Chapter 19 · Diarrhea, Intestinal Failure & Colon Disorders

Acute infective diarrhea (etiology, pathogenesis, clinical features, management) · Protracted diarrhoea in early infancy · Intestinal failure (definition, prevalence, etiology, investigations, management, quality of life, prognosis) · The colon: structure & function
📌 Core principles: Acute diarrhea is mainly viral (rotavirus, norovirus); management focuses on rehydration (ORS, IV) and continued feeding. Protracted diarrhea (>2 weeks) requires investigation for cow's milk allergy, postenteritis enteropathy, or immunodeficiency. Intestinal failure: reduced functional gut mass requiring parenteral nutrition; managed with intestinal rehabilitation, teduglutide, and transplantation. Colon: absorbs water/electrolytes, houses microbiota, forms stool; disorders include Hirschsprung, IBD, and functional constipation.

📖 Diarrhea, Intestinal Failure & Colon – Key Concepts

🦠 Acute infective diarrhea
Etiology: viral (rotavirus, norovirus, adenovirus, astrovirus); bacterial (Salmonella, Campylobacter, Shigella, E. coli, C. difficile); parasitic (Giardia, Cryptosporidium). Pathogenesis: enterotoxin, cytotoxin, mucosal invasion, malabsorption. Clinical features: watery or bloody stools, fever, vomiting, dehydration, abdominal pain. Management: oral rehydration solution (ORS) or IV fluids; continued feeding; zinc; antibiotics only for specific bacterial causes (dysentery, cholera).
🩺 Protracted diarrhoea (>2 weeks)
Cause: postenteritis enteropathy (secondary lactase deficiency), cow's milk protein allergy, coeliac disease, immunodeficiencies, congenital enteropathies (microvillus inclusion, tufting), IBD. Investigations: stool culture, faecal calprotectin, endoscopy with biopsies, sweat test, immunoglobulins, genetic studies. Treatment: treat underlying cause, nutritional support (elemental diet, PN), probiotics, avoid unnecessary antibiotics.
💧 Intestinal failure (IF)
Definition: reduction of functional gut mass below minimum needed for absorption of nutrients/fluids, requiring parenteral nutrition (PN). Prevalence: 10-15 per million children. Etiology: short bowel syndrome (NEC, atresia, volvulus, gastroschisis), neuromuscular disorders (CIPO), congenital enterocyte disorders. Investigations: contrast radiology, manometry, D-xylose absorption, liver biopsy (IFALD). Management: intestinal rehabilitation (trophic feeds, teduglutide), PN (lipid minimization to prevent cholestasis), prevention of line sepsis, surgical lengthening (STEP, LILT), intestinal transplantation. Quality of life: dependent on PN complications, family burden, need for transplant. Prognosis: 5-year survival >85% with multidisciplinary care; transplantation for irreversible IF.
🧫 The colon – structure & function
Structure: cecum, ascending, transverse, descending, sigmoid colon, rectum; teniae coli, haustra, appendices epiploicae. Function: absorption of water/electrolytes (NaCl), fermentation of unabsorbed carbohydrates (short-chain fatty acids), storage of stool, gut microbiota (commensal bacteria). Disorders: Hirschsprung disease, IBD (UC, Crohn), functional constipation, polyps, volvulus, diverticulitis (rare in children).

🔎 Symptom-based approach: acute vs chronic diarrhea, intestinal failure

1️⃣
Acute watery diarrhea + vomiting + dehydration – Most likely viral (rotavirus, norovirus). Assess dehydration status (WHO scale), rehydrate with ORS/low-osmolarity solution, continue breast/formula feeding, avoid antibiotics, consider zinc.
2️⃣
Bloody diarrhea (dysentery) + fever + tenesmus – Bacterial (Shigella, Campylobacter, Salmonella, E. coli O157). Stool culture, antibiotics if invasive or severe; monitor for HUS (E. coli O157).
3️⃣
Diarrhea persisting >2 weeks + faltering growth – Protracted diarrhea. Investigate: cow's milk protein allergy (trial of hypoallergenic formula), coeliac (tTG), immunodeficiency (IgA, IgG, lymphocyte subsets), parasites (Giardia). Endoscopy with biopsies.
4️⃣
Neonate with bilious vomiting, abdominal distension, and failure to pass meconium – Consider Hirschsprung (colonic aganglionosis) or distal intestinal obstruction (meconium ileus). Barium enema, rectal biopsy.
5️⃣
Chronic abdominal pain + bloating + alternating diarrhea/constipation without organic signs – Irritable bowel syndrome (IBS) or functional abdominal pain. Rome IV criteria, rule out red flags (weight loss, nocturnal symptoms, rectal bleeding).
⚠️ Red flags in chronic diarrhea: Failure to thrive, perianal fistulas (Crohn), bloody stools, nocturnal diarrhea, severe abdominal distension (pseudo-obstruction, malabsorption).

