Most urine infections are caused by germs (bacteria) which come from your own bowel. They cause no harm in your bowel but can cause infection if they get into other parts of your body. Some bacteria lie around your back passage (anus) after you pass a stool (faeces). These bacteria sometimes travel to the tube which passes urine from your bladder (the urethra) and into your bladder. Some bacteria thrive in urine and multiply quickly to cause infection.
A urine infection is often called a urinary tract infection (UTI) by doctors. When the infection is just in the bladder and urethra, this is called a lower UTI. If it travels up to affect one or both kidneys as well then it is called an upper UTI. This can be more serious than lower UTIs, as the kidneys can become damaged by the infection.
Urine infections are rare in men aged under 50. They become more common in older men. Urine infection is much more common in women.
What causes a urine infection?
In some cases an underlying problem can increase the risk of developing a urine infection. These include the following:
- An enlarged prostate gland.
- Bladder or kidney problems. For example, kidney stones or conditions that cause urine to pool and not drain properly.
- Having a urinary catheter.
- A poor immune system.
In other cases the infection occurs for no apparent reason. There is no problem with the bladder, kidney, prostate gland, or defence (immune) system that can be identified.
In the average adult patient there should be a urine output of: 0.5-1 ml/kg/hr. This means that an average 70 kg man should produce 35-70 mls an hour.
Urine output decreases in older patients and the target urine output should be 0.25-0.5 ml/kg/hr. This means that a 70 kg man who is aged over 65 years should produce 17.5-35mls per hour.
What are the symptoms of a urine infection?
- Infection in the bladder (cystitis) usually causes pain when you pass urine, and you pass urine more frequently. You may also have pain in your lower tummy (abdomen). Your urine may become cloudy, bloody or smelly. You may have a high temperature (fever).
- Infection in the kidneys may cause pain in a loin (the side of the abdomen over your kidney) and a high temperature (fever). It may cause you to feel sick or be sick (vomit). You may feel generally unwell.
In some elderly men, the only symptoms may be a recent onset of confusion or just feeling generally unwell, even without any actual urinary symptoms.
Are any tests needed?
A urine sample can confirm the diagnosis and identify the germ (bacterium) causing the infection. Further tests are not usually necessary if you are otherwise well and have a one-off infection. However, your doctor may advise tests of your kidney, prostate gland, or bladder if an underlying problem is suspected.
An underlying problem is more likely if the infection does not clear with an antibiotic medicine, or if you have:
- Symptoms that suggest a kidney is infected (and not just the bladder).
- Recurring urine infections. For example, two or more in a three-month period.
- Had problems with your kidney in the past, such as kidney stones or a damaged kidney.
- Symptoms that suggest an obstruction to the flow of urine.
- Blood-stained urine which persists after treatment with antibiotics.
Tests may include:
- An examination of your prostate gland by examination of your back passage (rectum).
- A general blood test or a specific blood test to check on your prostate, called prostate specific antigen, or PSA.
- A scan of your kidneys or bladder such as an ultrasound scan.
- An X-ray to look for kidney stones.
- A look inside your bladder with a special telescope (cystoscopy).
- Tests to see how well your bladder is working, called urodynamic tests.
What is the treatment of a urine infection?
- A course of an antibiotic medicine will usually clear the infection quickly. This is usually for seven days. You should see a doctor if your symptoms are not gone, or nearly gone, after a few days.
- Paracetamol or ibuprofen will usually ease any pain, discomfort, or high temperature (fever).
- Have plenty to drink to help prevent a lack of fluid in the body (dehydration) if you have a fever and feel unwell.
What is the outlook (prognosis)?
The vast majority of men improve within a few days of starting treatment. See a doctor if you do not quickly improve. If your symptoms do not improve despite taking an antibiotic medicine then you may need an alternative antibiotic. This is because some germs (bacteria) are resistant to some types of antibiotics. This can be identified from tests done on your urine sample.
Occasionally the infection may spread and cause you to be more unwell. Infection in the bladder (cystitis) may spread to the kidney (pyelonephritis). Infection may also spread to involve the prostate gland, causing infection of the prostate gland (prostatitis). Occasionally it may lead to a swelling caused by a collection of pus (abscess) in the prostate gland.
Further reading and references
Guidelines on Urological Infections; European Association of Urology (2019)
Urinary tract infection (lower): antimicrobial prescribing; NICE Guidance (October 2018)
Urinary tract infection (lower) - men; NICE CKS, November 2018 (UK access only)
Smithson A, Ramos J, Nino E, et al; Characteristics of febrile urinary tract infections in older male adults. BMC Geriatr. 2019 Nov 2919(1):334. doi: 10.1186/s12877-019-1360-3.