# Seminar 06: Pediatric Gastrointestinal Disorders ## Year 3: Pediatrics Clerkship --- ## Learning Objectives By the end of this seminar, students will be able to: 1. Evaluate acute abdominal pain in children 2. Recognize and manage gastroenteritis and dehydration 3. Diagnose and treat constipation and GERD 4. Identify surgical emergencies of the GI tract 5. Describe inflammatory bowel disease in children 6. Recognize celiac disease and food allergies --- ## Lecture Outline ### I. Approach to Abdominal Pain The evaluation of abdominal pain in children requires careful attention to history elements that help distinguish benign from serious conditions. Location of pain provides important diagnostic clues, with periumbilical pain often representing early appendicitis or functional abdominal pain, while right lower quadrant pain suggests appendicitis and epigastric pain may indicate gastritis or peptic ulcer disease. The character of pain also guides the differential, as colicky pain that comes in waves typically suggests intestinal obstruction or intussusception, while constant pain raises concern for peritonitis or other inflammatory processes. Duration distinguishes acute conditions requiring urgent evaluation from chronic conditions that may warrant outpatient workup, and associated symptoms including vomiting, diarrhea, and fever help narrow the diagnostic possibilities. The differential diagnosis of abdominal pain varies significantly by age group, making age-based categorization essential for clinical reasoning. In infants, common causes include colic, gastroesophageal reflux, intussusception, and the life-threatening malrotation with volvulus that requires immediate recognition. Toddlers most commonly present with constipation, viral gastroenteritis, or intussusception, while school-age children frequently have functional abdominal pain, appendicitis, or constipation. Adolescents develop conditions seen in adults including appendicitis and require consideration of ovarian pathology in females, including ovarian torsion, ruptured ovarian cyst, and ectopic pregnancy. Physical examination of the abdomen requires systematic assessment for signs of peritonitis and other concerning findings. Guarding, which represents voluntary muscle contraction to protect the abdomen, suggests peritoneal irritation, while rebound tenderness confirms peritoneal inflammation and indicates urgent surgical consultation. Absent or diminished bowel sounds suggest ileus or obstruction, and palpable masses may represent intussusception, tumor, or fecal impaction. Specific examination maneuvers help localize appendicitis, including the psoas sign elicited by hip extension suggesting retrocecal appendicitis, and the obturator sign elicited by internal rotation of the flexed hip suggesting pelvic appendicitis. Red flag symptoms requiring urgent evaluation must be recognized immediately to prevent life-threatening complications. Bilious vomiting in a neonate represents intestinal obstruction distal to the ampulla of Vater and constitutes a surgical emergency until proven otherwise, most commonly caused by malrotation with volvulus. Bloody stool may indicate intussusception, inflammatory bowel disease, or infectious colitis and requires prompt evaluation. Signs of peritonitis including rigidity, rebound tenderness, and the child lying very still indicate perforation or severe inflammation requiring immediate surgical consultation. Weight loss, growth failure, and nocturnal symptoms that wake the child from sleep suggest organic disease rather than functional conditions. Panel A: Anatomical diagram showing locations of abdominal pain with corresponding differential diagnoses at each location including periumbilical, right lower quadrant, epigastric, and diffuse patterns. Panel B: Clinical photograph demonstrating proper technique for assessing rebound tenderness in a pediatric patient with suspected peritonitis. Panel C: Algorithm flowchart for evaluation of acute abdominal pain based on age groups showing different diagnostic pathways for infants, toddlers, school-age children, and adolescents. Panel D: Illustration of red flag symptoms requiring urgent evaluation including bilious vomiting, bloody stool, peritoneal signs, and nocturnal symptoms. --- ### II. Gastroenteritis and Dehydration Gastroenteritis remains one of the most common reasons for pediatric emergency visits, with viral pathogens causing the majority of cases. Rotavirus was historically the leading cause of severe gastroenteritis in young children before widespread vaccination, and norovirus has now become the most common cause of epidemic gastroenteritis in all age groups. Adenovirus types 40 and 41 cause endemic gastroenteritis with prolonged symptoms, while astrovirus predominantly affects young children and immunocompromised patients. Viral gastroenteritis typically presents with vomiting followed by watery diarrhea and low-grade fever, with symptoms generally resolving within 5-7 days. Bacterial gastroenteritis requires consideration when specific clinical features suggest bacterial etiology. Salmonella species cause foodborne illness associated with poultry, eggs, and reptile exposure, typically producing fever, diarrhea, and abdominal cramps. Shigella causes dysentery with bloody diarrhea and high fever, and uniquely among enteric pathogens may cause seizures even without significant fever due to neurotoxin production. Campylobacter jejuni, associated with undercooked