Can excretory phase computed tomography predict bacteremia in obstructive calculous pyelonephritis?

Purpose: Acute pyelonephritis (AP), a complication of urolithiasis, can be fatal if it progresses to septic shock. We aimed to evaluate the performance of excretory phase computed tomography (CT) in predicting bacteremia among AP patients with upper urinary tract calculi.

Methods: We reviewed medical records of 250 patients diagnosed with AP and upper urinary tract calculi and who were admitted to our institute. We analyzed 132 patients who underwent excretory phase CT. Excretory phase CT images were obtained 7 min after injection with the contrast agent. Obstruction was classified either as high or low grade. Univariate and multivariate analyses were performed to identify the risk factors of bacteremia.

Results: Of 132 patients, 73 (55.3%) had bacteremia. Escherichia coli was the most frequently identified pathogen in blood cultures. Univariate analysis demonstrated that high-grade obstruction on excretory phase CT and quick Sepsis-related Organ Failure Assessment (qSOFA) score ≥ 2 were correlated with bacteremia. In addition, the administration of vasopressors was significantly associated with bacteremia (31.5% vs. 6.8%; p < 0.001). Multivariate analysis identified high-grade obstruction on excretory phase CT [odds ratio (OR) 6.68; p < 0.001] and qSOFA score ≥ 2 (OR 3.59, p = 0.03) as independent risk factors for bacteremia.

Conclusions: Excretory phase CT images can be used to predict bacteremia by evaluating the degree of ureteral obstruction. The evaluation of the passage of urine shown by excretory phase CT is critical in patients with AP associated with upper urinary tract calculi.