Residency · Residency · Medicine-Pediatrics

Acute Abdomen: Surgical Decision-Making in Children and Adults

Introduction

The acute abdomen is a common clinical scenario requiring rapid assessment and decision-making. The differential diagnosis varies significantly by age, and the med-peds physician must recognize age-specific surgical emergencies while avoiding unnecessary interventions. This lecture covers the systematic approach to abdominal pain from infancy through adulthood with emphasis on surgical versus medical management.

Age-Specific Differential Diagnosis

Neonates (0-28 days)

Necrotizing enterocolitis (NEC): Primarily in premature infants; feeding intolerance, bloody stools, pneumatosis intestinalis. Malrotation with midgut volvulus: Bilious emesis is a surgical emergency until proven otherwise. Hirschsprung disease: Failure to pass meconium in first 48 hours. Intestinal atresia.

Infants (1-12 months)

Intussusception: Colicky pain, currant jelly stools, sausage-shaped mass; peak 6-36 months. Incarcerated inguinal hernia. Pyloric stenosis: Projectile nonbilious vomiting at 3-6 weeks.

Children (1-12 years)

Appendicitis: Most common surgical emergency in children. Meckel diverticulum: Painless rectal bleeding, or may present like appendicitis; Mesenteric lymphadenitis; Constipation (most common cause of abdominal pain in children).

Adolescents and Adults

Appendicitis: Remains most common surgical emergency. Cholecystitis and cholelithiasis; Small bowel obstruction (adhesive disease, hernias); Perforated peptic ulcer; Diverticulitis (typically age >40); Ovarian torsion, ectopic pregnancy (reproductive-age females); Mesenteric ischemia (elderly; "pain out of proportion to exam").

Clinical Assessment

History

Onset, location, character, radiation, severity of pain; Associated symptoms: vomiting (bilious vs. nonbilious), fever, diarrhea, anorexia. Last bowel movement, urinary symptoms; Menstrual history and pregnancy status in reproductive-age females; Surgical history (adhesive obstruction risk).

Physical Examination

Inspection: Distension, visible peristalsis, surgical scars. Auscultation: Absent bowel sounds (ileus/peritonitis), high-pitched tinkling (obstruction) Palpation: Rebound tenderness, guarding, rigidity (peritoneal signs) Special signs: McBurney point tenderness, Rovsing sign, psoas sign, obturator sign (appendicitis); Murphy sign (cholecystitis) Pediatric considerations: Exam may be unreliable in young children; observe gait, positioning, and facial expressions.

Red Flags Requiring Urgent Surgical Consultation

Bilious vomiting in a neonate (malrotation until proven otherwise); Peritoneal signs (rigid abdomen, rebound, guarding); Hemodynamic instability with abdominal pain; Evidence of bowel ischemia or perforation on imaging; Signs of incarcerated hernia.

Diagnostic Workup

Laboratory Studies

CBC with differential, CRP; BMP, lipase, liver function tests; Urinalysis (rule out UTI, nephrolithiasis); Beta-hCG in all reproductive-age females; Lactate if mesenteric ischemia or sepsis is suspected; Type and screen if surgical intervention anticipated.

Imaging

Pediatric principle: Ultrasound first to minimize radiation (ALARA principle) Adult principle: CT with IV contrast is the workhorse for acute abdominal imaging.

Appendicitis: The Prototype Surgical Emergency

Pediatric Appendicitis

Perforation rate higher in young children (up to 80% in children <5 years) Atypical presentations common in young children. Pediatric Appendicitis Score (PAS) or Alvarado Score for risk stratification. Ultrasound first; CT if US is equivocal. Appendectomy (laparoscopic) is standard treatment. Non-operative management with antibiotics is an emerging option for uncomplicated cases.

Adult Appendicitis

Classic presentation: periumbilical pain migrating to RLQ, anorexia, fever. Alvarado score or AIR score for risk stratification. CT abdomen/pelvis with IV contrast is the primary imaging modality. Laparoscopic appendectomy remains standard of care. CODA trial: Antibiotics alone are a reasonable alternative for uncomplicated appendicitis in adults.

Surgical Decision-Making Principles

Operate early when clinical and imaging findings are clear. Observe and reassess when diagnosis is uncertain; serial abdominal exams are valuable. Avoid unnecessary surgery in conditions managed medically (mesenteric lymphadenitis, constipation, pancreatitis) Understand the role of interventional radiology for percutaneous drainage of abscesses. Multidisciplinary communication between surgery, radiology, and primary team is essential.

Clinical Pearls

Bilious vomiting in a neonate is malrotation with volvulus until proven otherwise; this is a true surgical emergency. Ultrasound is the first-line imaging modality for pediatric abdominal pain; limit CT use to minimize radiation exposure. Always obtain a pregnancy test in reproductive-age females with abdominal pain before any imaging or intervention. Perforated appendicitis rates are highest in the very young and the elderly due to delayed or atypical presentations. The med-peds physician should maintain a low threshold for surgical consultation when peritoneal signs are present, regardless of age.

References

1. CODA Collaborative. A randomized trial comparing antibiotics with appendectomy for appendicitis. N Engl J Med. 2020;383(20):1907-1919.
2. Kharbanda AB, Vazquez-Benitez G, Ballard DW, et al. Development and validation of a novel pediatric appendicitis risk calculator (pARC). Pediatrics. 2018;141(4):e20172699.
3. Di Saverio S, Podda M, De Simone B, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg. 2020;15(1):27.
4. Leung AK, Sigalet DL. Acute abdominal pain in children. Am Fam Physician. 2003;67(11):2321-2326.

For the intern

At 3am, prioritize ensuring hemodynamic stability and identifying true surgical emergencies. Check vitals, perform a focused abdominal exam looking for peritoneal signs, obtain labs (including beta-hCG in reproductive-age females), and get appropriate imaging—ultrasound first in children, CT in adults for most indications. Call surgery immediately for bilious vomiting in neonates, peritoneal signs with guarding/rigidity, or hemodynamic instability. Serial exams over 4-6 hours are powerful when the diagnosis is unclear. Most other workup—including risk scores, subspecialty consultation for medical causes, and definitive management discussions—can wait until morning rounds when the attending team is available.

Common pitfalls

• Forgetting pregnancy testing before imaging or offering pain control in reproductive-age females—always check beta-hCG first to avoid missing ectopic pregnancy or causing fetal harm
• Over-relying on labs like white blood cell count; appendicitis and other surgical emergencies can occur with normal laboratory values, especially early in presentation
• Delaying surgical consultation when peritoneal signs are present—rigid abdomen with rebound and guarding requires immediate surgical evaluation regardless of imaging availability
• Ordering CT in children without first attempting ultrasound; radiation exposure is cumulative and should follow ALARA principles whenever diagnostic alternatives exist

Make it stick

You’re picking up a new patient on rounds, a 4-year-old with abdominal pain. Your resident asks you to formulate your initial thoughts on whether this might be surgical. You recall a lecture on acute abdomen. You remember that for children, appendicitis is the most common surgical emergency, but also that young children often present atypically, and may progress to perforation faster than adults. You’d also check for intussusception (colicky pain, currant jelly stools) and incarcerated hernia. You’d get an ultrasound, not a CT, as your first imaging choice. You would also specifically look for peritoneal signs (guarding, rigidity, rebound tenderness), which would be a red flag regardless of age, and call your surgery team.

If you remember one thing

Recognize age-specific surgical emergencies, with a low threshold for surgical consultation when peritoneal signs are present. Prioritize ultrasound for imaging in children to minimize radiation exposure.

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