poultry and unpasteurized milk, causes bloody diarrhea and may trigger post-infectious complications including Guillain-Barre syndrome. Enterohemorrhagic Escherichia coli O157:H7 produces Shiga toxin that causes bloody diarrhea and may progress to hemolytic uremic syndrome, making antibiotic treatment contraindicated as it may increase toxin release. Accurate assessment of dehydration severity guides treatment decisions and disposition planning. Mild dehydration representing 3-5% volume loss presents with slightly decreased urine output and mildly dry mucous membranes but normal vital signs and mental status. Moderate dehydration at 6-9% volume loss causes decreased tears, sunken eyes, tachycardia, and delayed capillary refill greater than 2 seconds. Severe dehydration exceeding 10% produces mottled skin, lethargy or irritability, markedly prolonged capillary refill, weak pulses, and hypotension representing impending shock. Clinical assessment combines multiple findings, as no single sign reliably determines dehydration severity, and acute weight change provides the most accurate assessment when a recent pre-illness weight is available. Oral rehydration therapy represents the cornerstone of gastroenteritis management and has dramatically reduced mortality from dehydration worldwide. Oral rehydration solutions containing glucose and sodium in specific concentrations facilitate coupled sodium-glucose transport across intestinal epithelium, optimizing water absorption. Commercial preparations and World Health Organization oral rehydration solution provide approximately 75-90 mEq/L sodium and 75-90 mmol/L glucose, while common household beverages including apple juice and sports drinks contain excessive sugar and inadequate sodium. Mild dehydration requires replacement over 4 hours with 50 mL/kg of oral rehydration solution plus replacement of ongoing losses, while moderate dehydration requires 100 mL/kg over 4 hours. Severe dehydration necessitates intravenous fluid resuscitation with isotonic crystalloid boluses of 20 mL/kg, repeated as needed until perfusion improves. Panel A: Comparison chart showing clinical features of mild, moderate, and severe dehydration including vital signs, physical examination findings, and estimated fluid deficit percentages. Panel B: World Health Organization oral rehydration solution composition compared to inappropriate alternatives showing sodium, potassium, glucose, and osmolarity values. Panel C: Step-by-step protocol for oral rehydration therapy showing volume calculations and frequency of administration for different dehydration severities. Panel D: Flowchart for intravenous fluid resuscitation in severe dehydration showing initial bolus, reassessment points, and transition to maintenance fluids. --- ### III. Constipation Functional constipation represents the most common cause of constipation in children, affecting up to 30% of children at some point during childhood. The definition includes infrequent defecation with fewer than 3 bowel movements per week, hard and painful stools, withholding behaviors, and fecal soiling from overflow incontinence around impacted stool. Withholding behaviors develop when children experience painful defecation and subsequently avoid stooling, creating a vicious cycle where stool retention leads to harder, larger stools that cause more pain. Encopresis, defined as fecal soiling in a toilet-trained child, results from overflow incontinence around impacted stool and should not be confused with behavioral problems or poor toilet training. Organic causes of constipation must be considered, particularly in neonates and infants with constipation from birth. Hirschsprung disease results from absence of ganglion cells in the distal colon, preventing normal peristalsis and causing functional obstruction. Classic presentation includes delayed passage of meconium beyond 48 hours of life, abdominal distension, and bilious vomiting, though short-segment disease may present later with chronic constipation. Hypothyroidism causes constipation along with other features including growth failure, developmental delay, and prolonged jaundice. Spinal cord abnormalities including tethered cord and spinal dysraphism cause neurogenic bowel dysfunction and are suggested by cutaneous findings over the spine including dimples, hair tufts, or lipomas. The Rome IV criteria provide standardized diagnostic criteria for functional constipation in children. For infants and toddlers, diagnosis requires at least 2 of the following for at least 1 month: 2 or fewer defecations per week, excessive stool retention, painful or hard bowel movements, large-diameter stools, and presence of a large fecal mass in the rectum. For older children, the same criteria apply but must be present for at least 2 months, and encopresis at least once per week is an additional criterion. Digital rectal examination typically reveals a large amount of hard stool in the rectal vault, distinguishing functional constipation from Hirschsprung disease where the rectum is often empty despite abdominal distension. Management of functional constipation involves disimpaction followed by maintenance therapy and behavioral modifications. Disimpaction removes the fecal mass using oral polyethylene glycol 3350 at doses of 1-1.5 g/kg/day for 3-6 days, or rectal enemas when oral therapy is refused or ineffective. Maintenance therapy continues with daily polyethylene glycol 3350 at 0.4-0.8 g/kg/day to produce 