The elderly Fox Terrier Cross, named 'Brandy' was put down due to her condition.
RSPCA South Australia officers found Brandy inside a fenced enclosure at the man's home in 2017.
Brandy was surrounded by her own faeces and was suffering significant medical issues.
They included an enlarged eye, a collapsed eye, an ingrown and infected toenail causing an abscess, advanced periodontal disease, bilateral ear infections and roundworm infestation.
RSPCA South Australia’s Chief Veterinarian Dr Brad Ward says Brandy would have suffered "a very high degree of pain over a long period of time" as a result of the conditions.
Given her pain and poor prognosis, euthanasia was deemed the only humane option.
Geoffrey Mortenson, 54, pleaded guilty in Elizabeth Magistrates Court on Tuesday to two charges of ill treatment of an animal.
Mortenson was sentenced the defendant to six months and two weeks imprisonment, which was suspended.
He was also forced to pay costs of $3950 to the RSPCA South Australia.
RSPCA South Australia Chief Inspector Andrea Lewis described the level of neglect endured by Brandy as among the worst she had seen.
“This was an older dog, blind, deaf and totally vulnerable, who was completely abandoned by her owners when she needed them the most,” Lewis said.
“No animal should be left to suffer to that degree for that long.
This story first appeared on 7NEWS and has been republished here with permission.