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Doppler ultrasound in pelviureteric junction obstruction in infants and children
Doppler Ultrasound in Pelviureteric Junction in Infants and Children ByW. Kincaid,
AS. Hollman, Glasgow,
0 Six infants and seven children with known pelviureteric junction (PUJ) obstruction (11 unilateral, 2 bilateral) were assessed with Doppler ultrasound
kidneys.
No such change was detected
in the
normal kidneys. Five patients were reassessed after pyeloplasty. The Doppler indexes facilitated prediction of those cases with a satisfactory outcome after surgery. Doppler ultrasound with diuresis is useful in the assessment of PUJ obstruction in infants and children and in the postoperative follow-up. Copyri9ht
0 1994 by W.6. Saunders Compeny
INDEX WORDS: obstruction,
Doppler
and A.F.A. Azmy
Scotland
Doppler ultrasound in infants and children with PUJ obstruction.
before and after diuresis.
After intravenous frusemide, there was a significant increase in the resistance index in the interlobar renal arteries of the obstructed
Obstruction
ultrasound;
pelviureteric
junction
paediatric.
G dilated, obstructed
RAY -SCALE ultrasound cannot differentiate a renal collecting system from a similarly dilated but nonobstructed one. Some form of invasive imaging is usually required to make this distinction, and a technetium 99m diethylene triamine pentaacetic acid (DTPA) study along with a diuretic has become the imaging method of choice for diagnosing and quantifying the degree of obstruction. If an obstructed system is confirmed, an intravenous urogram may provide additional anatomic information for surgical planning. Several investigators1-4 have shown that duplex Doppler sonography may distinguish a nonobstructed kidney from an obstructed one because the renal arterial resistance is higher than normal in the latter. The resistance index (RI) (peak systole minus end diastole, divided by peak systole), calculated from the Doppler waveforms, is higher in the intrarenal arteries on the affected side because the diastolic flow rate is lower, particularly when the obstruction is acute. These effects are reversed if the obstruction is relieved. However, not all patients with obstruction have higher RI values in the obstructed side, particularly if the obstruction is chronic.5 In 1992, Renowden and Cochlin6 reported the use of diuresis Doppler sonography in two adult patients. The RI values of the obstructed and normal kidneys were normal; however, after intravenous frusemide, there was a significant increase in dilatation of the pelvicalyceal system and an increase in the RI on the obstructed side, but no such change was observed on the normal side. Herein we report the results of using diuresis Journal of Pediatric Surgery, Vol29, No 6 (June), 1994: pp 765-768
MATERIALS
AND METHODS
Thirteen infants and children with proven PUJ obstruction underwent color Doppler ultrasound within 24 hours before pyeloplasty. Full parental consent was obtained. The examinations were performed with the child in the prone position, using an Acuson 128 XPlO system (Mountain View, CA) with a ~-MHZ sector or curved linear transducer, or a 73MHz sector or linear transducer. The renal cortex was assessed subjectively as normal, reduced in thickness, or markedly thinned, and the degree of pelvicalyceal dilatation was assessed as none, minimal, moderate, or gross. Pulsed Doppler measurements were recorded from interlobar renal arteries at the upper pole, lower pole, and the mid aspect of each kidney. A minimum of three consecutive waveforms were recorded on video for each artery. The measurements were repeated 10 minutes after intravenous frusemide (1 mg/kg to a maximum of 20 mg). The RI for each kidney was calculated as an average value obtained from the waveforms. In five patients the Doppler study was repeated 1 week postpyeloplasty, within 8 hours of a nephrostogram. Before this examination the nephrostomy tube was clamped and the study performed as described above. The radiologist performing the ultrasound examination was unaware of the nephrostogram findings. RESULTS
There were seven girls and six boys in the study group (age range, 0.1 to 10.7 years; mean, 3.2 years). Table 1 shows the cortical width and the change in pelvicalyceal dilatation after frusemide. The PUJ obstruction was unilateral in 11 cases (7 right kidney, 4 left kidney) and bilateral in two (both males, aged 6.8 and 0.2 years). Figure 1 shows the RIs of kidneys with PUJ obstruction (Fig 1A) and normal kidneys (Fig 1B) before and after frusemide. The Doppler measurements before and after frusemide in the five patients examined postoperatively are shown in Fig 2. Figure 2A shows the significant increase in RIs of the kidneys that had no drainage of contrast on the nephrostogram; Fig 2B shows no From the Departments of Diagnostic Radiology and Surgery. The Royal Hospital for Sick Children. Glasgow, Scotland. Presented at the 40th Annual International Congress of the British Association of Paediattic Surgeons, Manchester, England, .I@ 21-23, 1993. Address reprint requests to A.S. Hollman. MD, Department of Diagnostic Radiology, The Royal Hospital for Sick Children. Yorkhill, Glasgow G3 8SJ. Scotland. Copyright o 1994 by U?B. Saunders Company 0022-3468/9412906-0013$03.OOJO 765
766
KINCAID, HOLLMAN, AND AZMY
RI
Table 1. Cortical Width and Change in Degree of Peivicalyceal Dilatation After Frusemide PelvicalycealDilatation CorticalWidth Patient No.
