Pyelonephritis, or kidney infection, is a type of urinary tract infection (UTI) that has progressed from the bladder to one or both kidneys. Pyelonephritis occurs when bacteria, often from the lower urinary tract, ascend to the kidneys, leading to inflammation and infection. 

Pyelonephritis can affect anyone, but certain groups, like women, are more susceptible due to anatomical differences. Pregnant women, in particular, need to be cautious as they are at a higher risk of developing this condition. It is also more common in individuals with a history of UTIs, those with certain medical conditions like diabetes, or those with a compromised immune system.

How Common is Pyelonephritis?

Pyelonephritis is a relatively common condition, though its prevalence can vary based on several factors such as age, sex, and underlying health conditions. Statistically, women are more prone to kidney infection due to their shorter urethra, which facilitates easier bacterial entry and ascent to the kidneys. It is estimated that pyelonephritis affects women almost six times more often than men. Amongst different age groups, young and sexually active women are particularly at risk, but this condition can occur at any age, including in children and the elderly. 

In terms of numbers, studies suggest that about 1-2% of women will experience pyelonephritis in their lifetime, with a higher incidence in those with a history of urinary tract infections. The condition is less common in men, but when it occurs, it is often associated with underlying urinary abnormalities or prostate issues. The prevalence of pyelonephritis also shows an increase in certain populations, such as those with diabetes or other conditions that compromise the immune system.

What are the Types of Pyelonephritis?

Pyelonephritis can be classified into two main types: acute and chronic. Acute pyelonephritis is the more common form, characterized by a sudden and severe onset. This type typically manifests with symptoms like high fever, flank pain, nausea, and urinary issues such as urgency and burning sensations. Acute pyelonephritis is generally caused by bacteria ascending from the lower urinary tract to the kidneys, leading to a rapid inflammatory response.

Acute pyelonephritis
Acute pyelonephritis: This is how very thin sections of the kidney with acute pyelonephritis look under microscope. Source:Wikimedia Commons 

On the other hand, chronic pyelonephritis is a long-standing or recurring form of kidney infection that can lead to more serious complications. This type often stems from structural abnormalities in the urinary tract or from a prolonged obstruction, which causes repeated or persistent bacterial infections. Chronic pyelonephritis can be more insidious, sometimes presenting with milder symptoms over a longer period, which can lead to gradual scarring and loss of kidney function.

There is also a specific form known as "xanthogranulomatous pyelonephritis," which is a rare and severe chronic form of the infection. It typically occurs due to long-standing obstruction and infection, often requiring surgical intervention.

What Causes Pyelonephritis?

Pyelonephritis is primarily caused by bacteria that enter the urinary tract and ascend to the kidneys. The most common culprit is Escherichia coli (E. coli), a type of bacteria commonly found in the intestines. These bacteria can migrate from the anus to the urethra, especially in women due to the shorter distance between these areas, and then travel up to the bladder and further into the kidneys, causing infection. Other bacteria like Klebsiella pneumoniae and Proteus mirabilis can also cause pyelonephritis, though less frequently.

Certain conditions and behaviors increase the risk of developing pyelonephritis. Urinary tract obstructions, such as kidney stones, can hinder urine flow and create an environment conducive to bacterial growth. Incomplete bladder emptying, which can occur in conditions like benign prostatic hyperplasia (BPH) in men or after certain surgeries, also raises the risk. Other risk factors include a weakened immune system, the use of urinary catheters, and conditions that cause urine to flow backward from the bladder to the kidneys, a condition known as vesicoureteral reflux.

Sexual activity can also contribute to the development of pyelonephritis, particularly in women, as it may facilitate the transfer of bacteria to the urinary tract. Additionally, a history of urinary tract infections (UTIs) increases the likelihood of the infection progressing to the kidneys. In summary, pyelonephritis is caused by bacterial invasion and is influenced by a variety of anatomical, physiological, and lifestyle factors that can increase the susceptibility to kidney infection.

Can I Prevent Pyelonephritis?

