abd-pain

Acute abdominal pain in children

Key points

Common presentation: Abdominal pain accounts for a substantial proportion of pediatric ED visits and is often due to self-limited conditions (e.g., gastroenteritis, constipation, viral illnesses).
High-stakes diagnoses: A subset of children have time-sensitive surgical or medical emergencies that require rapid recognition and intervention.
Diagnostic challenge: Infants and young children are at higher risk for delayed diagnosis and complications because of limited history, atypical presentations, and rapid clinical deterioration.
Broad differential: Etiologies span surgical, medical, extra-abdominal, systemic, and functional causes; a structured approach is essential.

Major etiologic categories

Acute surgical conditions
- Appendicitis
- Intussusception
- Malrotation with volvulus
- Strangulated or incarcerated hernia
- Trauma to solid organs (liver, spleen, kidney) or hollow viscus
Intra-abdominal, non-surgical conditions
- Gastroenteritis
- Constipation
- Urinary tract infection
- Peptic or gastric ulcer disease
- Gastroesophageal reflux disease
- Mesenteric adenitis
Extra-abdominal conditions
- Pneumonia (especially lower lobe)
- Streptococcal or viral pharyngitis
- Otitis media (in younger children)
- Contusions or strain of abdominal wall musculature or soft tissue
Systemic illnesses
- Viral syndromes
- Sepsis
- Diabetic ketoacidosis
- Hematologic/oncologic disease (e.g., leukemia, lymphoma, sickle cell vaso-occlusive crisis)
- Henoch–Schönlein purpura and other vasculitides
Functional and chronic pain syndromes
- Functional abdominal pain disorders
- Abdominal migraine
- Irritable bowel syndrome

Clinical priority: Maintain a low threshold to consider “acute abdomen” (e.g., appendicitis, volvulus, perforation, peritonitis) and to escalate evaluation when red flags are present (toxic appearance, peritoneal signs, bilious emesis, GI bleeding, severe localized pain, or hemodynamic instability).

Pathophysiology of abdominal pain in children

Neural pathways of pain

Visceral pain
- Dull, crampy, or aching pain arising from distention, ischemia, or inflammation of a hollow or solid viscus.
- Afferent impulses travel via autonomic fibers to the spinal cord; fibers are bilateral and overlapping, leading to poor localization.
- Typically perceived in midline regions: epigastric, periumbilical, or suprapubic areas.
- Common early presentation of appendicitis, gastroenteritis, constipation, or mesenteric ischemia before parietal involvement.
Somatic (parietal) pain
- Sharp, well-localized pain arising from irritation of the parietal peritoneum, abdominal wall musculature, or skin.
- Carried by somatic nerves (T6–L1) unilaterally to the spinal cord.
- Develops when an intra-abdominal process (e.g., appendicitis, perforated ulcer, cholecystitis) inflames the parietal peritoneum.
- Associated with guarding, rebound, and peritoneal signs; localization often corresponds to the involved quadrant.
Referred pain
- Pain perceived at a site distant from the diseased organ due to convergence of afferent fibers at the spinal cord or higher centers.
- May be sharp and localized or vague and aching.
- Examples: shoulder pain from diaphragmatic irritation; abdominal pain with lower lobe pneumonia or testicular torsion.

Modifying factors and clinical variability

Pain perception: Children vary widely in pain tolerance and expression; severe pathology (e.g., appendiceal abscess) may present with surprisingly mild reported pain, whereas functional pain can appear disproportionally severe.
Age-related differences: Infants and toddlers may present with nonspecific signs (irritability, poor feeding, lethargy) rather than localized pain or classic peritoneal findings.
Non-neurophysiologic associations: Some conditions (e.g., tonsillitis with high fever, viral syndromes, streptococcal pharyngitis) frequently present with abdominal pain despite incomplete neurophysiologic explanation.

Exam implications

Always think beyond the abdomen: Because extra-abdominal and systemic illnesses commonly manifest as abdominal pain, the physical exam must extend beyond the abdomen.
Minimum exam elements in a child with abdominal pain
- Oropharynx (tonsillitis, pharyngitis)
- Lungs (pneumonia, especially lower lobes)
- Skin (rash, purpura, trauma, bruising)
- Genitourinary system (testes, hernia exam, pelvic exam when appropriate)
- Back and costovertebral angles (renal pathology, trauma)
Reassessment: Serial abdominal exams are critical, as pain character may evolve from visceral to somatic with disease progression (e.g., early to late appendicitis).

