Urinary tract infection - Symptoms, Causes, Prevention and Treatment

Urinary tract infection definition

Urinary tract infection (occasionally called UTI infection) is a collective term given to various bacterial infections that occur in the urinary tract. One of the most commonly occurring diseases on the planet, the UTI causing organisms have the potential to invade adjacent tissues and/ or result in kidney complications. Nevertheless, with an appropriate antibiotic, UTI rapidly responds to antibiotic therapy prescribed by a urologist.

As such, the most common manifestation of UTI infection is acute cystitis (a type of bladder infection), which is far more prevalent among women than men; most clinical research on urinary tract infection has involved the women population. It has led to one of the common misconceptions that UTI infection is a gynaecological disease.

While it is true that UTI infection is overwhelmingly seen in women (approximately 1 in 3 females by 24 years), it is not a gynaecological disease, as this disease is also seen in men but less frequently.

Cystitis meaning

Cystitis is one of the common UTI infections. Cyst stands for "bladder-like bag or vesicle in an animal body", from the early Greek root “kystis," which meant "bladder, pouch", “-itis" is the word-forming suffix usually in medicine, which denotes "diseases characterized by inflammation" coming from the Modern Latin and Greek roots –“itis".

A higher rate of E. coli followed by Klebsiella spp are the commonly seen pathogens across the globe. Comparatively, the studies from the Asian continent have reported reduced E. coli cases. 



An Indian study from 2002 demonstrated the prevalence of E. coli as the most associated organism (64.3%), followed by Staphylococcus aureus and Klebsiella pneumoniae with (21.4%) and (14.3%) respectively. E. coli colonisation is higher in poorly controlled diabetics with HbA1C. An Indian study published in 2011 demonstrated that 42.8% of subjects from a sample of 1157 patients were suffering from UTI infection. 

Classification of urinary tract infection can be made according to the anatomical sites. Lower UTI infection could include diseases such as cystitis, urethritis, etc, while pyelonephritis can be included in upper UTI infection. It also differs from genders, such as bacterial prostatitis, epididymitis, orchitis, and epididymorchitis, which is seen in men. Delving deeper, the common types of UTI infections include: 

• Uncomplicated cystitis: A bladder infection that occurs in an otherwise healthy, premenopausal, nonpregnant, female with a healthy urinary tract.
• Complicated cystitis: A serious bladder infection is usually caused by foreign body-induced cystitis (such as a catheter or stone), urinary tract abnormalities, instrumentation, or vesicoureteral reflux (urine moves backward - from the bladder to kidneys). Catheter associated urinary tract infection falls under this category. 
• Uncomplicated pyelonephritis: Renal infection which occurs in an otherwise healthy, nonpregnant patient with a normal urinary tract.
• Recurrent UTI infection: Defined as ≥ 3 UTIs in 12 months or ≥ 2 UTIs in 6 months.
• Asymptomatic bacteriuria (colonization): If more than a lakh colony-forming units per milli litre (1,00,000 cfu/mL) of bacteria are seen in urine culture without any symptoms of illness or signs, it is called asymptomatic bacteriuria.
• Complicated pyelonephritis: A kidney infection during pregnancy or in a patient associated with other complicating factors, requiring hospitalisation. 
• Interstitial cystitis: A condition of increased bladder pressure, pain and sometimes extending to the pelvis. It is also called bladder infection. It is also called honeymoon cystitis. If the infection lasts more than six weeks, it is called chronic cystitis. 

UTI infection can also be stratified as healthcare-associated urinary tract infection (HAUTI) and community-associated urinary tract infection (CAUTI).

The most common cause of urinary tract infections (UTIs) is bacteria (most commonly Escherichia coli (E. coli)). These bacteria can enter the urethra (the tube that carries urine out of the body), and travel up the urinary tract, where they multiply and cause infection.