📋 Management algorithms: Acute diarrhea, Intestinal failure, Colonic disorders

💧
Acute diarrhea – rehydration protocol (WHO)
▪️ No/some dehydration: ORS (hypoosmolar) at 50–100 mL/kg over 4h.
▪️ Severe dehydration (shock): IV Ringer's lactate or 0.9% saline 20 mL/kg bolus, then maintenance.
▪️ Continue breastfeeding/regular diet after rehydration; avoid fruit juices.
▪️ Zinc supplementation (10–20 mg/day for 10–14 days) reduces severity/duration.
🩺
Intestinal failure (IF) – multidisciplinary management
▪️ Step 1: central venous access (tunneled line), start parenteral nutrition (PN) with lipid minimization (SMOF/Omegaven) to prevent IFALD.
▪️ Step 2: intestinal rehabilitation – trophic enteral feeding (continuous), teduglutide (GLP-2 analogue) for adaptation.
▪️ Step 3: manage complications: line sepsis (ethanol locks, antibiotics), SIBO (cyclic metronidazole/rifaximin), metabolic bone disease.
▪️ Step 4: consider surgical lengthening (STEP, LILT) or intestinal transplantation if progressive liver failure or loss of venous access.
🧫
Colonic disorders – approach to chronic constipation
▪️ Disimpaction: oral polyethylene glycol (PEG 3350) 1–1.5 g/kg/day for up to 6 days.
▪️ Maintenance: PEG (half-dose), increase fluids/fibre, toilet training, behavioural support.
▪️ Refractory: add stimulant laxatives (senna, bisacodyl), consider rectal enemas.
▪️ Hirschsprung: surgical pull-through after diagnosis.

💡 Reflex prompts – Diarrhea, Intestinal failure, Colon

🌊 A 2-year-old with acute watery diarrhea and mild dehydration. Best oral rehydration solution composition?
Hypoosmolar ORS (sodium 60–75 mEq/L, glucose 75 mmol/L) – reduced stool output.
🩸 A child with bloody diarrhea, afebrile, no dehydration, and history of eating undercooked hamburger. Most important complication to monitor?
Hemolytic uremic syndrome (E. coli O157:H7). Monitor platelets, creatinine, hemoglobin.
🍼 An infant with protracted diarrhea, vomiting, and perianal rash after starting cow's milk formula. Most likely?
Cow's milk protein allergy (non-IgE). Trial of extensively hydrolysed or amino acid formula.
💊 What is the first-line GLP-2 analogue for intestinal failure short gut syndrome?
Teduglutide – promotes intestinal adaptation, reduces parenteral nutrition requirements.
⚠️ A child on long-term PN develops conjugated hyperbilirubinemia, hepatosplenomegaly. Diagnosis?
Intestinal failure-associated liver disease (IFALD). Use fish oil-based lipid (Omegaven), cycle PN, treat sepsis.
🧪 What is the main function of the colon?
Absorption of water and electrolytes, fermentation of fiber to short-chain fatty acids, stool storage.
🔬 A child with chronic diarrhea, malabsorption, hypoalbuminemia, and dilated lacteals on biopsy. Diagnosis?
Intestinal lymphangiectasia (protein-losing enteropathy). MCT diet, treat underlying cause.
🦠 Most common bacterial cause of severe dysentery in children worldwide?
Shigella dysenteriae type 1 (also Shigella flexneri). Treat with azithromycin or ceftriaxone.
📏 A neonate with failure to pass meconium, abdominal distension, and X-ray shows microcolon. Likely diagnosis?
Hirschsprung disease (aganglionosis) or meconium ileus (CF). Rectal suction biopsy.
🍽️ Which vitamin deficiency is most common in short bowel syndrome with fat malabsorption?
Fat-soluble vitamins A, D, E, K. Monitor and supplement.