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Image from Capps E, Linnau KF, Crane DA. Insights Imaging. 2015;6(1):111-22. [Open access.] PMID: 25503997, PMCID: PMC4330228.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Urinary tract infections (UTIs) are common and range in severity from uncomplicated cystitis to pyelonephritis with complicating renal abscesses.[1] The risk factors associated with UTIs include outflow obstruction from benign prostatic hyperplasia (BPH) or urethral strictures, neurogenic bladder, estrogen depletion, urinary or fecal incontinence, and urinary catheterization.

The noncontrast computed tomography (CT) scan above shows a neurogenic bladder with formation of a bladder stone (yellow arrow). The white arrow depicts circumferential urinary bladder wall thickening, and a catheter within the bladder lumen (yellow arrowhead) is causing gas in the urinary bladder (white arrowheads).

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Uncomplicated UTIs

Main image: Scanning electron microscope (SEM) image of Escherichia coli from the Centers for Disease Control and Prevention (CDC) / Janice Haney Carr. Inset: E coli Gram stain from Wikimedia Commons / Y_tambe.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Uncomplicated UTIs

E coli is the most common cause of community-acquired UTIs.[2] Females are more susceptible to UTIs, as the female urethra is significantly shorter than that of males. Female patients who present with uncomplicated UTIs usually report symptoms and signs that include dysuria, hematuria, back pain, and suprapubic discomfort.[1] Such patients can be treated with appropriate antibiotics in the outpatient setting.

However, rates of antibiotic-resistant bacteria are climbing with the routine use of antibiotics, such as ciprofloxacin and trimethoprim-sulfamethoxazole (TMP-SMX, co-trimoxazole).[1,2] For example, between 2003 and 2012, ciprofloxacin resistance increased in all age groups, but the rise was especially pronounced among isolates from adults: from 3.6% in 2003 to 11.8% in 2012.[2]

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Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

The degree of hematuria associated with a UTI can range in severity from a slightly pink tinge to gross hematuria (shown).[1] Hematuria can occasionally be managed with improved hydration, which dilutes the urine without the need for placement of a large-bore Foley catheter. However, if significant hematuria and clot formation are present, placement of a large-bore Foley catheter may be required to prevent urinary obstruction due to the clots. If hematuria is associated with an infection, the degree of hematuria typically improves with the appropriate antimicrobial treatment of the UTI.[1]

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Asymptomatic Bacteriuria

Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Asymptomatic Bacteriuria

Asymptomatic bacteriuria is an entity in which a single isolate of bacteria is identified in a patient who is not exhibiting signs and symptoms.[1] However, this aspect of the history taking may be difficult to elucidate in patients who cannot describe their symptoms (eg, neurologically impaired patients).

In otherwise healthy adults, asymptomatic bacteriuria has not been found to be harmful; thus, it does not require treatment—unless the patient is pregnant or is undergoing a urologic procedure.[1] Approximately 2% to 10% of pregnant patients have asymptomatic bacteriuria; if left untreated, up to 30% of these women will eventually develop pyelonephritis.[3] In addition, untreated asymptomatic bacteriuria in pregnancy has been associated with preterm birth and low birth weight.[3]

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Image courtesy of Medscape.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Three variations of Foley catheters are shown: (1) straight tip, standard Foley; (2) a curved coude tip Foley; and (3) a three-way Foley catheter.

Urinary Catheter-Associated UTIs

The placement of a urinary catheter may be required because of urinary retention, hematuria, or urologic procedures.[1] However, the presence of a urinary catheter increases the risk of bacteria within the urinary system by almost 10% for each day the catheter is present. Indeed, catheter-associated UTIs are the most common nosocomial infection.[1]

Some studies have shown that the risk of infection after one-time urethral catheterization is 1% to 2% in healthy women; this risk increases in hospitalized patients.[1] Despite these findings, antimicrobial prophylaxis is discouraged, as most cases of bacteriuria related to urinary catheters are asymptomatic.

Aseptic technique while placing a urinary catheter is paramount to prevent associated infections. If a UTI is suspected, obtain a urine culture to guide proper antimicrobial therapy.

