conversion from laparoscopic to open surgery is common in colorectal surgery with an incidence of 10% to 23% . many studies have examined risk factors for conversion in laparoscopic colorectal surgery in an effort to identify high - risk patients . some of the reported risk factors include high body mass index , americans society of anesthesiology score > 2 , and the surgeon 's operative experience . there is limited data regarding outcomes of patients who had conversion from laparoscopic to open colorectal surgery . also , the best surgical approach ( laparoscopic vs. open ) for high - risk patients is unclear . there is controversy regarding the outcomes of patients who required conversion during laparoscopic colorectal operations . some previously published data demonstrates poor outcomes with up to 50% morbidity rate in patients requiring conversion . longer operative time for colorectal laparoscopic surgery and a high rate of conversion to open surgery in high - risk patients has raised concerns about benefits of laparoscopic surgery in this subset of patients . also , higher local recurrence and reduced cancer - free survival have been reported in colorectal cancer patients who had conversion from laparoscopic to open procedures . however , some studies report only a small difference in outcomes of patients who underwent conversion and justify implementation of laparoscopic surgery into daily practice . deciding on surgical technique in high - risk patients while considering most previous studies had limited numbers of patients ; therefore , a large nationwide study analyzing the contemporary rate of conversion and the impact of conversion on outcomes of colorectal patients is needed . using a large database , we aim to report contemporary rates of conversion and outcomes of converted procedures compared with planned open and successfully completed laparoscopic operations . this study was performed using the nis ( national inpatient sample ) database from january 1 , 2009 , to december 31 , 2012 . the nis database is the largest publically available all - payer inpatient care database in the united states and contains data on > 7 million hospital stays each year . approval for use of the nis data in this study was obtained from the human research protection of the university of california , irvine medical center and the nis . we analyzed discharge data on patients who had undergone colorectal resections for the diagnoses of benign or malignant colorectal tumors , diverticular diseases , crohn disease , and ulcerative colitis using the procedural and diagnosis codes as specified by the international classification of diseases , ninth revision , clinical modifications ( icd-9-cm ) . to identify patients who underwent colorectal resection the icd-9 procedure codes of 17.31 to 17.39 , 45.71 to 45.76 , 45.81 patients ' diagnoses were defined based on the following icd-9 codes : malignant neoplasm of colon and rectum ( 153.0153.9 , 154.0 , 154.1 , 230.3 , and 230.4 ) , benign neoplasm of colon and rectum ( 211.3 , 211.4 ) , diverticulosis ( 562.10 and 562.12 ) , diverticulitis ( 562.11 and 562.13 ) , crohn disease ( 555.0 , 555.9 ) , and ulcerative colitis ( 556.0556.9 ) . conversion of laparoscopic surgery to open surgery was defined as the icd-9 diagnostic code of v64.41 . patients were excluded if they were younger than 18 years old or did not undergo colon or rectal resection . preoperative factors analyzed , as conveyed in table 1 , included patient characteristics ( age , sex , and race ) and 12 comorbid conditions including chronic pulmonary disease , chronic renal failure , fluid and electrolyte disorders , obesity ( body mass index 30 kg / m ) , hypertension , diabetes mellitus , metastatic cancer , liver disease , coagulopathy , alcohol abuse , history of previous abdominal surgery , and weight loss > 10% in the preceding 6 months . other factors analyzed included pathologic conditions ( crohn disease , ulcerative colitis , colorectal cancer , diverticulosis or diverticulitis , and benign colorectal tumor ) , procedure type ( cecectomy , right colectomy , left colectomy , transverse colectomy , sigmoidectomy , and proctectomy ) , surgical techniques ( laparoscopic , open , and converted procedures ) , and postsurgical complications ( intra - abdominal infection , acute renal failure , acute respiratory failure , deep vein thrombosis , urinary tract infection , pulmonary embolism , wound infection , wound disruption , bowel obstruction , postoperative prolonged ileus , and hospitalization for > 7 days from admission date ) . patients were divided into 3 groups : successful laparoscopic surgery , open surgery , and conversion from laparoscopic to open surgery . risk - adjusted analysis was performed to compare postoperative complications of the 3 groups of patients . female sex , age < 70 years , and benign colorectal tumor were used as reference data points for comparison in line with the literature . demographics of patients who have undergone colon and rectal surgery in the united states , nis 20092012 values are n ( % ) unless otherwise indicated . multivariate analysis using logistic regression was used to compare outcomes of the 3 groups