Effects on renal outcome of concomitant acute pyelonephritis, acute kidney injury and obstruction duration in obstructive uropathy by urolithiasis: a retrospective cohort study

Abstract

Objective: Obstruction release from urolithiasis can be delayed with a lack of suggested time for preventing the deterioration of renal function. The objective of this study was to investigate the effect of obstruction duration, concomitant acute kidney injury (AKI) or acute pyelonephritis (APN) during the obstruction on the prognosis of renal function.

Design: Retrospective cohort study.

Setting and participants: 1607 patients from a urolithiasis-related obstructive uropathy cohort, between January 2005 and December 2015.

Outcome measures: Estimated glomerular filtration rate (eGFR) decrease ≥30% and/or end-stage renal disease (ESRD), and eGFR decrease ≥50% and/or ESRD, according to obstruction duration, AKI and APN accompanied by obstructive uropathy.

Results: When the prognosis was divided by obstruction duration quartile, the longer the obstruction duration the higher the probability of eGFR reduction >50% (p=0.02). In patients with concomitant APN or severe AKI during hospitalisation with obstructive uropathy, an eGFR decrease of >30% and >50% occurred more frequently, compared with others (p<0.001). When we adjusted for sex, age, hypertension, diabetes mellitus, APN, AKI grades and obstruction release >7 days for multivariate analysis, we found that concomitant APN (HR 3.495, 95% CI 1.942 to 6.289, p<0.001), concomitant AKI (HR 3.284, 95% CI 1.354 to 7.965, p=0.009 for AKI stage II; HR 6.425, 95% CI 2.599 to 15.881, p<0.001 for AKI stage III) and an obstruction duration >7 days (HR 1.854, 95% CI 1.095 to 3.140, p=0.001) were independently associated with an eGFR decrease >50%. Tree analysis also showed that AKI grade 3, APN and an obstruction duration >7 days were the most important factors affecting renal outcome.

Conclusions: In patients with urolithiasis-related obstructive uropathy, concomitant APN was strongly associated with deterioration of renal function after obstruction release. The elapsed time to release the obstruction also affected renal function.

Keywords: acute pyelonephritis; acute renal failure; chronic renal failure; nephrolithiasis; obstructive uropathy; urolithiasis.

Figure 1

Performed obstruction release procedures by APN, stone size and obstruction duration. (A) Percutaneous nephrostomy was performed more frequently in patients with APN compared with non-APN patients (10.2% vs 2.0%). (B) Stone size was significantly different according to the obstruction release method (p<0.001). Patients who had the obstruction released through percutaneous nephrostomy showed the longest obstruction duration. APN, acute pyelonephritis; ESWL, extracorporeal shock wave lithotripsy.

Figure 2

Kaplan-Meier curves for renal outcomes. (A, B) When the prognosis was evaluated by quartile of obstruction duration of all patients, the longer the obstruction duration the greater the likelihood of a decrease in GFR of more than 30% (log-rank p for pooled analysis=0.052, pairwise analysis; p=0.009 for 1Q vs 3Q, p=0.037 for 2Q vs 3Q) (A) and a decrease in GFR of more than 50% (p for pooled analysis=0.016, pairwise analysis; p=0.002 for 2Q vs 3Q, p=0.022 for 2Q vs 4Q) (B). (C, D) When we compared the results of the two groups, there was a significant increase in the possibility of GFR reduction >30% (p=0.022) (C) and >50% (p=0.003) (D) in group 2. 1Q, first quartile; 2Q, second quartile; 3Q, third quartile; 4Q, fourth quartile; eGFR, estimated glomerular filtration rate; GFR, glomerular filtration rate; Obst, obstruction.

Figure 3

Kaplan-Meier curves for renal outcomes by occurrence of APN and/or AKI. (A, B) Patients with APN were significantly more likely to have a GFR reduction >30% (p<0.001) (A) and a GFR reduction >50% (p<0.001) (B). (C, D) In patients with severe AKI of grade II or III, the probability of GFR reduction >30% (p for pooled analysis <0.001, HR 1.58, 95% CI 1.37 to 1.82, pairwise analysis; p<0.001 for no AKI vs AKI stage II or III, and AKI stage I vs stage II or III) (C) and >50% (p for pooled analysis <0.001, HR 2.62, 95% CI 2.05 to 3.34, pairwise analysis; p<0.001 for no AKI vs AKI stage II or III, p=0.035 for AKI stage I vs II, p<0.001 for AKI stage I vs III, and p=0.001 for AKI stage II vs III) (D) was significantly higher than the others. (E, F) The prognosis was best when neither AKI nor APN was present, and the prognosis was progressively worse with AKI alone, APN alone, and both AKI and APN, consecutively (p for pooled analysis <0.001, HR 1.50, 95% CI 1.33 to 1.71, pairwise analysis: p=0.029 for AKI(−)APN(−) vs AKI(+), p=0.027 for AKI(−)APN(−) vs APN(+), p<0.001 for AKI(−)APN(−) vs AKI(+)APN(+), and p<0.001 for AKI(+) vs AKI(+)APN(+) (E); p<0.001 for pooled analysis, HR 2.18, 95% CI 1.75 to 2.71, pairwise analysis: p=0.024 for AKI(−)APN(−) vs AKI(+), p<0.001 for AKI(−)APN(−) vs AKI(+)APN(+), and p<0.001 AKI(+) vs AKI(+)APN(+) (F)). APN, acute pyelonephritis; eGFR, estimated glomerular filtration rate; GFR, glomerular filtration rate.

Figure 4

Tree analyses. (A) In a decision tree model, AKI was the most important risk factor for the GFR decrease >50% (p<0.001). The second most important risk factor was AKI stage II (p=0.03). An age >49 years at the time of obstructive uropathy was selected at the next node in the group of patients with AKI stage I (p=0.019). Concomitant APN during the obstruction episode was presented for the next node in the group of patients without AKI and the obstruction duration is <7 days (p=0.002). An obstruction duration >7 days was selected at the next node, in the group of patients without AKI (p=0.035). (B) In a survival tree analysis with the variables sex, age, APN, AKI stage and obstruction duration groups, AKI stage III (p<0.001) was the most potent factor for the development of a GFR decrease >50%; APN was the second highest factor (p<0.001). An obstruction duration of more than 7 days (p=0.007) was also an independent risk factor for major renal outcomes in the survival tree analysis. AKI, acute kidney injury; APN, acute pyelonephritis; GFR, glomerular filtration rate.