Imaging in Urinary Tract Infectioin

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1 Case Report Jawa, ZM Oniyangi, O Ononiwu, UN Imaging in Urinary Tract Infectioin Corresponding Author ( ) Jawa, Zabah Muhammad Department of Nuclear Medicine / Radiology National Hospital Abuja, Nigeria Jawazm@yahoo.com Department of Nuclear Medicine, National Hospital Abuja Department of Paediatrics, National Hospital Abuja Manuscript first received on the 13/06/17, peer reviewed and accepted for publication on 24/06/17 Abstract The imaging of a child with a proven urinary tract infection (UTI) remains a significant dilemma especially in Africa where some imaging modalities are either unavailable or unaffordable. The role of imaging in UTI is to assist in confirming the infection, identify those children with risk factors that will predispose them to recurrent UTI and also identify those who have suffered complications. This review article provides an overview and suggested approach to imaging in UTI. The different imaging tools and the type of information they provide and their possible side effects would be discussed. Keywords; UTI (urinary tract i n f e c t i o n ), I m a g i n g, V U R (vesicoureteric reflux), Renal scarring Introduction Imaging of a child with urinary tract infection (UTI) remains controversial, with several 1-2 different imaging modalities implode. Most pediatricians use imaging modalities based on historical practice and some based on availability rather than on strong scientific evidence, very few based on some institutional protocols, and on the recommendations of official guidelines 3 published several years ago. Imaging especially with modalities that utilizes ionizing radiation such as IVU and CT- scan should be limited to the child at risk 3 of developing permanent renal damage. Its aim should be to demonstrate anatomical or functional abnormalities that predispose the urinary tract to new or progressive renal damage. There are two types of imaging modalities available for investigating a child with UTI, those that provide anatomical information (X-ray, ultrasound scan, CT-scan, IVU, cystography) and those that provide 4-5 information on physiology (renography). It is also important to differentiate modalities that utilizes ionizing radiation verses those with non-ionizing radiation when requesting for imaging modalities. Ultrasound scan which is the most common and first imaging tool requested by paediatrician in evaluating a child with UTI, uses non-ionizing radiation and therefore it is safe, can be repeated 5-6 severally. Epidemiology UTIs are caused by invasion of the urinary tract (bladder and/or kidneys) with bacteria. Both the bacterial infection together with inflammatory response that results from the infection is capable of causing renal damage. 57

2 7-8 A significant bacteriuria must to be present 5 to document a UTI, with at least microorganisms per milliliter of urine. Approximately 1% of boys and 3% of girls have a UTI in their first decade of life. The prevalence of UTI is more in males in the first two months of life due to congenital abnormalities of the urinary tract and thereafter, girls are more likely to develop a UTI and have an increased incidence of recurrent UTI when compared with boys. Escherichia coli is responsible for approximately 80% of UTIs. Different types of Gram-negative microorganisms exist, with different degrees of virulence. A more virulent type of E. coli shows fimbriae. More than 90% of children with acute pyelonephritis have a fimbriated E. coli in their urine, with only 19% of children with cystitis having this more virulent subtype of 13 E. coli. Other microorganisms responsible for the remaining 20% of UTI are Proteus, Enterococcus, Pseudomonas, Klebsiella, Staphylococcus aureus, and Staphylococcus epidermis. An atypical microorganism often results in greater clinical concern because of the more virulent nature of the infection and the greater risk of renal damage. The clinical problem with UTI in children UTI is a common problem in children and must be considered in a child with fever. The prevalence of UTI is approximately 5% in 15 infants and young children with fever. Prompt diagnosis and treatment is important to prevent the potential complication of acute pyelonephritis. Renal scarring is the most i m p o r t a n t c o m p l i c a t i o n o f a c u t e pyelonephritis. Renal scarring increases the risk of developing hypertension. A significant percentage of patients with persistent hypertension will have evidence of renal scarring and this risk is even higher with bilateral renal scarring. It is therefore important to determine which child has acute pyelonephritis and renal scarring. UTI and development of renal scarring can be associated with a variety of conditions such as vesicoureteric reflux, obstructive uropathy, urinary bladder dysfunction and renal dysplasia. There is a very strong association between vesicoureteric reflux (VUR) and the development of renal scarring. Imaging tools are helpful in understanding these relations. Imaging techniques in UTI 1. Ultrasound scan; ultrasound scan has become one of the most popular and acceptable imaging tool by paediatrician because it is readily available, affordable and uses non- ionizing radiation. Ultrasound scan is able to detect urinary tract dilatation, but unable to determine if it is as a results of obstruction. Evidence of VUR is inferred by the demonstration of lower ureteric dilatation. Ultrasound findings in acute pyelonephritis include increase renal size, areas of hyperechogenity and poor corticomedullary differentiation. In the setting of renal scarring, there may be decreased renal size and irregular parenchymal outline. Unfortunately, the sensitivity of ultrasound is poor for detection of renal scarring. Ultrasound is greatly operator dependent and 58

