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Can ultrasound reliably detect renal scarring in children with urinary tract infection?
ClinicalRadiology(1993) 47, 177 179
Can Ultrasound Reliably Detect Renal Scarring in Children With Urinary Tract Infection? A. D. TASKER, D. R. M. L I N D S E L L and M. M O N C R I E F F *
Departments of Radiology and *Paediatrics, John Radcliffe Hospital, Oxford One hundred children with a proven urinary tract infection were studied prospectively using both ultrasound (US) and 99mTc dimercaptosuccinic acid (DMSA) scintigraphy to assess the efficacy of U S in the detection of renal scarring. Sixty-nine girls and 31 boys with an age range of 0.5-11.8 years were studied. D M S A scintigraphy detected 19 scarred kidneys in 17 children. Scarring was classified as mild, moderate or gross. U S detected a total of seven of the scarred kidneys (sensitivity 37%). US detected 0/6 kidneys with mild scarring, 1/7 kidneys with moderate scarring and 6/6 kidneys with gross scarring. Four kidneys with scarring on D M S A showed abnormalities other than scarring on US. 8/19 scarred kidneys were thought to be normal on US. It is important to detect renal scarring in young children and US cannot be relied upon for this purpose. It should therefore be supplemented with D M S A scintigraphy. Tasker, A.D., Lindsell, D.R.M. & Moncrieff, M. (1993). Clinical Radiology 47, 177-179. Can Ultrasound Reliably Detect Renal Scarfing in Children With Urinary Tract Infection?
Accepted for Publication 2 October 1992
Reflux nephropathy is a major cause o f renal failure and hypertension in children and adults. Eight percent of patients with reflux nephropathy and renal scarfing will develop hypertension [1] and in 5-6% of patients with end stage renal failure the cause will be reflux nephropathy [2]. It may be possible to prevent these complications if the scarring is detected early. Renal scarring can be demonstrated on intravenous urography (IVU), ultrasound (US) and technetium 99m dimercaptosuccinic acid (DMSA) scintigraphy. DMSA scintigraphy has been shown to be more sensitive than IVU in the detection of renal scars [3], but there are relatively few studies comparing DMSA scintigraphy and US. This study compares directly the ability of DMSA scintigraphy and US to detect scarring. PATIENTS AND M E T H O D S One hundred unselected children referred to a paediatric outpatient department with a proven urinary tract infection (UTI) were examined prospectively by US and DMSA scintigraphy. The investigations were performed on the same day whenever possible. The age range was 0.5-11.8 years. There were 69 girls with a mean age of 4.7 years and 31 boys with a mean age of 4.6 years. DMSA scintigraphy was performed at least 2 months after the UTI. The dose was calculated by correcting for surface area from the standard adult dose of 50 MBq of Tc 99m DMSA. Three hours later images were obtained in the posterior and both posterior-oblique projections using an IGE 400T maxicamera. Differential renal function was provided by computer analysis. The images were reviewed by two radiologists. Renal size and the size, number and position of any photon deficient areas, persisting at least 2 months after the UTI, were assessed. Scarring on DMSA scans was classified into three groups: Correspondenceto: Dr D. R. M. Lindsell,Department of Radiology, John RadcliffeHospital,HeadleyWay,Headington,OxfordOX39DU.