Table 1: Differential Diagnosis by Age

Age Group	Common	Less Common	Rare / Very Uncommon
< 2 years	Colic (<3 months) GERD Acute gastroenteritis Viral syndromes Constipation UTI Trauma (accidental or non‑accidental) Sickle cell disease	Trauma (possible child abuse) Intussusception Incarcerated hernia Meckel diverticulum Milk protein allergy Nephrotic syndrome Peptic ulcer disease Cystic fibrosis (meconium ileus) Pneumonia, asthma	Appendicitis Volvulus (malrotation) Malignancy (e.g., Wilms tumor) Heavy metal toxicity (lead) Malabsorptive syndromes Choledochal cyst Hemolytic anemia Porphyria
2–5 years	Acute gastroenteritis Pneumonia, asthma Constipation UTI Appendicitis Sickle cell disease Viral syndromes Trauma	Henoch–Schönlein purpura Intussusception Testicular torsion Cystic fibrosis Toxin ingestion Collagen vascular disease Inflammatory bowel disease	Incarcerated hernia Neoplasm Renal calculi Rheumatic fever Hepatitis Meconium ileus (late) Recurrent intussusception
6–12 years	Acute gastroenteritis Appendicitis UTI Constipation Functional abdominal pain Trauma GERD Sickle cell disease	Inflammatory bowel disease Cholecystitis / pancreatitis Testicular torsion Collagen vascular disease Toxin ingestion Diabetes mellitus (DKA) Hepatitis	Rheumatic fever Heavy metal toxicity Malignancy Abdominal abscess Ovarian torsion
> 12 years	Acute gastroenteritis Appendicitis Colitis GERD UTI Dysmenorrhea Mittelschmerz Epididymitis Lactose intolerance Sickle cell disease Trauma	Pelvic inflammatory disease Ectopic pregnancy Ovarian torsion Testicular torsion Cholecystitis / pancreatitis Renal calculi Inflammatory bowel disease Hepatitis Toxin ingestion	Rheumatic fever Malignancy Abdominal abscess Porphyria Intussusception (rare in teens)

Age Group	Abdominal Life-Threatening Causes	Extra‑Abdominal Life-Threatening Causes
< 2 years	Malrotation with volvulus Intussusception Trauma (including possible child abuse) Incarcerated hernia Hirschsprung disease (toxic megacolon) Necrotizing enterocolitis (late presentation possible) Severe gastroenteritis with dehydration/shock Peritonitis (primary or secondary) Meckel diverticulum (bleeding or obstruction) Appendicitis (rare but possible and often severe) Malignancy (e.g., Wilms tumor)	Myocarditis / pericarditis Sepsis Hemolytic uremic syndrome Metabolic acidosis from inborn errors of metabolism Toxic ingestion / overdose
2–5 years	Intussusception Appendicitis Incarcerated hernia Meckel diverticulum Peptic ulcer disease (bleeding or perforation) Peritonitis (primary or secondary) Trauma Megacolon (from inflammatory bowel disease)	Sepsis Hemolytic uremic syndrome Myocarditis / pericarditis Collagen vascular disease (vasculitis with abdominal involvement) Toxic ingestion / overdose Diabetic ketoacidosis (less common but possible)
6–12 years	Appendicitis Trauma Peptic ulcer disease (bleeding or perforation) Peritonitis Cholecystitis / pancreatitis Megacolon (IBD) Obstruction from prior abdominal surgery Aortic aneurysm (rare but reported)	Sepsis Myocarditis / pericarditis Diabetic ketoacidosis Hemolytic uremic syndrome Collagen vascular disease Toxic ingestion / overdose
> 12 years	Ectopic pregnancy Appendicitis Trauma Peptic ulcer disease (bleeding or perforation) Peritonitis Cholecystitis / pancreatitis Intra‑abdominal abscess (PID, appendicitis, IBD, cholecystitis) Aortic aneurysm Acute fulminant hepatitis	Drug overdose / substance toxicity Diabetic ketoacidosis Sepsis Myocarditis / pericarditis Collagen vascular disease Hemolytic uremic syndrome