3 21- requires skills especially in young children Intravenous urography (IVU); IVU techniques requires adequate bowel preparation, which may be difficult in children, intravenous contrast medium injection and exposure to ionizing radiation, these limitations have made IVU unsuitable for imaging children with UTI. However, it is an excellent modality to demonstrate anatomical abnormalities that may predispose children to UTI e.g. obstruction and renal duplication, it may show caliceal and parenchymal abnormalities of acute pyelonephritis and renal scarring. 3. Micturating cystourethrography (MCUG); MCUG is a good anatomical modality for the visualization of the urinary bladder and demonstration of severe VUR. The male urethra can be evaluated for the presence of posterior urethral valves. However, its limitations are, the kidneys cannot be evaluated, it is invasive involving urethral catheterization and use of ionizing radiation. 4. Computed tomography (CT-scan); CTscan is an anatomical modality that can detect acute pyelonephritis and renal scarring. The sensitivity and specificity of CT to other modalities in imaging UTI is studied in available literature. CT is not a preferred technique in imaging UTI because it involves high ionizing radiation dose, injection of contrast medium and it is expensive. 5. Magnetic resonance imaging (MRI); provides a superb anatomical details using non-ionizing radiation and it can be used to detect renal parenchymal lesions associated with UTI. Its sensitivity and specificity is similar to cortical renography. However, MRI is expensive, not readily available and unfriendly in children. 6. Cortical renography; Cortical renography using Tc-99m DMSA (Dimercaptosuccinic acid) is a nuclear medicine functional imaging modality that is very sensitive for the detection of renal scarring in UTI (Figure 1). It is non-invasive and requires no patient preparation and uses minimal ionizing radiation. The most important advantage of cortical renography is that it provides differential individual percentage renal function. 7. Nuclear indirect cystography; This is nuclear medicine functional imaging modality involving the intravenous a d m i n i s t r a t i o n o f Tc m D T PA (Diethylenetriamine pentaaacetate) and serial images acquired using the gamma camera. The sensitivity and specificity to detect VUR is 84% and 95% respectively. It can also provide information of renal perfusion, parenchymal uptake, excretion as well as differential percentage individual renal function. Comparison of Imaging modalities. After the review of available literature on imaging children with UTI, the following information is clear; 1. Ultrasound has a low sensitivity for the detection of VUR and renal scarring when compared to cortical renography and nuclear indirect cystography respectively. Even with 59

recent improvement in ultrasound equipment and Doppler techniques, have shown that the sensitivity of ultrasound in detecting VUR 21,29- even in the experience hands is only 40%. 30 2.

