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.     

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.     

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.     

Intrarenal Doppler ultrasound studies in normal and acutely obstructed kidneys.

Renal ultrasound examinations and intrarenal arterial Doppler studies were performed on 48 patients with normal renal tracts and 20 patients presenting with acute renal colic resulting from ureteric calculus, 14 of whom had urographic evidence of renal obstruction. The mean resistance index (RI) of the Doppler waveforms obtained on the 14 obstructed kidneys (70.4 +/- 6.22) was significantly higher than the mean RI of the 96 normal kidneys (62.4 +/- 6.43). The mean difference between the RIs of the obstructed kidneys and their contralateral non-obstructed kidneys (8.37 +/- 4.43) was also significantly higher than the differences in RI seen between pairs of normal kidneys (2.70 +/- 1.71). Five out of 14 obstructed kidneys showed no pelvicalyceal dilatation and could not have been shown to be obstructed on conventional sonography. Four of these five had RI changes suggestive of obstruction and thus 13 of 14 obstructed kidneys would have been identified as obstructed by a combination of Doppler and conventional sonographic findings. 10 of the 14 obstructed kidneys were re-examined after passage of a urinary calculus and nine showed a reduction in the RI of the previously obstructed kidneys. The 10th subsequently required ureterolithotomy.     

Ultrasound of the kidney: obstruction and medical diseases

Ultrasound has emerged as the primary imaging modality in conditions where either renal obstruction or renal medical disease is suspected on the basis of clinical and laboratory findings. In urinary tract obstruction, pathophysiologic changes affecting the pressure in the collecting system and kidney perfusion are well understood and form the basis for the correct interpretation of real-time US and color Doppler duplex sonography (CDDS). Ultrasound is very sensitive for the detection of collecting system dilatation ("hydronephrosis"); however, obstruction is not synonymous with dilatation, as either obstructive or nonobstructive dilatation may be present. To differentiate these conditions, CDDS with measurement of the resistive index (RI) in the intrarenal arteries is extremely helpful, as obstruction (except in the peracute stage) leads to intrarenal vasoconstriction with a consecutive increase of the RI above the upper limit of 0.7, whereas nonobstructive dilatation does not. Diuretic challenge to the kidney may further enhance these differences in RI between obstruction and dilatation. Based on these findings, the present value of US and CDDS in the assessment of the patient with flank pain or renal colic is suggested, especially with respect to promising results for spiral CT and based on cost analysis. In renal medical disease, distinguishing different pathologic conditions using gray-scale US and CDDS (RI) criteria is still very difficult. Nevertheless, US is the fist-line imaging modality in the patient with renal insufficiency. Electronic Publication     

Ureteroscopic treatment of proximal ureter stones with the aid of an antegrade occlusion balloon catheter

Purpose: To define the role of an antegrade occlusion balloon catheter in preventing migration of proximal ureteral stones to the dilated proximal ureter during endoscopic treatment.

Material and Methods: An occlusion balloon catheter was used in 8 of 21 patients with proximal ureteral stones who underwent ureterorenoscopy. Five of the eight patients had solitary kidneys admitting with anuria and had percutaneous nephrostomy. In the other three patients, percutaneous nephrostomy and occlusion balloon catheters were placed a day before the procedure, since these patients had total obstruction and massive dilatation of the proximal ureter and renal collecting system. The balloons of occlusion catheters were inflated with 1 ml of sterile saline proximal to the stones just before ureterorenoscopy.

Results: All stones could be reached by ureterorenoscopy and treated successfully with the aid of an ultrasonic lithotripter, and no stone migration to the upper dilated collecting system was observed. Just after the operation, while the patient was still lying on the operation table, the occlusion catheter was removed. The nephrostomy catheter was removed a day later. All patients were totally stone-free after the procedures.

Conclusion: Occlusion balloon catheters increase the ureteroscopic treatment success rate in proximal ureter stones. This should be kept in mind especially when dilatation of the proximal collecting system is prominent and in cases with unsuccessful previous intervention with a retrograde stone cone catheter.     

