A "cascade" of medical failures led to a man dying of dehydration in a hospital bed, a coroner has ruled.

Kane Gorny, 22, a keen sportsman who was so desperate for water he phoned police, was not given vital medication to help him retain fluids by staff at St George's hospital in Tooting, south London.

At the inquest, deputy coroner Dr Shirley Radcliffe said "a cascade of individual failures had led to an incredibly tragic outcome". He had died from dehydration contributed to by neglect, she said, recording a narrative verdict.

"Kane was undoubtedly let down by incompetence of staff, poor communication, lack of leadership, both medical and nursing, and a culture of assumption," she said.

After the hearing at Westminster coroners court, his family's solicitor James Stevenson, said they were "devastated by the number of missed opportunities to prevent his death … there were systemic and individual failures in the level of care provided to Kane". Standing beside Gorny's mother, Rita Cronin, he said: "Kane was a well-liked, adoring and loving son, brother and friend."

Radcliffe said she would write to the hospital about nurses involved in fluid management and sedation following Gorny's treatment.

A postmortem blamed high sodium levels caused by dehydration for his death.

The supermarket employee, from Balham, south London, was suffering from diabetes insipidus, a condition that had caused him to be aggressive towards nurses the day before he died in May 2009. He had been sedated and put in a side room.

Gorny was prone to violent behaviour since treatment for a brain tumour. He was undergoing a routine hip replacement at the hospital.

Medical staff were "blinkered" by his previous behavioural problems and said he had a "fixation" with water.

In desperation, he called police saying he had been assaulted by security guards, but when officers arrived, he asked them if he looked thirsty and wanted them to look at his tongue. They left when it was clear no assault had taken place.

The senior staff nurse on the night he died had told the inquest she did not take observations or ensure he took his medication. She said she had been mindful of his earlier behaviour, and his brother, sitting next to his hospital bed, asked her to let him sleep.

His condition deteriorated shortly after her shift ended and, despite efforts to save him for two-and-a-half hours, he was pronounced dead at 11.20am the following morning.

Dr Ros Given-Wilson, medical director at St George's Healthcare NHS Trust, said: "We deeply regret the death of Kane Gorny and have apologised unreservedly to his family for the grief this has caused.

"We provide safe, high-quality healthcare services to over one million patients across south west London every year, but it is clear that the care we provided on this occasion fell short of expectation in a number of respects and for this we are profoundly sorry.

"We have admitted civil liability for the failures in Kane's care and we fully accept the coroner's verdict.

"Since Kane died in 2009, we have made changes to senior leadership on our wards and put a number of patient safety measures in place."