What is the diagnosis and treatment for an 8-year-old with hip and back pain, fever, and urinalysis showing leukocytes, nitrites, ketonuria, hematuria, and proteinuria?

Acute Pyelonephritis with Possible Musculoskeletal Involvement

This 8-year-old requires immediate empiric antibiotic therapy for acute pyelonephritis and urgent imaging to rule out spinal infection, given the combination of fever, back/hip pain, and urinalysis findings consistent with upper urinary tract infection.

Diagnosis

Primary Diagnosis: Acute Pyelonephritis

• The urinalysis findings of leukocytes, nitrites, hematuria (+3 blood), and proteinuria in a febrile child strongly indicate acute pyelonephritis rather than simple cystitis 1
• Pyelonephritis typically presents with systemic symptoms including high fever, malaise, vomiting, abdominal or flank pain, and tenderness—this child's back and hip pain fit this pattern 1
• The presence of both leukocytes and nitrites increases specificity to 96% for urinary tract infection 2
• Ketonuria (+3) suggests decreased oral intake or metabolic stress from infection 1

Critical Differential: Spinal Infection (Discitis/Osteomyelitis)

• Back pain with fever in children aged 2-12 years mandates consideration of vertebral osteomyelitis or discitis, which commonly presents with persistent pain, low-grade fever, decreased range of motion, and localized tenderness 1
• Hip pain in this context may represent referred pain from the spine or concurrent septic arthritis 1
• Spine infections in children often present with limping, irritability, and nighttime pain 1
• Laboratory values typically show leukocytosis, elevated ESR, and elevated CRP 1

Immediate Management

Obtain Urine Culture Before Antibiotics

• Collect a catheterized urine specimen for culture and antimicrobial susceptibility testing before initiating antibiotics 1
• Culture is mandatory in all cases of suspected pyelonephritis to guide definitive therapy 1
• UTI is confirmed by ≥50,000 CFU/mL of a single pathogen in catheterized specimens 1

Laboratory Evaluation

• Complete blood count with manual differential to assess for leukocytosis, bandemia, or left shift 1
• Blood cultures if the child appears septic or has rigors 1
• ESR and CRP to evaluate for inflammatory/infectious processes including spinal infection 1
• Basic metabolic panel to assess renal function and hydration status 1

Urgent Imaging Required

MRI of the spine with and without contrast is the imaging modality of choice when spinal infection is suspected in a child with back pain and fever 1

• MRI has increased sensitivity for detecting marrow edema, soft tissue pathology, and early osteomyelitis/discitis 1
• Contrast enhancement is helpful in evaluating infection, inflammation, or tumor 1
• Plain radiographs of the spine should be obtained first but have limited sensitivity for early infection 1
• Renal ultrasound should be performed to evaluate for hydronephrosis, abscess, or anatomic abnormalities 1

Empiric Antibiotic Therapy

First-Line Treatment for Pyelonephritis

Initiate empiric therapy with either a fluoroquinolone or third-generation cephalosporin immediately after obtaining cultures 1

• Oral cephalosporins (e.g., cefixime) or fluoroquinolones (if local resistance patterns allow) are recommended for outpatient management 1
• If the child appears toxic, has persistent vomiting, or cannot tolerate oral intake, hospitalize and administer IV ceftriaxone (50-75 mg/kg/day, max 2g) or gentamicin (5-7 mg/kg/day) 1, 3
• E. coli accounts for approximately 75% of pediatric UTIs 4, 5
• Treatment duration is typically 7-14 days for pyelonephritis 1

Antibiotic Considerations

• Nitrofurantoin and fosfomycin should be avoided for pyelonephritis as they achieve insufficient tissue concentrations 1
• The absence of nitrite does not exclude UTI—only 3% of nitrite-negative UTIs are caused by Enterococcus, so routine empiric coverage is unnecessary 4
• Adjust antibiotics based on culture results and clinical response within 48-72 hours 1

Follow-Up and Monitoring

Clinical Response Assessment

• If fever persists beyond 72 hours of appropriate antibiotic therapy, obtain contrast-enhanced CT or MRI to evaluate for renal abscess, obstruction, or alternative diagnosis 1
• Immediate imaging is warranted if clinical deterioration occurs 1
• Repeat urinalysis and culture if symptoms recur or persist 1

Post-Treatment Imaging

• Renal ultrasound should be performed after treatment to detect anatomic abnormalities, hydronephrosis, or scarring 1
• VCUG is NOT routinely indicated after first UTI but should be performed if ultrasound shows hydronephrosis, scarring, or if febrile UTI recurs 1
• Renal scarring occurs in approximately 15% of children after first pyelonephritis episode 1

Long-Term Considerations

• Instruct parents to seek prompt evaluation (within 48 hours) for any future febrile illnesses to detect recurrent UTI early 1
• Prophylactic antibiotics are NOT routinely recommended after first UTI unless high-grade vesicoureteral reflux is identified 1
• Children with bilateral renal scarring are at highest risk for renal insufficiency and hypertension 1

Critical Pitfalls to Avoid

• Do not delay imaging if spinal infection is suspected—early MRI is essential as delayed diagnosis can lead to catastrophic neurologic consequences 1
• Do not treat based on urinalysis alone without obtaining culture in a febrile child 1, 2
• Do not assume back pain is musculoskeletal in a febrile child—spine infections are common between ages 2-12 years 1
• Do not use oral antibiotics if the child is vomiting, appears septic, or has signs of dehydration 1
• Do not perform VCUG routinely after first UTI—reserve for recurrent infections or abnormal ultrasound findings 1