Urinary tract infection (UTI) refers to an inflammatory response caused by various pathogens invading the urinary tract epithelium or tissues. Pathogens include bacteria, fungi, mycoplasma, chlamydia, viruses, and parasites. This section primarily focuses on UTIs caused by bacteria, excluding Mycobacterium tuberculosis.

Classification

Classification based on Clinical Symptoms

UTIs can be classified as symptomatic urinary tract infections or asymptomatic bacteriuria. Asymptomatic bacteriuria refers to the presence of true bacteriuria without clinical symptoms.

Classification based on the Site of Infection

UTIs can be divided into upper urinary tract infections (involving the urinary tract above the ureteral orifice) and lower urinary tract infections (involving the urinary tract below the ureteral orifice). The former primarily includes pyelonephritis, while the latter mainly refers to cystitis.

Classification based on the Urinary Tract Condition at the Time of Infection

UTIs can be classified as uncomplicated or complicated. Uncomplicated UTIs primarily occur in women without anatomical or functional abnormalities of the urinary tract or associated comorbidities. Complicated UTIs are associated with risk factors such as male, pregnancy, anatomical or functional abnormalities of the urinary tract, indwelling catheters, diabetes, or other conditions that impair immune function.

Classification based on Frequency of Occurrence

UTIs can be classified as isolated episodes or recurrent UTIs (defined as ≥2 episodes within 6 months or ≥3 episodes within 1 year). Recurrent UTIs can be further divided into reinfections and relapses. Reinfections refer to infections caused by new pathogens, while relapses result from the persistence of the same pathogen causing recurrent episodes.

Epidemiology

Clinically, most UTIs are bacterial in origin. Statistics indicate that approximately 90% of cases present as cystitis, while 10% involve pyelonephritis.

During infancy, the incidence of UTIs is slightly higher in male infants due to a higher prevalence of urethral abnormalities. After childhood, UTIs become more common in females. The male urethra is longer, while the female urethra is shorter and wider, making it easier for pathogens to enter. Additionally, the proximity of the female urethral opening to the anus and vagina increases the risk of contamination from feces and vaginal secretions. Consequently, the incidence of UTIs in females is significantly higher than in males, with 50–80% of females experiencing at least one UTI during their lifetime.

In individuals over 65 years of age, the incidence of UTIs increases due to factors such as diabetes, prostate diseases, and indwelling catheters. The incidence rates in elderly females and males are approximately 20% and 10%, respectively.

UTIs are also one of the most common healthcare-associated infections, most of which are related to indwelling catheters. UTIs are prone to recurrence, with about 27% of patients experiencing another episode within 6 months, and approximately 3% having more than three episodes within the same period.

Etiology

The most common pathogens causing UTIs are Gram-negative bacilli, with Escherichia coli being the most prevalent. In community-acquired infections, approximately 85% are caused by E. coli, followed by other Gram-negative bacilli such as Proteus mirabilis and Klebsiella species, as well as Gram-positive cocci such as Enterococcus and Staphylococcus saprophyticus.

In complicated UTIs, the range of pathogens is more diverse, but Gram-negative bacilli remain the most common. These include E. coli, Klebsiella species, Proteus mirabilis, and Pseudomonas aeruginosa. Gram-positive cocci and, in some cases, fungi are also involved.

Pathogenesis

Routes of Infection

Ascending Infection

Ascending infection refers to the spread of pathogens from the urethra to the bladder, ureters, and renal pelvis, accounting for approximately 95% of UTIs. Under normal conditions, a small number of intestinal flora colonize the vestibule of the vagina and the periurethral area without causing disease. Certain factors, such as sexual activity, urinary obstruction, medical procedures, and genital infections, can lead to ascending infections.

Hematogenous Infection

Hematogenous infection occurs when pathogens invade the bloodstream from an infection site and reach the urinary system through circulation. This route is rare, accounting for less than 2% of cases, and is more common in patients with chronic underlying diseases or those receiving immunosuppressive therapy. Common pathogens include Staphylococcus aureus, Salmonella species, Pseudomonas aeruginosa, and Candida species.

Direct Infection

Direct infection occurs when pathogens invade the urinary system from adjacent tissues or organs with inflammation.

Lymphatic Spread

Lymphatic spread occurs when pathogens from infections in the pelvis or lower abdominal organs spread to the urinary system through lymphatic channels. This route is clinically rare.

