Failures in basic hospital care are resulting in more than 1,000 deaths a month from the preventable condition acute kidney injury (AKI), an NHS report has found.
Almost half a million of the three million people admitted to hospital in England each year develop the illness, with between 15,000 and 40,000 dying as a result. Dubbed "the silent killer" because it often goes undetected by many medical staff, AKI is often overlooked due to other illnesses patients are suffering.
It involves the sudden loss of kidney function - often caused by dehydration but also by infections such as pneumonia or flu - that can affect the heart, lungs and brain.
The report commissioned by NHS Improving Quality is the most comprehensive study of the illness to have been conducted in the UK.
It found the condition is five times more prevalent in English hospitals than previously thought.
"Every day more than 30 people are dying needlessly. Compare that to MRSA which was killing about four people a day at its peak," said Marion Kerr, a health economist for Insight Health Economics.