Managing urinary tract infections

Urinary tract infections (UTI) are common in childhood. Presence of pyuria and bacteriuria in an appropriately collected urine sample are diagnostic of UTI. The risk of UTI is increased with an underlying urological abnormality such as vesicoureteral reflux, constipation, and voiding dysfunction. Patients with acute pyelonephritis are at risk of renal scarring and subsequent complications such as hypertension, proteinuria with and without FSGS, pregnancy-related complications and even end-stage renal failure. The relevance and the sequence of the renal imaging following initial UTI, and the role of antimicrobial prophylaxis and surgical intervention are currently undergoing an intense debate. Prompt treatment of UTI and appropriate follow-up of those at increased risk of recurrence and/or renal scarring are important.     

Complicated urinary tract infections

A complicated urinary tract infection is that which occurs in a patient with an anatomically abnormal urinary tract or significant medical or surgical comorbidities. Whereas this definition may not cover each and every situation, it does serve to encompass the great majority of these patients and guide their care. The definition is necessarily broad, to assure that these potentially complex patients are appropriately managed. Thus, complicated urinary tract infection describes a group of patients that usually need a prolonged course of antimicrobial therapy, with all its attendant morbidities, costs, and outcome differences.     

Catheter-associated urinary tract infections

In the past few years it has been clearly demonstrated that the concept of bacterial biofilm production permits an understanding and provides some explanation of the pathogenesis, diagnosis and treatment of catheter-associated urinary tract infections. This concept describes the colonization of catheter surfaces and the movement of bacteria against the urinary flow. It explains the antibacterial resistance of these matrix-enclosed sessile populations of bacteria. The catheter encrustation can be observed as mineralizing bacterial biofilm. The differentiation in swarming cells exposing a much higher activity of the enzyme urease is responsible for the predominant role of Proteus mirabilis in obstructing encrustations. The guidelines for the prevention of catheter-associated urinary tract infections were developed over the past decades by clinicians and are still valid. They can now be better understood taking into consideration these new theories. As overuse of urethral catheters and non-compliance of their recommended use are still apparent, educational and surveillance programmes are needed to help maintain good standards of care.     

Nosocomial urinary tract infections

Hospital-acquired urinary tract infections, which account for approximately 40 percent of all nosocomial infections, often result in serious complications and ultimately lead to rising hospital costs. To combat the high incidence of nosocomial urinary tract infections, surveillance and control programs must be developed and carefully maintained by hospitals. When urinary tract infections cannot be prevented, empiric therapy with broad-spectrum antibiotics effective against beta-lactamase-producing bacteria should begin immediately.     

Nosocomial urinary tract infections

Convenience to the hospital staff is certainly not an acceptable reason for the use of a potentially dangerous drainage tube. An indwelling urinary drainage catheter should be used only in patients who need multiple straight urinary catheterizations, develop urinary obstruction or incontinence, or are comatose and require frequent urinary output measurements. An indwelling catheter may also be needed for drainage or stenting during or following genitourinary surgery. Once it has been determined that urinary catheterization is necessary, a closed urinary drainage system catheter must be carefully and aseptically inserted by experienced hospital personnel after careful preparation. The closed drainage system must be meticulously maintained throughout the patient's hospitalization and catheterization. After the catheter is removed, a urinary culture should be performed to identify any postcatheter infection. If there is infection, the patient must be treated with antibiotics. If symptoms of a urinary tract infection, bacteremia, or sepsis ensue, treatment must be rapidly begun with antibiotics as appropriate on the basis of drug sensitivity testing. These techniques will not eliminate bacteriuria associated with urinary drainage catheters. However, they will reduce the incidence, morbidity, and mortality associated with urinary catheterization.     

Pediatric urinary tract infections

Urinary tract infection is a frequent diagnosis in infants and children who are referred to a urologist. Infections in children are often benign, yet the potential for significant renal damage in this age group makes adequate urinary tract evaluation mandatory. Urinary obstruction, vesicoureteral reflux, periurethral bacterial colonization, and voiding dysfunction are important in the pathogenesis of pediatric infections. Adequate therapy requires detection and control of these conditions in order to prevent pyelonephritic renal scarring and its sequelae.     

Fungal infections of the urinary tract

Funguria, fungal urinary tract infections, are most commonly caused by Candida species but may also be caused by Cryptococcus neoformans, Aspergillus species, and the endemic mycoses. Candiduria presents as an increasingly common nosocomial infection, which may involve all anatomic levels of the urinary tract, resulting in a spectrum of disease varying from asymptomatic candiduria to clinical sepsis. Although several successful systemic or local therapeutic options exist for the eradication of candiduria, knowledge of the pathogenesis and natural history of candiduria has lagged. This has resulted in confusion among practitioners as to when antifungal therapy is indicated. Treatment guidelines have recently been formulated and are described herein.     

