Kidney and Urinary Tract Infections: Symptoms, Causes & Treatment Guide

What Is a Urinary Tract Infection?

A urinary tract infection (UTI) is a bacterial infection affecting any part of the urinary system, including the kidneys, ureters, bladder, and urethra. Most UTIs involve the lower urinary tract (bladder and urethra) and are caused by Escherichia coli (E. coli) bacteria, which normally live in the intestines. UTIs are classified as uncomplicated (occurring in healthy individuals) or complicated (associated with structural abnormalities, catheters, or underlying conditions).

The urinary system is designed to keep bacteria out through several defense mechanisms. Urine flows in one direction from the kidneys to the bladder and out through the urethra, flushing bacteria along the way. The bladder wall and urine itself contain antibacterial properties that help prevent infection. However, when bacteria successfully enter the urinary tract and multiply, an infection develops.

Urinary tract infections represent one of the most common bacterial infections encountered in clinical practice. According to the World Health Organization, UTIs account for approximately 150 million cases globally each year, resulting in significant healthcare costs and impact on quality of life. The economic burden is substantial, with billions spent annually on diagnosis, treatment, and management of complications.

Understanding the anatomy helps explain why infections occur. The urinary tract consists of two kidneys that filter blood and produce urine, two ureters that carry urine from the kidneys to the bladder, the bladder that stores urine, and the urethra through which urine exits the body. Infections can affect any of these structures, with different symptoms and severity depending on the location.

Types of Urinary Tract Infections

UTIs are categorized based on their location and complexity. Lower urinary tract infections include cystitis (bladder infection) and urethritis (urethra infection), which typically cause uncomfortable but manageable symptoms. Upper urinary tract infections involve the kidneys (pyelonephritis) and are more serious, potentially leading to permanent kidney damage or life-threatening sepsis if untreated.

The distinction between uncomplicated and complicated UTIs is clinically important. Uncomplicated UTIs occur in healthy, non-pregnant women with normal urinary tract anatomy. Complicated UTIs occur in men, pregnant women, children, or anyone with structural abnormalities, kidney disease, diabetes, immunosuppression, or urinary catheters. Complicated infections require longer treatment courses and closer monitoring.

Who Gets Urinary Tract Infections?

While anyone can develop a UTI, certain populations face significantly higher risk. Women are disproportionately affected due to anatomical differences – the female urethra is only about 4 centimeters long compared to approximately 20 centimeters in men, providing bacteria a shorter path to the bladder. Sexual activity, pregnancy, menopause, and certain contraceptive methods further increase risk in women.

Men typically develop UTIs less frequently but face higher risk after age 50 due to prostate enlargement, which can impede urinary flow. Elderly individuals of both sexes experience increased UTI rates due to age-related changes in bladder function, weakened immune responses, and higher rates of catheter use. Children can also develop UTIs, with recurrent infections sometimes indicating underlying anatomical abnormalities.

What Are the Symptoms of a UTI?

Common UTI symptoms include a persistent urge to urinate, burning sensation during urination, passing frequent small amounts of urine, cloudy or strong-smelling urine, and pelvic pain. Kidney infections add symptoms like high fever, chills, severe back or flank pain, nausea, and vomiting. The severity and combination of symptoms help distinguish between lower and upper urinary tract infections.

The symptoms of a urinary tract infection vary depending on which part of the urinary system is affected. Recognizing these symptoms early enables prompt treatment and prevents progression to more serious infections. Many people experience their first UTI without knowing what the symptoms mean, leading to delays in seeking appropriate care.

Lower urinary tract symptoms predominantly relate to bladder irritation and dysfunction. The bladder becomes inflamed and hypersensitive, triggering frequent urination signals even when little urine is present. This inflammation also causes the characteristic burning or stinging sensation during urination, medically termed dysuria. The discomfort may persist after urination completes.

The nature of the urine itself often changes with infection. Bacteria and white blood cells fighting the infection create cloudiness, while bacterial metabolites produce unusual odors. Blood may appear in the urine (hematuria), ranging from slight pink discoloration to visible red. Any blood in urine warrants medical evaluation, as it can also indicate other conditions.