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Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

This CT scan was obtained from a 31-year-old woman who presented with fever, flank pain, and a positive urinalysis. Note the multiple areas of hypodensity in the right kidney, consistent with pyelonephritis.

Pyelonephritis

Classically, acute pyelonephritis manifests with sudden onset of flank pain, fever, and chills.[1] There can be associated abdominal pain, nausea, vomiting, and diarrhea. The presence of granular or leukocyte casts on urinalysis is also suggestive of pyelonephritis.[1]

Pyelonephritis can be categorized as uncomplicated or complicated. Complicated cases include those involving pregnant patients; kidney transplant recipients; immunocompromised persons; and those with uncontrolled diabetes, urinary anatomic anomalies, kidney failure, and/or hospital-acquired infections.

Patients who require hospital admission are typically treated with hydration and intravenous antibiotics for about 7 days, followed by 7 days of oral antimicrobial therapy upon discharge.[1] If the usual treatment pathways fail, obtain imaging to rule out other complicating factors (eg, an obstructing stone).

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Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

This image reveals the purulent material that can build up behind an obstructing ureteral stone and cause complicated pyelonephritis. The blue stent is placed endoscopically past the stone to allow obstructed urine and infection to flow out.

The patient is a 74-year-old woman who presented with acute onset of right flank pain, a temperature of 40.8°C (105.4°F), and tachycardia. Her serum lactic acid level was 7.8 mmol/L, and there were 10-20 white blood cells in her urine with positive nitrite. The patient underwent emergent decompression with removal of the obstructing ureteral stone and placement of a ureteral stent.

The European Association of Urology and the American Urological Association indicate that standard therapy for septic patients with obstructing stones is "urgent decompression of the collecting system with either percutaneous drainage or ureteral stenting. Definitive treatment of the stone should be delayed until sepsis is resolved."[4,5]

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CT scan courtesy of Medscape. Gas is present in the right renal cortex and collecting system, with some extension into the perinephric space.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Emphysematous pyelonephritis and cystitis

Emphysematous pyelonephritis is a rare, potentially life-threatening, gas-forming infection of the upper urinary tract, renal parenchyma, and surrounding structures.[6] It is commonly associated with diabetes mellitus, particularly in females. Poor prognostic factors include advanced age, higher body mass index, renal impairment, thrombocytopenia, altered sensorium, and shock at presentation.[6]

Emphysematous cystitis is another rare, potentially life-threatening infection typically seen in female patients with diabetes.[7,8] Its clinical presentation can be variable, ranging from irritative voiding symptoms or pneumaturia to an acute abdomen and severe sepsis. Concurrent infection with emphysematous pyelonephritis can also occur. As with most UTIs, E coli is the predominant inciting organism in emphysematous cystitis.[7,8]

Management includes antibiotic therapy, decompression of the collecting system with retrograde or anterograde drainage, or proceeding directly to nephrectomy in the setting of pyelonephritis.[6] In a retrospective review (2001-2015) of 74 patients with emphysematous pyelonephritis, there was an 8% overall mortality. Mortality on medical treatment alone was 50% to 70%, whereas it was 25% for medical management with emergency nephrectomy and 13.5% with combined medical and percutaneous drainage.[6] Emphysematous cystitis has about a 7% mortality, lower than that of emphysematous pyelonephritis.[7,8]

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CT scan revealing an enlarged kidney with little to no parenchyma and an associated obstructing stone courtesy of Medscape.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Xanthogranulomatous pyelonephritis and perinephric abscesses

Xanthogranulomatous pyelonephritis is a rare variant of chronic pyelonephritis that occurs in the setting of chronic inflammation associated with infection and obstruction.[1,9] It is characterized by the accumulation of lipid-laden foamy macrophages within the tissue. Kidney destruction with near-total or complete loss of renal function can ensue, often requiring nephrectomy.[1,9] The significant inflammatory response can make performing a nephrectomy challenging; an open (vs laparoscopic) approach may be beneficial.[10]

Perinephric abscesses are thought to occur from hematogenous bacterial spread or the rupture of an acute cortical abscess into the perinephric space.[1] These abscesses are commonly associated with diabetes mellitus.