Side of PUJ
PUJ
With Frusemide
Normal Side
PUJ
Normal Side
0.9 -
Marked 1
thinning
Bilateral
0.8 -
Reduced
0.7 -
Right
Normal
Normal
Right
Normal
Normal
None
0.6 -.
Left
Normal
Normal
None
0.5 -
Right
Reduced
Normal
None
None
Left
Reduced
Normal
None
Right
Normal
Normal
None
Left
Normal
Normal
None
Right
Normal
Normal
None
”
0.4 -
;
Marked 10
Right
11
Right
12
Left
thinning
Normal
None
Normal
Normal
None
Normal
Normal
None
Patient
No.
Patient
No.
Reduced
13
Reduced NOTE. Arrows indicate increased dilatation after frusemide.
significant change in the RIs of the kidneys that had free drainage of contrast down the ureter.
0.8
1
DISCUSSION
It has been well documented1-3,5 that in acute renal obstruction in adults an increase in vascular resistance occurs within the kidney, which can be detected by Doppler ultrasonography, ie, a significant increase ( > 0.1) in the calculated RI. In chronic obstruction there is a compensatory reduction in renal function to reach a steady state, and no change in the Doppler study can be detected. This is confirmed by our study; no significant difference in RI was detected between the obstructed and nonobstructed kidneys in the resting state. In an obstructed kidney that has an adequate renal cortex and that continues to function, the increased urine production leads to an increase in collecting system pressure and parenchymal pressure, which is reflected as an increase in vascular resistance
A
l
l
2
3
4
5
3
7
Patient
5
No.
9
IO
11
12
13
13
Fig 2. Ris before (E2) and after (U) diuresis in five patients following pyeiopiasty. (A) There is a significant increase in the RI, suggesting continuing obstruction and cormiating with no drainage on the nephrostogram. (B) There is no significant increase in the RI with diuresis; this correlates with the nephrostogram result of free drainage of contrast into the ureter.
s
7
Patient
9
io
11
12
No.
Fig 1. Change in RI before (I#) and after (w) intravenous frusemide. The RI is significantly higher in the obstructed control kidneys (B).
kidneys (A) than in the
DOPPLER ULTRASOUND
IN PUJ OBSTRUCTION
767
of 1.0 (Fig 4). In each of the 11 cases, a noticeable increase in pelvicalyceal dilatation occurred after diuresis. When assessing renal obstruction with Doppler ultrasound, other factors must be considered. In children, cortical width is difficult to assess accurately with ultrasound; we simply graded it as normal, reduced, or markedly thinned. If there is very marked cortical thinning and very poor renal function, then the ability of a kidney to respond to a diuretic is significantly reduced and, therefore, no significant change in RI is detected. This is believed to explain two of the cases (nos. 1 and 10) in which there was little change in RI postdiuresis. In one child with bilateral PUJ obstruction, the divided renal function was right kidney 3%, left kidney 97%. No significant change in RI was noted in the poorly functioning right kidney after intravenous frusemide, and the child underwent a right nephrectomy and a left pyeloplasty. In the other case, there was marked reduction in cortical thickness, suggesting poor renal function. The detected RI difference after diuresis in another obstructed kidney was 0.08 (no. 9). This is not a significant increase and may reflect a mild degree of
Fig 3. Doppler waveform before (A; RI = 0.62) and after fruwmida (6; RI = 0.79). Gray scale shows the increase in pelvicalyceal dilatation postdiuresis in PUJ obstruction.