(1) Minor - a single, small peripheral defect in the renal outline (Fig. la). (2) Moderate - two or three defects in the renal outline with no reduction in renal size and normal differential function (Fig. lb). (3) Gross - m o r e than three defects in the renal outline and/or a reduction in renal size and split renal function falling outside the normal range of 45-55% (Fig. lc). The ultrasound scans were all performed by a consultant radiologist with an interest in US using an Acuson 128 machine with a 5 or 3.5 MHz sector transducer. The patient was scanned in the supine, supine-oblique and prone positions. A note was made of renal size, scarring (Fig. 2), pelvicalyceal dilatation or other evidence of reflux nephropathy, such as ureteric dilatation. The bladder was also assessed. RESULTS The examinations were normal in 74/100 children (52 girls and 22 boys). Seventeen children had 19 scarred kidneys on DMSA scintigraphy. The mean age of children with renal scarring was 4.2 years (0.5-8.4 years). 12/69 girls (17.4%) and 5/31 boys (16.1%) had scarred kidneys. Of the 12 girls with scarring five had gross scarring, five had moderate scarring and two had mild scarring. One of the five boys had gross scarring and four had mild scarring. The DMSA results were taken as a gold standard and were compared with the US findings (Fig. 3). US detected 7/19 kidneys which had been demonstrated to have scars on DMSA (sensitivity 37%). US detected 0/6 kidneys with mild scarfing, 1/7 kidneys with moderate scarring and 6/6 kidneys with gross scarring. In four of the scarred kidneys where US failed to demonstrate scarring it showed dilatation of the pelvicalyceal system suggesting vesicoureteric reflux. These children were therefore inves-
178
CLINICAL RADIOLOGY
Fig. 2 - US examination of a grossly scarred and shrunken kidney.
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(a)
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6
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Mild
(b)
Moderate
Gross
Degree of scarring on DMSA St0dy Findings at US
9
Normal
[] ]
Scarring Other eg pelvicalyceal dilatation
Fig. 3 Correlation of scarring on D M S A scintigraphy with US findings.
Table 1 - Number of UTIs per child with renal scarring
(c) Fig. 1 - D M S A scintigraphy demonstrating 'minor' scarring (a), 'moderate' scarring (b) and 'gross' scarring (c).
tigated further with a micturating cystourethrogram and the presence of reflex was confirmed. However, 8/19 (42%) scarred kidneys were thought to be completely normal when assessed by ultrasound. In seven children with normal DMSA scintigraphy the US was thought to be abnormal. Five patients showed
Scarring
Range
Mean
Mild Moderate Gross
1-3 1 1-5
1.5 1.0 3.5
dilatation of the renal collecting system on US and in three of these cases micturating cystourethrography (MCU) demonstrated reflux. Two patients had findings suggesting mild scarring on ultrasound but a normal DMSA study. These were considered to be 'false positive' US diagnoses o f scarring. The number o f urinary tract infections was documented for each child at the time of the scans. Table 1 shows the number o f UTIs that each child with renal scarring had had at the time of presentation.
RENAL SCARRING IN URINARY TRACT INFECTION DISCUSSION U T I in c h i l d h o o d is c o m m o n , affecting 3% o f girls a n d 1% o f b o y s [4]. R e n a l d a m a g e occurs d u e to p y e l o t u b u l a r backflow o f infected urine a n d 10-28% o f these will develop cortical s c a r r i n g [4,5]. It is i m p o r t a n t therefore to detect vesicoureteric reflux a n d renal scarring early, especially in the y o u n g e r age g r o u p w h o are m o s t susceptible to scarring. It has been widely suggested t h a t U S should be the initial investigation o f U T I [6,7]. T h e n o n i n v a s i v e n a t u r e o f