Pyelonephritis

Pyelonephritis

Introduction to Pyelonephritis

Pyelonephritis is a type of urinary tract infection (UTI) that specifically affects the kidneys. It is an inflammation of the kidney tissue and renal pelvis, usually caused by bacterial infection, though viruses can also be responsible in some cases. This condition can affect one or both kidneys and is considered more serious than lower urinary tract infections, such as cystitis, because it involves the upper urinary tract and can lead to significant complications if not treated promptly.

Causes and Pathophysiology

The most common cause of pyelonephritis is a bacterial infection, typically by Escherichia coli (E. coli), which normally resides in the intestines. These bacteria can enter the urinary tract through the urethra and ascend to the bladder, causing cystitis, and then continue upward to infect the kidneys. Other bacteria such as Klebsiella, Proteus, Enterobacter, and Pseudomonas species can also cause pyelonephritis, especially in hospital-acquired infections or in patients with structural abnormalities of the urinary tract.

The infection usually begins in the lower urinary tract and ascends to the kidneys via the ureters. In some cases, bacteria can reach the kidneys through the bloodstream, especially in patients with compromised immune systems or systemic infections. Once bacteria reach the kidneys, they cause inflammation and swelling of the renal parenchyma and pelvis, which can impair kidney function.

Certain factors increase the risk of developing pyelonephritis, including urinary tract obstruction (such as kidney stones or an enlarged prostate), vesicoureteral reflux (a condition where urine flows backward from the bladder to the kidneys), diabetes, pregnancy, immunosuppression, and the presence of urinary catheters.

Symptoms

The symptoms of pyelonephritis are often more severe than those of lower urinary tract infections. Common signs include:

  • Fever and chills: High fever is a hallmark of pyelonephritis and often accompanied by shaking chills.
  • Flank pain: Pain in the back or side, typically on one side, over the affected kidney.
  • Dysuria: Painful or difficult urination.
  • Increased urinary frequency and urgency: A frequent need to urinate, often with a sense of urgency.
  • Nausea and vomiting: These symptoms may accompany the infection due to systemic illness.
  • General malaise and fatigue: Feeling unwell and tired is common.
  • Cloudy or foul-smelling urine: Urine may appear cloudy or have a strong odor due to infection.
  • Hematuria: Blood in the urine can sometimes be present.

In severe cases, pyelonephritis can lead to sepsis, a life-threatening systemic infection, especially if the infection spreads beyond the kidneys.

Diagnosis

Diagnosis of pyelonephritis is based on clinical presentation, physical examination, and laboratory tests. A healthcare provider will typically look for signs such as fever, flank tenderness (pain when pressing on the sides of the lower back), and symptoms of urinary tract infection.

Laboratory tests include:

  • Urinalysis: This test checks for the presence of white blood cells, red blood cells, bacteria, and nitrites in the urine, which indicate infection.
  • Urine culture: Identifies the specific bacteria causing the infection and helps guide antibiotic treatment.
  • Blood tests: May show elevated white blood cell count and markers of inflammation such as C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR). Blood cultures may be done if sepsis is suspected.
  • Imaging studies: Ultrasound or CT scans of the kidneys may be used if complications such as abscesses, obstruction, or stones are suspected, or if the patient does not respond to initial treatment.

Treatment

Prompt treatment of pyelonephritis is essential to prevent kidney damage and systemic complications. The mainstay of treatment is antibiotics, which are chosen based on the likely causative bacteria and local antibiotic resistance patterns.

  • Antibiotic therapy: Mild cases may be treated with oral antibiotics such as fluoroquinolones, trimethoprim-sulfamethoxazole, or beta-lactams. Severe cases, especially those requiring hospitalization, often need intravenous antibiotics initially.
  • Hospitalization: Patients with severe symptoms, dehydration, inability to tolerate oral medications, or complications may require hospital admission for intravenous fluids and antibiotics.
  • Supportive care: Includes pain management, hydration, and monitoring for complications.
  • Treatment duration: Typically lasts 10 to 14 days, but may be longer in complicated cases.

In cases where an underlying cause such as urinary obstruction or kidney stones is identified, addressing these issues is crucial to prevent recurrent infections.

Complications

If left untreated or inadequately treated, pyelonephritis can lead to serious complications, including:

  • Renal scarring: Repeated or severe infections can cause permanent damage to kidney tissue, leading to scarring and impaired kidney function.
  • Chronic pyelonephritis: Persistent or recurrent infections can cause chronic inflammation and progressive kidney damage.
  • Renal abscess: A localized collection of pus within the kidney may require drainage.
  • Sepsis: The infection can spread to the bloodstream, causing a life-threatening systemic response.
  • Acute kidney injury: Severe infection and inflammation can impair kidney function temporarily or permanently.
  • Hypertension: Kidney damage from pyelonephritis can contribute to high blood pressure.

Prevention

Preventing pyelonephritis involves reducing the risk of urinary tract infections and addressing predisposing factors:

  • Hydration: Drinking plenty of fluids helps flush bacteria from the urinary tract.
  • Urinary hygiene: Proper wiping techniques and urinating after sexual intercourse can reduce bacterial entry.
  • Prompt treatment of lower UTIs: Early treatment of bladder infections can prevent progression to the kidneys.
  • Managing underlying conditions: Controlling diabetes, treating urinary obstructions, and correcting anatomical abnormalities reduce risk.
  • Avoiding unnecessary catheterization: Catheters increase infection risk and should be used only when necessary.

Pyelonephritis in Special Populations

  • Pregnant women: Pyelonephritis during pregnancy is more common and can lead to complications such as preterm labor and low birth weight. Pregnant women with symptoms suggestive of pyelonephritis require prompt evaluation and treatment.
  • Children: Pyelonephritis in children may indicate underlying urinary tract abnormalities and requires thorough investigation.
  • Elderly: Older adults may present with atypical symptoms such as confusion or weakness and are at higher risk for complications.

Conclusion

Pyelonephritis is a serious kidney infection that requires timely diagnosis and treatment to prevent complications. It typically arises from bacterial infections ascending from the lower urinary tract and presents with fever, flank pain, and urinary symptoms. Diagnosis involves clinical evaluation and laboratory testing, while treatment centers on appropriate antibiotics and supportive care. Awareness of risk factors and preventive measures can help reduce the incidence of this potentially severe condition.

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