Table 3 Red Flags & actions

Red‑Flag Symptom / Sign	Possible Life‑Threatening Etiologies	Immediate Actions / Priorities
Bilious vomiting	Malrotation with volvulus High‑grade bowel obstruction Intestinal atresia (infants)	Immediate surgical consult NG tube decompression IV fluids, resuscitation STAT abdominal imaging (upper GI series preferred for volvulus)
Severe, sudden‑onset abdominal pain	Volvulus Ovarian or testicular torsion Perforated viscus Ruptured ectopic pregnancy (>12 yrs) Pancreatitis	Rapid assessment of perfusion STAT ultrasound or CT depending on suspected cause Immediate surgical or gynecologic consult
Abdominal distention with vomiting	Obstruction (mechanical or functional) Hirschsprung disease (toxic megacolon) Peritonitis Sepsis	NG tube decompression Broad‑spectrum antibiotics if peritonitis suspected Urgent imaging
Bloody stool or hematemesis	Intussusception Meckel diverticulum Hemolytic uremic syndrome Peptic ulcer disease (bleeding) Inflammatory bowel disease flare	Type & screen, CBC, coagulation panel IV fluids Urgent ultrasound for intussusception GI or surgical consult
Fever with severe abdominal pain	Appendicitis (complicated) Peritonitis Cholecystitis / cholangitis Pyelonephritis Sepsis	Broad‑spectrum antibiotics Blood/urine cultures Imaging based on suspected source
Localized RLQ pain with guarding	Appendicitis Ovarian torsion (right‑sided) Mesenteric ischemia (rare)	Ultrasound first‑line Surgical consult if high suspicion
Severe abdominal pain out of proportion to exam	Mesenteric ischemia (rare in children) Sickle cell vaso‑occlusive crisis DKA Toxic ingestion	Immediate labs (CBC, CMP, lactate, ketones) Consider toxicology screening Rapid resuscitation
Syncope, hypotension, or shock	Hemorrhage (GI bleed, ectopic pregnancy) Sepsis Myocarditis / pericarditis Adrenal crisis	Immediate IV access and fluid resuscitation POC glucose STAT ECG Consider bedside ultrasound
Testicular or scrotal pain	Testicular torsion Incarcerated inguinal hernia	Immediate urologic or surgical consult Do not delay for imaging if high suspicion
Pelvic pain with vaginal bleeding (post‑menarchal)	Ectopic pregnancy Ovarian torsion PID with tubo‑ovarian abscess	Pregnancy test immediately Pelvic ultrasound Gynecology consult

Differential Diagnosis & Evaluation of Acute Abdominal Pain in Children

Major Diagnostic Categories

Traumatic intra‑abdominal injury – solid organ laceration, hollow viscus perforation, mesenteric injury
Obstructive conditions – malrotation with volvulus, intussusception, incarcerated hernia, adhesions
Inflammatory / infectious – appendicitis, peritonitis, gastroenteritis, IBD, cholecystitis, pancreatitis
Genitourinary – UTI, pyelonephritis, nephrolithiasis, testicular torsion, ovarian torsion
Systemic / metabolic – DKA, HUS, sickle cell crisis, vasculitis (HSP), myocarditis/pericarditis
Functional / chronic – constipation, functional abdominal pain, dietary intolerance
Gynecologic (post‑menarchal) – PID, ectopic pregnancy, ovarian torsion, TOA

Key Age‑Specific Diagnoses

Neonates < 2 months
- Malrotation with volvulus (bilious emesis)
- Necrotizing enterocolitis
- Hirschsprung disease
Infants 2 months – 2 years
- Intussusception (colicky pain; late finding: currant jelly stool)
- Trauma (including non‑accidental injury)
- Severe gastroenteritis with dehydration
Children > 5 years
- Appendicitis (most common surgical cause)
- IBD (Crohn disease more common than UC)
- Cholecystitis (hemolytic anemia, CF, adolescents)
Adolescents
- PID, tubo‑ovarian abscess
- Ectopic pregnancy
- Ovarian torsion
- Substance ingestion / overdose

