Cystitis



Cystitis




GENERAL CONSIDERATIONS


Bladder infections in women are common: 10%-20% of all women have urinary tract discomfort at least once a year; 37.5% of women with no history of urinary tract infection (UTI) will have one within 10 years; 2%-4% of healthy women have elevated bacteria in urine, indicating unrecognized UTI. A woman with history of recurrent UTI has an episode once a year. Recurrent bladder infections are significant problems; 55% eventually involve kidneys. Recurrent kidney infection causes progressive damage: scarring and, for some, kidney failure. UTIs are much less common in males, except infants, and indicate anatomic abnormality, prostate infection, or unprotected rectal intercourse.



Causes


Urine excreted by the kidneys is sterile until reaching the urethra. Bacteria can ascend the urethra or, much less commonly, reach the urinary system by the bloodstream. Bacteria are introduced into the urethra from fecal contamination or, in women, vaginal secretions. Factors influencing ascending infection are anatomic or functional obstructions to flow (allowing pooling of urine) and immune dysfunction. Major defenses against infection: free flow, large urine volume, complete bladder emptying, optimal immune function. Urine flow washes away bacteria. The inner surface of the bladder has antimicrobial properties. Urine pH inhibits growth of many bacteria. In men prostatic fluid has antimicrobial substances.



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The body quickly mobilizes white blood cells (WBCs) to control bacteria.




DIAGNOSIS


Bladder infection diagnosis is imprecise; clinical symptoms and presence of significant amounts of bacteria in urine do not correlate well. Only 60% of women with UTI symptoms have abundant bacteria in urine; 20% have serious kidney involvement. Diagnosis is according to signs, symptoms, and urinary findings. Pelvic examination is indicated if history suggests vaginitis or cervicitis or if any diagnostic confusion exists. Microscopic examination of infected urine reveals high WBCs and bacteria. Urine culture determines quantity and type of bacteria. Escherichia coli (from the colon) are most common. Fever, chills, and low back pain suggest kidney involvement. Recurrent infections warrant intravenous urogram to rule out structural abnormality.




Examining Collected Urine


Routine methods include dipsticks, microscope, and culture. For most accurate results, examine urine within 1 hour. If examination must be delayed, refrigerate at 5° C. Culturing requires that urine not be refrigerated for more than 8 hours.



• Dipsticks: reagent strips are dipped into urine and removed. Parts of dipstick are impregnated with chemicals that react with specific substances in urine to produce various colors. Careful matching of dipstick color to color standard at appropriate time is essential. Dipsticks are invaluable for qualitative and rough quantitative analysis: pH, protein, glucose, ketones, bilirubin, hemoglobin, nitrite, and urobilinogen. Some dipsticks detect WBCs and bacteria (including semiquantitative cultures). Leukocyte esterase test detects WBCs (80%-90% sensitive). Many organisms reduce urine nitrate to nitrite (Citrobacter spp., E. coli, Klebsiella pneumonia, Proteus spp., Pseudomonas spp., Serratia marcescens, Shigella, Staphylococcus spp. [most]). Measuring nitrite (50% sensitive) is inexpensive and a rapid detector of bacteriuria; confirm by culture.


• Microscopic examination: Perform within first hour. Place a drop of fresh urine or a drop of resuspended sediment from centrifuged fresh urine on slide, cover with cover glass, and examine with high-dry objective under reduced illumination. More than 10 bacteria per field in unstained specimen suggests bacteria count >100,000/mL. Gram stain under oil immersion objective; WBCs indicate infection. Abundant protein and/or WBC casts indicate renal involvement, commonly pyelonephritis.


• Urine culture: Only quantitative cultures typically are used. Diluted urine is introduced to suitable medium and incubation. Colonies counted and multiplied by dilution factor, giving bacterial count per milliliter. Bacteriuria is significant if >100,000/mL but 1000 colonies/mL is clinically significant in the presence of UTI symptoms. Semiquantitative tests using dipsticks or glass slides coated with culture media commonly are used. Colonies are counted or appearance is compared 12-24 hours later. Recurrent or chronic infection warrants sensitivity studies. Roughly 95% of UTIs involve single bacterial species. Mixed species suggest contamination. S. epidermidis, diphtheroids, and Lactobacillus are common in distal urethra but rarely cause UTI. The most common organisms are E. coli, Proteus miribili, Klebsiella pneumonia, Enterococcus, Enterobacter aerogenes, Pseudomonas aeruginosa, Proteus spp., S. marcescens, S. epidermidis, and S. aureus.

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Apr 3, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Cystitis

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