Pyelonephritis: Symptoms, Causes, Diagnosis, Treatment, Prevention, Complications and Epidemiology

It is inflammation of the kidney, usually due to a bacterial infection. The most common symptoms include fever and flank tenderness.

Other symptoms may include nausea, burning with urination, and frequent urination. Complications can consist of pus around the kidney, sepsis, or kidney failure.

It is usually due to a bacterial infection, most often Escherichia coli. Risk factors include sexual intercourse, previous urinary tract infections, diabetes, structural urinary tract problems, and use of spermicides.

The mechanism of infection generally extends through the urinary tract. Less often, the condition occurs through the bloodstream.

Diagnosis is usually based on symptoms and is supported by urinalysis. If there is no improvement with treatment, medical imaging may be recommended.

Pyelonephritis can be prevented by urinating after having sex and drinking enough fluids. Once present, it is usually treated with antibiotics, such as ciprofloxacin or ceftriaxone.

Those with a severe illness may need treatment in the hospital. Surgery may be required in those with specific structural urinary tract problems or kidney stones.


Pyelonephritis is common. Approximately 1 to 2 per 1,000 women is affected per year and just under 0.5 per 1,000 men. Young adult women are the most affected, followed by the youngest and the oldest.

With treatment, the results are generally good in young adults. Among people over 65, the risk of death is about 40%.

Signs and symptoms of pyelonephritis

The signs and symptoms of acute pyelonephritis usually develop rapidly over a few hours to a day. It can cause a high fever, painful urination, and abdominal pain that radiates along the flank to the rear. There is often associated vomiting.

Chronic pyelonephritis causes persistent flank or abdominal pain, signs of infection (fever, involuntary weight loss, malaise, decreased appetite), lower urinary tract symptoms, and blood in the urine.

Chronic pyelonephritis can cause a fever of unknown origin. In addition, proteins related to inflammation can accumulate in the organs and cause the condition of AA amyloidosis. Physical examination may reveal fever and tenderness at the costovertebral angle on the affected side.

Pyelonephritis that has progressed to urosepsis may be accompanied by signs of septic shock, including rapid breathing, decreased blood pressure, chills, and occasionally delirium.


Most cases of “community-acquired” pyelonephritis are due to intestinal organisms entering the urinary tract. Common organisms are E. coli (70-80%) and Enterococcus faecalis.

Hospital-acquired infections can be caused by coliform bacteria and enterococci, as well as other organisms rare in the community (e.g., pseudomonas aeruginosa and various species of Klebsiella).

Most cases of pyelonephritis begin as lower urinary tract infections, primarily cystitis, and prostatitis. E. coli can invade the superficial umbrella cells of the bladder to form intracellular bacterial communities (IBCs), which can mature into biofilms.

These biofilm-producing E. coli are resistant to antibiotic therapy and immune system responses and present a possible explanation for recurrent urinary tract infections, including pyelonephritis. The risk increases in the following situations:

Mechanical: any structural abnormality in the urinary tract such as:

  • Vesicoureteral reflux (urine from the bladder flowing into the ureter).
  • Kidney stones
  • Catheterization of the urinary tract.
  • Ureteral stents or drainage procedures (e.g., nephrostomy).
  • Pregnancy.
  • Neurogenic bladder; for example, due to spinal cord damage.
  • Spina bifida or multiple sclerosis.
  • Prostate disease (for example, benign prostatic hyperplasia) in men.

Constitutional: diabetes mellitus, immunocompromised states.

Behavior: change in a sexual partner in the last year, spermicide use.

Positive family history (close relatives with frequent urinary tract infections).

Diagnosis of pyelonephritis

Laboratory exam

Urinalysis may show signs of a urinary tract infection. Specifically, the presence of nitrite and white blood cells in a urine test strip in patients with typical symptoms is sufficient for diagnosing pyelonephritis, and they are an indication for empirical treatment.

Blood tests, such as a complete blood count, can show neutrophilia. Microbiological urine cultures, with or without blood cultures and antibiotic sensitivity tests, help establish a formal diagnosis and are considered mandatory.

Imaging studies

Suppose a kidney stone is suspected (for example, due to characteristic colicky pain or a disproportionate amount of blood in the urine). In that case, the kidneys, ureters, and bladder x-ray (KUB film) can help identify stones. Radiopaque.

A non-contrast helical computed tomography scan with 5-millimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis.

All stones are detectable on CT scans, except scarce rocks made up of specific drug residues in the urine.

In patients with recurrent ascending urinary tract infections, excluding an anatomical abnormality, such as vesicoureteral reflux or polycystic kidney disease, may be necessary.

