INTRODUCTION — The procedures for obtaining and processing urine samples in infants and children are reviewed here. The diagnosis, treatment, and subsequent evaluation of urinary tract infections in neonates, infants, and older children are discussed separately:
●(See "Urinary tract infections in neonates".)
●(See "Urinary tract infections in children: Long-term management and prevention".)
INDICATIONS — The likelihood of a urinary tract infection (UTI) varies significantly in the pediatric population according to age, sex, circumcision status in males, presence of urologic abnormalities, and presenting signs and symptoms (table 1). Although clinicians may have variable thresholds for diagnostic testing, urine samples for urinalysis (dipstick and microscopic examination) and culture are generally indicated when the probability of a UTI is greater than 2 percent. UTICalc can be used to determine the probability of UTI in febrile (temperature ≥38°C [100.4°F]) children aged 2 through 23 months according to clinical characteristic. (See "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis", section on 'Decision to obtain urine sample'.)
UTIs are an important cause of acute and chronic morbidity in children. Long-term complications include hypertension and decreased renal function caused by renal scarring. The accurate diagnosis of UTI in children is necessary to ensure appropriate therapy and follow-up for those who need it, and to avoid unnecessary therapy, hospital admission, and further evaluation in those who do not. The manner in which urine is collected and processed before it is cultured can affect the validity of the culture result. (See "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis", section on 'Urine culture'.)
SELECTION OF TECHNIQUE — The technique for urine collection is primarily determined by whether the patient is toilet trained or not. In infants and children who are not toilet trained, transurethral bladder catheterization is the most commonly performed technique. However, suprapubic aspiration is least likely to result in a contaminated urine culture.
Toilet trained — Children who are toilet trained can provide clean voided urine samples for urine dipstick, urinalysis, and urine culture. (See 'Clean voided samples' below.)
Not toilet trained
Specimen for urine culture — Based upon observational studies, the relative rates of urine culture contamination by method of collection are as follows:
●Suprapubic aspiration (SPA) – 1 percent [1]
●Transurethral bladder catheterization (TUBC) – 6 to 12 percent [1-4]
●Clean catch voided urine (stimulation technique or bag specimen) – 16 to 63 percent [1-5]
We recommend that infants and children with a suspected urinary tract infection (UTI), who are not toilet trained and who are ill enough to merit antimicrobial therapy, have urine cultures obtained by TUBC or SPA rather than by clean catch or clean urine bag specimen [6,7]. We usually perform TUBC in our patients. Although specimen contamination is more likely by TUBC than by SPA [1,3,6,8], urine is also more likely to be obtained by TUBC [9,10]. Contamination of urine obtained by TUBC can be decreased by discarding the initial stream and culturing the subsequent urine stream during catheterization [6,11]. Many physicians and parents/caregivers also prefer TUBC because they view SPA as much more invasive and painful [6]. (See 'Transurethral bladder catheterization' below.)
SPA performed by a trained clinician is recommended for sterilely obtaining a urine culture in at least selected circumstances: uncircumcised boys with a tight phimosis or some girls with labial adhesions. While invasive and potentially painful, it represents the gold standard in the diagnosis of UTI because of the low likelihood of urine specimen contamination (approximately 1 percent) [1,6,12-14]. (See 'Suprapubic aspiration' below.)
The practice of obtaining urine specimens by the "clean voided" bag appeals to clinicians and parents/caregivers because it is noninvasive. However, bag urines should not be routinely used to obtain urine samples for culture, especially in situations where contamination of the specimen will complicate further management (eg, young infants or ill-appearing patients who warrant empiric parenteral antibiotics) because contamination occurs in up to two-thirds of specimens [1,3,6].
