Urinary tract infections account for the majority of serious bacterial infections affecting infants. The prevalence of urinary tract infection in female infants is slightly higher than in boys. The leading cause of urinary tract infection in infants is vesicoureteral reflux, the passage of urine from the bladder back up into the kidneys. Infants with urinary tract infections need to be evaluated for the presence of vesicoureteral reflux to avoid long-term kidney damage.
General Signs
Female infants with urinary tract infections usually have nonspecific general symptoms. Fever, defined as a rectal temperature higher than 100.4 degrees Fahrenheit, is usually present. Some infants will instead have hypothermia, or low body temperature, or temperature instability, with fluctuations in the core body temperature. Infants with urinary tract infection are also irritable, hard to console and have feeding difficulty. They may spit up more than usual or experience frank vomiting. Some infants will have pain when urinating or during diaper changes.
Female infants with urinary tract infection can also be jaundiced (yellowish tinge of the skin) and have poor weight gain or failure to thrive.
Urine Signs
Female infants with urinary tract infections can have strong-smelling urine. This could be both from the presence of the bacteria causing the infection or from dehydration. Occasionally, infants have blood in the urine, which is usually noticed during diaper changes. When the urine is examined under the microscope, you can see white blood cells, which are the cells that fight infection. Other elements of the urine analysis in female infants with urinary tract infections include the presence of nitrites, which are breakdown products of bacterial metabolites, an indirect indication of presence of bacteria in the urine.
Abdominal Signs
If the urinary tract infection is caused by a congenital obstruction of the urinary tract, patients may have swelling of the bladder, which expands if the urine cannot flow out. This manifests itself as a round mass in the lower abdomen. If the obstruction is higher in the urinary tract, swelling of the kidneys will appear as a mass in the lower back or flank.
