Ultrasound detection of differences in density. Explanation of the ureteric jet phenomenon and implications for new ultrasound applications

Optimization of ultrasonographic ureteral jet detection and normal ureteral jet morphology in dogs

Ureteral jets are visualized with ultrasound as echogenic streams extending from the ureterovesicular junction into the urinary bladder. In clinical practice, diuretics are sometimes administered to increase visibility of ureteral jets, however this has not been well described in the veterinary literature. The purpose of this prospective, crossover study was to describe the normal morphology of canine ureteral jets, determine an optimal protocol for diuretic administration to increase visibility of ureteral jets, and confirm in vitro the effect that differences in specific gravity and velocity have on visibility. Ultrasound of 10 normal dogs was performed at baseline and following 1 mg/kg furosemide administered intravenously or subcutaneously. Increased numbers of ureteral jets were seen post-furosemide administration compared to baseline, with an overall increased number of ureteral jets identified following intravenous administration when compared to subcutaneous administration. Time to first ureteral jet was significantly shorter with intravenous compared to subcutaneous administration. Urine specific gravity significantly decreased following furosemide administration. For the in vitro study, saline solutions of varying specific gravities were infused into a bath of hypertonic saline with specific gravity of 1.037. There was good visibility in vitro with infusion of solutions of specific gravities of 1.010-1.025. Infusion of saline solution with a specific gravity of 1.030 had reduced visibility, while infusion of saline with equivalent specific gravity (1.037) was not visible with B-mode ultrasonography. Both intravenous and subcutaneous furosemide administration significantly increase ureteral jet detection with ultrasound secondary to differences in specific gravity, confirming results of prior studies.

Development of a Novel Nomogram and a Simple Scoring System Using Ureteral Jet Flow to Predict Impacted Ureteral Stone

PURPOSE

To examine the efficacy of ureteral jet flow measured by Doppler ultrasonography (USG) together with radiological parameters obtained by non-contrast enhanced computed tomography (CT) in predicting whether a ureteral stone is impacted.

MATERIAL-METHOD

A total of 178 patients that met the criteria were included in the study. Stone size, location, grade of hydronephrosis, HU values of the stone and the proximal and distal parts of the stone, and ureteral wall thickness (UWT) were obtained from non-contrast enhanced abdominal CT images. Ureteral jet flows (Vmax) were measured and recorded by Doppler USG. Thirty-eight cases in which the guide wire or opaque contrast material could not pass beyond the stone were included in the impacted ureteral stone (IUS) group while the remaining 140 patients constituted the non-impacted ureteral stone (non-IUS) group.

RESULTS

Significant independent predictors of IUS were determined as stone size [odds ratio (OR): 2.23, p=0.020), ureteral HU value under the stone (OR: 1.11, p=0.014), UWT (OR: 5.66, p=0.009), anteroposterior diameter (OR: 1.23, p=0.033), and the Vmax value of the stone side (OR: 0.76, p=0.011). The proposed scoring system predicted IUS with 89% sensitivity and 91% specificity at a cut-off value 11.5.

CONCLUSION

Determining whether a ureteral stone is impacted is important in deciding on the optimal treatment modality. The nomogram and scoring system that we created based on the data which were obtained with non-invasive methods can predict IUS with high sensitivity and specificity.

Evaluation of the ureteral jet in dogs by using color Doppler ultrasonography

Ureteral jets are the result of a forceful ejection of urine from the vesicoureteral junction into the urinary bladder. By using color Doppler ultrasonography (US), we aimed to identify distinct ureteral jets in dogs, provide insight into ureteral obstruction, and facilitate study of urodynamics and vesicoureteric sphincter function via pulsed Doppler US. Color Doppler US was applied to detect urinary flow from the right ureteral orifices in eight healthy beagles. Under anesthesia, 0.9% saline (2.5 mL/kg/h) and furosemide (0.5 mg/kg) were administered intravenously to assist in detection of distinct ureteral jets and examine their frequency, velocity, duration, and waveform. In all dogs, ureteral jets were visualized under diuresis and anesthesia within 2 to 5 min (mean 3.57 ± 0.90 min) of the furosemide injection. Mean frequency, peak velocity, and duration of right ureteral jets in seven dogs in whom six ureteral jet waveform patterns were identified were 9.86 ± 3.09 jets/min, 34.07 ± 10.02 cm/sec, and 2.82 ± 1.08 sec, respectively. During the 10 min period starting 10 min after the initial jet appeared, only three waveforms were identified. Color Doppler US of ureteral jets may aid in assessing vesicoureteric sphincter function and ureteral abnormalities, such as ureteral obstruction, in dogs.