Host Defense Mechanisms

Under normal circumstances, pathogens entering the bladder are quickly cleared. A weakened host defense system increases the risk of UTIs. The body's defense mechanisms include:

The protective role of normal vaginal flora in women against pathogenic bacteria.
The flushing effect of urination.
The defensive capabilities of the urethral and bladder mucosa.
Antibacterial factors in urine, including high concentrations of urea, low pH, high osmolality, and organic acids.
Antibacterial components in prostatic fluid.
The natural barrier function of the urethral sphincter.

Predisposing Factors

Urinary Obstruction

Factors that cause impaired urine flow, such as stones, prostatic hyperplasia, strictures, or tumors, can lead to urine retention, making it difficult for bacteria to be flushed out. This allows bacteria to proliferate at sites of urine stasis, leading to infection. Additionally, increased pressure above the obstruction can impair blood supply and reduce mucosal resistance, further predisposing to infection.

Structural Abnormalities of the Urinary System

Conditions such as renal hypoplasia, abnormalities of the renal pelvis and ureters, kidney transplantation, and polycystic kidney disease are predisposing factors for UTIs.

Immunosuppression

Conditions that weaken the immune system, such as diabetes, use of immunosuppressive agents, prolonged bed rest, post-kidney transplantation, severe chronic diseases, AIDS, frailty, and advanced age, increase susceptibility to UTIs.

Gender and Sexual Activity

UTIs are more common in females. During sexual activity, pathogenic bacteria around the urethral opening can be pushed into the urethra and bladder, triggering infection.

Vesicoureteral Reflux (VUR)

The valve mechanism at the intramural segment of the ureter and the mucosa at the bladder opening prevent urine from refluxing from the bladder into the ureters. Functional or structural abnormalities in this mechanism can cause urine to flow backward into the ureters or even the renal pelvis, leading to infection.

Pregnancy

UTIs occur in 2–8% of pregnant women. This is associated with decreased ureteral smooth muscle tone and peristalsis during pregnancy, temporary incompetence of the vesicoureteral valve, and impaired urine drainage caused by uterine enlargement in late pregnancy.

Iatrogenic Factors

Medical procedures such as catheterization, indwelling urinary catheters, cystoscopy, ureteroscopy, or retrograde urography can damage the urinary tract and introduce pathogens into the urinary system, leading to UTIs. The incidence of UTIs after single catheterization is 1–2%, while the infection rate is approximately 50% after one day of indwelling catheterization and over 90% after three days.

Other Factors

Chronic kidney diseases causing renal parenchymal scarring can obstruct urine flow in some nephron units, increasing the risk of UTIs.

Genetic factors, such as host gene mutations, are associated with recurrent UTIs.

Neurogenic bladder contributes to the disease as well.

Bacterial Virulence

The ability of bacteria to adhere to the urothelial cells is closely related to the development of UTIs. Escherichia coli is the most common pathogen causing UTIs, but not all E. coli strains are capable of inducing infection. Its pathogenicity is associated with specific antigenic components.

E. coli possesses O, H, and K antigens, with strains containing a large amount of K antigen being more likely to cause pyelonephritis. Additionally, the P-type and I-type fimbriae on the surface of E. coli play a significant role in its virulence. These fimbriae bind to specific receptors on the surface of urothelial cells, allowing the bacteria to colonize and proliferate in the urinary tract. This process induces apoptosis and shedding of urothelial cells, playing a critical role in the pathogenesis of UTIs.

Pathology

Acute Cystitis

Acute cystitis is primarily characterized by vascular dilation and congestion of the bladder mucosa, epithelial cell swelling, submucosal congestion, edema, and infiltration of inflammatory cells. Severe cases may exhibit punctate or patchy hemorrhages and even mucosal ulcers.

Acute Pyelonephritis

Acute pyelonephritis may affect one or both kidneys. It is characterized by localized or widespread congestion and edema of the renal pelvis and calyces, with the presence of purulent exudate on the surface. Submucosal microabscesses may be observed, along with wedgy inflammatory lesions of varying sizes pointing toward the renal papillae. Within these lesions, tubular epithelial cells may show varying degrees of swelling, necrosis, and shedding. Leukocyte casts can be found in the tubular lumen. The renal interstitium exhibits edema, infiltration of neutrophils, and formation of small abscesses. Severe inflammation may lead to extensive hemorrhage, and larger inflammatory lesions may heal with scar formation. The glomeruli generally remain morphologically unaffected.