Bag urine samples may occasionally have a role for collection in well-appearing older infants and children in settings where urine catheterization is not frequently performed or when the caregiver is reluctant to have the child undergo urinary catheterization. In these situations, a negative urine culture result avoids bladder catheterization. However, given the high likelihood of bacterial growth, close follow-up with the patient needs to be assured and any growth on a bag specimen culture requires collection of a catheterized sample. Thus, presumptive antibiotic treatment should be avoided when a bag specimen is obtained. Any positive culture should be carefully interpreted in light of the individual clinical context and simultaneous urinalysis (if available).
Although use of clean voided urine samples for urine culture have been described in infants younger than six months of age, we do not recommend it because the technique has low yield (specimen obtained in about half of patients) and a contamination rate of 16 percent [2]. It was also most successful in infants younger than 90 days of age in whom rapid and more definitive identification of a UTI is needed.
Specimen for urine dipstick or urinalysis — Catheterization or SPA is also the preferred method of urine collection for dipstick and microscopic examination of the urine in infants and young children who are not toilet-trained [6,15].
However, preliminary evidence suggests that a bag urine for a screening urine dipstick and/or urinalysis may prevent the need for a catheterized urine culture in selected patients older than 6 months of age at low risk for a UTI [6,16-18]. In an observational study of over 800 previously healthy, well-appearing children 6 to 24 months of age presenting to a pediatric emergency department for evaluation of fever, screening of urine obtained by a bag specimen reduced the number of subsequent urine cultures obtained by TUBC from 63 to 30 percent during the course of the study without prolonging length of stay or increasing rates of revisits or missed UTI [18]. Follow-up for missed UTI in children who screened negative was only definitely known for 39 percent of patients. If a negative dipstick for leukocytes and nitrites on a bag urine specimen is used to forego urine culture, then close follow-up is needed to assure that fever resolves and no further signs of UTI develop because a negative urinalysis does not exclude a UTI (table 2). (See "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis", section on 'Diagnostic criteria'.)
Using matched urine specimens from 60 infants younger than 90 days of age, urine obtained by the bladder stimulation technique had similar accuracy for detecting a UTI and similar rates of specimen contamination when compared with urine obtained by bladder catheterization [19]. However, because of the importance of timely detection of a UTI in younger infants, and because the bladder stimulation technique is successful in only about half of patients, bladder catheterization is the recommended technique to acquire urine from infants six months of age and younger.
Urine screening with a bag specimen is not recommended for children with urinary tract abnormalities, recent genitourinary tract surgery, immune deficiency, neurogenic bladder, ill-appearing children, or children who require antibiotics immediately after the urine specimen is collected.
Furthermore, an infant or young child should not receive antibiotics on the basis of a positive urine dipstick or urinalysis (table 2) from a clean catch or voided bag urine specimen because of the high rates of urine culture contamination associated with these methods. For example, up to 85 percent of positive cultures from bag urine specimens represent false-positive results [20]. Positive urine screening from a voided or bag urine sample warrant another urine sample for urinalysis and culture collected by TUBC or SPA. (See "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis", section on 'Rapidly available tests'.)
TECHNIQUES
Clean voided samples — In toilet trained children, we suggest using the following technique to collect clean voided urine samples for urine culture:
●For girls, the labia should be spread, and the perineum cleansed two to three times with non-foaming antiseptic solution or mild soap. In postmenarcheal girls who are menstruating, a tampon can be inserted prior to specimen collection if the patient agrees.
●For boys, the meatus should be cleansed in a similar fashion. The foreskin should be retracted before cleansing for those who are uncircumcised. Cleansing the perineum with soap prior to urine collection may decrease the rate of contamination [21].
●Contact of the urinary stream with the mucosa can be minimized by retracting the foreskin in boys who are uncircumcised and by spreading the labia in girls during urination.
●The child should urinate into a toilet or urinal. Midway through urination, a specimen should be collected in a sterile container.
●For uncircumcised males, ensure that the foreskin is reduced to its normal position so that a paraphimosis does not develop. (See "Paraphimosis: Clinical manifestations, diagnosis, and treatment", section on 'Definition'.)
