Liam Payne has been rushed to hospital in severe pain from a serious kidney infection
The former One Direction singer, 30, fell ill during a trip to Lake Como in Italy with his girlfriend Kate Cassidy.
The painful and unpleasant disease can cause fever, back pain and a burning sensation when urinating.
If left untreated, it can cause permanent kidney damage.
Here, MailOnline analyzes the early warning signs and symptoms of a kidney infection that you should look out for.
The painful and unpleasant disease can cause fever, back pain and a burning sensation when urinating. If left untreated, it can cause permanent kidney damage
What causes a kidney infection?
A common bladder infection known as cystitis is usually the cause of a kidney infection.
The initial infection may be caused by a type of bacteria called E. coli entering the urethra, a tube that carries urine from your body.
E. coli usually lives in the intestines, but can end up on the genitals during sex or when wiping after going to the toilet.
Although most people who get bladder infections do not develop a kidney infection, bacteria sometimes travel from the bladder to the kidneys.
But in some cases it can develop without a bladder infection if you have kidney stones or a weakened immune system.
According to the NHS, it is crucial to have the infection treated immediately with antibiotics to prevent permanent kidney damage.
Liam Payne was rushed to hospital after suffering agonizing kidney pain during a romantic holiday with his girlfriend (pictured in Lake Como with Kate on Saturday)
Fever
Fever is a common symptom of a kidney infection.
A normal body temperature is around 37 degrees Celsius, but if you have a fever it will be 37.8 degrees Celsius or higher, the NHS says.
If you feel hot, shivery or cold, these are signs of a fever.
The body uses fevers to fight infections because they stimulate the immune system and make it harder for the bacteria and viruses behind infections to survive.
Wearing loose clothing, drinking plenty of water to stay hydrated, and taking acetaminophen can help improve symptoms of fever.
Backache
Pain or discomfort in your lower back, side, or genitals is also a sign of a kidney infection.
It can often feel like a dull ache that can get worse with gentle pressure.
The pain is felt just below the rib cage, where the kidneys are located.
In some cases, only one kidney is infected, leaving only one side painful and tender, the NHS says.
Liam Payne announced last month that he was canceling a tour in South America due to a ‘serious kidney infection’ that left him in hospital
Sudden need to urinate
Kidney infections can also cause symptoms of cystitis or a urinary tract infection.
According to the NHS, this also means having to urinate suddenly or more often.
The bacteria in your bladder, which cause the infection, can cause the area to swell and become irritated.
It is this swelling that causes the urge to go to the toilet more often and with more urgency, experts say.
Pain or burning sensation when urinating
Not only do kidney infections make you urinate more, they can also cause pain or a burning sensation when you do.
This is caused by the inflammation or swelling of the urinary tract, experts say.
Kidney infections are more common in women because a woman’s urethra is shorter than a man’s, making it easier for bacteria to reach the kidneys.
‘Younger women are most at risk because they tend to be more sexually active and frequent sex increases the risk of a kidney infection,’ the NHS says.
Smelly or cloudy urine
Usually the urine is clear or pale yellow, but if the urine becomes cloudy or smelly, it may be a sign of a urinary tract infection or a kidney infection.
That’s because the body sends white blood cells to fight the infection.
Cells are usually excreted through the urine. When the white blood cells mix with the urine, it can cause a cloudy color.
Although a change in the color of urine can be caused by dehydration or certain medications, the NHS says that if this is accompanied by other symptoms, such as pain when urinating, it could be a urinary tract infection.
‘Less commonly, smelly pee can be caused by other conditions such as type 2 diabetes or kidney stones,’ says the NHS.
Blood in your pee
Finding blood in your pee is another symptom of both a UTI and a kidney infection.
But the NHS is urging people to see their GP if symptoms of a urinary tract infection have not improved within a few days, or if they have blood in their pee.
‘Blood in your pee can come from anywhere in the urinary tract: the bladder, kidneys or urethra,’ says the NHS.
A doctor will usually prescribe antibiotics for an infection to prevent the infection from entering the bloodstream.
Most people diagnosed and treated promptly with antibiotics feel completely better after about two weeks.