What is Acute Pyelonephritis (Kidney Infection)?
Acute pyelonephritis is a type of kidney infection that typically occurs when a urinary tract infection (UTI) in the bladder spreads upward to the kidney. It can also start from a bloodborne infection. It’s one of the most frequent kidney related illnesses. Symptoms can include fever, pain in the lower back or side, chills, nausea, vomiting, lack of appetite, painful urination, and an increased need to urinate often and urgently. The most common signs are fever and lower back or side pain.
There are two categories of acute pyelonephritis: complicated and uncomplicated. The complicated type is present in pregnant women, people with uncontrolled diabetes, people who’ve had a kidney transplant, those with abnormalities in the urinary system, people with acute or chronic kidney failure, people with weakened immune systems, and cases where the infection was caught in the hospital. It’s very important to identify whether the patient has either complicated or uncomplicated pyelonephritis because the type of treatment depends on it.
Chronic pyelonephritis is a more long-term condition, with persistent scarring and inflammation in the kidney due to ongoing or recurring infections. This type usually occurs in children who have significant urinary tract abnormalities or from a condition called vesicoureteral reflux. In adults, chronic pyelonephritis can describe a persistent or hard-to-treat kidney infection associated with severe abnormalities in the urinary tract, kidney stones, or a different type of inflammatory response, like in a condition called xanthogranulomatous pyelonephritis.
What Causes Acute Pyelonephritis (Kidney Infection)?
Bacteria can get to the kidneys in two ways: through the bloodstream or from a lower urinary tract infection. The bloodstream route is rare, and usually affects people who are unwell, have a weak immune system, or have a blockage in their urinary tract.
Most people get an inflammation of the kidneys, also known as acute pyelonephritis, from an infection that starts in the urinary tract. This can happen when bacteria from the rectum reach the urinary tract, then travel to the bladder. If the bacteria can multiply fast enough, they can reach the kidneys.
Urinary tract infections are more common in women because they have shorter urinary tracts which are close to the anus, and hormonal changes can also play a role. Any blockage in the urinary tract can lead to the bladder not emptying completely. This can allow bacteria to multiply because they are not being washed away.
A blockage caused by a kidney stone can lead to a more serious and life-threatening version of acute pyelonephritis.
Another lesser-known cause of acute pyelonephritis is a birth defect that allows urine to flow back from the bladder into the kidneys. Up to 40% of children diagnosed with a urinary tract infection will also be diagnosed with this disorder and it can lead to permanent damage to the kidney.
People who have had a kidney transplant are very likely to get pyelonephritis because of a weaker immune system and changes in their kidney structure, especially in the first 6 months after transplant.
Escherichia coli is the most common cause of acute pyelonephritis and most other urinary tract infections. Candida spp is another possible cause, often found in older individuals, patients with diabetes, patients treated extensively with antibiotics, those with urinary catheters, and hospital patients, especially in the ICU.
There is a growing problem with bacteria that are resistant to antibiotics. Now, over 90% of bacteria causing urinary tract infections are resistant to at least one antibiotic, and about 80% are resistant to at least two.
People are more likely to get infections from these bacteria if they have recently used a lot of antibiotics, have a blockage in their urinary tract, have had repeated urinary tract infections, been hospitalised, have a urinary catheter, are older, or have been misusing antibiotics.
There is a general problem with overuse of antibiotics in healthcare, and factors like not regulating the use of last-resort antibiotics also contributes to this.
If less than 10% of bacteria in a community are resistant to an antibiotic, it is usually considered useful. However, antibiotics that don’t penetrate tissue or get excreted in the urine aren’t usually used for treating pyelonephritis.
In less developed countries, there are some unique factors, such as poverty leading to delays in seeking medical care, use of alternative therapies, insufficient healthcare systems, poor patient education, and difficulties with identifying counterfeit drugs.
Risk Factors and Frequency for Acute Pyelonephritis (Kidney Infection)
Acute pyelonephritis, a type of kidney infection, has an annual rate of 15 to 17 cases per 10,000 females and 3 to 4 cases per 10,000 males in the United States. This results in an overall total of 250,000 cases every year. An extensive study in Sweden found that if a urinary tract infection (UTI) or cystitis (bladder infection) was not treated with antibiotics within 5 days, it developed into pyelonephritis nearly 1.43% of the time.