Symptoms of Bladder Infection (Cystitis)

Bladder infections typically produce localized symptoms without systemic illness. The hallmark triad includes dysuria (painful urination), frequency (urinating more often than usual), and urgency (sudden, compelling need to urinate). Many patients describe feeling like they cannot completely empty their bladder, leading to multiple bathroom trips that produce only small amounts of urine.

Suprapubic pain or pressure – discomfort in the lower abdomen just above the pubic bone – commonly accompanies cystitis. This pain may be constant or intensify during urination. Some patients experience pelvic heaviness or pressure. While uncomfortable, these symptoms rarely include fever, which helps distinguish cystitis from kidney infection.

• Frequent urination: Needing to urinate more often than usual, sometimes every few minutes
• Burning sensation: Pain or stinging during urination that may persist afterward
• Urgency: Sudden, intense need to urinate that's difficult to delay
• Cloudy urine: Urine appears murky rather than clear due to bacteria and white blood cells
• Strong odor: Urine smells unusually strong or unpleasant
• Lower abdominal discomfort: Pressure or pain in the pelvic region

Symptoms of Kidney Infection (Pyelonephritis)

Kidney infections represent a significant escalation in severity and require prompt medical attention. When bacteria ascend from the bladder to the kidneys, the body mounts a systemic inflammatory response. High fever (often exceeding 101°F/38.5°C), shaking chills, and general malaise indicate the infection has progressed beyond the bladder.

Back or flank pain distinguishes kidney infections from simple cystitis. The kidneys are located in the upper back, just below the ribcage on either side of the spine. Pain from pyelonephritis typically affects one side and may be severe enough to limit movement. The pain often worsens with percussion (tapping) over the affected kidney area, a clinical sign called costovertebral angle tenderness.

Gastrointestinal symptoms frequently accompany kidney infections. Nausea and vomiting result from the systemic inflammatory response and may complicate treatment by preventing oral medication absorption. Decreased appetite and general weakness are common. Some patients experience confusion or altered mental status, particularly elderly individuals, signaling potential sepsis.

Symptoms in Special Populations

UTI symptoms can present differently in certain groups, making diagnosis more challenging. Elderly patients may not develop typical symptoms like dysuria or fever. Instead, they might experience sudden confusion, agitation, falls, or general decline in function. Any unexplained change in mental status in an older adult should prompt consideration of UTI.

Children, particularly infants, cannot communicate typical UTI symptoms. Parents should watch for unexplained fever, irritability, poor feeding, vomiting, or failure to thrive. Older children might complain of abdominal pain rather than typical urinary symptoms. Any unexplained fever in young children warrants urine testing.

What Causes Urinary Tract Infections?

UTIs are primarily caused by bacteria entering the urinary tract through the urethra and multiplying in the bladder. Escherichia coli (E. coli) from the intestinal tract causes 80-90% of uncomplicated UTIs. Other bacterial causes include Staphylococcus saprophyticus, Klebsiella, Proteus, and Enterococcus species. Risk factors include female anatomy, sexual activity, menopause, catheter use, urinary obstruction, and immunosuppression.

Understanding what causes urinary tract infections helps explain prevention strategies and why certain individuals are more susceptible. The vast majority of UTIs result from bacteria that normally inhabit the gastrointestinal tract gaining access to the urinary system. This occurs through the ascending route, meaning bacteria travel up the urethra to reach the bladder and potentially the kidneys.

E. coli possesses specific virulence factors that enable urinary tract infection. These bacteria have surface structures called fimbriae or pili that allow them to adhere to the cells lining the urinary tract. Once attached, bacteria cannot be easily flushed away by urination. They then multiply rapidly in the warm, nutrient-rich environment of the bladder, establishing infection.

The body's defense mechanisms normally prevent infection despite constant exposure to potential pathogens. Regular, complete bladder emptying flushes bacteria before they can establish infection. The bladder wall produces protective substances and immune cells respond to bacterial invasion. Infection occurs when these defenses are overwhelmed or compromised.

Risk Factors for UTI

Anatomical factors significantly influence UTI risk. The short female urethra provides bacteria easy access to the bladder. The urethral opening's proximity to the vagina and rectum increases exposure to bacteria from these areas. Any condition that prevents complete bladder emptying allows bacteria more time to multiply, including enlarged prostate in men, pregnancy, and neurological conditions.