The role of ultrasound in renal insufficiency: the essentials

Sonography is the best screening modality to evaluate patients presenting with renal insufficiency. Ultrasound findings can be normal in patients with renal disease, especially in prerenal azotemia and acute parenchymal renal disease. Echogenic kidneys indicate the presence of parenchymal renal disease; the kidneys may be of a normal size or enlarged. Small kidneys suggest advanced stage chronic kidney disease. Uncommonly, cystic disease of the kidney, especially adult type polycystic kidney disease may be the cause of the patient's renal insufficiency with bilaterally enlarged kidneys containing multiple cysts of various sizes. If hydronephrosis is present, the level and cause of the obstruction should be sought. When ultrasound cannot diagnose the level and cause of obstruction, other imaging modalities, including CT and MRI may be useful. When renovascular disease (arterial stenosis or venous thrombosis) is suspected, spectral and color Doppler can be useful in detecting abnormalities.

Noninvasive assessment of patency of internal ureteral stent: role of colour Doppler ultrasound

OBJECTIVE

To compare colour Doppler ultrasonography (CDU) and retrograde cystography in the assessment of the patency of internal ureteral stents.

PATIENTS AND METHODS

Thirty-two patients with 33 internal ureteral stents were evaluated for patency of the internal ureteral stent using both CDU and retrograde cystography. Real-time ultrasonography and CDU were performed before retrograde cystography. Stent patency was defined as seeing flow from the distal end of the stent in the urinary bladder or iodinated contrast in the renal pelvis. The two investigators had no prior knowledge of the other's results. After completion of both investigations, stent patency was proved by direct inspection of the stent after removal.

RESULTS

Both investigations showed the same result in 27 of the 33 stents. Stent patency was found if either investigation was positive. The accuracies of retrograde cystography, CDU and both were 73%, 79% and 85%, respectively.

CONCLUSIONS

CDU is a noninvasive method with high accuracy. Detection of flow at the distal end of the stent is helpful, but absence of flow may or may not indicate an obstructed stent and further investigation should be performed.

On the relationship between power mode and pressure amplitude decorrelation

Estimation of mean transit time, along with tissue blood volume, are important factors in determining soft tissue perfusion. Recently, power mode decorrelation techniques have been successfully used to estimate mean transit time of red blood cells or contrast material through a region-of-interest (ROI) both in laminar flow phantoms and in vivo. The previously described theory for power mode decorrelation derives from a phenomenological stochastic differential equation (Langevin equation) based on conservation of matter, relating the detected signal power to the measured rate of decorrelation. Given the experimental support for power mode decorrelation as a method to estimate mean transit time, it becomes important to determine the relationship between the phenomenological parameters that appear in the corresponding stochastic equation and system parameters, such as the transducer point response function. With this equation as a starting point, and using the fact that the pressure amplitude is a Gaussianly distributed random process, the following stochastic differential equation for the pressure amplitude p(t) is derived, a necessary first step in establishing the relationship between the measured decorrelation rate and system parameters (i.e., point response function): dp(t)/dt = -(v/2+2ik x v)p(t)+f(t), where v/2 represents the rate of decorrelation, 2k x v is the Doppler shift for an insonating wave vector k and particle velocity v.f(t) is a stationary, white noise Gaussian random process.