1-2 soft stools daily, and treatment must continue for months to allow the distended rectum to return to normal size. Dietary modifications including increased fiber and fluid intake support medication therapy but are insufficient alone for established constipation. Behavioral intervention establishes regular toileting routines, typically 5-10 minutes after meals to take advantage of the gastrocolic reflex, with positive reinforcement for sitting on the toilet regardless of results. Panel A: Rome IV diagnostic criteria for functional constipation displayed as a checklist with age-specific requirements for infants/toddlers and children/adolescents. Panel B: Anatomical illustration comparing normal rectal anatomy with impacted rectum showing dilated ampulla and overflow incontinence mechanism. Panel C: Disimpaction protocol flowchart showing polyethylene glycol dosing, timeline, and transition to maintenance therapy. Panel D: Behavioral toilet training approach showing sitting schedule, reward systems, and proper positioning on toilet with footstool. --- ### IV. Gastroesophageal Reflux Distinguishing physiologic gastroesophageal reflux from pathologic gastroesophageal reflux disease guides appropriate management. Physiologic GER affects up to 50% of infants in the first months of life and manifests as effortless regurgitation of stomach contents without associated symptoms or complications. These "happy spitters" maintain normal growth, have normal feeding behavior, and require no intervention beyond parental reassurance and anticipatory guidance. Symptoms typically peak around 4 months of age and resolve by 12-18 months as the lower esophageal sphincter matures and the infant spends more time upright. Pathologic GERD causes symptoms or complications including poor weight gain, feeding refusal, irritability, respiratory symptoms, and esophagitis. GERD symptoms vary significantly by age group, reflecting developmental differences in symptom expression and disease manifestations. Infants with GERD demonstrate irritability during or after feeds, feeding refusal, arching of the back (Sandifer syndrome), failure to thrive, and respiratory symptoms including recurrent wheeze and aspiration pneumonia. Older children may describe regurgitation, abdominal pain, and water brash but often have difficulty articulating specific symptoms. Adolescents present more similarly to adults with classic heartburn described as substernal burning, chest pain, and acid taste in the mouth. Respiratory manifestations including chronic cough, recurrent pneumonia, and reactive airway disease occur at all ages and may be the primary presenting complaint. Diagnosis of GERD in pediatrics remains primarily clinical, with testing reserved for atypical presentations or treatment failures. Empiric treatment with acid suppression serves as a diagnostic trial in older children with classic symptoms, with symptom improvement supporting the diagnosis. Upper GI series identifies anatomic abnormalities including hiatal hernia, stricture, and malrotation but does not diagnose reflux itself as brief reflux episodes are physiologic. pH-impedance monitoring provides the most sensitive detection of reflux episodes and correlates symptoms with reflux events, helping determine if atypical symptoms result from GERD. Upper endoscopy with biopsy identifies esophagitis and excludes alternative diagnoses including eosinophilic esophagitis, infection, and Barrett's esophagus in patients with chronic symptoms. Management of GERD follows a stepwise approach beginning with lifestyle modifications and advancing to pharmacotherapy when needed. Positional therapy keeps infants upright for 20-30 minutes after feeds and elevates the head of the bed, though prone positioning should never be recommended due to SIDS risk. Thickened feeds using rice cereal reduce visible regurgitation in infants but do not improve other outcomes. Proton pump inhibitors including omeprazole and lansoprazole provide superior acid suppression compared to histamine-2 receptor blockers and represent first-line pharmacotherapy for erosive esophagitis. Treatment duration of 4-8 weeks allows mucosal healing, followed by the lowest effective dose or discontinuation with monitoring for symptom recurrence. Surgical fundoplication remains reserved for patients with life-threatening complications including recurrent aspiration pneumonia or failure of maximal medical therapy. Panel A: Side-by-side comparison of physiologic GER and pathologic GERD features including symptom characteristics, growth patterns, and management implications. Panel B: Age-specific GERD presentations showing typical symptoms in infants, children, and adolescents with anatomical correlates. Panel C: Diagnostic algorithm for GERD showing when to employ empiric treatment versus diagnostic testing including pH-impedance monitoring and endoscopy. Panel D: Treatment ladder for GERD showing progression from lifestyle modifications through pharmacotherapy to surgical intervention with indications for each step. --- ### V. Surgical Emergencies Appendicitis represents the most common surgical emergency in children, with peak incidence between 10-12 years of age. Classic presentation begins with periumbilical pain caused by visceral inflammation that subsequently localizes to the right lower quadrant as parietal peritoneal irritation develops over 12-24 hours. Associated symptoms include anorexia, nausea, vomiting occurring after pain onset, and