UTI is associated with multiplication of organisms in the urinary tract defined as the presence of more than 100.000 organism per ml. in the midstream urine sample OR presence of any organism from suprapubic puncture sample of urine.
The prevalence of UTI varies markedly with age and sex. In the first year of life it is more common in male with a male to female ratio of 2.8:1 while in other age groups it is much more common in females reaching a ratio of 1:10.
In girls UTIs often occur at the onset of toilet training because of voiding dysfunction that occurs at this age. The child is trying to retain the urine to stay dry, yet the bladder may have uninhibited contractions forcing urine out, the result may be high pressure turbulent urine flow or incomplete bladder emptying, both of which increase the likelihood of bateruria. Voiding dysfunction may occur in the toilet trained child who void infrequently.
Obstructive uropathy, urethral instrumentation, anatomic abnormalities, vesicoureteral reflux and neuropathic bladder increase the risk of UTI. Other risk factors include: pinworm infestation, constipation, uncircumcised male, wiping from back to front, tight under wear, and bubble bath. P- fimbriated bacteria are more likely to cause pyelonephritis.
The diagnosis depends on the culture of bacteria from the urine, so every effort should be made to get a reliable sample.
In toilet trained children midstream urine sample (MSU) sample is satisfactory, in uncircumcised male the prepuce must be retracted. For MSU sample colony count is used to differentiate between infected and contaminated specimens. In infants and young children the application of adhesive, sealed sterile collection bag after disinfection of the skin of the genitalia can be useful, specially if culture results were negative. When significant growth result is obtained greater assurance as to possibility of UTI is needed. A catheter specimen or suprapubic sample should be obtained from the bladder to confirm the diagnosis.
A urinalysis should be done on the same sample that is cultured. Pyuria suggest infection, but infection can occur in the absence of pyuria and pyuria can be present without UTI. Microscopic hematuria may be present. Cast in the urine sediment suggest renal involvement. Proteus infection produces alkaline PH of urine.
Leukocytosis and neutrophilia are common with acute pyelonephritis. Serum creatinine elevates transiently in 30% of infants with renal infection. Blood culture is positive when sepsis complicates renal infection.
A renal US should be obtained to rule out obstructive uropathy, malformations, cysts, urolithiasis, and perinephric abscess.
A voiding cystourethrogaphy is indicated in all children younger than 5 year with UTI, any child with febrile UTI, any male with UTI, and school aged girls with two or more UTIs. The most common finding is vesicoureteral reflux which is found in 40% of patients. US is insensitive in detecting reflux. Only 40% of children with reflux have abnormality on US.
IF vesicouteteral reflux is present a Tc99 DMSA scan is performed to assess the presence of renal scarring.
Acute cystitis should be treated promptly to prevent it’s possible progression to pyelonephritis. A urine sample is obtained and treatment started immediately if symptoms are severe. Trimethoprim-sulfamethoxazole, Amoxycillin, and Nitrofuantoin are good initial treatment and effective against most strains of E.coli and Klebsiella.
In acute febrile illness suggesting pyelonephritis the use of broad spectrum antibiotic capable of reaching significant tissue level is preferable like Ceftriaxone or Ampicillin + Gentamicin.
Treatment may be changed according to the result of culture and their sensativity.
A urine culture should be obtained one week after the termination of antibiotic to assure that urine remain sterile. Follow up urine cultures should be obtained every three months interval for one – two year when the child is asymptomatic.
If recurrences are frequent, prophylaxis therapy against reinfection is often effective using either Cotrimoxazole or Nitrofurantoin at 1/3 the usual therapeutic dose once daily. Urine cultures should be obtained to detect break through infection by resistant organisms.
Antibacterial prophylaxis is also indicated in: 1. Vesicoureteral reflux. 2. Neurogenic bladder. 3. Obstruction. 4. Calculi.
The long term prognosis of UTI is excellent provided prompt and adequate treatment is instituted when the diagnosis is established.