Urinary tract infection 尿路感染 方 炜 Renal Division, Renji Hospital Shanghai Second Medical University

Introduction Urinary tract infection (UTI) is the most common of all bacterial infections, affecting humans throughout their life span. Not only is UTI common, but the range of clinical effects it can produce is exceptionally broad, from acute pyelonephritis with gram- negtive sepsis to asymtomatic bacteriuria.

Introduction UTI upper pelvic 肾盂 calyx 肾盏 ureter 输尿管 Female:male 10:1 lower bladder 膀胱 urethra 尿道 pyelonephritis cystitis urethritis Female:male 10:1

Definition UTI: a broad term that encompasses both asymptomatic microbial colonization of the urine and symptomatic infection with microbial invasion and inflammation of urinary tract structures. Acute pyelonephritis (急性肾盂肾炎): a pyogenic, focal infection of the renal parenchyma accompanied by local and systemic symptoms of infection. Chronic pyelonephritis（慢性肾盂肾炎）: the pathologic and radiologic findings of chronic cortical scarrings, tubulointerstitial damage, and deformity of the underlying calyx.

Pathogen Gram-negtive enterobacteria is most common 95% E.coli大肠杆菌 60-80% Proteus mirabilis 变形杆菌 Klebsiella sp克雷伯杆菌 Pseudomonas sp 绿脓杆菌 (urinary tract instrumentation) Serratia sp 沙雷杆菌 Gram-positive organisms 5-10% Streptococcus faecalis 粪链球菌 Staphylococcus aureus 金黄色葡萄球菌 Staphylococcus albus 白色葡萄球菌 Fungi 真菌 Yeasts 原虫 Viruses 病毒

Possible routes of infection Ascending infection Most UTI are believed to occur by the ascending route. urethra→bladder→ureter→pelvis→calyx →parenchyma Hematogenous infection Relatively rare Staphylococcal bacteremia 金葡菌血症 Intestine to kidney by way of lymphatics 盆腔器官炎症 阑尾炎 结肠炎 Direct infection 外伤 肾周器官感染

Ascending infection： urethra→bladder→ureter→pelvis→calyx →parenchyma Hematogenous infection： circulation → parenchyma →calyx →pelvis

The defence mechanism of urinary tract Valve at the junction of ureter and bladder. The dilution and removal of bacteria in urine which occurs with micturition. The high concentration of urea and low pH in urine restrict the growth of bacteria. Antibacterial ability of mucosa: secret IgA, IgG. Prostatic fluid

Factors predisposing to infection Obstruction to the flow of urine anywhere from the kidney to urethra is well recognized as the most important predisposing cause. Congenital abnormalities such as polycystic kidney disease 多囊肾, vesicoureteral reflux 膀胱输尿管返流. urinary tract instrumentation Female urethra Disturbence of immune capacity such as diabetes, anemia, chronic hepatic disease, chronic kidney disease, tumor and so on. Inflammation of near area Other factors

Pathology - Acute Phase Macroscopic examination: Mucosa is edematous and congestive, and contain a variable number of abscesses on the capsular surface and on cut sections of the cortex and medulla. Occasionally, areas of inflammation extend from the cortex into the medulla in the shape of wedge.

Pathology - Acute Phase Histologic changes: Tubular epithelial cells are edematous, necrosis and detach from basement membrane. Some tubules are damaged and others are destroyed, many tubules contain leukocytes. Acute inflammation with polymorphonuclear leukocyte infiltraton may be found. The glomeruli and blood vessels are relatively free of inflammatory changes.

Pathology - Chronic Phase Macroscopic examination: Parenchymal scarring and underlying caliceal deformity. The kidneys are frequently irregular, and reduction in size is often unilateral or asymmetrical. The kidney usually has flat-based or U-shaped scars.

Chronic pyenephritis. Note the irregularly scared kidney, dilated and blunted calices.

Chronic pyenephritis broad scars in a patient with chronic VUR.

Pathology - Chronic Phase Histologic changes: increase in interstitial fibrous tissue tubule atrophy and necrosis periglomerular fibrosis

Clinical presentations Acute pyelonephritis Systemic symptoms: rigors and high fever, often with fatigue, nausea and vomiting, abdominal pain or diarrhea. Local manifestations: Dysuria frequancy, and nocturia. Back and loin pain (with exquisite tenderness on percussion of the costovertebral angle). Urine: Cloudy urine, pyuria.

