To determine the potential clinical usefulness of duplex Doppler estimation of arcuate artery res... more To determine the potential clinical usefulness of duplex Doppler estimation of arcuate artery resistive index (a measure of intrarenal blood flow impedance) for diagnosis of aminoglycoside-induced nephrotoxicosis. 30 adult, female, mixed-breed dogs, allotted to 3 groups of 10 dogs each as: toxic dosage of gentamicin, therapeutic dosage of gentamicin, and saline solution sham equivalent in volume to that of the toxic dosage of gentamicin. After baseline screening to establish normalcy (serum biochemical analysis, endogenous creatinine clearance determination, urinalysis, urine protein-to-creatinine ratio, urine culture, gray-scale sonography, and percutaneous ultrasound-guided renal biopsy), results of arcuate artery resistive index determination were compared with serum creatinine and urine specific gravity values on a Monday-Wednesday-Friday data collection schedule for 10 days. Endogenous creatinine clearance determination, ultrasound-guided renal biopsy, and urine culture were repeated at the end of data collection in all 3 groups. Significant differences in resistive index measurements were not observed, despite clinicopathologic and renal biopsy results compatible with severe acute tubular necrosis in dogs of the toxic dosage group. Duplex Doppler sonography of arcuate artery blood flow impedance, expressed as the resistive index, appears to have poor clinical usefulness as a diagnostic tool in this disorder. Normal arcuate artery resistive index values obtained in dogs for which aminoglycoside-induced nephrotoxicosis is suspected do not exclude the disorder. If abnormal arcuate artery resistive index values are obtained for such dogs, further evaluation for nephropathies other than aminoglycoside-induced nephrotoxicosis may be considered.
We studied the role of duplex Doppler ultrasonography in the diagnosis of renal obstruction cause... more 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 ΔRI values of each group. Threshold levels for the diagnosis of urinary tract obstruction (mean RI ≥ 0.70 and ΔRI ≥ 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 ΔRI value (0.07 ± 0.02) of obstructed kidney group was statistically higher than the ΔRI 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.
To investigate the effect of intravenous normal saline fluid load, with and without furosemide, u... more To investigate the effect of intravenous normal saline fluid load, with and without furosemide, upon the renal resistive index (RI) of obstructed and nonobstructed kidneys. Right partial ureteral obstruction was induced in 10 dogs. Grade 1 (mild) obstruction was performed in 5 dogs (group A), and grade 3 (severe) obstruction was carried out to the remaining 5 dogs (group B). Evaluation by Doppler ultrasonography was performed before induction of ureteral obstruction and by the end of the 8th week of obstruction. Every obstructed animal was subjected to bilateral renal Doppler ultrasonography 3 times in one setting: 1) before infusion of normal saline, 2) 30-60 minutes after intravenous infusion of normal saline (15 ml./kg.) given in a rate of 1 ml./kg./min. and 3) 10 minutes after admission of furosemide (1 mg./kg.). After induction of right partial ureteral obstruction, there was a significant increase of the RI of the right kidney and a significant decrease of the RI of the left kidney compared to baseline RI in both groups. Infusion of normal saline and administration of furosemide caused a further significant increase of the RI of the obstructed kidney and a further significant decrease of the RI in the nonobstructed kidney in both groups. In unilateral partial ureteral obstruction, addition of intravenous normal saline and furosemide cause the RI to increase in obstructed kidney and to decrease in nonobstructed kidney. Such a divergent response may be useful for the development of a pharmacologically challenged Doppler examination to diagnose better potentially obstructed kidneys.
