Urinary Tract Infection (UTI)
Table of Contents
- Introduction to UTI
- Types of UTI
- Cause and Risk factors
Introduction to Urinary Tract Infection (UTI)
What is the Urinary Tract?
The urinary tract is an organ system of the body that is involved in the removal of waste products. It is composed of multiple organs that produce, store, and remove urine according to requirements of the body. For the sake of understanding, the urinary tract can be divided into the upper urinary tract and lower urinary tract. The upper urinary tract consists of kidney and ureters; while the lower urinary tract is made up of bladder and urethra.
What is UTI?
When any pathogen (bacteria, viruses, etc.) invades a urinary tract organ, it is termed as urinary tract infection (UTI). The body responds to this infection by gathering relevant immune cells at the site of the invasion, through the bloodstream, initiating the process of inflammation. Inflammation is the body’s natural reaction to all foreign particles identified as harmful. This results in immune cells destroying the pathogens and saving the organs from their damaging effects. This also has some effects on healthy cells of the body, which explains symptoms like pain and fever.
Prevalence and Key Statistics
UTI is one of the most commonly encountered outpatient infections. It is estimated that around 150 million people around the globe are affected by UTI every year. 1 It is seen more frequently in women than in men, with the incidence increasing with age. It is postulated that nearly one out of every three women has a severe UTI by the age of 24, requiring antibiotic therapy, and almost half of the total female population experiences UTI at least once in a lifetime.2
Types of Urinary Tract Infection (UTI)
UTIs can be classified on the basis of a number of different factors.
Considering the organ involved, UTI can be classified as:
- Pyelonephritis: An infection of kidney tissue
- Ureteritis: An infection of ureters
- Cystitis: An infection of the bladder
- Urethritis: An infection of the urethra
Note: The vagina and prostate being in close relation with the urinary tract are often infected, and their infections are considered a part of UTI.
Based on the severity, complications involved, underlying anatomical defects, and previous medical history, UTIs are classified as:
- Simple UTI: In this type of infection, the patient is healthy, and there is no major anatomical defect. 3 Usually, this infection resolves easily without causing much trouble. This is common in young, healthy women who are sexually active.
- Complicated UTI: This infection usually occurs in the older population (regardless of the gender) and those with some other medical issues and low immunity.
The symptoms of UTI vary depending upon whether the upper or lower urinary tract is involved; however, there are some signs which generally occur in all types of UTI. These are:
- Frequency: A frequent desire to urinate
- Urgency: A sudden desire to urinate that cannot wait
- Bacteriuria: Bacteria are being shed in the urine
- Dysuria: Burning and painful urination
Symptoms of Upper UTI:
The symptoms of upper UTI are
- Flank pain (where the kidney is located)
- Burning micturition
- Urgency and frequency
The symptoms that help distinguish kidney infection from ureteritis are the presence of high-grade fever with chills and flank pain 4, but these may overlap in patients. Hence, a definitive diagnosis is made by using special tests.
Symptoms of Lower UTI:
In lower UTI, there is usually no fever, nausea, or vomiting. The most common symptoms that one may experience are
- Seldom hematuria (blood in urine)
A symptom common in urethritis is pyuria, which means white blood cells are being shed in the urine. There is also lower abdominal pain in lower UTI. 5
Causes and Risk factors
The cause of UTI is a bacterial invasion of urinary tract organs. There are certain factors that increase the risk of this invasion. These are:
- Female Gender: The infection occurring in the urinary tract is of ascending type, which means bacteria ascend from lower urinary tract organs to upper urinary tract organs. In females, the urethra is short and near the vagina that allows easy invasion of normal anal or vaginal flora (bacteria that reside within the anus and vagina without causing any harm) into it, which then move upward to involve other organs. Certain factors like frequent intercourse (4 or more times a week), use of spermicide as a contraceptive, and multiple sex partners may alter normal vaginal pH and flora as well. Thus, the introduction of any new bacteria and its invasion into urethra leads to UTI. 6
- Postmenopausal Effects: Menopause is an event where a woman becomes infertile and no longer produces a hormone (estrogen) that is necessary for not only femininity but for many normal bodily functions, as well. The postmenopausal effects because of the lack of estrogen increase the risk of UTI. When estrogen is no longer there, the tissues of the vagina and vulva start to degrade and become thin; this causes normal flora to gradually vanish, thus, allowing other pathogenic bacteria to reside, ultimately increasing the risk of UTI. 7
- Decreased Immunity: When any harmful substance enters the body, the immune system becomes activated and removes it. Many harmful bacteria and particles enter our bodies daily, which are easily removed by a healthy immune system. If the immune system is compromised because of some other diseases (for example, diabetes), the body will not be able to effectively clear the harmful agent, resulting in disease. Hence, a weak immune system is prone to common infections like throat infections, gut infections, and UTIs.
- Obstruction: An impacted stone within the urinary tract or any anatomical defect may obstruct the urine outflow. The standing of urine for long periods initiates bacterial multiplication and thus, increases the risk of UTI. One may experience recurrent infection because of this problem.
- Urinary Incontinence: The sudden involuntary leakage of urine is termed as urinary incontinence. Sometimes, there is incomplete bladder emptying due to urinary incontinence, which increases the risk of UTI. The storage of urine for longer in bladder allows bacteria to multiply easily.8
- Catheterization: Hospital-admitted patients are often catheterized for various reasons. The poor hygienic and non-sterile conditions favor the growth of bacteria and thus, increase the risk of UTI.8
Suspecting a UTI, your doctor may order the following tests:
- Complete Blood Count (CBC):
This is a complete profile of blood. It helps your doctor understand what’s going on inside your body by looking at the concentration of blood cells. The increased number of white blood cells depicts the presence of infection.
