Renal diuretic duplex Doppler sonography in childhood hydronephrosis

OBJECTIVE: The purpose of this study was to determine the diagnostic value of diuretic duplex Doppler sonography in distinguishing between obstructive and nonobstructive hydronephrosis in children by calculating the resistive indices (RI) before and after administration of furosemide. MATERIAL AND METHODS: We prospectively evaluated 28 kidneys (2 solitary) in 15 patients with unilateral or bilateral neonatal hydronephrosis. All patients underwent diuretic renography and duplex Doppler sonography before and after administration of furosemide. RESULTS: According to the half-time drainage patterns at diuretic renography, 13 kidneys were classified as nonobstructed and 15 as obstructed. At baseline, the mean RI values of nonobstructed and obstructed kidneys were not significantly different (0.66 and 0.64, respectively). Ten minutes after the injection of furosemide, the mean RI values of the nonobstructed and obstructed kidneys were 0.68 and 0.70, respectively. The increase in RI over the baseline 10 min after the diuretic injection was statistically significant (p<0.00001) in the obstructed kidneys. CONCLUSION: The baseline RI value of 0.70 is not a definite value for distinguishing obstructed from nonobstructed systems. An increase in RI of at least 10% over the baseline seems to be a more reliable criterion, especially when it is used in conjunction with diuretic renography.     

Volume expanded diuretic renography in the postnatal assessment of suspected uretero-pelvic junction obstruction.

Controversy surrounds the role of 99mTc-diethylenetriamine pentaacetic acid renography in suspected uretero-pelvic junction obstruction in early life. Accordingly, we retrospectively reviewed 18 patients (28 hydronephrotic kidneys) with a mean age of 2 mo (range: 1 wk-6 mo) who underwent a total of 36 scans using intravenous volume expansion (10 ml/kg) and furosemide diuresis (1 mg/kg). Initial scans were classified as obstructed, not obstructed or indeterminate using differential renal function, furosemide washout T 1/2 and visual assessment of tracer clearance. Those initially classified as obstructed (n = 8) have been surgically confirmed. In the indeterminate (n = 6) and nonobstructed (n = 14) groups, three and two kidneys, respectively, developed obstruction on progress scans. Mean follow-up in the nonsurgical patients was approximately 9 mo (range: 4-17 mo). A total of 13 kidneys had developed obstruction by renographic criteria, and to date 12 have surgical confirmation. Our data indicate that: (1) scans classified as obstructed correlate well with surgery; (2) an initial classification of indeterminate or nonobstructed does not exclude later development of obstruction; and (3) serial scans correctly stratify children with possible uretero-pelvic junction obstruction.     

A software engine to justify the conclusions of an expert system for detecting renal obstruction on 99mTc-MAG3 scans.

The purposes of this study were to describe and evaluate a software engine to justify the conclusions reached by a renal expert system (RENEX) for assessing patients with suspected renal obstruction and to obtain from this evaluation new knowledge that can be incorporated into RENEX to attempt to improve diagnostic performance. METHODS: RENEX consists of 60 heuristic rules extracted from the rules used by a domain expert to generate the knowledge base and a forward-chaining inference engine to determine obstruction. The justification engine keeps track of the sequence of the rules that are instantiated to reach a conclusion. The interpreter can then request justification by clicking on the specific conclusion. The justification process then reports the English translation of all concatenated rules instantiated to reach that conclusion. The justification engine was evaluated with a prospective group of 60 patients (117 kidneys). After reviewing the standard renal mercaptoacetyltriglycine (MAG3) scans obtained before and after the administration of furosemide, a masked expert determined whether each kidney was obstructed, whether the results were equivocal, or whether the kidney was not obstructed and identified and ranked the main variables associated with each interpretation. Two parameters were then tabulated: the frequency with which the main variables associated with obstruction by the expert were also justified by RENEX and the frequency with which the justification rules provided by RENEX were deemed to be correct by the expert. Only when RENEX and the domain expert agreed on the diagnosis (87 kidneys) were the results used to test the justification. RESULTS: RENEX agreed with 91% (184/203) of the rules supplied by the expert for justifying the diagnosis. RENEX provided 103 additional rules justifying the diagnosis; the expert agreed that 102 (99%) were correct, although the rules were considered to be of secondary importance. CONCLUSION: We have described and evaluated a software engine to justify the conclusions of RENEX for detecting renal obstruction with MAG3 renal scans obtained before and after the administration of furosemide. This tool is expected to increase physician confidence in the interpretations provided by RENEX and to assist physicians and trainees in gaining a higher level of expertise.     

