Urinary Infection B&B

Question 1

what is a “lower” vs “upper” UTI called?

Answer 1

cystitis = bladder (lower) infection

pyelonephritis = kidney (upper) infection

*note most infections ascend from bladder to kidneys rather than reach the kidneys via bloodstream

Question 2

what bacteria is responsible for most UTIs?

Answer 2

Escherichia coli (75-95%)

Question 3

what urease-producing bacteria is the cause of struvite kidney stones?

Answer 3

Proteus mirabilis

Question 4

how do the symptoms of cystitis vs pyelonephritis differ?

Answer 4

cystitis: dysuria, frequency/urgency, suprapubic pain, normal WBC count

pyelonephritis: systemic symptoms (fever/chill), flank pain, CVA tenderness, hematuria, WBC casts

Question 5

what urinalysis findings would be diagnostic of a UTI? (3)

Answer 5

1. cloudy urine
2. leukocyte esterase: produced by WBCs in urine
3. nitrites: most UTI bacteria convert nitrates to nitrites, best for detecting aerobic gram negative rods (like E. coli)

Question 6

what does leukocyte esterase in urinalysis indicate?

Answer 6

WBCs in urine produce leukocyte esterase - indicative of urinary infection

Question 7

which 2 common causes of urinary infection do NOT produce nitrite?

Answer 7

most UTI bacteria convert nitrates to nitrite - best for detecting aerobic gram negative rods (like E. coli) in urinalysis

however, enterococcus and staph saprophyticus do not

Question 8

what is the typical treatment for urinary infection?

Answer 8

3 day course of fluoroquinolones: ciprofloxacin, levofloxacin, ofloxacin

can also give TMP-SMX (trimethoprim-sulfamethoxazole)

Question 9

how is urinary infection in pregnancy treated?

Answer 9

nitrofurantoin (Macrobid)

Question 10

what could be the cause of sterile pyuria?

Answer 10

sterile pyuria = WBC in urine but no bacterial growth

can indicate chlamydia or gonorrhea infection - majority of infected women are asymptotic, but may complain of urinary tract symptoms

Question 11

what histological changes occur with chronic pyelonephritis?

Answer 11

corticomedullary renal scarring, blunting of calyxes, “thyroidization” of kidneys (tubules contain eosinophilic material)

could be caused by recurrent kidney stones in adults or vesicoureteral reflux in children

Question 12

what are the causes of most urinary tract infections? (4)

Answer 12

1. E. coli
2. proteus
3. klebsiella
4. enterobacter

Question 13

describe how bladder infections ascend to become pyelonephritis

Answer 13

normal bladder/urine is sterile, so first step is colonization of distal urethra and introitus (in female) by coliform bacteria - via adhesins on P-fimbriae (pili) of bacteria

Question 14

what is the pathological hallmark of acute pyelonephritis?

Answer 14

patchy interstitial suppurative inflammation, intratubular aggregates of neutrophils, tubular injury

Question 15

what kind of necrosis occurs in renal papillary necrosis?

Answer 15

ischemic coagulative necrosis that appears grey-white to yellow

papillary necrosis is seen mainly in diabetes, sickle cell disease, and patients with urinary tract obstruction

Question 16

what virus is known to cause pyelonephritis in kidney allografts?

Answer 16

polyomavirus

Question 17

what histological changes occur with chronic pyelonephritis?

Answer 17

coarse, discrete corticomedullary scars overlying dilated, blunted, or deformed calyces, and flattening of the papillae

only chronic pyelonephritis and analgesic nephropathy affect the calyces, so pelvocalyceal damage is an important diagnostic clue!

Question 18

how do K antigens facilitate bacterial colonization of the urinary tract?

Answer 18

K antigens: promote bacterial virulence by decreasing ability of antibodies/complement to bind to bacterial surface

K-1 composed of polymer of n-acetyl neuraminic acid - antiphagocytic, works as antigenic disguise

Question 19

what are the most common causes of papillary necrosis? (hint: POSTCARDS)

Answer 19

Pyelonephritis
Obstruction
Sickle cell
Tuberculosis

Cirrhosis
Analgesic nephropathy or Alcohol
Renal vein thrombosis
Diabetic nephropathy
Systemic vasculitis

Question 20

what are 3 important causes of sterile pyuria (WBC in urine)?

Answer 20

(important according to USMLE)

1. genitourinary tuberculosis
2. urethritis/ pelvic inflammatory disease (PID)
3. papillary necrosis

(many many other causes as well)

Question 21

which of these is true?
a. all UTIs in kidney transplant patients are considered complicated UTIs
b. Asymptomatic bacteruria in pregnant women should not be treated

Answer 21

true: a. all UTIs in kidney transplant patients are considered complicated UTIs (because they are on immunosuppressive therapy)

bacteruria in pregnant women should ALWAYS be treated (even if asymptomatic) - pyelonephritis in pregnancy has been associated with adverse outcomes