How to manage a 16-year-old patient with abdominal and lower back pain, and a history of fever?

Management of a 16-Year-Old with Abdominal and Lower Back Pain and History of Fever

Obtain CT abdomen and pelvis with IV contrast immediately as the initial imaging study, as this is the preferred diagnostic approach for adolescents presenting with nonlocalized abdominal pain, back pain, and fever to identify serious intra-abdominal pathology including abscess, appendicitis, inflammatory bowel disease complications, or vascular causes. 1, 2

Immediate Diagnostic Workup

Initial Imaging

• CT abdomen and pelvis with IV contrast is the gold standard initial imaging for this presentation, as it changes the leading diagnosis in 49% of cases, alters admission status in 24%, and modifies surgical plans in 25% of patients with nontraumatic abdominal complaints 1
• CT with IV contrast specifically increases detection of cholecystitis/cholangitis by 100% and pelvic inflammatory disease by 280% compared to clinical assessment alone 1
• In patients with fever and abdominal pain, CT decreased abscess diagnosis by 19% (ruling out false positives) and decreased colitis/inflammatory bowel disease diagnosis by 12% after imaging 1

Critical Laboratory Tests

• Complete blood count (CBC) to assess for leukocytosis suggesting infection or inflammation 2
• C-reactive protein (CRP) has superior sensitivity and specificity compared to white blood cell count for identifying surgical disease 2
• Serum lactate to evaluate for mesenteric ischemia, though normal lactate does not exclude early ischemia 2
• Lipase and amylase to evaluate for pancreatitis, which commonly presents with back radiation 2
• Liver function tests and renal function tests to assess hepatobiliary and kidney pathology 2
• Blood cultures if fever is present, as bacteremia may indicate serious infection 3

Critical Red Flags Requiring Urgent Intervention

Vital Sign Abnormalities

• Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop 2, 3
• Fever ≥38°C combined with tachycardia ≥110 bpm indicates possible sepsis requiring immediate resuscitation 3
• Hypotension, respiratory distress with tachypnea, or decreased urine output indicate sepsis or peritonitis requiring immediate source control 3

Physical Examination Findings

• Abdominal rigidity suggests peritonitis requiring immediate surgical evaluation 3
• Pain out of proportion to physical examination should raise immediate suspicion for acute mesenteric ischemia, even with normal vitals 2
• Right lower quadrant tenderness with fever strongly suggests appendicitis 4

Differential Diagnosis Priority List

Life-Threatening Conditions to Rule Out First

• Appendicitis (including perforated appendicitis with abscess): Most common surgical emergency in this age group, with atypical presentations possible 1, 4, 5
• Intra-abdominal abscess: May present with fever, diffuse or localized abdominal pain, and back pain from retroperitoneal extension 1
• Inflammatory bowel disease complications (Crohn's disease with psoas abscess or perforation): Can present with fever, abdominal pain, back pain, and weight loss 5, 6
• Mesenteric ischemia: Pain out of proportion to examination findings, though rare in adolescents 2
• Mycotic aneurysm or vascular infection: Fever with back pain in 65-90% of cases, though more common in older adults 1

Other Important Considerations

• Pyelonephritis or complicated urinary tract infection: Can cause abdominal and back pain with fever 1
• Pancreatitis: Commonly radiates to the back 2
• Spinal epidural abscess: Presents with back pain, fever, and potentially neurological symptoms 7
• Systemic infections (including meningococcemia): Can present atypically with abdominal pain before classic signs develop 8
• Psoas abscess: Rare complication of Crohn's disease or hematogenous spread, presents with hip/back pain and fever 6

Management Algorithm After Imaging

If CT Shows Uncomplicated Appendicitis

• Proceed to appendectomy as the standard of care 1
• Alternatively, consider non-operative management with antibiotics in select cases, though surgery remains preferred in adolescents 1