RENEX: an expert system for the interpretation of 99mTc-MAG3 scans to detect renal obstruction.

A renal expert system (RENEX) has been developed to assist physicians detect renal obstruction in patients undergoing pre- and postfurosemide 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) scans. RENEX uses quantitative parameters extracted from the dynamic renal scan data and heuristic rules in the form of a knowledge base (KB) obtained from expert interpreters to conclude whether a kidney is obstructed. METHODS: Normal limits were established for 47 quantitative parameters extracted from the 99mTc-MAG3 scans of 100 potential renal donors. From these data the domain expert estimated 5 boundary conditions for each parameter: (i) definitely abnormal, (ii) probably abnormal, (iii) equivocal, (iv) probably normal, and (v) definitely normal. A sigmoid-type curve was then generated from these 5 boundary conditions, creating a parameter knowledge library used for converting the value of a prospective patient's individual quantitative parameters to a certainty factor (CF). Sixty heuristic rules were extracted from the domain expert to generate the KB for detecting obstruction. A forward-chaining inference engine was developed using the MYCIN combinatories (an approximation of Bayes theorem) to determine obstruction. A justification engine was implemented, which recorded the sequence of each rule that was fired and the current CF value of all input and output parameters at the time of instantiation to track and justify the logic of the conclusions. The entire system was fine tuned and tested using a pilot group of 32 patients (11 males, 21 females; mean age, 56.8 +/- 17.2 y; 63 kidneys) deemed by an expert panel to have 41 unobstructed kidneys, 13 obstructed kidneys,and 9 equivocal findings. RESULTS: RENEX agreed with the expert panel in 92% (12/13) of the obstructed kidneys, 93% (38/41) of the unobstructed kidneys, and 78% (7/9) of the kidneys interpreted as equivocal for obstructions. Processing time per patient was practically instantaneous using a 3.0-GHz personal computer programmed using interactive data language. CONCLUSION: We have developed a renal expert system for detecting renal obstruction using pre- and postfurosemide 99mTc-MAG3 renal scans, at a standardized expert level. These encouraging preliminary results warrant a prospective study in a large population of patients with and without renal obstruction to establish the diagnostic performance of this system.     

Duplex Doppler US of the kidney: differentiation of obstructive from nonobstructive dilatation

Distinction of the obstructed from the nonobstructed dilated renal collecting system is a difficult problem often requiring interventional procedures and pressure measurements. The authors prospectively performed duplex Doppler ultrasound (US) evaluations in 21 kidneys (obstructed, n = 14; nonobstructed, n = 7) immediately before percutaneous nephrostomy. In addition, ten of the obstructed kidneys were evaluated with follow-up Doppler US after percutaneous nephrostomy. Renal obstruction caused a change in the Doppler waveform detected by means of the resistive index (RI). Thirteen of the 14 obstructed kidneys had a RI value greater than .70, while none of the nonobstructed kidneys had a RI value exceeding .70. Relief of the obstruction resulted in a reduced RI; in nine of ten kidneys, the RI was less than or equal to .70 (similar to that of the nonobstructed kidneys). When a dilated collecting system is being imaged, additional evaluation with duplex Doppler US may help distinguish obstructed from nonobstructed dilatation, which may be of particular benefit in patients with conditions that usually predispose them to collecting system dilatation.     

