Twelve studies reported the overall morbidity. There was significant heterogeneity between the studies (P = 0.002), and therefore, the random effects model was used. The meta-analysis showed that the overall morbidity did not differ significantly between the 2 groups (OR = 1.11, 95% CI [0.76, 1.64]) (see Figure 1B).
Incidence of Infectious Morbidity
Seven studies reported the incidence of infectious morbidity. There was significant heterogeneity among the studies (P < 0.001), and therefore, the random effects model was used. The meta-analysis showed that the incidence of infectious morbidity did not differ significantly between the 2 groups (OR = 1.62, 95% CI [0.70, 3.77]) (see Figure 1C).
Incidence of Wound Infection
Ten studies reported the incidence of wound infection. There was significant heterogeneity among the studies (P = 0.009), and therefore, the random effects model was used. The meta-analysis showed that the incidence of wound infection morbidity did not differ significantly between the 2 groups (OR = 1.46, 95% CI [0.69, 3.10]) (see Figure 1D).
Incidence of Intra-abdominal Abscess
Seven studies reported the incidence of intra-abdominal abscess. There was no significant heterogeneity among the studies (P = 0.04), and therefore, the fixed effects model was used. The meta-analysis showed that the incidence of intra-abdominal abscess did not differ significantly between the 2 groups (OR = 0.77, 95% CI [0.30, 1.93]) (see Figure 1E).
Incidence of Pancreatic Fistula
Six studies reported the incidence of pancreatic fistula. There was no significant heterogeneity among the studies (P = 0.44), and therefore, the fixed effects model was used. The meta-analysis showed that the incidence of pancreatic fistula did not differ significantly between the 2 groups (OR = 0.95, 95% CI [0.56, 1.61]) (see Figure 1F).
Incidence of Bile Leak
Six studies reported the incidence of pancreatic bile leak. There was no significant heterogeneity among the studies (P = 0.79), and therefore, the fixed effects model was used. The meta-analysis showed that the incidence of bile leak did not differ significantly between the 2 groups (OR = 1.61, 95% CI [0.74, 3.51]) (see Figure 1G).
Incidence of Delayed Gastric Emptying
Eight studies reported the incidence of delayed gastric emptying. There was no significant heterogeneity among the studies (P = 0.82), and therefore, the fixed effects model was used. The meta-analysis showed that the incidence of delayed gastric emptying did not differ significantly between the 2 groups (OR = 1.07, 95% CI [0.75, 1.54]) (see Figure 1H).
Publication Bias Analysis
A funnel plot was applied for publication bias analysis (Figure 2), which resulted in a symmetric inverted funnel shape in all plots. The results of Begg test indicate that there were no publication bias in all studies (P > 0.252).
Group Analysis Based on Drainage Time
Ten studies reported the duration of preoperative drainage, including 3 studies discussing a duration of <4 weeks (group I) and 7 discussing a duration of >4 weeks (group II). As shown in Figure 3, the overall mortalities of groups I and II were (OR = 0.66, 95% CI [0.28, 1.58]) and (OR = 0.75, 95% CI [0.50, 1.13]), respectively, which indicate that they did not differ from each other significantly. Besides, in groups of I and II, the overall morbidities were (OR = 1.90, 95% CI [1.33, 2.70]) and (OR = 1.61, 95% CI [0.68, 3.82]), respectively. When compared with nondrainage patients of group I, the overall morbidity of drainage patients increased by 7% to 23%, which was greater than that of nondrainage patients; whereas, the overall morbidity of group II was not obviously different between drainage and nondrainage patients. We speculated that longer drainage duration, for instance, >4 weeks, might help reduce the overall morbidity.
Group Analysis Based on Stent Material
Nine studies discussed the stent material (metal/plastic). In 7 studies, plastic stents were used and in the remaining 2, both metal and plastic stents were used. As shown in Figure 4, the overall mortalities of plastic and metal–plastic group were (OR = 0.88, 95% CI [0.58, 1.34]) and (OR = 0.14, 95% CI [0.02, 0.89]), respectively, and the overall morbidities of the 2 groups were (OR = 2.48, 95% CI [0.91, 6.77]) and (OR = 1.16, 95% CI [0.72, 1.86]), respectively. The overall morbidity was not affected by the stent material.
When compared with the nondrainage group, the overall mortality of the drainage group using metal–plastic stents was reduced by 0.5% to 6%; yet, the rates of the drainage group using plastic stents only were not significantly different. We conjectured that metal stents could reduce the overall mortality and possibly are superior to plastic ones.
