Duplex Doppler estimation of resistive index in arcuate arteries of sedated, normal female dogs: implications for use in the diagnosis of renal failure.

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.

Estimation of arcuate artery resistive index as a diagnostic tool for aminoglycoside-induced acute renal failure in dogs.

OBJECTIVE: 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. ANIMALS: 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. PROCEDURE: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.

Gray-scale sonographic characterization of aminoglycoside-induced nephrotoxicosis in a canine model.

RATIONALE AND OBJECTIVES: The diagnostic usefulness of gray-scale sonography was evaluated in a canine model of aminoglycoside-induced nephrotoxicosis. METHODS: Sonography was performed before and during the onset and progression of nephrotoxicosis induced by administration of a toxic dosage of gentamicin. Subjective visualization of increased renal cortex echogenicity (IRCE) was objectified with digital image analysis methods. Results of both subjective and objective evaluation were correlated with clinicopathologic tests and renal cortex biopsy obtained concurrently. RESULTS: Subjective visualization of IRCE was associated with significant nephrotoxicosis and was superior to serum creatinine elevation in nephrotoxicity detection. Objective detection of IRCE improved nephrotoxicity detection sensitivity to that of increased urine enzymuria. CONCLUSIONS: Based on the above results, subjective visualization of IRCE in patients with aminoglycoside-induced nephrotoxicity may occur before azotemia and is suggestive of significant renal dysfunction; application of digital image analysis methods may lead to earlier sonographic recognition of nephrotoxicity.

Color Doppler sonography of transjugular intrahepatic portosystemic shunts (TIPS).

Transjugular intrahepatic portosystemic shunts (TIPS) have largely replaced surgically created shunts in the treatment of life-threatening sequelae of portal venous hypertension [1-5]. Conventional duplex and color Doppler sonography are proving to be useful tools in the assessment of the stents and their associated hemodynamic changes [2-5]. A thorough Doppler survey before and immediately after TIPS placement provides a baseline for evaluation of shunt function and procedure-related complications. Routine follow-up studies at regular intervals after the procedure provide noninvasive assessment of shunt patency and late complications. This pictorial essay illustrates the anatomic and hemodynamic abnormalities present with portal hypertension before TIPS and discusses the expected duplex and color Doppler findings after TIPS. The sonographic characteristics of immediate and delayed complications, as well as potential diagnostic pitfalls, are discussed.

Duplex and color Doppler sonography of complications after percutaneous interventional vascular procedures.

Duplex and color Doppler sonography have proved to be excellent noninvasive modalities for evaluating complications of percutaneous interventional vascular procedures. Complications including hematoma, pseudoaneurysm, arteriovenous fistula, thrombosis, stenosis, and vessel occlusion are routinely diagnosed with Doppler sonography. Hematomas exhibit variable echogenicity and internal complexity but never demonstrate internal blood flow. A pseudoaneurysm is a contained extravasation of blood that, unlike a hematoma, maintains a patent vascular connection with the injured vessel. Puncture-related arteriovenous fistulas are false vascular channels between an adjacent artery and vein that demonstrate low-resistance arterial signal, high-velocity venous outflow, and variable flow patterns within themselves. Narrowing in a stent demonstrates high-velocity turbulent flow with conventional Doppler and color aliasing with color Doppler techniques. Thrombus can be seen directly as a mural-based or luminal defect; however, it is often alterations in color flow dynamics, waveform characteristics, and flow velocities that permit conclusive diagnosis. Early experience in evaluation of stent stenosis in patients with transjugular intrahepatic portosystemic shunts suggests that low-velocity shunt flow indicates stenosis, likely related to the presence of low-resistance collateral pathways. Familiarity with both the interventional procedures and their possible complications facilitates prompt diagnosis and treatment.

Postoperative diuresis renography and ultrasound in patients undergoing pyeloplasty. Predictors of surgical outcome.

The authors reviewed 50 pediatric patients (56 renal units) who underwent pyeloplasty and had serial preoperative and postoperative diuresis renogram and ultrasound studies. Of those patients that clinically improved with surgery, 73% and 91% showed improved renographic patterns in postoperative studies at 3 and 12 months, respectively. Ultrasound demonstrated more gradual improvement in grade and pelvic diameters over longer study intervals. Diuresis renography is an excellent predictor of surgical outcome within 3 months of pyeloplasty and showed change well in advance of that seen on ultrasound. Sonography is better suited to longer term evaluation of grade, pelvic diameter, and renal size.

Early sonographic evaluation of the transjugular intrahepatic portosystemic shunt (TIPS).

The purpose of this study was to evaluate duplex and color Doppler findings in patients before and within 24 h after transjugular intrahepatic portosystemic shunts (TIPS). Conventional duplex and color Doppler were used in the assessment of 19 patients who underwent TIPS as part of a prospective protocol. Patients were examined within 24 h before and after the procedure. Before TIPS, patency, flow direction, and peak flow velocity in the main portal vein and hepatic artery were studied, as well as patency and flow direction in hepatic veins, splenic vein, and inferior vena cava (IVC). Immediately after the procedure, sonographic identification of stent position, shunt patency, and flow dynamics were evaluated and patency and flow direction of hepatic veins, splenic vein, and IVC were determined. The portogram performed at the end of the procedure was compared with the 24-h sonographic studies after TIPS to determine sonographic/angiographic correlation. No intraparenchymal abnormalities or perihepatic fluid collections were detected after the procedure. The metallic stent was clearly seen in all patients. Mean peak shunt flow velocities were 139 +/- 50 cm/sec within 24 h after TIPS. Absence of flow through the shunt was correctly identified in one case and confirmed angiographically. Mean peak flow velocity in the portal vein before TIPS was 22 +/- 13.6 cm/sec and increased to 43.6 +/- 9.1 cm/sec after TIPS (p < 0.05). The hepatic artery peak systolic velocity increased from 77 +/- 51 cm/sec before TIPS to 119 +/- 53 cm/sec after the procedure (p = 0.029).(ABSTRACT TRUNCATED AT 250 WORDS)

Duplex and color Doppler sonography of hemodialysis arteriovenous fistulas and grafts.

