Antenatally detected hydronephrosis

Renogram image characteristics and the reproducibility of differential renal function measurement

PURPOSE

Patient factors such as age and glomerular filtration rate (GFR), have been implicated as causes for poor reproducibility of differential renal function (DRF) estimates on 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) renography. This study aims to investigate factors associated with the reproducibility of DRF measurements.

METHODS

The association between age, GFR and imaged derived image characteristics and reproducibility of repeated DRF estimates calculated using the area under the curve method and the Rutland Patlak method was analysed for cohort 1 (n = 127). The association between these variables and reproducibility of DRF was tested with univariate linear regression. The univariate linear regression results were used to plan the multiple linear regression combinations.The associations between variables identified and reproducibility of DRF values were then tested in a second cohort (n = 227).

RESULTS

The R2 values for goodness-to-fit for the multiple regression models ranged from 0.33 to 0.49 for cohort 1 and from 0.17 to 0.22 for cohort 2. Left kidney to background ratio (LKTBR) was significant in all the multiple linear regression combinations (P < 0.05). Right kidney to background ratio (RKTBR), right renal margins well defined, right renal margins poorly visualised, time visualisation right calyces and age were significant in most combinations. The reproducibility of DRF measurement was decreased when the kidney to background ratio (KTBR) was ≤2.

CONCLUSION

Only LKTBR, RKTBR, right renal margins well defined, time visualisation right calyces and age predicted reproducibility for the measurement of DRF on 99mTc-MAG3 renograms. The KTBR should be incorporated into the renal processing software as a quality control step. The DRF values should be interpreted with caution if the KTBR is ≤2.0.

Renal cortical transit time in the evaluation of prenatally detected presumed pelvi ureteric junction like obstruction: A systematic review

Introduction

Differentiating nonobstructive from obstructive dilatation of the kidney is a clinical dilemma in prenatally detected hydronephrosis. Many radionuclide renogram parameters have been used to differentiate obstructed from non-obstructed units, including cortical transit time (CTT). We evaluate the role of CTT in identifying obstruction through a systematic review.

Methods

A literature search of the MEDLINE, MEDLINE In-Process, and MEDLINE Epub Ahead of Print, EMBASE, Google scholar, Pub Med, and Cochrane Library was done using key words - radionuclide renogram, CTT, parenchymal transit time, cortical transit, renography to identify articles on the subject. The identified articles were assessed for appropriateness and reviewed.

Results

The initial search yielded a total of 1583 articles, after adding the articles from references and applying the inclusion and exclusion criteria a total of 28 articles were selected. CTT showed good inter observer agreement in identifying obstruction. The use of CTT as a single parameter for determining the need for surgery and to identify those kidneys which will have functional improvement after surgery has been evaluated and has been found to be useful. CTT is best used in conjunction with ultrasonography to make clinical decisions.

Conclusion

The commonly used visual method of estimating the CTT, is a promising parameter for the evaluation of prenatally detected pelviureteric junction obstruction. Further well-designed multicenter prospective studies are needed to establish it as the most specific parameter to differentiate obstructive from nonobstructive dilatation of the pelvicalyceal system.

Nuclear Medicine in Pediatric Nephro-Urology: An Overview

In the context of ante-natally diagnosed hydronephrosis, the vast majority of children with a dilated renal pelvis do not need any surgical treatment, as the dilatation resolves spontaneously with time. Slow drainage demonstrated at Tc-99m-mercaptoacetyltriglycine (MAG3) renography does not necessarily mean obstruction. Obstruction is defined as resistance to urinary outflow with urinary stasis at the level of the pelvic-ureteric junction (PUJ) which, if left untreated, will damage the kidney. Unfortunately this definition is retrospective and not clinically helpful. Therefore, the identification of the kidney at risk of losing function in an asymptomatic patient is a major research goal. In the context of renovascular hypertension a DMSA scan can be useful before and after revascularisation procedures (angioplasty or surgery) to assess for gain in kidney function. Renal calculi are increasingly frequent in children. Whilst the vast majority of patients with renal stones do not need functional imaging, DMSA scans with SPECT and a low dose limited CT can be very helpful in the case of complex renal calculi. Congenital renal anomalies such as duplex kidneys, horseshoe kidneys, crossed-fused kidneys and multi-cystic dysplastic kidneys greatly benefit from functional imaging to identify regional parenchymal function, thus directing further management. Positron emission tomography (PET) is being actively tested in genito-urinary malignancies. Encouraging initial reports suggest that F-18-fluorodeoxyglucose (FDG) PET is more sensitive than CT in the assessment of lymph nodal metastases in patients with genito-urinary sarcomas; an increased sensitivity in comparison to isotope bone scans for skeletal metastatic disease has also been reported. Further evaluation is necessary, especially with the promising advent of PET/MRI scanners. Nuclear Medicine in paediatric nephro-urology has stood the test of time and is opening up to new exciting developments.