US, its lack o f ionizing r a d i a t i o n a n d the ease with which investigations can be r e p e a t e d are a d v a n t a g e s . U S has been s h o w n to be an excellent m e t h o d for detecting structural a b n o r m a l i t i e s o f the u r i n a r y tract such as h y d r o n e p h r o s i s , ureteric d i l a t a t i o n a n d b l a d d e r lesions. It is, however, o p e r a t o r - d e p e n d e n t . This s t u d y clearly shows it to be m u c h less sensitive in the detection o f mild and m o d e r a t e scarring t h a n D M S A scintigraphy. This accords with the w o r k o f K a n g a r l o o e t al. who also f o u n d that u l t r a s o u n d was p o o r at detecting small focal renal defects [8]. Studies c o m p a r i n g I V U a n d D M S A have s h o w n that I V U is less sensitive in the detection o f renal scars [5,9]. M e r r i c k studied 79 children a n d f o u n d a sensitivity o f 60% a n d a specificity o f 92% for I V U c o m p a r e d to a sensitivity o f 96% a n d a specificity o f 98% for scintigraphy [10]. It has also been shown t h a t scars m a y take u p to 2 years to b e c o m e evident on I V U [11]. M o s t studies have s h o w n D M S A s c i n t i g r a p h y to be the most sensitive m e t h o d o f detecting scarring [8,9,12]. Occasional conflicting studies have been published. Smellie studied 52 children in w h o m D M S A failed to detect 6/72 scars seen o n I V U a n d u n d e r - e s t i m a t e d a n o t h e r 13 [ 13]. W h e n e v a l u a t i n g D M S A s c i n t i g r a p h y the timing o f a n y preceding U T I m u s t be t a k e n into consideration in o r d e r to differentiate p o t e n t i a l l y reversible defects in i s o t o p e u p t a k e f r o m those which are p e r m a n e n t [14,15]. V e r b e r a n d Meller d e m o n s t r a t e d t h a t in 49 kidneys with defects seen on the initial scan, only 39 (80%) r e m a i n e d at a m e a n o f 2.25 years [12]. F o r this reason the D M S A s c i n t i g r a p h y in o u r s t u d y was d e l a y e d for at least 2 m o n t h s after the U T I h a d been treated. It is unclear w h e t h e r s o m e o f the small defects detected by D M S A s c i n t i g r a p h y are clinically significant a n d further studies on this are required. In d e c i d i n g an i m a g i n g strategy for the investigation o f a child with U T I s age is i m p o r t a n t : Evidence suggests that new scars are unlikely to develop in those over 5 years o f age [ 16]. C h i l d r e n o f less t h a n 1 y e a r o f age are at highest risk o f d e v e l o p i n g scarring. G l e e s o n s h o w e d s c a r f i n g in 48% o f children u n d e r 1 year with reflux [17]. A n y imaging strategy is c o m p l i c a t e d b y the fact t h a t some children with severe reflux m a y never develop scarfing and it m a y n o t be possible to d e m o n s t r a t e reflux in a child o f u n d e r I y e a r w h o a l r e a d y has renal scarring. W e w o u l d
179
suggest t h a t all children u n d e r 5 years should have a U S scan to detect h y d r o n e p h r o s i s a n d structural a b n o r m a l i ties o f the u r i n a r y tract. US, however, c a n n o t reliably detect mild o r m o d e r a t e l y severe renal scarfing a n d until the significance o f this degree o f scarring is k n o w n children in this age g r o u p s h o u l d also have a D M S A scintigram. In a d d i t i o n children u n d e r 1 y e a r need an M C U to detect reflux before scarring has occurred.
REFERENCES