and in the observed RI. Intravenous frusemide does not alter the RI of normal nonobstructed kidneys,’ as found in the contralateral kidneys (which acted as controls) in 11 of our patients. The normal range of Doppler indexes in adult kidneys has been well established. An RI of less than 0.7 is normal, and the measured difference in RI between the left and right kidneys should not be greater than 0.1. A value greater than 0.7 is considered consistent with obstruction, although there is some overlap for patients with partial obstruction.l There are notable differences in normal renal RI values in paediatric practice. The RI is age-dependent; it is commonly high before the age of 1 year and decreases with age. x,y The difference detected between left and right remains at 0.1 or less. This explains the “high” resting RIs detected in three patients. After diuresis, a significant increase (>O.l) in RI was detected in 11 of the 15 kidneys with known PUJ obstruction (Fig 3). This includes the kidneys with a high resting RI. In one infant with an RI of 0.85, end diastolic flow was absent after diuresis, giving an RI
Fig 4. Doppler waveform of an infant shows [A) a high resting RI (0.85) and (El) loss of diastolic flow after diuresis in the obstructed kidney (RI = 1.0).
768
KINCAID, HOLLMAN,
obstruction that cannot be differentiated from the interobserver and intraobserver variation inherent in the technique. The fourth case (no. 2) with a minimal change in RI occurred early in the study, and our only possible explanation is that the Doppler study was repeated too soon after frusemide administration. After pyeloplasty, as might be expected, there was no significant change in RI following frusemide in the patients whose kidneys showed free drainage on the nephrostogram. In those with continuing obstruction, an increase in RI was noted after the frusemide.
AND AZMY
These results correlated well with those of a nephrostogram performed on the same day. In each case with continuing obstruction, this was confirmed at a later date by a repeat DTPA study. At present we consider Doppler examination useful in confirming PUJ obstruction, and it may have an initial role in departments with no nuclear medicine service. It is also a potentially valuable technique in assessing the result of pyeloplasty. The greatest potential in paediatrics will lie in differentiating dilated obstructed systems from nonobstructed systems.
REFERENCES 1. Platt JF, Rubin JM, Ellis JH, et al: Duplex Doppler US of the kidney: Differentiation of obstructive from non-obstructive dilatation. Radiology 171:515-517, 1989 2. Platt JF: Duplex Doppler evaluation of native kidney dysfunction: Obstructive and nonobstructive disease. AJR 158:1035-1042, 1992 3. Platt JF, Rubin JM, Ellis JH: Acute renal obstruction: Evaluation with intrarenal duplex Doppler and conventional US. Radiology 186:685-688,1993 4. Patriquin H: Doppler examination of the kidney in infants and children. Ural Radio1 12:220-227,199l 5. Dubbins PA: Duplex ultrasound of the renal tract. BMUS Bulletin, May 1991, pp 12-15
6. Renowden SA, Cochlin DL: The potential use of diuresis Doppler sonography in PUJ obstruction. Clin Radio1 46:94-96, 1992 7. Renowden SA, Cochlin DL: The effect of intravenous frusemide on the Doppler waveform in normal kidneys. J Ultrasound Med 11:65-68, 1992 8. Kincaid W, Hoilman AS: Renal Doppler ultrasound normal infants and children. Br J Radio1 66:121, 1993
in
9. Bude RO, DiPietro MA, Platt JF, et al: Age dependency of the renal resistive index in healthy children. Radiology 184:469473, 1992
AS. Hollman, Glasgow,
0 Six infants and seven children with known pelviureteric junction (PUJ) obstruction (11 unilateral, 2 bilateral) were assessed with Doppler ultrasound
kidneys.
