Table 2

Association of bariatric surgery with first incident AKI, stratified by length of follow-up

PYEventsRate per 1000 PY (95% CI)Crude RR
(95% CI)*
P values Adjusted RR
(95% CI)
P values
All patients
Day 1–30
  Unexposed20300
  Bariatric surgery199525.1 (10.5 to 60.4)
>Day 30
  Unexposed7882546.9 (5.2 to 8.9)
  Bariatric surgery8061344.2 (3.0 to 5.9)0.62 (0.40 to 0.95)0.0270.37 (0.23 to 0.61)<0.001
All patients analysed by type of surgery§
Day 1–30
  Unexposed
  Gastric band
  Sleeve gastrectomy
  Gastric bypass
  Other
>Day 30
  Unexposed7882546.9 (5.2 to 8.9)
  Gastric band4614173.7 (2.3 to 5.9)0.54 (0.31 to 0.93)0.026
  Sleeve gastrectomy728<5 5.5 (2.1 to 14.6)0.80 (0.29 to 2.21)0.670
  Gastric bypass2655134.9 (2.8 to 8.4)0.71 (0.39 to 1.31)0.277
  Other630
All patients over whole period of follow-up
  Unexposed8085546.7 (5.1 to 8.7)
  Bariatric surgery8259394.7 (3.5 to 6.5)0.71 (0.47 to 1.07)0.0990.45 (0.28 to 0.72)0.001
  • Unexposed refers to the propensity-matched comparison group.

  • *Poisson regression model.

  • †Wald test.

  • ‡Poisson regression model adjusted for age at baseline, sex, calendar time, CKD at baseline, history of AKI, history of taking oral antidiabetics and BMI at baseline.

  • §No analysis for day 1–30 owing to sparse data.

  • ¶Cell counts <5 have been suppressed to ensure anonymity.

  • AKI, acute kidney injury; BMI, body mass index; CKD, chronic kidney disease; PY, person years; RR, rate ratio.