Correlation Between the Renal Resistive Index (RI) and Nonenhanced Computed Tomography in Acute Renal Colic

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.     

多普勒超声诊断急性输尿管梗阻的实验研究

本研究利用多普勒超声对８例左侧输尿管结扎与８例正常对照家犬在术后２４小时内行双肾内动脉及肾脏超声（ＵＳ）观测，测取双肾内动脉阻力指数（ＲＩ），并与ＵＳ结果对比。结果表明，实验组梗阻侧肾ＲＩ在输尿管梗阻后８小时开始上升，且显著高于对照组肾ＲＩ（Ｐ＜０．００１），实验组双肾ＲＩ差值（＞０．１）显著高于对照组双肾ＲＩ差值（＜０．１）（Ｐ＜０．００１），在输尿管梗阻后８小时，实验组健侧肾ＲＩ显著低于对照组及术前ＲＩ（Ｐ＜０．００１），有１例家犬ＲＩ升高时ＵＳ未显示集合区扩张（１３％）。我们认为多普勒超声对诊断急性输尿管梗阻有重要意义。     

肾动脉阻力指数诊断急性上尿路梗阻的意义

应用彩色多普勒技术对20例急性上尿路梗阻的病人,进行患侧和健侧肾脏内的血流测量。各分支血管的血流阻力指数(RI)值被记录。测量的结果:急性上尿路梗阻疼痛发作时,肾内各动脉的血流阻力指数(RI)明显升高(0.67 0.08),对侧肾内血流阻力指数无变化(0.56 0.089,P值0.1,而正常组双侧肾脏的RI差值<0.03(P值<0.001)。通过对可疑肾及输尿管结石疼痛发作的病人,进行肾内血流的RI和RI差值的测量,观察RI的变化,能提供对这一类疾病诊断的支持。     

Intrarenal duplex Doppler sonographic evaluation of unilateral native kidney obstruction.

RIs were measured in intrarenal arteries in 66 kidneys of 33 examinees without renal impairment and in 42 kidneys of 21 patients with unilateral urinary obstruction. The mean RI in normal kidneys was 0.593 +/- 0.040. Patients with unilateral obstruction had a mean RI of 0.709 +/- 0.039 in obstructed kidneys and a mean RI of 0.591 +/- 0.033 in contralateral nonobstructed kidneys. Statistically significant differences have been noticed in the groups of normal versus obstructed kidneys (P < 0.001) and of obstructed versus contralateral nonobstructed kidneys (P < 0.001). The mean dRI was 0.118 +/- 0.034 in patients with unilateral obstruction, and it was 0.014 +/- 0.012 in examinees without renal impairment (P < 0.001). A comparison of RI values between the right and left kidneys in a patient with unilateral obstruction proved more useful than using a 0.7 RI cutoff value in a Doppler sonographic diagnosis of unilateral obstruction.     

多普勒超声评价正常妊娠及妊娠并输尿管结石孕妇肾内动脉血流指数变化

多普勒超声观测Ａ组３０名健康非孕妇女、Ｂ组１４０名正常孕妇及Ｃ组１２例妊娠并输尿管结石孕妇肾内动脉血流指数（ＲＩ、ＰＩ、Ｓ／Ｄ）。结果：Ｂ组１０９名（１１８只肾）有肾积水；无论有无肾积水Ｂ组肾ＲＩ、ＰＩ、Ｓ／Ｄ值与Ａ组无显著差异（Ｐ＞０．０５），除Ｂ组４只积水肾ＲＩ＞０．７（３％）外，Ａ、Ｂ组肾ＲＩ均＜０．７，且Ａ、Ｂ组左、右侧肾ＲＩ差值均＜０．１；Ｂ组积水肾ＲＩ、ＰＩ、Ｓ／Ｄ值高低与肾积水程度及孕周无关（Ｐ＞０．０５）。Ｃ组输尿管梗阻侧肾ＲＩ、ＰＩ、Ｓ／Ｄ均显著高于Ａ、Ｂ组与对侧健肾（Ｐ＜０．００１），梗阻侧肾ＲＩ均＞０．７且与对侧健肾ＲＩ差值＞０．１。结果表明：多普勒超声观测肾动脉血流指数变化对诊断妊娠合并机械性输尿管梗阻有重要意义     

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.     

