The problem is not serious and the Spaniard is expected to be back at work before the end of the week.

The news comes just days after his Chelsea counterpart Luiz Felipe Scolari revealed he had been suffering from the same complaint.

A Liverpool spokesman said: "Rafa was admitted to hospital last night after suffering problems with a kidney stone.

"He will undergo a minor operation this afternoon and is expected to return to work within two or three days.

"He remains in good spirits and everyone at Liverpool wishes him a very speedy recovery."