A urinary tract infection (UTI) is the presence of bacteria in the urinary tract together with a response from the body. In a child, that definition carries more weight than it does in an adult, because the same infection can be the first sign of a urinary tract that was malformed before birth. The urethra is short, especially in girls; the inflammatory response in the kidney can leave permanent damage; and structural problems — vesicoureteral reflux (VUR), posterior urethral valves, and other congenital anomalies of the kidney and urinary tract (CAKUT) — are common enough that a single febrile infection triggers a structured search for them.
The clinical sequence organises the subject. An unexplained fever leads to a urine specimen. A first febrile UTI is treated as infection of the kidney (pyelonephritis) rather than of the bladder alone (cystitis). Imaging then asks whether the tract is structurally normal, and the findings decide how much that kidney is at risk over the following decades. The event worth preventing is rarely the first infection, which is what reveals the underlying problem, but the second and third, because repetition is what turns an inflamed kidney into a scarred one.
Choose a route through this family
Start with the first three notes. They give the vocabulary, the probabilities and the age bands that the rest of the family assumes.
- Pediatric UTI: Foundations and Pathophysiology — what the terms mean, the defences the urinary tract relies on, why the bacterium Escherichia coli (E. coli) causes most infections, why an organism other than E. coli raises the odds of a structural abnormality, and how bacteria attaching to the lining of the tract set off the inflammation that produces fever and white cells in the urine (pyuria).
- Pediatric UTI: Epidemiology and Pre-Test Probability — how common these infections are at each age, how sex and circumcision status shift the probability, and why that probability decides whether a urine specimen is obtained at all.
- Pediatric UTI: Clinical Presentation by Age — which signs belong to the neonate, the infant, the preschool child and the adolescent, and why symptoms that point to the urinary tract appear only after about age 3.
The acute episode comes next. The sampling and treatment notes are best read as a pair, since the order in which the specimen and the antibiotic are obtained is part of both.
- Pediatric UTI: Urine Sampling and Culture — the sequence of a bag specimen, a dipstick test strip and a culture, what the dipstick’s two markers each mean, and the colony counts that define a positive culture.
- Pediatric UTI: Acute Treatment and Compartment Logic — why antibiotics that concentrate only in urine, such as fosfomycin and nitrofurantoin, treat cystitis and not pyelonephritis, when to use the intravenous route, and how long to treat.
Imaging follows the acute episode and decides which structural question comes next. The notes on bladder function, reflux, obstruction and malformations carry those questions between them.
- Pediatric UTI: Imaging After a First Febrile UTI — the ultrasound-first ladder, when an X-ray study of the bladder during voiding (cystography) is justified, and what the two nuclear scans, DMSA and MAG-3, each answer.
- Pediatric UTI: Bladder and Bowel Dysfunction — the voiding history, constipation criteria, the two opposite bladder patterns, and why the bowel is treated before imaging is repeated.
- Vesicoureteral Reflux in Children — the definition, grades I–V, causes, and the choice between surveillance, antibiotic prophylaxis and surgery.
- Posterior Urethral Valves and Obstructive Uropathy in Children — where obstruction occurs, how the most damaging congenital cause presents before and after birth, and why its bladder and kidney effects continue for life.
- CAKUT and Congenital Solitary Kidney in Children — the malformation spectrum, why childhood kidney failure looks different from adult kidney failure, and how a single kidney is followed.
The last note follows the kidney itself into adult life.
- Pediatric UTI: Renal Scarring and Long-Term Outcome — which children scar, why recurrence rather than the first episode is the driver, and how blood pressure and kidney function are followed afterwards.
Where this material stops
The reasoning here is specific to childhood, and several neighbouring subjects follow different rules. Urinary tract infection in adults, recurrent cystitis in adults and infection in pregnancy belong elsewhere, as do urinary infections in children who already have a neuropathic bladder or an indwelling catheter. Glomerular disease, renal replacement therapy and the wider paediatric chronic kidney disease curriculum are separate subjects; only the contrast between childhood and adult causes of kidney failure is included, because it explains why a first febrile UTI triggers a search for CAKUT. Weight-based antibiotic doses are not given, since doses belong to a current paediatric formulary and both resistance patterns and licensing differ by country.