- Acute pyelonephritis most often affects young, sexually active women because they have a higher rate of UTIs. However, men have a higher mortality rate.
- Men are more likely to have related health conditions such as diabetes, kidney stones, or kidney disease.
- Groups at the extremes of age, like older adults and infants, also face a higher risk.
- There is no evidence to show that any racial group is more likely to get acute pyelonephritis than others.
- Pregnant women are considered a high-risk group because their bodies are changing in ways that make them more susceptible to UTIs. Acute pyelonephritis in pregnant women can lead to complications for the mother and, in some cases, premature birth and low birth weight.
It’s important to note that while earlier studies suggested treating pregnant women with no symptoms but bacteria in their urine (asymptomatic bacteriuria) to prevent pyelonephritis, more recent data supports not doing so, especially as antibiotics can have potential side effects. The matter still needs to be studied further through high-quality clinical trials.
Signs and Symptoms of Acute Pyelonephritis (Kidney Infection)
Acute pyelonephritis, an infection of the kidney, usually comes with a combination of fever, side pain, and nausea or vomiting, though not all symptoms may be present. Some patients might also experience loss of appetite in the absence of nausea or vomiting. Symptoms typically develop within a few hours or over a day. Symptoms related to bladder infection like painful urination and blood in urine are more common in women.
- Fever
- Side pain
- Nausea or vomiting
- Loss of appetite
- Painful urination (more common in women)
- Blood in urine (more common in women)
In children, especially newborns and kids under two years, classic symptoms might be missing. They might exhibit symptoms like slow growth, fever, and feeding issues. Elderly patients might show signs of sudden mental confusion or altered mental state, fever, loss of appetite along with kidney failure, and damage to other organs.
People with pyelonephritis may have a high fever, often over 103 °F (39.4 °C). Despite the high fever, they usually don’t seem very sick and might look quite normal. Blood pressure reading below 90 mm Hg could indicate a more serious condition, possibly septic shock.
During a physical examination, signs can vary. Tenderness over the kidney area on the back, tenderness over the lower abdomen, and absence of abdominal pain except in the lower abdomen area are some patterns. Normal bowel sounds and skin appearance, except in cases with possible Herpes zoster, might be observed. Symptoms in men, older adults, and young children can be very different.
- Tenderness over the kidney area on the back
- Tenderness over the lower abdomen
- No abdominal pain except in the lower abdomen area
- Active bowel sounds
- Flexible abdomen
Testing for Acute Pyelonephritis (Kidney Infection)
If you’re being checked for acute pyelonephritis (a severe kidney infection), your doctor will primarily rely on your medical history and a physical examination. But lab tests and imaging studies can also assist in confirming the diagnosis.
One of the first things your doctor will do is take a urine sample for testing and culture. This can help confirm if you have pyelonephritis, though in up to 30% of cases the urine culture may be negative. Blood tests are also conducted to look for signs of infection or sepsis (a dangerous response to infection in the body).
The urine test will look for increased white blood cells (a condition known as pyuria), certain chemicals such as nitrite (which may suggest the infection is caused by certain types of bacteria), protein, and blood. Other causes such as kidney stones should be considered if there is blood in your urine. The presence of a specific type of bacteria in the urine can also indicate pyelonephritis.
Blood tests may include a complete blood cell count to look for increased white blood cells (a sign of infection) and to check for signs of sepsis (a dangerous, body-wide response to infection). Tests to assess kidney function and other signs of infection are also commonly done.
Imaging tests may not be needed for uncomplicated cases, but these should be considered for patients considered high-risk. These include patients with diabetes, recurrent pyelonephritis, hospital-acquired infections, sepsis, kidney stones, transplant recipients, and immunosuppressed individuals, among others.
The go-to imaging test for acute pyelonephritis is an abdominal/pelvic CT scan. It can spot kidney stones, which can greatly complicate treatment. Ultrasound can be used too, but it’s not as reliable as CT scans, so it’s usually only used when a CT scan isn’t appropriate. In certain circumstances, MRI can also be useful.
In pregnant women, who are more susceptible to serious complications from pyelonephritis, an ultrasound is usually the first imaging test used. If the diagnosis is still not clear, an MRI or other tests might be considered.
