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Emphysematous pyelitis (EP) is a rare infection of the urinary collecting system due to gas-forming bacteria. It is an uncommon form of acute pyelonephritis that has been reported sporadically in the literature. The present case of EP was complicated by renal calculi. The patient had surgery to remove the calculi 4 months after the initial diagnosis. During the 4-month interim between diagnosis and surgery, she had no antibiotic therapy. A presurgical CT showed the same stone burden with no evidence of abscess. There was a complete resolution of gas in the collecting system. At the 6-month follow-up evaluation, the patient was asymptomatic and the kidney remained stone-free.
KEYWORDS: Emphysematous pyelitis; Calculi; CT scan.
CORRESPONDENCE: Dr. Sataa Sallami, Department of Urology, La Rabta Hospital-University, Tunis 1007, Tunisia ().
CITATION: UroToday Int J. 2010 Jun;3(3). doi:10.3834/uij.1944-5784.2010.06.10
ABBREVIATIONS AND ACRONYMS: CT, computed tomography; EP, emphysematous pyelitis; EPN, emphysematous pyelonephritis; KUB, kidney, ureter, bladder.
Emphysematous (gas-forming) infections in the abdomen and pelvis represent potentially life-threatening conditions that require aggressive medical care that often includes surgical management. These infections frequently progress rapidly to sepsis in the absence of any early therapeutic interventions . Among the entities of gas-forming infections, there is a condition called emphysematous pyelitis (EP) where the prognosis is excellent, with rapid complete recovery after adequate medical treatment .
EP is used to describe the presence of gas from gas-forming bacteria that is limited to the urinary collecting system [1,2,3]. It usually occurs in patients with diabetes mellitus or obstructive conditions of the collecting system. The authors present a case of EP complicated by renal calculi.
An obese 71-year-old female presented to the authors' department with intermittent right-sided lumbar pain. Her history included hypertension and cerebral ischemic attack. Her medications included captopril (Lopril; Bosnalijek, Ukraine), aspirin, furosemide, and dipyridamole (Procardin; Medochemie, Hong Kong). She had no history of diabetes mellitus and she denied any history of hematuria or lower urinary tract symptoms.
Clinically, this patient showed no evidence of a fistula between the urinary tract and bowel, no history of trauma, and no history of instrumentation of the urinary tract (including Foley catheter placement). Physical examination was unremarkable.
Laboratory tests revealed normal serum creatinine, electrolyte, and glucose levels. White blood cell count was 7,800/mL. The urine culture was negative.
Plain kidney, ureter, bladder (KUB) radiography showed multiple radiopacities measuring 2 cm to 3 cm in diameter, located in the left kidney Figure 1. An ultrasound evaluation showed Grade 2 hydronephrosis that contained multiple echogenic stones within the dilated right kidney pelvis with dirty shadowing (ie, containing low-level echoes and reverberations). An intravenous urography (IVU) confirmed the presence of multiple renal stones (Figure 2).
Contrast computed tomography (CT) of the abdomen showed a dilated left urinary pelvis containing calculi and air only in the collecting system (ie, gas fluid levels in the cavities) Figure 3. The urinary bladder also showed the presence of air Figure 4. However, there were no gas pockets or fluid collections seen within the left renal parenchyma or in the left perinephric tissues. Diagnosis of EP was made based on the CT findings.
An emergency hospitalization was recommended, but the patient refused admission and was lost to the authors. Four months after the intial evaluation, the patient responded and was hospitalized. She had no antibiotic therapy during the 4-month period between evaluation and hospitalization.
At admission, the patient was afebrile and her vital signs were stable (blood pressure of 140/85 mm Hg; pulse rate of 72 beats per minute). Her abdomen was soft, revealing tenderness only at the right lumbar region without palpable mass.
A second CT scan showed the same stone burden, with no evidence of abscess. There was a complete resolution of gas in the collecting system.
Management of Calculi
Although the patient's white blood cell count was normal and blood and urine cultures were negative, the patient was given intravenous cephapirin sodium and metronidazole. Surgical nephrolithotomy was indicated under antibiotic therapy.
Intraoperatively, the renal pelvis and kidney dissection were easy and there were no signs of inflammation. At pelvic incision, the urine was clear with no evidence of air in the upper collecting system. A small stone was obstructing the ureteropelvic junction. Ten stones were extracted Figure 5. No evidence of a urodigestive fistula was found. The duration of intravenous treatment was 7 days.
The postoperative course was unremarkable. The patient was discharged with the prescription of oral antibiotics (ciprofloxacin) for 2 weeks. At the 6-month follow-up evaluation, the patient was asymptomatic and the kidney remained stone-free.
