What are the differential diagnoses for an 11-year-old patient with intermittent left lower abdominal pain that started while sitting, with no pain on palpation and stable vital signs?

Differential Diagnoses for 11-Year-Old with Intermittent Left Lower Abdominal Pain

In an 11-year-old with intermittent left lower abdominal pain, stable vitals, and no peritoneal signs, the most likely diagnoses are functional abdominal pain (most common at this age), constipation, early appendicitis (even with left-sided pain), mesenteric adenitis, and less commonly, ovarian pathology in females or early inflammatory bowel disease.

Primary Differential Diagnoses

Most Common Causes in This Age Group

• Functional abdominal pain is the leading diagnosis in school-age children, affecting approximately 10% of this population, particularly when examination is benign and vitals are stable 1
• Constipation should be strongly considered even without obvious history, as children may not report bowel patterns accurately and this commonly presents with intermittent lower abdominal pain 2
• Mesenteric adenitis (viral-associated lymph node inflammation) frequently mimics appendicitis but presents with less severe symptoms and no peritoneal signs 2

Critical "Cannot Miss" Diagnoses

• Appendicitis remains in the differential despite left-sided pain location—atypical presentations occur, and malrotation can place the appendix in unusual locations 3, 4

  • Classic presentation includes right lower quadrant tenderness, vomiting, and guarding, but early appendicitis may have minimal findings 4
  • Sensitivity of clinical diagnosis alone is only 87.1% by ultrasound and 90.8% by CT, meaning examination alone misses cases 4

• Intussusception should be considered in this age range, though more common in younger children, presenting with intermittent colicky pain 2

• Ovarian torsion or ovarian cyst (if female) can present with intermittent pain when torsion is incomplete or cyst is enlarging 5

Other Important Considerations

• Early inflammatory bowel disease (Crohn's disease) can present with intermittent abdominal pain before other symptoms develop 6
• Gastroenteritis or viral syndrome are common causes of mild, intermittent pain with stable vitals 2
• Urinary tract infection or nephrolithiasis should be excluded, as renal pathology can refer pain to lower abdomen 3
• Parasitic infections (giardiasis, ascariasis) remain important in certain populations, though frequency has decreased 1

Key Clinical Features to Elicit

History Elements That Change Management

• Pain characteristics: Colicky vs. constant, relation to meals, bowel movements, or position changes 1
• Last bowel movement and passage of gas: Absence suggests obstruction; constipation history has 85% sensitivity for predicting bowel-related pain 5
• Associated symptoms: Fever (even low-grade), vomiting, diarrhea, dysuria, or vaginal symptoms 2
• Menstrual history in females: Cyclical pain suggests gynecologic etiology 7
• Recent illness: Upper respiratory infection or pharyngitis suggests mesenteric adenitis 2
• Weight loss or chronic symptoms: Suggests organic disease like inflammatory bowel disease or malignancy 1

Physical Examination Red Flags

• Rebound tenderness or guarding: Even subtle findings increase probability of surgical pathology significantly 5
• Abdominal distension: Combined with pain suggests obstruction or significant pathology 5
• Rectal examination: May reveal occult blood or fecal impaction 1
• Pelvic examination (if appropriate): For sexually active females or when gynecologic pathology suspected 5

Diagnostic Approach

Initial Laboratory Testing

• Urinalysis: Essential to exclude urinary tract infection or nephrolithiasis 4
• Complete blood count: Leukocytosis >14,000 suggests infection or inflammation, though can be normal in early appendicitis 5, 4
• Pregnancy test in post-menarchal females: Mandatory before imaging 5

Imaging Strategy

• Ultrasound is the preferred initial imaging in pediatric patients when appendicitis or gynecologic pathology is suspected, with 87.1% sensitivity and 89.2% specificity for appendicitis 4

  • Advantages: No radiation, can evaluate ovaries/appendix, operator-dependent but excellent in experienced hands 4

• CT abdomen/pelvis with IV contrast should be reserved for cases where ultrasound is non-diagnostic or high suspicion remains, with 90.8% sensitivity and 94.2% specificity 4

  • The American College of Radiology emphasizes that CT alters diagnosis in nearly 50% of cases with nonlocalized pain 3

• Plain radiographs have very limited utility but may identify constipation, free air, or bowel obstruction patterns 5, 4

Management Algorithm

Immediate Actions for Stable Patient

• Serial examinations are critical—accuracy increases significantly with repeated assessments over 4-6 hours 5, 4
• Nothing by mouth if surgical pathology suspected until definitive diagnosis 2
• Pain control: Analgesia should NOT be withheld, as it does not mask surgical findings and improves patient cooperation with examination 2

Indications for Immediate Surgical Consultation

• Fever with inability to pass gas or stool 8
• Severe tenderness with guarding or rebound 8
• Abdominal distension with peritoneal signs 5
• Bloody stools or signs of shock 8

Observation vs. Discharge Criteria

• Safe for discharge: Improving or stable pain, tolerating oral intake, reliable follow-up, no red flags 6
• Requires observation: Equivocal findings, moderate pain, inability to exclude surgical pathology, unreliable follow-up 2
• Requires admission: Any peritoneal signs, persistent vomiting, inability to tolerate oral intake, confirmed surgical pathology 6, 2

Common Pitfalls to Avoid

• Do not dismiss left-sided pain as non-appendiceal: Malrotation and atypical presentations occur, and clinical diagnosis alone has 34-68% misdiagnosis rate 3, 4
• Do not assume functional pain without adequate evaluation: Organic causes are found in 30-40% of children with recurrent abdominal pain in some series 1
• Do not order CT reflexively: Start with ultrasound in pediatric patients to minimize radiation exposure 4
• Do not withhold analgesia: Pain control improves diagnostic accuracy and does not mask surgical findings 2
• Do not miss gynecologic pathology in females: Always consider ovarian torsion, which requires urgent intervention 5