To evaluate the use of color Doppler imaging (CDI) for determining the resistive index (RI) of th... more To evaluate the use of color Doppler imaging (CDI) for determining the resistive index (RI) of the medial long posterior ciliary artery (mLPCA) in clinically normal conscious dogs. 18 (10 sexually intact males, 8 sexually intact females) dogs between 1 and 5 years old. Color Doppler ultrasonography was performed on both eyes with dogs in a sitting position. Each eye was imaged from the region dorsal to the zygomatic arch with the transducer positioned in a horizontal plane. The mLPCA was localized, and RI was calculated from velocities obtained for 3 similar Doppler waveforms. To determine the reproducibility of CDI-derived RI, measurements were repeated twice at a 10-day interval. Mean (+/- SD) RI of the mLPCA was 0.68 +/- 0.07 (95% confidence interval, 0.65 to 0.70; n = 36 eyes). Resistive index did not significantly differ between right and left eyes or male and female dogs. In addition, body weight was not correlated with RI. Repeated measurements of RI did not yield significantly different results (interclass correlation coefficient, 0.8297). Color Doppler imaging appears to be a valid technique for determination of RI of the mLPCA in conscious dogs. This technique may be useful for investigating the pathophysiologic processes of many ocular and orbital vascular disorders in dogs.
Some studies have shown that relative to baseline, the renal resistive index (RI) remains unchang... more Some studies have shown that relative to baseline, the renal resistive index (RI) remains unchanged in nonobstructed kidneys and increases in obstructed kidneys after administration of furosemide. To our knowledge, the effect of mannitol administration on the renal RI of dogs has not been reported. We evaluated the renal RI in 16 kidneys in 8 young adult dogs after administration of mannitol. The mean RI decreased significantly from baseline (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .01). Additionally, left complete ureteral obstruction wasinduced in 5 dogs. Evaluation by Doppler ultrasonography was performed for 5 days. On the 5th day, Doppler examination was repeated at 30 and 60 minutes after administration of mannitol to obstructed dogs. After induction of left ureteral obstruction, the RI of the left kidney increased significantly over 5 consecutive days. Administration of mannitol decreased the RI in the nonobstructed contralateral kidneys, and thus the RI difference between obstructed and nonobstructed kidneys was increased above normal (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001). In conclusion, administration of mannitol may be useful as another diuretic agent to identify unilateral ureteral obstruction on Doppler sonographic examination.
Objective Because acute renal failure (ARF) is frequent in septic shock, an early marker of ARF c... more Objective Because acute renal failure (ARF) is frequent in septic shock, an early marker of ARF could impact on management of such patients. High renal arterial resistive index (RI) is associated with parenchymatous renal failure. We assessed whether Doppler-measured RI on day 1 (D1) of septic shock can predict ARF. Design Prospective descriptive clinical study. Setting A 20-bed medical intensive care unit in a university hospital. Patients All patients with septic shock, excluding those with chronic renal failure (serum creatinine > 120 μmol/l). Measurements and results RI was determined during the first 24 h (D1) following vasopressor introduction, concomitant with recording of: age, SAPS II, mean arterial pressure, arterial lactate, catecholamine (dose and type), urine output and serum creatinine. ARF was diagnosed according to the RIFLE classification. RI measurement was possible for 35 of 37 included patients. On day 5 (D5), 17 patients were without ARF (RIFLE-0 or R) and 18 patients were classified as having ARF (RIFLE-I or F). On D1, RI was higher in these latter 18 patients (0.77 ± 0.08 vs. 0.68 ± 0.08, p < 0.001). They also had higher SAPS II and arterial lactate concentration. RI > 0.74 on D1 had a positive likelihood ratio of 3.3 (95% CI 1.1–35) for developing ARF on D5. RI correlated inversely with mean arterial pressure (ρ = –0.48, p = 0.006) but not with catecholamine type or dose or with lactate concentration. Conclusion Doppler-based determination of RI on D1 in septic shock patients may help identify those who will develop ARF.
... The highest frequency probe that gives measurable waveforms should be used, supplemented by c... more ... The highest frequency probe that gives measurable waveforms should be used, supplemented by color or power Doppler sonography as necessary for vessel localization. ... of renal function withcolor Doppler ultrasound in autosomal dominant polycystic kidney disease. ...
