaks of blood in the nappy over the past three weeks. There isn’t much blood but mixed in with the stool.

When it first appeared, the parents sought advice from their community public health nurse.

They suggested trying a lactose-free formula and coming in for a review if it didn’t resolve.

The child is happy and otherwise healthy, with good weight gain, normal development, and vomiting.

In breast-fed neonates, ingested maternal blood from cracked or sore nipples can pass through the gut into the poo. Constipated children can get small anal fissures. They may lead to bright red blood in the nappy with each bowel motion. Blood in the urine is sometimes seen in urinary tract infections. In neonates, pink staining in the nappy is seen with urinary urate crystals. This is normal. A small amount of vaginal bleeding during the first couple of weeks of life is also completely normal due to a sudden drop in exogenous maternal oestrogen.

In slightly older infants, blood may be due to food protein allergies, most commonly cow’s milk protein allergies.

Non-IgE-mediated gastrointestinal food allergies typically present in infancy with delayed gastrointestinal symptoms of variable severity after exposure to specific dietary antigens. The diagnosis is clinical. It relies on a constellation of symptoms that improve on the removal of the offending food. Dietary avoidance, nutritional counselling, and supportive measures in the case of accidental exposure are a key part of management. The prognosis is favourable, and most cases resolve before school age.

Food Protein-Induced Allergic Proctocolitis (FPIAP) is the most common form. It tends to occur within the first few weeks of life due to indirect exposure to maternal dietary protein via breast milk. Infants present with loose, bloody stools, sometimes mixed with mucus. These infants look well, have no severe symptoms of vomiting or diarrhoea and no significant growth failure. Although FPIAP is most often seen in young infants, it can occur in older children.

Chronic Food Protein-Induced Enterocolitis Syndrome (FPIES) is a non-IgE-mediated gastrointestinal food hypersensitivity. It’s at the more severe end of the food protein allergy spectrum. It presents with chronic watery diarrhoea (occasionally with blood or mucus), intermittent vomiting, abdominal distension, and/or poor weight gain with dehydration and metabolic disturbances. Chronic FPIES occurs with persistent exposure to cow’s milk or soy-based formulas. A defining feature is the recurrence of symptoms presenting acutely when the trigger food is reintroduced after a period of withdrawal (an acute-on-chronic phenotype). Rarely has FPIES been reported in exclusively breastfed infants. The age of onset can vary, with FPIES to cow’s milk or soy usually presenting earlier within the first weeks or months of life, while FPIES to solids presents later at about 4 to 7 months of life. 30% of infants with FPIES develop atopic diseases, such as atopic dermatitis, asthma or allergic rhinitis.

The approach to both FPIAP and FPIES is the same. It’s always worth sending a stool sample for culture to rule out infective gastroenteritis. In formula-fed babies, changing the formula is diagnostic and therapeutic, with clinical improvement usually seen within one to two weeks. An extensively hydrolysed formula may resolve the symptoms in 80% of patients. If there’s no improvement after 4 weeks, an amino acid-based formula can help the remaining 20%.

Exclusively breastfed infants usually respond to the maternal elimination of all milk products (including butter). Occasionally, the elimination of multiple foods may be required, usually soy and/or egg. Breastfeeding mothers should be referred to a dietitian for nutritional support. When maternal dietary restriction is unsuccessful or too cumbersome, infants can be placed on an extensively hydrolysed formula.

Check out these posts for more on cow’s milk protein allergies, FPIES and different infant formulas.

Case 3 – Inflammatory Bowel Disease

An 8-year-old presents with a four-week history of intermittent bloody diarrhoea. He’s had cramping abdominal pain, and you notice that he also has a couple of mouth ulcers. There are bruise-like marks on both of his shins.

The stool culture sent by his GP was unremarkable.

Bloody diarrhoea is a common presenting symptom of inflammatory bowel disease (IBD). It is present in 85% of cases of ulcerative colitis and 50% of cases of Crohn’s. It may occur at any age but is more common in children over one year. Other symptoms and signs suggestive of IBD can be grouped into intestinal and extra-intestinal manifestations.

Intestinal manifestations include colicky abdominal pain, peri-defecation cramping, stool urgency, tenesmus, stool clustering, weight loss, deep oral ulceration, and perianal abscess/fistula/large skin tags.

Extra-intestinal manifestations include fever, growth failure, pubertal delay, clubbing, erythema nodosum, pyoderma gangrenosum, arthritis, liver disease, iritis, and uveitis.

As with any presentation of bloody diarrhoea, a stool sample should be sent for culture. But what else do you need to do?