No such change was detected
in the
normal kidneys. Five patients were reassessed after pyeloplasty. The Doppler indexes facilitated prediction of those cases with a satisfactory outcome after surgery. Doppler ultrasound with diuresis is useful in the assessment of PUJ obstruction in infants and children and in the postoperative follow-up. Copyri9ht
0 1994 by W.6. Saunders Compeny
INDEX WORDS: obstruction,
Doppler
and A.F.A. Azmy
Scotland
Doppler ultrasound in infants and children with PUJ obstruction.
before and after diuresis.
After intravenous frusemide, there was a significant increase in the resistance index in the interlobar renal arteries of the obstructed
Obstruction
ultrasound;
pelviureteric
junction
paediatric.
G dilated, obstructed
RAY -SCALE ultrasound cannot differentiate a renal collecting system from a similarly dilated but nonobstructed one. Some form of invasive imaging is usually required to make this distinction, and a technetium 99m diethylene triamine pentaacetic acid (DTPA) study along with a diuretic has become the imaging method of choice for diagnosing and quantifying the degree of obstruction. If an obstructed system is confirmed, an intravenous urogram may provide additional anatomic information for surgical planning. Several investigators1-4 have shown that duplex Doppler sonography may distinguish a nonobstructed kidney from an obstructed one because the renal arterial resistance is higher than normal in the latter. The resistance index (RI) (peak systole minus end diastole, divided by peak systole), calculated from the Doppler waveforms, is higher in the intrarenal arteries on the affected side because the diastolic flow rate is lower, particularly when the obstruction is acute. These effects are reversed if the obstruction is relieved. However, not all patients with obstruction have higher RI values in the obstructed side, particularly if the obstruction is chronic.5 In 1992, Renowden and Cochlin6 reported the use of diuresis Doppler sonography in two adult patients. The RI values of the obstructed and normal kidneys were normal; however, after intravenous frusemide, there was a significant increase in dilatation of the pelvicalyceal system and an increase in the RI on the obstructed side, but no such change was observed on the normal side. Herein we report the results of using diuresis Journal of Pediatric Surgery, Vol29, No 6 (June), 1994: pp 765-768
MATERIALS
AND METHODS
Thirteen infants and children with proven PUJ obstruction underwent color Doppler ultrasound within 24 hours before pyeloplasty. Full parental consent was obtained. The examinations were performed with the child in the prone position, using an Acuson 128 XPlO system (Mountain View, CA) with a ~-MHZ sector or curved linear transducer, or a 73MHz sector or linear transducer. The renal cortex was assessed subjectively as normal, reduced in thickness, or markedly thinned, and the degree of pelvicalyceal dilatation was assessed as none, minimal, moderate, or gross. Pulsed Doppler measurements were recorded from interlobar renal arteries at the upper pole, lower pole, and the mid aspect of each kidney. A minimum of three consecutive waveforms were recorded on video for each artery. The measurements were repeated 10 minutes after intravenous frusemide (1 mg/kg to a maximum of 20 mg). The RI for each kidney was calculated as an average value obtained from the waveforms. In five patients the Doppler study was repeated 1 week postpyeloplasty, within 8 hours of a nephrostogram. Before this examination the nephrostomy tube was clamped and the study performed as described above. The radiologist performing the ultrasound examination was unaware of the nephrostogram findings. RESULTS
There were seven girls and six boys in the study group (age range, 0.1 to 10.7 years; mean, 3.2 years). Table 1 shows the cortical width and the change in pelvicalyceal dilatation after frusemide. The PUJ obstruction was unilateral in 11 cases (7 right kidney, 4 left kidney) and bilateral in two (both males, aged 6.8 and 0.2 years). Figure 1 shows the RIs of kidneys with PUJ obstruction (Fig 1A) and normal kidneys (Fig 1B) before and after frusemide. The Doppler measurements before and after frusemide in the five patients examined postoperatively are shown in Fig 2. Figure 2A shows the significant increase in RIs of the kidneys that had no drainage of contrast on the nephrostogram; Fig 2B shows no From the Departments of Diagnostic Radiology and Surgery. The Royal Hospital for Sick Children. Glasgow, Scotland. Presented at the 40th Annual International Congress of the British Association of Paediattic Surgeons, Manchester, England, .I@ 21-23, 1993. Address reprint requests to A.S. Hollman. MD, Department of Diagnostic Radiology, The Royal Hospital for Sick Children. Yorkhill, Glasgow G3 8SJ. Scotland. Copyright o 1994 by U?B. Saunders Company 0022-3468/9412906-0013$03.OOJO 765
766
KINCAID, HOLLMAN, AND AZMY
RI
Table 1. Cortical Width and Change in Degree of Peivicalyceal Dilatation After Frusemide PelvicalycealDilatation CorticalWidth Patient No.
