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What is acute pyelonephritis? Causes, Symptoms and Treatments

Home / What is acute pyelonephritis? Causes, Symptoms and Treatments

What is acute pyelonephritis? Causes, Symptoms and Treatments

In general, pyelonephritis is a condition of infection in the kidneys. The main focus of this blog will be acute pyelonephritis. We’ll see what this condition is, what causes it, some of the pathophysiology behind the reason it occurs, symptoms and diagnosis of pyelonephritis, and lastly its treatment.

What is acute pyelonephritis?

To understand the term pyelonephritis we must break it down. ‘Pyelo’ means pelvis, ‘nephr’ refers to the kidney. So ‘pyelonephr’ refers to the area of the renal pelvis which is the funnel-like structure inside the kidney and which has the functionality to drain urine into the ureter. As ‘itis’ refers to inflammation, pyelonephritis means inflammation of a segment of the kidney. In acute pyelonephritis, the kidney inflamed is developed relatively quickly and the pathogen contributing to this inflammation is usually bacteria. As inflammation is a symptom of infection, pyelonephritis is actually a type of upper urinary tract infection.

What causes acute pyelonephritis?

Acute pyelonephritis is most often caused by ascending infection of the urinary tract. The bacteria first start by colonizing the urethra and bladder, thus causing lower urinary tract infections. After this colonization, bacteria make their way up to the kidney. This is the reason that the factors causing upper UTI (pyelonephritis) are the same as the factors causing lower UTI. Some of these factors are as follows:

  • Female gender
  • Sexual intercourse
  • Indwelling catheters
  • Diabetes mellitus
  • Urinary tract obstruction

One single major factor that increases the risk of occurrence of upper UTI from the spread of lower UTI upwards is Vesicoureteral reflux. In this condition, the backward movement of urine is not restricted and therefore urine can move up the urinary tract. This is caused by the failure of the Vesicoureteral valve.

Most common pathogens causing pyelonephritis:

  • E. coli
  • Proteus
  • Enterobacter

The less common reason that causes acute pyelonephritis is hematogenous infection. Pyelonephritis due to this reason is usually a consequence of:

  • Septicemiamia
  • Endocarditis

Pathophysiology of pyelonephritis

Acute pyelonephritis affects just one kidney in most cases. This means it is a unilateral condition. At the start of the attack, the bacteria adhere to the renal epithelium of the tubules. This triggers an immune response causing inflammation. Chemokines, which are the protein secreted by immune cells, attract neutrophils ( a type of WBC) to the renal interstitium. These neutrophils upon infiltrating and dying off, move through the urinary tract and are expelled through the urine. This is the reason that people with acute pyelonephritis often have white blood cells in their urine.

Symptoms of acute pyelonephritis

Pyelonephritis symptoms are most often the same as those of the lower urinary tract infection but some systemic symptoms that often distinguish pyelonephritis from the lower urinary tract infection are as follows:

  • Leukocytosis: Increased WBCs in blood
  • Fevers
  • Chills
  • Nausea and vomiting
  • Flank pain
  • White blood cells and casts in the urine

Complications due to pyelonephritis

  • Emphysematous pyelonephritis: in patients with diabetes mellitus the risk of acute pyelonephritis developing into EPN as a complication of acute pyelonephritis remains high. In EPN, the spread of inflammation is much more rapid and is more fatal than acute pyelonephritis.
  • Renal abscess: Formation of puss pockets in the kidney tissue as a complication of acute pyelonephritis remains a possibility too.
  • Recurrent infections: This complication can lead to the following:
    • Chronic pyelonephritis
    • Papillary necrosis
  • Xanthogranulomatous pyelonephritis: It is a rare complication of acute pyelonephritis in which the kidney parenchyma is degenerated by the process of granulomatous.   

Diagnosis of pyelonephritis

Oftentimes, the diagnosis of pyelonephritis is done by the clinical examination of the patients in which the following symptoms are searched for:

  • Flank pain
  • Costovertebral angle tenderness

When the clinical diagnosis is established for pyelonephritis, then the laboratory diagnosis of pyelonephritis is done to evaluate the severity of the condition. Some laboratory diagnostic methods of pyelonephritis are as follows:

  • Urinalysis
  • Pyuria
  • Bacteriuria
  • Urine culture

Treatment of pyelonephritis

After the evaluation of pyelonephritis in a patient through diagnosis, the treatment option suitable for them is decided to implement. Following are all the treatment options for acute pyelonephritis:

  • Rehydration: This is the universal part of the treatment for every pyelonephritis patient. This is important to restrict the damage done my acute pyelonephritis as often times due to dehydration renal failure occurs.
  • Antibiotics: This is the main treatment method for pyelonephritis and the dosages of different medicine depend upon the severity of the condition. General time period of antibiotic intake is 7-14 days
  • Hospitalization: For the complicated cases of pyelonephritis, patients are hospitalized to provide them with:
    • IV Ceftriaxone
    • IV Pip-Tazo
    • IV Fluoroquinolones


Pyelonephritis is a degenerating disease that is not treated properly. For a precise diagnosis of this kidney condition, one must always choose their medical assistance by seeing the experience of the practitioner who will handle them.

At Alfa Kidney Care, you will get the most experienced nephrologists to take care of you.