Pus in Urine & Cancer
- Pus in urine (pyuria) is the presence of pus cells in the urine, which can occur due to various causes, including bacterial infections of the urinary tract (UTI) and cancer.
- The presence of pus in urine doesn’t necessarily indicate cancer, as the vast majority of cases are due to infections and stones.
- Suspect cancer as a cause of pus in urine when you have no other reason explaining the pus, and you have other risk factors and symptoms of urinary tract cancer such as bladder or kidney cancer.
- Common urinary tract cancers that can be associated with pus in urine are urinary bladder cancer, kidney cancer, prostate cancer, and ureteric cancer.
- Long-standing pus in the urine itself is not a direct cause of cancer. Still, untreated underlying causes of pus in urine may increase the risk of developing certain types of urinary tract cancers, such as bladder cancer.
 What causes pus in the urine?
Pus in urine (pyuria) is defined as the presence of pus cells (more than three cells/HPF (high power field of the microscope).
According to this definition, pus in urine is not a “clinical” diagnosis based on urine appearance but a laboratory diagnosis.
Pus in urine doesn’t always mean turbidity:
This leads us to the fact that clear, normal-looking urine is not an exclusion for pus in the urine.
Accordingly, you may see pus (as turbid or cloudy urine) or get a diagnosis of pyuria based on urine analysis.
Infection is the main cause of pus in urine:</strong>
Pus in urine occurs primarily due to bacterial infections of the urinary tract (UTI). In such cases, evidence of bacterial infections confirms the cause of pus (a urine culture test to detect the causative bacteria).
UTI is more common in women, and women are 30 times more likely to get UTI (and subsequent pus in urine) than men (reference).
Pus in urine can also occur without infection:
Pus cells in urine can occur due to a wider variety of causes other than infection (including cancer).
The following table illustrates the infectious and non-infectious causes of pus in urine (pyuria).
 Does pus in urine indicate cancer?
Looking at the above table, you will notice that (Urinary tract neoplasms) are among the causes of sterile pyuria (pus in urine with negative bacterial culture).
However, pus in urine doesn’t mean you have cancer. More than 99.9% of the causes of pus in urine are due to infections and stones unrelated to the tumor.
Pus is primarily a sign of infection of the urinary tract. So, no need to worry about cancer when you have pus in your urine unless:
- The pus is unexplained by UTI or any of the causes listed above.
- You have risk factors for developing cancers, such as bladder cancer (see later).
- You have other symptoms and signs consistent with bladder cancer (such as painless blood in urine, weight loss, etc.).
Moreover, when pyuria occurs due to cancer in the urinary tract (such as bladder cancer), it is often mild and typically detectable by urine analysis only (and the urine appears normal).
In conclusion, No need to worry about cancer if you have pus in your urine. The odds of cancer being the cause of such a condition is very low.
 When to worry about cancer if you have pus in your urine.
Pus in urine is suspicious for cancer when you have no other reason explaining the pus (such as infection), and you have other risk factors & symptoms of urinary tract cancer (such as bladder or kidney cancer).
The most common urinary tract cancers that can be associated with pus in urine include:
- Urinary bladder cancer (The most common urinary tract cancer).
- Kidney cancer.
- Prostate cancer.
- Ureteric cancer.
Below, we will explain the risk factors, symptoms, and signs of the most common urinary tract cancer (bladder cancer).
Suspect cancer as a cause of pus in urine when the pus is associated with symptoms and risk factors listed below.
[A] Risk factors of cancer.
You should consider bladder cancer as a cause of blood urine, especially if you have risk factors such as:
- Cigarette smoking.
- Females are generally less commonly affected by bladder cancer than men.
- Being older (more than 50).
- Opium use.
- Occupation exposure to carcinogens as with metal workers, painters, rubber industry workers, leather workers, textile and electrical workers, miners, cement workers, transport operators, excavating-machine operators, and jobs that involve the manufacture of carpets, paints, plastics, and industrial chemicals.
- Genetics also plays a role.
- Schistosomiasis infection (common in north Africa and Japan).
For kidney cancer, the risk factors are nearly the same, plus obesity, older age, hypertension, and a family history of kidney cancer.
[B] Symptoms of urinary tract cancer.
- Early bladder cancer may present with irritative symptoms such as painful urination (dysuria), the urgency to urinate, or frequent urination.
- Typically, bladder cancer causes painless bleeding in the urine (intermittent attacks of bloody urine or blood on tissue after urination).
- Blood is often present throughout the urination, but minor bleeding also occurs.
- Bladder pain or pressure in the lower abdomen (typically, no pain is present in patients with bladder cancer).
- Dysuria or pain after the end of urination.
- Signs of metastasis may also exist, such as bone pain, abdominal pain, liver pain, headache, or blurring of vision.
- Weight loss, anorexia, and other systemic symptoms may also present.
The symptoms of kidney cancer are the same, except the pain is often in the flanks. 25% of the cases of kidney cancers are completely asymptomatic.
 Can long-standing pus in urine cause cancer?
Long-standing pus in the urine itself is not a direct cause of cancer. However, suppose the underlying cause of the pus in urine is left untreated for an extended period of time. In that case, it may increase the risk of developing certain types of urinary tract cancers, such as bladder cancer.
For instance, patients with untreated bladder stones with recurrent or persistent UTI and pus in urine for years are at higher risk of bladder cancer (reference).
Therefore, it is important to address any persistent symptoms of pyuria and seek medical attention promptly to prevent potential complications.