low-grade fever, though these features may be absent or atypical in young children. Physical examination reveals right lower quadrant tenderness, guarding, and positive signs including Rovsing's sign (pain in RLQ with palpation of LLQ) and the psoas sign. Diagnosis uses clinical scoring systems combined with imaging, with ultrasound preferred initially and CT scan when ultrasound is inconclusive, and treatment is appendectomy with perioperative antibiotics. Intussusception occurs when one segment of bowel telescopes into an adjacent segment, most commonly ileocolic with terminal ileum invaginating into the cecum and colon. Peak incidence occurs between 6 months and 3 years of age, with a viral prodrome present in many cases and pathologic lead points including Meckel diverticulum and lymphoma becoming more common in older children. Classic presentation includes episodic colicky abdominal pain causing the child to draw up the legs, vomiting, and eventually "currant jelly" stool representing blood and mucus, though this full triad appears in only one-third of cases. Ultrasound reveals the characteristic "target sign" or "doughnut sign" in cross-section and "pseudokidney" sign in longitudinal view. Treatment involves air or contrast enema reduction performed by radiology, which is successful in 80-95% of cases without peritonitis, while surgical reduction is required for failed enema or signs of perforation. Malrotation with midgut volvulus constitutes a true surgical emergency requiring immediate recognition and treatment. Malrotation results from incomplete rotation of the midgut during fetal development, creating abnormal peritoneal attachments (Ladd bands) and a narrow mesenteric base predisposing to volvulus. Presentation includes bilious vomiting in an otherwise well-appearing neonate, though abdominal distension and bloody stools indicate progression to ischemia. The critical teaching point is that bilious vomiting in a neonate represents malrotation with volvulus until proven otherwise and demands urgent evaluation. Upper GI series demonstrates malposition of the duodenojejunal junction (normally to the left of the spine at the level of the pylorus), and treatment is emergent Ladd procedure to untwist the bowel, lyse bands, and widen the mesenteric base. Pyloric stenosis typically presents between 2-8 weeks of age with progressive, projectile, non-bilious vomiting immediately after feeds. The condition results from hypertrophy of the pyloric muscle causing gastric outlet obstruction, with the classic patient being a first-born male though it affects both sexes. Physical examination may reveal a palpable olive-shaped mass in the right upper quadrant and visible gastric peristaltic waves. Prolonged vomiting produces characteristic hypochloremic, hypokalemic metabolic alkalosis due to loss of gastric acid and renal potassium wasting. Ultrasound confirms the diagnosis when pyloric muscle thickness exceeds 3 mm or channel length exceeds 15-17 mm, and treatment is pyloromyotomy after correction of fluid and electrolyte abnormalities. Panel A: Clinical progression of appendicitis from periumbilical pain to right lower quadrant localization with timeline and associated symptoms at each stage. Panel B: Intussusception anatomy showing ileocolic telescoping with target sign on ultrasound and reduction procedure using air enema. Panel C: Malrotation embryology and volvulus mechanism with upper GI series findings demonstrating malpositioned duodenojejunal junction and corkscrew sign. Panel D: Pyloric stenosis showing hypertrophied pylorus, ultrasound measurements, and electrolyte abnormalities with pathophysiology of hypochloremic hypokalemic metabolic alkalosis. --- ### VI. Inflammatory Bowel Disease Inflammatory bowel disease in pediatrics includes Crohn's disease and ulcerative colitis, with approximately 25% of patients presenting before age 20. Both conditions result from dysregulated immune responses to intestinal microbiota in genetically susceptible individuals, with environmental triggers including antibiotic exposure and dietary factors playing modulating roles. Crohn's disease may affect any portion of the gastrointestinal tract from mouth to anus, most commonly involving the terminal ileum, and causes transmural inflammation with skip lesions (normal segments between diseased areas). Ulcerative colitis involves only the colon in a continuous pattern extending proximally from the rectum, which is always involved, and inflammation remains limited to the mucosa and submucosa. Clinical features differ between Crohn's disease and ulcerative colitis, though significant overlap exists. Crohn's disease commonly presents with abdominal pain, diarrhea that may or may not be bloody, weight loss, and growth failure, with perianal disease including fissures, fistulas, and abscesses present in one-third of pediatric patients. Ulcerative colitis classically presents with bloody diarrhea, urgency, and tenesmus, with abdominal pain typically less prominent than in Crohn's disease. Growth failure occurs in both conditions but is more common in Crohn's disease and may precede gastrointestinal symptoms by months to years. Extraintestinal manifestations affect up to 25% of pediatric IBD patients and include arthritis, erythema nodosum, pyoderma gangrenosum, uveitis, and primary sclerosing cholangitis. Diagnosis requires endoscopic evaluation with histopathology, as no laboratory test definitively establishes the