Performing renography in children with antenatally detected pelvi-ureteric junction stenosis: errors, pitfalls, controversies.

The aim of this work is to present to the reader the practical experience of three clinicians having actively participated to the publication of the guidelines on renography in children. The present publication should be considered as a practical guide. We have underlined good practice, obvious errors to avoid, common pitfalls which might be overlooked, some items for which more than one reasonable solution exists and finally a few controversial points, for which there is still no agreement and no solid evidence to resolve these issues. This paper is only focused on the aspects of acquisition and processing and will not cover the clinical aspects, namely the interpretation of the renogram in terms of renal obstruction or, more precisely, in terms of risk of renal deterioration.

A single sample method for evaluating 51chromium-ethylene diaminic tetraacetic acid clearance in normal and hyperthyroid cats.

BACKGROUND: Chronic kidney failure is frequently seen in middle-aged and elderly cats. 51Chromium-ethylene diaminic tetraacetic acid (51Cr-EDTA) clearance and single blood sample (SBS) method are used in several species to estimate the glomerular filtration rate (GFR). HYPOTHESIS: The hypothesis of this study was that 51Cr-EDTA clearance could be determined using an SBS method in normal and hyperthyroid cats. ANIMALS: Forty-six cats were included in this study, with an average age of 9.5 years. Of these cats, 27 had hyperthyroidism; 19 were healthy. METHODS: After IV injection of 51Cr-EDTA (average dose: 4.25 MBq), 7 blood samples were obtained between 5 and 240 minutes. Reference clearance was calculated in mL/min and mL/min/kg body weight, using a 2-compartment model. Optimal time for clearance measurement with SBS was then determined by systematically comparing each individual plasma concentration to the reference multisample clearance. RESULTS: The average reference plasma clearance of 51Cr-EDTA for all cats was 14.9 mL/min (3.7 mL/min/kg). The clearance in hyperthyroid cats averaged 16.4 mL/min (4.3 mL/min/kg) and in normal cats averaged 10.3 mL/min (2.4 mL/min/kg). The optimal time for the SBS was 48 minutes after injection of tracer 51Cr-EDTA (R2= 0.9414), giving the following converting equation: clearance = (0.0066 x DV48 minutes) - 0.9277 (in mL/min). CONCLUSIONS AND CLINICAL IMPORTANCE: In this study, the single sample 51Cr-EDTA clearance method was used to estimate the global GFR in cats. The method identified differences in clearance between normal and hyperthyroid cats. The optimal time for an SBS was 48 minutes.

Revisiting normal (51)Cr-ethylenediaminetetraacetic acid clearance values in children.

PURPOSE: Normal (51)Cr-ethylenediaminetetraacetic acid (EDTA) clearance values as a function of age were published a number of years ago. These values were based on data from children with a normal left to right ratio and a normal appearance on DMSA scintigraphy, despite the presence of an acute renal infection. At that time, the authors were unaware that hyperfiltration is a common phenomenon in patients with acute renal infection and that their normal values could have been significantly overestimated. The present work therefore aimed to re-appraise these normal values. METHODS: In a first step, in order to verify the previous results, the same type of population was selected, namely patients with present or past urinary tract infection but normal images and a normal left to right ratio on DMSA scintigraphy. In a second step, the selection was based on patients who had had no recent urinary tract infection. In both series, a single blood sample method was used for the evaluation of (51)Cr-EDTA clearance. RESULTS: In the first group of patients, the results obtained were almost identical to those previously published. In the second group of patients, the results were significantly lower: after 2 years of age, the mean GFR value was 104 ml/min/1.73 m(2) (10th and 90th percentiles 81 and 135 ml/min/1.73 m(2), respectively), compared with 117 ml/min/1.73 m(2) in the first group. CONCLUSION: The data of the second group are probably more representative of the true normal GFR values and can be applied to the entire paediatric population.

Supranormal renal function in unilateral hydronephrosis: does it represent true hyperfunction?

