PATIENTS AND METHODS
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- PATIENTS AND METHODS
Thirty-five children (15 boys, 20 girls, aged 2–15 years, mean 7.1, sd 3; and 6.5, sd 2.7, respectively) underwent DUS and standard VCUG. The rationale and nature of the study were explained to the parents beforehand. All patients underwent DUS and VCUG within 48 h but the findings of VCUG were not reported to the ultrasonographer before the DUS studies. Care was taken to hydrate the patients well at the time of the examination, and recordings obtained when the bladder was moderately full and during micturition.
VCUG was undertaken using a digital screening unit (Philips, Tele Diagnost, the Netherlands). The ultrasound examinations were obtained with a colour Doppler real-time machine (Esaote-Biomedika HU3-Partner, Italy) using a 3.5 MHz convex colour Doppler transducer. The machine settings were wall-filter medium (50) and pulse frequency 2800 Hz. The colour map was red toward the probe and blue away from it. Representative images of jets and of the Doppler detection of VUR were recorded with a multiformat camera and on VHS videotape (Fig. 1a–c).
Conventional US and DUS were carried out by the same ultrasonographer; all patients were examined by conventional US before fluid intake to record pelvicalyceal system dimensions and to provide baseline information about the kidneys (size, shape, parenchymal thickness and scars). All children were then asked to drink water or tea until they had a full-bladder sensation; the patients ingested a large amount of water and/or tea. The lower ends of the ureters were monitored in the transverse and longitudinal planes, and bladder jets from the ureter to bladder, and any reversal of flow from bladder to ureter, noted. At the end of the filling period there was a second conventional US of the kidney to detect possible pelvicalyceal dilatation. The child was then asked to void and again the lower end of the ureter was continuously monitored. The duration of any reflux and its upward extent were difficult to evaluate. The change in pelvicalyceal and/or ureteric echoes, while applying pressure on the bladder and voiding, was also evaluated during the study, to infer high-grade VUR, the diagnosis of which was based on collecting system dilatation, and included both scans at baseline and during the study. High-grade VUR was confirmed by the presence of collecting system dilatation in the ipsilateral kidney and ureter only during the study. If there was a collecting system dilatation on baseline scans, which was especially apparent in patients with grade IV and V reflux, high-grade reflux was inferred by the presence of increased collecting system dilatation in the ipsilateral kidney and ureter during the study compared with baseline findings. The mean (sd, range) of the examination time was 26.1 (5.3, 15–35) min. If patients did not void, DUS of the bladder was repeated on the following day.
Reflux detected on VCUG was graded according to the international classification of VUR . Collecting systems were examined and compared with previous US findings to grade the reflux. The grade of dilation of the pelvis and/or ureter during the study was used to classify high-grade reflux, with the grade on DUS classified according to Salih et al.; grade I, II on VCUG was classified as low-grade on DUS because the reflux occurred with no pelvic dilatation and the kidneys were normal; grade III reflux was associated with mild dilation of the pelvicalyceal system and ureter. Grade IV and V were associated with moderate and massive dilation of pelvis, respectively (Table 1). Also, in the follow-up of patients using DUS, collecting system dilatation was examined by conventional US to grade and compare with previous US findings.
Table 1. Grading of reflux on DUS
|I||Partial filling of an undilated ureter||Low-grade reflux|
|II||Total filling of an undilated ureter||Reflux (+ve) and lower ureteric filling only; US shows no pelvicalyceal system dilation|
|III||Dilated calyces but sharp fornices||Reflux (+ve), mild dilation of ureter and pelvis on US|
|IV||Blunted fornices and degree of dilation greater than in lower stages||Reflux (+ve) with moderate dilation of pelvis on US|
|V||Massive hydronephrosis and tortuosity of ureters ||Reflux (+ve) with massive dilation of pelvis and ureter on US|
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- PATIENTS AND METHODS
Because the procedure requires compliance from the patients, the study included only patients aged ≥ 2 years. Differentiation of the colour jets from vascular structures nearby was ensured by combining pulsed Doppler and colour flow DUS. The comparison of VCUG and DUS in 35 patients is shown in Table 2; 29 ureters were refluxing on VCUG (bilateral in seven patients and unilateral in 15) with the distribution of grade as shown in Table 2. On simultaneous DUS there were 28 refluxing ureters; DUS clearly showed reflux in most of the patients (Fig. 1a-c). There were two positive results on DUS where the VCUG was normal and three false-negative findings on DUS. The sensitivity and specificity of DUS were 90% and 93%, respectively.