Sexual activity represents a major risk factor for UTIs in women. Intercourse can introduce bacteria into the urethra and massage them toward the bladder. Certain contraceptive methods increase risk – spermicides alter vaginal flora, promoting E. coli growth, while diaphragms can press against the urethra and impede complete bladder emptying.

Hormonal changes associated with menopause substantially increase UTI susceptibility. Declining estrogen levels cause thinning of vaginal and urethral tissues, reducing local defense mechanisms. The vaginal pH changes, altering the protective bacterial flora. Postmenopausal women experience UTIs two to three times more frequently than premenopausal women.

Less Common Causes

While bacterial infection causes most UTIs, other organisms occasionally cause urinary tract infections. Fungal UTIs, typically caused by Candida species, occur mainly in hospitalized patients with catheters, diabetes, or immunosuppression. Viral infections of the urinary tract are rare but can occur. Sexually transmitted infections like Chlamydia and gonorrhea can cause urethritis with similar symptoms.

Structural abnormalities predispose to complicated UTIs. Kidney stones create niches where bacteria can hide from antibiotics and the immune system. Urinary tract obstruction from any cause prevents complete emptying and promotes bacterial growth. Vesicoureteral reflux, where urine flows backward from the bladder to the kidneys, allows bladder bacteria to reach the kidneys directly.

How Are UTIs Diagnosed?

UTI diagnosis typically involves urinalysis and urine culture. Urinalysis detects white blood cells, red blood cells, bacteria, and nitrites indicating infection. Urine culture identifies the specific bacteria and determines antibiotic sensitivity. For recurrent or complicated UTIs, additional tests may include kidney ultrasound, CT scan, or cystoscopy to identify underlying causes.

Accurate diagnosis of urinary tract infections requires proper sample collection and appropriate testing. While symptoms often suggest UTI, confirmation through laboratory testing ensures appropriate treatment and distinguishes UTIs from other conditions with similar presentations. The diagnostic approach varies based on infection severity, patient factors, and recurrence patterns.

Proper urine sample collection critically affects test accuracy. Midstream clean-catch technique involves cleaning the genital area, beginning to urinate into the toilet, then collecting the sample mid-stream. This minimizes contamination from skin bacteria. In some situations, catheterization may be necessary to obtain an uncontaminated sample, particularly in hospitalized patients or those unable to provide clean-catch samples.

Urinalysis

Urinalysis provides rapid initial assessment using dipstick tests and microscopic examination. Dipstick testing detects leukocyte esterase (an enzyme from white blood cells) and nitrites (produced when bacteria convert urinary nitrates). Positive results for both markers strongly suggest bacterial UTI, while negative results make UTI unlikely but don't completely exclude it.

Microscopic examination quantifies white blood cells (pyuria), red blood cells, and bacteria in the urine. Significant pyuria, defined as more than 10 white blood cells per high-power field, indicates urinary tract inflammation. However, pyuria alone doesn't confirm infection, as it can occur with kidney stones, interstitial cystitis, or other inflammatory conditions.

Urine Culture

Urine culture remains the gold standard for UTI diagnosis, identifying the specific bacterial species and determining antibiotic susceptibility. A sample is placed on growth media and incubated for 24-48 hours. Significant bacteriuria, typically defined as more than 100,000 colony-forming units per milliliter (CFU/mL), confirms infection in symptomatic patients.

Culture results guide antibiotic selection and are particularly important for complicated or recurrent infections, treatment failures, and before invasive urological procedures. While awaiting culture results (which take 1-2 days), empiric antibiotic therapy based on local resistance patterns is typically initiated for symptomatic patients.

Additional Diagnostic Tests

Imaging studies help evaluate complicated, recurrent, or treatment-resistant infections. Kidney ultrasound can detect stones, obstruction, or structural abnormalities without radiation exposure. CT urography provides detailed imaging of the entire urinary tract and is preferred when kidney stones or masses are suspected.

Cystoscopy involves inserting a thin camera through the urethra to directly visualize the bladder lining. This procedure helps evaluate recurrent infections, especially when interstitial cystitis, bladder tumors, or anatomical abnormalities are suspected. It's not routinely performed for uncomplicated UTIs.

How Are Urinary Tract Infections Treated?

UTIs are primarily treated with antibiotics. Uncomplicated bladder infections typically require 3-7 days of treatment with nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin. Kidney infections require 7-14 days of antibiotics and may need hospitalization. Pain relief, increased fluid intake, and avoiding irritants support recovery. Treatment choice depends on infection type, local resistance patterns, and patient factors.