Chronic Pyelonephritis

Chronic pyelonephritis is characterized by kidney shrinkage, uneven surfaces, adhesion and deformation of the renal pelvis and calyces, scarring of the renal papillae, tubular atrophy, interstitial lymphomononuclear infiltration, and fibrosis. In advanced stages, glomerulosclerosis may occur.

Clinical Manifestations

Acute Cystitis

Acute cystitis has a sudden onset and is the most common form of UTI in adults. The main symptoms include urinary frequency, urgency, and dysuria (collectively referred to as lower urinary tract symptoms). Patients may also experience suprapubic discomfort, a burning sensation in the urethra, cloudy urine, and occasionally gross hematuria. Systemic symptoms of infection are generally absent.

Pyelonephritis

Acute Pyelonephritis

Urinary Symptoms

Lower urinary tract symptoms, hematuria, and unilateral or bilateral flank pain. Tenderness or percussion pain is evident at the costovertebral angle.

Systemic Symptoms

Chills, high fever, and associated symptoms such as headache, nausea, emesis, and loss of appetite are present.

Chronic Pyelonephritis

Chronic pyelonephritis presents with complex and nonspecific clinical manifestations, with both systemic and local urinary symptoms being atypical. It is often caused by persistent or recurrent UTIs due to factors such as urinary obstruction or structural abnormalities. The main features include nocturia, low specific gravity of urine, and pyuria. Patients may also experience low-grade fever and varying degrees of dull lower back pain. Prolonged disease progression can lead to chronic renal failure.

Asymptomatic Bacteriuria (ASB)

Patients with ASB exhibit true bacteriuria but lack any clinical symptoms or signs. The diagnosis is based on urine culture results.

Complicated Urinary Tract Infections

Complicated UTIs are often associated with structural or functional abnormalities of the urinary system or underlying systemic diseases. These infections are more difficult to treat, have a higher risk of treatment failure, and, in severe cases, may progress to systemic or severe infections.

Complications

When UTIs are treated promptly, complications are rare. However, in cases of complicated UTIs, particularly in patients with underlying conditions such as diabetes, delayed or inappropriate treatment can lead to severe complications.

Renal Papillary Necrosis

Renal papillary necrosis refers to ischemic necrosis of the renal papillae and adjacent renal medulla. The main manifestations include chills, high fever, severe flank or abdominal pain, and hematuria. Patients may also develop concurrent septicemia and/or acute kidney injury.

Perinephric Abscess

Severe pyelonephritis may lead to the formation of perinephric abscesses. In addition to worsening of existing symptoms, patients often experience significant unilateral flank pain, which intensifies when bending toward the unaffected side. Diagnostic imaging techniques such as ultrasound, abdominal X-rays, CT, and MRI can aid in diagnosis.

Urosepsis

Urosepsis refers to sepsis caused by urinary tract infections. Its clinical manifestations include chills, high fever, systemic inflammatory response, and organ dysfunction. Severe cases may progress to septic shock, which can be life-threatening. Common risk factors include advanced age, diabetes, use of immunosuppressive agents, urinary obstruction, indwelling urinary catheters, or urological surgeries.

Laboratory and Auxiliary Examinations

Urine Tests

Macroscopic Observation

The urine appears cloudy, which has high sensitivity but low specificity for diagnosing symptomatic urinary tract infections.

Routine Urinalysis

Findings may include pyuria, hematuria, and proteinuria. Leukocyte esterase is often positive. A positive urine nitrite reduction test is commonly seen in urinary tract infections caused by Gram-negative bacteria such as Escherichia coli. Microscopic examination of urine sediment showing leukocyte counts >5/HPF is indicative of pyuria or purulent urine and is significant for diagnosing urinary tract infections. Some patients may have microscopic hematuria, which is typically characterized by uniform red blood cells. Gross hematuria can occur in cystitis, and white blood cell casts may be observed in the urine of some patients with pyelonephritis.