Preventing pyelonephritis involves several practical steps aimed at reducing the risk of urinary tract infections (UTIs), which often precede kidney infections. Good personal hygiene, particularly for women, is crucial. This includes wiping from front to back after using the toilet to prevent bacteria from the anal region from reaching the urethra. Staying well hydrated is also important, as regular urination helps flush out bacteria from the urinary tract. It is advised to urinate shortly after sexual intercourse to expel any bacteria that may have entered the urethra. 

Avoiding the use of irritating feminine products, like douches and powders, in the genital area can also reduce the risk. Additionally, managing chronic conditions like diabetes effectively is important since high blood sugar levels can increase the risk of infections. While not all cases of pyelonephritis can be prevented, these strategies can significantly reduce the risk and severity of potential infections.

What are the Signs and Symptoms of Pyelonephritis?

Pyelonephritis presents a range of symptoms that can vary in intensity but typically signify a more severe condition than a standard urinary tract infection. The most common and telltale sign is a high fever, often accompanied by shaking chills, indicating the body's fight against the infection. Patients usually experience significant pain or discomfort, particularly in the flank, back, or side, which is the area directly over the affected kidney. This pain can be persistent and severe.

Other urinary symptoms are also prevalent, including a burning sensation during urination, an increased urgency to urinate, and sometimes the presence of blood or pus in the urine. The urine may appear cloudy and have a strong odor. Nausea and vomiting can occur, reflecting the body's systemic response to the infection. Fatigue and a general feeling of being unwell are also common.

How is Pyelonephritis Diagnosed?

Diagnosing pyelonephritis typically begins with a thorough medical history and physical examination. Healthcare providers will look for hallmark symptoms such as flank pain, fever, and urinary discomfort. A key diagnostic tool is urinalysis, which tests urine for the presence of bacteria, white blood cells, or other indicators of infection. If this initial test suggests an infection, a urine culture is often performed to identify the specific type of bacteria causing the infection, which guides antibiotic treatment.

In some cases, particularly if the infection is severe or if there are concerns about urinary tract abnormalities, further imaging tests may be recommended. These can include an ultrasound or a computed tomography (CT) scan, which provide detailed images of the urinary tract and can reveal obstructions, abscesses, or anatomical abnormalities. In certain situations, particularly in recurrent or complicated cases, a cystoscopy might be performed. This procedure involves inserting a small camera through the urethra to visually inspect the bladder and urethra.

Blood tests may also be conducted to assess the kidney function and to check for signs of infection or inflammation in the bloodstream. For individuals with recurrent pyelonephritis, additional investigations to determine underlying causes, such as vesicoureteral reflux or other structural issues, may be necessary.

What are the Treatment Options for Pyelonephritis?

The treatment of pyelonephritis, or kidney infection, typically involves antibiotics, which are chosen based on the severity of the infection and the type of bacteria causing it. For mild cases of pyelonephritis, oral antibiotics are usually sufficient, and patients often experience symptom relief within a few days. Common antibiotics used include fluoroquinolones, cephalosporins, and amoxicillin-clavulanate. It is crucial to complete the entire course of antibiotics even if symptoms improve to ensure the infection is fully eradicated.

In more severe cases, or if the patient is pregnant, a child, elderly, or has a weakened immune system, hospitalization may be required for intravenous antibiotics. This ensures that the medication is more effectively delivered into the bloodstream, especially important if the patient is unable to keep down oral medications due to nausea or vomiting.

Alongside antibiotics, supportive treatments like pain relievers to manage pain and fever and adequate hydration are important. Hydration can be oral or intravenous, depending on the patient's condition. In cases where an obstruction, such as a kidney stone, is causing the infection, procedures to remove or break up the obstruction might be necessary.

For recurrent pyelonephritis, preventive measures or long-term low-dose antibiotics may be recommended. Additionally, addressing any underlying risk factors, such as managing diabetes or making lifestyle changes, is an integral part of treatment and prevention of future episodes.

What are the Side Effects of Pyelonephritis Treatment?