Is urine intercellular adhesion molecule-1 a marker of renal disorder in children with ureteropelvic junction obstruction?

AIM

We aimed to investigate whether urine intercellular adhesion molecule-1 (ICAM-1) might serve as a marker of renal disorder in children with ureteropelvic junction obstruction.

MATERIAL AND METHODS

Twenty-nine children with severe hydronephrosis (HN) were compared with 23 participants with mild HN and with 19 healthy peers.

RESULTS

Urine ICAM-1/uCre levels were significantly higher in HN children than healthy controls (P<0.01), and in severe HN when compared with mild HN (p<0.05).

CONCLUSIONS

It seemed to us that uICAM-1 is a biomarker of renal disorder, and might have the potential to predict which patients will require surgery.

Optimizing functional MR urography: prime time for a 30-minutes-or-less fMRU

BACKGROUND

Current protocols for functional MR urography (fMRU) require long scan times, limiting its widespread use.

OBJECTIVE

Our goal was to use pre-defined criteria to reduce the number of sequences and thus the examination time without compromising the morphological and functional results.

MATERIALS AND METHODS

The standard fMRU protocol in our department consists of eight sequences, including a 17-min dynamic post-contrast scan. Ninety-nine children and young adults (43 male, 56 female, mean age 7 years) were evaluated with this protocol. Each sequence was retrospectively analyzed for its utility and factors that affect its duration.

RESULTS

Mean scan time to perform the eight sequences, without including the variable time between sequences, was 40.5 min. Five sequences were categorized as essential: (1) sagittal T2 for planning the oblique coronal plane, (2) axial T2 with fat saturation for the assessment of corticomedullary differentiation and parenchymal thickness, (3) coronal 3-D T2 with fat saturation for multiplanar and 3-D reconstructions, (4) pre-contrast coronal T1 with fat saturation to ensure an appropriate scan prior to injecting the contrast material and (5) the coronal post-contrast dynamic series. Functional information was obtained after 8 min of dynamic imaging in the majority of children. The coronal fat-saturated T2, coronal T1, and post-contrast sagittal fat-saturated T1 sequences did not provide additional information. Because of the effects of pelvicalyceal dilation and ureteropelvic angle on the renal transit time, prone position is recommended, at least in children with high-grade pelvicalyceal dilation.

CONCLUSION

Comprehensive fMRU requires approximately 19 min for sequence acquisition. Allowing for time between sequences and motion correction, the total study time can be reduced to about 30 min. Four pre-contrast sequences and a shortened post-contrast dynamic scan, optimally with the child in prone position, are sufficient.

Validation of IAEA software package for the analysis of scintigraphic renal dynamic studies: parameters of renal transit in children with renal pelvic dilatation

PURPOSE

The objectives of the study were to use the International Atomic Energy Agency (IAEA) software package for the analysis of scintigraphic renal dynamic studies to obtain values of curve parameters and excretory parameters in children with hydronephrosis and to validate the reliability of these numerical outputs by comparing with values established by consensus reports.

PATIENTS AND METHODS

Fifty children with hydronephrosis (median age, 16 months; 30 boys, 20 girls; 99 kidneys) underwent Tc-MAG3 diuresis renography. Studies were analyzed by 2 observers, and according to the assessment of images, renograms, and differential function, kidneys were classified as normal (42, kidneys contralateral to hydronephrotic kidney), hypotonic unobstructed (49), and obstructed (8). The IAEA software was applied to each renogram. The parameters analyzed were as follows: normalized residual activity at 20 minutes (NORA 20) and on postmicturition (PM) acquisition, output efficiency at 20 minute (OE 20), PM to maximum renal count ratio (PM/max), and mean transit time (MTT).

RESULTS

Mean values for normal, hypotonic unobstructed, and obstructed kidneys were as follows: NORA 20: 0.25, 0.57, and 2.16; OE 20 (%): 94.5, 87, and 57; normalized residual activity on PM acquisition: 0.02, 0.03, and 0.27; PM/max: 0.01, 0.02, and 0.13; and MTT (minutes): 1.9, 3.5, and 8.9, respectively. Difference between obstruction/dilatation and normal/dilatation was significant (P < 0.0001), as well as the correlation between NORA 20/OE 20 (R = -0.982). Cutoff values to predict obstruction were as follows: NORA 20, 1.6; OE 20, 73%; NORA PM, 0.11; PM/max, 0.06; and MTT, 8.23 minutes.