Surgically constructed Brescia-Cimino arteriovenous fistulas and synthetic loop grafts are common means of vascular access for hemodialysis. Although angiography has been the traditional method of imaging these vascular systems, duplex and color Doppler sonography offer a noninvasive method of evaluating dysfunctional hemodialysis access. In normally functioning fistulas, waveforms of flow in the supply arteries and throughout the graft are monophasic, with peak systolic velocities of 100-400 cm/sec and end-diastolic velocities of 60-200 cm/sec. The draining veins have arterial pulsations with peak velocities of 30-100 cm/sec. Arterial and venous stenoses, graft thrombosis (occlusive and nonocclusive), infection, aneurysm and pseudoaneurysm formation, and arterial steal are relatively common abnormalities that can threaten or destroy graft function and can be diagnosed sonographically. Although abnormal hemodynamics in access fistulas are usually detected during hemodialysis, sonographic evaluation at the time of initial dysfunction may reveal an underlying correctable abnormality, and specific therapy may be instituted before the condition progresses. In addition, use of sonography may obviate an invasive angiographic examination if no significant hemodynamic problem is present.

Effects of central venous catheter placement on upper extremity duplex US findings.

PURPOSE: The upper extremity veins of 17 patients who underwent operative central venous catheter placement were studied prospectively with color duplex sonography to determine which duplex changes, if any, could be due to the presence of the catheter alone and to determine if these waveform changes could mimic the dampened waveform seen peripheral to central nonvisualized or nonocclusive thrombosis or proximal stenosis. PATIENTS AND METHODS: The subclavian, internal jugular, and brachiocephalic veins were examined with color duplex sonography immediately before and after catheter placement. Images obtained before and after catheterization were reviewed by two radiologists for (a) spectral broadening in both the vein of insertion and the brachiocephalic vein, (b) transmission of atrial pulsations, and (c) respiratory phasicity. RESULTS: In all cases, atrial pulsatility and respiratory phasicity were present before and after catheter placement. There was no statistically significant change in the amount of spectral broadening after catheter placement. A mild increase in the peak blood flow velocity of 7 cm/sec (P = .04) in the ipsilateral brachiocephalic vein was demonstrated; however, no significant increase in velocity could be shown in the vein of insertion. CONCLUSION: In this clinical setting, the hemodynamic changes within the vein from the catheter placement are minimal. Any damping of the venous waveform seen with sonography performed to rule out upper extremity deep venous thrombosis secondary to indwelling catheter--for example, loss of atrial pulsatility or respiratory phasicity--is presumably due to the presence of venous thrombosis or stenosis.

Sonography of the upper extremity and jugular veins.

Color Doppler sonography is a useful technique for rapid, noninvasive evaluation of venous disease in the upper extremity. It has been used successfully to evaluate thrombosis related to indwelling central catheters. In addition, Doppler sonography shows promise for monitoring thrombolytic therapy after "effort thrombosis" and detecting intermittent venous compression related to thoracic outlet syndrome.

Assessment of vascular complications of renal, hepatic, and pancreatic transplantation.

The assessment of the vasculature of the transplant recipient is complex; current emphasis is on utilization of noninvasive techniques, particularly conventional and color duplex sonography. These examinations reduce the need for diagnostic angiography, and their findings provide crucial information with regard to vascular complications seen after transplantation, such as arterial or venous stenosis or occlusion, arteriovenous fistulas, and pseudoaneurysms. However, the complexity of the clinical settings of these vascular complications often makes other noninvasive examinations, as well as angiography, necessary. Some complications are common to all three types of transplantations, but some, such as graft thrombosis in pancreatic transplantation, predominate in one particular type of transplant. Use of imaging is also important in identifying candidates for liver transplantation. In addition, access for therapeutic radiologic intervention can be provided with diagnostic angiographic procedures.

The nature of the life concept across the life-span.

In this study of people ranging from six to over sixty-five years of age, a high frequency of animistic responses was found in all ages examined. While a significant age effect was noted in the ability to categorize animate objects accurately, animistic responding was generally unrelated to logical classification ability or to analytic cognitive style. For eleven- to thirteen-year-olds, however, a significant relationship between animism and both cognitive style and classification ability existed. An interpretation of the results which found high levels of animistic thinking beyond adolescence does not support Piagetian theory. Rather, adults may respond animistically because of emotional attachments which they have formed to a certain meaningful physical objects.

The life concept in female college students: An exploratory analysis.

In the present study a two-part animism questionnaire was devised and administered to 200 female undergraduate students who had fairly extensive course backgrounds in science. When these students were asked to classify each of 15 objects as "living" or "nonliving," 67% (N=134) gave evidence of apparent animistic thought. Yet when the subjects were asked to choose which of several statements reflected their own definition of living, 66% (N=132) claimed that "only plants and animals are living." Scientific background did not relate to performance on either section of the questionnaire. Results indicate that although the primary orientation of many young adults toward the word living is not a biological one, most college students areable to classify stimuli according to this criterion.