of surgical techniques ( open , laparoscopic , and laparoscopic procedures that required conversion ) . p values < .05 were considered statistically significant . for each outcome , the adjusted odds ratio ( aor ) with a 95% confidence interval ( 95% ci ) was calculated and reported to estimate the relative risk associated with each surgical technique . adjustments were made for age , sex , race , chronic pulmonary disease , chronic renal failure , history of abdominal surgery , obesity , hypertension , diabetes mellitus , metastatic cancer , liver disease , coagulopathy , alcohol abuse , weight loss , type of admission , type of the procedure , type of surgical technique , and pathology type . multivariate analysis using logistic regression was used to compare outcomes of the 3 groups of surgical techniques ( open , laparoscopic , and laparoscopic procedures that required conversion ) . p values < .05 were considered statistically significant . for each outcome , the adjusted odds ratio ( aor ) with a 95% confidence interval ( 95% ci ) was calculated and reported to estimate the relative risk associated with each surgical technique . adjustments were made for age , sex , race , chronic pulmonary disease , chronic renal failure , history of abdominal surgery , obesity , hypertension , diabetes mellitus , metastatic cancer , liver disease , coagulopathy , alcohol abuse , weight loss , type of admission , type of the procedure , type of surgical technique , and pathology type . the most prevalent comorbidities included hypertension ( 52.5% ) and diabetes mellitus ( 18.5% ) . the most common laparoscopic colorectal procedure was right colectomy ( 41.2% of all laparoscopic procedures ) followed by sigmoidectomy ( 40.3% ) . among patients who underwent planned laparoscopic colorectal resection , 48,265 patients ( 14.3% ) had conversion to open surgery . the mean length of total hospital stay was 9 days in patients with conversion , while patients who had successfully laparoscopic surgery had mean hospitalization of 6 days . the mean risk - adjusted difference in hospitalization length was statistically significant ( mean difference = 2 days ; 95% ci , 1.601.70 ; p < .01 ) . the mortality rate in patients who underwent laparoscopic colorectal resection with and without conversion was 1.4% and 0.6% , respectively , while the adjusted risk of mortality in patients who underwent conversion was higher than in patients without conversion ( aor , 1.61 ; 95% ci , 1.451.78 ; p < .01 ) . also , the risk - adjusted mortality of patients who underwent planned open surgery was higher than for converted patients ( 3.9% vs. 1.4% ; aor , 1.70 ; 95% ci , 1.571.85 ; p < .01 ) . the mean hospital charge was $ 77 186 in patients with conversion , while patients who underwent successfully completed laparoscopic surgery had a mean hospital charge of $ 56 032 . the mean difference in hospital charge was statistically significant ( mean difference = $ 12 215 ; 95% ci , $ 11 648-$12 782 ; p < .01 ) . the risk - adjusted analysis for postsurgical complications associated with conversion of laparoscopic surgery to open surgery is reported in table 2 . specific postsurgical complications linked with conversion of laparoscopic surgery include intra - abdominal abscesses ( aor , 2.64 ; p < .01 ) , and postoperative wound infection ( aor , 2.38 ; p < .01 ) . hemorrhagic complications and wound infection in converted procedures were more than in both laparoscopic and planned open procedures ( table 2 ) . risk - adjusted analysis for postoperative complications of open and converted procedures compared with laparoscopic procedures values are n ( % ) unless otherwise indicated . the risk of conversion of laparoscopic surgery to open surgery is reported by perioperative factors and type of colorectal resection in tables 3 and 4 . factors such as history of previous abdominal surgery ( aor , 3.50 ; p < .01 ) and presence of metastatic cancer ( aor , 1.73 ; p < .01 ) have strong associations with conversion . also , compared with right colectomy procedure , the highest risk of conversion exists in proctectomy procedure ( aor , 2.81 ; p < .01 ) followed by transverse colectomy ( aor , 1.88 ; p < .01 ) . risk - adjusted analysis of factors associated with conversion of laparoscopic colorectal surgery to open surgery abbreviations as in table 2 . risk - adjusted analysis of conversion of laparoscopic colorectal surgery to open by procedure type abbreviations as in table 2 . table 5 estimates the increased risk of conversion associated with the presence of multiple risk factors in colorectal surgery . for example , patients with history of previous abdominal surgery who were admitted emergently with one of the comorbidities of liver disease , obesity , or metastatic cancer had at least 7 times increased risk of conversion . multivariate risk estimating of conversion in colon and rectal surgery patients ( increased risk calculated compared with female patients admitted nonemergently without any comorbidity ) finally , table 6 describes the associations between preoperative variables and mortality of patients who underwent converted procedures . conversion of laparoscopic to open colorectal surgery