Although not routinely recommended for obtaining urine cultures because of high rates of contamination [4,6,22], several methods have been described for the collection of clean voided urine samples in infants and children who are not toilet-trained and may permit urine sampling for other testing:
●Bag specimen – For infants and children six months of age and older, the genitalia and perineum are broadly cleaned with an antiseptic solution (eg, povidone iodine) and a urine bag is applied by removing the backing from the adhesive and applying it over the vulva or penis and scrotum. The bag is regularly monitored and removed once urination has occurred.
●Bladder stimulation technique – For infants younger than six months of age, urine can be obtained by clean catch in approximately half of patients using the following method [2,23,24]:
•Allow the infant to feed for up to 20 minutes.
•Clean the genitalia with an antiseptic (eg, povidone-iodine solution).
•Have an assistant or the parent/caregiver suspend the infant under the arms (legs dangling in males or hip flexed in females).
•Have another assistant hold the sterile urine cup below the patient in preparation to catch the urine.
•Alternatively, gently tap over the bladder approximately 100 times per minute for 30 seconds followed by paravertebral massage for 30 seconds until urination occurs, up to a maximum of 5 minutes.
●Stimulation of the suprapubic region with cold fluid (Quick-Wee method) – With this method, the clinician applies cold liquid (eg, saline-soaked gauze) to the suprapubic region for up to five minutes. In one trial that compared this method to standard clean-catch collection using no stimulation in infants younger than 12 months of age, suprapubic stimulation resulted in a significantly higher rate of voiding [25]. However, urine was obtained in a minority of patients in both groups and contamination occurred in about one quarter of urine specimens obtained by suprapubic stimulation. Thus, use of this method for urine culture is strongly discouraged.
Transurethral bladder catheterization — The catheterization of the urethra is another safe and effective method for obtaining urine samples for culture in most infants and children who are not toilet trained. Based upon observational studies, sample collection is successful in 72 to 100 percent of patients [9,10]. The success rate of transurethral bladder catheterization (TUBC) is increased by the use of point-of-care ultrasonography [26].
●Preparation – An explanation of the anatomy and the indications for the procedure should be given to parents and caregivers before TUBC is performed to avoid unnecessary parental anxiety about the manipulation of their child's genitalia. In addition, the examiner should ensure use of latex-free catheters, especially in children with spina bifida and other conditions that require frequent bladder catheterization.
If available, point-of-care ultrasound easily identifies the presence of urine in the bladder and helps to improve the success rate of TUBC [26,27].
Topical lidocaine does not appear efficacious for pain relief in infants and young children during bladder catheterization, and we do not routinely use it. In a metaanalysis of four trials (almost 350 children younger than 4 years of age), there was no significant difference in pain reduction for urethral catheterization when comparing lidocaine gel to nonanesthetic lubricant [28]. In children older than 4 years of age one small trial of 20 patients suggests a modest pain reduction with lidocaine gel [29]. However, larger trials are needed to confirm this finding.
●Technique:
•The child is restrained in the supine and frog leg position. This position permits adequate stabilization of the pelvis and complete visualization of the external genitalia.
•The anterior urethra is cleansed thoroughly with an antiseptic (eg, povidone-iodine solution).
•A sterile lubricant jelly is applied to the end of an appropriately sized catheter (5 French for children younger than six months; 8 French for those between six months and adolescence, and 10 French for adolescents) and the catheter is passed through the urethra and into the bladder as follows:
•Boys:
-The foreskin of the glans is retracted gently to permit complete visualization of the urethral meatus if the boy is uncircumcised.
-The urethra is straightened by using the nondominant hand to hold the penis perpendicular to the lower abdomen (figure 1). Gentle traction is applied.
-The catheter is inserted with the dominant hand until urine returns.
-As the catheter is being advanced, it can be palpated along the posterior aspect of the penis. Resistance may be encountered near the base of the penis due to contraction of the external bladder sphincter. This can generally be overcome by maintaining traction on the penis, while applying gentle pressure with the catheter. The catheter should never be forced [30].