diagnosis. Laboratory findings include anemia from chronic disease or iron deficiency, elevated inflammatory markers (ESR and CRP), hypoalbuminemia from protein-losing enteropathy, and elevated fecal calprotectin indicating intestinal inflammation. Colonoscopy with ileal intubation and esophagogastroduodenoscopy with biopsies allow direct visualization and histologic confirmation, with Crohn's disease showing granulomas and transmural inflammation while ulcerative colitis shows crypt abscesses and mucosal inflammation. Magnetic resonance enterography or capsule endoscopy evaluates small bowel involvement in Crohn's disease not accessible by standard endoscopy. Treatment goals include inducing and maintaining remission while optimizing growth and quality of life. Induction therapy uses corticosteroids for moderate-severe flares, though exclusive enteral nutrition using elemental or polymeric formula provides equivalent efficacy for Crohn's disease while avoiding steroid side effects. Maintenance therapy employs immunomodulators including azathioprine, 6-mercaptopurine, and methotrexate, with biologic agents (anti-TNF medications including infliximab and adalimumab) increasingly used early in disease course for moderate-severe or high-risk disease. 5-aminosalicylic acid medications (mesalamine) treat mild ulcerative colitis but have limited efficacy in Crohn's disease. Surgical management includes colectomy for medically refractory ulcerative colitis (which is curative) and resection of strictures or fistulas in Crohn's disease, though surgery is not curative for Crohn's. Panel A: Comparison diagram of Crohn's disease and ulcerative colitis showing anatomical distribution, depth of inflammation, endoscopic appearance, and histologic features. Panel B: Extraintestinal manifestations of IBD displayed on body diagram including joint, skin, eye, and hepatobiliary involvement with prevalence data. Panel C: Diagnostic workup algorithm showing laboratory tests, fecal markers, endoscopy with biopsy, and imaging modalities with typical findings for each condition. Panel D: Treatment pyramid showing stepwise therapy from aminosalicylates through immunomodulators to biologic agents with indications for each level. --- ### VII. Celiac Disease Celiac disease is an immune-mediated enteropathy triggered by gluten ingestion in genetically susceptible individuals carrying HLA-DQ2 or HLA-DQ8 haplotypes. Gluten, the storage protein found in wheat, barley, and rye, contains gliadin peptides that cross the intestinal epithelium and undergo deamidation by tissue transglutaminase. The modified gliadin peptides bind HLA molecules and activate T-cell mediated immune responses causing villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis in the small intestine. Prevalence has increased dramatically and now affects approximately 1% of the population, with higher rates in first-degree relatives of affected individuals, patients with type 1 diabetes, Down syndrome, Turner syndrome, and autoimmune thyroid disease. Clinical presentations of celiac disease vary widely, ranging from classic malabsorption to subtle or extraintestinal manifestations. Classic celiac disease presents in toddlers after gluten introduction with chronic diarrhea, abdominal distension, failure to thrive, and irritability. Non-classic presentations are now more common and include constipation, short stature, delayed puberty, iron-deficiency anemia refractory to oral supplementation, dental enamel defects, and recurrent aphthous stomatitis. Many patients remain asymptomatic or oligosymptomatic and are detected through screening of high-risk groups. Dermatitis herpetiformis, characterized by intensely pruritic papulovesicular lesions on extensor surfaces, represents the cutaneous manifestation of celiac disease and also responds to gluten elimination. Diagnosis requires serologic testing followed by intestinal biopsy while the patient continues consuming gluten. Tissue transglutaminase IgA (TTG-IgA) serves as the first-line screening test with sensitivity and specificity exceeding 95%. Total IgA level must be measured concurrently because IgA deficiency, which is more common in celiac disease, causes false-negative TTG-IgA results, requiring IgG-based testing in deficient patients. Endomysial antibodies (EMA-IgA) provide highly specific confirmatory testing when TTG-IgA is borderline. Upper endoscopy with duodenal biopsies remains the gold standard for diagnosis, demonstrating villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes (Marsh classification). HLA-DQ2/DQ8 testing has high negative predictive value and can exclude celiac disease when negative but cannot confirm diagnosis when positive. Treatment requires strict, lifelong adherence to a gluten-free diet, eliminating all wheat, barley, rye, and cross-contaminated products. Consultation with a registered dietitian experienced in celiac disease is essential for comprehensive education about hidden gluten sources, label reading, and maintaining nutritional adequacy. Oats are intrinsically gluten-free but frequently cross-contaminated, and pure oats may be introduced cautiously after initial dietary response. Monitoring includes clinical assessment of symptom resolution, normalization of TTG-IgA typically within 6-12 months reflecting mucosal healing, and screening for associated conditions including osteoporosis and thyroid disease. Patients with persistent symptoms or elevated serology despite reported dietary