is associated with increased mortality and morbidity rates , as well as an increase in length of hospitalization . however , the outcomes of patients who required conversion are still better than those of patients who underwent planned open colorectal operations . this study reinforces implementation of laparoscopic surgery into daily practice in colorectal surgery . also , considering the prognosis of patients who underwent converted laparoscopic procedures compared with patients who underwent open colorectal procedures , laparoscopic surgery in high - risk patients ( even accepting higher chance for conversion ) may still have benefits . our results show that laparoscopic colorectal resectional surgery has a contemporary rate of 43.5% in the united states . this is in line with the previous report of 41.6% rate of laparoscopic colorectal surgery by the surgical care and outcomes assessment program collaborative in 2010 . reported the use of laparoscopic procedures in colorectal surgery increased from 23.3% in 2005 to 41.6% in 2010 . the conversion rate of laparoscopic surgery has been previously reported between 5% and 29% in colorectal surgery.the wide variance of conversion rate is related to the patient selection , surgeon 's experience , and procedure - related factors that affect the need for conversion in different studies . however , the conversion rate in colorectal surgery remains higher than for most other abdominal laparoscopic procedures such as cholecystectomy ( 4.9%)or splenectomy ( 5% ) . our results show proctectomy and right colectomy have the highest and the lowest rates of conversion , respectively . high conversion rates of proctectomy in colorectal surgery have been previously reported . also , patients suffering from crohn disease have the highest conversion rate for any pathologic condition . the incidence of conversion in patients suffering from crohn disease in this study was 23.2% . also , risk adjustment shows that crohn disease increases the risk of conversion > 2 times than do benign colorectal tumors . this is in line with the previous report by schmidt et al of significant increase in conversion rate of laparoscopic colectomy for patients suffering from crohn disease . converted laparoscopic procedures have higher mortality and overall morbidity than do successfully completed laparoscopic procedures . we reinforce previous reports of an increased risk of wound infection , prolonged hospitalization , and postoperative ileus with conversion compared with successful laparoscopic surgery . other postoperative complications we found that have associations with conversion included intra - abdominal abscess , acute renal failure , respiratory failure , myocardial infarction , pulmonary embolism , hemorrhagic complications , pneumonia , wound disruption , postoperative bowel obstruction , and urinary tract infection . our result reinforces the importance of controlling the correctable risk factors for conversion including surgeon - related factors ( learning curve , experience , technical ability ) by adequate training . converted laparoscopic procedures , compared with planned open colorectal procedures , have lower rates of mortality and overall morbidity . although converted laparoscopic procedures are performed with open surgical techniques and outcomes of such patients should not be better than planned open procedures , our results show mortality and postoperative complications were lower in converted procedures versus open procedures . this can be partly be explained with the difference in case selection between laparoscopic and open surgery , and partly by the progress made ( eg , mobilization ) prior to conversion . further studies are indicated to compare outcomes of converted colorectal operations with planned open operations in 2 complete homogeneous groups of patients . after risk adjustment with a multivariate analysis , wound infection , postoperative ileus , and postoperative hemorrhagic complications in patients who underwent converted procedures are higher than both open and completed laparoscopic procedures . further studies are indicated to confirm the significant increase of these 3 complications in patients undergoing converted procedures . our study , which represents the largest to date on this topic , shows that 13 preoperative factors have associations with conversion of laparoscopic surgery to open surgery . also , we confirm the previous reports of older age , male sex , and obesity as risk factors of conversion of laparoscopic surgery . surprisingly , male sex has been cited as a predictive factor of conversion multiple times . it can be best explained by the differences in pelvic anatomy between male and female sexes and the higher amount of visceral obesity . patients suffering from metastatic cancer and liver disease have increased risk of conversion of laparoscopic surgery . our results show metastatic cancer and liver disease increase the risk of conversion of operation 73% and 27% , respectively . the higher rate of conversion in patients with advanced cancer has been reported previously . emergently admitted patients with a history of previous abdominal surgery and comorbidities including