Acute Abdomen in Infants and Children

Eva Ilse Rubio, MD

DIFFERENTIAL DIAGNOSIS

Common

Appendicitis
Inguinal Hernia
Midgut Volvulus
Intussusception
Adhesions
Crohn Disease

Less Common

Ovarian Torsion
Pelvic Inflammatory Disease
Ectopic Pregnancy
Meckel Diverticulum
Nonaccidental Trauma/Child Abuse
Henoch-Schönlein Purpura
Foreign Body Ingestion

Rare but Important

Gastric Volvulus
Wandering Spleen

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Gender
Bilious emesis vs. nonbilious emesis
Presence or absence of bowel obstruction
If bowel obstruction, proximal or distal
Skin: Rash or bruising

Helpful Clues for Common Diagnoses

Appendicitis
- Fever, leukocytosis, anorexia are expected but none are universal
- Radiograph
  - Findings range from right lower quadrant air-fluid levels to frank small bowel obstruction
  - Useful for excluding free air
- US
  - Noncompressible tubular structure > 7 mm in diameter
  - In children, may obviate CT and avoid radiation
  - Pitfall: Must see entire length of appendix to exclude tip appendicitis
- CT
  - Hyperemic walls, inflammatory stranding in fat
Inguinal Hernia
- Radiograph may demonstrate loops of bowel in scrotal sac
- US: Peristalsing bowel within scrotal sac
Midgut Volvulus
- With midgut malrotation
  - Typical presentation in neonate with bilious emesis but may present at any age
  - Usually a proximal obstruction
- Without midgut malrotation
  - Lead points include adhesions, Meckel diverticulum, or other abdominal lesions
  - Proximal or distal obstruction
Intussusception
- Radiographs (notoriously unreliable) may suggest intussusception with rounded soft tissue density
- US sensitive and specific for ileocolic intussusception
  - Bowel and mesenteric fat trapped within colon create “doughnut” sign if seen in transverse plane
Adhesions
- Presents as partial, complete, or intermittent bowel obstruction
- Adhesions not seen but transition point from dilated to collapsed bowel may be identified on CT
Crohn Disease
- Marked bowel wall thickening, often with skip areas
- Perirectal inflammation/abscess easily missed on imaging

Helpful Clues for Less Common Diagnoses

Ovarian Torsion
- US: Torsed ovary is generally large, heterogeneous, predominantly hypoechoic
  - Pitfall: Blood flow on US may confound diagnosis due to intermittent torsion or multiplicity of blood supply to ovaries
- Obvious size/volume discrepancy between ovaries is virtually always present
  - In postmenarchal patient, torsed ovarian volume often > 20 mL
  - In premenarchal patient, ovarian volumes markedly discrepant, but torsed ovarian volume may be < 20 mL
- Consider underlying ovarian mass or cyst
Pelvic Inflammatory Disease
- Early PID shows nonspecific inflammatory changes
- Tuboovarian abscess may be seen with US or CT
Ectopic Pregnancy
- Look for extrauterine gestational sac
- If ruptured, appears as complex cystic/solid mass with echogenic peritoneal fluid
Meckel Diverticulum
- May present as bleeding, intussusception, or bowel obstruction
- CT: Small bowel obstruction, inflammatory changes around bowel loops, hyperemic tubular structure
Nonaccidental Trauma/Child Abuse
- Abdomen CT obtained when laboratory values are abnormal (liver, pancreatic enzymes, CK-MB)
  - Abdomen CT: Duodenal hematoma, jejunal perforation, liver laceration, pancreatic laceration, pericardial effusion
  - Scrutinize images for fractures
- Rectal prolapse is uncommon but known presentation
Henoch-Schönlein Purpura
- Small vessel vasculitis
- Acute abdominal findings may precede rash, arthralgia, hematuria
- CT findings may prompt clinical consideration
  - Marked bowel wall thickening predominantly in jejunum and ileum, with skip areas
  - Intussusception, ascites
  - Mesenteric lymphadenopathy and vascular engorgement
Foreign Body Ingestion
- May cause perforation, erosion, obstruction
- Multiple magnets retain attraction to each other, cause pressure erosion, perforation

Helpful Clues for Rare Diagnoses

Gastric Volvulus
- Radiograph: Large spherical gastric bubble
- Fluoroscopic upper gastrointestinal (UGI) study considered definitive
- Mesenteroaxial gastric volvulus
  - Stomach folds and twists
  - Higher association with vascular compromise and obstruction in children
  - Pylorus near/above gastroesophageal junction
  - May be associated with congenital diaphragmatic or abdominal abnormalities
- Organoaxial gastric volvulus
  - Stomach flips upside down
  - Lower likelihood of vascular compromise or acute obstruction in children
  - Greater curvature above lesser curvature; downward pointing pylorus
- Mixed mesenteroaxial/organoaxial
Wandering Spleen
- Spleen absent from usual position in left upper quadrant due to lax or absent splenic ligaments
  - Risk of torsion of long vascular pedicle
  - Higher risk of injury in minor accidents when not protected by thoracic cage

Image Gallery

Frontal radiograph shows a nonspecific bowel gas pattern with air-fluid levels

, hinting at trouble in the right lower quadrant. Note the patient is bending slightly, splinting from pain.

Axial CECT of the same patient shows a dilated hyperemic tubular structure

and lamellated appendicolith in the right lower quadrant, consistent with acute appendicitis.

(Left) Longitudinal ultrasound shows an elongated dilated noncompressible tubular structure

in the right lower quadrant. (Right) Axial CECT shows diffuse severe bowel wall thickening

, free fluid

, flattened IVC, and small caliber aorta

in a 3 year old with perforated appendicitis who presented in septic shock with abdominal compartment syndrome. The patient survived after multiple abdominal washouts.

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