Recent clinical studies using duplex Doppler sonography identified an alteration in renal arteria... more Recent clinical studies using duplex Doppler sonography identified an alteration in renal arterial blood flow in obstructed hydronephrotic kidneys that reportedly can be used to distinguish obstructive from nonobstructive collecting system dilatation. We attempted to verify these clinical findings and establish the temporal relationship of the alteration in the Doppler spectrum to the onset of urinary obstruction by evaluating surgically induced urinary obstruction in dogs. We performed laparotomies on 11 dogs, with the left ureter isolated and ligated in five dogs, and left intact in six dogs (control group). Duplex Doppler examination of the left renal arteries performed nine times during the first postoperative month identified a statistically significant difference (p less than .05) in the Doppler resistive index calculation between the two groups on days 1, 2, 4, and week 4. A resistive index discriminatory threshold of 0.7 (greater than 0.7, obstructed; less than 0.7, nonobstructed) produced a test sensitivity of 74% and specificity of 77%. We conclude from our study that renal arterial duplex Doppler sonography can detect a change in renal perfusion as a result of urinary obstruction and that this change can be detected as early as 24 hours after obstruction. However, high false-positive and false-negative rates may limit the ability of this modality to reliably distinguish obstructive from nonobstructive collecting system dilatation.
The resistive index (RI), an ultrasonographic method of evaluating intrarenal resistance to blood... more The resistive index (RI), an ultrasonographic method of evaluating intrarenal resistance to blood flow, may be used to aid in diagnosis of renal failure. Values for arcuate artery RI, expressed as mean +/- two standard deviations, were obtained in clinically normal female dogs sedated with atropine, acepromazine maleate, diazepam, and ketamine hydrochloride. No statistically significant differences were noted between the values for the right kidney (0.33 to 0.57) versus the left kidney (0.32 to 0.56); however, the values were statistically significantly lower than values reported for nonsedated, normal dogs.
Purpose We investigated the role of the renin-angiotensin system on intrarenal hemodynamics in ch... more 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.
Results of studies on the accuracy of the resistive index as a predictor of acute renal transplan... more Results of studies on the accuracy of the resistive index as a predictor of acute renal transplant rejection have varied widely. Clinical evaluations are limited by the inability to control the numerous coincidental factors that affect vascular resistance. We performed a controlled study in dogs to isolate the effects of acute tubular necrosis, cyclosporine toxicity, and acute rejection on the resistive index, and to compare them with a population of normal control subjects. By doing so, we hoped to identify the patterns of change in the resistive index over time and possibly explain the wide spectrum of resistive index data reported in the literature. Resistive index, a parameter calculated from relative systolic and diastolic velocity, indicates parenchymal resistance to perfusion. Since an increase in renal length also has been reported useful in predicting rejection, we studied changes in length in each of the isolated conditions. The normal control group (four dogs) had heterotopic autotransplantation with minimal cold ischemic time. The acute tubular necrosis group (six dogs) had heterotopic autotransplantation with 1 hr of warm ischemic time. The cyclosporine toxicity group (four dogs) was allowed approximately 3 months to heal from heterotopic autotransplantation. Very high (toxic) doses of cyclosporine were then administered. The acute rejection group (five dogs) had heterotopic allografting with minimal cold ischemic time. No medications were administered. In all groups, the abnormalities induced were confirmed by biopsy. Creatinine levels were also used to monitor cyclosporine toxicity. In the normal control and acute tubular necrosis groups, resistive index increased immediately after surgery, returning to baseline within 10 days. Renal length increased slightly in both groups, but the duration of increase was longer in the acute tubular necrosis group. No significant change in resistive index or renal length was seen in the cyclosporine toxicity group. In the acute rejection group, an initial decrease in resistive index during the mild to moderate phase was followed by a rapidly progressive increase with worsening rejection. Renal length increased progressively beginning immediately after surgery. Our study determined the patterns of change in resistance and renal length over time as caused by the isolated pathologic states. Our finding that vascular resistance decreased in mild to moderate acute rejection was unexpected, since almost all the literature reports resistive index elevation. This may explain some of the conflicting results obtained in Doppler investigations of rejection. Our results on renal length reinforce the positive clinical reports of its predictive value in rejection.
... I6 This results in a From the Departments of Radiological Health Scienccs (Morrow, Wrig-ley) ... more ... I6 This results in a From the Departments of Radiological Health Scienccs (Morrow, Wrig-ley) and Clinical Sciences (Salman, Lappin), College of Veterinary Med-icine and Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523. ...