Important Diagnoses to Consider

Trauma‑Related

Solid organ injury (liver, spleen, kidney)
Hollow viscus perforation
Mesenteric injury
Child abuse – always ask specifically about trauma

Obstructive Conditions

Adhesive bowel obstruction (post‑surgical)
Malrotation with volvulus (bilious emesis in neonates)
Intussusception (2 months–2 years)
Incarcerated inguinal hernia

Inflammatory / Infectious

Appendicitis – may lack classic migration of pain
Primary bacterial peritonitis (nephrotic syndrome, liver failure)
Gastroenteritis (viral most common)
Streptococcal pharyngitis
Lobar pneumonia
UTI / pyelonephritis
Intra‑abdominal abscess (post‑appendicitis)

Gastrointestinal / Chronic Conditions

Inflammatory bowel disease (Crohn > UC)
Cholecystitis (hemolytic anemia, CF, adolescents)
Pancreatitis
Dietary protein allergy (infants)
Malabsorption syndromes

Extra‑Abdominal Causes

Incarcerated inguinal hernia
Myocarditis / pericarditis
DKA
Hemolytic uremic syndrome
Henoch–Schönlein purpura (HSP)
Sickle cell vaso‑occlusive crisis
Testicular torsion
Urolithiasis
Toxic ingestions (lead, iron, etc.)

Functional Abdominal Pain

Diagnosis of exclusion
Pain rarely occurs during sleep
No association with meals or activity
Normal growth and development
Exam typically normal or mild mid‑abdominal tenderness

Gynecologic (Post‑Menarchal)

PID with tubo‑ovarian abscess
Ruptured ectopic pregnancy
Ovarian torsion
Consider ectopic pregnancy in all reproductive‑age females

Evaluation & Decision‑Making Priorities

Stabilize the seriously ill child
- Airway, breathing, circulation
- Shock and cardiorespiratory disease may present as abdominal pain
Identify children needing immediate surgical intervention
- Traumatic injury
- Appendicitis
- Intussusception
- Volvulus or other obstructive lesions
Diagnose medical conditions requiring urgent non‑operative management
- DKA
- HUS
- Sepsis
- Severe gastroenteritis
- Pyelonephritis
Consider self‑limited or nonspecific causes
- Viral gastroenteritis
- Constipation
- Functional abdominal pain

Clinical Presentation	Recommended Laboratory Tests	Recommended Imaging
Suspected Appendicitis	CBC with differential CRP ± ESR Urinalysis (rule out UTI) Pregnancy test (post‑menarchal females)	Ultrasound (first‑line) CT abdomen/pelvis if US nondiagnostic and suspicion remains high MRI (preferred alternative to CT when available)
Bilious Vomiting (neonate/infant)	CBC, CMP Lactate Blood gas	STAT Upper GI series (gold standard for volvulus) Abdominal X‑ray (initial screen for obstruction/perforation) Ultrasound (adjunct for pyloric stenosis or intussusception)
Intermittent colicky pain ± bloody stool (Intussusception)	CBC Electrolytes Type & screen if unstable or bloody stool	Ultrasound (diagnostic test of choice) Air or contrast enema (diagnostic + therapeutic)
Abdominal Trauma	CBC Liver enzymes (AST/ALT) Amylase/lipase Urinalysis (renal injury) Type & screen	FAST exam (initial) CT abdomen/pelvis with contrast (hemodynamically stable) Chest X‑ray (if thoracic injury suspected)
Fever + abdominal/flank pain (UTI / Pyelonephritis)	Urinalysis & urine culture CBC CRP	Renal/bladder ultrasound (if severe, recurrent, or atypical) CT only if concern for abscess or obstruction
Vomiting + abdominal pain + polyuria/polydipsia (DKA)	POC glucose Venous blood gas Serum ketones (β‑hydroxybutyrate) CMP (electrolytes, anion gap) UA (ketonuria)	Imaging not routinely required Head CT only if concern for cerebral edema
Abdominal pain + purpuric rash (HSP)	CBC CMP UA (renal involvement) Stool guaiac	Ultrasound (intussusception risk)
Epigastric pain radiating to back (Pancreatitis)	Lipase (preferred) Amylase CMP Triglycerides	Ultrasound (first‑line) CT abdomen if unclear or severe
Pelvic pain (adolescent female)	Pregnancy test (mandatory) CBC CRP GC/CT testing if PID suspected	Pelvic ultrasound (transabdominal ± transvaginal) Doppler if torsion suspected
Acute scrotal pain (Testicular torsion)	Labs not required before intervention	Scrotal ultrasound with Doppler (if diagnosis uncertain) Do not delay surgery if high suspicion
Vomiting + diarrhea (Gastroenteritis)	None routinely required Electrolytes if dehydrated Stool studies if bloody stool, severe illness, or travel exposure	Imaging not indicated unless red flags present