Broad-spectrum antibiotics are the initial course of therapy, but drainage of the abscess is the mainstay of treatment.[1] Both percutaneous and open drainage approaches can be used; however, open drainage techniques have been associated with improved cure rates and reduced length of stay in the setting of multiloculated perinephric renal abscesses.[11]

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Bacterial Prostatitis and Prostatic Abscesses

CT scan revealing a prostatic abscess courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Bacterial Prostatitis and Prostatic Abscesses

Patients with acute bacterial prostatitis typically present with dysuria, spiking fevers, chills, perineal pain, and cloudy urine.[1] Usually, treatment with appropriate antibiotics elicits a rapid clinical response. However, if the spiking fevers persist, further investigation is warranted as there is concern for a prostatic abscess.[1]

The preferred imaging modality for suspected bacterial prostatitis or a prostatic abscess is transrectal prostate ultrasonography, but an abdominopelvic CT scan can also be obtained (shown).[1] The optimal treatment modality for a prostatic abscess is transurethral resection. Although percutaneous needle drainage can be attempted first, it is not recommended for large abscesses such as the one seen in the image above.[1]

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Vesicoureteral Reflux

Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Vesicoureteral Reflux

Vesicoureteral reflux (VUR) is characterized by the retrograde flow of urine from the bladder to the upper urinary tract.[12,13] This condition can be caused by ureteral anomalies (primary), as well as obstruction or stricture in the bladder neck or urethra (secondary).[13] VUR most often affects infants and young children (≤2 years), with a female preponderance, but it can occur in males, older children, and adults.[14] Although VUR is not the primary cause of pediatric UTIs, when it is associated with UTIs in children (30%-33%), complications with renal function and overall patient health may result.[12,13]

Although VUR may be asymptomatic, it is often discovered after a febrile UTI is documented and renal ultrasonography with voiding cystourethrogram is performed.[13] However, VUR also occurs in about 17% of children without UTIs.[12]

Treatment for VUR depends on multiple factors, including the reflux grade, patient's age, parental preference, and other variables.[12-15] Management options include medical, surgical, and observational. The goals of VUR care are to prevent recurring febrile UTIs, avert renal injury, and minimize the morbidity of treatment and follow-up.[12-15]

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Pyocystis

Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

Pyocystis

Pyocystis is a severe form of lower UTI that is defined as a large collection of purulent material within a bladder, commonly associated with patients with end-stage renal disease (ESRD), who do not produce enough urine to allow the bladder to be flushed out.[16] However, because of the greatly reduced urine output, pyocystis can be a frequently overlooked etiology of fever in patients with ESRD. Culture results are typically polymicrobial.

Affected patients often require Foley catheter placement and bladder irrigation to flush the static urine and purulent debris from the bladder.[16]

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Image courtesy of Josh Palka, DO.
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Urinary Tract Infections: Pathologies and Challenges

Josh Palka, DO | March 14, 2022 | Contributor Information

This image of transurethral resection of the prostate for outlet obstruction was obtained from a patient with BPH and recurrent UTIs.

Recurrent UTIs

In the workup of patients with recurrent UTIs, clinicians must determine whether these are truly recurrent UTIs or if the original UTI is persistent. Bacterial persistence is associated with closely occurring UTIs caused by the same organism, whereas recurrent UTIs are seen with different bacteria and occur over differing time periods.[1]

Patients must also be evaluated for other factors that can contribute to recurrent UTIs, including anatomic abnormalities, outlet obstruction, and kidney stones.[17] Repeat urine cultures are recommended.[18]

Recurrent UTIs commonly occur as ascending bacterial infections from gastrointestinal flora, and there is a female preponderance.[17] Women can be affected owing to postmenopausal changes in their vaginal microflora, which can be corrected with topical estrogen.[1,18] Clinicians may prescribe daily antibiotic prophylaxis to lower the risk of future UTIs in women of all ages with a history of recurrent UTIs. Common prophylactic antibiotics include nitrofurantoin, fosfomycin, and TMP-SMX.[18]

Recurrent UTIs may require surgical intervention (eg, calculi, fistulas, abscesses, VUR). Surgical options can range from minimally invasive procedures (eg, endoscopic or percutaneous) to more invasive (eg, laparoscopic or open approach).[17]

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References