Side of PUJ
PUJ
With Frusemide
Normal Side
PUJ
Normal Side
0.9 -
Marked 1
thinning
Bilateral
0.8 -
Reduced
0.7 -
Right
Normal
Normal
Right
Normal
Normal
None
0.6 -.
Left
Normal
Normal
None
0.5 -
Right
Reduced
Normal
None
None
Left
Reduced
Normal
None
Right
Normal
Normal
None
Left
Normal
Normal
None
Right
Normal
Normal
None
”
0.4 -
;
Marked 10
Right
11
Right
12
Left
thinning
Normal
None
Normal
Normal
None
Normal
Normal
None
Patient
No.
Patient
No.
Reduced
13
Reduced NOTE. Arrows indicate increased dilatation after frusemide.
significant change in the RIs of the kidneys that had free drainage of contrast down the ureter.
0.8
1
DISCUSSION
It has been well documented1-3,5 that in acute renal obstruction in adults an increase in vascular resistance occurs within the kidney, which can be detected by Doppler ultrasonography, ie, a significant increase ( > 0.1) in the calculated RI. In chronic obstruction there is a compensatory reduction in renal function to reach a steady state, and no change in the Doppler study can be detected. This is confirmed by our study; no significant difference in RI was detected between the obstructed and nonobstructed kidneys in the resting state. In an obstructed kidney that has an adequate renal cortex and that continues to function, the increased urine production leads to an increase in collecting system pressure and parenchymal pressure, which is reflected as an increase in vascular resistance
A
l
l
2
3
4
5
3
7
Patient
5
No.
9
IO
11
12
13
13
Fig 2. Ris before (E2) and after (U) diuresis in five patients following pyeiopiasty. (A) There is a significant increase in the RI, suggesting continuing obstruction and cormiating with no drainage on the nephrostogram. (B) There is no significant increase in the RI with diuresis; this correlates with the nephrostogram result of free drainage of contrast into the ureter.
s
7
Patient
9
io
11
12
No.
Fig 1. Change in RI before (I#) and after (w) intravenous frusemide. The RI is significantly higher in the obstructed control kidneys (B).
kidneys (A) than in the
DOPPLER ULTRASOUND
IN PUJ OBSTRUCTION
767
of 1.0 (Fig 4). In each of the 11 cases, a noticeable increase in pelvicalyceal dilatation occurred after diuresis. When assessing renal obstruction with Doppler ultrasound, other factors must be considered. In children, cortical width is difficult to assess accurately with ultrasound; we simply graded it as normal, reduced, or markedly thinned. If there is very marked cortical thinning and very poor renal function, then the ability of a kidney to respond to a diuretic is significantly reduced and, therefore, no significant change in RI is detected. This is believed to explain two of the cases (nos. 1 and 10) in which there was little change in RI postdiuresis. In one child with bilateral PUJ obstruction, the divided renal function was right kidney 3%, left kidney 97%. No significant change in RI was noted in the poorly functioning right kidney after intravenous frusemide, and the child underwent a right nephrectomy and a left pyeloplasty. In the other case, there was marked reduction in cortical thickness, suggesting poor renal function. The detected RI difference after diuresis in another obstructed kidney was 0.08 (no. 9). This is not a significant increase and may reflect a mild degree of
Fig 3. Doppler waveform before (A; RI = 0.62) and after fruwmida (6; RI = 0.79). Gray scale shows the increase in pelvicalyceal dilatation postdiuresis in PUJ obstruction.