Recommended Labs & Imaging by Clinical Presentation

Clinical Presentation	Recommended Laboratory Tests	Recommended Imaging
Abdominal Pain After Trauma “Children with localized and/or acute pain after blunt trauma may appear surprisingly well yet have significant solid organ or hollow viscus trauma.”	CBC Liver enzymes (AST/ALT) Amylase/lipase Urinalysis (renal injury) Type & screen	CT abdomen/pelvis with contrast (gold standard in stable patients) FAST exam (screening only; low sensitivity for solid organ injury) Chest X‑ray if thoracic injury suspected
Vomiting + Prior Abdominal Surgery / Suspected Obstruction “A child who has had prior abdominal surgery…should have abdominal radiographs…to evaluate for obstruction.”	CBC Electrolytes Lactate (if concern for ischemia)	Abdominal X‑ray (flat & upright) Ultrasound if intussusception suspected Upper GI series if malrotation suspected
Peritoneal Signs (rebound, guarding, rigidity) “Rebound tenderness…or guarding suggests peritoneal inflammation.”	CBC CMP Lactate Blood cultures if febrile	Ultrasound (appendicitis, cholecystitis, abscess) CT abdomen/pelvis if diagnosis unclear Abdominal X‑ray if perforation suspected
Suspected Appendicitis “Ultrasound can be used to confirm the diagnosis…CT has excellent test characteristics…MRI has similar test characteristics without radiation.”	CBC with differential CRP ± ESR Urinalysis Pregnancy test (post‑menarchal females)	Ultrasound (first‑line) MRI (preferred alternative to CT) CT abdomen/pelvis if US nondiagnostic
Colicky Pain ± Bloody Stool (Intussusception) “A patient with episodic colicky pain…should raise suspicion for intussusception.”	CBC Electrolytes Type & screen if unstable or bleeding	Ultrasound (diagnostic test of choice) Air‑contrast enema (diagnostic + therapeutic) Abdominal X‑ray if obstruction suspected
Neonate with Distention + Emesis (NEC) “In neonates…abdominal tenderness with distention…should raise suspicion for necrotizing enterocolitis.”	CBC CMP Lactate Blood cultures	Abdominal X‑ray (pneumatosis, portal venous gas) Ultrasound (adjunct)
Flank Pain / Hematuria (Urolithiasis or Pyelonephritis) “Focal tenderness in the flank region suggests pyelonephritis or urolithiasis.”	Urinalysis & urine culture CBC CMP	Renal/bladder ultrasound CT (non‑contrast) if stones suspected and US nondiagnostic
Acute Pelvic Pain (Adolescent Female) “Pregnancy and complications of pregnancy must be considered…a urine β‑hCG should be obtained.”	Pregnancy test (mandatory) CBC CRP GC/CT testing if PID suspected	Pelvic ultrasound (transabdominal ± transvaginal) Doppler if torsion suspected
Abdominal Pain + Polyuria/Polydipsia (DKA) “Polydipsia with polyuria may suggest…diabetes mellitus with abdominal pain from ketoacidosis.”	POC glucose Venous blood gas Serum ketones CMP UA	No routine imaging Head CT only if concern for cerebral edema
Fever + Abdominal Pain (Possible Pneumonia) “Localized…breath sounds or crackles suggest pneumonia…not an uncommon cause of abdominal pain.”	CBC Consider viral testing	Chest X‑ray
Suspected Constipation “A palpable mass…is sometimes appreciated…radiography should be reserved for obstruction or if diagnosis is in doubt.”	No routine labs	Abdominal X‑ray only if obstruction suspected