These are some other potential causes of urinary tract infections (UTIs):

• Sexual activity
• Incomplete bladder emptying
• Anatomical abnormalities (a shortened urethra or bladder prolapse)
• Medical conditions (Diabetes, kidney stones, usage of catheter)
• Weakened immune system
• Poor Hygiene or Improper Hygiene Practices

The common risk factors that could enhance the risk and potentiality of urinary tract infection are as follows: 

• Female gender 
• Older age 
• Urine incontinence 
• Family history and genetics 
• Catheterization 
• Procedure 
• Kidney or bladder stones 
• Diabetes mellitus 
• Immunocompromised status

• Female gender: In females, the anatomical distance from the urethral opening to the bladder is short when compared to that of males. It increases the chances of bacterial migration from the rectum to the urethral opening due to closer proximity, thus, enhancing the E. coli colonization and urinary tract infection progression. 
• Older age: In the elderly (≥ 65 years, and particularly ≥ 80 years), the risk of male and female UTI infection is increased, and by 80 years of age, both genders have similar rates of UTI infection. Also, reduction in estrogen levels in postmenopausal women is another risk factor.
• Urine incontinence: This is one of the common risk factors which rapidly increases the risk of UTI infection by four times. 
• Genetics and family history: A 2-4-fold increased risk of UTI infection is seen in the offspring (especially if it’s a girl) if the mother had UTI infections in her lifetime. 
• Catheterization: Catheters are commonly used in hospitalized patients (accounting for about 70% of UTIs) which can significantly increase the urinary tract infection risk, especially with longer hospital stay. Catheterization issues such as neurogenic bladder, incomplete bladder emptying, etc all increase the risk of UTI infection, so as anatomic abnormalities of the genitourinary tract.
• Procedure: The risk of UTI infection increases during the immediate postprocedural days of any urinary tract procedure, such as flexible ureteroscopy indicated for stone management, etc. A Cochrane review demonstrated the beneficial aspect of urinary tract infection medication - antibiotic prophylaxis in patients assigned to procedures such as cystoscopy, reducing the risk of symptomatic UTI. 
• Renal calculi or bladder stones: Stones display affinity towards bacteria, which can cause recurrent urinary tract infections. Ureteral stones associated with pyelonephritis can increase urosepsis risk.
• Diabetes mellitus: Sugar is a rich enabler of UTI infection, almost doubling it. When combined with obesity, the risk of urinary tract infection is even greater, but it is unclear if obesity is the cause. 
• Immunocompromised status: In procedures such as renal or other solid organ transplant, the risk of urinary tract infection is increased. Nevertheless, human immunodeficiency virus (HIV) infection didn’t demonstrate any influence on the risk of bladder infection symptoms (symptomatic UTI infection), even in low CD4 count cases.
  

In general, there are usually three routes of urinary tract infection by which the organisms gain entry into the urinary tract: 

• The ascending route, 
• The hematogenous (descending), and 
• Lymphatic pathways. 

The female urethra is usually colonized by bacteria believed to originate from the faecal flora (bacteria seen in the stools). The short length of the female urethra and its proximity to the perirectal area enhance the pathogenesis of urinary tract infection by easing the colonization of the urethra. There are various other factors which enhance the colonization of the urethra.

• Modes of contraception: The use of spermicides and diaphragms as methods of contraception can serve as the basis of pathogenesis of urinary tract infection. Although there is evidence in females that bladder infections follow colonization of the urethra, the mode of ascent of the microorganisms is incompletely understood.
• Massaging and sexual intercourse: Massage of the female urethra and sexual intercourse allow bacteria to reach the bladder. Once bacteria have reached the bladder, the organisms quickly multiply and can ascend the ureters to the kidneys. This sequence of events is more likely to occur if vesicoureteral reflux (reflux of urine into the ureters and kidneys while voiding) is present. That UTIs are more common in females than in males because of the anatomic differences in location and length of the urethra tends to support the ascending route of infections as the primary acquisition route.
• Renal infection and hematogenous spread: Infection of the kidney by hematogenous spread (spread through blood) of microorganisms usually occurs as the result of dissemination of organisms from a distant primary infection in the body. Infections via the descending route are uncommon and involve a relatively small number of invasive pathogens. Bacteraemia (bacteria in blood) caused by S. aureus may produce renal abscesses. Additional organisms include Candida spp., Mycobacterium tuberculosis, Salmonella spp., and enterococci. Of particular interest, it is difficult to produce experimental pyelonephritis by intravenously administering common gram-negative organisms such as E. coli and P. aeruginosa. Overall, less than 5% of documented UTIs result from hematogenous spread of microorganisms.
• Renal lymphatic spread: There appears to be little evidence supporting a significant role for renal lymphatics in the pathogenesis of UTIs. There are lymphatic communications between the bowel and kidney, as well as between the bladder and kidney. There is no evidence, however, that microorganisms are transferred to the kidney via this route.
• After bacteria reach the urinary tract, three factors determine the development of infection: the size of the inoculum, the virulence of the microorganism, and the competency of the natural host defense mechanisms. Most UTIs reflect a failure in host defense mechanisms.