The 31-year-old man was described as being in a "stable" condition in Manchester Royal Infirmary yesterday after undergoing emergency surgery.
Emergency services were called to a house in the Moss Side area of the city at 11.45 on Sunday morning, where they found the man bleeding but conscious. A spokesman for Greater Manchester Ambulance Service said the man was in a "distressed" state as "his genitals had been sliced".
"He was bleeding heavily but amazingly was still conscious and able to walk around. The man had arrived at [the house] after the injuries had occurred ... Paramedics failed to find any trace of the genitals."
It is understood that the man had gone to the home of a former girlfriend after the injury occurred. A woman was interviewed by police yesterday but was thought to have nothing to do with the incident.
A Greater Manchester police spokeswoman said their inquiries were continuing. "He's very reluctant to tell anybody anything. We've not found a penis end."
Nicholas Parkhouse, a consultant plastic surgeon at The Queen Victoria Hospital in East Grinstead, Sussex, said many factors dictated how possible it was to operate successfully. "The principles of the surgery of repairing apply to the penis as they do to the hand or face."
If the severed penis part was not found, emergency plastic surgery could tidy the wound. After it had healed, which might take around 12 months, reconstructive surgery could then be carried out to build up part of the missing length.
But Mr Parkhouse said: "... it is unlikely the functioning and appearance will ever be entirely normal."