Clinical presentations Chronic pyelonephritis Asymptomatic bacteriuria, dysuria and frequency, vague complaints of flank or abdominal discomfort, and intermittent low-grade fevers. May be divided into the following five types: Recurrent type; Low-grade fever type; Hematuria type; Insidious type; Hypertension type

Recurrence clinical characteristic of pyelonephritis Relapse: If bacteriuria recurs with the same pathogen within a short time following cessation of therapy, the recurrence is defined as a relapse. Reinfection: infection with new organism.

Complications Papillary necrosis Perinephric abscess Septicemia Renal stone and obstruction

Complications- Papillary necrosis An uncommon complication in pyenephritis. Occurs more often in diabetic patients. Patients sometimes have renal colic with hematuria due to passage of papillae down the ureter. The IVP may show loss of papillae.

Complications- Perinephric abscess rare complication of pyelonephritis, often associated with obstruction to urine flow or DM . Symptoms and signs: loin pain accentuated by movement, chills and fever, urinary frequency and dysuria. Ultra-sound, radiation examination help to diagnosis.

Laboratory examinations Urinary routine White cells are frequently observed. Detection of leukocyte casts is also an indication of involvement of the kidney. hematuira Proteinuria, < 2g/d, low molecular protein. Low gravity, high pH, when the tubular dysfunction occurs.

Laboratory examinations Gram’s stain The simplest method for detecting significant bacteriuria is to examine the urine under the microscope, using Gram’s stain. If bacteria are found using the oil immersion objective, there are likely to be more than 105 bacteria/ml of urine.

Laboratory examinations clean mid-stream urine culture The most widely used method of collecting urine for culture and is the method of choice. If the bacterial counts > 100000/ml, can be defined significant result. When bacterial count < 10000/ml, can be regard as contaminated. Coccus count reaches 1000~10000/ml also can be defined significant result.

Clean mid-stream urine culture, notice: the procedure should be done before antibiotic therapy or 5 days after cessation antibiotic therapy. the first uriation is preferred for the bacteria can grow more. strict attention to asepsis is necessary.

Other examinations Blood routine test: WBC，ESR  ，CRP  Antibody-coated bacteria: help to distinguish pyelonephritis from the lower UTI Renal function tests: defect in urinary concentrating, acidification capacity as well as glomerular filtration function. Radiologic evaluations

Radiologic evaluations objective: delineate abnormalities that would lead to changes in the medical or surgical mangement of the patient. Indication: recurrence; complicated UTI; clinical presentation of pyelonephritis; rare pathogen infection; persistent infection; male Notice: should be avoided during acute phase

Diagnosis Acute pyelonephritis The diagnosis can be established according to the systemic, local symptoms and signs as well as the urine test.

Diagnosis History exceed half year, companied with: IVP show the deformity and stricture of pelvis and calices The kidneys are irregular, often asymmetrical Decreased tubular ability.

Differential diagnosis Lower UTI: Antibody-coated bacteria(-) urine culture after bladder sterilized absence of systemic symptom Urethral syndrome: urine culture(-) Renal TB: dysuria, frequency and nocturia persistent and obvious urine TB culture(+) serous anti-TB antibody(+) X-ray

distinguished from chronic glomerulonephritis   Chronic glomerulonephritis Chronic pyelonephritis History Edema, hypertension Usually no edema Proteinuria Middle and large molecular protein, usually > 2g Low molecular protein, usually < 2g Renal function Defect of glomerular function Defect of tubular function Radiological examination Sizes of kidneys are similar, no deformity and stricture of pelvis and calices Sizes of kidneys are different, with deformity and stricture of pelvis and calices

Treatment Acute pyelonephritis General treatment: rest in bed, increase fruid intake and so on. Antibiotic treatment: should start antibiotic therapy immediately after urine collection. Serious patient should be given combined 2 antibiotic drugs and the drug should be given through intravenous route. The antibiotic course usually is 10~14 days.

Treatment Chronic pyelonephritis General treatment: the most important effort should be made to correct the underlying complicating factors such as urinary tract obstruction, congenital abnormality and so on. Rest, fruid intake to increase urine volume is also needed.

Treatment Chronic pyelonephritis Principles of antibiotic treatment including: combined antibiotic therapy is usually need. treatment course: 2~4 weeks. correct the underlying complicating factors. the treatment of acute phase is similar to acute pyelonephritis

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