Investigations used in this setting include renal ultrasound or voiding cystourethrography. Computed tomography or renal ultrasound is helpful in the diagnosis of xanthogranulomatous pyelonephritis; Serial imaging can be beneficial in differentiating this condition from kidney cancer.

The ultrasound findings that indicate pyelonephritis are kidney enlargement, edema in the renal sinus or parenchyma, bleeding, loss of corticomedullary differentiation, abscess formation, or areas of poor blood flow on Doppler ultrasound.

However, ultrasound findings are seen in only 20% to 24% of people with pyelonephritis.

A dimercaptosuccinic acid (DMSA) scan is a radionuclide scan that uses dimercaptosuccinic acid to assess kidney morphology. It is now the most reliable test for the diagnosis of acute pyelonephritis.


Pyelonephritis aguda

Acute pyelonephritis is a localized exudative purulent inflammation of the renal pelvis (collecting system) and kidney.

The renal parenchyma occurs in interstitial abscesses (suppurative necrosis), which consists of purulent exudate (pus): neutrophils, fibrin, cellular debris, and central colonies of germ (hematoxylininophils).

The tubules are damaged by exudate and may contain neutrophilic casts. In the early stages, the glomerulus and vessels are normal. Gross pathology often reveals pathognomonic radiations of bleeding and suppuration through the renal pelvis to the renal cortex.

Chronic pyelonephritis

Chronic pyelonephritis involves recurrent kidney infections and can lead to scarring of the kidney parenchyma and impaired function, especially in obstruction.

In severe cases of pyelonephritis, a perirenal abscess (infection around the kidney) and pyonephrosis may develop.

Pyelonephritis xanthogranulomatous

Xanthogranulomatous pyelonephritis is an unusual form of chronic pyelonephritis characterized by the formation of granulomatous abscesses, severe renal destruction, and a clinical picture that may resemble renal cell carcinoma and other inflammatory diseases of the renal parenchyma.

Most of those affected have recurrent fever and urosepsis, anemia, and a painful kidney mass. Other common manifestations include kidney stones and loss of function of the affected kidney. Bacterial cultures of kidney tissue are almost always positive.

Microscopically, there are lipid-laden granulomas and macrophages (hence the term xantho-, which means yellow in ancient Greek). It is found in approximately 20% of surgical pyelonephritis specimens.

Pyelonephritis treatment

A urine culture and antibiotic sensitivity test are performed in people suspected of pyelonephritis, so the therapy can eventually be tailored based on the infecting organism.

Since most cases of pyelonephritis are due to bacterial infections, antibiotics are the mainstay of treatment.

The choice of antibiotic depends on the species and antibiotic sensitivity profile of the infecting organism and may include fluoroquinolones, cephalosporins, aminoglycosides, or trimethoprim/sulfamethoxazole, either alone or in combination.


Antibiotics are the first course of action against acute pyelonephritis. However, the type of antibiotic your doctor chooses depends on whether the bacteria can be identified or not. If not, a broad-spectrum antibiotic is used.

In people who do not require hospitalization and live in an area with a low prevalence of antibiotic-resistant bacteria, oral fluoroquinolone, such as ciprofloxacin or levofloxacin, is an appropriate initial option for treatment.

In areas with a higher prevalence of resistance to fluoroquinolones, it is helpful to start treatment with a single intravenous dose of a long-acting antibiotic, such as ceftriaxone or aminoglycoside, then continue treatment with a fluoroquinolone.

Oral trimethoprim/sulfamethoxazole is an appropriate option for therapy if the bacteria are known to be susceptible. If trimethoprim/sulfamethoxazole is used when susceptibility is unknown, it is helpful to initiate treatment with a single intravenous dose of a long-acting antibiotic such as ceftriaxone or an aminoglycoside.

Oral beta-lactam antibiotics are less effective than other available agents for the treatment of pyelonephritis. An improvement is expected in 48 to 72 hours.

Although the medications can cure the infection within 2 to 3 days, the drug must be taken for the entire prescription period (usually 10 to 14 days). This is true even if you feel better.


In some cases, drug therapy is ineffective. For severe kidney infections, your doctor may admit you to the hospital.

People with acute pyelonephritis, accompanied by high fever and leukocytosis, are typically admitted to the hospital for intravenous hydration and treatment with intravenous antibiotics.

Treatment usually begins with an intravenous fluoroquinolone, aminoglycoside, extended-spectrum penicillin, cephalosporin, or a carbapenem.

Combination antibiotic therapy is often used in such situations. The treatment regimen is selected based on local resistance data and the susceptibility profile of the specific infecting organism.

The serial white blood cell count and temperature are closely monitored during antibiotic treatment.

