Pyelonephritis is a type of urinary tract infection (UTI) that primarily affects the kidneys. Often referred to simply as a kidney infection, it’s a more severe condition than lower urinary tract infections, such as cystitis. If left untreated, pyelonephritis can lead to serious health complications, making it crucial to understand its causes, symptoms, diagnosis, treatment options, and preventive measures.

What is Pyelonephritis?

Pyelonephritis is an infection and inflammation of the kidney and the upper urinary tract, usually caused by bacteria that have ascended from the bladder or have been carried to the kidneys from the bloodstream. The most common causative agent is Escherichia coli (E. coli), but other bacteria and, in rare cases, viruses or fungi may also be responsible.

Causes and Risk Factors

The primary cause of pyelonephritis is bacterial infection, particularly with E. coli. However, several risk factors increase the likelihood of developing this condition:

  • Sexual Activity: Especially frequent, vigorous, or with new partners, can introduce bacteria into the urinary tract.
  • Female Anatomy: Women are more prone to UTIs and subsequently pyelonephritis due to their shorter urethra, which allows bacteria easy access to the bladder and kidneys.
  • Urinary Obstruction: Kidney stones, enlarged prostate, or any structural abnormalities in the urinary tract can block the flow of urine, making infection more likely.
  • Catheter Use: Long-term use of urinary catheters significantly increases infection risks due to bacteria entry along the catheter.
  • Compromised Immune Systems: Individuals with weakened immune systems are more susceptible to infections, including pyelonephritis.
  • Pregnancy: Hormonal changes and urinary stasis during pregnancy can increase the risk of UTIs and kidney infections.

Symptoms of Pyelonephritis

Symptoms of pyelonephritis can vary but typically include:

  • High Fever and Chills
  • Back, Side (flank) or Groin Pain
  • Abdominal Pain
  • Frequent, Painful Urination
  • Cloudy, Dark, Bloody, or Foul-Smelling Urine
  • Nausea and Vomiting
  • General Malaise and Fatigue

In older adults and young children, symptoms might be less specific and can include lethargy, irritability, inappetence, or low-grade fever.


Diagnosis of pyelonephritis typically involves a combination of clinical evaluation and diagnostic tests:

  • Medical History and Physical Exam: To check for pain in the kidney area.
  • Urinalysis: To detect signs of infection and inflammation such as bacteria, white blood cells, or blood.
  • Urine Culture: To identify the specific type of bacteria causing the infection, which helps in selecting the most effective antibiotic.
  • Blood Tests: To assess kidney function and detect signs of infection in the bloodstream.
  • Imaging Tests: Such as ultrasounds or CT scans, especially if recurrent infections are a concern or there are unusual symptoms.

Treatment Options

Treatment for pyelonephritis generally involves antibiotics, which are selected based on the type of bacteria identified in urine cultures. Treatment duration can vary:

  • Oral Antibiotics: Typically prescribed for 7-14 days, but the length and type of antibiotic may differ based on the severity of the infection and patient history.
  • IV Antibiotics: Used in more severe cases or when nausea and vomiting prevent oral medications from being effective.
  • Pain Relievers: To manage fever and relieve pain.

Hospitalization might be necessary for severe infections, especially for those who are pregnant, severely ill, or have compromised immune systems.


Preventive measures can reduce the risk of pyelonephritis:

  • Hydration: Drinking plenty of fluids helps flush bacteria from the urinary tract.
  • Urinary Hygiene: Women should wipe from front to back after toileting to prevent bacterial transfer.
  • Frequent Urination: Urinating frequently and fully emptying the bladder when urinating can help flush out bacteria.
  • Avoiding Irritants: Such as harsh soaps or bubble baths, which can irritate the urethra.


Pyelonephritis is a severe type of urinary tract infection that requires prompt and effective treatment to prevent complications. Understanding the symptoms, risks, and treatment options available is vital for managing and preventing this painful and potentially dangerous condition.

Always consult a healthcare provider if you suspect you may have Pyelonephritis, as timely medical intervention is crucial.