Most renal transplants fail because of chronic allograft nephropathy or because the recipient die... more Most renal transplants fail because of chronic allograft nephropathy or because the recipient dies, but no reliable factor predicting long-term outcome has been identified. We tested whether a renal arterial resistance index of less than 80 was predictive of long-term allograft survival. The renal segmental arterial resistance index (the percentage reduction of the end-diastolic flow as compared with the systolic flow) was measured by Doppler ultrasonography in 601 patients at least three months after transplantation between August 1997 and November 1998. All patients were followed for three or more years. The combined end point was a decrease of 50 percent or more in the creatinine clearance rate, allograft failure (indicated by the need for dialysis), or death. A total of 122 patients (20 percent) had a resistance index of 80 or higher. Eighty-four of these patients (69 percent) had a decrease of 50 percent or more in creatinine clearance, as compared with 56 of the 479 patients with a resistance index of less than 80 (12 percent); 57 patients with a higher resistance index (47 percent) required dialysis, as compared with 43 patients with a lower resistance index (9 percent); and 36 patients with a higher resistance index (30 percent) died, as compared with 33 patients with a lower resistance index (7 percent) (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for all comparisons). A total of 107 patients with a higher resistance index (88 percent) reached the combined end point, as compared with 83 of those with a lower resistance index (17 percent, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). The multivariate relative risk of graft loss among patients with a higher resistance index was 9.1 (95 percent confidence interval, 6.6 to 12.7). Proteinuria (protein excretion, 1 g per day or more), symptomatic cytomegalovirus infection, and a creatinine clearance rate of less than 30 ml per minute per 1.73 m2 of body-surface area after transplantation also increased the risk. A renal arterial resistance index of 80 or higher measured at least three months after transplantation is associated with poor subsequent allograft performance and death.
The renal resistive index (RI) value of 0.73 has been proposed as the upper limit in normal adult... more The renal resistive index (RI) value of 0.73 has been proposed as the upper limit in normal adult dogs. In humans, changes in RI with age are associated with plasma renin activity. There are relatively few equivalent reference data for dogs. We obtained reference RI data from 22 clinically healthy dogs <4 months of age and 33 healthy dogs between 4 months and 7 years of age. An association between the RI and plasma renin activity was investigated. The mean RI in the older dogs was 0.65 ± 0.05 vs. 0.75 ± 0.05 in dogs <4 months of age. The mean plasma renin activity in the older dogs was 1.18 ± 1.03 vs. 4.23 ± 3.09 ng/ml/h in dogs <4 months of age. There was a weak linear relationship between the RI and plasma renin activity (r2=0.280, P<0.01) in dogs <4 months of age. Also in these younger dogs, RI was negatively correlated with age (r2=0.682, P<0.01). The RI was higher in dogs <4 months of age than in older dogs. Therefore, the mean renal RI is slightly higher in young dogs than reported for an older population and interpretation of the RI must include an assessment of patient age.
In human beings, intrarenal blood flow impedance, expressed as the resistive index (RI) and obtai... more In human beings, intrarenal blood flow impedance, expressed as the resistive index (RI) and obtained by duplex Doppler ultrasonography, has been used to aid in diagnosis and prognosis of renal failure. Higher than normal values for RI were obtained in 3 of 4 dogs with acute tubular necrosis (ATN) and in 5 of 10 dogs with glomerulonephrosis (GN). Normalization of RI was observed in 2 dogs with ATN evaluated serially during treatment. Increased RI values were obtained in 9 of 10 cats with nonobstructive renal disease and in 2 of 5 cats with obstructive renal disease. Normalization of RI was observed in 3 cats with renal failure in which treatment was effective (1 with obstruction; 2 with nonobstructive disease). The magnitude of increase in RI did not correlate with the magnitude of concurrent renal dysfunction. These results suggest that duplex Doppler evaluation of intrarenal RI is more useful as an ancillary diagnostic technique in azotemic dogs with ATN than in those with GN and in azotemic dogs with nonobstructive than in those with obstructive disease.