Typically, intravenous antibiotics are continued until the person has no fever for at least 24 to 48 hours. Antibiotics can be given by mouth for two weeks of treatment duration.

Intravenous fluids can be administered to compensate for reduced oral intake, insensitive losses (due to elevated temperature), vasodilation, and optimized urine output.

A percutaneous nephrostomy or ureteral stent placement may be indicated to relieve the stone obstruction.

Children with acute pyelonephritis can be effectively treated with oral antibiotics (cefixime, ceftibuten, and amoxicillin / clavulanic acid) or with short courses (2 to 4 days) of intravenous followed by oral therapy.

If intravenous therapy is chosen, single daily dosing with aminoglycosides is safe and effective. The length of your stay depends on the severity of your condition and how well you respond to treatment.

Recurrent kidney infections can be the result of an underlying medical problem. Treatment for xanthogranulomatous pyelonephritis includes antibiotics and surgery.

In those cases, surgery may be required to remove any obstruction or correct any structural problems in the kidneys. Surgery may also be necessary to drain an abscess that does not respond to antibiotics.

In cases of severe infection, a nephrectomy may be necessary. In this procedure, a surgeon removes part of the kidney.

Removing the kidney is the best surgical treatment in most cases, although polar resection (partial nephrectomy) has been adequate for some people with localized disease.

Watchful waiting with serial images may be appropriate in exceptional circumstances.


Pyelonephritis can be a severe disease. Contact your doctor as soon as you suspect you have pyelonephritis or a urinary tract infection. This condition requires immediate medical attention, so the sooner treatment begins, the better.

Further investigation may identify an underlying abnormality in people who experience recurrent urinary tract infections. Occasionally, surgical intervention is necessary to reduce the likelihood of recurrence.

Some studies suggest long-term preventive treatment with antibiotics if no abnormalities are identified, either daily or after sexual activity.

In children at risk for recurrent urinary tract infections, not enough studies have concluded that long-term antibiotic prescribing has a positive net benefit.

Drinking cranberry juice doesn’t seem to provide much, if not benefit, in decreasing urinary tract infections.

Prevention tips

Drink plenty of fluids to increase urination and remove bacteria from the urethra. Urinate after sex to help kill bacteria. Wipe from front to back.

Avoid using products that can irritate the urethra, such as douches or feminine sprays.

Possible complications of pyelonephritis

A possible complication of acute pyelonephritis is chronic kidney disease. If the infection continues, the kidneys can be permanently damaged. Although rare, it is also possible for the condition to enter the bloodstream. This can lead to a life-threatening infection called sepsis.

Other complications include:

  • Recurrent kidney infections.
  • The infection spreads to areas around the kidneys.
  • Acute renal failure.
  • Kidney abscess.


Approximately 12-13 cases per year per 10,000 inhabitants in women who receive outpatient treatment and 3-4 cases requiring admission. In men, 2-3 cases per 10,000 are treated as outpatients and 1-cases / 10,000 require admission.

Young women are most often affected, probably reflecting sexual activity in that age group. Babies and the elderly are also at higher risk, reflecting anatomical changes and hormonal status.

Xanthogranulomatous pyelonephritis is more common in middle-aged women. It can present somewhat differently in children, in whom it can be confused with Wilms tumor.


The term is from the Greek πύελο | ς pýelo | s, “basin” + νεφρ | ός nepʰrós, “kidney” + suffix -itis suggesting “inflammation.”

A similar term is “pyelitis,” which means inflammation of the renal pelvis and calyces. In other words, pyelitis, along with nephritis, is collectively known as pyelonephritis.

Pyelonephritis in pregnant women

Pregnancy causes many temporary changes in the body, including physiological changes in the urinary tract. Increased progesterone and increased pressure on the ureters can increase the risk of pyelonephritis.

Pyelonephritis in pregnant women usually requires hospital admission. It can threaten the lives of both mother and baby. It can also increase the risk of preterm labor. Pregnant women are treated with beta-lactam antibiotics for at least 24 hours until their symptoms improve.

A urine culture should be done between 12 and 16 weeks of pregnancy to prevent pyelonephritis in pregnant women. A urinary tract infection with no symptoms can lead to the development of pyelonephritis. Early detection of urinary tract infections can prevent kidney infections.

Pyelonephritis in children

According to the American Urological Association, in the United States, more than one million trips to the pediatrician are made each year for pediatric urinary tract infections. Girls are at higher risk if they are over one year old. Boys are at greater risk if under one, especially if they are not circumcised.

Children with urinary tract infections often have fever, pain, and urinary tract-related symptoms. A doctor must address these symptoms immediately before they can develop into pyelonephritis.

Most children can be treated with oral antibiotics on an outpatient basis.