Pyuria refers to the presence of pus in the urine. It is usually a sign of a bacterial infection of the urinary tract. What are the risk factors for pyuria? What are the causes ? How to detect and treat it?

The term pyuria comes from the Greek words puon which means pus and ouron which means urine. Pyuria therefore refers to the presence of pus in the urine. It is not a disease but a symptom. 

It is characterized by:

• cloudy urine;
• smelly urine;
• discolored urine;
• the presence in the urine of altered leukocytes (white blood cells) in large quantities (more than one million per milliliter).

The origin of the pus can be found anywhere in the urinary tract, from the calyxes to the anterior urethra. It may even happen that the origin is extra-urinary.

Pyuria indicates an infection of the excretory urinary tract such as:

• pyelonephritis (an infection that affects the kidney) with lower back pain;
• cystitis (infection of the bladder) with painful urination;
• urethritis (inflammation of the urethra);
• acute prostatitis (inflammation of the prostate);
• etc.

Pyuria due to a urinary tract infection is common in people of all ages. However, it is more common in women than in men. The overall prevalence of asymptomatic infection is estimated at 3,5%. Pregnant women are also more likely to be affected, with 4-10% of women having pyuria. Pyuria can also be present in people with sepsis (generalized infection) or pneumonia (mainly in the elderly).

Diseases or situations that favor the multiplication of the germs responsible for the infection, such as the bacterium Escherichia coli, constitute risk factors. They include:

• diabetes ;
• the SIDA;
• history of urinary tract infection;
• urinary retention (stasis) of the upper (hydronephrosis) or lower apparatus (post-voiding residue);
• changes in the urothelium due to foreign bodies, tumors, wounds, scars;
• foreign bodies such as stones or a urinary catheter;
• suppuration of the parenchyma surrounding the excretory pathway (kidney, prostate, etc.);
• nearby suppurations open in the excretory tract: colic, adnexal (uterine tubes), rectal;
• low socio-economic status.

When no germ is detected by cytobacteriological examination of the urine, it is called aseptic pyuria or sterile pyuria. It is characterized by urine that contains leukocytes, but which appears sterile when cultured. This may be due to:

• a side effect of certain drugs such as paracetamol;
• infection not fully treated with antibiotics;
• a sexually transmitted and blood-borne infection (STBBI) such as gonorrhea;
• Kawasaki disease;
• genitourinary tuberculosis;
• cancer ;
• renal pathologies.

The prevalence of sterile pyuria is 13,9% in women and 2,6% in men. It can be greater than 20% in hospitalized people.

There are no distinct symptoms of pyuria and the symptoms reported are usually related to an underlying medical condition that is causing the pyuria. Since this is usually caused by a bacterial infection of the urinary tract, it can be associated with other symptoms such as:

• frequent urination;
• painful urination;
• abdominal or lower back pain.

In more serious infections, there may also be signs of:

• fever: if it is greater than 38,5 °, it may be a sign of parenchymal involvement such as the kidney in men and women, and the prostate and epididymis in men;
• chills;
• nausea;
• vomiting;
• renal colic;
• unilateral low back pain.

The presence of pus in the urine can be detected by analyzing a urine sample, which is sent to a laboratory for microscopic examination and chemical analysis. Additional diagnostic tests may be needed to determine the cause of pyuria and guide decisions towards optimal treatment. It can be:

• an intravenous pyelography, a technique used to examine the kidneys, the ureters, that is to say the ducts which connect the kidneys to the bladder, and the bladder;
• a CT scan;
• magnetic resonance imaging (MRI);
• or an ultrasound of the abdominal area.

The recommended treatment for pyuria depends on the underlying cause of the condition. If there is no associated infection and the patient is asymptomatic, treatment may not be necessary.

In case of infection, several antibiotics may be indicated to eradicate the bacteria that have colonized the urinary tract:

• lévofloxacine ;
• ciprofloxacin;
• minocycline ;
• ampicillin;
• amoxicilline/clavulanate ;
• erythromycin;
• doxycycline ;
• norfloxacin.