Radionuclide Investigations Of The Urinary Tract In The .
Downloaded from jnm.snmjournals.org by on June 26, 2020. For personal use only.CONTINUINGEDUCATIONRadionuclide Investigations of the Urinary Tractin the Era of Multimodality Imaging*Ariane Boubakery1, John O. Priory1, Jean-Yves Meuwly2, and Angelika Bischof-Delaloye11Departmentof Nuclear Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; and 2Department ofRadiodiagnostic and Interventional Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, SwitzerlandThis article presents the role of nuclear medicine procedures ininvestigating renal and parenchymal disease, as well as upperurinary tract abnormalities. More specifically, the use of scintigraphy is described in the exploration of urinary tract dilatationand UTIs, vesicoureteric reflux, renovascular hypertension, andrenal transplants. With a low radiation burden and the absenceof sedation, these nuclear medicine procedures are easy to perform and can provide clinicians with valuable data on renal perfusion and the function of individual kidneys, as well as on urinarytract dynamics. However, knowledge of limitations and technicalpitfalls is essential in understanding the role of scintigraphyamong contemporary imaging methods and the unique information it supplies in nephrourology.Key Words: pyelonephritis; renal transplant; renography; renovascular hypertension; urinary tract dilatationJ Nucl Med 2006; 47:1819–1836Nuclear medicine procedures can provide clinicianswith valuable data on renal perfusion and the function ofindividual kidneys, as well as on urinary tract dynamics.These procedures have a low radiation burden, require nosedation, and are easy to perform, but clinicians must beaware of the limitations and technical pitfalls of scintigraphy to understand its role among contemporary imagingmethods. This review describes the use of scintigraphy inthe exploration of urinary tract dilatation and infections,vesicoureteric reflux (VUR), renovascular hypertension(RVH), and renal transplants.URINARY TRACT DILATATIONDiuretic renography is an established procedure for theinvestigation and diagnostic work-up of upper urinary tractReceived Apr. 17, 2006; revision accepted Jun. 19, 2006.For correspondence or reprints contact: Angelika Bischof-Delaloye, MD,Department of Nuclear Medicine, CHUV University Hospital, CH-1011Lausanne, Switzerland.E-mail: angelika.bischofdelaloye@chuv.ch*NOTE: FOR CE CREDIT, YOU CAN ACCESS THIS ACTIVITY THROUGHTHE SNM WEB SITE (http://www.snm.org/ce online) THROUGH NOVEMBER2007.yContributed equally to this work.COPYRIGHT ª 2006 by the Society of Nuclear Medicine, Inc.dilatation and for the follow-up of patients with hydronephrosis. In routine clinical practice, diuretic renography isthe method of choice for differentiating a dilated unobstructed urinary system from a true stenosis and contributesto the management of patients with hydronephrosis by assessing both urinary flow and renal function. Major effortshave been made to standardize the procedure, to avoid technical pitfalls, and to allow comparison of results betweeninstitutions (1–4). In radionuclide studies of the kidneysand urinary tract of children, sedation should be avoided ifpossible, because it may interfere with bladder voiding andtherefore with the study of urinary dynamics under physiologic conditions. Increased radiation exposure of the bladdermucosa might be another concern. We generously use topicallidocaine preparations to diminish the stress of venipuncture.Receiving the child with the parents in a dedicated, calmenvironment; allowing them to become acclimated; andgiving them all the necessary information about the purposeand course of the procedure usually makes sedation unnecessary. When it cannot be avoided, local guidelines forsedating pediatric patients should be followed. We use, atthe beginning of the study, a short inhalation of an equimolarmixture of nitrous oxide and oxygen for its analgesic andamnesic properties and minor side effects.Diuretic RenographyTubular tracers such as 99mTc-mercaptoacetyltriglycine(MAG3) and 123I-orthoiodohippurate (OIH) are generallypreferred to the glomerular agent 99mTc-diethylenetriaminepentaacetate (DTPA) because of their higher renal extraction ratio and rapid plasma clearance, especially in infantsand young children and in patients with impaired renalfunction. Considering the immaturity of nephrons in newborns, the usual recommendation is that diuretic renography be delayed until the age of 4 wk. Before that age,renal tubules may be unable to respond to the effect offurosemide. Renal function matures gradually during thefirst 2 y of life. Using 99mTc-MAG3 clearance normalizedfor body surface, Lythgoe et al. found that mature clearancewas reached during the first year of life and, in 68%, evenbefore the age of 2 mo (5). Other authors have also emphasized the feasibility and reliability of diuretic renographyRENAL IMAGING Boubaker et al.1819