4 recent improvement in ultrasound equipment and Doppler techniques, have shown that the sensitivity of ultrasound in detecting VUR 21,29- even in the experience hands is only 40% Cortical renography has a higher sensitivity than IVU and CT for the detection of renal scarring. 3. Following a diagnosis of UTI, renal scarring can occur without demonstrable VUR. However, studies have shown high association between infection and VUR with VUR in 99% of children with bilateral renal scarring and 72% of children with unilateral renal scarring. Surprisingly, 60% of children with a documented UTI did not have VUR. 23,27,35 4. Vesicoureteric reflux in siblings. Imaging contributes to the screening of VUR in asymptomatic siblings of patients' known to have this disorder. In this situation, nuclear indirect cystography is the imaging modality of choice because of its high sensitivity for detecting reflux and lower radiation exposure. Studies have shown that nuclear indirect cystography has detected 45% VUR 30, 31 in 50% of siblings. Figure 1. Cortical renography (DMSA), showing bilateral renal scarring consistent with acute UTI. The likelihood of VUR in this setting is 99%. Recommendations; We are aware that facilities and experience varies from centers, the recommended suggested below are based on our experiences and available facilities. The use of these recommendations will help maximize the detection of children with cortical involvement in UTI and minimize 14,17,31 unnecessary imaging in children. 1. At diagnosis of UTI, it is recommended to image all children younger than 1 year with ultrasound, nuclear indirect cystography and cortical renography and Children older than 1 year should be imaged with ultrasound and cortical renography, and nuclear indirect cystography or MCUG only if there is evidence of renal scarring on ultrasound or cortical renography. 2. At follow-up, routine ultrasound is recommended to assess for kidney size and 60

5 cortical renography only if there is concern about renal growth on ultrasound. Nuclear indirect cystography can be done to determine resolution of VUR or evidence of recurrent UTI. 3. Siblings of a child with diagnosed VUR should be screened with nuclear indirect cystography up to the age of 10years, after which the use of ultrasound scan is recommended. Contribution of the authors Dr Jawa initiated the study while Drs Oniyangi, O and Ononiwu, UN participated in revising the manuscript and making critical contribution in the clinical content and giving final approval for the study to be submitted. References 1. Biassoni L, Chippington S. Imaging in urinary tract infections: current strategies and new trends. Semin Nucl Med. 2008;38: Conway JJ. The role of scintigraphy in urinary tract infection. Semin Nucl Med. 1988;18: Charron M, Hickey RW, Hoberman A. Imaging studies after a first febrile urinary tract infection in young children. N Engl J Med 2003; 16: Sfakianakis GN, Sfakianaki E. Renal scintigraphy in infants and children. Urology. Elsevier; 2016;57: Ta y l o r AT. R a d i o n u c l i d e s i n nephrourology, Part 2: pitfalls and diagnostic applications. J Nucl Med 2014; 55: Piepsz A, Ham HR. Pediatric applications of renal nuclear medicine. Semin Nucl Med 2006; 3: Shulkin BL, Mandell GA, Cooper JA, Leonard JC, Majd M, Parisi MT, et al. Procedure guideline for diuretic renography in children 3.0. J Nucl Med Technol. 2008;36: Gordon I, Piepsz A, Sixt R. Guidelines for standard and diuretic renogram in children. Eur J Nucl Med Mol Imaging. 2011;38: Madrigal G, Odio CM, Mohs E. Single dose antibiotic therapy is not as effective as conventional regimens for management of acute urinary tract infections in children. Pediatr Infect Dis J 1988; 7: Rossleigh MA. Renal Cortical Scintigraphy and Diuresis Renography in Infants and Children. J Nucl Med. 2001;42: Martín Aguado MJ, Canals Baeza A, Vioque López J, Tarazona JL, Flores S e r r a n o J. [ Te c h n e t i u m m - dimercaptosuccinic acid (DMSA) scintigraphy in the first febrile urinary tract infection in children]. An espan?oles Pediatr. 2000;52: Jodal U: The natural history of bacteriuria in childhood. Infect Dis Clin North Am 1987; 1: , 13. Noorbakhsh S, Lari AR, Masjedian F. C o m p a r i s o n o f i n t r a v e n o u s aminoglycoside therapy with switch therapy to cefixime in urinary tract infections. Saudi Med J 2004; 25: Piepsz A, Ham HR. Pediatric applications of renal nuclear medicine. Semin Nucl Med. 2006;36: Mandell G, Eggli D. Procedure guideline for renal cortical scintigraphy in children. J Nucl Med. 1997;38:

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Giovanni Montini has documented that he has no relevant financial relationships to disclose or conflict of interest to resolve.

Giovanni Montini has documented that he has no relevant financial relationships to disclose or conflict of interest to resolve. Imaging in Pediatric UTI Giovanni Montini Milano, Italy giovanni.montini@unimi.it