Defining the Economic Burden of Venous Thromboembolism After Surgery for Inflammatory Bowel Disease: A National Inpatient Sample Study

BACKGROUND: Venous thromboembolism (VTE) may be considered an extra-intestinal manifestations of inflammatory bowel disease (IBD) related to inflammation associated hypercoagulability, and at least 4% of patients requiring surgery for IBD develop a VTE post-operatively. However, the economic burden associated with VTE after surgery for IBD has not been reported. Therefore we aimed to use a large national database to define the rate of post-operative VTE, and VTE-associated healthcare costs.

METHODS: A retrospective, cross-sectional analysis was performed using National Inpatient Sample (NIS) dataset from 2010 – 2014. The International Classification of Disease 9th edition (ICD-9) diagnostic and procedure codes were used to identify patients with primary diagnosis of Crohn’s disease (CD) or Ulcerative colitis (UC) who underwent major abdominopelvic surgery. VTE included any extremity DVT, pulmonary embolism, portomesenteric venous thrombosis, and cerebral venous sinus thrombosis. The national VTE rate and VTE associated costs were estimated using the sampling weights provided and following explicit instructions given by Healthcare Cost and Utilization Project (HCUP).  Univariate and multivariate logistic regression models were used to compare patient characteristics, hospital characteristics and outcomes between VTE and non-VTE groups. The total average direct costs in dollars were then compared between the two groups using linear regression accounting for complex survey design, and the resulting difference, in dollars, extrapolated to the national population. P-values <0.05 were considered statistically significant. 

RESULTS: Any VTE was identified in 1,656 (5.3%) out of a total of 31,242 patients.  On univariate analysis, older age, white race, higher Elixhauser comorbidity score, UC diagnosis, hospital transfer prior to surgery, larger bed size and urban teaching hospital were associated with VTE; conversely, elective surgery, laparoscopic approach and colectomy (compared to proctectomy and >1 type of resection) were associated with lower risk of VTE.  On multivariate analysis age, Elixhauser score, resection type, transfer status, hospital bed size, location and teaching status of hospital were independently associated with VTE. Proctectomy and >1 type of resection were independent factors associated with increased risk of VTE compared to colectomy alone (OR 1.5, 95% CI 1.3 – 1.9; OR 1.4, 95% CI 1.2 -1.6 respectively; both p<0.001). In terms of outcomes, patients who developed VTE had an increased length of stay (11.3 vs. 7.6 days; p<0.001) and higher inpatient mortality (5.4% vs 3.7%; OR 1.5, 95% CI 1.2– 1.8; p<0.001) compared to the non-VTE cohort. Direct costs were significantly higher in the VTE group, with an addition cost of $14,939 (95% CI $12,369 - $17,510, p <0.001) per admission. After adjusting for clinically relevant covariates, the cost difference was $10,507 (95% CI $9,649 – $11,365, p<0.001). Nationwide, the additional cost of VTE was estimated to be $17,031,847 annually.

CONCLUSION(S): VTE after abdominopelvic surgery for IBD occurs in >5% of patients nationally, and is associated with additional costs of $10,000 per patient, translating into over $17 million dollars in the United States annually. Novel screening and prophylactic regimens are sorely needed to reduce this morbid, costly, and potentially avoidable complication.