Downloaded from jnm.snmjournals.org by on June 26, 2020. For personal use only.in neonates (6,7). The guidelines published by the Society ofNuclear Medicine and the European Nuclear MedicineAssociation recommend the use of furosemide at a dose of1 mg/kg, up to a maximum of 20 mg in children and 40 mgin adults. We inject 1 mg/kg in infants, 0.5 mg/kg inchildren, and 40 mg in adults according to the recommendations of the Consensus Committee of the Society ofRadionuclides in Nephrourology (4). The validated timingfor furosemide administration is either 20 min or more(F120) after tracer injection, when maximal distension ofthe renal pelvis or ureter can be visually assessed, or 15 minbefore tracer injection (F215), which will then occur whenthe diuretic response of the kidney is maximal. A morerecent proposal has been to inject furosemide at the sametime as or just after (F10) the radiopharmaceutical. Thisprocedure has gained popularity, especially in infants andchildren, because it avoids repeated venous puncture andshortens the procedure (6–8). Concomitant administration ofradiotracer and furosemide does not interfere with the determination of renal function: The diuretic effect begins 1–2min after injection of the furosemide, and parenchymalextraction of tubular tracers occurs during the first minuteafter bolus injection, with a normal time to peak of lessthan 3 min. Up to now, there is no evidence that one timingof diuretic administration is better than another. Diureticresponse is evaluated by visual and quantitative interpretationof the dynamic acquisition. Postmicturition images aremandatory because a full bladder may delay urinary floweven in an unobstructed system. The effect of gravityassisted drainage (a change from the supine position to erector prone) is recommended in cases of incomplete urinarydrainage. The role of bladder catheterization is still debated,but it is not recommended in clinical routine practice. Inolder children and adults, renography is performed afterbladder emptying, whereas in non–toilet-trained children,spontaneous micturition is usually observed during the acquisition. In some particular conditions such as a neurogenic,dysfunctional, or low-capacity bladder, continuous bladderemptying during the examination may be indicated. Adequate functioning of the affected kidney (glomerular filtration rate [GFR] . 15 mL/min) and adequate hydration aremajor determinants of the response to furosemide. Oralhydration (15 mL/kg during the 30 min before renography)is usually sufficient. Infants will receive bottle or breastfeeding before the test. In particular cases, an intravenoussaline infusion before and during the study may be preferred.Urinary output, reflecting both the diuretic response and thehydration state of the patient, should be measured during thestudy. Furthermore, in neonates and infants, renal pelviscompliance is high: An apparently obstructed responsepattern may reflect just the volume expansion induced byfurosemide (9). Background-corrected time–activity renalcurves are used to assess urinary drainage and to calculatedifferential renal function. An unobstructed system is easilyassessed by prompt tracer washout, whereas a rising curvewill be highly suggestive of true obstruction. Simple param-1820THE JOURNALOFeters such as time to peak and time to obtain a washout of50% of tracer from the kidney allow one to quantify theresponse. Other quantitative parameters that assess drainagerelative to renal function (output efficiency, pelvic excretionefficiency, parenchymal transit time index, normalized residual activity) may be used to refine the response evaluation,but none allows unequivocal interpretation of diuretic renography in impaired kidneys. Thus, besides assessing thediuretic response, quantifying renal function is important.Chronic obstruction may cause a loss of renal parenchymalfunction due to increased pressure in the urinary system(Table 1).With tubular tracers, the normal time to peak is less than3 min in a well-hydrated subject, including neonates andyoung infants studied with the F10 protocol. Differentialrenal function should consequently be measured during theextraction phase of the renogram, that is, during the first2 min (Fig. 1). Differential renal function represents thecontribution of each kidney to the sum of the left and rightrenal activity and normally ranges from 45% to 55% (2). Adifferential renal function below 40% or a decrease ofdifferential renal function of more than 5% on successivediuretic renography studies is generally considered indicative of renal function deterioration, possibly because ofobstructive uropathy, and is used as the threshold forsurgery in most institutions. We do not believe that differential renal function alone can reliably be used to assessrenal function. The impaired function of one kidney may becompensated for by the contralateral nonaffected kidney.This compensation may induce an apparent fall of differential renal function whereas the absolute function of theaffected kidney in fact remains stable. g-Camera–basedmethods of determining absolute renal function are notrecommended by the experts, and clearance techniquesbased on blood sampling remain the gold standard. However, we measured the absolute function of individualTABLE 1Limitations and Pitfalls in Performing and AssessingDiuretic ingLimitation/pitfallHydration statusBladder emptyingRenal function insufficiencyPatient position, movementsRadiopharmaceuticalTiming of furosemide administrationChange of position, postvoiding/late imagesRegions of interest, background subtractionQuantitative parameters used to assessurinary drainageRenal function measurementParenchymal aspect and renal functionResponse to furosemide, change of positionand voidingLevel of urinary drainage impairmentNUCLEAR MEDICINE Vol. 47 No. 11 November 2006
