J.
Holly
Burge,
MD2
William
#{149}
D. Middleton,
MD
Bruce
#{149}
L. McClennan,
Ureteral Jets in Healthy Subjects and in Patients with Unilateral Calculi: Comparison with Color Color Doppler ultrasound was used to image the ureteral jets in 17 healthy subjects and 26 patients with ureteral calculi proved with intravenous urography. In patients with ureteral calculi, three patterns of ureteral jets were seen: no detectable urine flow from the symptomatic side (12 patients), low-level continuous flow from the symptomatic side (four patients), and periodic ureteral jets on the symptomatic side that were not significantly different from ureteral jets of healthy subjects (10 patients). Of the 12 patients with high-grade obstruction on urograms, 11 had ureteraljets significantly different from those of healthy subjects (either no detectable ureteral jets or continuous low-level jets on the symptomatic side). Only three of the 11 patients with low-grade obstruction or nonobstructing stones had ureteral jets that were different from those of healthy subjects. It is concluded that analysis of ureteral jets with color Doppler can enable detection and qualitative determination of the degree of ureteral obstruction in many patients with unilateral ureteral calculi. Index studies stenosis
terms: Ultrasound #{149} Ureter, calculi, or obstruction,
(US), Doppler 82.811, 82.844 #{149}Ureter, 82.84 #{149}Ureter, US stud-
ies, 825.12984 Radiology
I
1991;
Institute
of
Radiol-
Washington University School of Medicine, 510 S Kingshighway Blvd, St Louis, MO 63110. Receivedjuly 27, 1990; revision requested September 14; revision received December 27; accepted April 1, 1991. Address reprint requests to W.D.M. 2 Current address: Wake Radiology, Raleigh, ogy,
NC. #{176}RSNA,1991
detection of ureteral jets entering the bladder is a well-described procedure (1,2). 5everal groups have recently studied the relationship between ureteral jets and vesicoureteral refiux in children (3,4). However, little attention has been focused on the effect of urinary tract obstruction on the ureteraljet phenomenon. This study was undertaken to determine the color Doppler ultrasound (US) characteristics of ureteral jets in patients with ureteral calculi.
PATIENTS
AND
METHODS
From September 1989 to June 1990, color Doppler US was performed in 29 patients (10 women and 19 men) with urographic documentation of ureteral calculi. Their ages ranged from 25 to 77 years (mean age, 44 years). The results of the intravenous urogram in all patients except one were known to the examiners prior to the color Doppler examination. During this period, some patients received treatment for ureteral stones without undergoing either intravenous urography (IVU) or ureteraljet study. Most of these patients were seen in the emergency room during evening hours. Eighteen healthy volunteers (seven women and 11 men), aged 26-39 years (mean age, 29 years), underwent examination also. All examinations were performed by means of a commercially available unit Advanced
Technology
Charles
Lab-
Bothell, Wash) with a 3-MHz phased-array transducer. A low pulse-repetition frequency (1,500 Hz), moderate receiver gain, and moderate output were used to optimize visualization. The wall ifiter was set at 50-100 Hz. Flow toward the transducer was assigned a red color. The bladder was examined in the transverse plane to simultaneously view the left and right ureteraljets at the level of the trigone. All patients received oral hydration, intravenous hydration, or both (depending on whether an intravenous catheter was already in place) until ureteral jets were easily detected on the asymptomatic side. Generally this deteclion required 600-1,000 mL of water prior to the study. Ureteral jets could usually be
F. Hildebolt,
#{149}
Ureteral Doppler
ONOGRAPHIC
(Ultramark-9; oratories,
180:437-442
From the Mallinckrodt
S
MD
PhD
US’ minutes
hydration. not detected hydration, the patients were asked to drink more water, and delayed scans were obtained. All subjects underwent scanning for at least 5 minutes, and the examination was videotaped for subsequent review. Range-gated pulsed Doppler analysis of the ureteral jets was not visualized
15-30
Whenever after initial
ureteral
attempted kidneys
in any
after
jets were
of these
patients.