adherence should be evaluated for inadvertent gluten exposure, refractory celiac disease, or alternative diagnoses including microscopic colitis or small intestinal bacterial overgrowth. Panel A: Pathophysiology diagram showing gliadin crossing intestinal epithelium, tissue transglutaminase deamidation, HLA-DQ presentation, and T-cell activation leading to villous atrophy. Panel B: Clinical presentation spectrum ranging from classic malabsorption in toddlers through non-classic presentations to silent celiac disease detected by screening. Panel C: Diagnostic algorithm showing serologic testing pathway including TTG-IgA, total IgA level, confirmatory testing, and role of intestinal biopsy with Marsh classification. Panel D: Gluten-free diet education showing safe and unsafe grains, hidden gluten sources, cross-contamination prevention, and monitoring parameters. --- ### VIII. Food Allergies IgE-mediated food allergies represent immediate hypersensitivity reactions occurring within minutes to 2 hours of food ingestion. The most common allergens in children include cow's milk, egg, peanut, tree nuts, wheat, soy, fish, and shellfish, with milk, egg, wheat, and soy allergies typically outgrown while peanut, tree nut, fish, and shellfish allergies more often persist. Symptoms range from mild cutaneous manifestations (urticaria, angioedema) to life-threatening anaphylaxis involving multiple organ systems. Diagnosis combines detailed history correlating specific foods with reproducible symptoms, skin prick testing or serum-specific IgE levels, and oral food challenges when history and testing are discordant. Management requires strict avoidance of allergens, comprehensive education about hidden allergens and label reading, and provision of epinephrine auto-injectors with anaphylaxis action plans. Non-IgE-mediated food allergies present with delayed symptoms primarily affecting the gastrointestinal tract. Food protein-induced allergic proctocolitis typically presents in young breastfed infants with blood-streaked stools but otherwise appears well without systemic symptoms. Diagnosis is clinical and confirmed by symptom resolution with elimination of the causative food (usually cow's milk or soy) from the maternal or infant diet. Food protein-induced enterocolitis syndrome (FPIES) causes more severe symptoms including profuse vomiting 2-4 hours after ingestion, sometimes progressing to dehydration and lethargy mimicking sepsis. Common triggers include cow's milk, soy, rice, and oats, and the condition typically resolves by age 3-5 years. Eosinophilic esophagitis presents with feeding difficulties in young children and dysphagia with food impaction in older children and adolescents, diagnosed by esophageal biopsies showing eosinophilic infiltration. Food protein-induced enterocolitis syndrome deserves particular attention due to its dramatic presentation and potential for diagnostic confusion. Acute FPIES presents with repetitive projectile vomiting 1-4 hours after ingestion of the triggering food, often accompanied by pallor, lethargy, and hypotonia that may progress to hypovolemic shock. Laboratory findings during acute episodes include leukocytosis with neutrophilia, thrombocytosis, and metabolic acidosis, potentially leading to misdiagnosis as sepsis. Chronic FPIES occurs with regular ingestion of the trigger food and causes failure to thrive, chronic diarrhea, and hypoalbuminemia. Diagnosis is clinical based on characteristic history and symptom resolution with food elimination, with oral food challenge performed under medical supervision to confirm diagnosis or assess resolution. Management involves strict avoidance and intravenous ondansetron and fluids during acute reactions. Management of food allergies requires a comprehensive approach addressing safety, nutrition, and quality of life. Dietary elimination must be complete as even trace amounts may trigger reactions in highly sensitive individuals. Nutritional counseling ensures dietary adequacy, particularly for milk-allergic children at risk for calcium and vitamin D deficiency. School and childcare action plans specify allergen avoidance measures, symptom recognition, and emergency treatment protocols. Epinephrine auto-injectors should be available in all settings where the child spends time, with training provided to caregivers on recognition of anaphylaxis and proper injection technique. Oral immunotherapy, involving gradual administration of increasing allergen doses, has emerged as a treatment option for peanut allergy and is under investigation for other allergens. Panel A: IgE-mediated food allergy pathway showing allergen exposure, IgE cross-linking on mast cells, mediator release, and clinical manifestations ranging from urticaria to anaphylaxis. Panel B: Non-IgE-mediated food allergy comparison showing allergic proctocolitis, FPIES, and eosinophilic esophagitis with timing of symptoms, typical age, and diagnostic approach. Panel C: FPIES acute episode recognition showing timeline from ingestion to symptom onset, characteristic features, laboratory findings, and management protocol. Panel D: Comprehensive allergy management plan components including dietary avoidance, emergency preparedness, school protocols, and monitoring for natural resolution. --- ### IX. Other GI Conditions Meckel's diverticulum represents the most common congenital anomaly of the gastrointestinal tract, resulting from incomplete obliteration of the omphalomesenteric (vitelline) duct