The primary treatment for pyelonephritis involves antibiotics, which, like all medications, can have side effects. The nature and severity of these side effects can vary depending on the specific type of antibiotic used and the individual's response. Common side effects associated with antibiotics include gastrointestinal issues like nausea, vomiting, diarrhea, and abdominal discomfort. Some individuals might experience allergic reactions, ranging from mild skin rashes to more severe reactions like anaphylaxis, though severe reactions are rare.

Certain antibiotics used for treating pyelonephritis can also cause photosensitivity, making the skin more susceptible to sunburn. Patients are advised to use sunscreen and wear protective clothing when outdoors. Some antibiotics, particularly fluoroquinolones, can affect tendons and might increase the risk of tendonitis or tendon rupture, particularly in older adults, those on corticosteroid therapy, and individuals with kidney, heart, or lung transplants.

In addition to antibiotic-related side effects, other treatments for pyelonephritis, such as pain relievers, can cause side effects like dizziness, drowsiness, or gastrointestinal discomfort. Intravenous antibiotics, given in more severe cases, can sometimes cause vein irritation or inflammation.

Can Pyelonephritis Come Back?

Yes, pyelonephritis can recur, particularly in individuals who have certain risk factors or underlying health conditions. Recurrent pyelonephritis is a concern because each infection can potentially cause more damage to the kidneys. Women are at a higher risk of recurrent infections due to anatomical factors that make it easier for bacteria to enter the urinary tract. 

Other risk factors for recurrence include structural abnormalities in the urinary tract, such as vesicoureteral reflux (where urine flows backward from the bladder towards the kidneys), kidney stones, or any condition that obstructs the normal flow of urine.

Individuals with weakened immune systems, such as those with diabetes or HIV, are also more susceptible to repeated infections. In some cases, the recurrence is due to the initial infection not being fully cleared, despite treatment. This can happen if the course of antibiotics is not completed or if the bacteria are resistant to the antibiotic used.

What is the Prognosis and Survival for Pyelonephritis?

The prognosis for pyelonephritis is generally good, especially when the condition is diagnosed and treated promptly. Most patients respond well to antibiotic therapy, with symptoms often improving within a few days of starting treatment. Complete recovery is typically expected without any long-term effects on kidney function, provided that the infection is not severe, and the patient does not have underlying kidney problems or other complicating health issues.

However, the prognosis can vary depending on several factors, including the severity of the infection, the presence of any underlying medical conditions, and how quickly treatment is initiated. In severe cases, or when treatment is delayed, pyelonephritis can lead to complications such as chronic kidney disease, kidney scarring, or even acute kidney injury. These complications can have long-term implications for kidney function and overall health.

In rare instances, if the infection spreads to the bloodstream, a condition known as sepsis can occur, which is a medical emergency and can be life-threatening. Prompt medical attention and adherence to treatment regimens are crucial in ensuring a positive outcome.

Pyelonephritis During Pregnancy

Pyelonephritis requires special attention during pregnancy due to its potential impact on both the mother and the developing fetus. Pregnant women are at a higher risk of developing pyelonephritis, partly because hormonal changes and the expanding uterus can affect urinary flow, making it easier for bacteria to ascend to the kidneys. The condition can present typical symptoms like back pain, fever, and urinary discomfort, but sometimes, symptoms are less pronounced, making vigilance crucial.

The implications of pyelonephritis during pregnancy are significant. It has been associated with increased risks of preterm labor, low birth weight, and other pregnancy complications like preeclampsia (high blood pressure during pregnancy). For this reason, prompt diagnosis and treatment are essential. Treatment typically involves antibiotics that are safe for use during pregnancy, and in more severe cases, hospitalization may be required for intravenous antibiotic therapy.

Pyelonephritis in Children

Pyelonephritis in children, while less common than in adults, is a significant health concern that requires prompt attention. This kidney infection often arises from a lower urinary tract infection and can present with symptoms like fever, abdominal or back pain, and changes in urination, such as urgency or pain. In very young children and infants, the signs might be less specific, including irritability, reduced appetite, or vomiting, making early diagnosis challenging.