If CT Shows Perforated Appendicitis with Abscess

• Small abscesses (<3-4 cm): Antibiotic therapy alone for 7 days 2
• Large abscesses: Percutaneous drainage combined with antibiotic therapy for 4 days, followed by interval appendectomy 2
• Use aminoglycoside-based combinations, carbapenems, piperacillin-tazobactam, or advanced-generation cephalosporins with metronidazole 4

If CT Shows Inflammatory Bowel Disease or Abscess

• Initiate broad-spectrum antibiotics for complicated intra-abdominal infection 4
• Consider percutaneous drainage for accessible abscesses 2
• Gastroenterology consultation for inflammatory bowel disease management 5

If CT Shows Diverticulitis (Rare in Adolescents)

• Conservative management without antibiotics may be appropriate in immunocompetent patients with uncomplicated disease 2
• Antibiotic therapy for no more than 7 days in immunocompromised patients 2

If CT is Negative or Inconclusive

• Consider MRI without or with IV contrast if clinical suspicion remains high, as it has sensitivity of 86-94% and specificity of 94% without radiation exposure 4
• Abdominal ultrasound can identify acalculous cholecystitis, liver or kidney abscesses, or appendicitis if not already performed 1
• Consider diagnostic laparoscopy if symptoms persist and imaging is inconclusive, as it has diagnostic accuracy between 86-100% 2

Special Considerations for Adolescents

Age-Specific Factors

• Adolescents may present with atypical symptoms, particularly if immunocompromised or if diagnosis is delayed 4
• Laboratory values may be normal despite serious infection, especially early in the disease course 3
• Weight loss, as mentioned in case reports, should raise suspicion for inflammatory bowel disease or chronic infection 5, 6

Pain Management

• Provide immediate pain relief without withholding medication while awaiting diagnosis, as pain control facilitates better physical examination without affecting diagnostic accuracy 4
• Use oral NSAIDs (ibuprofen) for mild-to-moderate pain if no contraindications exist 4
• For severe pain, use intravenous opioid analgesics titrated to effect 4

Common Pitfalls to Avoid

• Do not rely on absence of fever to exclude serious infection, as fever may be intermittent or absent early in the disease course 3, 5
• Do not delay imaging in favor of serial examinations when the presentation includes fever, back pain, and abdominal pain, as this combination warrants immediate investigation 1, 2
• Do not assume normal laboratory values exclude serious pathology, particularly in adolescents where inflammatory markers may lag behind clinical disease 3
• Do not withhold pain medication while awaiting diagnosis, as this outdated practice impairs examination quality and causes unnecessary suffering 4
• Do not miss spinal epidural abscess by focusing only on intra-abdominal pathology; if neurological symptoms develop or back pain is severe, obtain MRI of the spine 7

Antibiotic Therapy Guidelines

When to Initiate Antibiotics

• Reserve antibiotics for confirmed complicated intra-abdominal infections such as perforated appendicitis with abscess, confirmed inflammatory bowel disease complications, or identified bacterial infections 4
• Do not routinely prescribe broad-spectrum antibiotics when there is low suspicion of complicated infection 4

Antibiotic Regimens

• Acceptable regimens include aminoglycoside-based combinations, carbapenems, piperacillin-tazobactam, or advanced-generation cephalosporins with metronidazole 4
• Discontinue antibiotics within 24 hours if signs of infection resolve and source control is adequate 4
• Oral step-down options include second- or third-generation cephalosporins with metronidazole, or amoxicillin-clavulanate if organisms are susceptible 4

Follow-Up and Reassessment

• Instruct patient and family to return immediately if severe or progressive pain develops, fever persists beyond 48-72 hours of treatment, or new neurological symptoms appear 4
• Monitor for persistent fever, leukocytosis, or failure of symptoms to improve, as these indicate high risk of ongoing intra-abdominal infection requiring additional intervention 4
• If symptoms persist despite initial management and negative imaging, consider rare diagnoses such as systemic juvenile idiopathic arthritis or atypical infections based on travel history 5