A kidney infection also called Pyelonephritis, is a painful and sudden inflammation of the kidneys as a consequence of urinary tract infections. All urinary tract infections are not always associated with kidney infection. It occurs when the bacteria from the bladder travels up to reach one or both kidneys.

If treated promptly with antibiotics it can be cured effectively. But early diagnosis is crucial for the treatment and if not treated the condition may worsen leading to permanent kidney damage.¹ Sometimes it is associated with kidney stones as the obstruction in passing urine helps in the multiplication of bacteria. The bacteria may also spread to the bloodstream and cause a more serious infection.

Common symptoms

Symptoms usually develop within hours or over a day.

Fever

• Associated with high fever,  often more than 103 °F (39.4 °C)¹
• Fever may be accompanied by shivering or chills

Pain in the lower back or side

• Pain and discomfort are usually present on the lower back or side (flank pain) and may be seen in the genital areas also.
• Frequent urination

The patient may have the urge to urinate frequently and is associated with

• Burning sensation
• Pain in the abdomen
• Cloudy and foul-smelling urine
• Inability to urinate fully

Blood in the urine

• Hematuria (the presence of blood in the urine) is also a common finding in patients with kidney infection. It is more commonly found in women.¹

Other symptoms include nausea, vomiting, loss of appetite and feeling tired or weak.

Importance of medical history in the diagnosis of kidney infection

A detailed medical history plays a crucial role in the diagnosis of kidney infection.

Symptoms and duration

Kidney infection usually presents itself as a classical triad of fever, lower back and side pain and nausea. Not all patients may have nausea and vomiting. Some of them may present with loss of appetite also.¹

In infants, the classical symptoms may be absent but they may present with fever and feeding difficulties. Sometimes jaundice without any other underlying cause may be the only symptom present in newborns.² 

Any feeling of frequent and urgent urination with a burning sensation and blood in the urine must be discussed with the physician immediately. An accurate description of the symptoms and the duration of experiencing them will help the healthcare provider in assessing the severity of the condition.

Past medical history

It is also important to discuss any episodes of previous urinary infections, kidney diseases or infections with the healthcare provider. The physician will also enquire about any condition that might weaken the immune system like HIV, diabetes etc.

Relevant risk factors

The physician may enquire about the patient's hygiene practices, habits, sexual activity, frequency of emptying the bladder, and contraception methods as these may influence the incidence of kidney infections.

Physical examination

• The physician assesses pain in the lower back and sides, by palpating the region between the lower ribs and spine. If the kidney is inflamed a firm pressure on this area will elicit pain
• The abdominal region will also be palpated to assess the pain
• Digital rectal examination

It is done to examine the prostate gland in men. The healthcare professional assesses whether an enlarged prostate is causing any obstruction to the neck of the bladder

• It is important to discuss symptoms and any relevant risk factors with your doctor during the consultation

Laboratory tests

Urine analysis

Urine analysis helps to find out the presence of any infection or traces of blood and pus in the urine. Midstream urine or catheter specimen of urine sample is collected in suspected individuals. Urine samples may best be collected before starting antibiotic therapy.

An increased count of white blood cells and bacteria suggests a kidney infection.

Urine culture

Urine culture helps to identify the exact bacteria responsible for the infection. E- coli is the most common bacteria causing acute kidney infections.¹

Blood tests

Blood tests give information about the overall health and help in the diagnosis of kidney infection. The commonly done tests are CBC(Complete blood count) and a blood culture.

CBC(Complete blood count)

It measures the different components of blood like red blood cells, white blood cells and platelets. Any abnormality in their count indicates the chances of an infection.

Blood culture

A blood sample is taken to check the presence of bacteria causing the infection.

Imaging tests

Ultrasound

Ultrasound imaging helps to visualise the kidneys and urinary tract using sound waves. It can be done at the bedside, has no radiation exposure and helps in definitive treatment.³ But a negative result should not exclude kidney infection as such. In high-risk patients, a CT scan should be done.⁴

X-rays

X-rays can be used to detect any obstructions like kidney stones but they are not as effective as other imaging techniques to identify a kidney infection.

