What are the concerns and next steps for a constipated patient with fever, fussiness, and spitting up?

Immediate Concerns and Next Steps for Infant with Constipation, Fever, and Fussiness

This infant requires urgent evaluation for urinary tract infection (UTI), which is the most critical concern given the constellation of fever, constipation, and fussiness—particularly if the infant has any history of prenatal urinary tract dilation or is under 2 months of age. 1

Primary Concern: Urinary Tract Infection

• Any child with known or suspected urinary tract abnormalities presenting with fever should be evaluated for UTI, as these infants are at highest risk for serious infection 1
• Even without known urinary abnormalities, constipation with fecal impaction can cause obstructive uropathy and subsequent UTI in infants and young children 2
• The combination of fever (101°F for 28 hours), fussiness, and difficulty with bowel movements raises concern for UTI as the primary diagnosis 1

Immediate Diagnostic Steps

Obtain a catheterized urine specimen immediately for:

• Urinalysis looking for bacteria and white blood cells 2
• Urine culture before starting any antibiotics 1
• A catheterized specimen is essential to minimize contamination and avoid over-treatment 1

Assess hydration status urgently:

• Check for signs of dehydration: tachycardia, decreased skin turgor, decreased urine output, altered mental status 3
• Evaluate for hemodynamic stability 3

Physical examination must focus on:

• Abdominal distention or masses suggesting severe constipation 3
• Signs of peritonitis or acute abdomen 1
• Rectal examination if indicated to assess for fecal impaction 2

Secondary Concern: Severe Constipation with Complications

• Constipation for 2-3 days with fever and fussiness could indicate developing complications such as fecal impaction causing urinary obstruction 2
• The "spitting up" may represent gastroesophageal reflux from increased intra-abdominal pressure or early signs of obstipation 3
• Fever with constipation is NOT typical and demands investigation for infectious causes rather than treating constipation alone 4

Management Algorithm

If UTI is Confirmed or Highly Suspected:

1. Start antimicrobial therapy immediately once urine culture is obtained, particularly if the infant shows any signs of sepsis 1
2. For infants with fever and suspected UTI, empiric antibiotics should not be delayed while awaiting culture results 1
3. Address the constipation simultaneously as it may be contributing to urinary obstruction 2
4. Consider imaging (renal ultrasound) if UTI is confirmed to evaluate for hydronephrosis or structural abnormalities 1

For Hydration Management:

• If mild-moderate dehydration is present, initiate oral rehydration solution at 10 mL/kg for ongoing losses 3
• Reserve IV fluids for severe dehydration, shock, or inability to tolerate oral intake 3
• Once hemodynamic stability is achieved, transition to maintenance fluids rather than continued boluses 5

For Constipation Management:

• Do NOT use laxatives until serious infection is excluded, as antimotility effects could worsen any underlying inflammatory process 3
• Avoid polyethylene glycol if the infant has nausea, bloating, or abdominal pain that is worsening, as these may indicate a serious condition 6
• Once infection is ruled out, gentle stool softeners may be appropriate

Critical Pitfalls to Avoid

• Do not attribute fever solely to constipation—this combination demands infectious workup 4, 2
• Do not delay urine culture while treating constipation first—UTI is the more immediately dangerous condition 1
• Do not use rectal stimulation or suppositories if there is concern for inflammatory bowel disease or infection, as this is a rare but serious presentation in infants 4
• Do not assume "spitting up" is benign reflux—in the context of fever and constipation, it may indicate systemic illness 3

Escalation Criteria for Hospitalization

Admit immediately if:

• Hemodynamic instability or signs of sepsis 3
• Inability to tolerate oral fluids 3
• Severe dehydration despite oral rehydration attempts 3
• Confirmed UTI in an infant, particularly if under 2 months old 1
• Suspected urinary obstruction on examination or imaging 2

Follow-up Imaging if UTI Confirmed

• Perform voiding cystourethrogram (VCUG) or contrast-enhanced voiding urosonography (ceVUS) to evaluate for vesicoureteral reflux 1
• Renal functional imaging should be deferred until 6-12 weeks of age if structural abnormalities are identified 1