A child with isolated, mild bloody diarrhoea And no other intestinal or extra-intestinal manifestations could be discharged without any investigations other than a stool culture and a review by their GP in 3 weeks to see if their symptoms have resolved. If it persists for more than three weeks, or if there are other intestinal or extra-intestinal manifestations, they should have blood workup including FBC, U&E, LFT, CRP and an ESR.

If they are unwell with fever or tachycardia, even if the bloody diarrhoea has only been present for a week or so, or if they’re experiencing many episodes a day or if they have raised inflammatory markers or anaemia, they need admission. You can then start supportive therapy with IV fluids and antipyretics whilst involving the paediatric gastroenterology team.

Don’t forget that children with an IBD diagnosis may present to ED with bloody diarrhoea, either due to an exacerbation of their underlying disease process or because of infection. Always send a stool culture, including C. difficile, and blood work-up.

Case 4 – Intussussception

A 2-month-old infant is brought to the ED with a distended belly and bilious vomiting. You open the nappy and see blood. What’s going on?

Children with an acute surgical abdomen may present with severe abdominal pain, persistent or bilious vomiting, guarding or rigidity and distension. They can also pass blood PR due to intestinal ischaemia. This is a surgical emergency.

Intussusception is the one cause of intestinal ischaemia we’ve all heard of (even if we can’t spell it). It can occur at any age but most commonly presents between 2 months and 2 years of age. 90% of cases are idiopathic or follow a viral infection or recent rotavirus vaccination. In older children, a pathological lead point may lead to intussusception. This can occur in Meckel’s diverticulum, Henoch-Schönlein Purpura, lymphoma, or luminal polyps (such as in Peutz-Jegher Syndrome).

Children present initially with episodic crying and irritability due to colicky abdominal pain. The child looks normal between the episodes. Parents sometimes give a history of sudden extreme lethargy or pallor. The child may look shocked, and textbooks say that you can palpate a mass in the upper right quadrant can be palpated, most often with an empty lower right quadrant “Dance sign”. The classic “redcurrant jelly” stool is due to blood and mucus but, in practice, isn’t seen often. It’s a late sign. Abdominal X-rays can show small bowel dilatation and paucity of gas in the right lower and upper quadrants. Free gas under the diaphragm indicates intestinal perforation, a surgical emergency. The gold standard test is abdominal ultrasonography. This shows a classic target (or doughnut) sign of an intussusceptum inside the intussuscipiens.

Case courtesy of Assoc Prof Frank Gaillard, From the case rID: 6502

Like many surgical emergencies, management with IV fluid resuscitation and nasogastric decompression. The telescoped section of the bowel needs reduction by air enema. It’s quick and reliable and can reduce the need for more invasive treatment. A paediatric surgeon is usually present as the risk of an enema is perforation. The highest risk of perforation is in children with a delayed diagnosis or those outside the usual preschool age range. Observation for 48 hours after reduction is required to monitor recurrence.

A common cause of neonatal bowel ischaemia is malrotation and volvulus. This may present with bilious vomiting. Malrotation and volvulus can present outside the neonatal period, although this is less common. Children (and even adults) may present with episodic abdominal pain, with the cause often undiagnosed until they eventually present with complete obstruction. As the volvulus develops, there may be sepsis and extensive intestinal gangrene. This is a surgical emergency.

In the younger patient, Necrotising Enterocolitis (NEC) is also worth considering. Although it is most often seen on the neonatal unit, infants can present to the ED with NEC. Preterm infants are most at risk, presenting up to 10 weeks of age. The classic signs are abdominal distension, bilious vomiting, signs of septicaemia and bloody diarrhoea. Term infants can also develop NEC, usually within the first week of life and often with a predisposing risk factor such as cardiac disease, polycythaemia, or gastrointestinal malformation (all of which can be undiagnosed until the neonate presents with NEC).

Case courtesy of Dr Hani Makky Al Salam, From the case rID: 9793

AP and lateral decubitus abdominal x-rays demonstrate an abnormal gas pattern, dilated loops, and thickened bowel walls. You may see little or no intestinal gas. This is more worrisome than diffuse distention. Pneumatosis intestinalis presents in 70%-80% of patients with NEC. It appears as a characteristic train-track lucency configuration within the bowel wall, though it may be fleeting or intermittent and is often an early finding.  

Treatment includes nasogastric decompression, TPN and IV antibiotics. This will require PICU involvement. Surgery is indicated in cases of clinical deterioration despite medical management or in the presence of pneumoperitoneum or gas in the portal vein.

Have a read of this post on an infant with haematemesis – could it be NEC?