Evaluation of ureterocele with Doppler sonography

Ureterocele is a common disorder characterized by cystic dilatation of the terminal submucosal portion of 1 or both ureters. Conventional imaging modalities for the diagnosis of ureterocele include intravenous urography and voiding cystourethrography; gray-scale sonography, augmented by color Doppler and spectral analysis studies, can be useful in diagnosing and managing this condition as well. We describe the diagnosis of ureterocele using transvaginal gray-scale and color Doppler sonography with spectral analysis in 2 women. Color Doppler sonography demonstrated urine flow into the bladder, and spectral analysis was used to measure the flow velocity. Together, these modalities can provide additional information about urinary flow dynamics, aid in implementing treatment for patients with ureterocele, and eliminate the need for invasive diagnostic procedures.

Ultrasonography of the ureters

It is difficult to visualize the normal canine or feline ureters ultrasonographically; however, diagnosis of various abnormalities associated with ureteral dilation is possible in many instances. Ultrasonography is a practical method for diagnosis of ectopic ureter, ureterocele, and certain causes of ureteral obstruction that compares favorably with contrast radiography because it is quicker, does not involve use of contrast media or ionizing radiation, and usually requires no sedation or anesthesia. Ultrasonography is a convenient method for examining adjacent organs, principally the kidneys and bladder, that may be affected in animals with ureteral abnormalities. Also, ultrasound guidance facilitates certain interventional diagnostic procedures for the ureters.

Ultrasonographic findings in 14 dogs with ectopic ureter

To evaluate ultrasonography as an alternative to contrast radiography for diagnosis of ectopic ureter in dogs, ultrasonography of the urinary tract was performed prospectively in a series of urinary incontinent dogs anesthetized for contrast radiography. Fourteen dogs had ectopic ureter based on surgical, necropsy or unequivocal contrast radiographic findings. There were eight females and six males of a variety of breeds; five were Labrador retrievers. Mean (range) age at the time of diagnosis was 1.2 (0.2-4) years for females and 3.5 (0.3-5) for males (p < 0.05). Ectopic ureters were unilateral in five dogs (2 left; 3 right) and bilateral in nine dogs. Both ultrasound images and contrast radiographs were positive for 21 (91%) ectopic ureters; the same two ectopic ureters were not detected using either modality. The termination of each of the five normal ureters was visible on ultrasound images; two (40%) were visible on radiographs. Other ultrasonographic findings included dilatation of the ectopic ureter and/or ipsilateral renal pelvis in ten (43%) instances, evidence of pyelonephritis in two dogs (with enlargement of the contralateral kidney in one dog), and urethral diverticuli in one dog. Ultrasonography is a practical diagnostic test for ectopic ureter in dogs. In this series there was close correlation between the ultrasonographic and contrast radiographic findings for each ectopic ureter, but ultrasonography enabled more accurate determination of normal ureteral anatomy.

The ureteric jet index: a novel measure of divided renal function

The aim of this study was to evaluate an index of divided renal function based on the quantification of the ureteric jets seen on colour Doppler ultrasound of the bladder. Thirty-one patients attending for scintigraphic renography underwent colour Doppler ultrasound with video recording for 5 min. Divided renal function was calculated as the proportion of jets from the right-sided orifice ('jet index'). This was compared with the corresponding 'scintigraphic index' found using Patlak-Rutland graphical analysis. Absolute discrepancies were calculated. Twenty-eight of thirty-one (90%) of studies were diagnostic for the calculation of jet indices. The mean jet index was 52% (n=28, SEM=5.8%) compared to a mean scintigraphic index of 54% (n = 28, SEM = 4.0%). The two scores were correlated, with a correlation coefficient of 0.72 and the median absolute difference between the two scores was 7.7%. Forty-three per cent (12/28) of subjects had discrepancies in the two scores of 5% or less. The score differences, however, showed a highly skewed distribution with 32% (9/28) subjects showing discrepancies over 20%. This discordant group (> 20% difference) included three patients with functional pelviureteric obstruction, one with a pelvic mass and one with an underfilled bladder. Two patients with very poor quality jets had impaired renal function. In one case, the index improved after angioplasty for renal artery stenosis. This simple test is a useful adjunct to urinary tract ultrasound but should be interpreted alongside evidence of renal obstruction, and complements rather than replaces existing tests.