Treatment of urinary tract infections aims to eliminate the infection, relieve symptoms, and prevent complications. The approach depends on whether the infection involves the bladder (uncomplicated cystitis), kidneys (pyelonephritis), or occurs in patients with complicating factors. Prompt, appropriate treatment prevents the significant morbidity associated with complicated or untreated infections.

Antibiotic selection considers several factors including the likely causative organism, local antibiotic resistance patterns, patient allergies, kidney function, and potential drug interactions. Empiric therapy is started based on these factors before culture results are available. Adjustments may be made once specific bacteria and sensitivities are identified.

Completing the full prescribed antibiotic course is essential even when symptoms improve quickly, which often occurs within 1-2 days. Stopping antibiotics early allows surviving bacteria to repopulate and potentially develop resistance. Treatment duration varies by infection type and antibiotic choice, ranging from single-dose therapy to two weeks for complicated infections.

Treatment for Bladder Infections

Uncomplicated cystitis in healthy, non-pregnant women responds well to short-course antibiotic therapy. First-line options include nitrofurantoin (5-7 days), trimethoprim-sulfamethoxazole (3 days), or a single dose of fosfomycin. These antibiotics concentrate effectively in urine and have favorable safety profiles. Fluoroquinolones, while effective, are reserved for other infections due to concerns about resistance and side effects.

Supportive measures enhance treatment and comfort. Increased fluid intake helps flush bacteria from the urinary tract and dilute urine, reducing irritation. Pain medications like phenazopyridine provide symptomatic relief from dysuria (though it turns urine orange). Heating pads applied to the lower abdomen can ease discomfort. Avoiding caffeine, alcohol, and spicy foods may reduce bladder irritation.

Treatment for Kidney Infections

Pyelonephritis requires more intensive treatment than bladder infections. Oral antibiotics for 7-14 days may suffice for mild cases in otherwise healthy individuals who can tolerate oral medications. Fluoroquinolones (ciprofloxacin, levofloxacin) or trimethoprim-sulfamethoxazole are common choices, though increasing resistance limits their effectiveness in some regions.

Hospitalization is necessary for patients with severe symptoms (high fever, severe pain, dehydration), inability to take oral medications due to vomiting, suspected sepsis, pregnancy, or significant underlying health conditions. Intravenous antibiotics provide reliable drug levels and are continued until fever resolves and the patient can transition to oral therapy.

Follow-up urine cultures after treatment completion help confirm eradication, particularly for complicated infections. Imaging studies may be warranted to exclude abscess formation or other complications. Patients who don't respond as expected to appropriate therapy need evaluation for resistant organisms, abscess, or obstruction.

Managing Recurrent UTIs

Recurrent UTIs, defined as three or more infections within 12 months or two within 6 months, require a comprehensive management strategy. Investigation to identify underlying causes (incomplete emptying, stones, anatomical abnormalities) guides specific interventions. Behavioral modifications including adequate hydration, regular voiding, and post-coital urination form the foundation of prevention.

Prophylactic approaches include continuous low-dose antibiotics (daily or three times weekly), post-coital antibiotics for sexually associated infections, or patient-initiated therapy at symptom onset for women who can reliably recognize their infections. Vaginal estrogen therapy benefits postmenopausal women by restoring normal vaginal flora and tissue integrity.

How Can You Prevent Urinary Tract Infections?

Prevention strategies include drinking adequate fluids (6-8 glasses daily), urinating when needed and completely emptying the bladder, wiping front to back, urinating before and after sexual activity, avoiding irritating feminine products, and wearing breathable cotton underwear. For recurrent infections, prophylactic antibiotics, vaginal estrogen, or cranberry products may help.

Preventing urinary tract infections, particularly recurrent episodes, significantly improves quality of life and reduces healthcare utilization. Prevention strategies target the mechanisms by which bacteria enter and establish infection in the urinary tract. While not all UTIs are preventable, consistent adherence to prevention measures substantially reduces risk.

Hydration plays a central role in UTI prevention. Adequate fluid intake increases urine production, promoting regular bladder flushing that removes bacteria before they can multiply. Water is the optimal choice, while limiting caffeine and alcohol reduces bladder irritation. Clear or light yellow urine color indicates adequate hydration.

