Acute obstruction of the renal collecting system: the intrarenal resistive index is a useful yet time-dependent parameter for diagnosis

WITHDRAWN: Impact on Delayed Graft Function of the Renal Resistive Index in the Immediate Postoperative Period After Kidney Transplantation: A Cohort Analysis

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Renal intraparenchymal resistive index: the ultrasonographic answer to many clinical questions

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

Urolithiasis in pregnancy

Clinicians are faced with multiple diagnostic and treatment challenges when managing pregnant women with urolithiasis. Anatomical and physiological changes during pregnancy have to be taken into account whilst simultaneously considering both the expectant mother and the foetus. Ultrasonography remains the first-choice imaging modality, notwithstanding its potentially poor diagnostic accuracy. There is currently no consensus on second-line investigation for suspected urolithiasis. Low-dose non-contrast CT is highly sensitive, but the long-term effects of ionizing radiation on the foetus remain unknown. As far as treatment is concerned, expectant therapy is the primary option for management in the majority of cases. Percutaneous nephrostomy or ureteric stent placements are safe temporizing measures in relieving an acutely obstructed system and should be expedited in the presence of sepsis. Studies have shown ureteroscopy to be safe and effective during pregnancy with no significant risk to the foetus. It is important for the clinician to explain clearly the risks associated with the investigation and management options to the pregnant patient, including an acknowledgement that some of these remain unquantified, or even unknown.

Resistive intrarenal index: myth or reality?

In renal diagnosis, the B-mode ultrasound is used to provide an accurate study of the renal morphology, whereas the colour and power Doppler are of strategic importance in providing qualitative and quantitative information about the renal vasculature, which can also be obtained through the assessment of the resistive index (RI). To date, this is one of the most sensitive parameters in the study of kidney diseases and allows us to quantify the changes in renal plasma flow. If a proper Doppler ultrasound examination is carried out and a critical analysis of the values obtained is performed, the RI measurement at the interlobar artery level has been suggested in the differential diagnosis between nephropathies. The aim of this review is to highlight the pathological conditions in which the study of intrarenal RI provides useful information about the pathophysiology of renal diseases in both the native and the transplanted kidneys.

The renal resistive index as a predictor of acute hydronephrosis in patients with renal colic

INTRODUCTION

The objective of this study was to determine whether the renal resistive index (RI) can predict hydronephrosis in patients with renal colic (RC) and whether or not its performance is time-dependent.

MATERIALS AND METHODS

The study population was composed of 54 patients admitted for unilateral RC. At the time of the first observation (time point I, tpI), each patient underwent routine examinations, abdominal ultrasonography, and renal color Doppler ultrasound (CDUS) with measurement of the RI. The two imaging studies were repeated 6, 12, 18, 24, 36, and 48 h later (tpII, tpIII, tpIV, tpV, tpVI, tpVII). In addition, each patient underwent non-contrast urinary tract CT 48-60 h after admission. A mean renal RI of >0.70 (mRI+) for the symptomatic kidney was considered indicative of obstruction. Patients were retrospectively divided into two groups: those who developed dilatation (group A) and those who did not (group B).

RESULTS

A mRI+ on CDUS predicted the onset of hydronephrosis with 100% sensitivity, 84% specificity, 92.6% accuracy, PPV and NPV of 87.9% and 100%, and diagnostic efficiency of 84%. In group A, mRI+ were always observed before onset of hydronephrosis in a time-dependent manner. In group B, mRI+ were observed occasionally in 4/25 patients (16%) and all were recorded at tpII. In these cases, the RI had returned to normal by tpIII.

CONCLUSIONS

In our RC patients, renal RI obtained with CDUS predicted the onset of acute dilatation with higher sensitivity, specificity, accuracy, and diagnostic efficiency than ultrasonography, and it can be used routinely in the emergency department to supplement ultrasound findings.

[Experimental study with Doppler ultrasound in partial chronic obstructive uropathy]

INTRODUCTION

This study has aimed to assess the hemodynamic parameters, Renal Resistive Index (RI), Peak Systolic Velocity (PSV), End-Diastolic Velocity (EDV) and Blood Flow of the Renal Artery (FR) by Doppler Ultrasound for diagnosis and monitoring postsurgical partial chronic obstructive uropathy.