Urine Bacteriological Examination

Urine Bacterial Smear

A clean midstream urine sediment smear showing more than 1 bacterium/HPF suggests a urinary tract infection. This method is simple, with a detection rate of 80–90%. It provides preliminary information on the presence of bacteria and their types, offering valuable guidance for selecting appropriate antibiotics.

Urine Culture

Urine culture is the key method for diagnosing urinary tract infections. Clean midstream urine, catheterized urine, or bladder puncture urine should be collected before treatment for bacterial culture. Among these, bladder puncture is the most accurate sampling method but is invasive, so clean midstream urine is most commonly used in clinical practice. False-positive and false-negative results may occur in urine cultures.

False positives are primarily due to:

Improper collection of clean midstream urine, leading to contamination.
Urine samples not stored or transported at low temperatures and left for more than one hour.

False negatives are primarily due to:

Recent antibiotic use within the past 7 days.
Insufficient bladder retention time of urine (less than 2 hours).
Excessive water intake, diluting the urine.
Intermittent bacterial shedding from the infection site.
Contamination of the urine sample with disinfectants during collection.

Criteria for true bacteriuria include any of the following:

Bacterial counts >1/HPF in clean midstream urine sediment smear.
Positive bacterial culture from bladder puncture urine.
Bacterial count ≥10⁵ CFU/ml in clean midstream urine culture (CFU refers to colony-forming units).

Blood Tests

In acute pyelonephritis, blood tests may show elevated white blood cell counts, often with an increase in neutrophils. Erythrocyte sedimentation rate (ESR) may be accelerated, and levels of C-reactive protein (CRP), procalcitonin, and interleukin-6 (IL-6) are often elevated. In cases of urosepsis, blood cultures may yield positive results. In chronic pyelonephritis with impaired renal function, decreased glomerular filtration rate and elevated serum creatinine levels may be observed.

Imaging Studies

In cases of recurrent urinary tract infections or suspected urinary system abnormalities, such as structural anomalies, stones, or obstructions, imaging studies are warranted. Ultrasound of the urinary system is the first-choice diagnostic tool. Additional imaging modalities such as abdominal X-rays, urinary system CT or MRI, intravenous urography, and renal static imaging can provide detailed information on the urinary tract and help identify factors contributing to recurrent or persistent infections, such as stones, obstructions, reflux, or malformations. Intravenous urography or cystoscopy is not recommended for women with uncomplicated cystitis.

Diagnosis

Diagnosis of Urinary Tract Infections (UTIs)

The diagnosis of a UTI is based on clinical symptoms and signs, in conjunction with findings from routine urinalysis and urine bacteriological examination. True bacteriuria is a definitive indicator of a UTI. In cases of acute uncomplicated cystitis, symptoms such as lower urinary tract irritation (e.g., dysuria, frequency, urgency) or suprapubic discomfort, along with a clean midstream urine culture showing ≥10³ CFU/ml, confirm the diagnosis of a UTI. For acute uncomplicated pyelonephritis, symptoms such as chills, fever, and flank pain, combined with a clean midstream urine culture showing ≥10⁴ CFU/ml, are diagnostic. Asymptomatic bacteriuria requires two consecutive clean midstream urine cultures with the same bacterial species, each showing ≥10⁵ CFU/ml, for diagnosis. In women with significant lower urinary tract symptoms, increased urinary leukocytes, and a clean midstream urine culture showing ≥10² CFU/ml of a common pathogen, a presumptive diagnosis of a UTI can also be made.

The diagnosis of complicated UTIs involves two criteria:

A clean midstream urine culture showing ≥10⁵ CFU/ml.
The presence of structural or functional abnormalities of the urinary system, or underlying conditions that predispose to infection.

For UTIs that respond poorly to treatment or recur frequently, it is necessary to investigate potential contributing factors such as urinary tract malformations, obstructions, diabetes, or other conditions that compromise host immunity.

Localization

Localization based on Clinical Symptoms

Lower urinary tract infections are associated with symptoms such as lower urinary tract irritation and suprapubic discomfort, and may include gross hematuria. Upper urinary tract infections, in addition to lower urinary tract symptoms, often present with systemic symptoms such as chills, fever, flank pain, nausea, and vomiting.

Localization based on Laboratory Findings

Upper urinary tract infections are suggested by the following:

Positive urine culture after ureteral catheterization or bladder irrigation.
Presence of white blood cell casts in urine sediment microscopy, after excluding conditions such as interstitial nephritis or lupus nephritis.
Evidence of impaired tubular function.
Blood test findings such as elevated white blood cell and neutrophil counts, increased C-reactive protein levels, and positive blood cultures.