Utility of the resistance index ratio in differentiating obstructive from nonobstructive hydronephrosis in children.

PURPOSE: We assessed the utility of the resistance index ratio (RIR) in distinguishing between obstructive and nonobstructive upper urinary tract dilatation in children. METHODS: Twenty-three children (7 days-14 years old) with unilateral dilated collecting systems and a contralateral normal kidney were prospectively evaluated by duplex Doppler sonography. We measured the resistance index (RI) of the intrarenal arteries and calculated the RIR. Ninety-six normal kidneys in 48 controls were also evaluated. RESULTS: Twelve kidneys were proved to be obstructed at the ureteropelvic junction, and 11 were found by renal scintigraphy with furosemide and/or by surgery to have nonobstructive dilatation. The mean RIR differed significantly between the obstructed and dilated nonobstructed kidneys (1.16+/-0.04 versus 1.04+/-0.04, respectively; p < 0.01). After surgical correction of ureteropelvic junction obstruction, the obstructed kidneys showed significant drops in the RIR (1.18+/-0.03 to 1.07+/-0.03, p < 0.01). The RIR showed no statistically significant relationship with age (r = -0.268, p > 0.01); however, the RI declined with increasing age (r= -0.414, p < 0.01). An RIR cut-off value of > or = 1.10 provided a good discriminatory level, resulting in a sensitivity of 92%, a specificity of 97%, a positive predictive value of 85%, and a negative predictive value of 97%. CONCLUSIONS: An RIR cut-off value of > or = 1.10 appears to be an effective parameter for evaluation and follow-up of unilateral obstructive hydronephrosis in children.     

Duplex sonography of retro-orbital and carotid arteries in patients with normal-tension glaucoma

PURPOSE: To evaluate retrobulbar and carotid arterial hemodynamics in patients with normal-tension glaucoma using Doppler sonography. MATERIALS AND METHODS: Duplex sonography was performed in 41 patients with normal-tension glaucoma and 30 control subjects to evaluate resistance indices (RIs) in retro-orbital and carotid arteries. Mean values were compared using the independent t-test. The ratios of the RI in retro-orbital to RIs in the carotid arteries (CCA and ICA) and interocular and intercarotid differences in RI (DeltaRI) were also calculated. RESULTS: Is in the central retinal (CRA) and temporal and nasal posterior ciliary arteries (TPCA and NPCA) were statistically significantly greater in glaucomatous eyes (p < 0.001). Plaque formation in carotid arteries without significant stenosis was noted in 12% of patients and 10% of control subjects. Ratios of RI of CRA or TPCA or NPCA to that of CCA and the ratios of RI of CRA or NPCA to that of ophthalmic arteries (OA) were significantly greater in glaucomatous eyes. We also found that ratios of the RI of CRA or TPCA or NPCA to that of ICA and the ratio of the RI of OA to CCA were nearly equal to 1 in both patients and control subjects. We found no significant difference between interocular and intercarotid DeltaRIs in patients and control subjects. CONCLUSIONS: In patients with symmetric normal-tension glaucoma, duplex sonography showed an elevated RI in CRA and PCA. The Doppler evaluation of carotid arteries was useful.     