Resistive Index in Rabbits with Experimentally Induced Hydronephrosis: Effect of Furosemide

RATIONALE AND OBJECTIVES: The purpose of this study in rabbits was to evaluate the effect of furosemide on resistive index (RI) in the diagnosis of partial hydronephrosis. MATERIALS AND METHODS: In 14 rabbits the left ureter was ligated by being tied to an angiographic guide wire. Doppler sonography was performed before and 1 and 6 hours, 1 and 3 days, and 1, 2, and 4 weeks after ureteral ligation. At each interval it was performed both before and after intravenous injection of saline and furosemide. RIs were compared (a) between obstructed and contralateral kidneys and (b) before and after furosemide administration, and the statistical significance of any differences was determined. RESULTS: Obstructed kidneys had significantly higher RIs than the contralateral kidneys before furosemide administration at five of seven postligation measurements and after furosemide administration at all seven. The differences between obstructed and contralateral kidneys were significantly higher after furosemide administration (P < .05). The increase in RI after furosemide administration was significantly greater in obstructed than in contralateral kidneys (P < .05). CONCLUSION: The results in a rabbit model indicate that Doppler sonography with furosemide administration is a valuable method for evaluating hydronephrosis. The administration of furosemide accentuates the difference in RI between obstructed and nonobstructed kidneys.     

iRENEX: a clinically informed decision support system for the interpretation of 99mTc-MAG3 scans to detect renal obstruction

Purpose

Decision support systems for imaging analysis and interpretation are rapidly being developed and will have an increasing impact on the practice of medicine. RENEX is a renal expert system to assist physicians evaluate suspected obstruction in patients undergoing mercaptoacetyltriglycine (MAG3) renography. RENEX uses quantitative parameters extracted from the dynamic renal scan data using QuantEM?II and heuristic rules in the form of a knowledge base gleaned from experts to determine if a kidney is obstructed; however, RENEX does not have access to and could not consider the clinical information available to diagnosticians interpreting these studies. We designed and implemented a methodology to incorporate clinical information into RENEX, implemented motion detection and evaluated this new comprehensive system (iRENEX) in a pilot group of 51 renal patients.

Methods

To reach a conclusion as to whether a kidney is obstructed, 56 new clinical rules were added to the previously reported 60 rules used to interpret quantitative MAG3 parameters. All the clinical rules were implemented after iRENEX reached a conclusion on obstruction based on the quantitative MAG3 parameters, and the evidence of obstruction was then modified by the new clinical rules. iRENEX consisted of a library to translate parameter values to certainty factors, a knowledge base with 116 heuristic interpretation rules, a forward chaining inference engine to determine obstruction and a justification engine. A clinical database was developed containing patient histories and imaging report data obtained from the hospital information system associated with the pertinent MAG3 studies. The system was fine-tuned and tested using a pilot group of 51 patients (21 men, mean age 58.2?±?17.1?years, 100 kidneys) deemed by an expert panel to have 61 unobstructed and 39 obstructed kidneys.

Results

iRENEX, using only quantitative MAG3 data agreed with the expert panel in 87?% (34/39) of obstructed and 90?% (55/61) of unobstructed kidneys. iRENEX, using both quantitative and clinical data agreed with the expert panel in 95?% (37/39) of obstructed and 92?% (56/61) of unobstructed kidneys. The clinical information significantly (p?Conclusion Our renal expert system for detecting renal obstruction has been substantially expanded to incorporate the clinical information available to physicians as well as advanced quality control features and was shown to interpret renal studies in a pilot group at a standardized expert level. These encouraging results warrant a prospective study in a large population of patients with and without renal obstruction to establish the diagnostic performance of iRENEX.     

F+0 diuresis renography in infants and children.