Gas in the urinary tract is a relatively rare occurrence that usually arises with urinary tract infection . The infections may manifest as cystitis, pyelonephritis, or pyelitis. EP is a rare, gas-forming, acute bacterial urinary tract infection that is associated with gas localized in only the renal collecting system [1,2,4]. The pathogenesis of emphysematous urinary tract infections remains poorly understood.
A common bacterial cause of EP is Escherichia coli (E. coli). Other culprit organisms include Klebsiella, Proteus, Citrobacter, Aerobacter, and Candida species [4,5]. It has been postulated that high glucose concentration in the tissues provides the substrate for organisms that can produce carbon dioxide and hydrogen by fermentation of sugar . However, bacterial gas production does not fully explain the pathologic and clinical manifestations of emphysematous urinary tract infections [6,7]. No organism was cultured from the urine sample or blood culture in the present case, so no comment can be made regarding the etiology.
Based on a CT classification scheme proposed by Wan et al , EP falls under Type II emphysematous pyelonephritis (EPN). EPN has been defined as an acute, severe, necrotizing infection of the renal parenchyma and perirenal tissue. It results in the presence of gas within the renal parenchyma, collecting system, or perinephric tissue.
EP and EPN are both associated with diabetes mellitus, but to different extent . Underlying, poorly-controlled diabetes mellitus is present in up to 90% of patients who develop EPN , compared with only 50% of patients with EP . EP typically accompanies urinary tract obstruction, and the cause of the obstruction is usually calculi . The present case did not have diabetes mellitus, but she had obstructing pelviureteric calculi.
EP is a benign condition with a low overall mortality rate when compared with EPN . Thus, it is important to distinguish between these 2 types of gas-forming renal infections because of the prognostic differences. The prognosis of EP is excellent, with rapid complete recovery after medical treatment . EP carries a mortality rate of up to 20% , which is significantly lower than 50% mortality for EPN .
The diagnosis of EP is often delayed because the clinical manifestation may be nonspecific and similar to the clinical presentation of uncomplicated acute pyelonephritis [2,4]. Roy et al  reported 5 patients with EP. Four patients presented with lumbar pain, fever, chills, and general health impairment, and 1 patient had septic shock. These symptoms are usually associated with upper-quadrant tenderness, which was present in the current case along with flank pain.
To the authors' knowledge, imaging findings in patients with EP have not been frequently reported in the literature . A typical feature seen in conventional radiography of EP is the presence of gas outlining the ureters and pelvicalyceal system; this appearance mimics gas pyelograms [4,5]. Although abdominal radiography usually allows easy detection of air, the sensitivity reported with radiography is low at 33% [4,10,11]. This low sensitivity is due to difficulty in differentiating renal gas from air in overlying loops of bowel. In the present case, a KUB film did not reveal any specific aspects.
Ultrasound findings of EP include high-amplitude echogenicities and posterior acoustic dirty shadowing within the renal sinus and anterior wall of the collecting system . In theory, the posterior shadowing in EP is typically dirty as opposed to the clean shadowing caused by calculus. Ultrasound provides less specific information about gas-producing renal infection because of potential confusion between air, renal calculi, or calcifications within the kidney .
The most specific imaging modality for diagnosis and follow-up of gas-containing infections of the urinary system is CT. In addition to evaluating renal parenchyma, it is possible to differentiate between gas and stones that locate in the collecting system and ureter; it is also possible to determine their diameters [2,4]. Therefore, CT is the current method of choice for diagnosis . CT is sensitive in demonstrating and precisely localizing air within the caliceal system and eliminating air within the kidney parenchyma and/or pararenal spaces . CT allows both accurate diagnosis and staging, thus reliably excluding the more fulminant EPN as a diagnosis if there are no gas pockets or fluid collections within the renal parenchyma or perinephric tissue .
EP should be differentiated from the reflux of air or gas from the bladder, or from ileal ureterosigmoidostomy. The spontaneous appearance of gas within the upper urinary tract has three main origins: (1) trauma and iatrogenic manipulation (ie, ureteral instrumentation, surgical procedure, or interventional radiologic procedure); (2) fistulous connection with a hollow viscus, especially in the gastrointestinal system; (3) reflux from the urinary bladder . All of these conditions should be eliminated before concluding that the diagnosis is EP.
The clinical management of EP and EPN are different. Intraparenchymal gas usually requires drainage or nephrectomy and is associated with a substantial mortality rate [2,5]. If the patient has EP and gas is localized to the collecting system with no obstruction, antibiotic therapy alone appears to be sufficient [2,4]. Coexisting obstruction to urine flow requires correction because it can limit the response to antibiotics.
EP is a rare upper urinary tract infection. The present case report provides additional information to the literature regarding the physiopathology of this condition. The diagnosis is made by CT, which helps to differentiate it from the more fulminant EPN. Efficient antibiotic therapy and treatment of urinary obstruction should be indicated in all cases.
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