MATERIAL AND METHODS

Fifty pigs were used. The experiment was divided into three phases. Phase I consisted of a duplex-Doppler evaluation of the both kidneys to determine the parameters under study. The ratio of each index is calculated as the difference between the value of study kidney and the contralateral. After, a fluoroscopic examination was performed by compressive cystography, excretory urography and retrograde ureteropyelography. Finally, a model of partial right ureteral obstruction was created. After six weeks of the obstructive model, Phase II was begun with the diagnosis of the uropathy, by means of the aforementioned diagnostic methods and the endourological treatment was completed. Phase III is a follow-up performed at 6 months of treatment using the same methods as in the previous phases.

RESULTS

Of the parameters studied, the EDV and its ratio showed greater sensitivity and specificity as a diagnostic marker of obstructive uropathy. In the postoperative monitoring, it was observed that the RI and the EDV returned to baseline levels, with the baseline values.

CONCLUSIONS

The ΔEDV and its ratio is the parameter that shows the greater efficacy for the diagnosis of chronic partial obstructive uropathy, however, it is insufficient to avoid conventional diagnostic techniques. All the parameters, mainly the EDV, have proven useful as complementary tests for monitoring after endourologic resolution of obstructive uropathy.

Functional evaluation of the urinary tract by duplex Doppler ultrasonography in patients with acute renal colic

Purpose

To determine the role of duplex Doppler ultrasonography (DDU) in patients with acute unilateral renal obstruction.

Subjects and methods

A total of 161 patients with suspected renal colic due to urolithiasis were evaluated by DDU followed by intravenous urography (IVU). The mean intra-arterial resistive index (RI) and the difference of mean resistive index between both kidneys (delta RI) were determined for each person. An RI value of ≥0.70 and a delta RI value of ≥0.06 were taken as the discriminatory threshold for obstruction. IVU results were considered the “ reference standard” against which renal DDU findings were compared.

Results

IVU showed both kidneys to be normal in 51 patients and with unilateral ureteric obstruction in 110 patients. The mean RI for obstructed kidneys was 0.67 (0.048), which was significantly higher (P-value <0.05) than a mean RI of contralateral normal kidneys 0.59 (0.04). The mean delta RI in patients with unilateral ureteric obstruction was significantly higher than that in patients with normal kidneys, at 0.076 (0.03) and 0.03 (0.05), respectively. In patients with complete obstruction, sensitivity of RI and delta RI were 77.5% and 92.5% with a specificity of 84.3% and 90.1%, respectively. In patients with partial obstruction, the sensitivity of these values was 22.8% and 62.8% with a specificity of 84.3% and 90.1%.

Conclusion

Delta RI is more sensitive and specific than RI in acute renal obstruction. However, due to relatively low sensitivity for detection of partial obstruction, DDU cannot replace IVU as the standard imaging technique.

Advances in noninvasive methods for functional evaluation of renovascular disease

As the number of patients with newly diagnosed renal artery stenosis increases, so has the number of percutaneous transluminal renal-artery angioplasties in the last few years. Deciding the preferred treatment in the clinical setting is fraught with difficulties related to many factors, and there is limited evidence to support angioplasty/stent for any indication. These considerations emphasize the urgent need for improved noninvasive assessment of kidney function in patients with vascular disease. This review will attempt to summarize the available techniques that may potentially be used for measurement of renal function in this context.

[Doppler US of the urinary system and renal vessels in normal and pathologic conditions]

The interest of Doppler ultrasound (US) in urinary tract investigation has dramatically increased during the past 10 years. It can provide useful diagnostic informations in pedicular and intrarenal vascular disorders, some medical nephropathies, in the assessment of renal tumors and urinary tract disorders including urolithiasis, acute obstruction and ureteral reflux. Recent technical improvements including the development of US contrast agents (microbubbles) have contributed to increase the diagnostic accuracy of the technique.