The purpose of this study was to evaluate the feasibility of modifying diuresis renography by the simultaneous administration of 99mTc-mercaptoacetyltriglycine (MAG3) and furosemide in the investigation of hydronephrosis and hydroureteronephrosis in infants and children. Two parameters were assessed: the diuretic response in normal kidneys and the ability of the F+0 study to differentiate between renal obstruction and nonobstruction and to identify the level of obstruction in cases of renal obstruction. METHODS: Seventy-two patients (48 males, 24 females; age 2 d to 7 y; median age 6 wk) with sonographic diagnoses of hydronephrosis or hydroureteronephrosis were reviewed prospectively over a 3-y period. All patients had prior sonographic studies and micturating cystourethrography. Bladder catheterization was not routinely performed and was undertaken only if the child had suspected vesicoureteric junction (VUJ) obstruction or grade II or more vesicoureteric reflux. A weight-adjusted dose of 99mTc-MAG3 (maximum 200 MBq, minimum 20 MBq) and 1 mg/kg of furosemide (maximum 40 mg) were administered intravenously at the same time. Posterior imaging of the kidneys and bladder was performed for 20 min and followed by gravity-assisted drainage or imaging after voiding. All patients were followed-up for 6-12 mo, and the final diagnoses were based on either surgery or conservative management with repeated sonography or follow-up 99mTc-MAG3 studies (or both). The results of the F+0 diuresis renography were then compared with the final diagnoses. RESULTS: A renal unit was defined as a kidney and its ureter. There were 151 renal units with 1 patient having bilateral duplex kidneys, 6 patients having unilateral duplex kidneys and 1 patient having a solitary kidney. Fifty-five normal renal units and 96 abnormal renal units on the basis of sonographic findings were assessed. The furosemide clearance half-time for the 55 normal renal units was 1.3-6.3 min (mean 3.8 min). Of the 96 abnormal renal units, 53 were classified as nonobstructed and 43 were classified as obstructed. Of the 53 renal units classified as nonobstructed, there were 48 true-negative studies and 5 false-negative studies; of the 43 renal units classified as obstructed, there were 40 true-positive studies and 3 false-positive studies. The sensitivity was 88.9%, specificity was 94.1% and accuracy was 91.7%. The level of obstruction, either pelviureteric junction or VUJ, was also correctly identified. CONCLUSION: F+0 diuresis renography shows excellent diuretic responses in normal kidneys and is a valid method for the investigation of hydronephrosis and hydroureteronephrosis in infants and children.     

Evaluation of dilated upper renal tracts by technetium-99m ethylenedicysteine f+0 diuresis renography in infants and children

AIM: To evaluate the feasibility of modifying diuresis renography by the simultaneous administration of Tc-99m ethylenedicysteine and furosemide in the investigation of hydronephrosis and hydroureteronephrosis in infants and children. Parameters assessed were the diuretic response in normal kidneys and the ability of the F+0 study to differentiate between renal obstruction and nonobstruction. METHODS: One hundred and thirty-three children (93 males, 40 females; mean age 35.2 months) with sonographic diagnoses of hydronephrosis or hydroureteronephrosis underwent F+0 diuresis renography. Tc-99m ethylenedicysteine (3.7 MBq/kg body weight) and furosemide at an appropriate dose were administered intravenously at the start of the study. Posterior imaging of the kidneys and bladder was performed for 20 min followed by imaging after voiding. All patients were followed-up for 12 months, and the results of the initial F+0 diuresis renography were compared with the final diagnoses. Final diagnosis was based on the pediatric urologist's decision of either surgery or conservative management. RESULTS: A renal unit was defined as a kidney and its ureter. There were 262 renal units with 4 patients having a solitary kidney. 90 normal and 172 abnormal renal units on sonography were assessed by F+0 diuresis renography. The furosemide clearance half time for the 90 normal renal units was 5.8 +/- 1.4 min. Of the 172 abnormal renal units, 100 were classified as nonobstructed and 72 as obstructed on diuresis renography. All 100 nonobstructed renal units were correctly classified with no false-negative studies; of the 72 renal units classified as obstructed, there were 43 true-positive studies and 29 false-positive studies. The sensitivity was 100%, specificity was 78% and accuracy was 83%. CONCLUSION: Tc-99m ethylenedicysteine F+0 diuresis renography is a valid method for the investigation of hydronephrosis and hydroureteronephrosis in infants and children.     

Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 2, anatomic and functional assessment of uteropelvic junction obstruction

OBJECTIVE: The purpose of our study was to retrospectively review our experience using MR urography in the diagnosis of ureteropelvic junction (UPJ) obstruction in children. MATERIALS AND METHODS: Sixty-one studies were performed in 50 children with hydronephrosis but without hydroureter. Anatomic criteria assessed included degree of hydronephrosis, morphology of the renal pelvis, atrophy of medulla, swirling contrast material, fluid levels, and the presence of fetal folds and crossing vessels. Functional criteria included renal transit time, differential renal function, and time-intensity curves when available. RESULTS: Thirty-one kidneys were classified as obstructed, 15 as equivocal, and 15 as nonobstructed. Obstructed systems had more marked hydronephrosis, more extensive medullary atrophy, more fluid levels, and more swirling contrast material. Fetal folds were seen in only the equivocal and nonobstructed groups. Crossing vessels were seen in all groups. Obstructed systems also showed greater functional derangement, decreased split renal function, and abnormal time-intensity curves. CONCLUSION: MR urography provides both excellent anatomic and functional information in children with UPJ obstruction in a single test that does not use ionizing radiation. MR urography may lead to greater understanding of the pathophysiology of UPJ obstruction.     

Increasing the dose of furosemide in patients with azotemia and suspected obstruction

Diuresis renography is widely used to distinguish obstructed from nonobstructed kidneys; however, the delivery of furosemide to its site of action in the loop of Henle is impaired in patients with azotemia. Consequently, the standard adult dose of 40 mg furosemide could be insufficient to generate an adequate diuretic response. This problem is illustrated by a patient with azotemia with bilateral nephrostomies who underwent Tc-99m MAG3 (mercaptoacetyltriglycine) diuresis renography with 40 mg furosemide to determine if his bilateral ureteral obstruction had resolved. The study showed findings typical for obstruction despite the fact that the patient could not have been obstructed because the nephrostomy tubes had not been clamped. When the study was repeated 6 days later with 80 mg furosemide and clamped nephrostomy tubes, there was good drainage bilaterally excluding obstruction. The nephrostomy tubes were removed and the patient's creatinine has subsequently remained stable for 3 years. In summary, this report illustrates the rationale for increasing the dose of furosemide in patients with azotemia referred for diuresis renography and shows how increasing the dose of furosemide could improve the diuretic response and minimize false-positive or indeterminate results.     

Renal transplant pyelocaliectasis: role of duplex Doppler US in evaluation

To distinguish the obstructed from the nonobstructed dilated collecting system of transplanted kidneys without interventional diagnostic measures, the authors prospectively evaluated duplex Doppler analysis (determination of resistive index [RI]) in 35 renal transplant patients with pyelocaliectasis. Proof of the presence or absence of obstruction was obtained at interventional procedures in 18 patients and at clinical follow-up in 17. Thirteen kidneys were obstructed (mean RI, .81 +/- .06), while 22 had nonobstructive dilatation (mean RI, .66 +/- .07). The RI difference was statistically significant (P less than or equal to .01). Of 21 kidneys with a normal RI, only two had obstruction. In both of these, the obstruction was associated with a significant peritransplant collection of fluid due to a ureteral leak. In the seven obstructed transplanted kidneys with follow-up, the mean RI was .82 +/- .06 before nephrostomy and .67 +/- .05 after nephrostomy. Obstruction was a common cause of an elevated RI (greater than or equal to .75). Other causes of transplant dysfunction can be associated with an elevated RI and nonobstructed dilatation. More important, a normal RI should strongly argue against obstruction unless a ureteral leak is also present.     

Renal transit time with MR urography in children

PURPOSE: To prospectively evaluate use of dynamic contrast material-enhanced magnetic resonance (MR) urography for measurement of renal transit time (RTT) of a contrast agent through the kidney and collecting system so as to identify obstructive uropathy in children. MATERIALS AND METHODS: One hundred twenty-six children suspected of having hydronephrosis were hydrated prior to undergoing both conventional and dynamic contrast-enhanced MR urography of the kidneys and urinary tract. A three-dimensional sequence was used to track passage of contrast agent through the kidneys. Time between the appearance of contrast material in the kidney and its appearance in the ureter at or below the level of the lower pole of the kidney was defined as RTT. Bland-Altman plots were used to quantify intra- and interobserver performance. In 30 children, a nuclear medicine renogram was also obtained, and the half-life of renal signal decay after furosemide administration was derived and compared with the MR imaging RTT by using receiver operating characteristic curves. RESULTS: On the basis of RTT, kidneys were classified as normal (RTT RTT 490 seconds). Inter- and intraobserver agreement indicated that the technique is both robust and reproducible. Receiver operating characteristic analysis for comparison of results of MR imaging and diuretic renal scintigraphy showed good agreement between the modalities, with a mean area under the curve of 0.90. CONCLUSION: When used in conjunction with morphologic images obtained in the same examination, RTT generally allowed normal kidneys to be differentiated from obstructed and partially obstructed kidneys.     

