Dosing paediatric contrast by lean body weight cut the volume without losing hepatic enhancement

Design

Prospective randomised comparison of three contrast dosing protocols for paediatric abdominal CT

Population

66 patients aged 0-16 undergoing contrast-enhanced abdominal CT, September 2023 to August 2024; 23 lean body weight, 20 total body weight, 23 institutional control

Primary outcome

Contrast volume administered and hepatic enhancement quality

Effect

Median volume 27 mL (IQR 10-80) lean body weight vs 34.5 mL (18-78) total body weight vs 40 mL (13-80) control, differences not significant; hepatic enhancement 552 plus or minus 139 HU, p=0.107 versus control

Iodinated contrast in paediatric CT is dosed by total body weight, which means a child with more adiposity receives more contrast for a fat compartment that does not take it up. Lean body weight dosing has been studied in adults and barely in children. This prospective study randomised 66 children aged 0-16 having contrast-enhanced abdominal CT between September 2023 and August 2024 to three protocols: lean body weight (0.63 g iodine/kg of lean weight, Peters formula, n=23), total body weight (0.46 g iodine/kg, n=20), or the institutional standard of 2 mL/kg total body weight, equal to 0.7 g iodine/kg (n=23).

Median contrast volume was lowest in the lean body weight group at 27 mL (IQR 10-80) against 34.5 mL (18-78) for total body weight and 40 mL (13-80) for the institutional protocol. Those differences did not reach statistical significance. Hepatic enhancement in the lean body weight group remained comparable to the control at 552 plus or minus 139 HU (p=0.107).

Read the statistics honestly: with 66 children in three arms this study was underpowered for the volume comparison, and 'not significant' here means not demonstrated rather than not real. The interquartile ranges overlap almost completely because the children span 0 to 16 years, so age variation swamps protocol variation.

What makes it worth acting on anyway is the direction and the safety endpoint. Enhancement quality - the thing you would lose by cutting the dose - did not deteriorate, and the reduction in volume falls specifically on children with higher adiposity, who are the ones currently overdosed. Contrast-induced nephropathy risk and, more practically, the total iodine load over a childhood of repeat scans both argue for individualising. This is early evidence in a small sample; the reasonable step is to pilot lean body weight dosing with enhancement audit rather than to adopt it wholesale.

• Pilot lean body weight contrast dosing in paediatric abdominal CT with a prospective enhancement audit
• Record height as well as weight - lean body weight formulas need both
• Audit hepatic enhancement in Hounsfield units so a dose reduction can be checked, not assumed
• The gain falls on children with higher adiposity; in lean children the protocols converge
• Sixty-six children across three arms - treat this as a reason to pilot, not to change policy

The statistics, in plain English

The volume difference between protocols did not reach statistical significance, which in 66 children across three arms tells you very little - the study was too small to detect a difference of this size, so the medians (27 vs 34.5 vs 40 mL) are the informative part and the p value is not. The enhancement comparison is the opposite case and is more reassuring: p=0.107 for hepatic enhancement means no difference was demonstrated in the outcome you would worry about losing, though a small trial can also miss a real deterioration. Wide interquartile ranges reflect the 0-16 year age span rather than protocol inconsistency.

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