Table 2.
Incidence rate ratio of renal stone event in patients and controls before and after surgery
| Group
|
Before surgery
|
After surgery
|
P value*
|
|||||
|---|---|---|---|---|---|---|---|---|
| Events/years
|
Incidence rate ratio (95% CI)
|
Events/years
|
Incidence rate ratio (95% CI)
|
|||||
| Patients
|
Controls
|
Patients
|
Controls
|
|||||
| All patients | 271/9229 | 20/27 670 | 40.6 (31.0 to 53.3) | 112/3661 | 22/12 038 | 16.9 (12.1 to 23.6) | <0.01 | |
| Patients with stones before operation | — | — | — | 97/1111 | 4/3 476 | 75.9 (45.8 to 125.5) | — | |
| Patients without stones before operation | — | — | — | 15/2517 | 18/8 550 | 2.8 (1.5 to 5.5) | — | |
| Patients with strictures of ureters or hydronephrosis | 3/9229 | 27/27 670 | 9.0 (1.4 to 58.1) | 9/3631 | 1/12 038 | 29.8 (7.9 to 112.7) | 0.30 | |
*
Incidence rate ratio before surgery compared with incidence rate ratio after surgery (Poisson regression).