and in the observed RI. Intravenous frusemide does not alter the RI of normal nonobstructed kidneys,’ as found in the contralateral kidneys (which acted as controls) in 11 of our patients. The normal range of Doppler indexes in adult kidneys has been well established. An RI of less than 0.7 is normal, and the measured difference in RI between the left and right kidneys should not be greater than 0.1. A value greater than 0.7 is considered consistent with obstruction, although there is some overlap for patients with partial obstruction.l There are notable differences in normal renal RI values in paediatric practice. The RI is age-dependent; it is commonly high before the age of 1 year and decreases with age. x,y The difference detected between left and right remains at 0.1 or less. This explains the “high” resting RIs detected in three patients. After diuresis, a significant increase (>O.l) in RI was detected in 11 of the 15 kidneys with known PUJ obstruction (Fig 3). This includes the kidneys with a high resting RI. In one infant with an RI of 0.85, end diastolic flow was absent after diuresis, giving an RI
Fig 4. Doppler waveform of an infant shows [A) a high resting RI (0.85) and (El) loss of diastolic flow after diuresis in the obstructed kidney (RI = 1.0).
768
KINCAID, HOLLMAN,
obstruction that cannot be differentiated from the interobserver and intraobserver variation inherent in the technique. The fourth case (no. 2) with a minimal change in RI occurred early in the study, and our only possible explanation is that the Doppler study was repeated too soon after frusemide administration. After pyeloplasty, as might be expected, there was no significant change in RI following frusemide in the patients whose kidneys showed free drainage on the nephrostogram. In those with continuing obstruction, an increase in RI was noted after the frusemide.
AND AZMY
These results correlated well with those of a nephrostogram performed on the same day. In each case with continuing obstruction, this was confirmed at a later date by a repeat DTPA study. At present we consider Doppler examination useful in confirming PUJ obstruction, and it may have an initial role in departments with no nuclear medicine service. It is also a potentially valuable technique in assessing the result of pyeloplasty. The greatest potential in paediatrics will lie in differentiating dilated obstructed systems from nonobstructed systems.
REFERENCES 1. Platt JF, Rubin JM, Ellis JH, et al: Duplex Doppler US of the kidney: Differentiation of obstructive from non-obstructive dilatation. Radiology 171:515-517, 1989 2. Platt JF: Duplex Doppler evaluation of native kidney dysfunction: Obstructive and nonobstructive disease. AJR 158:1035-1042, 1992 3. Platt JF, Rubin JM, Ellis JH: Acute renal obstruction: Evaluation with intrarenal duplex Doppler and conventional US. Radiology 186:685-688,1993 4. Patriquin H: Doppler examination of the kidney in infants and children. Ural Radio1 12:220-227,199l 5. Dubbins PA: Duplex ultrasound of the renal tract. BMUS Bulletin, May 1991, pp 12-15
6. Renowden SA, Cochlin DL: The potential use of diuresis Doppler sonography in PUJ obstruction. Clin Radio1 46:94-96, 1992 7. Renowden SA, Cochlin DL: The effect of intravenous frusemide on the Doppler waveform in normal kidneys. J Ultrasound Med 11:65-68, 1992 8. Kincaid W, Hoilman AS: Renal Doppler ultrasound normal infants and children. Br J Radio1 66:121, 1993
in
9. Bude RO, DiPietro MA, Platt JF, et al: Age dependency of the renal resistive index in healthy children. Radiology 184:469473, 1992