Diagnosis of Chronic Pyelonephritis

Differentiating between acute and chronic pyelonephritis requires a history of recurrent UTIs along with findings from imaging and renal function tests:

Uneven renal contours and asymmetry in kidney size.
Deformity or narrowing of the renal pelvis and calyces on intravenous pyelography.
Persistent impairment of tubular interstitial function.

A diagnosis of chronic pyelonephritis can be made when any one of the first two criteria is present along with the third.

Differential Diagnosis of UTIs

Urethral Syndrome

Urethral syndrome is more common in females and presents with lower urinary tract irritation symptoms, but multiple tests fail to demonstrate true bacteriuria. It may be related to dysfunction of the detrusor and bladder sphincter, gynecological or perianal diseases, or psychological factors such as anxiety. Infections caused by Chlamydia or Mycoplasma should also be excluded.

Urinary Tuberculosis

Urinary tuberculosis is characterized by more pronounced urinary irritation symptoms, resistance to conventional antibiotic therapy, and the presence of acid-fast bacilli in urine sediment. Urine culture for Mycobacterium tuberculosis is positive, while routine bacterial cultures are negative. Intravenous pyelography may show findings such as moth-eaten defects in the renal parenchyma. Some patients may have concomitant extrapulmonary tuberculosis. Effective anti-tuberculosis treatment aids in differentiation. Cases unresponsive to antibiotics should raise suspicion of urinary tuberculosis.

Chronic Glomerulonephritis

Chronic pyelonephritis with renal dysfunction and hypertension should be differentiated from chronic glomerulonephritis. The latter typically involves bilateral kidney involvement, with glomerular dysfunction being more prominent than tubular dysfunction. It is often associated with significant proteinuria, hematuria, and a history of edema. In contrast, chronic pyelonephritis often presents with lower urinary tract irritation symptoms, positive findings in urine bacteriological tests, and imaging evidence of asymmetrical kidney shrinkage.

Inflammation of Adjacent Organs

Conditions such as vaginitis, cervicitis, genital ulcers, or gonorrhea can be distinguished through gynecological examination and analysis of secretions. In men, prostatitis or benign prostatic hyperplasia should be considered. Some UTIs may present with abdominal pain, fever, and elevated white blood cell counts, necessitating differentiation from conditions such as acute appendicitis or acute pelvic inflammatory disease. A combination of medical history, physical examination, routine urinalysis, urine bacteriological tests, and imaging studies can aid in differentiation.

Treatment

General Treatment

General treatment includes symptomatic management, alkalization of urine, increased fluid intake, and frequent urination. For patients with recurrent urinary tract infections, it is necessary to identify the underlying causes and eliminate predisposing factors promptly.

Antimicrobial Therapy

Clean midstream urine culture combined with antibiotic susceptibility testing not only aids in confirming the diagnosis but also guides the selection of antibiotics.

Principles of Antibiotic Use

Antibiotics should be selected based on their sensitivity to the causative pathogens. For initial episodes of UTIs, antibiotics effective against Gram-negative bacilli are preferred before urine culture and susceptibility test results are available. If symptoms do not improve after three days of treatment, adjustments should be made according to susceptibility test results.

Antibiotics with high concentrations in urine and renal tissues are preferred.

Antibiotics with low nephrotoxicity and minimal side effects should be chosen, and dosages should be adjusted based on liver and kidney function.

Combination therapy is recommended in cases of treatment failure with single agents, severe infections, mixed infections, or infections caused by resistant bacteria.

The choice of antibiotic type, dosage, and treatment duration should be tailored to the specific type of UTI.

Commonly used antibiotics include sulfonamides, β-lactams (penicillins and cephalosporins), and fluoroquinolones (e.g., norfloxacin, ofloxacin).