Contribution of the renin-angiotensin system to the intrarenal resistive index in chronic unilateral partial ureteral obstruction in dogs

Purpose We investigated the role of the renin-angiotensin system on intrarenal hemodynamics in chronic unilateral partial ureteral obstruction (UPUO) using Doppler ultrasound (US). Methods In 11 dogs with chronic UPUO, we determined the renal resistive index (RI) before and 1 h after the intravenous infusion of an angiotensin-converting enzyme (ACE) inhibitor (captopril), an angiotensin II receptor type 1 (ART1) antagonist (L-158,809), and the combination of these two drugs. Change in resistive index (ΔRI) was calculated as RI after the administration of each tested material minus baseline RI. Results At the baseline measurement, significant differences in RI were seen between obstructed and nonobstructed kidneys. ACE inhibitor, ART1 antagonist, or the combination of these drugs did not result in any significant changes in RI in either obstructed or nonobstructed kidneys. However, in obstructed kidneys, ΔRI in the combination of ACE inhibitor and ART1 antagonist were significantly greater than those in ACE inhibitor or ART1 antagonist alone, whereas there were no significant differences in those values in nonobstructed kidneys. Conclusion These observations suggest that the renin-angiotensin system in dogs with chronic UPUO may not contribute significantly to the differences in intrarenal RI between obstructed and nonobstructed kidneys. However, the angiotensin-producing pathways and angiotensin II receptor subtypes other than ACE and ART1 may have some different effects between obstructed and nonobstructed kidneys.     

小儿肾积水血流动力学观察及临床意义

目的:研究小儿肾积水血流动力学指标及其临床意义。方法:应用彩色多普勒超声对20例正常小儿肾脏及30例小儿积水肾进行血流动力学研究。结果:①正常小儿肾脏主肾动脉(MRA)、段动脉(SRA)、叶间动脉(IRA)的血流收缩期峰值速度(PS)、舒张期峰值速度(ED)、平均速度(TAMx)、最低速度(TAMn)依次逐渐减小(P<0.01),MRA、SRA、IRA的阻力指数(RI)无明显改变(P>0.05);积水肾的PS、ED、TAMx、TAMn比正常肾脏的血流速度低(P<0.01),积水肾RI比正常肾RI大(P<0.05)。②肾积水术后1个月RI改善最明显,以后的改善将减缓,而其余各项指标在1~6个月期间恢复最为明显。结论:①肾积水时其血流动力学发生相应的变化,其中RI的变化具有较大临床意义。②梗阻性小儿肾积水,其SRA段RI>0.66。③术后RI值不降或反而升高,提示梗阻未完全解除,需再次手术治疗。     

Compensatory renal growth in children and adults studied by Doppler sonography

To identify modifications of kidney morphology and of the time-velocity spectral waveform associated with long-term compensatory hypertrophy, spectral Doppler sonography was performed in 30 children and adults with solitary kidneys 7 years to 28 years following nephrectomy. Doppler signals were obtained from three arterial sites in each kidney. The average renal volume was 207 mL and the mean hypertrophy of the kidneys was 186%. The mean value of pulsatility (PI) and Pourcelot (RI) indexes of solitary hypertrophied kidneys was significantly lower than that of normal paired kidneys or allografts with normal function described in the literature. The PI and RI were found to correlate inversely with the kidney volume and the body surface area (BSA). In spite of a long follow-up time, no patient suffered from renal failure. This study suggests that in the case of solitary kidney, specific ranges of PI and RI should be employed rather than those used with paired kidneys. © 1994 John Wiley & Sons, Inc.     

Changes of renal resistive index in response to hydration and diuretic administration in normal subjects and in patients with small ureteral stone.

The renal resistive index has been measured before and after hydration and administration of diuretics in persons with normal kidneys and in kidneys with small ureteral stone, either obstructing or nonobstructing, to assess induced flow changes and to identify features differentiating obstructing from nonobstructing stones. In normal kidneys the resistive index was normal (mean, 0.62+/-0.03); no changes in the resistive index occurred within 15 to 60 min after hydration alone, whereas the resistive index rose within 15 min after hydration plus administration of diuretics and then returned to initial values within 30 min. In both cases the resistive index decreased below basal values after 75 to 90 min. Similar changes were observed in kidneys with a nonobstructing ureteral stone. In kidneys with an obstructing ureteral stone the resistive index was higher than in normal subjects (mean, 0.73+/-0.02, P<0.01), increased further within 15 min after hydration and administration of diuretics (P<0.01), and remained higher than basal values during the following 90 min. In conclusion, different resistive index changes have been observed in response to hydration and diuretics in normal and obstructed kidneys. Duplex Doppler sonography and diuresis duplex Doppler sonography seem promising diagnostic tools to identify obstructing stones.     