Downloaded from jnm.snmjournals.org by on June 26, 2020. For personal use only.FIGURE 1. Diuretic renography (F10) in6-mo-old boy who had febrile UTI by ageof 2 mo. Renal sonography and VCUGhad normal findings. (A) One-minuteposterior views demonstrate normaltracer uptake by both kidneys and rapidwashout, with bladder activity visiblefrom third minute after injection andspontaneous micturition occurring atminute 10. (B) Left (red) and right (blue)renal time–activity curves show symmetric relative function (left, 50%; right, 50%)and normal time to peak (,180 s).kidneys using a camera-based method in infants with severeunilateral pelviureteric junction stenosis treated either surgically or conservatively, and we found reliable results evenin neonates and young infants (6,10,11). This finding hasbeen confirmed by others, who combined the overall GFRmeasured with 51Cr-ethylenediamine tetraacetic acid anddifferential renal function measured during renography toobtain a single-kidney GFR (12). Using differential renalfunction to assess renal function is also inappropriate inpatients with only one functioning kidney, bilateral hydronephrosis, urethral valves, or renal failure. Another important issue is that none of the methods predicts the finaloutcome for renal function.Nonradionuclide ImagingSonography easily detects hydronephrosis both in infantsand in adults and remains the first imaging modality usedfor the diagnosis and follow-up of hydronephrosis. Intravenous urography was used formerly but has now beenreplaced by unenhanced spiral CT, which needs no bowelpreparation, takes approximately 5 min, and detects otherabnormalities including parenchymal thinning, edema,perinephric fluid, and tumors. CT has been used in thediagnosis of urolithiasis and appears to be safe, simple,rapid, and accurate but does not provide functional information and may miss noncalcareous causes of obstruction(13,14). Magnetic resonance urography (MRU) has beenfound to be efficient in the investigation of a dilated upperurinary tract and offers advantages over other establisheddiagnostic procedures: The technique provides high anatomic resolution and information on renal function withoutradiation (14–16). Sequences with T2 weighting provideessential information on the dilated, fluid-filled urinarysystem without contrast administration, regardless of renalfunction. Gadolinium-enhanced T1-weighted sequencestogether with furosemide injection allow evaluation of theentire upper system. Three-dimensional MRU also offersthe possibility of quantifying renal parenchymal function incases of poor renal function or gross hydronephrosis (17).Another challenging potential of MRU is the measurementof single-kidney GFR and the mapping of intrarenal GFR.In small children, the major drawback of MRU is the needfor sedation and bladder catheterization. The procedure isquite lengthy and may not be used in the routine clinicalevaluation of hydronephrosis but can provide useful information in cases of complex urinary tract abnormalities suchas duplex kidneys (Fig. 2).Prenatal HydronephrosisPrenatal hydronephrosis is the second most frequentlyoccurring fetal structural anomaly after those involving thecentral nervous system and is usually detected during thesecond or third trimester of pregnancy (18,19). Prenatalhydronephrosis has an incidence ranging from 0.3% to4.5%, depending on the criteria used to differentiate hydronephrosis and pyelectasis, and is bilateral in 37%–57%.The hydronephrosis grading system developed by the Society for Fetal Urology takes into account the anteroposterior diameter of the renal pelvis, the appearance of calices,and the renal parenchyma (Table 2) (20). There is noabsolute threshold value, but follow-up is generally recommended if the anteroposterior diameter is at least 7–10 mmduring the third trimester of pregnancy. The objectives ofpostnatal evaluation are to confirm hydronephrosis and thento determine its cause and to assess renal function. Bilateralhydronephrosis requires prompt evaluation by sonographyand voiding cystourethrography (VCUG), especially inboys, in order not to miss posterior urethral valves (21).Unilateral hydronephrosis is generally considered a benigncondition that rarely leads to renal failure. The first postnatal sonographic study is usually performed during thefirst week after birth, depending on the severity of theprenatal findings, but not during the first 72 h because ofreduced urine output after delivery (18,21). More commoncauses of fetal hydronephrosis are transient hydronephrosis(48%) and physiologic hydronephrosis (15%), which willspontaneously resolve after birth. About 35%–50% ofprenatal hydronephrosis will persist on sequential sonographic studies performed during the first and sixth weeksof life. The most common cause of persistent hydronephrosis is pelviureteric junction stenosis, which is bilateralin 20%225% of cases and more frequent in males. Treatment of congenital unilateral pelviureteric junction stenosisis still debated, but there is evidence that a conservativeRENAL IMAGING Boubaker et al.1821