Renal Doppler ultrasound examination of ureteral obstruction in rabbits: effects of different sites and degrees of obstruction on renal resistive index

RATIONALE AND OBJECTIVES: We sought to investigate the usefulness of Doppler resistive index (RI) in the diagnosis and follow-up of obstructive uropathy of different degrees and different sites of obstruction. METHODS: Forty-six rabbits were classified as follows: group I, partial unilateral obstruction of the proximal ureter (n = 16); group II, complete unilateral obstruction of the proximal ureter (n = 17); group III, complete unilateral obstruction of the distal ureter (n = 13). The RI of the obstructed and contralateral kidneys was measured preoperatively and postoperatively 1 hour, 6 hours, 1 day, 3 days, 1 week, 2 weeks, and 4 weeks, respectively. In each group, the RI was analyzed for statistical differences in the preoperative versus postoperative kidneys, and the obstructed versus contralateral kidneys. We also analyzed the statistical differences in RIs of the obstructed kidneys, in interrenal RI differences (DeltaRI: RI of the obstructed kidney - RI of the contralateral kidney), and in RI ratio (RI of the obstructed kidney / RI of the contralateral kidney) between the 3 groups. RESULTS: The RIs in the obstructed versus contralateral kidneys were significantly increased (P < 0.05) postoperatively at 1 hour, 1 day, and 2 weeks in group I; 6 hours and 1 week in group II; and 1 hour, 6 hours, and 3 days in group III. In obstructed kidneys, the RIs in the postoperative versus preoperative kidneys were significantly increased (P < 0.05) from 1 hour to 2 weeks in group I and from 1 hour to 4 weeks in group II. There were no statistically significant differences in mean RI, DeltaRI, and RI ratio between the 3 groups during the preoperative and postoperative period. CONCLUSIONS: Doppler RI can be elevated in hydronephrotic kidney as a result of both partial and complete obstruction of the ureter. There are no RI differences among obstructed kidneys with different degree and different site of ureteral obstruction.     

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.     

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.     

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.     

Nondilated obstructive uropathy: percutaneous nephrostomy performed to reverse renal failure

Ureteral obstruction can lead to renal failure without involving detectable dilatation of the calyces, renal pelvis, or ureter proximal to the obstruction. This phenomenon was noted in seven patients who had clinical obstruction that we were not able to diagnose using computed tomography (CT) or ultrasonography (US). These patients underwent percutaneous nephrostomy (PCN), which resulted in brisk diuresis and improved renal function. We obtained an accompanying antegrade urogram in these cases, which demonstrated the level of obstruction and indicated that dilatation of the collecting system was minimal or not present. When obstructive uropathy is suspected, we believe it is essential to consider performing PCN to evaluate and potentially reverse renal failure, even when CT and US scanning do not demonstrate obstruction.     

Doppler-duplex ultrasound in renal colic

Objective: To determine the role of intrarenal Doppler ultrasound (US) in patients with renal colic and to establish the usefulness of this diagnostic method. Materials and methods: In 121 patients with renal colic and 70 healthy individuals, 382 kidneys were examined with color duplex US. Mean intrarenal-arterial resistive index (RI), and the difference of mean RIs (dRI) between both kidneys were determined. In 64 patients, RI and dRI were compared with urographic findings (time of delay pyelogram between both kidneys). Results: In the 70 healthy individuals, RI was 0.62 ± 0.045 and dRI 0.018 ± 0.01. In the 121 patients with renal colic, RI (0.71 ± 0.06) was significantly superior (P < 0.001) with respect to the opposite kidney, with a dRI of 0.09 ± 0.055. In a correlation performed in 64 patients with urographic findings among color doppler US, with a RI ≥ 0.70 and/or dRI ≥ 0.06 as an indicative value of obstruction, sensitivity and specifity were 91.8% for patients with delayed pyelogram (n = 37 patients), and 48.1% for patients with nondelayed pyelogram (n = 27 patients) with a specificity of 92.8% with respect to the group of normal patients. In the group of patients with delayed pyelogram, RI was significantly superior (P < 0.05) in patients with an evolution time greater than 24 hours, in patients with proximal ureteral obstruction and in patients who had signs of pyelonephritis. There were no significant differences in the group of patients with nondelayed pyelograms. Conclusion: Color Doppler US is useful to fundamentally evaluate the consequences of the obstruction on renal function. Other factors such as evolution time of the symptomology, obstruction level, or existence of pyelonephritis can alter the US-Doppler values.     

