Point-of-care ultrasound for the early diagnosis of emphysematous pyelonephritis: A case report and literature review

Abstract

Background: Emphysematous pyelonephritis (EPN) is a rare but fatal necrotic infection of the kidney, which usually leads to septic shock. Therefore, early diagnosis and optimized therapy are of paramount importance. In the past two decades, point-of-care ultrasound (POCUS) has been widely used in clinical practice, especially in emergency and critical care settings, and helps to rapidly identify the source of infection in sepsis. We report a rare case in which a "falls" sign on POCUS played a pivotal role in the early diagnosis of EPN.

Case summary: A 57-year-old man presented with fever and lumbago for 3 d prior to admission. He went to the emergency room, and the initial POCUS detected gas bubbles in the hepatorenal space showing a hyperechoic focus with dirty shadowing and comet-tail artifacts. This imaging feature was like a mini waterfall. His blood and urine culture demonstrated Escherichia coli bacteremia, and EPN associated with septic shock was diagnosed. The patient did not respond to broad-spectrum antibiotic treatment and a perirenal abscess developed. He subsequently underwent computed tomography-guided percutaneous catheter drainage, and fully recovered. We also review the literature on the sonographic features of POCUS in EPN.

Conclusion: This case indicates that a "falls" sign on POCUS facilitates the rapid diagnosis of severe EPN at the bedside.

Keywords: Case report; Emphysematous pyelonephritis; Point-of-care ultrasound; Review; Ultrasound; Urinary tract infection.

Figure 1

Point-of-care ultrasound of a “falls” sign and a sketch of this sign. A: Image on day 3 after symptom onset showing hyperechoic spots or patches (orange oblique arrow) collecting in the right hepatorenal space with dirty shadowing (white oblique arrow) and comet-tail artifacts (white asterisks); B: Chinese landscape painting illustrating a mini waterfall by Yu-Xin Wang.

Figure 2

Comparison of computed tomography scans of the right kidney. A: Image on day 3 after symptom onset showing gas bubbles (orange oblique arrow) in the right perirenal space and an enlarged kidney with perinephric fat stranding (PFS) (white oblique arrow); B: Image on day 7 after symptom onset showing gas bubbles plus an abscess in the right perirenal space (orange oblique arrow) and a more enlarged kidney with more PFS (white oblique arrow); C: Image on day 9 after symptom onset showing a pig-tail catheter (orange oblique arrow) in the right perirenal space and an enlarged kidney with PFS (white oblique arrow); D: Image on day 11 after symptom onset showing a pig-tail catheter (orange oblique arrow) in the right perirenal space and a normal-size kidney with clear perinephric fat (white oblique arrow).

Figure 3

Clinical course and vasopressor doses. Meropenem and tigecycline were prescribed on days 1-14. Percutaneous catheter drainage (PCD) was performed on day 5. The perinephric catheter was removed and the patient was discharged on day 14. ICU: Intensive care unit.

Figure 4

A-lines and B-lines in pulmonary ultrasound in our clinical practice and cartoon illustrating how different air-related artifacts in emphysematous pyelonephritis are produced. A: Point-of-care ultrasound (POCUS) of a healthy lung showing gradually diminished A-lines (the white arrows) and pleura lines (the orange arrows), and the equidistance between the lines; B: POCUS of lung edema showing B-lines (the white arrows); C: Cartoon showing how A-lines are produced. The ultrasound beams (the blue arrows) are repetitively reflecting between gas and the transducer with strength degradation; D: Cartoon showing how B-lines are produced. The ultrasound beam (the blue arrow) provokes resonance in the gas-fluid interface, emitting continuous waves back to the transducer (the small blue arrows); E: Cartoon showing how comet-tail artifacts are produced. The ultrasound beam is repetitively reflecting between the shallow and deep sides (the blue arrows) of gas bubbles with gradually diminished ultrasound beams returning to the transducer; F: Cartoon showing how dirty shadowing is produced. The ultrasound beam is reflecting in multiple directions (the blue arrows) deep into the gas.