connecting the fetal midgut to the yolk sac. The "rule of 2s" describes its classic features: present in 2% of the population, located 2 feet from the ileocecal valve, approximately 2 inches in length, and most commonly symptomatic before age 2 years. Approximately half of symptomatic diverticula contain ectopic gastric or pancreatic mucosa, with gastric mucosa causing peptic ulceration and painless rectal bleeding that is classically brick-red or maroon-colored. Diagnosis is made by Meckel's scan (technetium-99m pertechnetate scintigraphy), which detects ectopic gastric mucosa, though sensitivity is imperfect and negative scans do not exclude the diagnosis. Treatment of symptomatic Meckel's diverticulum is surgical resection. Hirschsprung disease results from failure of neural crest cell migration to the distal colon during fetal development, producing a segment of bowel lacking ganglion cells in the myenteric and submucosal plexuses. The aganglionic segment cannot relax, creating functional obstruction and proximal dilation. Classic presentation includes failure to pass meconium within 48 hours of birth (present in 90% of affected neonates), abdominal distension, and bilious vomiting. Rectal examination characteristically produces explosive release of gas and stool (squirt sign) as the finger bypasses the narrowed aganglionic segment. Contrast enema shows a transition zone between the narrow aganglionic distal segment and the dilated proximal normal bowel. Diagnosis is confirmed by rectal suction biopsy demonstrating absence of ganglion cells and nerve fiber hypertrophy, and treatment is surgical pull-through procedure with resection of the aganglionic segment. Biliary atresia represents a progressive fibro-obliterative disease of the extrahepatic bile ducts requiring early diagnosis and treatment to prevent cirrhosis. Presentation includes persistent conjugated (direct) hyperbilirubinemia beyond 2 weeks of age, acholic (pale) stools, dark urine, and hepatomegaly. The critical teaching point is that conjugated hyperbilirubinemia in an infant is never physiologic and requires urgent evaluation. Diagnosis involves hepatobiliary ultrasound (which may show absent or abnormal gallbladder), hepatobiliary scintigraphy (HIDA scan) demonstrating failure of tracer excretion into the intestine, and ultimately intraoperative cholangiography. Kasai portoenterostomy, which creates a direct connection between the porta hepatis and a Roux-en-Y jejunal limb, must be performed before 60 days of age for optimal outcomes, though many patients eventually require liver transplantation. Inguinal hernias in children are almost exclusively indirect, resulting from failure of processus vaginalis closure allowing peritoneal contents to protrude through the internal inguinal ring. Presentation includes intermittent inguinal bulging that increases with crying, straining, or Valsalva maneuver and reduces when the child relaxes or with gentle pressure. Incarceration occurs when hernia contents become trapped and cannot be reduced, presenting with a firm, tender, non-reducible mass and potentially causing bowel obstruction or strangulation. Premature infants have particularly high risk of inguinal hernia and incarceration. Management is elective surgical repair (herniorrhaphy), with urgency determined by age and incarceration risk. Incarcerated hernias require urgent reduction (often possible with adequate sedation and positioning) followed by repair within 24-48 hours. Panel A: Meckel's diverticulum anatomy showing location relative to ileocecal valve, omphalomesenteric duct remnant, ectopic gastric mucosa, and Meckel's scan uptake pattern. Panel B: Hirschsprung disease pathophysiology showing absent ganglion cells, functional obstruction, transition zone on contrast enema, and surgical pull-through concept. Panel C: Biliary atresia diagnostic pathway showing conjugated hyperbilirubinemia evaluation, ultrasound findings, HIDA scan, and Kasai portoenterostomy with timeline for optimal outcomes. Panel D: Inguinal hernia examination and management showing indirect hernia anatomy, reducible versus incarcerated presentations, and surgical repair indications. --- ### X. Functional GI Disorders Functional abdominal pain disorders represent the most common cause of chronic abdominal pain in children and adolescents, affecting 10-15% of school-age children. Rome IV criteria define functional abdominal pain as episodic or continuous abdominal pain at least 4 times per month for at least 2 months, not occurring only with physiologic events such as eating or menses, and not explained by another medical condition after appropriate evaluation. Subtypes include functional dyspepsia (pain or discomfort centered in the upper abdomen), irritable bowel syndrome (pain associated with defecation or change in stool frequency/form), abdominal migraine (episodic periumbilical pain with vasomotor symptoms and family history of migraine), and functional abdominal pain not otherwise specified. The biopsychosocial model explains symptom development through interaction of altered gut physiology (visceral hypersensitivity, dysmotility) with psychological factors (anxiety, depression, stress) and social influences (family, school). Evaluation of functional abdominal pain focuses on identifying red flags suggesting organic disease while avoiding excessive testing that reinforces illness behavior. Red flags warranting further investigation include involuntary