1 Wallace DMA, Rothwell DL, Williams DI. The long term follow-up of surgically treated vesicoureteric reflux. British Journal of Urology 1978;50:479-484. 2 White RH. Vesicoureteric reflux and renal scarring. Archives of Disease in Childhood 1989;64:407-412. 3 Whitear P, Shaw P, Gordon I. Comparison of99Tcmdimercaptosuccinic acid scans and intravenous urography in children, British Journal of Radiology 1990;63:438-443. 4 Winberg J, Andersen H J, Bergstrom T, Jacobsson B, Larson H, Lincoln K. Epidemiology of symptomatic UTI in childhood. Acta Paediatrica Scandinavica 1974;63 (Suppl. 252): 1 20. 5 Verber IG, Strudly MR, Meller ST. 99mTCdimercaptosuccinic acid (DMSA) scan as first investigation of urinary tract infection. Archives of Disease in Childhood 1988;63:1320-1325. 6 Mason WG Jr. Urinary tract infection in children: renal ultrasound evaluation. Radiology 1984;153:109 111. 7 Leonidas JC, McCauley RGK, Klauber GC, Fretzayas AM. Sonography as a substitute for excretory urography in children with urinary tract infection. American Journal of Radiology 1985; 144:815-819. 8 Kangarloo H, Gold RH, Fine RN, Diament MJ, Boechat MI. Urinary tract infection in infants and children evaluated by ultrasound. Radiology 1985;154:367-373. 9 Monsour M, Azmy AF, Mackenzie JR. Renal scarring secondary to vesicoureteric reflux. Critical assessment and new grading. British Journal of Urology 1987;60:320-324. 10 Merrick MV, Uttley WS, Wild SR. The detection ofpyelonephritic scarring in children by radioisotope imaging. British Journal o f Radiology 1980;53:544-556. 11 Filly R, Friedland GW, Govan GE, Fair RW. Development and progression of clubbing and scarring in children with recurrent urinary tract infection. Radiology 1974;113:145-153. 12 Verber IG, Meller ST. Serial 99mTc dimercaptosuccinic acid (DMSA) after urinary tract infections presenting before the age of five years. Archives of Disease in Childhood 1989;64:1533-1537. 13 SmellieJM, Shaw PJ, Prescod NP, Bantock HM. 99mTCdimercaptosuccinic acid (DMSA) scan in patients with established radiological renal scarring. Archives of Disease in Childhood 1988;63:1315 1319. 14 Goldraich NP, Ramos OL, Goldraich IH. Urography versus DMSA scan in children with vesicoureteric reflux. Paediatric Nephrology 1989;3:1-5. 15 Tappin DM, Murphy AV, Mocan H, Shaw R, Beattie TJ, McAllister TA et al. A prospective study of children with first acute symptomatic E. coli urinary tract infection. Early 99mTechnetium dimercaptosuccinic acid scan appearances. Acta Paediatrica Scandinavica 1989;78:923-929. 16 Birmingham Reflux Study Group. Prospective trial of operative versus non-operative treatment of severe vesicoureteric reflux in children: two years' observation in 96 children. British Medical Journal 1983;287:171 174. 17 Gleeson FV, Gordon I. Imaging in urinary tract infection. Archives o f Disease in Childhood 1991;66:1282-1283.
Can Ultrasound Reliably Detect Renal Scarring in Children With Urinary Tract Infection? A. D. TASKER, D. R. M. L I N D S E L L and M. M O N C R I E F F *
Departments of Radiology and *Paediatrics, John Radcliffe Hospital, Oxford One hundred children with a proven urinary tract infection were studied prospectively using both ultrasound (US) and 99mTc dimercaptosuccinic acid (DMSA) scintigraphy to assess the efficacy of U S in the detection of renal scarring. Sixty-nine girls and 31 boys with an age range of 0.5-11.8 years were studied. D M S A scintigraphy detected 19 scarred kidneys in 17 children. Scarring was classified as mild, moderate or gross. U S detected a total of seven of the scarred kidneys (sensitivity 37%). US detected 0/6 kidneys with mild scarring, 1/7 kidneys with moderate scarring and 6/6 kidneys with gross scarring. Four kidneys with scarring on D M S A showed abnormalities other than scarring on US. 8/19 scarred kidneys were thought to be normal on US. It is important to detect renal scarring in young children and US cannot be relied upon for this purpose. It should therefore be supplemented with D M S A scintigraphy. Tasker, A.D., Lindsell, D.R.M. & Moncrieff, M. (1993). Clinical Radiology 47, 177-179. Can Ultrasound Reliably Detect Renal Scarfing in Children With Urinary Tract Infection?