细菌生物膜对尿管相关性尿路感染的影响

目的 探讨细菌生物膜对留置尿管相关性尿路感染的影响。方法 对留置尿管不同时间的43例患者，于撤除尿管时行尿液细菌培养，并采用阿利新蓝-刚果红联合染色和扫描电镜观察尿管细菌生物膜形成情况，分析尿管细菌生物膜形成与尿管细菌培养及抗生素应用情况的关系。结果 留置尿管患者尿管细菌生物膜阳性率，3d组为0（0／4），1周组33．3％（4／12），2周组71．4％（10／14），4周组100．0％（13／13）。应用抗生素组60．6％（20／33），未用抗生素组70．0％（7／10），2组差异无统计学意义，P〉0．05。结论 细菌生物膜形成是留置尿管相关性尿路感染的重要致病因素，抗生素预防治疗效果不明显。缩短尿管留置时间，采用封闭式引流等仍是尿路感染主要的防治方法。     

Imaging in upper urinary tract infections

Most infections of the upper urinary tract are straightforward and do not require any emergency radiological investigations. A sonogram carried out within 48 hours will in most cases be sufficient to eliminate obstructed pyelonephritis requiring emergency drainage of urine. In complicated cases, or those affecting already weakened areas, an urgent CT scan is necessary, preferably after injection of iodinated contrast medium if renal function permits. CT scanning is far better at diagnosis than sonography as well as at investigating whether there are complications. Furthermore, it is essential that the radiologist is aware of unusual and rare forms of pyelonephritis, especially pseudotumoural forms, so that clinicians can be pointed towards the appropriate treatment, avoiding unnecessary and invasive interventions.     

Controversies in childhood urinary tract infections

Management of childhood urinary tract infections is conceptually straightforward, but controversies persist. Specimens must be collected carefully or culture results can be difficult to interpret. Urine culture remains the diagnostic standard but does not substitute for careful urinalysis. Radiography studies are designed to define abnormalities predisposing patients to pyelonephritis and to assess the extent of renal involvement during infection, but there is no agreement on the most appropriate combination of studies. Circumcision reduces the incidence of urinary infections in male infants. Vaginal reflux may have an impact on recurrent infections, especially after courses of antibiotics. The importance of vesicoureteral reflux remains controversial because renal scarring appears to be related more to infection than to reflux itself. A strong argument can be made for the avoidance of prophylactic antibiotic therapy, even in patients with reflux. Increased attention to early diagnosis and treatment may be responsible for a decreasing incidence in renal failure from reflux nephropathy in children.     

Glycosaminoglycans in childhood urinary tract infections

It has been suggested that urinary glycosaminoglycans (GAGs) form a natural defense mechanism against urinary tract infections (UTIs). This study investigated whether urinary GAGs play a role in pediatric UTIs, and whether urinary GAG level can be used to differentiate upper UTI from lower UTI. Forty-one children with UTIs (33 girls and eight boys; mean age 5.4+/-3.7 years) and 46 age- and sex-matched healthy children (35 girls and 11 boys; mean age 6.6+/-3.9 years) were included in the study. Urinary GAG levels were measured at the onset of acute infection and after a 10-day course of antibiotic treatment. Group GAG findings were compared, and comparisons were also made with the patients divided according to sex and according to UTI type (upper versus lower). The mean urinary GAG level in the patient group at the onset of acute infection (pretreatment) was significantly higher than the mean level in the control group (132.2+/-104.8 mg/g vs 42.2+/-27.1 mg/g creatinine, respectively; P <0.01). In the patient group, the mean urinary GAG level after antimicrobial therapy was significantly lower than the pretreatment level (75.9+/-52.1 mg/g vs 132.2+/-104.8 mg/g creatinine, respectively; P <0.01). However, the mean post-treatment level was still higher than the mean level in the controls ( P <0.05). There was no significant difference in urinary GAG levels when patients were categorized as upper versus lower UTI ( P >0.05). The study results suggest that GAGs play an important role in the pathogenesis of UTIs in children, and that measurement of urinary GAGs may be a valuable noninvasive method for evaluating UTIs in this patient group. However, this assay cannot be used to differentiate upper UTI from lower UTI in children.     

Imaging in lower urinary tract infections

In epididymo-orchitis, a sonogram shows a non-homogenous and hypertrophied epididymis and testis, with increased vascularisation seen on a Doppler sonogram. Abscesses must be investigated using sonography so that a necrotic tumour is not misdiagnosed. In prostatitis, sonography is indicated to investigate urine retention and where treatment has failed (to look for a blockage, an abscess, or pyelonephritis). Endorectal sonography is the best imaging modality for analysing the parenchyma, but otherwise has limited value. Chronic prostatitis is the main differential diagnosis from prostate cancer; the two may be distinguished using diffusion MRI. In cases of cystitis, imaging is indicated when a patient has recurrent cystitis (to investigate what the causative factors might be), or an infection with a less common bacterium (to look for calcifications, emphysema, any involvement of the upper urinary tract), and in cases of cystitis with pseudotumour.     

Uncomplicated urinary tract infections in women

Uncomplicated urinary tract infections, such as acute uncomplicated cystitis and pyelonephritis, are common infections in otherwise healthy women. Although severe complications are rare, the high prevalence of these infections contributes to significant costs to health care systems. The present review addresses recent publications that concern the epidemiology, pathogenesis, aetiology, diagnosis, treatment and prevention of uncomplicated urinary tract infections and recurrent urinary tract infections in women.