Both
were scanned prior to ureteral jet evaluation to assess the degree of hydronephrosis. Kidneys were assessed with both US and urography for any discrepancy in size that might cause one to suspect impaired function. The number of jets from each ureteral orifice was tabulated over time so that the number ofjets per minute could be calculated. Percentage differences between the number of ureteral jets from the left orifice and the number from the right orifice were cakulated by dividing the difference between those from the left orifice and those from the right orifice by the sum of those from the left and those from the right and multiplying by 100%. The presence or absence of left-to-right symmetry in ureteral jet frequency and appearance was ascertained in each patient. All patients were then categorized into three groups. Group I consisted of patients with no ureteral jets on the symptomatic side. Group H consisted of patients with continuous low-level ureteral jets on the symptomatic side. Group HI consisted of patients with ureteral jets similar to those of healthy subjects. In the healthy subjects and patients in groups I and III, multiple, two-tailed, Student t tests with corrections for inequality of variances were performed to test for statistically significant differences in ureteral jet frequency.
All examinations were performed within 24 hours of IVU except in one patient, whose examination was done within 72 hours
of WU.
WU
was
the standard
for
and position and determining the degree of obstruction and hydronephrosis. High-grade obstruction was defined as an obstruction that delayed visibility of the pyelogram for 12 minutes measuring
Abbreviation:
stone
size
P/U
=
intravenous
urography.
437
1.
Figure
Normal
nor and medial
ureteral
jets. (a) Transverse view of bladder shows ureteral jet arising from the left ureteral the midline. (b) Similar view shows right ureteral jet for comparison.
direction
or longer after the start of intravenous jection of contrast material. Low-grade was
obstruction
defined
in-
Table
in
Healthy
was classified as proximal, distal sydividing the ureter significant
size between
tested with multiple test for statistically
and
nonobstructing
combined group
stones
into one category
sizes.
This
degree
were
to increase
combination
is appropri-
of obstruction,
and
de-
of hydronephrosis because these parameters may have changed or did change between the time of IVU and the time of Doppler
US. Finally,
in three
pa-
the urograms could not enable accurate determination of the degree of obstruction, and these three patients were not included in the analysis of obstruction. One healthy subject and three patients with stone disease documented by means of contrast material-enhanced urography were excluded from the study secondary to inability to detect ureteral jets from eitients,
ther
ureteral
orifice.
This
inability
was
due
to inadequate hydration or inability to wait a sufficient length of time to allow the hydration to result in diuresis. Renal funclion (based on serum creatinine level) was normal in the three patients, and the 438
Radiology
#{149}
Therefore,
6.4
6.2
no history the
final
of 17 healthy ureteral
of renal study
popula-
subjects
and
calculi.
2.11-3.34/mm 2.01-3.39/mm
3.2-9.6
between
those
those
on the
are
ences
shown
on
the
left
side
right
in healthy
in Table
i. The
in jet frequency
between
sides were (P > .05).
not
subdifferleft
statistically
Subjects
subjects was cases the jets
frequency healthy
anteromedial. crossed the
In most midline. The
of jets from a single subject (left side plus
varied
from
i.5
to i2.4
jets
per
-
confidence
intervals
number of ureteral right sides and the
Patients The normal
for
jets on the percentage
total
left and differ-
appearance of the jets from the side in patients did not differ
from that of the healthy subjects except in two patients. One patient had jets that were directed vertically because an enlarged rectum distorted
the bladder,
torted
and
another
were directed an enlarged
jets that because
patient had anterolaterally
prostate
dis-
the bladder.
Patients of three side-to-side jets. The
were right
minute (mean, 5.4 jets per minute). The difference between the number of jets from the left side and the numben from the right side ranged from 0 to 5 (mean, 1.9). Expressed as a percentage of the total, the difference between the left side and right side [(left right)/(left + right) x iOO%] ranged from 0% to 20% (mean, 6.4%). The mean, standard deviation, and 95%
ence and jects
and right significant
The frequency, morphologic appearance, and direction of the ureteral jets were relatively symmetric in an individual healthy subject but varied among healthy subjects. In all cases the jets were flame-shaped, with the highest frequency shifts located at the ureteral orifice (Fig i). In many cases, the frequency shifts at the onfice were high enough to result in aliasing at a pulse-repetition frequency of i,500 Hz. The direction of the jets in all of these young healthy
side)
95% Confidence Interval
left and
had
with
Healthy
gree
color
subject
1.16/mm 1.29/mm
RESULTS
ate because these stones are more likely to be managed conservatively. Four patients who had passed their stones prior to the color Doppler ureteral jet examination were not included in the analysis of stone location,
healthy disease.
