Outcomes of inguinal hernia surgery : Combining and exploring data from national registers in Sweden

Abstract

Surgery for inguinal hernia is one of the most frequent operations in the world. In this thesis, data from the Swedish Hernia Register are combined with results from patient related outcome measures as well as with other registers. The aim is to explore different aspects of hernia surgery to improve the outcomes. In paper I the cover rate and the quality of data in the Swedish Hernia register is described. Between 2013 and 2018 the data quality was assessed by visiting 55 hospitals. At each hospital 50 operations were randomly selected and 27 variables in the register were compared with the medical records. In total 73,764 variables were examined and 98% were found to be correct. The cover rate was evaluated between 2014 and 2018. Data from 46 hospitals was collected on site and all operations in the medical records were compared to register data. The total cover rate was 97%. In paper II the impact of a self-gripping mesh on postoperative pain and the risk of reoperation for recurrence was assessed. Data from the Swedish hernia register was combined with results from patient related outcome measures. Individuals offered an open anterior mesh repair between 2012 and 2016 with self-gripping mesh and lightweight mesh were compared. Inguinal pain questionnaire was sent out to all patients one year after surgery. After exclusions 18,370 operations were included. There was no difference in the rate of postoperative pain one year after surgery and no difference in the rate of reoperation for recurrence. In paper III we explore the possible association between inguinal hernia and anastomotic leakage after colorectal cancer surgery. Patients registered in the Swedish Colorectal Cancer Register with an operation resulting in an anastomosis from 2007 up until 2018 were included. Data was linked to the Swedish Hernia Register to identify patients with previous inguinal hernia surgery. An acyclic graph was constructed to define possible confounding factors and their impact on the outcome. Multiple imputation was used to adjust for missing data. Results show no increased risk for anastomotic leakage for patients with previous inguinal hernia repair. In paper IV we analyse data from the 30 years of registration in the Swedish hernia register from 1992 to 2021. 362,502 groin hernia operations were identified. The results show an increase in the rate of day case surgery and a reduced risk of reoperation for recurrence. Significant changes can be detected in the choice of operative techniques. Both males and females have reduced risk of reoperation for recurrence, however females have a more pronounced improvements during the last 10 years compared to males. The laparo-endoscopic technique is associated with reduced risk of reoperation for recurrence for females. For males an open mesh repair is associated with a reduced risk of reoperation for recurrence. In conclusion, the Swedish hernia register has national coverage and good quality of data with long follow up time and is therefore a powerful tool when assessing outcomes and testing hypotheses. There is no evidence to support that self-gripping mesh can reduce chronic pain or that inguinal hernia is associated with an increased risk for anastomotic leakage after colorectal cancer surgery. When analysing the results of the last 30 years of hernia surgery in Sweden a significant reduction in reoperations for recurrence can be seen, with a more prominent improvement in females.