weight loss, gastrointestinal blood loss, significant vomiting, chronic severe diarrhea, unexplained fever, family history of inflammatory bowel disease or celiac disease, and localized right upper or right lower quadrant pain. Physical examination should be thorough and reassuring when normal, including assessment of growth parameters and pubertal development. Limited laboratory testing in the absence of red flags may include complete blood count, inflammatory markers, celiac serology, and urinalysis. Extensive testing and subspecialty referrals should be avoided when history and examination suggest functional disorder, as they may increase parental anxiety and reinforce illness behavior. Management of functional abdominal pain requires a therapeutic alliance between provider, patient, and family built on validation, reassurance, and realistic goal-setting. The initial consultation should acknowledge that pain is real and significant while explaining the brain-gut interaction and how stress, anxiety, and attention affect symptom perception. Treatment goals focus on restoring normal function including school attendance, activities, and sleep rather than complete pain elimination. Dietary modifications may include regular meals, adequate fiber, and trial of low-FODMAP diet in irritable bowel syndrome. Psychological interventions including cognitive behavioral therapy and gut-directed hypnotherapy have the strongest evidence base for functional abdominal pain, addressing catastrophizing, developing coping strategies, and modifying pain responses. Cyclic vomiting syndrome represents a distinct functional gastrointestinal disorder characterized by recurrent, stereotypical episodes of intense nausea and vomiting separated by symptom-free intervals. Episodes typically last 24-48 hours and recur at regular intervals with similar timing, duration, and severity for individual patients. Associated features include pallor, lethargy, anorexia, and abdominal pain, with patients often identifying triggers including infections, stress, excitement, and certain foods. Strong association exists with personal or family history of migraine, and cyclic vomiting syndrome may represent a migraine variant. Management includes supportive care during episodes (intravenous fluids, antiemetics including ondansetron), abortive therapy at episode onset (sumatriptan in adolescents), and prophylactic medications (cyproheptadine, amitriptyline, propranolol) for patients with frequent or severe episodes. Panel A: Rome IV criteria for functional abdominal pain disorders with subtypes including functional dyspepsia, irritable bowel syndrome, abdominal migraine, and functional abdominal pain-not otherwise specified. Panel B: Biopsychosocial model diagram showing interaction between visceral hypersensitivity, psychological factors, and social/environmental influences in functional pain pathogenesis. Panel C: Red flags checklist distinguishing functional from organic abdominal pain with recommended limited workup when red flags are absent. Panel D: Cyclic vomiting syndrome timeline showing prodrome, emetic phase, recovery, and interepisodic wellness with management strategies for each phase. --- ## Summary - Abdominal pain evaluation requires age-based differential diagnosis and recognition of red flags including bilious vomiting, bloody stool, and peritoneal signs - Gastroenteritis is most commonly viral; oral rehydration therapy is the cornerstone of management, with IV fluids reserved for severe dehydration - Functional constipation requires disimpaction followed by maintenance polyethylene glycol and behavioral modifications continued for months - Physiologic GER in the happy spitter differs from pathologic GERD causing symptoms or complications requiring acid suppression - Appendicitis presents classically with periumbilical pain migrating to the right lower quadrant with anorexia and low-grade fever - Intussusception affects infants 6 months to 3 years with colicky pain and currant jelly stool; air enema reduction is first-line treatment - Bilious vomiting in a neonate represents malrotation with volvulus until proven otherwise and constitutes a surgical emergency - Pyloric stenosis presents at 2-8 weeks with projectile non-bilious vomiting and hypochloremic hypokalemic metabolic alkalosis - Inflammatory bowel disease includes Crohn's (transmural, skip lesions) and ulcerative colitis (mucosal, continuous from rectum) - Celiac disease diagnosis requires serologic testing (TTG-IgA) followed by intestinal biopsy; treatment is lifelong gluten-free diet --- ## Key Terms | Term | Definition | |------|------------| | Intussusception | Telescoping of one bowel segment into an adjacent segment, most commonly ileocolic | | Volvulus | Twisting of bowel around its mesentery causing obstruction and ischemia | | Pyloric stenosis | Hypertrophy of pyloric muscle causing gastric outlet obstruction in young infants | | FPIES | Food protein-induced enterocolitis syndrome causing delayed vomiting and potential shock | | Hirschsprung disease | Congenital absence of ganglion cells in distal colon causing functional obstruction | | Celiac disease | Immune-mediated enteropathy triggered by gluten causing villous atrophy | | Encopresis | Fecal soiling in a toilet-trained child, usually due to overflow incontinence | | Meckel's diverticulum | Remnant of omphalomesenteric duct, the most common congenital GI anomaly | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*