Percutaneous nephrostomy in paediatrics

Percutaneous nephrostomy has been performed on 18 kidneys in 16 children with an age range of 1 day old to 14 years. The indications and techniques for percutaneous nephrostomy are described, the results are documented, and the effects of the procedure on the management of these patients are discussed. It is shown that percutaneous nephrostomy in paediatrics is a safe and reliable method for draining renal collecting systems in order to relieve obstruction, to assess renal function and to drain pyonephroses.     

Biliary pressure: manometric and perfusion studies at percutaneous transhepatic cholangiography and percutaneous biliary drainage

Manometric pressure recordings were attempted during percutaneous transhepatic cholangiography (PTC) and after percutaneous biliary drainage (PBD) in 203 cases. Successful readings were achieved at PTC in 85% (104/122) of patients. Pressure measurements were also obtained through 56 biliary drainage catheters, and controlled perfusion challenges were performed in 12 patients (on 18 occasions). Documentation of the occasionally poor correlation between the caliber of ducts and the degree of obstruction (i.e., pressure) was shown, and it was suggested that very high pressures may be predictive of a bile leak after PTC. Adequacy of percutaneous drainage and stricture dilatation were further assessed with these manometric techniques. Pressure and perfusion data aided in detecting and determining the significance of the nondilated obstructed duct, the dilated nonobstructed ductal system, and subtle distal ductal strictures. The knowledge obtained from percutaneous pressure recordings may help to determine appropriate therapy.     

Nondilated obstructive acute renal failure: diagnostic procedures and therapeutic management

We examined 80 patients with acute obstructive anuria by ultrasound (US). Four of the 80 patients did not have dilatation of the urinary tract. In all four cases, antegrade pyelography guided by real-time US demonstrated urinary tract obstruction after the four patients had experienced 4, 5, 8, and 34 days of anuria, respectively. Diuresis occurred as a result of percutaneous nephrostomy in all four cases. Three of the patients were successfully treated by percutaneous techniques alone. Our findings demonstrate that even a complete and long-term obstruction of the urinary tract does not necessarily induce dilatation in the upper part of the tract. In such cases, only the direct opacification of the urinary tract can help confirm that the obstruction is present. Even in the absence of dilatation, antegrade pyelography guided by real-time US is a possible diagnostic method and can be the first step in the performance of percutaneous nephrostomy.     

Radiological investigation for expert and medico-legal purposes

PURPOSE: To investigate whether colour Doppler US can demonstrate haemodynamic differences in patients with renal colic after pharmacological treatment with indomethacin and ketorolac. MATERIALS AND METHODS: We studied 180 consecutive patients with unilateral acute renal colic with colour Doppler US; 90 were treated with indomethacin, 90 with ketorolac. Furthermore, 37 consecutive patients without obstruction (17 treated with indomethacin and 20 with ketorolac) were also examined and considered normal controls. RESULTS: In the patients with renal colic the average resistive index (RI) was significantly greater on the side of the colic after administration of either indomethacin or ketorolac (p<0.001). The average RI in the obstructed kidneys was significantly higher in the patients treated with ketorolac than with indomethacin (p<0.005). No statistically significant differences were shown between the average RIs of the non obstructed kidneys of the patients with renal colic and between the kidneys of the control patients treated with either indomethacin or ketorolac. DISCUSSION AND CONCLUSIONS: Doppler evaluation of patients with renal colic requires careful interpretation after the administration of nonsteroidal anti-inflammatory drugs (NSAIDs), since values of renal RI depend on the drug that has been used to relieve symptoms.     