Accepted for Publication 2 October 1992
Reflux nephropathy is a major cause o f renal failure and hypertension in children and adults. Eight percent of patients with reflux nephropathy and renal scarfing will develop hypertension [1] and in 5-6% of patients with end stage renal failure the cause will be reflux nephropathy [2]. It may be possible to prevent these complications if the scarring is detected early. Renal scarring can be demonstrated on intravenous urography (IVU), ultrasound (US) and technetium 99m dimercaptosuccinic acid (DMSA) scintigraphy. DMSA scintigraphy has been shown to be more sensitive than IVU in the detection of renal scars [3], but there are relatively few studies comparing DMSA scintigraphy and US. This study compares directly the ability of DMSA scintigraphy and US to detect scarring. PATIENTS AND M E T H O D S One hundred unselected children referred to a paediatric outpatient department with a proven urinary tract infection (UTI) were examined prospectively by US and DMSA scintigraphy. The investigations were performed on the same day whenever possible. The age range was 0.5-11.8 years. There were 69 girls with a mean age of 4.7 years and 31 boys with a mean age of 4.6 years. DMSA scintigraphy was performed at least 2 months after the UTI. The dose was calculated by correcting for surface area from the standard adult dose of 50 MBq of Tc 99m DMSA. Three hours later images were obtained in the posterior and both posterior-oblique projections using an IGE 400T maxicamera. Differential renal function was provided by computer analysis. The images were reviewed by two radiologists. Renal size and the size, number and position of any photon deficient areas, persisting at least 2 months after the UTI, were assessed. Scarring on DMSA scans was classified into three groups: Correspondenceto: Dr D. R. M. Lindsell,Department of Radiology, John RadcliffeHospital,HeadleyWay,Headington,OxfordOX39DU.
(1) Minor - a single, small peripheral defect in the renal outline (Fig. la). (2) Moderate - two or three defects in the renal outline with no reduction in renal size and normal differential function (Fig. lb). (3) Gross - m o r e than three defects in the renal outline and/or a reduction in renal size and split renal function falling outside the normal range of 45-55% (Fig. lc). The ultrasound scans were all performed by a consultant radiologist with an interest in US using an Acuson 128 machine with a 5 or 3.5 MHz sector transducer. The patient was scanned in the supine, supine-oblique and prone positions. A note was made of renal size, scarring (Fig. 2), pelvicalyceal dilatation or other evidence of reflux nephropathy, such as ureteric dilatation. The bladder was also assessed. RESULTS The examinations were normal in 74/100 children (52 girls and 22 boys). Seventeen children had 19 scarred kidneys on DMSA scintigraphy. The mean age of children with renal scarring was 4.2 years (0.5-8.4 years). 12/69 girls (17.4%) and 5/31 boys (16.1%) had scarred kidneys. Of the 12 girls with scarring five had gross scarring, five had moderate scarring and two had mild scarring. One of the five boys had gross scarring and four had mild scarring. The DMSA results were taken as a gold standard and were compared with the US findings (Fig. 3). US detected 7/19 kidneys which had been demonstrated to have scars on DMSA (sensitivity 37%). US detected 0/6 kidneys with mild scarfing, 1/7 kidneys with moderate scarring and 6/6 kidneys with gross scarring. In four of the scarred kidneys where US failed to demonstrate scarring it showed dilatation of the pelvicalyceal system suggesting vesicoureteric reflux. These children were therefore inves-
178
CLINICAL RADIOLOGY
Fig. 2 - US examination of a grossly scarred and shrunken kidney.
O. ~a c
(a)
| <
6
" " ".5 " / / / . 6".
(D t/, r O r
~
. . . . . . . .
r r r I rw//////, r / I,.//,./z/-
I
4
",//////M/,
2
~/////////,
g ~9 ..O
E z
//////////
Mild
(b)
Moderate
Gross
Degree of scarring on DMSA St0dy Findings at US
9
Normal
[] ]
Scarring Other eg pelvicalyceal dilatation
Fig. 3 Correlation of scarring on D M S A scintigraphy with US findings.
Table 1 - Number of UTIs per child with renal scarring
(c) Fig. 1 - D M S A scintigraphy demonstrating 'minor' scarring (a), 'moderate' scarring (b) and 'gross' scarring (c).
tigated further with a micturating cystourethrogram and the presence of reflex was confirmed. However, 8/19 (42%) scarred kidneys were thought to be completely normal when assessed by ultrasound. In seven children with normal DMSA scintigraphy the US was thought to be abnormal. Five patients showed
Scarring
Range
Mean
Mild Moderate Gross
1-3 1 1-5
1.5 1.0 3.5
dilatation of the renal collecting system on US and in three of these cases micturating cystourethrography (MCU) demonstrated reflux. Two patients had findings suggesting mild scarring on ultrasound but a normal DMSA study. These were considered to be 'false positive' US diagnoses o f scarring. The number o f urinary tract infections was documented for each child at the time of the scans. Table 1 shows the number o f UTIs that each child with renal scarring had had at the time of presentation.