In any suspected case of intestinal ischaemia, start fluid resuscitation. Huge amounts of fluid can be lost, and the child can become unstable and shocked. Get an erect x-ray, if possible, or one in the lateral decubitus position. Send blood for full blood count, renal function, clotting profile, group and save, and blood culture. After fluid resuscitation, they need an NG tube on free drainage and an urgent surgical referral.

Case 5 – Henoch-Schoenlein Purpura

A 9-year-old comes to the emergency department. They have been unwell for the last three days with a reduced appetite and abdominal discomfort.

A rash has developed over the extensor surface of both lower limbs that has become palpable and purpuric over time.

The child’s abdominal pain has worsened over the last 24 hours, and the bloody diarrhoea has prompted the parents to come in. The other notable findings on the clinical exam are a swollen, tender left knee. A urine dipstick shows 2+ blood.

Henoch Schoenlein Purpura (HSP) is a systemic IgA vasculitis associated with a characteristic palpable purpuric rash on the extensor surfaces of the lower limbs and buttocks, present in 95-100% of cases. This is the hallmark finding. Other features include gastrointestinal symptoms such as abdominal pain, vomiting and bloody stool; joint pain, particularly of the knees and ankles (present in 60-84%); and features of renal disease including subcutaneous oedema in 20-50%, scrotal oedema in 2-35% and overt (or microscopic) haematuria.

Treatment is mainly supportive of hydration and analgesia. Any child diagnosed with HSP requires follow-up with regular urinalysis and blood pressure monitoring to ensure complete resolution of symptoms and early monitoring for complications. These complications include gastrointestinal bleeding, intussusception, bowel infarction, proteinuria, nephritis, and chronic renal failure.

Case 6 – Hirschpung’s Associated Enterocolitis

A 3-month-old infant with Down Syndrome presents to the ED with multiple episodes of bloody diarrhoea over the last 24 hours. They do not look well.

They are hypothermic, tachycardic and hypotensive. Their abdomen is distended and tender. Wisely, you start treatment for generalized sepsis with fluids and IV antibiotics.

When you delve into the history, it’s clear the infant has been constipated since birth. The parents have tried over-the-counter medications and changed the formula three times.

Hirschsprung’s disease classically presents with constipation and delayed passage of meconium. However, 25% of infants present with Hirschprung’s Associated Enterocolitis (HAEC), secondary to prolonged stasis of stool in the gut. This allows the proliferation of bacteria, leading to abdominal distension with tenderness, severe watery and sometimes bloody diarrhoea, and sepsis. The infant may develop hypovolaemic shock due to colonic perforation. HAEC can be potentially life-threatening. Suspect it in any unwell child with bloody diarrhoea and a history of constipation or delayed passage of meconium. It must be included in the differential of an unwell child with Hirschprung’s, even after correction. Children with Trisomy 21, long-segment Hirschprung’s Disease, and previous HAEC are most at risk, as well as those in the postoperative period. Early recognition of Hirschsprung disease before the onset of enterocolitis reduces morbidity and mortality.     

Look at this post to learn about Hirschprung’s disease and HAEC, as well as their pathophysiology and management in the ED.

Using an age-based framework can help segregate common causes in infants and older children to help differentiate between different presentations and direct management. And don’t forget to include anal fissures and Meckel’s diverticulum in your differentials if the child is either constipated or has painless blood per rectum.

Selected references

Frykman PK, Short SS. Hirschsprung-associated enterocolitis: prevention and therapy. Semin Pediatr Surg. 2012;21(4):328-335. doi:10.1053/j.sempedsurg.2012.07.007 Hirschsprung-Associated Enterocolitis: Prevention and Therapy (

Murphy MS. Management of bloody diarrhoea in children in primary care. BMJ. 2008;336(7651):1010-1015. doi:10.1136/bmj.39542.440417.BE

Labrosse R, Graham F, Caubet JC. Non-IgE-Mediated Gastrointestinal Food Allergies in Children: An Update. Nutrients. 2020;12(7):2086. Published 2020 Jul 14. doi:10.3390/nu12072086

Roache-Robinson P, Hotwagner DT. Henoch Schönlein Purpura. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:


  • Dani Hall is a PEM consultant in Dublin, member of the DFTB executive team and senior clinical lecturer on the Queen Mary University of London and DFTB PEM MSc. Dani is passionate about advocating for children and young people, and loves good coffee, a good story and her family. She/her.

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  • Michael is a paediatric emergency medicine consultant in Children’s Health Ireland. He’s Associate Prof with University College Dublin. He loves research when it translates to the floor. Likes a sea swim and a cycle if there’s time. All is second to spending time with his 4 children. he/him

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