Pre- and postnatal diagnostic imaging of congenital urinary tract disorders

The prenatal diagnosis of urinary tract obstruction was made in 10 neonates. These findings were confirmed postnatally by sonography, urography, voiding cystourethrography, and scintigraphy. There were 8 neonates with unilateral obstruction of the ureter, and 2 with urethral valves and reflux. Nephrectomy because of hydronephrosis was necessary in 2 instances. The prenatal diagnosis of a urinary tract obstruction is of great importance, because the neonate may be operated upon without delay. Thus the diseased kidney can be saved. Diuretic radionuclide urography is helpful in differentiating between dilated obstructed and dilated nonobstructed kidneys.     

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 obstruction in patients with ileal loops: US evaluation

Ultrasound (US) is often employed as a screening test for hydronephrosis in the nondiverted kidney and has been used recently to evaluate the diverted kidney, specifically ileal loops, for obstruction. The utility of US in evaluating obstruction in patients with ileal loops has apparently not been previously explored. During a 2-year period, 87 kidneys drained by an ileal loop diversion were examined with US because of clinical indications of possible renal obstruction. In 33 kidneys, no hydronephrosis was seen on sonograms, and no obstruction was later proved; in 51 kidneys, shown by US to be hydronephrotic, only 19 (37%) were obstructed. Three left kidneys were not visualized with US. The percentage of hydronephrotic kidneys subsequently shown to be obstructed increased rapidly as the US appearance progressed from grade 1 (20%) to grade 3 (80%). In this series, US had a 100% sensitivity and a 50% specificity in evaluating patients with ileal loops for renal obstruction. Thus, for the adult patient, a direct contrast evaluation of the collecting system is suggested; for the pediatric patient, initial use of US is justified as a means to avoid radiation exposure.     

Diagnostic performance of an expert system for interpretation of 99mTc MAG3 scans in suspected renal obstruction.

The purpose of the study was to compare diuresis renography scan interpretation generated by a renal expert system with the consensus interpretation of 3 expert readers. METHODS: The expert system was evaluated in 95 randomly selected furosemide-augmented patient studies (185 kidneys) obtained for suspected obstruction; there were 55 males and 40 females with a mean age +/- SD of 58.6 +/- 16.5 y. Each subject had a baseline (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) scan followed by furosemide administration and a separate 20-min acquisition. Quantitative parameters were automatically extracted from baseline and furosemide acquisitions and forwarded to the expert system for analysis. Three experts, unaware of clinical information, independently graded each kidney as obstructed/probably obstructed, equivocal, and probably nonobstructed/nonobstructed; experts resolved differences by a consensus reading. These 3 expert categories were compared with the obstructed, equivocal, and nonobstructed interpretations provided by the expert system. Agreement was assessed using weighted kappa, and the predictive accuracy of the expert system compared with expert readers was assessed by the area under receiver-operating-characteristic (ROC curve) curves. RESULTS: The expert system agreed with the consensus reading in 84% (101/120) of nonobstructed kidneys, in 92% (33/36) of obstructed kidneys, and in 45% (13/29) of equivocal kidneys. The weighted kappa between the expert system and the consensus reading was 0.72 and was comparable with the weighted kappa between experts. There was no significant difference in the areas under the ROC curves when the expert system was compared with each expert using the other 2 experts as the gold standard. CONCLUSION: The renal expert system showed good agreement with the expert interpretation and could be a useful educational and decision support tool to assist physicians in the diagnosis of renal obstruction. To better mirror the clinical setting, algorithms to incorporate clinical data must be designed, implemented, and tested.