Urinary Tract Infections

Urinary tract infections (UTIs) are common and potentially disabling. It is important to use the same terminology when referring to various types of infectious episodes. Bacteriuria is merely the presence of bacteria in the urine, whereas a UTI implies an inflammatory response to bacterial invasion of the tissues. Pyuria is the presence of white blood cells (WBCs) in the urine seen on microscopic urinalysis and is an indication of an inflammatory process.

CLASSIFICATION OF URINARY TRACT INFECTIONS

First infection
Unresolved bacteriuria during therapy (most commonly owing to a resistant organism)
Recurrent UTIs:
- Reinfection (>80%)—recurrence from new organisms outside the urinary tract
- Bacterial persistence (uncommon)—recurrence from the same organism within the urinary tract despite sterilization of urine during therapy

Causes of Bacterial Persistence

Infected stones
Chronic bacterial prostatitis
Unilateral infected atrophic kidney
Vesicovaginal or intestinal fistulas
Ureteral anomalies
Infected diverticula
Foreign bodies (stents and catheters)
Infected urachal cyst
Infected medullary sponge kidney
Infected papillary necrosis
Ureteral stump after nephrectomy

Factors That Increase the Risk of Complications from Urinary Tract Infections

Urinary tract obstruction
Infections from urea-splitting bacteria
Diabetes mellitus
Renal papillary necrosis
Neurogenic bladders
Pregnancy
Congenital urinary tract anomalies
Elderly patient with acute bacterial prostatitis
Severe reflux in children younger than age 4 years
End-stage renal disease on hemodialysis
Immunosuppression after a renal transplant

UPPER TRACT INFECTIONS

Acute Pyelonephritis

Acute pyelonephritis is associated with a clinical syndrome of chills, fever, and flank pain as a result of bacterial infection of the renal parenchyma and pelvis. It is usually associated with dysuria, pyuria, frequency, and urgency. The most common causative organisms are Escherichia coli, Klebsiella, Proteus, Enterobacter, Pseudomonas, Serratia, Citrobacter, occasionally Streptococcus faecalis, and rarely Staphylococcus aureus. Infection usually results from bacteria ascending from the lower urinary tract. Hematogenous infection occurs infrequently.

▪ Workup

Urinalysis (pyuria, bacteriuria, and hematuria)
Urine culture and sensitivity (before and during therapy)
Complete blood count (CBC) (significant neutrophilic leukocytosis)
Blood culture (frequently positive)
Stone Protocol CT Scan (may show stones or obstruction)
Renal ultrasound (stones, hydronephrosis, or abscess)
Voiding cystourethrography (VCUG) (delay several weeks because transient reflux can often occur during an acute infection)

▪ Management

In uncomplicated cases, outpatient management with an oral fluoroquinolone may be appropriate. In other cases, intravenous (IV) antibiotic therapy should be started without delay after cultures are sent. A quinolone or ampicillin (1 g IV q6h) and gentamicin or tobramycin (1.5 mg/kg IV q8h) are a good choice initially until culture and sensitivity results are available. Obstruction noted on CT or ultrasound must be relieved. Fevers will often persist for 2 to 5 days despite sterile urine and antibiotic therapy. However, if the urine continues to show infection, reevaluation should be instituted to rule out obstruction, abscess, or inappropriate antibiotic selection. If symptoms have resolved after 2 to 5 days of IV antibiotics, the patient may be switched to PO medication for an additional 10 to 14 days.

Pyonephrosis

Pyonephrosis refers to a condition characterized by acute pyelonephritis complicated by obstructed hydronephrosis. Renal ultrasound or computed tomography (CT) scan can usually make the diagnosis. The IVU will show nonfunction or poor visualization of the involved kidney. Fifty percent of obstructed pyonephrotic kidneys are nonfunctioning. Obstruction should always be ruled out in pyelonephritis. Renal ultrasound is usually sufficient.

▪ Management

IV antibiotics and immediate relief of obstruction by either a percutaneous nephrostomy or placement of a retrograde ureteral stent are mandatory.

Emphysematous Pyelonephritis

Emphysematous pyelonephritis is an acute necrotizing parenchymal and perirenal infection. It is a rare complication of acute pyelonephritis in which organisms (generally E. coli) ferment glucose to CO₂ and H₂O, producing gas in the renal parenchyma. The characteristic appearance of intraparenchymal gas on the kidney, ureter, and bladder (KUB) is diagnostic. Eighty percent
of cases occur in poorly controlled insulin-dependent diabetics, and the rest occur in patients with obstruction. Prognosis is poor with a high mortality.

Management consists of IV antibiotics, relief of obstruction, and frequently nephrectomy.

Renal Abscess (Carbuncle)

Renal cortical or medullary abscesses typically arise from a focus of pyelonephritis (usually E. coli) or by hematogenous spread of S. aureus from a distant cutaneous infection, particularly in IV drug abusers. Patients present with chills, fever, and flank pain. Urinalysis may be normal in a staphylococcal renal abscess. CBC will show marked leukocytosis with shift to the left.

Perinephric Abscess

A perinephric abscess lies between the renal capsule and the perirenal (Gerota’s) fascia. Rupture of an intrarenal abscess into the perirenal space is the most common etiology; however, hematogenous seeding from distant sites of infection occurs. The most common organisms are Proteus or E. coli (from an intrarenal abscess) and S. aureus (from distant infections). Mortality has been reported as high as 50%, mostly because of the difficulty in making a diagnosis. Diabetics and patients with polycystic kidneys on hemodialysis are particularly susceptible.

