Introduction

Definition of recurrent kidney infections

A recurrent kidney infection is defined as three or more instances of infection in a year. 

Importance of preventing recurrent kidney infections

Our kidneys function as a natural filtration system, removing waste products like urea and drugs from our blood and removing extra fluid through urine. Recurrent acute kidney infections increase the risk of chronic kidney infection, or in worse instances, kidney disease. Chronic kidney infection is defined by the long-term damage and scarring caused by repeated bacterial infection, resulting in a loss of renal parenchyma, an important filtration component in the kidneys. Kidney disease is characterized by a gradual loss of renal function over time. In the late stages, the kidneys may completely malfunction, resulting in kidney failure.

As well as this, if recurrent kidney infections are not prevented, the risk of the infection getting into the bloodstream and causing sepsis is increased.

Causes of recurrent kidney infections

Anatomical abnormalities

Vesicoureteral reflux

In rare cases where urine flows backwards from the bladder up through the ureter(urine tube) toward the kidneys, this condition is known as vesicoureteral reflux (VUR). VUR occurs because of a functional complication with the one-way valve that connects the ureter to the bladder. This can be an issue with one ureter (a unilateral reflux) or both ureters (a bilateral reflux). 

Demographically, VUR is most often seen in babies and young children under 2 years old. In a 2022 study of children with urinary tract infections, a common consequence of VUR, 57% of all patients that were found to have VUR were under the age of 1 year.¹

In babies, the condition is most common in boys but becomes more prevalent in girls as age increases. This is likely due to posterior urethral valves (PUV), which are only present in the male urinary tract and are usually detected during infancy. PUV occurs seemingly randomly during pregnancy and is characterized by a blockage in the urethra. This causes the child to overexert whilst urinating which causes a build-up of pressure, leading to VUR.

Kidney stones

Recurrent kidney stones are likely to cause recurrent kidney infections. Kidney stones are very common, occurring in approximately 10% of the population. They are lumps of crystallized waste, which form when there is the absence of enough liquids for the waste to dissolve in. Often they are minor and easily flushed through the body by drinking more water. However, in more serious cases, a kidney stone may get lodged in the ureter, blocking the flow of urine to the bladder. When this happens, the urine levels will build up in the kidneys. Since urine contains the waste products we aim to remove, this can lead to a build-up of bacteria resulting in an infection in the kidneys.

Recurrent kidney stones may be caused by:

• Poor hydration
• No change to a diet high in protein/salt 
• Obesity²
• Genetics - Dent disease,³ cystinuria,⁴ primary hyperoxaluria type 1⁵

Chronic medical conditions

Recurrent urinary tract infections (UTIs)

UTIs typically cause pain while urinating and the uncomfortable feeling of needing to constantly or suddenly urinate. Lower stomach pain is common, in addition to dark and cloudy urine, but they are short-lasting and tend to go away with a short course of antibiotics. 

If the UTI becomes recurrent, this is a cause for concern as it can lead to kidney infections. UTIs are classed as recurrent after the occurrence of 2 acute UTIs within 6 months, or 3 episodes within a year. Recurrent UTIs can happen for a number of reasons, including functional defects (e.g. urinary incontinence); anatomical defects (e.g. bladder or pelvic prolapse); or human error factors (e.g. not completing previous treatment or repeatedly not urinating after sex).⁶ 

Recurrent UTIs will require multiple courses of antibiotics. Typically, a patient will be prescribed a different antibiotic than before to reduce the risk of developing antibiotic resistance. However, if the course of antibiotics is not carried out properly – that is, they are taken irregularly or the course is not completed, this may lead to bacteria not being completely eradicated. This residual bacteria can then proliferate and spread to the kidneys, potentially causing recurrent kidney infections if left untreated. 

Diabetes

Diabetics are prone to urological health issues, such as kidney infections. Generally, diabetes is associated with higher levels of infection. A study from 1992 comparing the incidence of bacteraemia due to E. coli in diabetics and non-diabetics reported that 67% of the bacteraemias were found in those who had diabetes.⁷ Therefore, a person with diabetes is more predisposed to getting recurrent infections of the kidneys due to their difficulty fighting off infection in general.