The existence of supranormal differential renal function in unilateral hydronephrosis remains controversial. While some authors consider it as fact, others believe that it is just a technical artifact. Within our department, chromium-51 ethylene diamine tetra-acetic acid (Cr-EDTA) renal clearance is systematically performed in conjunction with technetium-99m mercaptoacetyltriglycine (MAG3) renograms to derive an absolute single kidney glomerular filtration rate (SKGFR). Our data allows us to ascertain whether supranormal differential renal function in unilateral hydronephrosis might be due to hypofunction of the contralateral kidney. Children with marked unilateral hydronephrosis were selected from a large database of MAG3 diuretic(s) renograms. We excluded patients with posterior urethral valves, duplex anomalies, neurogenic bladder, solitary kidney, and those who underwent any previous urological surgery. We also excluded children who had an early furosemide injection (F0 procedure), selecting only those having received furosemide at the end of the renogram (F+20 test). Seventy-three patients (92 renograms) fulfilled these criteria. Differential renal function was calculated using the integral method. Hydronephrotic kidney with a relative uptake > or =55% was defined as supranormal. Six renograms (four patients) demonstrated supranormal relative function on the hydronephrotic side. However, the SKGFR of these kidneys was in all cases within the range of normal values, while the contralateral side demonstrated borderline low SKGFR. Increased relative function on the side of the hydronephrotic kidney is relatively infrequent. When it occurs, it may be related to a borderline hypofunction of the contralateral kidney.

How to interpret a deterioration of split function?

OBJECTIVE: A drop of split renal function often constitutes a criterion for pyeloplasty in hydronephrosis since it is considered as representing deterioration of the affected kidney. The aim of this work was to determine, in a selected population of patients with a drop of split function of at least 5%, if the evolution of single kidney glomerular filtration rate (SKGFR) was parallel to the one of split renal function. METHODS: From a large data basis, we found retrospectively only 29 children (10 below and 19 above two years of age at first examination) having had at least two Tc-99m mertiatide (Tc-99m MAG3) renographic explorations for various urological diseases, with a decrease of split function of at least 5% between the two examinations. Evolution of split function was compared to evolution of SKGFR obtained by means of the combination of Tc-99m MAG3 split function and overall glomerular filtration rate as given by the chromium Cr 51 ethylenediamine tetraacetic acid (EDTA) clearance. RESULTS: For the group above two years of age, SKGFR increased or remained stable in 63% of the cases, while in the children less than 2 years of age, a decrease of SKGFR was never observed, according to the maturation of overall GFR in this age group. Thus, the decrease of split function was not necessarily associated with a similar decrease of SKGFR. CONCLUSION: In patients with unilateral or bilateral urological disorders, deterioration of split renal function does not necessary correspond to a loss of function of the affected kidney. SKGFR often modifies the interpretation of split function.

Optimised tracer-dependent dosage cards to obtain weight-independent effective doses.

PURPOSE: The aim of this study was twofold: firstly, to determine whether the European Association of Nuclear Medicine (EANM) dosage card results in weight-independent effective doses or weight-independent count rates; secondly, to determine whether one dosage card is sufficient for 95 different radiopharmaceuticals, and, if not, how many cards we reasonably need to take into account inter-tracer variability. METHODS: Normalisation factors for count rate and effective dose were calculated as a function of body weight, with 70 kg as standard. Calculations were performed, using whole-body absorption fractions and MIRDOSE 3 software, for seven anthropomorphic phantoms and ten radionuclides. An analytic function for both relations was proposed. Normalisation factors for effective dose for 95 radiopharmaceuticals were investigated using cluster analysis. RESULTS: Normalisation factors for count rate and effective dose can be estimated accurately as a function of body weight W by (W/70)a holding only one parameter, called the a value. The a values for 95 radiopharmaceuticals were classified into three clusters (nA=7, nB=76, nC=12). Cluster A contains tracers for renal studies. Cluster B contains all remaining tracers, except iodine-labelled tracers for thyroid studies and 89Sr for therapy, which belong to cluster C. CONCLUSION: Correction factors proposed by the EANM task group mainly correct for effective dose. They are very similar to the factors obtained for cluster A. Using the EANM factors for tracers belonging to clusters B and C results in significantly higher effective doses to children. We suggest using three tracer-dependent dosage cards for which the correction factors have been calculated to obtain weight-independent effective doses.

99mTc-MAG3 diuretic renography in children: a comparison between F0 and F+20.

The aim of this work was to compare the quality of renal drainage obtained with two well-described procedures of diuretic renography (F+20 and F0 tests). We selected 36 clinically stable children, aged 10 days to 17 years, with unilateral (25) or bilateral (11) hydronephrosis, in whom both F+20 and F0 tests were successively performed. In all cases, a late image (PM) was acquired after micturition and after changing the position of the patient. The following parameters were calculated: the time to the maximum of the basic renogram (Tmax); and the normalized residual activity (NORA) and output efficiency (OE) at the end of the 20 min renogram, at the end of the furosemide test (35 min) and on the PM image. In F+20, the renal drainage was better on the PM image than at the end of the diuretic renogram, whereas, in F0, the renal drainage was better on the PM image than at the end of the 20 min diuretic renogram. When comparing F0 and F+20, both OE and NORA parameters revealed slightly better drainage at the end of the 20 min F0 renogram than at the end of the 35 min F+20 diuretic renogram. The drainage obtained on the late post-voiding image was comparable for both F0 and F+20 tests. In conclusion, the quality of drainage obtained during the F+20 and F0 procedures can easily be compared using both OE and NORA. A very similar quality of drainage was reached for both procedures when considering only the PM image. This PM view remains mandatory irrespective of the timing of the furosemide injection and despite the use of tracers with a high extraction rate.