-For uncircumcised males, ensure that the foreskin is reduced to its normal position so that a paraphimosis does not develop. (See "Paraphimosis: Clinical manifestations, diagnosis, and treatment", section on 'Definition'.)
•Girls:
-The urethra may be difficult to visualize in girls. An assistant often is needed to retract the labia majora (figure 2). Having an assistant lift the labia majora anteriorly, laterally, and cephalad may also provide better urethral exposure [31]. In addition, redundant tissue around the introitus can sometimes obscure the urethral meatus. Swabbing the area from front to back may push this tissue out of the way and permit the povidone-iodine solution to pool in the meatus, making it easier to identify.
-The catheter is inserted into the urethral meatus until urine returns (figure 3). Catheters that are inadvertently placed in the vagina may be left in place to serve as a landmark for subsequent attempts.
The first few drops of urine obtained may be discarded to prevent contamination of the urine with urethral organisms or cells. A prospective study comparing early and later urine samples obtained by TUBC in 86 children demonstrated that inclusion of the early stream urine slightly increases false positive results on urinalysis for white blood cell counts and bacteria detection [11].
●Complications – Complications of bladder catheterization are minimal and include urethral trauma and microscopic hematuria. In addition, catheterization can cause iatrogenic infection. However, this risk was assessed by the American Academy of Pediatrics subcommittee on UTI in 1999 and found to be extremely low, and no change was made in the recommendation to perform the procedure [32].
Suprapubic aspiration — Although much less commonly used than TUBC, suprapubic aspiration (SPA) is a safe and effective method for obtaining urine specimens in infants and young children (usually not performed in children who are older than two years). The distended bladder, which extends above the level of the pubic symphysis into the lower abdomen, is easy to access percutaneously.
Success is more likely if the bladder can be visualized by portable ultrasonography, percussed, or palpated and the child has not emptied the bladder within 60 minutes of the procedure [9,33]. Percussion or palpation of the bladder may stimulate urination in some children. Reported success rates for the procedure range from 45 to 65 percent when ultrasound is not used [9,10] and up to almost 80 percent with ultrasonography [34]. Thus, if available, we recommend point-of-care ultrasound to confirm the presence of sufficient volume of urine in the bladder prior to SPA.
●Preparation – An explanation of the anatomy and the indications for the procedure should be given to parents and caregivers before SPA is performed.
•The site for needle insertion, in the midline, approximately 1 to 2 cm above the pubic symphysis, is widely prepared with an antiseptic solution.
•The planned puncture site may be locally anesthetized with infiltration of lidocaine or topical anesthetic techniques. (See "Clinical use of topical anesthetics in children".)
●Technique – The following steps are performed [35,36]:
•The patient is restrained in the supine and frog leg position. This position permits adequate stabilization of the pelvis (figure 4).
•The urethral opening can be occluded just before needle insertion because the procedure will stimulate urination in many children. This is accomplished by squeezing the penile urethra in boys or applying urethral pressure to the meatus in girls [35].
•A 1.5 inch, 22-gauge needle attached to a 3- or 5-mL syringe is inserted in the midline, 1 to 2 cm above the pubic symphysis. The needle should be angled 10 to 20 degrees from vertical and advanced under negative pressure until urine returns as shown in the figure (figure 5).
If the initial attempt is unsuccessful, then the needle should be partially withdrawn and redirected at an angle more perpendicular to the frontal plane.
Urine is not likely to be obtained after the third attempt [33]. Thus, if the initial two attempts are unsuccessful, the clinician can either perform TUBC or wait 15 to 30 minutes for the bladder to become more distended [37].
●Complications – Minor complications, such as microscopic hematuria, are common. Major complications, such as gross hematuria [38,39] and anterior abdominal wall abscess, are rare [40]. Intestinal perforation can occur if a loop of bowel overlies the bladder, but the small puncture rarely leads to peritonitis [35,41]. Intestinal (or other viscus) perforation may be avoided if point-of-care ultrasound is used to guide SPA or the procedure is not performed in children who have abdominal distension, organomegaly, volume depletion, or congenital anomalies of the gastrointestinal or genitourinary tract [9,40,41].