Obstructive nephropathy: evaluation with dynamic Gd-DTPA-enhanced MR imaging

The potential of dynamic gadolinium diethylenetriaminepentaacetic acid (DTPA)-enhanced magnetic resonance (MR) imaging for the examination of obstructive nephropathy was analyzed in 27 subjects (five healthy subjects, seven patients with dilated nonobstructed kidneys, six patients with acute obstruction, and nine patients with chronic obstruction) with use of a 1.5-T magnet. Morphologic findings were compared with quantitative analysis of temporal changes in signal intensity. Dynamic postcontrast images of the normal kidney demonstrated four phases of enhancement; cortical enhancement phase, early tubular phase, ductal phase, and excretory phase. The pattern of enhancement in dilated nonobstructed kidneys was similar to that in normal kidneys. In acutely obstructed kidneys, cortical enhancement was similar to that in normal kidneys (17% increase), but medullary enhancement was higher than normal, resulting in diminished corticomedullary differentiation. The early tubular phase was prolonged (until 2.5 minutes after injection), with delayed appearance of the ductal and excretory phases. In chronically obstructed kidneys, the increase in cortical intensity was less than that in normal kidneys (13% increase). The early tubular phase was prolonged, and the ductal phase was diminished or absent.     

Evaluation of thoracic abnormalities on 64-row multi-detector row CT: comparison between axial images versus coronal reformations

PURPOSE: To evaluate the capability of coronal reformations of chest on 64-row MDCT in demonstrating thoracic abnormalities in comparison with axial images. MATERIALS AND METHODS: Thirty-eight consecutive patients who underwent pulmonary CTA on 64-row MDCT were retrospectively studied with institutional review board (IRB) approval. Contiguous 2 mm axial and coronal images were reviewed independently with a 1-week interval, by consensus reading of two board-certified radiologists. Overall image quality was graded using a five-point scale. Abnormalities in mediastinum, hilum, pulmonary vessels, aorta, heart, esophagus, pleura, chest wall, and lung parenchyma were scored: 1 = definitely absent, 2 = probably absent, 3 = equivocal, 4 = probably present, 5 = definitely present. Scores on axial and coronal images were compared using weighted kappa analysis. RESULTS: Overall image quality was not different with statistical relevance between axial and coronal images (mean/median scores; 3.7/4; 3.6/4, respectively, P = 0.286, Wilcoxon signed-rank test). Significant agreement was observed between axial and coronal scores (mean weighted kappa, 0.661; range, 0.362-1). Agreement was almost perfect for pneumothorax, lung and pleural mass, effusion and consolidation (weighted kappa=0.833-1); substantial for pulmonary embolism, trachea, mediastinal lymphadenopathy and non-skeletal chest wall lesion, heart, esophagus, and emphysema (weighted kappa, 0.618-0.799); moderate for atelectasis, mediastinum, hilar nodes, aorta, other lung lesions, skeletal chest wall lesions, linear scarring, nodules > 1 cm, pulmonary artery abnormalities and pleural thickening (weighted kappa, 0.405-0.592); and fair for nodules < 1 cm (weighted kappa = 0.362). CONCLUSION: Coronal reformations on 64-row MDCT had substantial agreement with axial images for evaluation of the majority of thoracic abnormalities.     