26 patients
between the three groups of patients for stone location, degree of obstruction, and degree of hydronephrosis, multiple Fisher exact tests were used (6). For stone location, proximal and midureteral stones were combined into one category to increase group sizes. For obstruction, lowgrade
Difference between right sides (%)
2.70/mm
in stone
t tests. To differences
Standard Deviation
2.73/mm
I, II, and III were Student significant
Mean Total No. of Ureteral Jets
Left Right
tion consisted
middle, and into thirds.
differences
groups
Subjects
Side
after
Statistically
in an ante-
as an obstruction
visibility of the pyelogram for the start of such injeclion. Lack of obstruction was defined as a pyelogram that appeared on the initial tomograms and was symmetric with the normal side. Hydronephrosis was graded mild, moderate, or severe on the basis of criteria established by Ellenbogen et al (5). These categories were not considered in the grading of obstruction. Stone size was calculated as the average of the largest and shortest dimensions. Stone position minutes
The jet travels
1
Findings
that delayed
4-8
orifice.
and crosses
were categorized into one distinct groups on the basis of differences in ureteral largest number of patients
in group
complete
I, in which
absence
there
of detectable
was jets
on
the affected side (12 patients). Data from this group of patients are shown in Table 2. The percentage difference between left and right ureteral jets in this group of patients was significantly different from that in the healthy subjects (P < .001). Eight of these patients jets from the were similar
the
of
(ie, the ureteral jets were separated by intervals of absent flow). In four patients in this group,
healthy
had periodic ureteral unaffected side that in all respects to those
flow
subjects
from
the
nonobstructed
August
1991
Table
2 in Group
Findings
I Patients:
No Ureteral
Total No. of Jets
Jet
Frequency (no. per minute)
Percentage
Patient
(min:sec)
R
L
R
L
1 2 3 4 5
5:00
5:15 5:13 5:14 6:00
5 29 14 27 12
0 0 0 0 0
1.0 5.5 2.7 5.1 2.0
0 0 0 0 0
6 7
6:18
9
0
1.4
0
9:19 5:14
CN 17
0 0
NA 3.2
0 0
9:00
CN
0
NA
0
6:40 9:00
0 CN
CN 0
0.0 NA
NA 0
5:00
15
0
3.0
0
continuous
normal-level
8 9 10 11 12 Note.-CN mined, R
=
right.
=
*Times in parentheses
Stone
Difference
Time
indicate
flow,
HG
=
(R
L)/(R + L)
Size
100 100 100 100 100 100 100 100 100 100 100 100
high-grade
when the IVU first showed
-
obstruction,
contrast
material
L
=
left, LG
in the collecting
=
Location
(mm)
Grade of Obstruction*
Hydronephrosis
4.0 2.0
Midureteral Distal
Moderate Moderate
HG (1 h) LG (8 min)
5.5
Proximal
3.0 4.5 4.4 4.0 4.0 3.0 53 8.0 7.0
Proximal Proximal Distal Proximal Distal Distal
Mild Mild
HG ND
Mild
HG (5 h)
Moderate Mild
HG
low-grade
Mild
Midureteral PrOximal
Moderate Moderate
obstruction,
NA
=
(3.5 h)
HG (9 h) HG(>3h) HG (20 mm) HG (> 1.5 h) HG (1 h) ND
Mild Moderate
Distal
(9 h)
not applicable,
ND
=
not deter-
system.
.
I 4
a-
-4 #{149}-:. ...
-.
,-grade
obstructioi
%
stop for 6 minutes 40 s from a video recording.
S.
Image
,.twas quality
orifice had a morphologic appearance similar to that in the healthy subjects but continued nonstop throughout the entire examination. In nine of these 12 patients, high-grade obstruclion was documented with IVU. One patient had low-grade obstruction. In two pregnant patients the severity of obstruction was not determined because of the limited number of images obtained. The degree of hydronephrosis varied; six patients demonstrated only mild hydronephrosis, and six patients, moderate hydronephrosis. The four patients in group II had continuous, nonstop flow from the affected side that was decreased in magnitude when compared with the normal periodic jets from the unaffected side (Fig 2). Three patients had mild hydronephrosis; one patient, moderate hydronephrosis. Obstruclion was low grade in two patients, Volume
180
#{149} Number
2
______
--..-
less intense is degraded
than normal, because hard
...d copy
it continued was obtained
non-
high grade in two. The data from this group are shown in Table 3. Group III consisted of 10 patients with ureteral jets that were similar to those
of the
healthy
subjects
(Table
4).