PROCESSING OF URINE SAMPLES — The urine sample should be sent immediately to the bacteriology laboratory because bacteria will continue to proliferate in the warm medium of freshly voided urine, leading to increased bacterial counts [42]. If such immediate dispatch is not possible, the container should be transported in iced water and then stored in a refrigerator at 4°C. Cooling stops bacterial growth until the urine is plated on culture medium and incubated.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Urine collection techniques in infants and children".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Blood in the urine (hematuria) in adults (The Basics)" and "Patient education: Kidney stones in adults (The Basics)")
●Beyond the Basics topics (see "Patient education: Blood in the urine (hematuria) in children (Beyond the Basics)" and "Patient education: Kidney stones in children (Beyond the Basics)" and "Patient education: Urinary tract infections in children (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●The likelihood of a urinary tract infection (UTI) varies significantly in the pediatric population according to age, sex, race, circumcision status in males, presence of urologic abnormalities, and presenting signs and symptoms (table 1). Although clinicians may have variable thresholds for diagnostic testing, urine samples for urinalysis (dipstick and microscopic examination) and culture are generally indicated when the probability of a UTI is greater than 2 percent. UTICalc can be used to determine the probability of UTI in febrile (temperature ≥38°C [100.4°F]) children aged 2 through 23 months according to clinical characteristic. (See "Urinary tract infections in infants and children older than one month: Clinical features and diagnosis", section on 'Decision to obtain urine sample'.)
●The technique for urine collection is primarily determined by whether the patient is toilet trained or not as follows (see 'Selection of technique' above):
•Children who are toilet trained can provide clean voided urine samples for urine dipstick, urinalysis, and urine culture. (See 'Clean voided samples' above.)
•We recommend that infants and children with a suspected UTI, who are not toilet trained and who are ill enough to merit antimicrobial therapy, undergo transurethral bladder catheterization (TUBC) or suprapubic aspiration (SPA) to obtain a urine culture rather than providing a cleaned, voided urine sample (clean-catch or bag specimen). We typically perform TUBC in these patients. However, SPA by a trained clinician is the recommended method for sterilely obtaining a urine culture in uncircumcised boys with a tight phimosis or some girls with labial adhesions and represents the gold standard in the diagnosis of UTI. (See 'Specimen for urine culture' above.)
•Catheterization or SPA is also the preferred method of urine collection for dipstick and microscopic examination of the urine in infants and young children who are not toilet-trained. (See 'Specimen for urine dipstick or urinalysis' above.)
•Monitoring the clinical course of otherwise healthy patients six months of age or older without antibiotic therapy is a reasonable course of action if the urinalysis from a clean voided bag specimen is not suggestive of UTI. However, a negative urinalysis or urine dipstick test does not exclude a UTI (table 2).
An infant or young child should not receive antibiotics on the basis of a positive urine dipstick or urinalysis from a clean catch or voided bag urine specimen because of the high rates of urine culture contamination associated with these methods. (See 'Specimen for urine dipstick or urinalysis' above.)
●The techniques for collection of urine in infants and children by clean voided samples, clean voided bag samples, SPA, and TUBC are described. (See 'Clean voided samples' above and 'Suprapubic aspiration' above and 'Transurethral bladder catheterization' above.)
●If available, we suggest use of point-of-care bladder ultrasound to confirm the presence of sufficient volume of urine in the bladder prior to TUBC or SPA. (See 'Suprapubic aspiration' above and 'Transurethral bladder catheterization' above.)
●Once obtained, the urine sample should be sent immediately to the bacteriology laboratory for processing. If immediate dispatch is not possible, the container should be transported in iced water and then stored in a refrigerator at 4°C. (See 'Processing of urine samples' above.)
