Introduction
Urinary tract infection is a bacterial invasion of the kidneys and the urinary tract. It is designated as pyelonephritis or upper UTI when the infection involves mainly renal parenchyma and pelvicalyceal system. Lower UTI involves infection of the urinary bladder and urethra.
Causes
UTI is predominantly caused by enterococci like certain strains of E.Coli and other gram-negative bacilli such as Proteus, Klebsiella, and Pseudomonas, which are uropathogenic. It is rarely caused by tubercular bacilli.
In children below the age of 3-4 years, UTI is associated with underlying congenital anomalies such as posterior urethral valves, PUJ obstruction, vesicoureteral reflux (VUR), bladder diverticula or ureteroceles, etc.
Presentation
The clinical manifestations of UTI are non-specific and general. At younger age i.e. in new-borns and infants- fever, failure to thrive, vomiting or diarrhea, convulsions, jaundice predominate, hence UTI can be missed at the early stage when it is important to diagnose.
In older children above the age of 4-5 years, UTI manifests with fever, pain in the abdomen especially loin pain, vomiting with urinary symptoms such as frequency, urgency, dysuria, painful micturition, and foul-smelling urine. The fever can be associated with chills and recurs frequently. When the UTI is recurrent there is a failure to thrive, anemia, listlessness, and general malaise.
Diagnosis
The gold standard for diagnosis of UTI is urine culture, colony count, and antibiotic sensitivity report in a clinical setting of UTI. The collection of urine under sterile conditions is an important point to remember. In very young infants, suprapubic bladder aspiration, and in females or infants, the use of urinary collection bags may be needed.
In older children, midstream clean catch collection of urine in a sterile container and sending it within an hour or two to the lab are important points to get an accurate diagnosis of UTI. The presence of pus cells (more than 10/HPF in males and 25/hpf in female children) and gram staining of fresh samples of urine for gm-ve bacilli support the diagnosis of UTI. 50% of cases of UTI may not have pyuria.
There are chemical tests like a) leukocyte esterase test and b) nitrite test, which can be used as screening tests for UTI but the gold standard, is urine culture even in these children.
Investigations
Since there is a high incidence of congenital obstructive and non-obstructive malformations of the kidney and urinary tract in 50-75% of infants with UTI, early diagnosis of these malformations is useful in preventing permanent kidney damage which occurs if congenital defects + UTI combine. Hence every child with UTI below the age of 3 years should be investigated as follows:
- USG of kidneys, pelvicalyceal system, ureter, and urinary bladder to detect dilatation (hydronephrosis, hydroureter, distended bladder, and residual urine) which denotes either obstruction in the subvesical region or VU reflux.
- To detect the site of obstruction (like PU valves) or reflux, MCU should be performed in every child below the age of 2-3 years with UTI. It is done 3 - 6 weeks after the acute episode is over. Above the age of 3 years, MCU is indicated in those children with abnormal USG findings or renal scars detected on Tc DMSA renal scan which is the 3rd imaging test in a child with UTI. DMSA renal scan is ideally done 3 - 6 months after the acute episode is over. The aim of the Tc99 DMSA renal scan is to detect acute infection of the kidney and subsequently after 3-6 months of pyelonephritis to detect permanent renal scars.
Treatment
Treatment of UTI is an early institution of the appropriate drugs according to the antibiotic sensitivity report for a duration of 7-10 days. In sick children especially neonates and infants, intravenous antibiotics are required even before the culture report is available. The recommendation is to use Ampicillin and Gentamicin. This is the treatment given for sepsis. Delay of more than 72 hrs in starting the antibiotic can result in permanent renal damage. A 2nd urine culture after 3-5 days of antibiotic therapy should be sterile while the clinical features such as fever resolve within 2-3 days; raised ESR and CRP resolve over 2-3 weeks.
High Risk UTI
A high-risk UTI is the one, which can cause permanent renal scars. The long term consequences of recurrent pyelonephritis can be multiple bilateral renal scars resulting in end-stage renal disease requiring renal transplant or hypertension in young adulthood. In young females, the risk of toxemia of pregnancy is high in those who suffered from recurrent UTI in school age. Because of these long-term complications, it is mandatory to follow every infant with UTI, both males, and females, and every school-age girl with recurrent UTI for a minimum of 20-25 years.
Management of high-risk UTI consists of monitoring growth, BP recording, renal function tests, size of the kidneys by USG, and periodic urine cultures.
Advise to Parents
The parents should be educated as regards the perineal hygiene especially the use of diapers, cleaning the perineal region with water (not to use any antiseptics) and to toilet train the children at the age of 2-3 years, to give plenty of fluids and inculcate good habits of voiding every 3-4 hourly to prevent residual urine. These are some of the simple measures for the prevention of recurrent UTI.
Children with constipation should be advised high fiber-containing food and increased intake of fluids along with the use of mild laxatives or suppositories because constipation is associated with recurrent UTI.
Recurrent diarrhea can cause UTI due to the same organism because of the proximity of the rectum and the urethra.
The use of antibiotics for diarrhea can result in resistant strains of organisms leading to recurrent UTI and since mostly the diarrheas are viral in origin, antibiotics should not be used indiscriminately for acute diarrheas of infants.
Compliance, as regards the use of long term use of single night dose of co-trimoxazole or Furadantin, should be observed closely by parents to prevent recurrences.
Recurrence
The best way to prevent recurrence of UTI is to treat the first infection thoroughly as mentioned above and to detect underlying lesions that may require surgical corrections. Long term chemoprophylaxis using a single night dose of appropriate drug-like co-trimoxazole or Furadantin or Nalidixic acid at 1/3rd dose prevents recurrent UTI in children with VUR or recurrent cystitis or in those in whom UTI follows urologic procedures.
Good perineal hygiene, treatment of threadworms, treatment of constipation, high fluid intake, and toilet training for voiding periodically every 2-3 hours are some of the measures which help to prevent recurrent UTI. Monitoring for UTI includes periodic urine cultures initially every monthly and if cultures are negative in the first 3 months, regularly every 3 months or whenever there is fever without the focus of infection.
The choice of drug for recurrent UTI depends on culture and antibiotic sensitivity. Pyelonephritis is treated for 7-10 days while Lower UTI i.e. cystitis may be treated for 3-5 days followed by long term drug therapies mentioned above. On average 2-3 years of treatment is required for VUR and 6 months to 1-year treatment for post urologic operations or procedures.