Role of resistive index in renal colic

We studied the role of duplex Doppler ultrasonography in the diagnosis of renal obstruction caused by ureteral calculi. Using duplex Doppler sonography, we evaluated the intrarenal hemodynamics of 27 patients who presented to the emergency department with renal colic. We performed Doppler ultrasonography on patients in whom US did not reveal any pathology causing renal colic and calculated and compared mean RI values of normal and obstructed kidneys and DeltaRI values of each group. Threshold levels for the diagnosis of urinary tract obstruction (mean RI > or = 0.70 and DeltaRI > or = 0.08) were used to determine the sensitivity and specificity of Doppler sonography for the diagnosis of urinary tract obstruction. Patients were investigated for revealing calculi diagnosis either by stone excretion history, intravenous pyelography or non contrast enhanced urinary computed tomography. A total of 162 intrarenal arterial Doppler recordings were made on 54 kidneys. Of the 16 patients with urinary obstruction, 11 (68%) had sonographic evidence of pelvicalyceal dilatation. The mean RI of the 16 obstructed and 11 unobstructed kidneys was 0.69 +/- 0.04 and 0.61 +/- 0.06 (mean +/- standard deviation), respectively. The difference between the mean RI values for each group was statistically significant (P < 0.05). Mean RI values of the contralateral kidneys in the obstructed group and unobstructed group were 0.61 +/- 0.03 and 0.59 +/- 0.05, respectively. Also DeltaRI value (0.07 +/- 0.02) of obstructed kidney group was statistically higher than the DeltaRI value (0.01 +/- 0.03) of the unobstructed group (P < 0.05). The mean RI of the 16 obstructed kidneys (0.69 +/- 0.04) was significantly greater than that of the 16 unobstructed contralateral kidneys (0.61 +/- 0.03) (P < 0.05). This study supplements the existing evidence that, in acutely obstructed kidneys, renal Doppler recording can demonstrate altered renal perfusion before pelvicalyceal system dilatation and distinguish obstructed and unobstructed kidneys evaluated with suspicion of renal colic.

Correlation between the renal resistive index (RI) and nonenhanced computed tomography in acute renal colic: how reliable is the RI in distinguishing obstruction?

OBJECTIVE

The purpose of this study was to determine the sensitivity of renal color Doppler sonography in differentiating obstructive and nonobstructive urinary calculi in patients with acute renal colic and to compare findings with nonenhanced helical computed tomography (CT).

METHODS

Sixty-five patients referred to the emergency department with acute renal colic underwent nonenhanced CT and renal resistive index (RI) measurement with color pulsed Doppler sonography within 8 to 10 hours of the onset of the symptoms. Computed tomographic evaluation was based on the detection of urolithiasis and classification according to location and the presence of obstruction. The mean RI of each kidney and the difference between the mean RI (DeltaRI) of both kidneys were calculated and compared with CT findings.

RESULTS

A total of 164 stones were identified. Computed tomography revealed obstruction in 33 patients. Mean RI values for the obstructive and nonobstructive groups were 0.64 and 0.63, respectively. Mean DeltaRI values were 0.01312 and 0.01000 in the obstructive and nonobstructive groups. The differences in the mean RI and DeltaRI for the patients with and without obstruction were statistically insignificant (P = .73). No significant relationship was found between the RI values, calculus location, and degree of obstruction.

CONCLUSIONS

The RI is insensitive for detection of obstruction in patients with acute renal colic, and its value in routine practice seems quite controversial.

Renal Doppler sonography--update in clinical nephrology

These days renal Doppler sonography has been established as a diagnostic tool of the daily nephrological work-up. Extra- and intrarenal flow signals are obtained for different indications. The intrarenal resistive index is the best examined parameter in the literature. However, the results have to be carefully interpreted, because different hemodynamic factors, such as heart rate, stiffness of the aorta as well as observer-dependent factors may have an impact on the level of the resistive index. The value of this non-invasive technique is discussed in detail for different renal diseases, such as acute and chronic renal failure, renal artery stenosis and for patients after renal transplantation. Being aware of several pitfalls which may lead to false results, nephrologists may use renal Doppler sonography as the first screening method of choice in the diagnostic algorithm.

Color Doppler sonography examination of partially obstructed kidneys associated with ureteropelvic junction stone before and after percutaneous nephrolithotripsy: Preliminary report

AIM

To evaluate resistive index (RI) changes before and after unilateral percutaneous nephrolithotripsy in chronic partially obstructed kidneys due to ureteropelvic junction (UPJ) stones.

METHODS

Intrarenal RI of obstructed and contralateral normal kidneys of 18 patients were recorded immediately before the operations and at postoperative days 1, 7 and 30. Postoperative RI measurements were compared with baseline values for all patients without grouping and separately for different groups according to the preoperative RI value of the obstructed kidney.