RENAL SCARRING IN URINARY TRACT INFECTION DISCUSSION U T I in c h i l d h o o d is c o m m o n , affecting 3% o f girls a n d 1% o f b o y s [4]. R e n a l d a m a g e occurs d u e to p y e l o t u b u l a r backflow o f infected urine a n d 10-28% o f these will develop cortical s c a r r i n g [4,5]. It is i m p o r t a n t therefore to detect vesicoureteric reflux a n d renal scarring early, especially in the y o u n g e r age g r o u p w h o are m o s t susceptible to scarring. It has been widely suggested t h a t U S should be the initial investigation o f U T I [6,7]. T h e n o n i n v a s i v e n a t u r e o f US, its lack o f ionizing r a d i a t i o n a n d the ease with which investigations can be r e p e a t e d are a d v a n t a g e s . U S has been s h o w n to be an excellent m e t h o d for detecting structural a b n o r m a l i t i e s o f the u r i n a r y tract such as h y d r o n e p h r o s i s , ureteric d i l a t a t i o n a n d b l a d d e r lesions. It is, however, o p e r a t o r - d e p e n d e n t . This s t u d y clearly shows it to be m u c h less sensitive in the detection o f mild and m o d e r a t e scarring t h a n D M S A scintigraphy. This accords with the w o r k o f K a n g a r l o o e t al. who also f o u n d that u l t r a s o u n d was p o o r at detecting small focal renal defects [8]. Studies c o m p a r i n g I V U a n d D M S A have s h o w n that I V U is less sensitive in the detection o f renal scars [5,9]. M e r r i c k studied 79 children a n d f o u n d a sensitivity o f 60% a n d a specificity o f 92% for I V U c o m p a r e d to a sensitivity o f 96% a n d a specificity o f 98% for scintigraphy [10]. It has also been shown t h a t scars m a y take u p to 2 years to b e c o m e evident on I V U [11]. M o s t studies have s h o w n D M S A s c i n t i g r a p h y to be the most sensitive m e t h o d o f detecting scarring [8,9,12]. Occasional conflicting studies have been published. Smellie studied 52 children in w h o m D M S A failed to detect 6/72 scars seen o n I V U a n d u n d e r - e s t i m a t e d a n o t h e r 13 [ 13]. W h e n e v a l u a t i n g D M S A s c i n t i g r a p h y the timing o f a n y preceding U T I m u s t be t a k e n into consideration in o r d e r to differentiate p o t e n t i a l l y reversible defects in i s o t o p e u p t a k e f r o m those which are p e r m a n e n t [14,15]. V e r b e r a n d Meller d e m o n s t r a t e d t h a t in 49 kidneys with defects seen on the initial scan, only 39 (80%) r e m a i n e d at a m e a n o f 2.25 years [12]. F o r this reason the D M S A s c i n t i g r a p h y in o u r s t u d y was d e l a y e d for at least 2 m o n t h s after the U T I h a d been treated. It is unclear w h e t h e r s o m e o f the small defects detected by D M S A s c i n t i g r a p h y are clinically significant a n d further studies on this are required. In d e c i d i n g an i m a g i n g strategy for the investigation o f a child with U T I s age is i m p o r t a n t : Evidence suggests that new scars are unlikely to develop in those over 5 years o f age [ 16]. C h i l d r e n o f less t h a n 1 y e a r o f age are at highest risk o f d e v e l o p i n g scarring. G l e e s o n s h o w e d s c a r f i n g in 48% o f children u n d e r 1 year with reflux [17]. A n y imaging strategy is c o m p l i c a t e d b y the fact t h a t some children with severe reflux m a y never develop scarfing and it m a y n o t be possible to d e m o n s t r a t e reflux in a child o f u n d e r I y e a r w h o a l r e a d y has renal scarring. W e w o u l d
179
suggest t h a t all children u n d e r 5 years should have a U S scan to detect h y d r o n e p h r o s i s a n d structural a b n o r m a l i ties o f the u r i n a r y tract. US, however, c a n n o t reliably detect mild o r m o d e r a t e l y severe renal scarfing a n d until the significance o f this degree o f scarring is k n o w n children in this age g r o u p s h o u l d also have a D M S A scintigram. In a d d i t i o n children u n d e r 1 y e a r need an M C U to detect reflux before scarring has occurred.
