Pyelonephritis: causes, symptoms, diagnosis and treatment

By Cristiano Antonino On Jun 14, 2023

Pyelonephritis is an inflammatory disease of the kidney and renal pelvis that can be acute or chronic. The disease is often associated with a more or less extensive infection of the organ parenchyma

In fact, among the most evident symptoms there are fever, lumbar pain and lower urinary tract disorders.

Pyelonephritis: what is it?

Urinary tract infections can also affect the kidney and renal pelvis. Infections that affect this district are called pyelonephritis.

They are often caused by viruses or bacteria that infect the lower urinary tract, in particular the bladder (we are therefore talking about cystitis), and then rise, extending to the upper urinary tract and affecting one or both kidneys, despite the fact that the human body has natural barriers of defense that oppose the rise of the infectious process.

Pyelonephritis can also be caused by surgery, as a result of bacteria entering during the procedure.

Finally, pathogens can reach the kidneys via the blood.

How does the body defend itself?

Urine flows in only one direction, from the bladder towards the kidneys, thus favoring the expulsion of viruses or bacteria which are eliminated through urination.

However, this one-way flow is sometimes not enough to prevent pathologies.

The microorganisms manage to infect the bladder and from there spread to the kidneys.

Kidney infections can be very painful and lead to serious complications.

For this reason, as soon as certain symptoms are felt, such as frequent urination with traces of blood, abdominal pain that radiates towards the back, fever and nausea, it is essential to contact your doctor.

Pyelonephritis: symptoms

Pyelonephritis has quite obvious symptoms. In fact, from the onset of the infection, the signs appear rather quickly, appearing already in the first hours.

Affected patients experience fever and chills.

More generally, there is a widespread malaise with tiredness, decreased appetite and muscle weakness.

People with pyelonephritis have severe pain involving the groin, side, and back.

Urine is cloudy, contaminated with blood, and foul-smelling, while urination is frequent and particularly painful.

Vomiting and nausea also often occur.

The signs that you have a widespread infection in the kidneys can vary with age.

In children under the age of two, fever is often the only symptom.

On the other hand, patients over the age of 65 may experience symptoms that are not typical and involve the cognitive sphere.

In these cases pyelonephritis causes hallucinations, confusion and slurred speech.

Pyelonephritis: when to see a doctor?

When you feel the first symptoms of pyelonephritis it is essential to contact your doctor.

In fact, the infection can quickly evolve into sepsis, a more serious condition that can lead to death.

Symptoms of sepsis are rapid breathing and pulse, rash, confusion, chills, and fever.

When the infection becomes chronic and lasts over time it can also cause permanent and debilitating damage to kidney function.

Pyelonephritis: causes

Pyelonephritis often has a bacterial origin.

The pathogens that cause infection can spread in several ways.

The most common method is the ascending route.

In this case the microorganisms ascend from the genital area, through the urethra, reaching the bladder and, finally, the kidneys.

In women this process is favored by the shorter length of the urethra and the possibility of contamination of the vaginal mucosa during sexual intercourse.

In men, however, a risk factor is represented by prostatitis.

Kidney infection is more common in patients with catheters.

In fact, contamination can occur during placement or manipulation of the catheter.

In this way, the pathogens easily ascend from the bladder.

Pyelonephritis can also arise from an infection of the blood that reaches the kidneys.

This condition occurs when the patient is suffering from septicemia, i.e. the presence of bacteria in the blood.

Contamination of this type is called hematogenous.

The pathology can also originate via the lymphatic route, when pathogens spread through the lymphatic vessels.

The microorganisms that cause pyelonephritis are the same ones that cause infections of the genital tract, gastrointestinal tract and urinary tract.

In particular, we speak of Escherichia coli, Klebsiella spp., Proteus spp. and Enterococcus spp.

These pathogens are part of the faecal flora and often manage to reach the bladder despite the presence of peristalsis, i.e. the contraction and distension movements of the urinary tract that protect against infections.

At the origin of pyelonephritis we can find, less frequently, mycobacteria, yeasts, fungi and Corynebacterium urealyticum.

Pyelonephritis: risk factors

There are certain factors that predispose patients to the development of pyelonephritis.

Among the most critical conditions are those that lead to urine stagnation such as when there are stones or other types of obstruction (this is the case of pathologies such as prostatic hypertrophy or cancer).

People who are immunosuppressed or have peripheral neuropathy, such as a spinal cord lesion, are more at risk.

Pyelonephritis: diagnosis

The diagnosis of pyelonephritis is made after a thorough history, a complete physical examination and some specific tests.

Doctors usually evaluate the patient’s general health and factors that could increase the risk of a kidney infection.

The various symptoms are then evaluated.

Digital rectal examination (DRE) is often performed in male patients.

During the exam, the doctor has the person lie on their side, with their knees up to their chest.

He then introduces a gloved finger lubricated with an anesthetic gel into the anus in order to assess the size of the prostate which prevents complete emptying of the bladder.

Other follow-up tests such as ultrasound, CT scans, or magnetic resonance imaging (MRI) are also needed to diagnose pyelonephritis.

These procedures are done in a hospital or diagnostic center and do not require anesthesia.

A urine test and urine culture are also usually done.

The collected sample is analyzed in the laboratory to identify the presence of bacteria and leukocytes, cells produced by the body to fight an infection.

Urine culture allows you to discover the type of bacterium that caused the infection and allows you to set up the best therapy.

Pyelonephritis: cure

Pyelonephritis is treated with antibiotic therapy.

If the treatment is prescribed promptly, healing can be achieved without any consequences.

The treatment allows you to eliminate the bacteria present in the urine by taking specific antibiotic cycles.

Medicines often also have a protective function and help prevent new infections. In some cases, surgery may be required.

The specialist can then resort to urethroscopy, an operation usually used to treat stones, urothelial neoformations and strictures, or to nephrectomy which involves the partial or total removal of the kidney.

Pyelonephritis: complications

In rare cases, pyelonephritis can lead to serious complications.

This happens when kidney infection occurs in people who already have kidney disease with another cause, who have a problem with the structure of the urinary tract, or who have a history of recurrent episodes of kidney infection.

Acute pyelonephritis

Acute pyelonephritis is a sudden, onset infection of the kidney that enlarges the organ and can damage it permanently.

It is a very rare form of this pathology, more frequent in children and in subjects with urinary obstructions.

The pathology is identified through a urine test and an ultrasound, to evaluate the presence of cysts or tumors that may obstruct the urinary tract.

Symptoms of acute pyelonephritis usually appear within the first two days after infection.

The most common are high fever, pain in the back, abdomen and sides, accompanied by blood in the urine, burning when urinating, chills and nausea.

The infection usually starts in the lower urinary tract.

The bacteria can enter the body through the urethra and spread up to the bladder, then reaching the kidneys.

Most often, bacteria such as E.coli cause the infection.

In other cases, a serious infection in the bloodstream can spread, leading to acute pyelonephritis.

Chronic pyelonephritis

Chronic pyelonephritis is a long-lasting infection of the kidney that occurs in people who have severe anatomical abnormalities.

Symptoms are often subtle and include flank pain, fever, and general malaise.

Diagnosis is made by urinalysis, urine culture, and radiological examinations.

Therapy consists of antibiotic treatment and correction of the structural disorder.

Chronic pyelonephritis mainly affects patients who have a predisposition to urinary reflux.

The disease is most often diagnosed in the presence of recurrent acute pyelonephritis.

Chronic pyelonephritis is treated with correction of the obstruction, long-term antibiotic therapy, and in rare cases with nephrectomy which may or may not be followed by a kidney transplant.

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