To determine the potential clinical usefulness of duplex Doppler estimation of arcuate artery res... more To determine the potential clinical usefulness of duplex Doppler estimation of arcuate artery resistive index (a measure of intrarenal blood flow impedance) for diagnosis of aminoglycoside-induced nephrotoxicosis. 30 adult, female, mixed-breed dogs, allotted to 3 groups of 10 dogs each as: toxic dosage of gentamicin, therapeutic dosage of gentamicin, and saline solution sham equivalent in volume to that of the toxic dosage of gentamicin. After baseline screening to establish normalcy (serum biochemical analysis, endogenous creatinine clearance determination, urinalysis, urine protein-to-creatinine ratio, urine culture, gray-scale sonography, and percutaneous ultrasound-guided renal biopsy), results of arcuate artery resistive index determination were compared with serum creatinine and urine specific gravity values on a Monday-Wednesday-Friday data collection schedule for 10 days. Endogenous creatinine clearance determination, ultrasound-guided renal biopsy, and urine culture were repeated at the end of data collection in all 3 groups. Significant differences in resistive index measurements were not observed, despite clinicopathologic and renal biopsy results compatible with severe acute tubular necrosis in dogs of the toxic dosage group. Duplex Doppler sonography of arcuate artery blood flow impedance, expressed as the resistive index, appears to have poor clinical usefulness as a diagnostic tool in this disorder. Normal arcuate artery resistive index values obtained in dogs for which aminoglycoside-induced nephrotoxicosis is suspected do not exclude the disorder. If abnormal arcuate artery resistive index values are obtained for such dogs, further evaluation for nephropathies other than aminoglycoside-induced nephrotoxicosis may be considered.
We studied the role of duplex Doppler ultrasonography in the diagnosis of renal obstruction cause... more 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 ΔRI values of each group. Threshold levels for the diagnosis of urinary tract obstruction (mean RI ≥ 0.70 and ΔRI ≥ 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 ΔRI value (0.07 ± 0.02) of obstructed kidney group was statistically higher than the ΔRI 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.
To investigate the effect of intravenous normal saline fluid load, with and without furosemide, u... more To investigate the effect of intravenous normal saline fluid load, with and without furosemide, upon the renal resistive index (RI) of obstructed and nonobstructed kidneys. Right partial ureteral obstruction was induced in 10 dogs. Grade 1 (mild) obstruction was performed in 5 dogs (group A), and grade 3 (severe) obstruction was carried out to the remaining 5 dogs (group B). Evaluation by Doppler ultrasonography was performed before induction of ureteral obstruction and by the end of the 8th week of obstruction. Every obstructed animal was subjected to bilateral renal Doppler ultrasonography 3 times in one setting: 1) before infusion of normal saline, 2) 30-60 minutes after intravenous infusion of normal saline (15 ml./kg.) given in a rate of 1 ml./kg./min. and 3) 10 minutes after admission of furosemide (1 mg./kg.). After induction of right partial ureteral obstruction, there was a significant increase of the RI of the right kidney and a significant decrease of the RI of the left kidney compared to baseline RI in both groups. Infusion of normal saline and administration of furosemide caused a further significant increase of the RI of the obstructed kidney and a further significant decrease of the RI in the nonobstructed kidney in both groups. In unilateral partial ureteral obstruction, addition of intravenous normal saline and furosemide cause the RI to increase in obstructed kidney and to decrease in nonobstructed kidney. Such a divergent response may be useful for the development of a pharmacologically challenged Doppler examination to diagnose better potentially obstructed kidneys.