REFERENCES
1 Wallace DMA, Rothwell DL, Williams DI. The long term follow-up of surgically treated vesicoureteric reflux. British Journal of Urology 1978;50:479-484. 2 White RH. Vesicoureteric reflux and renal scarring. Archives of Disease in Childhood 1989;64:407-412. 3 Whitear P, Shaw P, Gordon I. Comparison of99Tcmdimercaptosuccinic acid scans and intravenous urography in children, British Journal of Radiology 1990;63:438-443. 4 Winberg J, Andersen H J, Bergstrom T, Jacobsson B, Larson H, Lincoln K. Epidemiology of symptomatic UTI in childhood. Acta Paediatrica Scandinavica 1974;63 (Suppl. 252): 1 20. 5 Verber IG, Strudly MR, Meller ST. 99mTCdimercaptosuccinic acid (DMSA) scan as first investigation of urinary tract infection. Archives of Disease in Childhood 1988;63:1320-1325. 6 Mason WG Jr. Urinary tract infection in children: renal ultrasound evaluation. Radiology 1984;153:109 111. 7 Leonidas JC, McCauley RGK, Klauber GC, Fretzayas AM. Sonography as a substitute for excretory urography in children with urinary tract infection. American Journal of Radiology 1985; 144:815-819. 8 Kangarloo H, Gold RH, Fine RN, Diament MJ, Boechat MI. Urinary tract infection in infants and children evaluated by ultrasound. Radiology 1985;154:367-373. 9 Monsour M, Azmy AF, Mackenzie JR. Renal scarring secondary to vesicoureteric reflux. Critical assessment and new grading. British Journal of Urology 1987;60:320-324. 10 Merrick MV, Uttley WS, Wild SR. The detection ofpyelonephritic scarring in children by radioisotope imaging. British Journal o f Radiology 1980;53:544-556. 11 Filly R, Friedland GW, Govan GE, Fair RW. Development and progression of clubbing and scarring in children with recurrent urinary tract infection. Radiology 1974;113:145-153. 12 Verber IG, Meller ST. Serial 99mTc dimercaptosuccinic acid (DMSA) after urinary tract infections presenting before the age of five years. Archives of Disease in Childhood 1989;64:1533-1537. 13 SmellieJM, Shaw PJ, Prescod NP, Bantock HM. 99mTCdimercaptosuccinic acid (DMSA) scan in patients with established radiological renal scarring. Archives of Disease in Childhood 1988;63:1315 1319. 14 Goldraich NP, Ramos OL, Goldraich IH. Urography versus DMSA scan in children with vesicoureteric reflux. Paediatric Nephrology 1989;3:1-5. 15 Tappin DM, Murphy AV, Mocan H, Shaw R, Beattie TJ, McAllister TA et al. A prospective study of children with first acute symptomatic E. coli urinary tract infection. Early 99mTechnetium dimercaptosuccinic acid scan appearances. Acta Paediatrica Scandinavica 1989;78:923-929. 16 Birmingham Reflux Study Group. Prospective trial of operative versus non-operative treatment of severe vesicoureteric reflux in children: two years' observation in 96 children. British Medical Journal 1983;287:171 174. 17 Gleeson FV, Gordon I. Imaging in urinary tract infection. Archives o f Disease in Childhood 1991;66:1282-1283.