Behavioral modifications address common risk factors. Urinating when the urge arises rather than holding urine allows regular bacterial flushing. Complete bladder emptying is important – taking time to fully void and relaxing pelvic muscles helps. Double voiding (urinating, waiting a moment, then urinating again) may benefit those with incomplete emptying.

Hygiene Practices

Proper hygiene significantly reduces bacterial introduction into the urethra. Wiping from front to back after bowel movements prevents transferring intestinal bacteria toward the urethra. Cleaning the genital area before and after intercourse reduces bacterial load. Avoiding douches, powders, and scented feminine products maintains healthy vaginal flora that competes with pathogenic bacteria.

Clothing choices affect the periurethral environment. Cotton underwear allows better air circulation and moisture wicking compared to synthetic materials. Avoiding tight-fitting pants reduces moisture accumulation. Changing out of wet swimwear or exercise clothes promptly removes the warm, moist environment that promotes bacterial growth.

Sexual Activity Considerations

For women with UTIs related to sexual activity, specific measures help prevent infection. Emptying the bladder before and after intercourse flushes bacteria that may have been introduced. Adequate lubrication, using water-based products if needed, reduces friction and tissue trauma. Avoiding spermicides, particularly with diaphragms, reduces UTI risk.

For women with recurrent sexually-associated UTIs who have tried behavioral measures without success, post-coital antibiotic prophylaxis (a single dose after intercourse) is highly effective. This approach minimizes total antibiotic exposure while providing targeted prevention.

Non-Antibiotic Prevention Options

Cranberry products have been extensively studied for UTI prevention. Cranberries contain proanthocyanidins (PACs) that may prevent E. coli from adhering to urinary tract cells. Evidence suggests modest benefit for recurrent UTI prevention, though optimal dosing remains unclear. Cranberry capsules or tablets provide more consistent PAC concentrations than juice.

D-mannose, a naturally occurring sugar, may prevent UTI by providing a preferential binding site for E. coli. Limited evidence suggests similar effectiveness to low-dose antibiotics for prevention. Probiotics, particularly vaginal Lactobacillus preparations, aim to restore healthy flora that competes with uropathogens. Evidence remains mixed but they appear safe for use.

For postmenopausal women, vaginal estrogen therapy effectively reduces UTI frequency. Estrogen restores vaginal thickness, acidity, and healthy Lactobacillus colonization. Low-dose vaginal preparations (creams, rings, tablets) have minimal systemic absorption and are appropriate for most women without contraindications to estrogen.

What Are the Complications of UTIs?

Untreated or inadequately treated UTIs can lead to serious complications including kidney infection (pyelonephritis), kidney abscess, permanent kidney damage, sepsis (life-threatening blood infection), and pregnancy complications including preterm labor. Recurrent infections can cause chronic kidney disease over time. Prompt treatment prevents most serious complications.

While most urinary tract infections resolve with appropriate treatment, delayed or inadequate treatment can lead to serious complications. Understanding potential complications emphasizes the importance of prompt medical care and completing prescribed treatment courses. Certain populations face higher complication risks and require particularly vigilant management.

The most common complication of an untreated bladder infection is ascending infection to the kidneys. Once bacteria reach the kidneys, they can cause acute pyelonephritis with its associated systemic symptoms. If treated promptly, kidney infections usually resolve completely. However, severe or recurrent kidney infections can cause permanent scarring and reduced kidney function.

Serious Complications

Renal abscess occurs when infection creates a pus-filled cavity within the kidney. This complication requires prolonged antibiotics and often drainage procedures or surgery. Patients with diabetes, obstruction, or delayed treatment face higher abscess risk. Perinephric abscess, infection around the kidney, can spread to adjacent structures and is similarly serious.

Sepsis represents the most dangerous UTI complication. When bacteria enter the bloodstream from an infected urinary tract, the body's immune response can become dysregulated, leading to widespread inflammation, organ dysfunction, and potentially death. Urosepsis causes significant mortality, particularly in elderly and immunocompromised patients. Warning signs include high fever, rapid heartbeat, confusion, and low blood pressure.