To evaluate the use of color Doppler imaging (CDI) for determining the resistive index (RI) of th... more To evaluate the use of color Doppler imaging (CDI) for determining the resistive index (RI) of the medial long posterior ciliary artery (mLPCA) in clinically normal conscious dogs. 18 (10 sexually intact males, 8 sexually intact females) dogs between 1 and 5 years old. Color Doppler ultrasonography was performed on both eyes with dogs in a sitting position. Each eye was imaged from the region dorsal to the zygomatic arch with the transducer positioned in a horizontal plane. The mLPCA was localized, and RI was calculated from velocities obtained for 3 similar Doppler waveforms. To determine the reproducibility of CDI-derived RI, measurements were repeated twice at a 10-day interval. Mean (+/- SD) RI of the mLPCA was 0.68 +/- 0.07 (95% confidence interval, 0.65 to 0.70; n = 36 eyes). Resistive index did not significantly differ between right and left eyes or male and female dogs. In addition, body weight was not correlated with RI. Repeated measurements of RI did not yield significantly different results (interclass correlation coefficient, 0.8297). Color Doppler imaging appears to be a valid technique for determination of RI of the mLPCA in conscious dogs. This technique may be useful for investigating the pathophysiologic processes of many ocular and orbital vascular disorders in dogs.
Some studies have shown that relative to baseline, the renal resistive index (RI) remains unchang... more Some studies have shown that relative to baseline, the renal resistive index (RI) remains unchanged in nonobstructed kidneys and increases in obstructed kidneys after administration of furosemide. To our knowledge, the effect of mannitol administration on the renal RI of dogs has not been reported. We evaluated the renal RI in 16 kidneys in 8 young adult dogs after administration of mannitol. The mean RI decreased significantly from baseline (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .01). Additionally, left complete ureteral obstruction wasinduced in 5 dogs. Evaluation by Doppler ultrasonography was performed for 5 days. On the 5th day, Doppler examination was repeated at 30 and 60 minutes after administration of mannitol to obstructed dogs. After induction of left ureteral obstruction, the RI of the left kidney increased significantly over 5 consecutive days. Administration of mannitol decreased the RI in the nonobstructed contralateral kidneys, and thus the RI difference between obstructed and nonobstructed kidneys was increased above normal (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001). In conclusion, administration of mannitol may be useful as another diuretic agent to identify unilateral ureteral obstruction on Doppler sonographic examination.
Objective Because acute renal failure (ARF) is frequent in septic shock, an early marker of ARF c... more Objective Because acute renal failure (ARF) is frequent in septic shock, an early marker of ARF could impact on management of such patients. High renal arterial resistive index (RI) is associated with parenchymatous renal failure. We assessed whether Doppler-measured RI on day 1 (D1) of septic shock can predict ARF. Design Prospective descriptive clinical study. Setting A 20-bed medical intensive care unit in a university hospital. Patients All patients with septic shock, excluding those with chronic renal failure (serum creatinine > 120 μmol/l). Measurements and results RI was determined during the first 24 h (D1) following vasopressor introduction, concomitant with recording of: age, SAPS II, mean arterial pressure, arterial lactate, catecholamine (dose and type), urine output and serum creatinine. ARF was diagnosed according to the RIFLE classification. RI measurement was possible for 35 of 37 included patients. On day 5 (D5), 17 patients were without ARF (RIFLE-0 or R) and 18 patients were classified as having ARF (RIFLE-I or F). On D1, RI was higher in these latter 18 patients (0.77 ± 0.08 vs. 0.68 ± 0.08, p < 0.001). They also had higher SAPS II and arterial lactate concentration. RI > 0.74 on D1 had a positive likelihood ratio of 3.3 (95% CI 1.1–35) for developing ARF on D5. RI correlated inversely with mean arterial pressure (ρ = –0.48, p = 0.006) but not with catecholamine type or dose or with lactate concentration. Conclusion Doppler-based determination of RI on D1 in septic shock patients may help identify those who will develop ARF.
... The highest frequency probe that gives measurable waveforms should be used, supplemented by c... more ... The highest frequency probe that gives measurable waveforms should be used, supplemented by color or power Doppler sonography as necessary for vessel localization. ... of renal function withcolor Doppler ultrasound in autosomal dominant polycystic kidney disease. ...