liver disease , obesity , or metastatic cancer have at least a 7 times higher risk of conversion than do patients admitted nonemergently without any comorbidities . because comorbidities of liver disease , obesity , and metastatic cancer are not acutely correctable risk factors , open planned surgery for such high - risk patients with multiple risk factors may have benefits . although none of the identified risk factors is a contraindication to laparoscopic surgery , using this information may help surgeons in estimating the risk of conversion and expected outcomes for high - risk patients . finally , age > 70 years and coagulopathy have strong associations with mortality of patients who underwent converted procedures . this study is a retrospective study of an immense database and is subject to selection bias and coding errors . also , a wide variety of hospital settings and surgeons ' expertise can affect the study results . the 3 groups of patients compared in the study were not 3 homogeneous groups of patients and their demographic data , comorbidities , and disease stage varied . due to the restrictions of the database , some of the potentially important factors , such as the reason for the conversion and surgeon - related factors ( eg , surgeon 's experience ) , were not included in this study . despite these limitations , this study is one of the most comprehensive and largest studies investigating outcomes of conversion of laparoscopic colorectal surgery to open surgery . this study is a retrospective study of an immense database and is subject to selection bias and coding errors . also , a wide variety of hospital settings and surgeons ' expertise can affect the study results . the 3 groups of patients compared in the study were not 3 homogeneous groups of patients and their demographic data , comorbidities , and disease stage varied . due to the restrictions of the database , some of the potentially important factors , such as the reason for the conversion and surgeon - related factors ( eg , surgeon 's experience ) , were not included in this study . despite these limitations , this study is one of the most comprehensive and largest studies investigating outcomes of conversion of laparoscopic colorectal surgery to open surgery . although patients with converted procedures have higher rates of morbidity and compared with successfully completed laparoscopic procedures , morbidity and mortality of converted patients are still lower than those of planned open colorectal procedures . wound infection , postoperative ileus , and postoperative hemorrhagic complications in patients who underwent converted procedures are higher than for both open and successfully completed laparoscopic procedures . in colorectal resectional operations , crohn disease patients have the highest risk of conversion of any pathology . a history of previous abdominal surgery is the most important predictor of conversion in colorectal surgery . among procedures , proctectomy has the highest risk of conversion . the most important mortality predictor of patients who underwent converted operations are age > 70 years and coagulopathy . improved control of coagulation disorders may decrease postoperative mortality of such patients .
objectives : there is limited data regarding the outcomes of patients who undergo conversion to open surgery during a laparoscopic operation in colorectal resection . 
 we sought to identify the outcomes of such patients.methods:the nis ( national inpatient sample ) database was used to identify patients who had conversion from laparoscopic to open colorectal surgery during the 2009 to 2012 period . 
 multivariate regression analysis was performed to identify risk - adjusted outcomes of conversion to open surgery.results:we sampled 776 007 patients who underwent colorectal resection . 
 337 732 ( 43.5% ) of the patients had laparoscopic resection . 
 of these , 48 265 procedures ( 14.3% ) were converted to open surgery . 
 the mortality of converted patients was increased , when compared with successfully completed laparoscopic operations , but was still lower than that of open procedures ( 0.6% vs. 1.4% vs. 3.9% , respectively ; adjusted odds ratio [ aor ] , 1.61 and 0.58 , respectively ; p < .01 ) . 
 the most common laparoscopic colorectal procedure was right colectomy ( 41.2% ) . 
 the lowest rate of conversion is seen with right colectomy while proctectomy had the highest rate of conversion ( 31.2% vs. 12.9% , aor , 2.81 , p < .01 ) . 
 postsurgical complications including intra - abdominal abscess ( aor , 2.64 ) , prolonged ileus ( aor , 1.50 ) , and wound infection ( aor , 2.38 ) were higher in procedures requiring conversion ( p < .01).conclusions : conversion of laparoscopic to open colorectal resection occurs in 14.3% of cases . compared with patients who had laparoscopic operations , 
 patients who had conversion to open surgery had a higher mortality , higher overall morbidity , longer length of hospitalization , and increased hospital charges . 
 the lowest conversion rate was in right colectomy and the highest was in proctectomy procedures . 
 wound infection in converted procedures is higher than in laparoscopic and open procedures .