Perinephric Fat Stranding Is Associated with Elevated Creatinine Among Patients with Acutely Obstructing Ureterolithiasis

Introduction: Pyelovenous/pyelolymphatic backflow from acute ureteral obstruction, manifesting radiologically as perinephric fat stranding (PFS), may result in elevated serum creatinine. Among patients with acutely obstructing ureterolithiasis, we evaluated the relationship between degree of PFS and changes in serum creatinine from baseline. Methods: Our tertiary care center's radiology dictation system (Fluency Discovery, M Modal) was queried for noncontrast abdominopelvic CT studies obtained in the Emergency Department for patients with obstructing ureteral calculi from 7/2015 to 4/2016. A single radiologist blinded to clinical data reviewed all CT scans and coded stone size, location, severity of hydronephrosis, and degree of PFS (none, mild, moderate, severe). For patients who met imaging criteria, a retrospective chart review was performed. Results: We evaluated 148 patients with mean age of 46 years (SD 14.6), 56.0% (n=83) were male. On univariate analysis, moderate-severe perinephric stranding was associated with elevated creatinine from baseline (OR 2.93, p=0.03). Mean creatinine increased as the severity of stranding increased (none Cr=0.978mg/dL, mild Cr=0.983mg/dL, moderate Cr=1.165mg/dL, severe Cr=1.370mg/dL; p<0.01). An increase in creatinine from baseline was not associated with greater severity of hydronephrosis (OR 0.504, p=0.189). There was no association between degree of PFS and severity of hydronephrosis, positive urine culture, stone location, or symptom duration (p>0.05). On regression analysis controlling for positive urine culture and degree of hydronephrosis, there remained an association between elevated serum creatinine from baseline and moderate-severe PFS (OR 9.0, p=0.01). Conclusions: Among patients with acute obstructive ureterolithiasis, moderate-severe PFS was associated with elevated serum creatinine from baseline. This elevated creatinine was not explained by the obstructed kidney alone, as there was no association between the severity of hydronephrosis and increased creatinine. Pyelovenous/pyelolymphatic backflow resulting in PFS may be a contributing factor to elevated serum creatinine in this setting.