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Indian Pediatr 2015;52:
315-317 |
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Early Dimercaptosuccinic Acid Renal Scan in
Children With First Febrile
Urinary Tract Infection
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K Umamageswari, B Antony Terance and *N Anirudhan
From Departments of Pediatrics and *Nuclear Medicine,
G Kuppuswamy Naidu Memorial Hospital, Coimbatore, India.
Correspodence to: Dr Umamageswari K, G Kuppuswamy
Naidu Memorial Hospital, P N Palayam, Coimbatore.
Email: [email protected]
Received: June 19, 2014;
Initial review: August 04, 2014;
Accepted: February 10, 2015.
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Objective: To determine use of early Tc-99m
dimercaptosuccinic acid scintigraphy in screening for vesicoureteral
reflux following first febrile urinary tract infection. Methods:
43 children (1 mo-5 yr) with first febrile urinary tract infection
underwent micturating cystourethrography, abdominal sonogram and early
dimercaptosuccinic acid scintigraphy. Results: Early
dimercaptosuccinic acid scintigraphy had 72% sensitivity and 76%
specificity for vesicoureteral reflux. For dilating vesicoureteral
reflux, sensitivity and specificity were 100% and 75%, respectively.
Conclusion: Early dimercaptosuccinic acid scintigraphy has the
potential to replace micturating cystourethrography in initial
evaluation of febrile urinary tract infection.
Keywords: Diagnosis, Vesicoureteral reflux, Scintigraphy,
Screening.
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S
creening for vesicoureteral reflux (VUR) is an
important part of evaluation in children with urinary tract infection
(UTI) as it can lead to reflux nephropathy and renal scarring. VUR is
detected in 30% to 70% of these children [1,2]. Micturating
cystourethrography (MCU) remains the gold standard for diagnosing and
grading VUR but the procedure is cumbersome. Recent studies have
reported that a normal early dimercaptosuccinic acid (DMSA) renal scan
excludes dilating VUR, and hence MCU can be avoided [2-4]. However, some
other studies indicate that even clinically significant VUR is missed by
early DMSA scans [5]. The extent to which DMSA scintigraphy can replace
MCU is still unknown. This study was undertaken to assess the role of
early DMSA scan in children with first episode of febrile UTI.
Methods
Between May 2011 and April 2013, children (age 1 mo-5
yr) with first episode of febrile (temp. >37.5ºC) UTI (Urine culture
showing colony count of 10 5
CFU, >104 CFU and
³1 CFU for midstream
clean catch, catheterisation and suprapubic aspiration samples,
respectively) [6] were eligible for this study. Children with anatomical
and neurological genitourinary abnormalities, previously diagnosed renal
disease, recurrent UTI and atypical UTI (presence of poor urinary
stream, abdominal mass, raised creatinine, septicemia and serious
illness) were excluded. The study was approved by the Institutional
Ethical committee. Purposive sampling technique was adopted and informed
consent was obtained from parents of included children.
Renal ultrasonography (USG) was done soon after the
diagnosis of UTI. DMSA renal scan was performed within 10 days of onset
of fever. MCU was done after completion of the treatment of UTI when
repeat cultures were sterile. USG was considered positive when there
were features suggestive of pyelonephritis or dilated ureter. Early DMSA
was taken positive when there were: (a) evidence of acute
pyelonephritis, defined as single or multiple cortical defects having
reduced tracer localization with indistinct margin without deforming
renal contour; or (b) possible cortical scarring defined as,
cortical thinning, ovoid or wedge shaped defect with sharp edges. Reflux
was graded according to the international system of radiographic grading
of VUR.
Data were analyzed using SPSS version 17.0. Mean,
standard deviation, sensitivity, specificity, positive and negative
predictive value, and likelihood ratios were used to interpret the data.
Results
A total of 43 children with first episode febrile UTI
were included, of which VUR was identified in 22 (51%) children. Eleven
out of 14 children with dilating VUR, and five out of seven children
with bilateral VUR were below 2 years of age. USG showed positive
findings in seven children, with low sensitivity and high specificity
for VUR (Table I).
TABLE I Diagnostic Performance of USG and Early DMSA in Detecting VUR and Dilating VUR
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Test |
VUR |
Dilating VUR |
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USG |
Early DMSA |
USG |
Early DMSA |
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Sensitivity |
29 |
72 |
28 |
100 |
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Specificity |
90 |
76 |
89 |
75 |
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PPV (%) |
71 |
76 |
57 |
66 |
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NPV (%) |
52 |
72 |
72 |
100 |
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Positive LR |
2.9 |
3 |
2.55 |
4 |
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Negative LR |
0.78 |
0.36 |
0.8 |
0 |
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USG - Ultrasonography; DMSA – Dimercaptosuccinic acid renal
scan; VUR Vesicoureteral reflux; PPV- positive predictive value;
NPV- Negative predictive value; LR – Likelihood ratio. |
Abnormal DMSA scan was found in 21 patients in form
of reduced cortical uptake (11 children) and possible cortical scars (10
children). All children with Grade III, IV and V reflux (dilating VUR)
had a positive early DMSA scan. The association between a positive DMSA
and presence of VUR in MCU was statistically significant (P<0.001).
The overall accuracy rate for the presence of VUR with a positive DMSA
scan was 74% (Table I).
Discussion
About half of children with first febrile UTI had VUR
in our study. Early DMSA renal scan was found to have high sensitivity
and negative predictive value for detection of dilating VUR in our
study.
The major limitation of this study was small sample
size, due to which association between presence of dilating VUR with age
group, and USG findings with grades of VUR could not be evaluated.
Lower sensitivity of USG abdomen in detection of VUR
has also been demonstrated in other studies [7]. High sensitivity and
high negative predictive value of early DMSA renal scan for VUR, as seen
in this study has also been observed in some other studies [8-10].
Though contradicting results are observed in some studies [5,10], it has
been observed that in children with dilating VUR missed out by early
DMSA, development of significant renal disease was uncommon [3,12,13].
Some guidelines recommend detailed evaluation only after the second
episode of febrile UTI but this may not be ideal in our population due
to higher proportion of children having VUR and uncertainty in follow
up. Although both DMSA and MCU employ a considerable amount of
radiation, DMSA is still advantageous over MCU as it delivers radiation
to relatively radio-resistant kidneys sparing the gonads [3].
To conclude, the risk of missing clinically
significant VUR is very low with early DMSA scan (top-down approach).
Further studies with larger sample size, including different age groups
are required to validate these findings.
Contributors: All authors were involved in all
aspects of study conduct and manuscript preparation.
Funding: None; Competing interest: None
stated.
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What This Study Adds?
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Early DMSA scintigraphy can be
used in evaluation of under-five children with first episode of
febrile urinary tract infection.
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