The difference between the number of jets from the left side and the number from the right side averaged four (range, one to iO), with a percentage difference of 4%-38% . The percentage differences in the left and right ureteral jets between this group of patients and the healthy subjects had a P value of .05; however, with the Bonferroni adjustment (a test of significance for multiple simultaneous comparisons), statistically
this value significant.
was
no Four
longer patients
in this group had passed stones from the ureter after IVU, prior to the ureteral jet examination. This was documented by means of straining of the urine and retrieval of the stone or sonographic visualization of the stone
in the bladder. Of the remaining six patients, four had mild hydronephrosis and two had moderate hydronephrosis. Obstruction was low grade or absent in all of these patients, except in one in whom the stone had passed prior to the color Doppler examination. In one patient it was not possible to grade the obstruction because of the limited number of images obtained. To determine whether the detection of ureteral jets was related to the degree of obstruction, the pattern in group I was compared with the pattern in group III (with nonobstructing and low-grade obstructing stones grouped into one category). Patients in whom IVU could not enable determination of the degree of obstruction and patients who had passed their stones
between
IVU
and
color
Dop-
pler examination were eliminated from the analysis. Degree of obstruction was significantly different between groups I and III (P = .002). This indicates that patients with no detectable ureteral jets on the symptomatic side are more likely to have highgrade ureteral obstruction than patients with normal ureteral jets. Similan comparisons between groups II and III (P = .17) and groups I and II (P = .18) failed to show a significant difference in the degree of obstruclion. The test for differences between groups I and III for stone location (combining proximal and midureteral stones into one category) had a P value of .04. This value was not significant (P > .05) with the Bonferroni adjustment. No statistically significant differences were found between groups I, II, and III for degree of hyRadiology
439
#{149}
Table
3
Findings
II Patients:
in Group
Continuous
Low-Level
No.
Total
ofJets
(no. per minute)
(min:sec)
R
L
R
L
Percentage Difference (R - L(R + L)
6:40 7:27 8:07
CL 12 CL CL
18 CL 13 24
NA 1.6 NA 4.3
2.7 NA 1.6 NA
NA NA NA NA
Time
Patient 1 2 3 4
5:36
Note-CL = continuouslow-levelfiow, Times in parentheses indicate when
Table
HG = high-grade the IVU first showed
obstruction, L contrast material
III Patients:
in Group
Normal
Size
Location
(mm)
2.5
Distal
Mild
4
Distal
Mild
6 3
Distal Distal
Moderate
left, LG = low-grade obstruction, in the collecting system.
Grade of Obstruction*
Hydronephrosis
HG HG LG LG
Mild
NA
not applicable,
=
R
=
(1.5 h) (>45 mm) (4 mm) (8 min)
right.
Jet
Ureteral
Frequency
Total No.
Percentage
(no. per minute)
ofJets Patient
(min:sec)
1 2
6:24
R
L
R
L
17 19
13 15’ 14
2.7 2.4 1.4 2.8
2.0 1.9 1.9 3.3
(R
-
Size (mm)
Location
13.3 11.8 16.7 8.3
4.5 10 3 3
Distal Distal Distal Distal
4 2 3
Distal Distal Passed
4.5 3 2.5
Passed Passed Passed
L)/(R + L)
5
7:54 7:12 7:50 6:13
lOt 22’ 22
26 17’
3.5
2.7
12.8
6
6:50
8t
Q.4
1.2
NA
NA
8’
18
0.8
1.8
38.5
14 8t 16’
13’ 13 19
1.3 1.3 2.8
1.2 2.0 3.4
3
4
7
8 9 10
10:05 10:44
6:23 5:40
Note.-CN = continuous normal-level nonobstructing. Times in parentheses indicate when
Symptomatic
side.
flow,
HG
and
complete
absence
of
detectable jets, whereas six of 14 distal stones caused high-grade obstruction, and five of these 14 distal stones caused complete absence of detectable jets (Table 5). This seemingly represents a clinically meaningful difference in that stone location may be associated with the degree of obstruclion and amount of urine production. However, the sample size of this study was too small to demonstrate that this difference was statistically significant. DISCUSSION Ureteral jets were first imaged with IVU (7). The jet occurs when densely opacified urine from the ureter enters the more dilute or unopacified urine in the bladder and appears as a dense stream exiting the ureteral orifice (8).