RESULTS

Mean age and symptom duration were 27.5 years and 43.8 weeks, respectively. Preoperatively and at all postoperative controls, kidney diameters and renal parenchyma thicknesses were normal in all patients. Mean RI of obstructed kidneys decreased from 0.68 to 0.63 for all patients (P=0.032), from 0.64 to 0.63 for those with preoperative RI<0.70 (P=0.850) and from 0.73 to 0.62 for those with preoperative RI>or=0.70 (P=0.001). In patients with preoperative RI>or=0.70 in obstructed kidney, significant RI decreases were recorded at postoperative day 7 and RI differences between obstructed and contralateral kidneys disappeared after then. No difference was present pre- and postoperatively between the mean RI of obstructed and contralateral kidneys of the patients with RI<0.70. Mean RI of contralateral kidneys were normal preoperatively and showed no significant change postoperatively.

CONCLUSIONS

Preoperative RI levels may indirectly reflect the presence of functionally significant obstruction in chronic obstructed kidneys related to UPJ stones. Patients with RI>or=0.70 may have a good indication for a surgical approach. Normalization of high RI occurs rapidly after percutaneous nephrolithotripsy.

Functional evaluation of the urinary tract by color-Doppler ultrasonography (CDU) in 100 patients with renal colic

INTRODUCTION AND OBJECTIVE

To evaluate if the addition of a renal color-Doppler ultrasonography (CDU) in the setting of acute renal colic improves the sensitivity of conventional sonography.

MATERIALS AND METHODS

Between July 2002 and June 2003, 100 patients (median 49 years) with renal colic have been evaluated. Within 24 h of the admission, a CDU study of the urinary tract was performed using a sonograph GE Logiq 500 PRO with a multifrequency (3-5 MHz) convex probe. The following parameters were evaluated: ultrasonography (US) of both kidneys, ureters and bladder; resistive index (RI) of the arciform arteries of both kidneys in three different parenchymal areas; ureteric jets in response to hydration. A renal RI>0.70 and/or a 10% difference between the kidneys were considered as diagnostic of obstructive uropathy; an asymmetric and/or reduced ureteric jet from the ureteric orifices was an additional indicator of obstruction. All patients underwent a CT scan both with and without the administration of contrast medium.

RESULTS

Enhanced helical CT demonstrated an urinary stone in 90 out of the 100 patients (90%): 29 pyelic, 28 at the pyelo-ureteral junction, 23 lumbo-iliac and 10 juxtavesical stones. Among 90 patients with urolithiasis, the stone was undetectable with US in 11 cases (12.2%); in 8 cases (8.9%) pyelocalicectasis was absent, and in 6 patients (6.6%) a non-obstructive hydronephrosis was present. Median RI in obstructed and non-obstructed kidney was 0.73 (range 0.71-0.87) versus 0.62 (0.50-0.68), respectively; in two, obstructed kidneys RI was <0.70 but greater than 10% compared with normal side. Sensitivity and specificity of US, CDU (RI+ureteric jet), unenhanced helical CT and CDU in association with unenhanced helical CT were 94.8 and 55.5, 98.9 and 90.9, 100 and 100%, respectively.

DISCUSSION AND CONCLUSIONS

CDU in patients with renal colic and/or pelvicalicectasis improves the diagnostic accuracy of US in distinguishing between obstructive and non-obstructive dilatation. Combined with unenhanced CT, CDU has a 100% sensitivity and specificity. Moreover, due to the absence of contraindications and side-effects, CDU is indicated for the follow-up of patients after ESWL, pregnant women and children.

Contrast media induces hypoperfusion in kidneys with ureteral stone: Doppler US study

We aimed to assess the hemodynamic effects of nonionic low-osmolarity contrast media (CM) on kidneys with ureteral stone (KUS). A total of 16 patients with KUS (group A) and 25 control patients (group B) were evaluated with Doppler ultrasound (US) bilaterally for main (MRA), interlobar (ILA) and arcuate renal arteries (ARA), before and 15 min after CM for IV pyelography. Peak systolic (PSV) and end diastolic velocities (EDV) and resistance index (RI) were measured. Data were analyzed by ANOVA and t-test. In group A, CM induced increase in PSV of MRA of contralateral kidney (p = 0.021) and decrease in PSV of ILA (p = 0.024), decrease in PSV and EDV and increase in RI of ARA of KUS (p = 0.010, 0.005, 0.027, respectively). CM induced hypoperfusion in KUS and compensatory changes in contralateral kidneys, similar to the effects of diuresis or mannitol. We conclude that the effect of CM on KUS is related to its osmolar load.