Recent clinical studies using duplex Doppler sonography identified an alteration in renal arteria... more Recent clinical studies using duplex Doppler sonography identified an alteration in renal arterial blood flow in obstructed hydronephrotic kidneys that reportedly can be used to distinguish obstructive from nonobstructive collecting system dilatation. We attempted to verify these clinical findings and establish the temporal relationship of the alteration in the Doppler spectrum to the onset of urinary obstruction by evaluating surgically induced urinary obstruction in dogs. We performed laparotomies on 11 dogs, with the left ureter isolated and ligated in five dogs, and left intact in six dogs (control group). Duplex Doppler examination of the left renal arteries performed nine times during the first postoperative month identified a statistically significant difference (p less than .05) in the Doppler resistive index calculation between the two groups on days 1, 2, 4, and week 4. A resistive index discriminatory threshold of 0.7 (greater than 0.7, obstructed; less than 0.7, nonobstructed) produced a test sensitivity of 74% and specificity of 77%. We conclude from our study that renal arterial duplex Doppler sonography can detect a change in renal perfusion as a result of urinary obstruction and that this change can be detected as early as 24 hours after obstruction. However, high false-positive and false-negative rates may limit the ability of this modality to reliably distinguish obstructive from nonobstructive collecting system dilatation.
The resistive index (RI), an ultrasonographic method of evaluating intrarenal resistance to blood... more The resistive index (RI), an ultrasonographic method of evaluating intrarenal resistance to blood flow, may be used to aid in diagnosis of renal failure. Values for arcuate artery RI, expressed as mean +/- two standard deviations, were obtained in clinically normal female dogs sedated with atropine, acepromazine maleate, diazepam, and ketamine hydrochloride. No statistically significant differences were noted between the values for the right kidney (0.33 to 0.57) versus the left kidney (0.32 to 0.56); however, the values were statistically significantly lower than values reported for nonsedated, normal dogs.
Purpose We investigated the role of the renin-angiotensin system on intrarenal hemodynamics in ch... more 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.
Results of studies on the accuracy of the resistive index as a predictor of acute renal transplan... more Results of studies on the accuracy of the resistive index as a predictor of acute renal transplant rejection have varied widely. Clinical evaluations are limited by the inability to control the numerous coincidental factors that affect vascular resistance. We performed a controlled study in dogs to isolate the effects of acute tubular necrosis, cyclosporine toxicity, and acute rejection on the resistive index, and to compare them with a population of normal control subjects. By doing so, we hoped to identify the patterns of change in the resistive index over time and possibly explain the wide spectrum of resistive index data reported in the literature. Resistive index, a parameter calculated from relative systolic and diastolic velocity, indicates parenchymal resistance to perfusion. Since an increase in renal length also has been reported useful in predicting rejection, we studied changes in length in each of the isolated conditions. The normal control group (four dogs) had heterotopic autotransplantation with minimal cold ischemic time. The acute tubular necrosis group (six dogs) had heterotopic autotransplantation with 1 hr of warm ischemic time. The cyclosporine toxicity group (four dogs) was allowed approximately 3 months to heal from heterotopic autotransplantation. Very high (toxic) doses of cyclosporine were then administered. The acute rejection group (five dogs) had heterotopic allografting with minimal cold ischemic time. No medications were administered. In all groups, the abnormalities induced were confirmed by biopsy. Creatinine levels were also used to monitor cyclosporine toxicity. In the normal control and acute tubular necrosis groups, resistive index increased immediately after surgery, returning to baseline within 10 days. Renal length increased slightly in both groups, but the duration of increase was longer in the acute tubular necrosis group. No significant change in resistive index or renal length was seen in the cyclosporine toxicity group. In the acute rejection group, an initial decrease in resistive index during the mild to moderate phase was followed by a rapidly progressive increase with worsening rejection. Renal length increased progressively beginning immediately after surgery. Our study determined the patterns of change in resistance and renal length over time as caused by the isolated pathologic states. Our finding that vascular resistance decreased in mild to moderate acute rejection was unexpected, since almost all the literature reports resistive index elevation. This may explain some of the conflicting results obtained in Doppler investigations of rejection. Our results on renal length reinforce the positive clinical reports of its predictive value in rejection.
... I6 This results in a From the Departments of Radiological Health Scienccs (Morrow, Wrig-ley) ... more ... I6 This results in a From the Departments of Radiological Health Scienccs (Morrow, Wrig-ley) and Clinical Sciences (Salman, Lappin), College of Veterinary Med-icine and Biomedical Sciences, Colorado State University, Ft. Collins, CO 80523. ...
