A man has said he faces weeks in agony after doctors failed to perform an operation to remove his kidney stones.

Simon Mallia was taken by ambulance to Lister Hospital in Stevenage on Thursday after the stones – balls of waste that crystallise in the blood and collect in the kidneys – left him unable to move due to the pain.

The 39-year-old was given the option of having a ureteric stent – a tube placed between the bladder and kidney to relieve pressure and help the stones to pass – or laser treatment using a powerful beam to break down the stones.

Mr Mallia, a self-employed engineer, opted for the second procedure and was told he would have an operation on Monday.

After he returned from surgery in the early hours of Tuesday morning, he found that the stones had not been removed and instead a stent had been inserted.

Mr Mallia, whose partner Jodie Norr is due to give birth by Cesarian section on Monday, said: “I am utterly disgusted at how I have been treated. I can’t blame the staff because the nurses have been good as gold and all the doctors have been fine but the management of everything has been appalling.

“I’m in agony and have been since last Thursday. All they did was give me drugs and kept me waiting.

“I waited for four days for them to remove them and now they tell me they’re still there. It’s utterly ridiculous that I’ve been discharged to go home for weeks to suffer in agony before I can have an operation that should have already taken place.

“I’ve just started a new job and there’s no way my boss will keep me on if I say I’ve got to have two, maybe three, months off work to recover. My partner is also due to give birth on Monday, which the hospital knows, so I don’t know why they’re delaying everything.”

A spokesman for the East and North Herts NHS Trust, which runs the hospital in Coreys Mill Lane, said: “Mr Mallia’s procedure was carried out during the evening of Monday, 29 September. The surgeon performing the procedure found that for clinical reasons that could not be foreseen, the laser therapy could not be performed – something that happens with some patients. This meant that the only option was for him to have the stent and then return back to see his consultant in a few weeks time.”