Assessment of renal circulation in small for gestational age and appropriate for gestational age term newborns: a prospective study

PURPOSE: To compare selected parameters of renal circulation between small for gestational age (SGA) and appropriate for gestational age (AGA) newborns. METHODS: Fifty-two SGA and 100 AGA term newborns were examined. The size of the kidneys were measured, and renal blood flow in the central and intraparenchymal renal arteries were assessed via Doppler sonography. Peak systolic velocity (PSV), end diastolic velocity (EDV), mean blood flow velocity (V mean), resistance index (RI), and pulsatility index (PI) were determined and compared between the groups. RESULTS: No statistically significant differences in the velocity parameters were found between SGA and AGA infants in central renal arteries. Slightly higher RIs and PIs were seen in AGA newborns (RI, 0.76 +/- 0.13 versus 0.78 +/- 0.06 [p < 0.05]; PI, 1.65 +/- 0.54 versus 1.84 +/- 0.46 [p < 0.05]). There were statistically significant differences between the groups in all measured parameters in intraparenchymal arteries (RI, 0.57 +/- 0.11 versus 0.63 +/- 0.05 [p < 0.001]; PI, 0.89 +/- 0.26 versus 1.09 +/- 0.16 [p < 0.001]) except PSV (7.11 +/- 1.55 versus 7.14 +/- 0.81 cm/s [p > 0.05]). CONCLUSION: Based on our findings, we suggest that renal circulation is not negatively influenced by intrauterine growth restriction in SGA neonates compared with AGA newborns.     

Intrarenal Doppler: characteristics of aging kidneys.

The normal range of Doppler findings in native kidneys has not been studied extensively. This study correlates changes in Doppler resistive index (RI) with age in patients without renal risk factors or renal disease. Young and old patients demonstrated the highest RI values (age < 1, mean RI = 0.73; age > 59, RI = 0.68), and patients in the 20-39 year age group showed the lowest values (RI = 0.59). The mean RI for all ages was 0.63. The cause of this variability is unknown. We suggest that age-related changes in Doppler values should be considered in the interpretation of renal Doppler measurements.     

双功能超声检测输尿管结石患者肾内动脉阻力指数

采用双功能超亏检测３２例输尿和结石患者和３２例正常人肾内动脉阻力指数、结果表明：尿管结石患者的患肾ＲＩ显著高于健肾和正常人肾脏的ＲＩ，患肾与健肾ＲＩ差值较正常人双肾ＲＩＤ显著增高。     

Renal duplex Doppler sonography in asymptomatic women during pregnancy

The purpose of this study was to establish the normal range of the renal RI in pregnant women. Maternal renal RIs were calculated in 61 asymptomatic pregnant patients with at least unilateral pyelocaliectasis. A mean RI was calculated for each kidney. Overall, the mean RI was 0.61 +/- 0.05. The renal RI was > or = 0.70 in 4% (5/121) of kidneys with no statistically significant difference between the mean right (0.62 +/- 0.06) and left (0.60 +/- 0.04) kidney RIs. There was no correlation between trimester of pregnancy or degree of pyelocaliectasis and RI.     

Doppler sonography in the diagnosis of antepartum pyelonephritis: value of intrarenal resistive index measurements.