Treatment for Different Types of UTIs

Acute Cystitis

The goal of treatment is to eradicate the causative pathogens, relieve symptoms, and prevent the spread of infection. For women with uncomplicated cystitis, oral antibiotics are recommended, with the following approaches:

Single-Dose Therapy: For initial episodes, a single high-dose antibiotic may be used. Common options include trimethoprim/sulfamethoxazole (TMP-SMZ) 320 mg/1600 mg as a single dose or fosfomycin trometamol 3 g as a single dose. While single-dose therapy has fewer side effects and better compliance, it has a higher recurrence rate and is less effective than short-course therapy.
Short-Course Therapy: First-line treatments include nitrofurantoin 50–100 mg three times daily for five days, TMP-SMZ 160 mg/800 mg twice daily for three days, or pivmecillinam 0.4 g twice daily for 3–5 days. Alternative regimens include levofloxacin (0.5 g once daily for three days) or second-generation cephalosporins (e.g., cefuroxime axetil, cefaclor). Compared to single-dose therapy, short-course therapy is more effective and reduces the recurrence rate of UTIs, making it the currently recommended approach.
Seven-Day Therapy: This longer regimen is suitable for pregnant women, the elderly, patients with diabetes, immunocompromised individuals, and male patients. Antimicrobial treatment is continued for seven days.

Regardless of the regimen, a urine culture should be performed seven days after discontinuing antibiotics. A negative result indicates that acute cystitis has been cured, while persistent bacteriuria requires continued antibiotic therapy for a total of two weeks.

Pyelonephritis

The treatment of acute pyelonephritis aims to eradicate pathogens, prevent and control sepsis, and reduce the risk of recurrence. Since the renal interstitium is often involved, with a risk of bacteremia, antibiotics with high concentrations in urine, renal tissues, and blood should be used. After obtaining urine samples for bacteriological testing, antibiotics effective against Gram-negative bacilli should be initiated immediately. If the treatment shows efficacy within 72 hours, no change in antibiotics is necessary; otherwise, adjustments should be made based on susceptibility test results.

Mild Cases: Oral antibiotic therapy typically shows efficacy within 2–3 days. The choice of antibiotics should be evaluated based on clinical outcomes and urine culture results, with a treatment duration of 7–14 days. Common options include fluoroquinolones (e.g., ciprofloxacin 0.5 g twice daily or levofloxacin 0.5 g once daily), semi-synthetic penicillins (e.g., amoxicillin-clavulanate 0.457 g twice daily), cephalosporins (e.g., cefuroxime axetil 0.25 g twice daily), or TMP-SMZ 160 mg/800 mg twice daily. If urine culture remains positive after 14 days of treatment, effective antibiotics should be selected based on susceptibility results for an additional 4–6 weeks.
Severe Cases with Systemic Toxicity: Hospitalization and intravenous antibiotic therapy are required. Commonly used antibiotics include ciprofloxacin 0.4 g twice daily, levofloxacin 0.5 g once daily, cefotaxime 2 g three times daily, ceftriaxone 1–2 g once daily, ceftazidime 2 g twice daily, or piperacillin-tazobactam 2.25–4.5 g three times daily. Carbapenems or combination therapy may be necessary in certain cases. For severe infections caused by Gram-positive cocci, empirical vancomycin therapy is recommended. Aminoglycosides, due to their nephrotoxicity, should be used with caution. If symptoms improve, intravenous antibiotics can be continued for three days after the resolution of fever, followed by oral antibiotics to complete a two-week course. If there is no improvement in 72 hours, antibiotics should be adjusted based on susceptibility results. Persistent fever despite treatment warrants attention to potential complications of pyelonephritis. Chronic pyelonephritis is often associated with complicated UTIs. The key to treatment is identifying and eliminating predisposing factors. The principles for managing acute exacerbations of chronic pyelonephritis are the same as for acute pyelonephritis.
Urosepsis: Urosepsis has a high mortality rate and can progress rapidly. For suspected cases, broad-spectrum intravenous antibiotics and early fluid resuscitation are necessary. Antibiotics should be adjusted based on urine culture and susceptibility results. Urinary tract obstruction is the most common predisposing factor, and relieving the obstruction is critical.
Recurrent UTIs: Acute episodes should be treated in the same manner as the initial infection. Anatomical or functional abnormalities of the urinary system should be evaluated, and predisposing factors should be addressed. Empirical short-course therapy may be used initially, followed by targeted therapy based on urine culture and susceptibility results. Preventive measures after the acute phase include increased fluid intake, frequent urination, local application of estrogen in postmenopausal women, single-dose antibiotic use after sexual activity, or prolonged low-dose antibiotic prophylaxis to prevent recurrence.

