The son of Chicago's police chief has been sworn in as a rookie officer just a year after he donated a kidney to his dad.

Daniel Johnson, 26, received a big hug from his father Superintendent Eddie Johnson, 58, as he walked across the stage on Tuesday, with the elder Johnson calling it 'one of the most special days' of his life.

Eddie was diagnosed more than three decades ago with acute kidney inflammation.

Doctors thought his kidneys would only work for a few more years, but it was not until 2016 when the situation became serious.

His kidney function dropped to 10 percent capacity and doctors told him that he was in desperate need of a kidney transplant.

No match was found after months of donor screenings until it was revealed that Daniel was a match and planning to donate his kidney to his father.

Daniel Johnson, 26 (right), was sworn in as a Chicago police officer on Tuesday just a year after he donated a kidney to his father Superintendent Eddie Johnson (right)

Daniel received a big hug from Eddie (pictured) as he walked across the stage, with the elder Johnson calling it 'one of the most special days' of his life

Glomerulonephritis is an acute inflammation of the kidney that affects the glomeruli.

These are tiny structures that filter the kidneys, removing excess fluid, electrolytes and waste from your bloodstream through your urine.

The disorder can occur on its own or as part of another disease such as diabetes or lupus, according to the Mayo Clinic.

The superintendent has been a central figure in trying to crack down on Chicago's crime.

His condition had gotten to such a dire point that he was forced to reveal at news conference he nearly fainted at that he was diagnosed with the disease more than 30 years ago when he first tested to become a cop in the Windy City.

He had informed Mayor Rahm Emanuel of his condition after he was picked as superintendent in March 2016.

'So when I was diagnosed, I was 25 years old and, at the time the doctor...thought that my kidneys would probably last three to four years. And it's been 31 years,' Eddie said, according to the Chicago Tribune.

He said it was only in 2016 when his kidneys fell to 10 percent functioning capacity that he was put on a waiting list for a kidney transplant and, even though he made it longer than expected, he was running out of time.

Eddie (pictured) revealed in January that he was diagnosed three decades ago with glomerulonephritis an acute inflammation of the kidney that affects the glomeruli - tiny structures that filter the kidneys

After Eddie revealed he was on a transplant waiting list because his kidneys were functioning at 10 percent capacity, Daniel was tested and found to be a match. Pictured: Eddie, left, and Daniel, right

Eddie's nephrologist, Dr Paul Crawford, also spoke at the news conference where the superintendent's kidney disease was revealed.

According to the Tribune, Dr Crawford said that African-Americans are three to four times more likely to develop kidney disease due to a higher prevalence of diabetes or high blood pressure among that race.

After his dad's very public announcement, Daniel decided to get tested and was found to be a match.

The operation took place on August 31, 2017 at Rush University Medical Center in Chicago.

You always were centered around helping and giving back to others. And that includes helping me Superintendent Eddie Johnson to his son Daniel Johnson

Just three days later, the superintendent was discharged from the hospital.

At the time, the medical center released a statement that read in part: 'According to Mr Johnson's transplant team, his kidney function is excellent. He is in good condition and making great progress.'

In just a little more than six weeks, Eddie had made such great strides that he was able to return to work at the Chicago Police Department.

Although a kidney transplant does not last forever, the average life span of a transplanted kidney from a living donor is about 15 years.

On average, people can live 10 to 20 years after a kidney transplant.

At the time of the transplant, Daniel was working as an elementary school teacher but told his father he was in the process of applying to become a Chicago cop.

Almost a year to the date of the surgery, the elder Johnson was able to watch his son be sworn in as a member of the force at the graduation ceremony at Navy Pier on Tuesday.

The operation took place on August 31, 2017 at Rush University Medical Center in Chicago and was declared to be a success. Pictured: Eddie Johnson at a press conference, right, with Mayor Rahm Emanuel, left

At the time of the transplant, Daniel was working as an elementary school teacher but told his father he was in the process of applying to become a Chicago cop. Pictured: Daniel shakes hands with Mayor Emanuel

'I'm not just here as superintendent. I get to stand before you as a dad watching my son follow in my footsteps. I promised him that I wouldn't do this,' Johnson told the audience as they applauded, according to the Chicago-Sun Times.

Despite promising his son he'd keep the speech about police business, Eddie couldn't help himself and was overcome with emotion.

'I'm so incredibly proud of the young man you have become. Since you were a little boy to when you decided to become a schoolteacher and now, a police officer, you have embodied the meaning of service,' he said.

'You always were centered around helping and giving back to others. And that includes helping me.'

There were 218 officers, 69 percent of whom are minorities and 20 percent of whom have family in the Chicago PD, in Tuesday's graduating class.

There were also 111 newly-promoted detectives as part of Emanuel's push to hire more than 1,000 police officers to the force to combat the city's poor clearance rate for homicides and shootings.