Definition. Urinary tract infection (UTI) is the presence of pathogenic bacteria or fungus in the urinary tract with or without symptoms of infection. A definitive diagnosis is made by culture of any organism in a urine specimen that has been properly collected by suprapubic bladder aspiration (>10,000 col), ideally, or by gentle catheterization (>100,000 col).
Incidence. Various series report an incidence of 0.5–1.0% in term infants weighing >2500 g and higher rates (3–5%) in premature infants or infants weighing <2500 g. (Note: In the neonatal period, there is a greater incidence among males than females.) The predominant organisms are Gram-negative rods; Escherichia coli is the most common. In neonates, UTIs are most frequently acquired by hematogenous spread.
Pathophysiology. The three routes with which the urinary tract can become infected are retrograde ascent of fecal-perineal bacteria, introduction of bacteria into urinary system by instrumentation (eg, catheter insertion), or urinary tract involvement as part of a systemic infection (may see Gram-positive species). When a UTI is present in an infant <1 year of age, an associated urinary tract abnormality is found in ~50% of neonates. Associated anomalies that may give rise to a UTI include neurogenic bladder, posterior urethral valves, vesicoureteral reflux, and ureteropelvic junction obstruction.
Risk factors include indwelling urinary catheters, systemic sepsis with hematogenous seeding of the urinary tract, urinary tract obstruction, neurogenic bladder (myelodysplasia), and male newborns. Evidence suggests that uncircumcised males may be at higher risk for UTIs. Ritual (religious) circumcision performed by nonphysicians may be a risk factor for male UTI.
Signs of sepsis. The infant may have frank signs of sepsis (respiratory distress, apnea, bradycardia, hypoglycemia, or poor perfusion) or abdominal distention.
Nonspecific findings. The signs are often subtle and may include lethargy, irritability, poor feeding, vomiting, jaundice, or failure to thrive.
Urine culture. Suprapubic aspiration or bladder catheterization is mandatory for a dependable urine culture in a neonate. Some clinicians consider "bag" urine inadequate to achieve reliable culture results.
Blood cultures should be obtained before starting antibiotic therapy.
Urinalysis. Microscopic examination may show white blood cells, but the presence of bacteria is a more reliable sign of UTI in the neonate, especially when urine is collected by suprapubic aspiration.
The complete blood cell count may show leukocytosis.
Serum bilirubin may be elevated and increased bilirubin levels in neonates with an UTI are related to pathological findings (renal cortex changes) when technetium-99m DMSA renal scintigraphy is performed.
No other studies are indicated.
Initial antibiotic treatment. Initial antibiotic therapy usually consists of broad-spectrum intravenous antibiotics, usually ampicillin and gentamicin, or third-generation cephalosporins, until definitive urine and blood culture results are reported. (For dosages and other pharmacologic information, see Chapter 132.)
Further investigations. Further tests are necessary to rule out anatomic abnormalities in the neonate. Tests such as renal/bladder ultrasonography, contrast voiding cystourethrogram, and renal scan are indicated; at times, an intravenous pyelogram is required for complex problems. Urologic consultation is usually recommended.
Prognosis. Up to a one-fourth of infants can have a recurrent UTI within the first year of life. Effective use of long-term suppressive antibiotics (in the presence of vesicoureteral reflux) along with any indicated corrective surgery has dramatically reduced the long-term incidence of ...
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