title: Risk of symptomatic venous thromboembolism following emergency appendicectomy in adults.
abstract: BACKGROUND
  Appendicectomy is the commonest intra-abdominal emergency surgical procedure, and little is known regarding the magnitude and timing of the risk of venous thromboembolism (VTE) after surgery. This study aimed to determine absolute and relative rates of symptomatic VTE following emergency appendicectomy.
  
  
  METHODS
  A cohort study was undertaken using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data of patients who had undergone emergency appendicectomy from 2001 to 2011. Crude rates and adjusted incidence rate ratios (IRRs) for VTE were calculated using Poisson regression, compared with baseline risk in the year before appendicectomy.
  
  
  RESULTS
  A total of 13 441 patients were identified, of whom 56 (0·4 per cent) had a VTE in the first year after surgery. The absolute rate of VTE was highest during the in-hospital period, with a rate of 91·29 per 1000 person-years, which was greatest in those with a length of stay of 7 days or more (267·12 per 1000 person-years). This risk remained high after discharge, with a 19·1- and 6·6-fold increased risk of VTE in the first and second months respectively after discharge, compared with the year before appendicectomy (adjusted IRR: month 1, 19·09 (95 per cent c.i. 9·56 to 38·12); month 2, 6·56 (2·62 to 16·44)).
  
  
  CONCLUSIONS
  The risk of symptomatic VTE following appendicectomy is relatively high during the in-hospital admission and remains increased after discharge. Trials of extended thromboprophylaxis are warranted in patients at particularly high risk.
authors.affiliation: Division of Epidemiology and Public Health, School of Medicine, Queens Medical Centre Campus, University of Nottingham, Nottingham, UK.|Nottingham Digestive Diseases Biomedical Research Unit, Queens Medical Centre Campus, University of Nottingham, Nottingham, UK.|Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden.
authors.forename: D J
authors.initials: DJ
authors.lastname: Humes
authors.affiliation: Division of Epidemiology and Public Health, School of Medicine, Queens Medical Centre Campus, University of Nottingham, Nottingham, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Walker
authors.affiliation: Thrombosis and Haemophilia Centre, Guy's and St Thomas' NHS Foundation Trust, London, UK.
authors.forename: B J
authors.initials: BJ
authors.lastname: Hunt
authors.affiliation: Division of Epidemiology and Public Health, School of Medicine, Queens Medical Centre Campus, University of Nottingham, Nottingham, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: Sultan
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden.|Department of Paediatrics, Örebro University Hospital, Örebro, Sweden.
authors.forename: J F
authors.initials: JF
authors.lastname: Ludvigsson
authors.affiliation: Division of Epidemiology and Public Health, School of Medicine, Queens Medical Centre Campus, University of Nottingham, Nottingham, UK.
authors.forename: J
authors.initials: J
authors.lastname: West
mesh_terms: D000293:Adolescent; D000328:Adult; D001062:Appendectomy / Q000009:adverse effects*; D004630:Emergencies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology* / Q000209:etiology; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology; D054556:Venous Thromboembolism / Q000453:epidemiology* / Q000209:etiology; D055815:Young Adult