Pyelonephritis (Kidney Infection) Causes and Treatment

A kidney infection—called pyelonephritis—is a bacterial infection of one or both of your kidneys. The infection can cause sudden, severe symptoms like fever, chills, lower back (flank) pain, nausea, and vomiting.

The diagnosis of pyelonephritis involves a medical history, physical exam, and lab tests, most notably a urine culture. Antibiotics are the cornerstone treatment of pyelonephritis.

The article describes the symptoms and causes of pyelonephritis and explains how kidney infections are diagnosed and treated.

How Can You Tell You Have a Kidney Infection?

The kidneys are two bean-shaped organs of the urinary system, each about the size of a fist. They are situated just below the rib cage on each side of your spine.

Pyelonephritis is characterized by kidney pain. The infection may be acute (sudden and severe) or chronic (persistent or recurrent).

Signs and symptoms of pyelonephritis include:

• Flank pain
• Nausea
• Vomiting
• Fever
• Chills

With acute pyelonephritis, symptoms can come on fast and furiously, often within hours or a day.

With chronic pyelonephritis commonly seen in older adults with underlying kidney problems, symptoms are lower-grade but may also include malaise (a general feeling of unwellness), loss of appetite, and unintentional weight loss.

Complications

Kidney infections can sometimes spread to the bladder, causing a bladder infection (cystitis). Symptoms of cystitis include pain with urination (dysuria), foul-smelling urine, blood in urine (hematuria), and the need to pee frequently (urinary frequency) or urgently (urinary urgency).

If left untreated, pyelonephritis can turn severe and lead to potentially serious complications, such as:

• Kidney abscess (a pocket of pus on the kidney)
• Emphysematous pyelonephritis (in which the infections start killing kidney tissues)
• Sepsis (a severe immune response to a spreading infection)
• Kidney failure
  

What Are the Main Causes of a Kidney Infection?

A kidney infection occurs when bacteria travels from the urethra (the tube through which urine exits the body) to the bladder and then passes to one of both kidneys through the ureters (the tubes that connect the bladder and kidneys).

Bacteria associated with pyelonephritis include:

• Escherichia coli (E.coli)
• Enterococcus faecalis
• Pseudomonas aeruginosa, commonly acquired in hospital
• Klebsiella species, commonly acquired in hospital

Kidney infection can also happen if urine flow is blocked due to kidney stones, an enlarged prostate, and congenital malformations in the shape of your urinary tract.

Fungus are rare causes of pyelonephritis, most commonly seen in immunocompromised people, such as organ transplant recipients and people with advanced, untreated HIV.

Risk factors for pyelonephritis include:

• Being female: This is due to the location of the urethra nearer the anus as well as the shorter length of the urethra (making it easier for bacteria to reach the kidneys)
• Diabetes: High blood sugar can damage the urinary tract, making it harder to empty the bladder
• Having a weakened immune system: This can make it harder to fight infections.
• Spinal cord injury: This can keep you from noticing symptoms of a urinary tract infection
• Urinary catheters: These can introduce bacteria more easily into the bladder.
• Vesicoureteral reflux: This condition causes urine to backflow from the bladder to the kidneys.

How Kidney Infections Are Diagnosed

The diagnosis of pyelonephritis is based on your symptoms, a review of your medical history, a physical exam, and lab tests. Sudden, severe, flank pain and fever are tell-tale signs.

As part of the physical exam, your healthcare provider will check for costovertebral angle (CVA) tenderness by tapping your lower back just below the ribcage. With pyelonephritis, sharp pain will be felt in the underlying kidney.

Pyelonephritis is positively diagnosed with a urinalysis and urine culture, The urinalysis can check for signs of blood, pus, or white blood cells (a common sign of infection), while the urine culture can identify the exact bacteria causing the infection. Between 70% and 80% of kidney infections are caused by E. coli.

Imaging isn't needed for most cases of pyelonephritis. That said, imaging with an ultrasound or computed tomography (CT) scan can identify blockages or structural abnormalities in the urinary tract if symptoms are severe, resistant to treatment, or causing significant blood in the urine.

What Is the Best Treatment for a Kidney Infection?

The standard treatment of pyelonephritis is the administration of fluids to flush bacteria from the kidneys and antibiotics to kill bacteria causing the infection.

For uncomplicated infections, one or more antibiotics are taken by mouth over several days, most commonly:

• Bactrim (trimethoprim-sulfamethoxazole)
• Amoxil (amoxicillin)
• Augmentin (amoxicillin/clavulanate)
• Rocephin (ceftriaxone)
• Keflex (cephalexin)
• Cipro (ciprofloxacin)
• Levaquin (levofloxacin)

In severe cases where hospitalization is needed, fluids and antibiotics may need to be administered intravenously (into a vein).

Prevention

There are certain steps that you can take to reduce your risk of pyelonephritis, particularly if you are female and have recurrent urinary tract infections (UTIs):

• Drink plenty of water and urinate regularly,
• Urinate before and after sexual intercourse,
• Females should wipe from front to back to avoid introducing bacteria from stool into the urethra.
• Avoid feminine hygiene products like douches, sprays, and powders.

Summary

Pyelonephritis is a kidney infection. It is almost always caused by bacteria like E. coli, causing symptoms like flank pain, fever, nausea, vomiting, and chills. Pyelonephritis is diagnosed with a physical exam and urine tests. The treatment involves increased fluid intake and antibiotics.