“Don’t‑Miss” Imaging Guide for Pediatric Abdominal Pain

Clinical Red Flag	Imaging That MUST Be Obtained	Rationale
Bilious vomiting (any age, especially neonates)	STAT Upper GI series (gold standard for volvulus) Abdominal X‑ray (initial screen)	Rule out malrotation with volvulus Time‑sensitive risk of midgut ischemia
Significant abdominal trauma	CT abdomen/pelvis with contrast (stable patients) FAST exam (adjunct only)	Detect solid organ injury (liver, spleen) Identify hollow viscus perforation
Colicky pain ± bloody stool (suspected intussusception)	Ultrasound (diagnostic test of choice) Air‑contrast enema (diagnostic + therapeutic)	Risk of bowel ischemia and perforation Enema can reduce obstruction immediately
Localized RLQ pain with peritoneal signs	Ultrasound (first‑line) MRI if US nondiagnostic CT only if necessary	Appendicitis is the most common surgical emergency Delayed diagnosis increases perforation risk
Acute scrotal pain (suspected testicular torsion)	Scrotal ultrasound with Doppler	Testicular salvage depends on rapid diagnosis Do NOT delay surgery if high suspicion
Sudden severe lower abdominal pain (suspected ovarian torsion)	Pelvic ultrasound with Doppler	Ovarian viability decreases with time
Pelvic pain + positive pregnancy test	Pelvic ultrasound (transabdominal ± transvaginal)	Rule out ectopic pregnancy Life‑threatening hemorrhage risk
Neonate with distention + emesis (suspected NEC)	Abdominal X‑ray (pneumatosis, portal venous gas) Ultrasound (adjunct)	Rapid progression to perforation and sepsis
Severe distention + vomiting (suspected obstruction)	Abdominal X‑ray (initial) Upper GI series if malrotation suspected Ultrasound if intussusception suspected	Rule out volvulus, incarcerated hernia, adhesions
Fever + abdominal pain + respiratory findings	Chest X‑ray	Pneumonia is a common extra‑abdominal cause of abdominal pain

Flowchart

Rapid Bedside Decision‑Making Flowchart for Pediatric Abdominal Pain

START: Child with Acute Abdominal Pain
Rapid assessment of appearance, vitals, hydration, and perfusion.

⬇

Step 1 — ABCs & Shock Assessment

Airway compromise
Respiratory distress
Hypotension, tachycardia, altered mental status

→ Immediate resuscitation (IV access, fluids, glucose, oxygen).

⬇

Step 2 — Red Flags Present?

Bilious vomiting
Peritoneal signs (rebound, guarding, rigidity)
Severe sudden pain
Bloody stool or hematemesis
Testicular or pelvic pain
History of trauma
Fever + focal tenderness

If YES → Immediate imaging pathway below

⬇

Step 3 — Imaging Pathway (Based on Presentation)

Bilious vomiting → STAT Upper GI series
Trauma → CT abdomen/pelvis with contrast
RLQ pain → Ultrasound (appendicitis)
Colicky pain → Ultrasound ± Air enema (intussusception)
Pelvic pain (female) → Pelvic ultrasound
Scrotal pain → Doppler ultrasound
Fever + cough → Chest X‑ray

⬇

Step 4 — Surgical Emergency?

Volvulus
Intussusception (not reducible)
Appendicitis with peritonitis
Incarcerated hernia
Testicular or ovarian torsion
Ruptured ectopic pregnancy

→ Immediate surgical or specialty consultation

⬇

Step 5 — Medical Emergencies?

DKA
HUS
Sepsis
Pyelonephritis
Myocarditis / pericarditis
HSP with GI involvement

→ Targeted labs + urgent medical management

⬇

Step 6 — Likely Benign / Self‑Limited Causes

Viral gastroenteritis
Constipation
Functional abdominal pain
Mesenteric adenitis

→ Supportive care, reassessment, return precautions

⬇

Step 7 — Reassess Frequently
Pain character may evolve (e.g., visceral → somatic). Serial abdominal exams are essential.