Pyelonephritis is a bacterial infection of one or both kidneys. This is an acute form of urinary tract infection: the infection travels up the urinary tract to the kidneys. There are several symptoms to look out for: burning when urinating, pain in the lower abdomen, frequent and urgent urination indicates a urinary tract infection. However, sometimes these symptoms, which constitute the “first stage” towards pyelonephritis, are little or not felt by the patient.

If the urinary tract infection is not taken care of, or if it is treated too late, it can reach the kidneys: this is called pyelonephritis. Symptoms include fever, lower back and/or abdominal pain, chills, a feeling of nausea,
vomiting.

The bacterium Escherichia Coli is involved in 70 to 95% of cases of infection, Staphylococcus saprophyticus and other enterobacteria appear in 5 to 20% of cases. While the bacteria causing pyelonephritis can vary, the causes of infection also vary depending on the type of patient.

Causes of pyelonephritis

The causes of pyelonephritis vary, depending on the age and gender of the patient. Cases of pyelonephritis are up to 30 times more common in young women than in men.

The reason for this discrepancy is anatomy; a woman’s urethra is on average 2 cm long, and a man’s urethra is 16 cm. The infection, therefore, escalates more easily in women than in men. Some profiles are more at risk than others: People with diabetes or a weakened immune system are more likely to get acute pyelonephritis, as are pregnant women.

Causes of pyelonephritis in men

Although much rarer in men than in women, pyelonephritis in men is considered serious from the start. If the infection is strong enough to travel up the urethra and then up the ureters to the kidneys, it is particularly aggressive. Pyelonephritis is more common in men over 40 because it is often linked to an infection of the prostate. This is because the urethra passes through the prostate before reaching the bladder. If the prostate is infected, the infection can easily travel to the kidneys. An infection of the prostate, called prostatitis, can occur after a urinary catheter or endoscopic examination of the bladder, after a bladder infection, or an adenoma of the prostate.

In younger patients, the cause of pyelonephritis is often a chlamydial infection. The bacterium that causes chlamydia is sexually transmitted, and sometimes takes years to appear and causes symptoms and complications, including prostatitis, and subsequently, pyelonephritis.

Finally, in general, all obstacles to the flow of urine are potential causes of pyelonephritis in men: the presence of stones, bladder neck disease, compression of the urinary tract, etc.

Causes of pyelonephritis in babies

Pyelonephritis in babies under 2 years old is relatively common. It is often identified following a fever peak between 39 and 40 degrees centigrade when the child does not present any pathology or childhood illness.

The cause of pyelonephritis in babies is, in the majority of cases, a malformation of the urinary tract. This malformation causes vesicourethral reflux, which means that urine goes back up into the bladder and then into the kidneys, creating an infection. Pyelonephritis in a baby usually goes away on its own, after two years, after the baby’s urinary system has developed and the malformation has naturally corrected. In rare cases, the problem persists. It is then necessary to go through a surgical intervention to correct the malformation.

Causes of recurrent pyelonephritis or chronic pyelonephritis

In at-risk individuals, pyelonephritis can be recurrent, or even chronic. In some cases, it can cause bacteria to be released into the bloodstream, leading to infection in the opposite kidney or other areas of the body. Very rarely, chronic pyelonephritis can cause severe kidney damage and lead to chronic kidney disease. The cause of chronic pyelonephritis is often found in underlying conditions: large and persistent kidney stones, reflux of urine into the bladder, obstruction of the urinary tract, deformation of the kidney tissue.

Symptoms of pyelonephritis

Acute pyelonephritis is often accompanied by a urinary tract infection. It can thus manifest itself by:

• burning during urination;
• frequent urge to urinate (pollakiuria);
• smelly or cloudy urine with pus (pyuria)
• the presence of blood in the urine (hematuria).

Unilateral pain in the lumbar area is often observed. It can spread to the genitals. Nevertheless, the pain is sometimes absent, especially in cases of chronic pyelonephritis.

A fever is a common sign of infection. However, sometimes pyelonephritis can be observed without a fever, especially in chronic pyelonephritis.

Treatments of pyelonephritis

Treatment of pyelonephritis will be tailored on a case-by-case basis, depending on the patient’s profile and the severity of the infection. For pyelonephritis of bacterial origin, antibiotic treatment is indicated. Urine tests are done to identify the bacteria responsible and adapt the antibiotic as needed.

In most cases, a hospital stay is necessary in order to find the causative bacteria, administer the corresponding antibiotic, and assess the potential impact on the bladder and kidneys. For simple pyelonephritis, taking the antibiotic for 7-10 days is often sufficient.

For severe pyelonephritis, treatment over 15 days may be necessary. If a kidney malformation is detected by ultrasound or scintigraphy, further examinations will be performed to prevent pyelonephritis from becoming chronic.

For people with obstruction of the urinary tract (stones, polyp, malformation), surgery may be necessary.