CONCLUSIONS

The IAEA software package gives reliable values of numerical parameters of renal excretion. The use of the software improves diagnostic accuracy of diuresis renography in children.

Chemokines as potential markers in pediatric renal diseases

Glomerular diseases and obstructive uropathies are the two most frequent causes of chronic kidney disease (CKD) in children. Recently, biomarkers have become a focus of clinical research as potentially useful diagnostic tools in pediatric renal diseases. Among several putative biomarkers, chemokines emerge as promising molecules since they play relevant roles in the pathophysiology of pediatric renal diseases. The evaluation of these inflammatory mediators might help in the management of diverse renal diseases in children and the detection of patients at high risk to develop CKD. The aim of this paper is to revise general aspects of chemokines and the potential link between chemokines and the most common pediatric renal diseases by including experimental and clinical evidence.

Interactions between cytokines, congenital anomalies of kidney and urinary tract and chronic kidney disease

Fetal hydronephrosis is the most common anomaly detected on antenatal ultrasound, affecting 1-5% of pregnancies. Postnatal investigation has the major aim in detecting infants with severe urinary tract obstruction and clinically significant urinary tract anomalies among the heterogeneous universe of patients. Congenital uropathies are frequent causes of pediatric chronic kidney disease (CKD). Imaging techniques clearly contribute to this purpose; however, sometimes, these exams are invasive, very expensive, and not sufficient to precisely define the best approach as well as the prognosis. Recently, biomarkers have become a focus of clinical research as potentially useful diagnostic tools in pediatric urological diseases. In this regard, recent studies suggest a role for cytokines and chemokines in the pathophysiology of CAKUT and for the progression to CKD. Some authors proposed that the evaluation of these inflammatory mediators might help the management of postnatal uropathies and the detection of patients with high risk to developed chronic kidney disease. Therefore, the aim of this paper is to revise general aspects of cytokines and the link between cytokines, CAKUT, and CKD by including experimental and clinical evidence.

Multicystic dysplastic kidney disease presenting with a single large cyst in a fetus-anatomical basis and radiological aspects

Multicystic dysplastic kidney (MCDK) is a congenital maldevelopment in which the renal cortex is characteristically replaced by numerous cysts of multiple sizes. MCDK presenting as a single predominant large cyst in morphology is less common. We report on the prenatal imaging findings and perinatal management of a fetus with MCDK unusually presenting as a single predominant large cyst, erroneously interpreted as a severe fetal hydronephrosis. Details of the perinatal history, radiological evaluation, morphological characteristic, and clinical aspect of this case are presented. We also discuss a few studies addressing the sensitivity of magnetic resonance urography for the prenatal diagnosis of MCDK.

Antenatal detection of pelviureteric junction stenosis: main controversies

Although renography has been used for half a century to evaluate the function of the infant kidney, there are still important disagreements among the specialists involved in this particular pathology. Each department of nuclear medicine has his own way to acquire and process a renogram; to interpret the obtained images, curves, and quantitative parameters; and to make recommendations for the referring physician. The urologist has his or her part of responsibilities because the decision for operating or not operating varies from one center to another and is generally determined by a series of unproven assumptions. The aim of the present work is to focus on the main controversies involving both the nuclear medicine physician and the urologist. Concerning the technique of renography. The bladder catheter, systematically recommended in different centers, can best be replaced in most of the cases by a much less-invasive procedure, namely the acquisition and processing of late postmicturition (PM) posterect images. The change of patient's position contributes strongly to the renal washout. Intravenous hydration is used to standardize the level of hydration. However, the patients, in most of the cases, are in good health, and adequate oral hydration is sufficient. Even if hydration was not ideal when the procedure began, the administration of furosemide and the late PM images will result in a very good drainage of a normal kidney. Any renal tracer with high extraction rate is adequate, but diethylene triamine pentaacetic acid ((99m)Tc-DTPA) does not allow a precise estimation of differential function in children younger than 6 months. The moment of furosemide injection (F0, F+20, F-15) does not influence the quality of the final renal washout, and the F0 procedure is recommended in cases of known hydronephrosis because it shortens the time of acquisition on the gamma camera and allows the simultaneous injection of both the tracer and the diuretic. Background correction remains controversial among nuclear medicine physicians. Including in the background area some liver and spleen activity, which are responsible for an important part of the extrarenal activity within the renal area, will improve the quality of the renogram curve, suppressing almost completely the initial vascular phase. The supporters of the Rutland-Patlak (R-P) fit for calculating differential function state that the vascular component is eliminated better than with use of the classical integral method. However, this method is based on a slope, with counting statistics being rather poor in infants with immature function. In most of the cases, the integral method will provide robust results. Determination of the same differential function by the use of both methods increases the level of confidence of the final results. It is generally admitted that the first renogram in children with antenatally detected hydronephrosis should be performed at approximately 1 month of age. However, there is a tendency to start earlier, and even in the first days of life, in case of huge hydronephrosis. The renogram should be repeated in case of significant hydronephrosis, significant increase of dilation, poor response to furosemide, or low initial differential function. Moderate dilation associated with normal differential function can probably be monitored by ultrasound alone. T(½) of the diuretic curve is an empiric parameter that does not take into account the bladder emptying and the change of patient's position. Output efficiency (OE) and normalized residual activity (NORA), measured on the late PM and posterect images, represent physiological parameters not dependent on the input function of the considered kidney and can be used whatever the moment of furosemide injection. There is presently no way to quantitatively measure cortical transit in antenatally detected pelviureteric junction syndrome; all methods are limited by the slight kidney motion related to respiratory movements and by the almost-complete superimposition between cortical area and collecting system. The best approach probably is a visual estimation. Concerning the position of the urologist. The main controversy is related to the definition of obstruction and the indication for surgery. Neither the degree of hydronephrosis nor the impairment of differential function and/or the quality of the response to furosemide can define which kidney is in danger of further deterioration. Alternatively, these parameters are unable to predict for which kidneys an improvement of differential function can be expected because of a pyeloplasty. It has not been excluded, according to recent published work, that cortical transit could be a better predictive factor of the risk of a conservative attitude or the benefits of a surgical procedure, but this procedure has still to be confirmed.