Doppler sonography in the diagnosis of urinary tract obstruction by stone

PURPOSE

This study was conducted to evaluate the accuracy of Doppler sonography in renal colic due to obstruction and to assess whether the resistance index (RI) and interrenal RI difference (DeltaRI) are time-dependent parameters.

SUBJECTS AND METHODS

Obstructed and unobstructed contralateral kidneys in 28 patients with renal colic and normal kidneys in 27 control subjects were prospectively evaluated with Doppler sonography. Mean RI, mean DeltaRI, and duration of pain were evaluated. Statistical analysis was done using paired and independent t-tests.

RESULTS

Mean RIs of the control-group, obstructed, and contralateral kidneys were 0.60, 0.71, and 0.61, respectively; mean DeltaRI values of the obstructed and control-group kidneys were 0.10 and 0.03, respectively. Differences in mean RI between obstructed and contralateral or control-group kidneys were statistically significant (p < 0.001). There was a statistically significant difference in DeltaRI between patients and controls (p < 0.001). The difference between the RI values of kidneys with low-grade (0.70) and high-grade obstructions (0.72) was not statistically significant. The difference between the DeltaRI values of kidneys with low-grade (0.08) and high-grade obstructions (0.13) was statistically significant (p < 0.05). Differences in the mean RI and mean DeltaRI values between 3 groups of patients categorized according to the duration of pain were not statistically significant.

CONCLUSIONS

Along with gray-scale sonography and intravenous urography, Doppler sonography can be used in the evaluation of renal obstruction. RI and DeltaRI are not time-dependent parameters.

Doppler sonography of renal obstruction: value of venous impedance index measurements

OBJECTIVE

Arterial resistive index values have poor sensitivity and specificity for alterations in renal perfusion induced by collecting system obstruction. We aimed to determine whether the intrarenal venous impedance index values could be useful in evaluating renal parenchymal compliance in cases of obstruction and in differentiating acute obstruction from chronic cases.

METHODS

Fifteen patients with acute renal colic having unilateral stone disease and another 15 patients having unilateral chronic obstruction due to various causes were evaluated sonographically. The diagnosis was confirmed either by computed tomography or intravenous urography in all cases. Fifteen subjects with normal kidneys were investigated as a control group. All patients were examined prospectively by conventional and Doppler sonography. The impedance indices and peak flow signals of the interlobar arteries and veins of both kidneys were calculated from spectral Doppler waveforms in all 3 groups.

RESULTS

The mean venous impedance index on the acutely obstructed side was lower than the index on the unobstructed side: 0.25 +/- 0.07 and 0.53 +/- 0.3 (mean +/- SD), respectively (P = .005). The mean venous impedance index on the acutely obstructed side was less than the indices both on the chronically obstructed side and in the control subjects (P > .0001). In acute cases, the mean arterial resistive index on the obstructed side was higher than the index on the unobstructed side: 0.62 +/- 0.06 and 0.57 +/- 0.06, respectively (P = .001). No statistically significant difference was detected between other parameters evaluated for the test and control groups.

CONCLUSIONS

Renal venous impedance index values may be helpful in evaluating renal hemodynamics in obstruction and in differentiating acute obstruction from chronic cases when used in conjunction with the arterial resistive index.

Changes of Renal Blood Flow in Nephroptosis: Assessment by Color Doppler Imaging, Isotope Renography and Correlation with Clinical Outcome after Laparoscopic Nephropexy

OBJECTIVE

Previously, we have detected changes in renal blood flow secondary to nephroptosis by assessing the renal resistive index (RI) using color Doppler imaging (CDI). The aim of the current study was to compare two diagnostic methods, CDI and isotope renography (IRG), for detection of renal blood flow impairment in patients with nephroptosis.

METHODS

26 patients with nephroptosis and flank pain underwent CDI and isotope renography (IRG) before and after laparoscopic nephropexy. The RI was assessed in segmental arteries with the patient in both the supine and erect position. Pre- and postoperative patient symptoms, results of Doppler measurements and IRG findings were assessed.

RESULTS

Preoperatively, 23 of 26 symptomatic patients showed a mean reduction in RI of more than 0.10 on the affected side, while only 7 of 26 patients had abnormal findings on preoperative IRGs. Postoperatively, none of the patients with preoperative changes in Doppler parameters showed any posture-related changes in RI. On postoperative IRG, obtained in 4 of 7 patients, normalization of renal perfusion was documented. Twenty out of 26 patients were asymptomatic postoperatively; in the remaining 6 patients symptoms were markedly improved.

