Urinary tract infection in infants and children: an update with special regard to the changing role of reflux

Abstract

The aim of this study was to present current theories of pathogenesis and prognosis in urinary tract infection (UTI) and renal scarring during infancy and childhood, with special regard to new insights concerning the role of vesico-ureteral reflux (VUR). For a long time VUR and UTI were considered the only risk factors for renal scarring in childhood. Now a wider spectrum of contributing conditions is commonly accepted, which all may pose different clinical consequences and require different imaging approaches. Particularly bilateral renal scarring causes long-term sequalae; therefore, renal involvement in UTI with potential scarring has become the clinical and imaging focus, and proper diagnosis of UTI as the key factor for further management has become even more important. The VUR still remains one issue on a list of important factors such as treatment onset and response, bacterial virulence, immunological factors, genetic disposition, anatomical variants, and lower urinary tract dysfunction. Recent advances in knowledge leading to changed patho-physiological concepts, and new imaging techniques, may consecutively impact the presently established standard imaging algorithms. New, advanced imaging techniques offer improved and accelerated comprehensive imaging of the paediatric urinary tract. At present, this is complimentary to the established gold standard techniques. Strong research efforts have to be made before suggesting significant changes of current imaging concepts; however, based on recent technical advances and new insight on the natural history of paediatric urological diseases, potential changes of established imaging algorithms need to be discussed and evaluated.

Imaging strategies in pediatric urinary tract infection

“…The main drawback of US in the context of pediatric UTI is its reported sensibility. US sensibility varied among the different published studies regarding acute pyelonephritis [4,[10][11][12][13][14]. This may be explained due to different operators (expert pediatric radiologists involved in this field in some studies versus residents or sonographers in others), different techniques (use of prone and supine position scanning, of color/power Doppler, of sedation, of injection of contrast medium, of high frequency scanning) as well as variable equipment.…”

“…US signs can be divided into two categories: (i) signs of pyelitis include mild dilatation, thickened pelvic wall (non-specific), and increased echogenicity of the renal sinus [15]; (ii) signs of nephritis include nephromegaly, triangular hyper-echogenicity or a rounded hypo-echoic area. Decreased perfusion on color/ power Doppler (spontaneously or after IV infusion of contrast medium) is common [10,11]. In addition, in school age girls with UTI and voiding dysfunction, bladder US completes the flowmetry examination (or urodynamics) to search for residual urine [16].…”

The Pediatric Kidney

“…• Increased peripyelonal echoes and/or thickened urothelium/pelvic wall ("urothelium sign") (Alton et al 1992 ;Sorantin et al 1997 ;Riccabona and Fotter 2004 ).…”

“…In patients where US is not clear, no high-end US or amplitude-coded color Doppler sonography is available or performable, or in patients where US fi ndings do not match clinical and laboratory results, additional imaging by acute renal scintigraphy or MRI for establishing the diagnosis or ruling out upper urinary tract infection will become necessary, particularly if only those with proven renal involvement will undergo further studies (for the assessment of vesicoureteral refl ux and scarring, the latter by delayed renal scintigraphy), as suggested by many local and international recommendations (Riccabona and Fotter 2004 ;Riccabona et al 2008a ). According to literature, the reduction of US indications in pediatric patients with acute UTI as suggested by the British guidelines (NICE 2007 ) is seen critically, as many children with signifi cant pathology may be missed and thus renal integrity it as risk (Wong et al 2010 ).…”

New Quantitative Parameters for Evaluating Radionuclide Cystography and Their Value in Understanding the Physiology of Reflux

“…Early diagnosis of VUR and urinary tract infection is necessary to decrease renal scarring (3). VUR may result in hypertension and end-stage renal disease (3,6,7). The correlation between renal scarring and VUR has been shown to vary between 23% and 75% and is higher in patients with a high grade of VUR (8)(9)(10)(11).…”