#{149} Radiology
=
high-grade
the IVU first showed
dronephrosis or stone size. However, because of the small sample size of this study, statistical validity cannot be assured, and type II errors may have been committed (that is, claiming no difference when one really exists). In fact, five proximal and middle ureteral stones produced high-grade obstruction
Stone Grade of Obstruction*
Difference
Time
440
=
Stone
4
Findings
t
Jet
Ureteral
Frequency
3.7 23.8
8.6 obstruction,
contrast
material
LG
=
low-grade
in the collecting
T 1,1 5 a e Ureteral Jets and Grade
obstruction,
NA
=
Hydronephrosis
LG (4 mm) LG (4 mm) NO NO
Mild Moderate Mild Mild Moderate Mild Moderate
ND
NO NO
Mild
NO HG (30 mm) NO
Mild
Moderate not applicable,
ND
=
not determined,
NO
=
system.
of Obstruction
Asso ciated
with
Ureteral
Stones
___________________________ Ureter
Type
of UreteralJet patients)*
Grade of Obstruction
Distal
Middle
Proximal
4 I
2 0
3 0
2 2 2 Low (2) None(3) 3 _____________________________________________________________
0 0 0 0
0 0 0 0
Absent
(12
Continuous low-level (four patients) Normal(10 patients)’
High (9) Low(1) High
(2)
Low (2)
Note-Numbers in parentheses are number of patients. * Obstruction not quantified: two proximal calculi. t Location not specified: four calculi. Obstruction not quantified:
Ureteral jets may also be seen at realtime gray-scale sonography as a stream of low-strength echoes entering the bladder (1). Intuitively, one would not expect an acoustic interface to be produced between fluids with identical acoustic properties. A number of theories have been proposed to explain why urine flowing into the bladder generates a reflection that can be detected with sonography. Potential sources of reflections include microbubbles or particulate matter in the urine, tempera-
one calculus.
tune differences between ureteral urine and bladder urine, and development of turbulence or cavitation the ureteral orifice (9). The most widely accepted current explanation is that the reflections are generated differences
in density
between
at
by
urine
in the bladder and urine exiting the ureter (9,10). Price et al (10) recently performed extensive experiments in vitro which show that the jet phenomenon occurs only when density differences exist. They have also shown that the intensity of the reflec-
August
1991
lions increases with both increasing density differences and increasing flow rates (10). Regardless of their cause, it is dear that sonographic detection of ureteral jets reflects urine flow from the ureteral orifice. Therefore, it is reasonable to assume that unilateral ureteral obstruction would result in asymmetry of the ureteral jets. To detect this asymmetry, it is important to have a system that is as sensitive as possible for detection of urine flow from the ureteral orifice. Clearly, Doppler techniques are more sensitive to moving, low-level reflectons than conventional gray-scale sonography.
This
is why
Doppler
sig-
nals can be obtained from flowing intravascular blood even when the lumen is completely anechoic. Therefore, it is better to evaluate the ureteraljets with Doppler techniques than with gray-scale imaging. We chose to use color Doppler US rather than conventional duplex sonography for two main reasons. First, color Doppler is sensitive to fluid flow throughout
the
field
of view,
so it is
much less prone to sampling error than range-gated pulsed Doppler. Second, color Doppler allows for simultaneous visualization of the ureteral jets from both ureteral orifices, while duplex Doppler can be used on only one side at a time. Our experience with these patients indicates that the temporal frequency of jets in any subject varies unpredictably after hydration. For instance, ureteral jets were occasionally not detected 15 minutes after hydration but were readily detected 25 minutes after hydration. Therefore, separate duplex Doppler evaluations of each ureteral orifice obtained at different times may differ
because
of temporal
fluctua-
lions in diuresis rather than true asymmetries in urine flow. The results we obtained with color Doppler in healthy adults are similar to those in previous studies of children (3,4). Jets are normally directed in an anteromedial direction but may be oriented differently if the bladder is distorted by intrinsic or extrinsic processes such as prostatic hypertrophy, rectal enlargement, or cystitis. Jequier et al have shown that the frequency of ureteral jets is variable and may range from less than one jet per minute to a continuous flow (3). We have noted similar variations among adult volunteers and believe this almost certainly reflects differences in hydration from subject to subject. However, because both kidneys in a
Volume
180
#{149} Number
2