Downloaded from jnm.snmjournals.org by on June 26, 2020. For personal use only.FIGURE 2. Bilateral duplex kidney diagnosed in 9-y-old boy after febrile UTI.(A) VCUG shows bilateral pyeloureteralreflux with opacification of incompletesystems, suggesting duplication. (B) Coronal T2-weighted MRI scan confirmspresence of duplex kidneys bilaterally.Lower pyelocaliceal systems are dilated(arrows) even when upper ones remainthin (arrowheads). (C) Sagittal sonographic view of right upper quadrantshows enlarged kidney with broad layerof parenchyma on upper pole (arrowhead) and atrophic lower pole (arrow). (D)One-minute parenchymal view showsdecreased tracer uptake by left lowersystem and parenchymal defects at bothpoles of right kidney. (E) Images obtained1, 4, 9, and 15 min (from left to right) afterinjection show delayed urinary flow inlower moiety of left kidney due to loss ofparenchymal function. (F) Renograms ofleft and right kidneys show symmetricfunction (left, 49%; right, 51%) and nosignificant impairment of urinary flowunder furosemide. (G) Indirect radionuclide cystography demonstrate VURin both left and right lower systems.approach with close follow-up of renal function can safelybe recommended (Fig. 3); 20%225% of infants will require surgery during the first 2 y of life (22). Otherinvestigators have emphasized the need for long-termfollow-up and found that 50% of neonates with unilateralpelviureteric junction stenosis finally required surgery bythe age of 7 y (23). Close follow-up with diuretic renography and sonography can be used safely to monitor renalfunction and the degree of hydronephrosis (24), althoughTABLE 2Grading System for Antenatally Detected HydronephrosisGrade*0IIIIIIIVCentral renalcomplex (pelvis)IntactMild splitting 5 dilatationModerate splitting, but complex,confined to renal borderMarked splitting, pelvis dilatedoutside renal border, and calicesdilatedFurther caliceal dilatation*Proposed by the Society of Fetal Urology (20).1822THE alNormalThinnone of the investigations is able to predict the ultimatedeterioration of renal function. The use of intravenousurography is declining, and CT is not routinely used inchildren (25). MRU offers the advantage of providing highresolution anatomic details and functional informationwithout radiation but remains a long and invasive procedurethat requires sedation in infants. Therefore, MRU is notrecommended for the diagnosis and follow-up of all children with hydronephrosis and should be used to addressonly complex urogenital malformations.The second most common cause of prenatally detected hydronephrosis is VUR, which will be discussed ina separate section. Other urologic abnormalities includemegaureters and multicystic dysplastic and duplex kidneys.Adult HydronephrosisWhereas hydronephrosis is most often detected fortuitously in asymptomatic children, in adults it is generallydiagnosed because of recurrent flank pain of various durations and intensities, UTI, or acute ureteric colic due tourolithiasis. The role of renography is probably limited inpatients presenting to the emergency room for acute renalcolic. Sonography followed by unenhanced CT will confirmhydronephrosis and reliably localize the level of obstruction. Some authors have observed that obstruction is bettercategorized by diuretic renography and that it should beNUCLEAR MEDICINE Vol. 47 No. 11 November 2006
Downloaded from jnm.snmjournals.org by on June 26, 2020. For personal use only.FIGURE 3. Diuretic renography (F10)obtained during follow-up of 4-y-old girltreated conservatively for left pelviureteric junction stenosis detected prenatally. (A) One-minute posterior viewsshow dilated left kidney with preservedparenchymal function despite impairedurinary drainage above pelviureteric junction. Right kidney is normal. (B) Left (red)and right (blue) renograms confirm symmetric (left, 51%; right, 49%) and normaltracer extraction by b
investigating renal and parenchymal disease, as well as upper urinary tract abnormalities. More specifically, the use of scintig-raphy is described in the exploration of urinary tract dilatation and UTIs, vesicoureteric reflux, renovascular hypertension, and renal
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INTERNATIONAL COMMITTEE FOR RADIONUCLIDE METROLOGY Editors Pablo Arenillas, Dirk Arnold and Uwe Wätjen 21st International Conference on Radionuclide Metrology and its Applications (ICRM 2017) 15-19 May 2017, Buenos Aires, Argentina Proceedings part II of the ICRM Technical Series on Radionuclide Metrology ISSN 2522-4328
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an indwelling urinary catheter. The indwelling urinary catheter is considered a foreign object in the lower urinary tract, which means a CAUTI differs from an infection occurring in the urinary bladder of a patient who is not catheterized (Leidl 2001). CAUTIs do not produce the