It still remains controversial whether to perform preoperative biliary drainage on obstructive jaundice patients with indications for surgery routinely.4,13,23 Previous retrospective and prospective randomized controlled trials have drawn different conclusions. Some studies have reported that preoperative biliary drainage could reduce the length of a hospital stay, the postoperative infection rate, renal damage, and bleeding.24–26 Lygidakis et al27 suggested that preoperative biliary drainage could reduce the pressure within the biliary tract, improve liver function, and reduce perioperative bleeding and postoperative complications. Abdullah et al14 reported that preoperative biliary drainage could reduce the rate of wound infections and did not affect the overall mortality. However, some studies declared that preoperative biliary drainage can increase the chances of biliary infection and infectious complications.3,19,20 Pešková et al4 indicated that preoperative biliary drainage could also increase the overall morbidity. Studies have shown that many severe complications were caused by improper drainage.17 Despite the improvements in drainage technology, surgical conditions, and perioperative care, it is still unclear whether the outcome of preoperative drainage has caused any improvements. Hence, in the current study, articles from the past decade were selected for meta-analysis.
Preoperative drainage methods include external and internal drainage. External drainage can lead to insufficient bile in the intestines, and thus, weakened inhibition of intestinal bacteria causing endotoxemia.5 It may also cause malnutrition because of lipid malabsorption and fluid balance disorders because of bile loss. In contrast, internal drainage can significantly improve these drawbacks of external drainage. Materials used for internal drainage include plastic and metal stents. Plastic stents are inexpensive and easy to operate for repeated placement; however, its major disadvantage is the presence of 3 to 6 internal obstructions,28 which may result in recurrence of jaundice and increase the incidence of cholangitis.29–31 Compared with plastic stents, metal stents have a larger diameter when expanded, and the expansion time is notably longer.32–34 Wasan et al35 showed that metal stents could reduce the occurrence of cholangitis and intraoperative and postoperative complications. However, metal stents may also become obstructed through tumor ingrowth or overgrowth.36,37 We performed a meta-analysis on drainage subgroups using different stent materials and found that the overall mortality and morbidity of the subgroups using plastic stents were not significantly different from the nondrainage group. Compared with the nondrainage group, the overall morbidity of the drainage subgroup using plastic and metal stents was not significantly different, yet its overall mortality was significantly lower. Compared with using plastic stents only, the use of metal and plastic stents can reduce the overall mortality. This suggests that compared with plastic stents, metal stents can reduce mortality. However, there were only 2 studies that have used plastic and metal stents for internal drainage. The small number of available studies makes this conclusion unreliable.
Drainage time is still a rather controversial issue. The supporters of preoperative biliary drainage believe that the reason why preoperative biliary drainage did not have any benefits in some cases was that the drainage time was too short. As liver function recovery requires 4 to 6 weeks, even if the bilirubin level may have returned to normal prior to 4 weeks, the drainage time should last 4 to 6 weeks.4,20 However, an overly long drainage time may increase infectious morbidity. In the present study, a meta-analysis on studies with drainage times ≥4 weeks showed that the overall mortality and morbidity were not significantly different from that of the nondrainage group. A meta-analysis on studies with drainage times <4 weeks showed that the overall mortality was not significantly different from that of the nondrainage group, yet the overall morbidity of the former group was significantly higher than that of the latter group. This suggests that a drainage time ≥4 weeks can reduce overall morbidity compared with a drainage time <4 weeks. However, studies with drainage times ≥4 weeks showed relatively large heterogeneity. Sensitivity analysis revealed that the results obtained from the fixed effects and random effects models were different. Hence, this conclusion is not very reliable.
Thus, we believe that preoperative biliary drainage should not be routinely applied. However, for patients with severe jaundice (serum bilirubin level ≥150 μm/L), concomitant cholangitis, or severe malnutrition and patients who need a relatively long preoperative assessment and wait for a relatively long time before the surgery, preoperative drainage may be selectively applied.38 We suggest that the drainage time should >4 weeks, and metal stents should be used for drainage.
This study has limitations. First, the quality of the included studies was not high. Second, there was a relatively large heterogeneity among different studies regarding the comparison of overall morbidity, infectious morbidity, and wound infection, and the results obtained from using the fixed effects and random effects models were different, thereby leading to unreliable conclusions. The main cause of the heterogeneity was that different studies defined the complications differently, and the evaluation criteria were different. Hence, future large-scale, large-sample, multicenter randomized controlled trials using standardized assessment indicators are still needed.
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Copyright © 2014 The Authors. Published by Wolters Kluwer Health, Inc. Health, Inc. All rights reserved.
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