[Imaging evaluation of renal function: principles and limitations]

The kidney performs multiple functions. Glomerular filtration is the most studied of these functions. In clinical practice, the surgical indication for patients with unilateral uropathy is frequently based on the split renal function as demonstrated by scintigraphy. MRI is not yet validated as a technique but nonetheless offers an interesting non-radiating alternative to achieve both morphological and functional renal evaluation. Recent pulse sequences such as diffusion, arterial spin labeling, and blood oxygenation dependent imaging may also provide additional information. CT and US remain of limited value for the evaluation of renal function.

[Postnatal evaluation and management of fetal pyelectasis on prenatal ultrasound]

Fetal pyelectasis is the most frequently encountered anomaly on prenatal ultrasound. The ultrasound diagnostic criteria are well established: nature of dilated structures, degree of dilatation, ultrasound appearance of the kidneys, volume of amniotic fluid. Ultrasound can also determine if the anomaly is isolated or not, which is important for the management and prognosis of the pregnancy. Ultrasound is the initial postnatal study to evaluate the urinary tract. Further management will be based on suspected diagnosis. In cases of suspected vesico-ureteral reflux, VCUG is performed. In cases of obstructive uropathy or complex malformation (duplications), MRI is performed at 6 months of age to further define the anatomy of the urinary tract. Radionuclide renogram, performed in most cases, allows evaluation of split renal function. Follow-up ultrasound is important to monitor renal development, urinary tract dilatation and appearance of the renal parenchyma. Functional follow-up is assured by radionucline renography. This comprehensive follow-up is recommended to prevent complications and progressive loss of renal function.

Obstructive diseases of the urinary tract in children: lessons from the last 15 years

Imaging urinary tract obstruction is a common query in paediatric uroradiology. With the advent of a more conservative treatment approach, the task of imaging today is to distinguish as early as possible those kidneys that do not require surgery, from those that will deteriorate and lose function and/or growth potential and thus benefit from surgery. At present, in spite of significant advancements in imaging and the introduction of diuretic paediatric MR-urography, there is still no reliable a-priori pro-futuro assessment. Thus, repeated follow-up imaging is often necessary for monitoring. Imaging usually starts with US; the major additional complementary and more function-oriented tools are diuretic renal scintigraphy and MR-urography. The frequency and timing as well as the detailed protocol vary within institutions, partly because of differences in the criteria that are used for indicating surgery. Intra-venous urography (IVU) for obstruction has practically vanished apart from for a few exceptions, and the "Whitaker" test is today seldom performed, being reserved for complicated cases.

MR urography in children. Part 1: how we do the F0 technique

MR urography (MRU) has been widely accepted as a substitute to intravenous urography for investigating children with a dilated urinary tract after preliminary assessment by US and voiding cystourethrography. Hydronephrosis is by far the main indication for MRU because upper tract dilatation is a frequent condition in infants and children. Recent advances in technology have allowed MR to go beyond morphology and to assess renal function parameters such as split renal function and drainage. In this article we report our routine practice of the F0 MRU technique. The main advantages of our protocol are no requirement for general anaesthesia, no bladder catheterization, use of low-dose gadolinium-based contrast agent (0.05-0.1 mmol/kg) and total acquisition time of 30 min or less.