Distinction between obstructive and nonobstructive pyelocaliectasis with duplex Doppler sonography

Because animal studies have shown that renal obstruction increases renal vascular resistance, we theorized that obstruction would change the Doppler waveform. We studied the value of the resistive index (RI) calculated from the duplex Doppler waveform to distinguish between obstructive and nonobstructive pyelocaliectasis in 229 kidneys in 133 patients. The RI is the peak systolic frequency shift minus the minimum diastolic frequency shift, then divided by the peak systolic frequency shift. Duplex Doppler sonography was performed prospectively in 70 kidneys with pyelocaliectasis before the presence or absence of obstruction was established. In 54 of 70 kidneys, the presence or absence of obstruction was proved by interventional methods (percutaneous nephrostomy, antegrade or retrograde pyelography, loopography), and in the rest it was proved by body CT, excretory urography, or surgery. Thirty-eight kidneys were found to be obstructed, and 32 had nonobstructive dilatation. In addition, 159 kidneys without pyelocaliectasis were studied to identify possible limitations of Doppler sonography in the diagnosis of obstruction. Clinical history and laboratory data were used to determine that 109 of these kidneys were in normal subjects and 50 were in patients with nondilated renal disease. There was a significant difference between the mean RI of the obstructed (0.77 +/- 0.05) and the nonobstructed dilated (0.63 +/- 0.06) kidneys (p less than .01). Analysis of the receiver-operating-characteristic curve showed an RI of 0.70 to be a good discriminatory level for obstruction, resulting in a sensitivity of 92%, a specificity of 88%, and an accuracy of 90%. All 109 normal kidneys had an RI less than 0.70. Over half (27/50) of the kidneys in patients with nondilated renal disease had an elevated RI (greater than or equal to 0.70). Ninety-six patients had Doppler examinations on both kidneys, and in only six patients did the RI values of each kidney differ by more than 0.10; all six were proved to have unilateral obstruction. Use of duplex Doppler sonography should improve the specificity, and thus the accuracy, of sonography in the noninvasive diagnosis of obstruction and should be used when a dilated collecting system is identified.     

Volume expansion diuretic renal scan in urinary tract obstruction

The diuretic renal scan is used to differentiate the obstructed dilated urinary system from the nonobstructed dilated system. The technique, however, has a false-positive and indeterminate rate of 10%-15%. This usually is due to variables such as the degree of dilatation of the pelvicalyceal system or ureter, the degree of bladder distention, the diuretic dose, and the state of hydration. We developed the volume expansion diuretic renal scan (VEDRS) to overcome these variables and to improve the accuracy of the technique. Twelve patients who had obstructive patterns on the diuretic renal scan were evaluated. Ten patients were shown to be dilated but not obstructed. Two patients were confirmed as obstructed. This technique improves the accuracy of the diuretic renal scan.     

F+0 renography in neonates and infants younger than 6 months: an accurate method to diagnose severe obstructive uropathy.