In rare cases, a more severe type of kidney infection known as acute lobar nephronia may be present. This condition requires prolonged antibiotic therapy and is usually detected using a contrast-enhanced CT scan or MRI.
For patients with urinary obstructions and signs of severe infection, urgent surgical drainage is often required. CT scanning may be needed to confirm the diagnosis and determine the exact cause of the urinary obstruction.
Treatment Options for Acute Pyelonephritis (Kidney Infection)
In simple terms, young, healthy, non-pregnant women with uncomplicated pyelonephritis, or kidney infection, can be treated outside of a hospital setting. The main treatments include antibiotics, painkillers, and fever-reducing medications. Anti-inflammatory medications can also be effective in treating pain and fever associated with kidney infections.
The initial selection of antibiotics depends on the local resistance patterns of bacteria to antibiotics, which will vary between different hospitals or institutions. Once urine culture results are available, the antibiotic therapy can be adjusted accordingly.
A common bacteria that causes kidney infections is E. coli. This can usually be treated with certain types of oral antibiotics like cephalosporins, sulfamethoxazole-trimethoprim or fluoroquinolone.
The American College of Physicians recommends treating uncomplicated kidney infections with sulfamethoxazole-trimethoprim for 14 days or a fluoroquinolone for 5 to 7 days. However, this depends on local bacterial resistance patterns which can affect antibiotic sensitivity.
A doctor is responsible for reviewing the culture results and discussing them with the patient, particularly if changes in therapy are necessary. Generally, antibiotics that the bacteria are sensitive to are preferred if possible.
Depending on the community’s resistance to certain antibiotics, different measures may need to be taken. For cases where there is significant potential for bacterial resistance, a long-acting antibiotic injection may be administered in the emergency department before the patient is discharged.
It is crucial that patients follow up 24-48 hours after discharge to check symptoms and make necessary adjustments to treatment. However, uncomplicated cases that have resolved do not require any imaging or additional urine cultures.
Significantly ill patients might require an inpatient treatment in the hospital. These patients include those with severe infection symptoms, high fever, intolerable pain, persistent nausea, weakness, failure of outpatient treatment, likelihood of not complying with therapy, or inadequate care at home.
Hospitalization might also be required for patients with impaired immune systems, kidney transplant recipients, poorly controlled diabetes, pregnant women or suspected urinary tract obstruction. Roughly 20% of all patients with kidney infections will require inpatient treatment.
In case of an obstructed kidney infection, emergency surgical procedures are needed which are usually followed by targeted antibiotic therapy. Delaying these emergency procedures can increase the mortality rate.
Antibiotics for inpatients include a long list, and the selection depends on various factors such as local resistance rates, organism sensitivity, critical status of the patient, etc.
Intravenous antibiotics are generally given for at least 48 hours, after which culture results are available, and patients should have shown improvement. If not, there might be a need to change antibiotics and continue with intravenous therapy.
Pregnant patients should be treated with certain antibiotics as per the guidelines from the American College of Obstetricians and Gynecologists.
In conclusion, the key to tackling infections like pyelonephritis is to minimise the overuse of broad-spectrum antibiotics, where possible. Initial treatment can focus on symptomatic therapy before culture-specific results are available, which usually takes about 48 hours. The risk of a simple urinary tract infection progressing into pyelonephritis is quite low. Prescription changes and adoption of proper initial antibiotics can help reduce bacterial resistance to antibiotics.
What else can Acute Pyelonephritis (Kidney Infection) be?
When a doctor is trying to diagnose kidney infection, or acute pyelonephritis, they must consider a wide range of other conditions that could cause similar symptoms. These symptoms might include fever, pain in the side or back, and tenderness in the area where the ribs and spine meet. Symptoms can vary widely, from occurring on one or both sides, to appearing as either sharp or dull pain. Pyelonephritis can also worsen quickly, leading to sepsis or shock. Therefore, many different diagnoses must be considered.
