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Water bottle sign

Dr Frank Gaillard et al.

The water bottle sign or configuration refers to the shape of the cardiac silhouette on erect frontal chest x-rays in patients who have a very large pericardial effusion. Typically the effusion has accumulated over many weeks to months (e.g. in patients with malignancy) and the pericardium has gradually stretched. The fluid, often measuring a litre or more, causes the pericardium to sag, mimicking an old-fashioned watter bottle sitting on the bench.