Chronic Pyelonephritis

Chronic pyelonephritis is a radiologic or pathologic diagnosis referring to severe cortical scarring or the small, contracted, atrophic kidney. Etiology is unclear; however, chronic pyelonephritis appears to originate in childhood and is associated with recurrent bacteriuria and vesicoureteral reflux.

Xanthogranulomatous Pyelonephritis

Xanthogranulomatous pyelonephritis is an uncommon, atypical chronic renal parenchymal infection that is often misdiagnosed as a renal tumor. Etiology is unknown, but infection and obstruction are almost always present.

▪ Presentation

Fever, chills, flank pain, and flank mass are typical. The IVU shows a renal mass in 60% and stones in 40% to 70%. CT scan often demonstrates a large renal mass with a central calcification. The involved kidney is often nonfunctioning. Persistent bacteriuria occurs in <50%, with Proteus and E. coli being the most frequent organisms. It can be difficult to differentiate from renal cell carcinoma; therefore, the diagnosis is often made at surgical exploration.

LOWER TRACT INFECTIONS

Cystitis

Acute bacterial cystitis is an infection of the bladder with organisms that ascended from the urethra. Its hallmark symptoms include frequency, urgency, nocturia, and dysuria. Patients will
often complain of low back or suprapubic pain. Fever is unusual. Urinalysis typically shows pyuria, bacteriuria, and hematuria. Urine cultures are positive, and E. coli is the usual pathogen. A persistent Proteus infection should suggest the possibility of an infected struvite stone.

Females have a higher incidence of cystitis, which increases throughout their lifetime. Recurrence is also high and is associated with coliform bacterial colonization of the urethra and vaginal vestibule.

Males are more likely to have other associated urinary problems (e.g., prostatitis, urethritis, strictures, and benign prostatic hyperplasia) that must be treated.

Children with a UTI, particularly infants, should have a thorough evaluation of the urinary tract including VCUG and renal ultrasound. (VCUG should be postponed 4-6 weeks because incidental low-grade reflux is often observed during an acute infection.)

Pyocystitis

Pyocystitis is a collection of pus within the bladder. It most commonly occurs in dialysis patients with low or absent urine output. Patients present with fever, suprapubic pain, and a palpable mass. Pelvic ultrasound can help make the diagnosis; however, a strong suspicion would warrant a diagnostic bladder aspiration. Management involves draining the bladder and providing appropriate antibiotic coverage.

Emphysematous Cystitis

Emphysematous cystitis (cystitis emphysematosa) is a rare manifestation of UTI characterized by gas within the bladder or its muscular wall. It usually occurs in severe diabetics and is commonly caused by E. coli, Proteus, Pseudomonas, and rarely
clostridia. Certain strains of these bacteria have the potential to ferment glucose. Other causes of air in the bladder include instrumentation and colovesical fistulas. The radiographic picture on KUB is pathognomonic. Cystography will confirm the location of the gas to the bladder. Treatment includes appropriate antibiotic therapy, control of glucosuria, and relief of any outlet obstruction.

Urethritis in Males

Urethritis in males presents with urethral discharge, dysuria, and frequency. It is an infection acquired by inoculation of organisms into the urethra during sexual intercourse. It is classified as gonococcal or nongonococcal urethritis based on the causative pathogens.

▪ Gonococcal Urethritis

Gonococcal urethritis is caused by an intracellular Gram-negative diplococcus, Neisseria gonorrhoeae. It has a short incubation of 2 to 8 days and produces a purulent, yellowish discharge with dysuria.

▪ Nongonococcal Urethritis

Nongonococcal urethritis is believed to be the most common cause of urethritis in males, with Chlamydia trachomatis being the most important pathogen (40%). Other likely pathogens include Ureaplasma urealyticum (30%), Trichomonas vaginalis (5%), or Candida albicans. It has a prolonged incubation of 5 to 21 days
and produces a mucoid, whitish discharge, with or without dysuria. The diagnosis of nongonococcal urethritis requires the exclusion of gonorrhea and the demonstration of urethritis (Gram’s stain of urethral swab showing >4 polymorphonucleocytes per oil immersion field).

▪ Reiter’s Syndrome

Reiter’s syndrome is a rare complication of nongonococcal urethritis possibly owing to C. trachomatis. It can present with arthritis, conjunctivitis, balanitis circinata, or keratodermia blennorrhagia.

Urethritis in Females

Urethritis in females presents with frequency, dysuria, and often pyuria; however, the urine culture will show no growth. Vaginitis accounts for up to one-third of these cases and must be diagnosed and treated appropriately. Gonorrhea or chlamydial infection will be responsible for most other patients, despite the absence of a urethral discharge, and is treated as done so in males.

Vaginitis

Vaginitis often produces symptoms that mimic a bladder infection and, therefore, must be recognized so that appropriate treatment may be rendered. Normal vaginal discharge is clear, white, or gray, with a pH < 4.5, and rare leukocytes. The most common causes of adult vaginitis are Trichomonas, Candida, and nonspecific organisms.

▪ Trichomonas Vaginitis

Trichomonas vaginitis is caused by a flagellated protozoan, T. vaginalis, and produces a thin, watery, yellowish-green, foamy malodorous discharge. Patients present with soreness, itching, and dysuria. The discharge may liberate a fishy odor with 10% KOH, has a pH > 4.5, and will show leukocytes and motile trichomonads. Trichomonas culture is positive.

▪ Candida Vaginitis

Candida vaginitis (Monilia) is generally caused by C. albicans and produces a thick, white, cheesy, curd-like discharge. Mycotic or fungal vaginitis most often occurs in pregnancy and diabetes and in patients taking oral contraceptives or antibiotics, especially tetracycline. Patients present with intense itching and discharge that shows yeast-like buds and hyphae on 10% KOH preparation and has a pH < 4.5.