This study aims to define the effects of pyelonephritis on intrarenal resistive indices and to determine the role of Doppler sonography in the diagnosis of pyelonephritis in pregnant patients. Twenty pregnant women with pyelonephritis underwent renal Doppler sonography with calculation of intrarenal resistive indices. The resistive index was calculated for the upper, lower, and interpolar areas of each kidney in the patients with pyelonephritis (40 kidneys) and was compared to the resistive indices for a control group of 153 normal asymptomatic pregnant women (306 kidneys). Doppler findings were correlated with the location (sidedness) of flank pain in the pyelonephritis group. The mean resistive index values of patients with pyelonephritis were 0.04 higher than in the controls, and this difference was statistically significant (P < 0.001). Four patients with pyelonephritis had a mean resistive index > or = 0.70, whereas the remaining 16 patients had resistive indices within the normal range of < or = 0.70. In patients with confirmed pyelonephritis and unilateral pain, the average resistive index in the kidney on the side of pain was 0.03 greater than that on the asymptomatic side (P = < 0.01). The mean renal resistive index is significantly greater in pregnant patients with pyelonephritis than in pregnant women without pyelonephritis. Even so, the magnitude of the differences in resistive index is too small and the overlap between the groups too large for this parameter to be of discriminating clinical value.     

Intrarenal hemodynamic changes after captopril test in patients with type 2 diabetes: a duplex Doppler sonography study

OBJECTIVE: ACE inhibitors are known to be effective in preventing the progression of diabetic nephropathy. Activation of the renin-angiotensin system (RAS) is reported to contribute to intrarenal hemodynamic abnormality in diabetic patients. We examined whether RAS blockade by captopril induces intrarenal hemodynamic changes in normotensive patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: The patients ranged in age from 40 to 65 years (20 men and 20 women). A total of 15 age- and sex-matched healthy individuals served as control subjects. Resistive index (RI) of interlobar arteries was examined by duplex Doppler sonography before and after the oral captopril (25 mg) test. RESULTS: At baseline, no significant differences in RI values or plasma renin activity (PRA) were seen between the patients and healthy subjects. In healthy subjects, the RI values after the captopril test were significantly higher than baseline values (P < 0.01). However, in patients with type 2 diabetes, both with normoalbuminuria and microalbuminuria, RI values after the test were significantly lower than baseline values (P < 0.001). There were significant negative correlations between DeltaRI value and HbA1c (r = -0.458, P < 0.005) and between DeltaRI value and baseline PRA in diabetic patients (r = -0.339, P < 0.05). Multiple regression analysis showed that HbA1c and baseline PRA significantly and independently affected the magnitude of decrease in RI values after captopril administration in diabetic patients (R2 = 0.391, P < 0.0001). CONCLUSIONS: These results indicate that the intrarenal RAS may be activated in diabetic patients, that such activation may be affected by poor glycemic control, and that blockade of RAS activation by ACE inhibitor reduces intrarenal vascular resistance in diabetic patients. The results emphasize the beneficial effects of ACE inhibition in improving intrarenal hemodynamics in diabetic patients.     

彩色多普勒超声鉴别诊断不同类型的移植肾急性排异

目的研究彩色多普勒超声在鉴别不同类型移植肾急性移植肾排异中的价值。方法回顾性地总结了１１２例经组织穿刺活检病理证实的不同类型移植肾急性排异的彩色多普勒超声表现。结果肾血管血流参数ＰＩ、ＲＩ值在急性移植肾血管排异组与细胞排异组、临界改变组之间有显著性差异。结论彩色多普勒超声在鉴别移植肾急性血管性排异和细胞性排异之间有一定价值,但对于鉴别血管性排异与混合性排异、细胞性排异与临界改变之间的作用还难以肯定     

Resistive indices in the evaluation of infants with obstructive and nonobstructive pyelocaliectasis.

Diagnosing obstructive uropathy by renal resistive indices calculated from duplex Doppler sonographic waveforms has been supported as well as challenged in the radiology literature relating to adults. Despite reports of normally higher resistive indices in children as compared to adults, two studies have documented high sensitivity and specificity of renal Doppler sonography in the diagnosis of obstructive uropathy in children, using the same discriminatory criterion of a resistive index of 0.7 or greater as used in adults. We evaluated 43 infants with significant or bilateral pyelocaliectasis secondary to both obstructive and unobstructive uropathy and found no significant difference in the mean resistive indices or the mean difference in resistive indices of two kidneys in one patient. We conclude that Doppler sonography in infants has no value in differentiating obstructive from nonobstructive pyelocaliectasis.