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Melamine-induced urinary calculi in infants--sonographic manifestations and outcomes 1 year after exposure
Fang Nie1, Xin-jie Li, Pan-feng Shang
1Department of Medical Ultrasonics, The Second Hospital of LanZhou University, LanZhou, 730030, People's Republic of China. niefang028@yahoo.com.cn
Insights
Infant urolithiasis caused by melamine can be characterized by ultrasound. Smaller stones (<4 mm) show a comet-tail sign, while larger stones (≥4 mm) appear as echogenic foci in the renal calyx.
Area of Science:
- Pediatric Nephrology
- Diagnostic Imaging
- Toxicology
Background:
- The 2008 melamine-tainted-milk incident in China led to a surge in infant urolithiasis.
- Infants affected by melamine-induced urolithiasis underwent screening for kidney stones.
Purpose of the Study:
- To characterize the sonographic features of infant urolithiasis resulting from melamine exposure.
- To correlate imaging findings with stone size and location.
Main Methods:
- Transabdominal ultrasound (US) was performed on 603 infants with melamine-induced calculi.
- Analysis included imaging characteristics of calculi and associated hydronephrosis.
- Follow-up US examinations were conducted.
Main Results:
- A comet-tail sign was observed posterior to calculi <4 mm.
- Calculi ≥4 mm presented with a clear posterior border, with or without shadowing.
- The inferior renal calyx was the most common site for calculi (55.2%).
- Infants aged 2-3 years showed smaller calculus size and a higher incidence of hydronephrosis (48.0%).
Conclusions:
- Sonography reveals distinct features for melamine-induced calculi based on size: <4 mm stones appear as hyperechoic foci near renal papillae, while ≥4 mm stones present as echogenic foci with visible inferior edges in the renal calyx.
- Hydronephrosis is a frequent finding in infants aged 2-3 years with melamine-induced urolithiasis.
Background:
In 2008, the melamine-tainted-milk incident started with reports of increased incidence of urolithiasis in infants in China. Affected children were screened for urolithiasis.
Objective:
The purpose of this study was to analyze sonographic characterization of infant melamine-induced urolithiasis.
Materials And Methods:
Transabdominal US examination was done in 603 infants with melamine-induced calculi. The imaging characteristics of calculi and hydronephrosis were analyzed. Follow-up US imaging was performed.
Results:
Comet-tail sign was seen behind the calculus of <4 mm. Calculi of ≥ 4 mm were found in 299 inpatients with clear posterior border and with or without light shadowing. Solitary and multiple stones had similar incidence. Incidence of calculi in the inferior renal calyx was the highest (55.2%) in inpatients. Calculus size in inpatients age 2-3 years was smaller than that of children younger than 2 years old (P < 0.05). Inpatients age 2-3 years had the highest incidence rate (48.0%) of hydronephrosis.
Conclusion:
Calculi of <4 mm manifested as hyperechoic foci near the renal papillae, while calculi of ≥ 4 mm usually manifested as echogenic foci with visible inferior edge in the renal calyx. Hydronephrosis was a common imaging finding in inpatients ages 2-3 years.
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