Table 2. Comparison of VCUG and DUS in 35 patients
|Grade||VCUG, n||DUS grade (n)|
|I||8||Low grade (6)|
|II||7||Low grade (6)|
|III||5||Mild pelvicalyceal changes (5)|
|IV||5||Moderate pelvicalyceal changes (5)|
|V||4||Severe pelvicalyceal changes (4)|
The lower ureter appeared to be dilating at the bladder base, together with the appearance of a blue DUS signal within the lumen in the presence of reflux. The ureteric lumen was wider and retrograde urine flow was slower in the patients with high-grade than in those with low-grade reflux (Fig. 1a-c).
Four patients with high-grade reflux underwent antireflux surgery during the course of their treatment, with DUS used to follow them for 3 months; both diagnostic methods showed no reflux (Fig. 1d,e).
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- PATIENTS AND METHODS
Various studies have reported success rates for diagnosing VUR by conventional US and DUS techniques. Schneider et al. reported total accuracy for grades III and IV, and 84% for grade II reflux when real-time US was used as a diagnostic method. Hanbury et al. reported total sensitivity in detecting grades III and IV, but 60% for grade II and 25% for grade I reflux. All US findings are based on visualizing structural and anatomical changes in the urinary tract. Although these methods give adequate results for detecting grade ≥ III reflux, they are ineffective for the lower grades. Later, DUS was used as an adjunct to standard US, to improve the results [6,9,10]. Oak et al. reported 87% accuracy for grade I, 92% for grade II and 100% for grades III, IV and V reflux using a colour Doppler real-time machine as a diagnostic method. Salih et al. reported 90%, 100% and 75% accuracy in low-grade, grade III and grade IV reflux, respectively. Others have reported that detecting reflux is greatly influenced by the hydration status and compliance of the patient, and the duration of the screening. All the present patients were asked to drink fluid before the procedure. Others have noted that the procedure requires compliance by the patients and hence is unsuitable for the patients aged < 2 years; the present study included only patients aged> 2 years and there were no compliance problems. However, four children did not void while supine and the procedure was repeated on the following day. False-positive findings of reflux have been reported as 5.5% by Oak et al. and Haberlik  reported higher values (18.5%), although the latter study included only patients with low-grade reflux. In the present study there were two false-positive results, probably because these patients had intermittent reflux. There is evidence from radionuclide cystography to suggest that reflux occurs even in children with a negative result on VCUG . Cyclic VCUG increases the detection of VUR and bladder fluctuation caused by manipulation during the procedure can form a colour artefact at the back of the bladder in some patients, which can be evaluated incorrectly as reflux. Oak et al. reported false-negative results in 8.3% of their patients; there were three in the present series, which might have been caused by reflux that was too slow to detect, by intermittent reflux, or by poor hydration and low patient compliance.
Some authors reported that DUS correlated well with the results of VCUG during the follow-up of patients who had undergone ureteric reimplantation [6,9], but the series were small. We also evaluated four patients with DUS 3 months after surgery and the results correlated well with those from VCUG. Further studies with more patients after antireflux surgery should increase knowledge about the role of DUS as a screening method after managing VUR.
DUS has some advantages and limitations; a major advantage is the absence of ionizing radiation, so that the examination can be repeated several times if necessary. Catheterization is avoided, as is injection with contrast medium. The parenchyma of the kidneys can also be evaluated for scarring by combining conventional US and DUS at the same session. An important limitation of DUS is that imaging of the posterior urethra is not as good as it is with VCUG, which imposes restrictions on the initial evaluation of PUV in boys. Reflux occurring in the filling phase may also not be as clear as with VCUG. The anatomical delineation of dilation, kinks and tortuosity of a ureter are also better seen with VCUG; this imposes restrictions on the grading of the reflux.
Detecting the presence of collecting system dilation in patients with high-grade VUR during the follow-up was ensured by combining conventional US with DUS at the same session. Also, measuring the lower ureteric lumen diameter at the bladder base and reversal of flow velocity to the ureter with DUS can help to grade and follow-up reflux. The ureteric diameter was greater and retrograde urine flow velocity slower in patients with high-grade than in those with low-grade reflux (Fig. 1a-c), but these initial results need further confirmation in a larger series.
Our diagnostic protocol for VUR was revised on the basis of these results; DUS is used in the follow-up of patients with a VCUG diagnosis of VUR, and VCUG is therefore only used in cases negative on US, to confirm resolution of the reflux. This allows the dose of radiation to be reduced significantly, which is important in young patients requiring several assessments during the follow-up; thus we have accepted DUS as probable technique for the future.
In conclusion, the present results accord with those from other studies on the role of DUS in diagnosing VUR. Further studies with more patients are required to evaluate the role of DUS in the follow-up of patients after antireflux surgery, the relationship between ureteric diameter at the base of the bladder, reversal of flow to the ureter and the grade of reflux.