Treatment of Other Types of Urinary Tract Infections

Asymptomatic Bacteriuria

There is ongoing debate regarding the treatment of asymptomatic bacteriuria. Asymptomatic bacteriuria does not require routine screening or treatment in premenopausal and non-pregnant women, the elderly, patients with diabetes, spinal cord injuries, indwelling catheters, or children. However, screening and treatment are recommended in the following situations:

Pregnant women
Patients scheduled for urological surgery that may damage the mucosa

In these cases, antibiotics can be selected based on susceptibility testing, with a preference for short-course therapy.

Urinary Tract Infections During Pregnancy

For acute cystitis during pregnancy, nitrofurantoin or cephalosporins can be used for 3–7 days. Acute pyelonephritis requires intravenous antibiotic therapy, with third-generation cephalosporins preferred for empirical treatment. Antibiotics should then be adjusted based on susceptibility results to select agents that are effective and safe for the fetus, with a treatment duration of two weeks. For recurrent UTIs, long-term, low-dose nitrofurantoin prophylaxis may be used.

Pediatric Urinary Tract Infections

Pediatric UTIs should be managed in conjunction with imaging studies to rule out congenital abnormalities of the urinary system. Antibiotic therapy should begin simultaneously with urine culture collection. The choice of antibiotics is similar to that in adults, but fluoroquinolones are generally avoided due to their potential effects on cartilage development. Dosages should be adjusted based on body weight.

Catheter-Associated Urinary Tract Infections (CAUTIs)

The use of indwelling catheters should be minimized, and the duration of catheterization should be shortened when indicated. Regular catheter replacement may reduce the incidence of UTIs. However, bladder irrigation with antibiotics or saline has no significant preventive effect and may increase the risk of infection.

Most cases of asymptomatic catheter-associated bacteriuria do not require antibiotic treatment. Patients with significant systemic symptoms, such as chills and fever, should be managed as cases of complicated UTIs.

Diabetes-Associated Urinary Tract Infections

The treatment of UTIs in diabetic patients involves strict glycemic control and the rational use of antibiotics. Asymptomatic bacteriuria in diabetic women does not require antibiotic therapy. Severe UTIs in diabetic patients may require combination antibiotic therapy and intravenous administration. Diabetic patients with upper urinary tract infections have a higher risk of renal papillary necrosis. Clinical manifestations such as high fever, severe flank pain, and hematuria, particularly when accompanied by renal colic or the passage of necrotic tissue in the urine, should raise suspicion for renal papillary necrosis. Enhanced antibiotic therapy and the relief of urinary obstruction are essential in such cases.

Complicated Urinary Tract Infections

For UTIs with complicating factors, treatment should involve a 14-day or longer course of antibiotics, along with efforts to eliminate predisposing factors and manage comorbidities. A urine culture should be performed two weeks after completing treatment to confirm the eradication of bacteria.

Evaluation of Treatment Efficacy

Cure

A cure is defined by the resolution of symptoms and negative urine culture results. Follow-up urine cultures at two weeks and six weeks after completing treatment should also remain negative.

Treatment Failure

Treatment failure is indicated by persistent bacteriuria after therapy, or when bacteriuria initially resolves but recurs with the same strain at follow-up urine cultures in two or six weeks.

Prognosis and Prevention

For patients with uncomplicated UTIs, the overall prognosis is favorable with timely treatment. However, complicated UTIs have lower clinical cure rates, a higher likelihood of recurrence, and require efforts to eliminate predisposing factors. Elderly patients, those with diabetes or other underlying conditions, and individuals on immunosuppressive therapy have an increased risk of urosepsis. The prognosis of urosepsis is poor, with a mortality rate of approximately 30%. If sepsis caused by Gram-negative bacilli is resistant to empirical therapy, the mortality rate increases significantly.

Prevention is key in managing UTIs. Practices such as maintaining adequate hydration, frequent urination, proper perineal hygiene, avoiding the use of urological instruments, adhering to strict aseptic techniques, and reducing the frequency and duration of indwelling catheter use can lower the incidence of UTIs. For patients with vesicoureteral reflux, "double voiding" (urinating again a few minutes after the initial void) is recommended. Efforts should focus on eliminating or mitigating complicating factors to prevent recurrent UTIs.