Calculation of renal retention function without deconvolution.

The aim of this study was to evaluate Rutland's method for the recovery of renal retention function without deconvolution. Renograms (n=5800) were generated by convolving 10 real input functions with 580 artificially created retention functions. Their ratios of minimal to mean transit time ranged from 0.1 to 1.0, and for mean transit time ranged from 3 to 60 min. The retention function was recovered from each renogram and its associated input function by calculating the first derivative of the residence time of the tracer in the kidney. Minimal, mean, and maximal transit time of the recovered retention function were calculated and compared with the original values. Qualitatively, the recovered retention function differed little from the original one. Quantitatively, values for recovered minimal transit time equalled original minimal transit time in all cases, whilst recovered mean transit time and maximal transit time equalled, respectively, the original mean transit time and maximal transit time if the original minimal to mean transit time ratio equalled 1. If this ratio was less than 1, recovered mean transit time was higher than original mean transit time and recovered maximal transit time was lower than original maximal transit time. For values of mean and maximal transit time, the differences from the original value increased with increasing original mean and maximal transit time, respectively, and with increasing renal clearance and decreasing minimal to mean transit time ratio. It is confirmed that Rutland's method is a particularly interesting alternative to deconvolution analysis. The errors that occur when recovering the retention function are relatively small.

Influence of early furosemide injection on the split renal function.

The split renal function, obtained using Technetium 99m mercaptoacetyltriglycine renography, is currently considered as a robust, accurate and reproducible parameter, provided that it is calculated at a time when no escape of the tracer from the kidney has occurred. The question arises as to whether the simultaneous administration of furosemide with the tracer (F0 test) might accelerate the escape of the tracer, resulting in an underestimation of the split renal function. From a large database, we selected 36 clinically stable children in whom both F0 and F+20 (administration of furosemide 20 min after the tracer) diuretic renography had been performed. In all cases, the F+20 test preceded the F0 test. The mean interval between the two tests was 17 months. The split renal function was calculated on the basis of the 1-2 min background-corrected renal activity using the integral method, slope method and Rutland-Patlak plot. In order to evaluate the effect on the split renal function of an early escape of the tracer, the patients were analysed according to the T(max) value of the renogram for both the F0 and F+20 tests. For the F+20 test, all T(max) values were more than 3 min. For the F0 test, the T(max) value was more than 3 min in 53 kidneys and less than 3 min in 19 kidneys (unilateral in all 19 patients). For the F0 test, for the kidneys with a T(max) value of less than 3 min, there was a tendency to underestimate the split renal function, taking as reference the split renal function observed in the F+20 test. This observation, however, was only statistically significant for the slope method (P=0.03). There was a tendency for lower values with the Rutland-Patlak plot (P=0.07), but, for the integral method, no difference was observed (P=0.5). In conclusion, the simultaneous administration of furosemide with the tracer induces an early acceleration of renal transit. This should be taken into account when calculating the split renal function, for example by favouring the integral method.

[Methodological aspects related to the determination of the relative renal function using 99mTC MAG3]. / Aspectos metodológicos relacionados con la determinación de la función renal relativa usando 99mTc MAG3.

UNLABELLED: The aim of the study was to evaluate three different methods for calculating the split renal function in patients with only one functioning kidney, keeping in mind that the split function should be zero on the side of the non-functioning kidney. PATIENTS: We retrospectively selected 28 99mTc MAG3 renograms performed in children, 12 with unilateral nephrectomy, 4 with unilateral agenesis and 12 with a non-functioning kidney. METHODS: A renal and perirenal region of interest (ROI) were delineated around the functioning kidney. The ROIs around the empty kidney were drawn symmetrically to the contralateral side. The split renal function was calculated using three different methods, the integral method, the slope method and the Patlak-Rutland algorithm. RESULTS: For the whole group of 28 kidneys as well as for the three categories of patients, the three methods provided a split function on the side of the non-functioning kidney close to the zero value, regardless of whether the empty kidney was the left or the right one. CONCLUSION: We recommend the use of the integral method for the whole range of split renal function with 99mTc MAG3. No significant improvement was obtained by means of the more sophisticated Patlak-Rutland method.