The causes of pyelonephritis in children can vary. In some cases, it may be related to congenital abnormalities of the urinary tract that disrupt normal urine flow, increasing the risk of infection. Vesicoureteral reflux, a condition where urine backs up from the bladder to the kidneys, is a common contributing factor in pediatric pyelonephritis.

Will Pyelonephritis Cause Chronic Kidney Disease?

Pyelonephritis, if recurrent or not properly treated, has the potential to lead to chronic kidney disease (CKD). This risk arises mainly in cases where repeated kidney infections result in scarring and damage to the kidney tissue. Each episode of pyelonephritis can cause inflammation and harm to the kidneys, and over time, this cumulative damage can impair kidney function. Chronic pyelonephritis, a prolonged or recurring form of the infection, is particularly concerning in this regard, as it can gradually lead to the loss of kidney function and contribute to the development of CKD.

Will Pyelonephritis Lead to the Surgical Removal of Kidneys?

Surgical removal of a kidney, known as nephrectomy, due to pyelonephritis is relatively rare and typically considered only in severe and exceptional cases. Pyelonephritis, when diagnosed and treated promptly, usually resolves without causing irreversible damage to the kidney that would necessitate surgical intervention. 

However, in certain extreme circumstances, such as when the infection leads to a non-functioning kidney, severe abscess formation, or uncontrollable hypertension due to damaged kidney tissue, surgical removal might be considered as a treatment option. Additionally, in cases where pyelonephritis is associated with severe anatomical abnormalities of the urinary tract that cannot be corrected otherwise, surgery might be a viable option.

Living with Pyelonephritis

Living with pyelonephritis, involves not only managing the immediate symptoms and treatment but also adopting lifestyle changes and preventive measures to avoid recurrence and promote overall kidney health. For those who have experienced pyelonephritis, it is crucial to be vigilant about urinary tract health. This includes staying well-hydrated to help flush bacteria from the urinary system, practicing good hygiene, particularly after using the bathroom and during sexual activity, and ensuring complete emptying of the bladder regularly.

Regular medical check-ups are essential, especially for those with risk factors like diabetes, a history of urinary tract infections, or structural abnormalities of the urinary tract. During these visits, kidney function may be monitored, and any concerns or symptoms can be addressed.

For many, living with pyelonephritis also means managing stress and prioritizing self-care, as stress can impact the immune system and overall health. Support from healthcare providers, family, and friends can be invaluable in navigating the challenges of recurring infections and in making the necessary lifestyle adjustments.


In summary, pyelonephritis, commonly known as kidney infection, is a significant medical condition that requires timely diagnosis and appropriate treatment. While it can be a serious health concern, especially if recurrent or left untreated, the prognosis for pyelonephritis is generally favorable with prompt and proper care. Understanding the risk factors and symptoms is crucial for early detection and prevention. This condition, affecting a wide range of individuals, underscores the importance of urinary tract health and the need for awareness about kidney infections.

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Further Reading

  1. Foxman B. Epidemiology of urinary tract infections: incidence, morbidity, and economic costs. Am J Med. 2002;113(Suppl 1A):5S-13S.
  2. Flores-Mireles AL, Walker JN, Caparon M, Hultgren SJ. Urinary tract infections: epidemiology, mechanisms of infection and treatment options. Nat Rev Microbiol. 2015 May;13(5):269-84.
  3. Nicolle LE. Urinary tract infections in the elderly. Clin Geriatr Med. 2009 Nov;25(4):423-36.
  4. Colgan R, Williams M, Johnson JR. Diagnosis and treatment of acute pyelonephritis in women. Am Fam Physician. 2011 Sep 1;84(5):519-26.
  5. Tandogdu Z, Wagenlehner FM. Global epidemiology of urinary tract infections. Curr Opin Infect Dis. 2016 Feb;29(1):73-9.
Disclaimer: This blog post is intended solely for informational purposes. It is not meant to serve as medical advice. For professional medical guidance, please consult your doctor.


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