Snapshot A 25-year-old, G1P0, woman who is 14 weeks pregnant presents to her obstetrician for routine prenatal screening. She reports feeling well except for mild nausea. She denies any dysuria, urinary frequency, or abnormal bleeding from the vagina or seen in the urine. A clean catch mid-stream urine sample is collected for urine culture. Urine culture reveals bacteriuria of ≥ 105 cfu/mL. She is started on oral nitrofurantoin for 5 days. (Asymptomatic bacteriuria in pregnancy) Introduction Clinical definition urinary tract infections (UTI) can either be asymptomatic or symptomatic and encompasses asymptomatic bacturia (ASB) login to view 7 more bullets cystitis prostatitis pyelonephritis Epidemiology Incidence 50-80% of women acquire at least 1 UTI 20-30% of women with 1 UTI have recurrent infections Demographics more common in women, elderly, and infants Location bladder prostate kidneys Risk factors female due to the shorter female urethra benign prostatic hyperplasia frequent sexual intercourse obstruction (e.g., constipation) history of UTI incontinence diabetes mellitus vasicoureteral reflux spermicide use indwelling catheter intermittent catheterization can prevent a UTI labial adhesions peak incidence is 2 years of age pathogenesis login to view 2 more bullets presents with login to view 4 more bullets physical exam login to view 3 more bullets treatment login to view 1 more bullet ETIOLOGY Pathogenesis in most cases bacteria ascends from the urethra to the bladder (cystitis) bacterial organisms can further ascend through the ureter and infect the kidney causing a renal parenchymal infection (pyelonephritis) note that infection and symptom development depends on the login to view 7 more bullets hematogenous spread to the urinary tract can also result in a UTI; however, this is rare login to view 1 more bullet Classification It is important to distinguish between uncomplicated and complicated UTI uncomplicated UTI this describes acute cystitis or pyelonephritis in outpatient women who are not pregnant and do not have anatomic abnormalities or instrumentation within the urinary tract complicated UTI this describes UTI that is not uncomplicated Microbiology of Urinary Tract Infections Microbe Findings Comments E. coli Green metallic sheen on EMB agar Most common cause of UTI S. saprophyticus Second most common cause in sexually active women K. pneumoniae Large mucoid capsule and viscous colonies Third most common cause S. marcescens Red pigment production by select strains Third most common cause Enterococcus Typically a nosocomial infection that is drug-resistant P. mirabilis - "Swarming" appearance on agar - Urease positive - Can result in struvite stone formation P. aeruginosa Blue-green pigment Typically a nosocomial infection that is drug-resistant Presentation Symptoms/physical exam/findings ASB asymptomatic patient with an incidental finding of bacteruria on urine culture cystitis dysuria urinary frequency urgency nocturia suprapubic discomfort gross hematuria prostatitis dysuria frequency pain in the prostatic pelvic or perineal area bladder outlet obstruction fever and chills pyelonephritis fever login to view 1 more bullet costovertebral angle pain login to view 1 more bullet obstructive uropathy in patients with diabetes login to view 1 more bullet emphysematous pyelonephritis in patients with diabetes login to view 1 more bullet Imaging Ultrasound renal and bladder indications in children < 2-years-old with a first febrile UTI in children who are not appropriately responding to antimicrobial treatment of UTI in children with recurrent UTIs family history of renal or urologic disease unless severe illness or failure to respond to therapy, imaging should occur after resolution of the acute illness Voiding cystourethrogram indication test of choice to determine the presence of a vesicourethral reflux 2 or more febrile UTIs in children anomalies seen on renal ultrasound high fever with pathogen other than E. coli Studies Labs urine dipstick nitrite positivity suggests an E. coli infection or other infection of the Enterobacteriaceae family leukocyte esterase positive urease positivity login to view 4 more bullets urinalysis > 10 white blood cells (WBCs)/mL > 1000 CFU/mL white blood cell casts login to view 1 more bullet urine culture gold standard for diagnosing UTI must be sent in pregnant patients to determine sensitivity assess for pregnancy Histology chronic pyelonephritis "thyroidization" of tubules due to eosinophilic casts contained in the tubules Differential Acute hemorrhagic cystitis can be caused by adenovirus Urethritis Nephrolithiasis Genitourinary malignancy Treatment Medical TMP-SMX, nitrofurantoin, fosfomycin indications login to view 8 more bullets fluoroquinolones (e.g., ciprofloxacin) indication login to view 1 more bullet fluconazole indication login to view 1 more bullet amoxicillin-clavulanate no treatment indicated in asymptomatic bacteriuria in non-pregnant patients Operative nephrectomy indications login to view 1 more bullet percutaneous drainage indications login to view 2 more bullets Complications Uncomplicated UTI complications are uncommon Complicated UTI bacteremia urosepsis systemic inflammatory response syndrome (SIRS) renal and perinephric abscess emphysematous pyelonephritis xanthogranulomatous pyelonephritis associated with long-term urinary tract obstruction and infection login to view 1 more bullet malakoplakia renal papillary necrosis UTI in pregnancy pyelonephritis sepsis chorioamnionitis preterm labor low birth weight hypertension and pre-eclampsia UTI in men acute or chronic prostatitis urethritis acute epididymitis orchitis Prognosis ASB in elderly or catheterized patients does not increase the risk of death Recurrent UTI in children and adults does not result in chronic pyelonephritis or renal failure this is true when there are not anatomic abnormalities