Urinary tract infection.ppt
n7 million office visits yearlyn1 million hospitalizationsnAbout 2/3rds of patients are women;40%to 50%of women have UTI at some point during their livesnImportant complications of pregnancy,diabetes mellitus,polycystic disease,renal transplantation,conditions that impede urine flow(structural and neurologic)nUrinary tract infectionnSignificant bacteriurianAsymptomatic bacteriurianAcute pyelonephritisnChronic pyelonephritisn“Upper”versus“lower”UTInUrethral syndromenUTI:the finding of microorganisms in bladder urine with or without clinical symptoms and with or without renal diseasenSignificant bacteriuria:the finding of 105 cfu/ml of urine(but lower counts can be significant)nAsymptomatic bacteriuria:Significant bacteriuria without clinical symptoms or other abnormal findings.nAcute bacterial pyelonephritis:a clinical syndrome of fever,flank pain,and tenderness,often with constitutional symptoms,leukocyte casts in the urine,and bacteriuria;or histologic findings thereofnChronic bacterial pyelonephritis:Long-standing infection associated with active bacterial growth in the kidney;or the residuum of lesions caused by such infection in the pastnChronic interstitial nephritis:renal disease with histologic findings resembling chronic bacterial pyelonephritis but without evidence of infectionn“Upper UTI”:infection above the level of the bladdern“Lower UTI”:infection at or below the level of the bladdern“Urethral syndrome”:clinical manifestations of lower UTI(dysuria,frequency,urgency)without significant bacteriurianPyuria:the presence of pus(WBCs leukocytes in urine,which may or may not be caused by UTI.The preferred method for quantitation is enumeration in unspun urine using a counting chamber.The leukocyte esterase nitrite test has a sensitivity of between 70%and 90%for symptomatic UTInIn patients with asymptomatic bacteriuria without infection,a colony count of 105 cfu/ml defines infectionnScreening has little apparent value in adults except during pregnancy and prior to urologic surgerynUp to 40%of elderly men and women have asymptomatic bacteriuria nAfter one bladder catheterization:2%nMedical outpatients:5%nPregnancy at term:10%nHypertensive patients:14%nDiabetes mellitus:20%nWomen with cystocoele:23%nCongenital urologic disease:57%nHydronephrosis;nephrolithiasis:85%nIndwelling catheter,open drainage 48 hours:98%(reference:Jackson et al,Arch Intern Med 1962;110:663)Screening for asymptomatic bacteriuria in adults has little value except for two situations:pregnancy(because of the high risk of acute pyelonephritis with its accompanying risk of fetal complications)and prior to urologic surgery(because of the risk of postoperative sepsis).nAt room temperature,the doubling time of common aerobic bacteria is about 20 minutesnSome contaminants in voided urine:Lactobacilli,Cornyebacterium species,Gardnerella,alpha-hemolytic streptococci,anaerobesnAny bacterial growth is significant if the specimen is collected from a normally-sterile site(e.g.,direct bladder puncture)nIn pyelonephritis,the“105 cfu/ml”rule breaks down;fewer colonies can be significant.Up to 20%of young women with acute uncomplicated pyelonephritis have between 103 and 104 cfu/ml.In catheterized patients in whom specimens are obtained directly from the catheter,between 102 and 104 cfu/ml should may be significant.nPatients with uncomplicated infection almost invariably have a single organism;this is not necessarily the case with complicated infectionsnUnspun midstream urine:One bacterium/high-powered field(hpf)correlates with 105/ml(thus,high positive predictive value)nGrams stain of spun urine:absence of visible bacteria makes 105 cfu/ml highly unlikely(that is,high negative predictive value)n20%of patients with urinary tract infection do not have pyurianAerobic gram-negative rods most oftennE.coli accounts for about 90%nStaphylococcus saprophyticus has been increasingly appreciated in recent years(with seasonality,tending to occur in the summer)nRare:anaerobes;pyogenic cocci;viruses nE.coli is the most common pathogennHowever,also common are other Enterobacteriacae(Proteus,Klebsiella,Enterobacter,Serratia,Providencia species)and Pseudomonadaceae(notably,Pseudomonas aeruginosa)nEnterococci:often in obstructive uropathynYeasts:Candida albicans,othersnUrease splits urea into ammonia,which has a direct toxic effect on the kidney;inactivates C4,and alkalinizes the urine with production of struvite crystals(MgNH4P04.6H20)crystalsnProteus mirabilis most often;also Providencia,Morganella,S.saprophyticus,Klebsiella,Corynebacterium D2;mycoplasmanEradicate if at all possiblenNewborns:overall rate is about 1%(higher in males than in females)nPreschool children:UTI is 10 to 20 times more common in girlsnSchool-aged children:about 1.2%of schoolgirls have bacteriuria on any given daynWomen:bacteriuria increases with age and sexual activitynMen:bacteriuria is rare before age 50(and as a corollary,calls for more aggressive evaluation than in women).Subsequently,b