A hallmark of diabetes is high blood sugar. Elevated blood glucose levels, or hyperglycaemia, have been linked to an increased frequency of E. coli infections of the urinary tract.⁸ Through various mechanisms, hyperglycaemia weakens the immunity of a diabetic, resulting in them becoming immunocompromised and therefore susceptible to infection. Additionally, blood glucose has been found to confer protection to E. coli, increasing the risk of infection, or reinfection.⁹

Symptoms & diagnosis

Common symptoms

The following are common symptoms of a kidney infection:

• Fever/chills
• A burning feeling when passing urine
• A frequent and/or strong urge to urinate
• Back, side, groin, or belly pain
• Nausea/vomiting
• Blood in urine
• Urine with a foul odour or that is cloudy in appearance¹⁰

Diagnostic methods

There are three main methods of diagnosing kidney infections. These include:

• Urinalysis
• Imaging tests (e.g., ultrasound, CT scan)
• Blood tests

Prevention strategies

Medical interventions

Antibiotic prophylaxis

Antibiotics are the first line of treatment for kidney infections. Antibiotics are required promptly to prevent further damage to the kidneys and infection of the blood (septicaemia). In order to prescribe antibiotics, a sample of urine should be tested. These tests should highlight the presence of bacteria in the urine, and the specific type of bacteria present. Kidney infections are typically caused by four types of bacteria: 

• E. coli (by far the most common)
• P. mirabilis
• Enterobacter
• Staphylococcus

In order to prevent recurrent kidney infections, it is imperative to complete the course of antibiotics after the initial infection. Otherwise, any residual bacteria may proliferate and cause reinfection.

Taking antibiotics when it is not needed can increase the risk of antibiotic resistance, leading to further problems and infections. However, occasionally antibiotics are prescribed at a low dose on a long-term basis as a prevention strategy. This is particularly the case for people who are at a higher risk of infection because of a pre-existing health problem such as diabetes.

Surgical correction of anatomical issues

Since one reason for recurrent kidney infections may be an underlying anatomical issue, they can be prevented by surgical intervention. If the infections are indeed being caused by this, referral to a nephrologist or urologist for further analysis and surgery will help address the root cause through structural modifications, preventing any recurrent infections. Kidney disease will also be able to be detected through routine check-ups since in the early stages there are very few obvious symptoms.

Monitoring and follow-up

Regular medical check-ups

Regular medical check-ups and medical insight from a licensed professional are always excellent ideas when dealing with chronic illnesses. The same goes for recurrent kidney infections because of the risk of kidney disease.¹¹ 

Routine checkups can be pivotal in highlighting any genetic predispositions to recurrent kidney infections by discussing family history. They can also help identify patterns in previous kidney infections by going through a patient’s health history. Conversations with specialists and subsequent referrals for scans may also bring to light some structural complications which will likely need to be resolved to prevent recurrent infections.

Early treatment of UTIs

If left untreated, UTIs can cause kidney infections as the bacteria travels up to the kidneys. The exact statistics for how often UTIs cause kidney infections are unknown, but it is important to recognise that even if it is an infrequent occurrence, the severity of a kidney infection is distinctly higher than that of a UTI. Therefore, prompt treatment is highly recommended. 

Treatment of UTIs involves a short course of oral antibiotics, usually 3 days long, although men and pregnant women are recommended a longer course. Symptoms of the infection tend to subside in the 3 to 5 days following treatment. 

Conclusion

In conclusion, recurrent kidney infections, defined as three or more instances within a year, often stem from underlying urinary tract issues such as VUR or kidney stones. These structural abnormalities can obstruct urine flow, leading to infections that may persist if not properly treated. Individuals with diabetes are particularly susceptible to recurrent infections due to compromised immune function and other physiological factors. Preventive measures, including surgical interventions to correct abnormalities, are crucial, as is the responsible use of antibiotics to avoid reinfection or the development of antibiotic resistance. Additionally, lifestyle modifications, such as staying well-hydrated and maintaining good urinary hygiene, can further reduce the risk of infections. Regular follow-ups with healthcare providers are important to monitor any underlying conditions and ensure comprehensive treatment. Addressing these factors is essential to reducing the risk and impact of recurrent kidney infections, ultimately improving patient outcomes and quality of life.