Emphysematous pyelonephritis is a rare but life-threatening complication occurring almost exclusively in diabetic patients. Gas-forming bacteria cause kidney tissue destruction. This condition has high mortality rates and usually requires emergency nephrectomy (kidney removal). Any diabetic patient with UTI symptoms should seek prompt medical care.

Long-term Consequences

Chronic or recurrent kidney infections can lead to chronic pyelonephritis with progressive kidney scarring and loss of function. Over years, this can progress to chronic kidney disease requiring dialysis or transplantation. Children with recurrent UTIs and vesicoureteral reflux are particularly vulnerable to this complication.

Recurrent UTIs significantly impact quality of life. The physical discomfort, frequent healthcare visits, repeated antibiotic courses with their side effects, and disruption to daily activities cause substantial psychological burden. Depression and anxiety are more common in women with recurrent UTIs.

UTIs in Pregnancy

Urinary tract infections during pregnancy carry special risks for both mother and baby. Physiological changes of pregnancy promote UTI development – hormonal effects relax the ureters, the growing uterus can compress the urinary tract, and increased urine glucose provides bacterial nutrition. Even asymptomatic bacteriuria (bacteria in urine without symptoms) requires treatment in pregnancy.

Untreated UTIs in pregnancy increase risk of preterm labor, low birth weight, and maternal complications including pyelonephritis and sepsis. Pregnant women with pyelonephritis often require hospitalization. Regular urine screening during prenatal care identifies infections for prompt treatment. Safe antibiotic options exist for use during pregnancy.

UTIs in Special Populations

Certain groups require special consideration for UTI management including elderly patients (who may lack typical symptoms), children (who need evaluation for anatomical abnormalities), pregnant women (who require treatment even for asymptomatic bacteriuria), men (who often have complicated infections), and catheterized patients (who have distinct management needs). These populations may need different diagnostic approaches, antibiotic choices, or treatment durations.

While the general principles of UTI diagnosis and treatment apply broadly, several populations require modified approaches due to different presentations, risk factors, or treatment considerations. Understanding these differences ensures appropriate care for all patients with urinary tract infections.

UTIs in Elderly Patients

Older adults frequently present with atypical UTI symptoms, making diagnosis challenging. Classic symptoms like dysuria and frequency may be absent or attributed to aging changes. Instead, elderly patients may present with confusion, falls, general functional decline, or exacerbation of underlying conditions. Any acute change in mental status in an elderly person should prompt consideration of UTI.

Asymptomatic bacteriuria is extremely common in elderly individuals, particularly those in nursing facilities. Treating asymptomatic bacteriuria in elderly patients is not recommended except before urological procedures, as it doesn't improve outcomes and promotes antibiotic resistance. Treatment decisions should be based on symptoms, not just positive urine tests.

UTIs in Children

Pediatric UTIs require prompt diagnosis and treatment to prevent kidney damage during the developmental years. Infants may present only with fever, irritability, or poor feeding. Older children might have typical symptoms or may complain of abdominal pain. Any unexplained fever in young children warrants urine testing.

Children with their first UTI, recurrent UTIs, or atypical presentations should be evaluated for underlying anatomical abnormalities, particularly vesicoureteral reflux (VUR). Imaging studies (ultrasound, voiding cystourethrogram) guide management. Some children require antibiotic prophylaxis or surgical correction of reflux to prevent kidney scarring.

UTIs in Men

While less common than in women, UTIs in men are almost always considered complicated due to the likely presence of underlying factors. Prostate enlargement causing urinary retention is common in older men. Evaluation should assess for prostatic involvement (prostatitis), obstruction, and other structural issues.

Treatment duration for male UTIs is typically longer than for women, usually 7-14 days. Fluoroquinolones are often preferred when prostate involvement is suspected due to good prostate penetration. Urological evaluation is often warranted, particularly for recurrent infections or young men without obvious risk factors.

Catheter-Associated UTIs

Urinary catheters are a leading cause of healthcare-associated infections. Bacteria can enter along the catheter during insertion or migrate up the catheter over time. The longer a catheter remains in place, the higher the infection risk – nearly all patients with long-term catheters develop bacteriuria.

Management focuses on preventing infection through proper insertion technique, maintaining a closed drainage system, minimizing catheter duration, and removing catheters as soon as possible. Treatment of catheter-associated UTI typically includes catheter removal or change along with appropriate antibiotics. Asymptomatic bacteriuria in catheterized patients should not be treated.