24 Ö. Aydogdu and C. Radmayr

3.4  Classification

1.Urinary tract infections can be classified according to either number of episodes (first episode or recurrent) or severity (simple or severe).2, 14

2.Recurrent UTIs may be due to unresolved infection, bacterial persistence or reinfection.5, 15

3.Recurrent UTI (any of the following)14, 16

•Two or more episodes of UTI with acute pyelonephritis (APN) or upper UTI.

•One episode of UTI with APN or upper UTI plus one or more episode of UTI with cystitis or lower UTI.

•Three or more episodes of UTI with cystitis or lower UTI.

4.Severe and simple forms UTI should be differentiated clinically (Table 3.1) to decide the degree of urgency with which diagnostic tool and treatment are to be under­ taken.

3.5  Signs and Symptoms

Signs and symptoms suggestive of UTI include;

1.Non-specific symptoms, such as irritability, lethargy, malaise, vomiting, diarrhea, failure to thrive, poor feeding, jaundice (especially in infants).16, 17

2.In the first weeks of life, 13.6% of patients with fever have a UTI.17

TABLE 3.1.  Clinical classification of UTIs in children.

Simple UTI

Mild pyrexia

Good fluid intake

Not or slightly dehydrated

Good expected level of compliance

Taken from EAU guidelines, update March 2009

3.Specific symptoms include dysuria, frequency, hesitancy, urgency, small-volume voids, hematuria, cloudy urine and suprapubic, lumbar or abdominal pain with or without

fever.2, 14, 16

4.Unusual odor of the urine is generally not helpful in predicting UTI.15, 16

5.Other conditions, such as acute urethritis and vulvovaginitis may mimic UTI symptoms.14, 16

The presenting symptoms of UTI may differ according to the anatomic site of the infection.14-17

1.Fever, nausea, vomiting and lumbar pain may be observed in upper UTI.

2.A lower UTI generally presents with symptoms such as dysuria, frequency, urgency and sometimes urinary incontinence.

3.The only way to correctly differentiate upper and lower urinary tract infection is performing a DMSA scan at the time of diagnosis. However this is not needed in most of the cases.18, 19

3.6  Diagnosis

A complete history and physical examination of the patient are just as critical in the evaluation of the patient with suspected UTI as the laboratory tests.

1.Physical examination

•Physical examination should be the first step and may be alone enough to discover underlying pathology.

•Clinician should be cautious for phimosis, signs of pyelonephritis or epididymo-orchitis, labial adhesion and congenital abnormalities (e.g., stigmata of spina bifida).

•Fever may or may not exist with aforementioned signs.

2.Laboratory tests

•Diagnosis of a suspected UTI is based on the examination of the urine.14, 16, 19

•Most investigators define a UTI as the presence of organisms in the urine combined with signs and symptoms of UTI in the patient.2, 18, 19

26Ö. Aydogdu and C. Radmayr

A.Method of urine collection

•The technique of obtaining urine for urinalysis or culture affects the rate of contamination and thus influences the interpretation of the result.

•The diagnostic threshold depends on the method of urine collection.20-22

•In older, toilet-trained children who can void on command, the use of clean catch, especially the midstream urine, after carefully retracting the foreskin and cleaning the glans penis in boys and spreading the labia and cleaning the periurethral area in girls was found to be an acceptable technique for obtaining urine.22

•Some studies have compared the results of cultures of urine obtained by both clean catch and catheterization. As a result it was reported that clean voided specimens had similar rates of contamination to those obtained by catheterization.20, 22

•For urine collection from infants and young children, suprapubic aspiration or transurethral catheterization should be preferred.19, 20

•Prospective studies proved that collection from bags or pads had a high incidence of false positive predictive value.21, 22

•Urine collection from a bag is helpful when the culture result is negative and has a positive predictive value of 15%.21, 22

B.Urinalysis: microscopic examination/dipstick analysis

•There is a need for a more rapid determination of the probability of the presence of a UTI to guide the clinician in the decision to treat empirically while waiting for the culture result.19, 23, 24

•The most frequent markers are nitrite and leukocyte esterase usually combined in a dipstick test.

•Combination of the presence of leukocyte esterase and nitrite is highly predictive of a positive urine culture.24

•Nitrite is the degradation product of the nitrates of bacterial­ metabolism, particularly of gramnegative bacteria.22, 24

•Clinician should realize that many gram-positive cocci does not produce nitrites and may yield a false-negative result.

•The nitrite test has a sensitivity of 45–60%, and a specificity of 85–98%.20, 24

•Leukocyte esterase is produced by the activity of leukocytes.

•Leukocyte esterase test has a sensitivity of 48–86% and a specificity of 17–93%.20, 24

•In patients who have a negative dipstick and microscopic analysis, especially if there is an alternative source of fever, further urine culture is generally not necessary.

•If the tests are positive, it is better to confirm the results in combination with the clinical symptoms and urine culture.

•Bacteriuria without pyuria may be found when urine is collected before the onset of the inflammatory reaction, in bacterial contamination and colonization.19, 24

•Pyuria without bacteriuria may be due to incomplete treatment, urolithiasis or foreign bodies in the urinary tract and infections caused by

Mycobacterium tuberculosis or Chlamydia trachomatis.19, 24

•Either bacteriuria or pyuria may not be considered reliable parameters to diagnose or exclude UTI.

•In a febrile child with both bacteriuria and pyuria (the findings of ³10 WBC/mm3 and ³50,000 cfu/mL in an urine specimen), the possibility of UTI increases significantly.17, 24

C.Urine culture

•Culture of the urine remains the gold standard for the diagnosis of the UTIs.20-23