When a patient presents these symptoms, doctors might consider other health issues like:
- Appendicitis
- Gallbladder inflammation (cholecystitis)
- Inflammation of the rib cartilage (costochondritis)
- Diverticulitis
- Ectopic pregnancy
- Womb lining inflammation (endometritis)
- Focal nephronia (a localized kidney infection)
- Shingles (herpes zoster)
- Pneumonia affecting one lobe of the lung (lobar pneumonia)
- Kidney stones (nephrolithiasis)
- Ovarian cysts
- Pancreatitis
- Pelvic inflammatory disease
- Collection of pus around the kidney (perinephric abscess)
- Pyonephrosis (a type of kidney infection with blockage)
- Kidney abscess
- Rib fracture
- Ureterolithiasis (stone in the ureter)
- Ureteropelvic junction obstruction (blockage where kidney and ureter meet)
- Urolithiasis (urinary tract stones)
- Xanthogranulomatous pyelonephritis (a rare form of kidney infection)
Physician will carefully study these possibilities along with appropriate tests for an accurate diagnosis.
What to expect with Acute Pyelonephritis (Kidney Infection)
Most cases of pyelonephritis, a type of kidney infection, are treated successfully in an outpatient setting. Around 80% of patients get better with treatments including antibiotics and pain killers. Usually, young, healthy women with a straightforward case of the condition are most likely to be treated outside of a hospital.
Uncomplicated pyelonephritis is typically not life-threatening unless it’s linked with other conditions like emphysematous pyelonephritis, perinephric abscess, pyonephrosis, or sepsis. In these situations, mortality rates of 25% or more have been reported. However, the outcome depends on how severe the disease is, the patient’s other health conditions, and how quickly it’s diagnosed and treated.
Even though most cases of pyelonephritis get better, severe or complicated cases can still be significantly harmful, and even fatal. Pregnant women particularly are at a very high risk for premature delivery and other complications like acute respiratory distress syndrome, kidney injury, severe infection, restricted baby growth inside the womb, and even fetal death.
The overall death rate for acute pyelonephritis varies between studies. Some report it as 10% to 20%, while a recent study from Hong Kong found it to be closer to 7.4%. Factors leading to a higher risk of death include being older (above 65 years), having diabetes or kidney failure, experiencing septic shock, having a long-term catheter, limited mobility, and being male.
However, with early recognition of the cause and immediate treatment, even patients with severe pyelonephritis often have a good outcome. Early use of the right antibiotics can be crucial, improving outcomes and potentially saving lives.
Possible Complications When Diagnosed with Acute Pyelonephritis (Kidney Infection)
Acute pyelonephritis, or sudden kidney infection, can lead to several complications. One of the more serious ones is emphysematous pyelonephritis. This is a devastating infection of the kidneys, usually due to E. coli or Klebsiella pneumoniae bacteria. This severe complication is often seen in people with diabetes, particularly women. Diagnosing this condition can start with an ultrasound, but typically, a CT scan is needed for confirmation. Statistics show that up to 38% of people with this complication die, but the chances of survival grow if the patient receives both medical treatment and surgery, instead of just medical treatment.
There are other complications to look out for, including:
- Acute focal nephronia, also known as acute focal bacterial nephritis
- Acute renal failure
- Chronic pyelonephritis
- Obstructive pyelonephritis
- Papillary necrosis
- Perinephric abscess
- Renal abscess
- Renal scarring and atrophy
- Renal vein thrombosis
- Sepsis and urosepsis
- Xanthogranulomatous pyelonephritis
Preventing Acute Pyelonephritis (Kidney Infection)
The best way for healthy, young women before menopause to prevent severe kidney infections or acute pyelonephritis is by preventing urinary tract infections (UTIs). Several factors can cause UTIs, but some simple prevention tips include going to the toilet before and right after sexual intercourse, drinking more water to flush out the urinary system, and wiping from the front to the back after using the toilet. This helps reduce the chances of introducing bacteria into the urinary tract.
Other than these behaviors, research also suggests that drinking cranberry juice, taking probiotics and certain supplements like D-mannose, and methenamine, vitamin C, or low-detail antibiotics could prevent UTIs.
To avoid recurrent severe kidney infections, it’s crucial that patients follow their antibiotic treatment as prescribed and finish the entire course. Drinking more water can prevent dehydration, reduce the risk of UTIs by regularly cleaning the bladder, help avert severe kidney infections, and maintain healthy kidney function.