Aspectos metodológicos relacionados con la determinación de la función renal relativa usando 99mTc MAG3 / Methodological aspects related to the determination of the relative renal function using 99mTc MAG3

El propósito de este trabajo fue evaluar tres métodos distintos de cálculo de función renal relativa (FRR) en pacientes con un solo riñón funcionante, teniendo en cuenta que en el lado del riñón 'no funcionante' la función debiera ser cero. Pacientes: Seleccionamos retrospectivamente 28 renogramas 99mTc MAG3 realizados en niños: 12 con nefrectomía unilateral, 4 con agenesia unilateral, y 12 con un riñón 'no funcionante'. Método: Se dibujó un área de interés (ROI) renal, y otra de sustracción de fondo perirrenal, para cada riñón funcionante. Las ROI para el riñón 'no funcionante' se dibujaron simétricamente al lado contralateral. La FRR fue calculada usando 3 métodos: Integral, de las Pendientes y Patlak-Rutland. Resultados: Tanto para el grupo total de riñones como para cada uno de los tres subgrupos de pacientes, los tres métodos dieron resultados cercanos a cero al lado del riñón 'no funcionante', estuviera éste al lado izquierdo o derecho. Conclusión: Recomendamos el uso del método integral para el cálculo de amplios rangos de FRR con 99mTc MAG3.Ninguna mejoría significativa fue obtenida por medio del más sofisticado método de Patlak-Rutland (AU)

Is deconvolution applicable to renography?

The feasibility of deconvolution depends on many factors, but the technique cannot provide accurate results if the maximal transit time (MaxTT) is longer than the duration of the acquisition. This study evaluated whether, on the basis of a 20 min renogram, it is possible to predict in which cases the MaxTT will exceed 20 min. Renograms of various shapes were simulated by convolution of a plasma disappearance curve and various created retention functions with a mean transit time (MTT) ranging from 3 to 23 min. The values of MaxTT were then derived from the created curves and compared to three parameters of transit measured on the renograms: the time to reach the maximum of the curve (Tmax), the output efficiency at 20 min (OE20), and the normalized residual activity at 20 min (NORA20). The proportion of retention functions (n=390) with MaxTT>20 min increased with increasing Tmax (e.g. 9% for 6< or =Tmax<10 min, and 34% for 11< or =Tmax<15 min), increasing NORA20 (e.g. 20% for 1.4< or =NORA20<3.0, and 84% for 3.0< or =NORA20<5.0) and decreasing OE20 (19% for 50%

Treatment of children with acute pyelonephritis: a prospective randomized study.

The aim of this study was to compare, in children with acute pyelonephritis, the efficacy of 7 days' (group A) and 3 days' (group B) intravenous antibiotics, both followed by an oral treatment. Children were randomized after 3 days of intravenous treatment. Technetium-99m dimercaptosuccinic acid (DMSA) scintigraphy was performed within the first days after admission and repeated 6 months later. Total or partial persistence of renal abnormalities on the 6-month DMSA scintigraphy was used as the endpoint of the study. Among the 92 children included in the study, 87 were followed for at least 6 months (43 in group A and 44 in group B) and were eligible for analysis. Late DMSA was abnormal in 9 kidneys of group A and 12 kidneys of group B, representing respectively 24% and 44% of kidneys with abnormalities on the initial DMSA (difference statistically not significant). When the patients were stratified according to the delay of treatment, the percentage of patients with sequelae in group A was comparable, whether the delay was less or more than 1 week. In group B, the percentage of patients with sequelae was significantly higher (P<0.01) when the delay was more than 1 week.

Role of Tc-99m DMSA scintigraphy in the diagnosis of culture negative pyelonephritis.

The aim of this work was to evaluate prospectively the proportion of children with a clinical and biological presentation of acute pyelonephritis, abnormal Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy and negative or equivocal urine cultures. All patients aged 6 weeks to 15 years suspected of acute pyelonephritis (APN) were admitted to the Paediatric Department and underwent Tc-99m DMSA scintigraphy within 3 days after admission and at 6 months. Of 166 patients enrolled in the study, 15 (9%) had negative or equivocal urine culture despite clinical and scintigraphic evidence of APN. Of these 15 children, renal ultrasound was normal in 7 patients and vesicoureteric reflux was found in 9 patients. Control DMSA 6 months after acute episode showed the disappearance of cortical lesions in eight and partial improvement in four patients. In this prospective series, as many as 9% of patients with APN would have been missed on the basis of equivocal or negative urine cultures. It is suggested that Tc-99m DMSA scintigraphy should be performed in children with severe infection without clear aetiology, especially in those with abnormal urinalysis.