We studied the response to F+0 renography and the relative and absolute individual kidney function in neonates and < 6-mo-old infants before and after surgery for unilateral ureteropelvic junction obstruction (UJO). METHODS: The results obtained at diagnosis and after pyeloplasty for 9 children (8 boys, 1 girl; age range, 0.8-5.9 mo; mean age +/- SD, 2.4 +/- 1.5 mo) with proven unilateral UJO (i.e., affected kidney [AK]) and an unremarkable contralateral kidney (i.e., normal kidney [NK]) were evaluated and compared with a control group of 10 children (6 boys, 4 girls; age range, 0.8-2.8 mo; mean age, 1.5 +/- 0.7 mo) selected because of symmetric renal function, absence of vesicoureteral reflux or infection, and an initially dilated but not obstructed renal pelvis as proven by follow-up. Renography was performed for 20 min after injection of (123)I-hippuran (OIH) (0.5-1.0 MBq/kg) immediately followed by furosemide (1 mg/kg). The relative and absolute renal functions and the response to furosemide were measured on background-subtracted and depth-corrected renograms. The response to furosemide was quantified by an elimination index (EI), defined as the ratio of the 3- to 20-min activities: An EI > or = 3 was considered definitively normal and an EI < or = 1 definitively abnormal. If EI was equivocal (1 < EI < 3), the response to gravity-assisted drainage was used to differentiate AKs from NKs. Absolute separate renal function was measured by an accumulation index (AI), defined as the percentage of (123)I-OIH (%ID) extracted by the kidney 30-90 s after maximal cardiac activity. RESULTS: All AKs had definitively abnormal EIs at diagnosis (mean, 0.56 +/- 0.12) and were significantly lower than the EIs of the NKs (mean, 3.24 +/- 1.88) and of the 20 control kidneys (mean, 3.81 +/- 1.97; P < 0.001). The EIs of the AKs significantly improved (mean, 2.81 +/- 0.64; P < 0.05) after pyeloplasty. At diagnosis, the AIs of the AKs were significantly lower (mean, 6.31 +/- 2.33 %ID) than the AIs of the NKs (mean, 9.43 +/- 1.12 %ID) and of the control kidneys (mean, 9.05 +/- 1.17 %ID; P < 0.05). The AIs of the AKs increased at follow-up (mean, 7.81 +/- 2.23 %ID) but remained lower than those of the NKs (mean, 10.75 +/- 1.35 %ID; P < 0.05). CONCLUSION: In neonates and infants younger than 6 mo, (123)I-OIH renography with early furosemide injection (F+0) allowed us to reliably diagnose AKs and to determine if parenchymal function was normal or impaired and if it improved after surgery.     

Comparison of three different diuretic renal scintigraphy protocols in patients with dilated upper urinary tracts

PURPOSE: To compare 3 different diuretic renal scintigraphy protocols in patients with dilated upper urinary tract. MATERIALS AND METHODS: Three diuresis renography protocols were performed in 22 adult patients (28 kidneys) with upper urinary tract dilatation. The diuretic was given 20 minutes after (F+20), at the same time as (F+0), and 15 minutes before (F-15) radionuclide administration. The mean age was 29.8 years (range, 18-43 years). The 3 protocols were identical, except for the time of injection of furosemide. The F+0 protocol could not be performed in 1 and F-15 in 2 of the patients. Each of the 3 protocols was performed for the rest of the patients. The results were classified as nonobstructive, equivocal, and obstructive according to the renogram images and curves. RESULTS: None of the patients showed equivocal results in both F+0 and F-15 protocols. In the F+20 studies, 7 of the 28 kidneys were evaluated as equivocal. Of these, 5 kidneys showed nonobstructive and 2 kidneys revealed obstructive renogram patterns with the other 2 protocols (F+0 and F-15). Moreover, one kidney, which was evaluated as nonobstructive in the F+20 protocol, showed an obstructive pattern in both F+0 and F-15 protocols. All of the kidneys showing obstructive patterns in the F+20 study also revealed obstruction in the F+0 and F-15 investigations. We could not find any difference between the renogram patterns of F+0 and F-15 investigations. CONCLUSIONS: F+0 and F-15 protocols allow clarification in cases of equivocal F+20 studies. Because the F+0 study is more practical and shorter, we suggest the F+0 method when equivocal results are obtained by an F+20 study or as a single test when there is only one opportunity to confirm or exclude the presence of obstruction.     

How accurate is ultrasonography in detecting hydronephrosis in azotemic patients?

Screening for hydronephrosis continues to be an essential part of the evaluation of patients with azotemia of unknown cause. To determine whether sonography is as reliable as nephrotomography for screening purposes, we carried out a prospective, comparative study. Sixty-two patients were evaluated. Mean serum creatinine was 4.3 mg/dl. Of 116 kidneys, 45 were obstructed according to urographic criteria and 42 of these were correctly called hydronephrotic by sonography. The 3 false negative sonographic studies occurred in 2 patients. All 3 kidneys contained radiopaque calculi visible on the plain abdominal film. Of the 71 nonobstructed kidneys, 5 were mistakenly called hydronephrotic by ultrasound, giving a false positive rate of 7%. We believe it is appropriate to use gray-scale ultrasound as a screening test for urinary obstruction in azotemic patients providing the plain abdominal radiograph shows no calcifications.