Urinary tract infection and pyelonephritis: Case

This six-week-old infant presents with fever, vomiting, and reduced feeding, which together with a positive urine sample make pyelonephritis the working diagnosis. Infants under three months are the highest-risk group for UTI complications, with a non-negligible risk of bacteraemia and immature immune responses, so this child needs a lower threshold for investigation and parenteral therapy than an older infant. ^[1]

Clinical findings

The key findings are the young age, the fever with non-specific features rather than localising urinary symptoms, and the positive urine. In an infant this young, dysuria and flank pain cannot be reported, so fever, irritability, poor feeding, and vomiting are the presenting picture. The suprapubic aspirate growing Escherichia coli with both leucocyte esterase and nitrites positive confirms true infection rather than contamination, because a suprapubic specimen is the gold standard for sterility and any growth of a single uropathogen is significant. ^[1]

Because he is under one month beyond the neonatal period and febrile, the standard of care includes a full sepsis evaluation with blood cultures and consideration of cerebrospinal fluid analysis, and parenteral antibiotics rather than oral therapy. A raised creatinine or hypertension would mandate urgent ultrasound to exclude obstruction, and a palpable bladder or abdominal mass would raise concern for posterior urethral valves in a boy. ^[1]