given patient are subjected to an identical state of hydration, one would expect that the frequency of jets should be bilaterally symmetric in a healthy individual. This appears to be the case both in our group of healthy adults and in children (3). Lack of the normal symmetry between the two ureteral jets made it possible to detect ureteral obstruction in 16 of 26 patients with ureteral stones documented by means of IVU. In 12 patients this asymmetry was manifest as complete nonvisualization of jets from the symptomatic side. This result is easy to understand. In four patients, continuous low-level flow was seen on the symptomatic side. In these four patients, we believe that increased pressure in the obstructed ureter overcame the resistance to flow caused by the ureteral stone and resulted in detection of some urine flow. The continuous nature of this flow presumably reflected ineffective ureteral peristalsis. No relationship existed between the degree of hydronephrosis and the pattern of ureteral jets. Hydronephrosis was mild in nine of the 16 patients with asymmetric ureteraljets. It is well recognized that mild separation of the central echogenic complex at sonography (ie, grade I hydronephrosis) may be due to many entities other than obstruction. These include normal variants, overhydration, diuretic medications, overdistention of the bladder, prominent renal vessels, or the sequelae of previous obstruction or reflux. Therefore, the positive predictive value of grade I hydronephrosis is only 50% (5). Hence, mild separation of the central echogenic complex often requires further evaluation for one to determine its functional significance. Duplex Doppler can help identify which of these patients are most likely to have obstruclion by enabling one to exclude prominent renal vessels as a cause of the separation or to detect elevated arterial resistance (11,12). This study suggests that detection of asymmetric ureteral jets with color Doppler may be another means of identifying patients with mild hydronephrosis who are likely to have obstruction. Although evaluation of ureteral jets may add information to sonographic renal examinations, it is important to recognize the limitations of this technique. As mentioned previously, four subjects were excluded from the study group because of inability to detect ureteral jets from either side. We suspect that jets would have been
detected if time had allowed for more prolonged scanning after hydration or rehydration. However, a busy patient schedule may preclude prolonged studies and make the examination impractical in certain patients. In patients with low-grade obstruclion or nonobstructing stones, the amount of asymmetry in the ureteral jets may fall within the normal range. This occurred in the 10 patients in group III. In addition, this technique may not aid in the sonographic determination of the level and cause of obstruction unless the shadowing calculus can be detected in the ureter. Patients with borderline cardiac function may be unable to tolerate the hydration necessary to perform the examination. Finally, alterations in renal function or renal concentrating ability may alter the detection of ureteral jets with color Doppler in the absence of obstruction. Therefore, we do not recommend that color Doppler be used routinely instead of IVU. Rather, we believe that its use should be adjunclive. As previously mentioned, one potential indication for analysis of areteraljets would be to further evaluate equivocal
hydronephrosis
detected
initially at sonography. In such a case, detection of asymmetry in the ureteraijets would suggest that the hydronephrosis is likely obstructive. Another potential use would be to differentiate high-grade from lowgrade ureteral obstruction in patients with ureteral calculi detected with sonography. Patients with complete absence of detectable jets are much more likely to have high-grade obstruction, whereas patients with normaljets never had high-grade obstruction. Finally, ureteral jets could be studied with color Doppler instead of IVU for suspected renal colic in patients sensitive to contrast media or in those for whom acquisition of multipie radiographs would be undesirable, such as pregnant and pediatric patients. In summary, this study has shown that in patients with ureteral calculi that produce high-grade obstruction, ureteral jets show asymmetry when evaluated with color Doppler. This asymmetry may manifest as either (a) complete absence of detectable ureteral flow from the symptomatic side or (b) continuous low-level flow from the symptomatic side. Patients with nonobstructing stones or stones producing low-grade obstruction may or may not have asymmetry in their ureteraljets. U
Radiology
#{149} 441
5.
References 1.
Dubbins
BB.
PA, Kurtz AB, DarbyJ, Goldberg Uretericjet effect: the echographic
appearance
2.
3.
4.
of urine
the
bladder.
Radiology 1981; 140:513-515. Elejalde BR, Mercedes de Elejalde M. Ureteral ejaculation of urine visualized by ultrasound. J Clin Ultrasound 1983; 11:475476. Jequier S, Paltiel H, Lafortune M. Ureterovesical jets in infants and children: duplex and color Doppler US studies. Radiology 1990; 175:349-353. JL,Johnson ND, De Campo MP. Vesicoureteric reflux in children: prediction with color Doppler imaging. Radiol-
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PH, Scheible
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933-935. Nevin IN, Clime ureteral
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spurt:
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ation. Radiology 12.
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1982; 142:175-177. Price CI, Adler RS, Rubin JM. Ultrasound detection of differences in density: explanation of the ureteric jet phenomenon and implications for new ultrasound applications. Invest Radiol 1989; 24:876-883. Scola FH, Cronan ll Schepps B. Grade I hydronephrosis: pulsed Doppler US evalu-
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1989;
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JM, Ellis JH, DiPietro
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August1991