CONCLUSION

Impairment of renal blood flow due to nephroptosis was detected with both CDI and IRG. RI measurement by CDI appears to be significantly more sensitive in detecting renal blood flow impairment. RI should be assessed in patients with nephroptosis and may impact on the decision for laparoscopic nephropexy.

[Imaging of chronic and intermittent adult upper urinary tract obstruction]

State-of-the-art analysis of non invasive diagnostic imaging techniques to demonstrate upper urinary tract obstruction. Advances in imaging techniques are illustrated (sonography, CT scan, MRI). The imaging features of different presentations of chronic and intermittent obstruction are described with reference to current imaging modalities. New strategies for evaluation of chronic and intermittent upper urinary tract obstruction are proposed using ultrasonography as the first line examination. The role of MRI is illustrated. Causes of obstruction are classified based from the intraluminal, parietal or extrinsic location of the lesion.

[Imaging of acute urinary obstruction: non-enhanced CT or KUB and US]

The use of non-enhanced CT as a primary imaging technique for acute lumbar pain is now widely accepted in many centers instead of the traditional association of KUB and ultrasound. This review will present the different features of the disease according to each technique, emphasising on respective performances, advantages and disadvantages. Finally, a strategy will be proposed based on clinical presentation.

Renal colic: new concepts related to pathophysiology, diagnosis and treatment

PURPOSE OF REVIEW

To give new insights into the pathophysiology, diagnosis and treatment of acute renal colic caused by a stone disease.

RECENT FINDINGS

Traditional intravenous pyelography is no longer the primary method of investigation in patients with renal colic. If the patient has a history of previous attacks of renal colic and stone disease the recommended diagnostic approach is to start with plain abdominal radiography and ultrasonography together with Doppler ultrasonography. Noncontrast computerized tomography is reserved for unsolved problems. If the patient has no history of stone disease or has atypical clinical presentation it is better to start with noncontrast computerized tomography. Intravenous pyelography is indispensable if an endoscopic or open intervention is required. Magnetic resonance imaging is a promising method of investigation, particularly in pregnant women. Effective pain relief is achieved by the use of opioids, nonsteroidal antiinflammatory drugs or desmopressin.

SUMMARY

The diagnostic approach to renal colic has recently been changed due to the introduction of new, noninvasive radiologic procedures such as Doppler ultrasonography, noncontrast computerized tomography and magnetic resonance imaging.

Doppler visualization of ureteric jets in unilateral hydronephrosis in children and adolescents

OBJECTIVE

to evaluate Doppler visualization of ureteric jets in the assessment of unilateral kidney collecting system dilatation in children and adolescents.

METHODS AND PATIENTS

color Doppler ultrasonography was performed in 27 patients with hydronephrosis (11 female, 16 male, age range 3-21 years, mean age 10.5+/-4.4). Nine had acute obstruction due to ureteral calculus, seven had obstructive hydronephrosis due to uretero-pelvic junction (UPJ) stenosis, and 11 had non-obstructive hydronephrosis. Doppler was also performed in 32 healthy children (15 boys and 17 girls, age 2-17 years, mean age 7.8+/-3.9), who represented the control group.

RESULTS

in the control group jets were visible in 57 out of 64 ureteric units (89%). The mean frequency of jets in healthy children was 4.1 jets per min. In all children with hydronephrosis, jets were visible in 25 out of 27 normal ureteric units (92.6%), and their mean frequency was 4.5 jets per min. In children with acute unilateral colic, ureteric jets were completely absent in eight of nine patients (89%). In children with obstructive hydronephrosis, due to UPJ stenosis, jets were absent in five out of seven patients (71.4%), and in children with non-obstructive hydronephrosis jets were absent in three out of eleven patients (27.3%). When jets are visible, their frequencies are much lower on the obstructed side as compared with normal side, while in cases of nonobstructive dilatation frequency of jets is similar on both sides.

CONCLUSION

absence of jets in patients with acute obstruction due to ureteral calculus, strongly correlates with high-grade obstruction. In children with UPJ stenosis, presence of ureteric jet does not exclude significant obstruction, but the frequency of jets on the obstructed side is much lower as compared with the unaffected side. When there is absence of jet from the dilated side or significant asymmetry in jet frequency, hydronephrosis is likely to be obstructive.