Most renal transplants fail because of chronic allograft nephropathy or because the recipient die... more Most renal transplants fail because of chronic allograft nephropathy or because the recipient dies, but no reliable factor predicting long-term outcome has been identified. We tested whether a renal arterial resistance index of less than 80 was predictive of long-term allograft survival. The renal segmental arterial resistance index (the percentage reduction of the end-diastolic flow as compared with the systolic flow) was measured by Doppler ultrasonography in 601 patients at least three months after transplantation between August 1997 and November 1998. All patients were followed for three or more years. The combined end point was a decrease of 50 percent or more in the creatinine clearance rate, allograft failure (indicated by the need for dialysis), or death. A total of 122 patients (20 percent) had a resistance index of 80 or higher. Eighty-four of these patients (69 percent) had a decrease of 50 percent or more in creatinine clearance, as compared with 56 of the 479 patients with a resistance index of less than 80 (12 percent); 57 patients with a higher resistance index (47 percent) required dialysis, as compared with 43 patients with a lower resistance index (9 percent); and 36 patients with a higher resistance index (30 percent) died, as compared with 33 patients with a lower resistance index (7 percent) (P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 for all comparisons). A total of 107 patients with a higher resistance index (88 percent) reached the combined end point, as compared with 83 of those with a lower resistance index (17 percent, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). The multivariate relative risk of graft loss among patients with a higher resistance index was 9.1 (95 percent confidence interval, 6.6 to 12.7). Proteinuria (protein excretion, 1 g per day or more), symptomatic cytomegalovirus infection, and a creatinine clearance rate of less than 30 ml per minute per 1.73 m2 of body-surface area after transplantation also increased the risk. A renal arterial resistance index of 80 or higher measured at least three months after transplantation is associated with poor subsequent allograft performance and death.
The renal resistive index (RI) value of 0.73 has been proposed as the upper limit in normal adult... more The renal resistive index (RI) value of 0.73 has been proposed as the upper limit in normal adult dogs. In humans, changes in RI with age are associated with plasma renin activity. There are relatively few equivalent reference data for dogs. We obtained reference RI data from 22 clinically healthy dogs <4 months of age and 33 healthy dogs between 4 months and 7 years of age. An association between the RI and plasma renin activity was investigated. The mean RI in the older dogs was 0.65 ± 0.05 vs. 0.75 ± 0.05 in dogs <4 months of age. The mean plasma renin activity in the older dogs was 1.18 ± 1.03 vs. 4.23 ± 3.09 ng/ml/h in dogs <4 months of age. There was a weak linear relationship between the RI and plasma renin activity (r2=0.280, P<0.01) in dogs <4 months of age. Also in these younger dogs, RI was negatively correlated with age (r2=0.682, P<0.01). The RI was higher in dogs <4 months of age than in older dogs. Therefore, the mean renal RI is slightly higher in young dogs than reported for an older population and interpretation of the RI must include an assessment of patient age.
In human beings, intrarenal blood flow impedance, expressed as the resistive index (RI) and obtai... more In human beings, intrarenal blood flow impedance, expressed as the resistive index (RI) and obtained by duplex Doppler ultrasonography, has been used to aid in diagnosis and prognosis of renal failure. Higher than normal values for RI were obtained in 3 of 4 dogs with acute tubular necrosis (ATN) and in 5 of 10 dogs with glomerulonephrosis (GN). Normalization of RI was observed in 2 dogs with ATN evaluated serially during treatment. Increased RI values were obtained in 9 of 10 cats with nonobstructive renal disease and in 2 of 5 cats with obstructive renal disease. Normalization of RI was observed in 3 cats with renal failure in which treatment was effective (1 with obstruction; 2 with nonobstructive disease). The magnitude of increase in RI did not correlate with the magnitude of concurrent renal dysfunction. These results suggest that duplex Doppler evaluation of intrarenal RI is more useful as an ancillary diagnostic technique in azotemic dogs with ATN than in those with GN and in azotemic dogs with nonobstructive than in those with obstructive disease.
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