This is a complete profile of urine. It helps detect any unusual substances present in urine. The presence of an increased number of nitrites strongly suggests a bacterial infection.
- Urine Culture:
This is the gold standard diagnostic test for UTI. In this, varying favorable conditions are given to the bacteria obtained from your urine, in order to encourage their growth. Each medium is marked for a specific type of bacteria. The medium in which bacterial grow occurs confirms the presence of that bacteria in the urine.
- DNA Detection Test:
This test is done in high-risk individuals. The test looks for specific bacteria: Chlamydia trachomatis and Neisseria gonorrhea.
- Renal Function Tests (RFTs):
Your doctor may also check the normal functioning of your kidneys and the rest of the urinary tract. For this purpose, the following tests can be performed:
- Blood Urea Nitrogen (BUN): This test calculates the amount of nitrogen and urea present in the blood, the waste products produced by the body and eliminated by the kidneys.
- Serum Creatinine: Creatinine is another major waste product produced by the body and eliminated by the kidneys. This test measures the amount of creatinine in blood to see the functioning of the kidney.
- Serum Electrolytes: The negative and positive ions in the body are maintained in equilibrium by the kidneys. This test checks the concentration of electrolytes in the blood.
Plain radiographs and ultrasound images are used to check any obstruction in the urinary tract, especially if one is having frequent UTIs.
The first-line treatment for all UTIs is antibiotics. The duration and type of antibiotic depends on the severity, and other factors like pregnancy and concomitant health issues, and the type and sensitivity of bacteria identified by culture. The treatment plan is quite different for simple and complicated UTI.
- Treatment of Simple UTIs:
The commonly recommended and safely used drugs for this group are sulfamethoxazole/trimethoprim, fosfomycin, nitrofurantoin, cephalexin, and ceftriaxone. Usually, for lower UTI in a previously healthy individual, the recommended treatment duration is three days for women and ten days for men with sulfamethoxazole/trimethoprim. But again, this can vary depending upon different factors. The symptoms may resolve within a few days of therapy, but you should complete the course of your antibiotic to prevent a relapse.
- Treatment of Recurrent UTIs:
If you are having recurrent UTIs, your doctor may recommend a low-dose antibiotic for as long as six months. For postmenopausal females having frequent UTIs, hormone replacement therapy is often recommended.
- Treatment of Complicated UTIs:
The additional drugs given to these individuals are fluoroquinolones. They may be given orally or intravenously depending on the severity of the disease. The treatment duration maybe 1-2 weeks or more, depending on the symptoms. After resolution and completion of therapy, the doctor may order a culture test again to look for any leftover bacteria before declaring the patient completely healthy.
Some drugs are prohibited for pregnant women, as they interfere with the growth of the fetus and cause birth defects. These include Trimethoprim/sulfamethoxazole, tetracycline, and fluoroquinolone. So, your doctor will switch to an alternative if you are pregnant.
UTIs are very common infections, so preventive strategies are important in order to decrease the healthcare burden. These strategies focus on minimizing the risk of infection.
- Increased water intake: Increasing the consumption of water helps in diluting the urine. This causes one to urinate more frequently, thus, flushing out all the bacteria before they get the chance to grow.
- Cranberry juice: There is no definitive evidence, but this is widely suggested by doctors for numerous kidney diseases. It may significantly help in preventing UTI.
- Wiping properly: After urination and defecation, it is important to pay special attention to wiping. Since most of the bacteria getting into the urethra are anal or vaginal, the wiping position from front to back helps in reducing the risk of transferring bacteria from the anal region to the urethral opening.
- Void after intercourse: Voiding after intercourse helps in removing the bacteria that may have surrounded the urethral opening during sex. This also helps in restoring the acidic pH of the vagina.
- Select appropriate contraception: Diaphragm, unlubricated condoms, and use of spermicide alter vaginal pH and flora. It is essential to select an appropriate contraceptive method to reduce the risk of UTI.
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- Foxman B. (2002). Epidemiology of urinary tract infections: incidence, morbidity, and economic costs. The American journal of medicine, 113 Suppl 1A, 5S–13S.
- Hooton T. M. (2012). Clinical practice. Uncomplicated urinary tract infection. The New England journal of medicine, 366(11), 1028–1037.
- Belyayeva, M., & Jeong, J. M. (2020). Acute Pyelonephritis. In StatPearls. StatPearls Publishing.
- Li R, Leslie SW. Cystitis. [Updated 2020 Jun 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.
- Hooton, T. M., Scholes, D., Hughes, J. P., Winter, C., Roberts, P. L., Stapleton, A. E., Stergachis, A., & Stamm, W. E. (1996). A prospective study of risk factors for symptomatic urinary tract infection in young women. The New England journal of medicine, 335(7), 468–474.
- Raz R. (2001). Hormone replacement therapy or prophylaxis in postmenopausal women with recurrent urinary tract infection. The Journal of infectious diseases, 183 Suppl 1, S74–S76.
- Storme, O., Tirán Saucedo, J., Garcia-Mora, A., Dehesa-Dávila, M., & Naber, K. G. (2019). Risk factors and predisposing conditions for urinary tract infection. Therapeutic advances in urology, 11, 1756287218814382.