CT scan (Computerized Tomography)

A CT scan of the abdomen and pelvis region is made especially when conditions like kidney stones are also present.⁴  CT scan is usually recommended for patients with high risk.

MRI scan (Magnetic Resonance Imaging) 

An MRI scan is done in patients where a CT scan cannot be done– like in pregnant patients. MRI also helps to differentiate a kidney infection from a kidney abscess.

Voiding Cystourethrogram (VCUG)

A voiding cystourethrogram is an imaging technique in which a contrast dye is injected to take the x-rays of the bladder while it is full and while urinating. It gives a clear picture of the urinary bladder and the urethra.⁵

Dimercaptosuccinic acid (DMSA) scintigraphy 

It is a highly reliable method to assess any inflammatory changes in kidney infection. Here a small amount of radioactive material is used to capture the picture of kidneys and urinary tract. It is particularly used in children when there is a chance of severe damage to the kidney.⁶

Biopsy 

In a kidney biopsy, a small tissue is taken from the kidney using a long needle under local anaesthesia and is examined under the microscope. It is not always necessary as simple non-invasive methods can effectively diagnose a kidney infection. It is done only in cases where there is severe inflammation and damage to the kidneys.

Who is at risk?

• A kidney infection can occur to anyone at any age. However,  people assigned female at birth (AFAB) are at greater risk because of shorter urethra and hence increased chances of bacteria entering the kidneys
• It is usually seen in patients with recurrent urinary tract infections (RUTI)
• Young sexually active people AFAB are also at high risk due to their high incidence of UTI¹
• Pregnant  people AFAB are also considered to be at increased risk due to their physiological condition and risk of UTI⁷
• It is also seen in patients who have used  recent broad-spectrum antibiotics and in those with inappropriate antibiotic usage( inadequate or long-term use, overdosage)

Treatment options

Antibiotics

Antibiotics are the primary treatment for kidney infections. The most commonly used antibiotics are oral cephalosporin for two weeks or fluoroquinolones for a week.¹ It is important to complete the full course of antibiotics as prescribed by the healthcare professional.

Hospitalisation (Severe cases)

Severe kidney infections require immediate hospitalisation and treatment involves intravenous antibiotics, painkillers and fluid administration.

Recurrent Infections

If there are any recurrent infections, then consult a specialist to overrule any underlying complications like congenital or developmental anomalies in the urinary tract.

Prevention of Kidney infection

• Always stay hydrated as it helps to flush out the bacteria and toxins from the urinary tract
• Emptying the bladder regularly helps to flush the bacteria out. Holding the urine helps the bacteria to multiply and cause infections
• Proper hygiene practices are very important in preventing kidney infections. This includes washing the genital area before and after sexual intercourse and wiping from front to back after using the toilet
• Practising safe sex is important as sexually transmitted diseases can lead to kidney infections
• A well-balanced diet with plenty of fruits and vegetables helps to boost immunity and prevent any kind of infections

When should you seek medical help?

You should seek medical help if you have a high fever with pain in the lower back, sides and genital area. If there are any symptoms like pain, burning sensation, cloudy foul-smelling urine, feeling unable to urinate fully or the presence of blood in the urine immediate medical attention should be sought. 

Summary

Knowing how kidney infection can be diagnosed early is crucial for effective treatment and maintaining the quality of life after treatment. Medical history and physical examination can help the healthcare provider to diagnose a kidney infection. It is important to discuss all the symptoms that you experience with your healthcare provider to help in the early detection of the condition. Along with this, the various imaging techniques and laboratory tests help to arrive at a definite conclusion and aid in the prompt treatment. It is important to keep in mind that early diagnosis is the key to successful treatment, faster recovery, and to prevent further complications.