A Cochrane review included 6 studies with a total of 520 subjects. Four trials compared percutaneous transhepatic biliary drainage with direct surgery, and 2 trials used endoscopic sphincterotomy and stenting as the method of drainage. The proportion of patients with malignant obstruction varied between 60% and 100%. There was no significant difference in mortality between the pre-operative biliary drainage group and the direct surgery group (Table 1).
| Outcomes | No of Participants (studies) | Assumed risk (control) | Corresponding risk | Relative effect (95% CI) |
|---|---|---|---|---|
| Mortality | 520 (6) | 133 per 1000 | 149 per 1000 (97 to 228) | RR 1.12 (0.73 to 1.71) |
| Morbidity | 503 (6) | 361 per 1000 | 599 per 1000 (462 to 780) | Rate ratio 1.66 (1.28 to 2.16) |
The overall serious morbidity was higher in the pre-operative biliary drainage group. There was no significant difference in the length of hospital stay (2 trials, 271 patients; MD 4.87 days; 95% CI -1.28 to 11.02; P = 0.12) between the two groups.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and lack of blinding) and by imprecise results (few patients and wide confidence intervals).