Skip to main content
SpringerLink
Log in

Surgical Management of Crohn’s Disease

  • Chapter
Pediatric Inflammatory Bowel Disease

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Log in via an institution
Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 179.00
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Rabbett H, Elbadri A, Thwaites R, et al. Quality of life in children with Crohn’s disease. J Pediatr Gastroenterol Nutr. 1996 Dec;23(5):528–33.

    Article  CAS  Google Scholar 

  2. Hancock L, Windsor AC, Mortensen NJ. Inflammatory bowel disease: the view of the surgeon. Colorectal Dis. 2006 May;8 Suppl 1:10–4.

    Article  CAS  Google Scholar 

  3. Schraut WH. The surgical management of Crohn’s disease. Gastroenterol Clin North Am. 2002 Mar;31(1):255–63.

    Article  CAS  Google Scholar 

  4. Poggioli G, Pierangeli F, Laureti S, Ugolini F. Review article: indication and type of surgery in Crohn’s disease. Aliment Pharmacol Ther. 2002 Jul;16 Suppl 4:59–64.

    Article  CAS  Google Scholar 

  5. Leowardi C, Heuschen G, Kienle P, et al. Surgical treatment of severe inflammatory bowel diseases. Dig Dis. 2003;21(1):54–62.

    Article  PubMed  Google Scholar 

  6. Aufses AH, Jr. The history of Crohn’s disease. Surg Clin North Am. 2001 Feb;81(1):1–11, vii.

    Google Scholar 

  7. Garlock JH, Crohn’s BB. Appraisal of results of surgery in the treatment of regional enteritis. J Am Med Assoc. 1945;127:205–8.

    Google Scholar 

  8. Greenstein AJ Sachar D, Pucillo A, et al. Cancer in Crohn’s disease after divisionary surgery. A report of seven carcinomas occurring in excluded bowel. Am J Surg. 1978;135:86–90.

    Article  Google Scholar 

  9. Dziki A, Galbfach P. Crohn’s disease–when to operate? Acta Chir Iugosl. 2004;51(2):61–8.

    Article  PubMed  CAS  Google Scholar 

  10. McLeod RS. Surgery for inflammatory bowel diseases. Dig Dis. 2003;21(2):168–79.

    Article  PubMed  Google Scholar 

  11. Veroux M, Angriman I, Ruffolo C, et al. Severe gastrointestinal bleeding in Crohn’s disease. Ann Ital Chir. 2003 Mar–Apr;74(2):213–5; discussion 6.

    CAS  Google Scholar 

  12. Andersson P, Olaison G, Bodemar G, et al. Surgery for Crohn’s colitis over a twenty-eight-year period: fewer stomas and the replacement of total colectomy by segmental resection. Scand J Gastroenterol. 2002 Jan;37(1):68–73.

    Article  CAS  Google Scholar 

  13. Hurst RD, Molinari M, Chung TP, et al. Prospective study of the features, indications, and surgical treatment in 513 consecutive patients affected by Crohn’s disease. Surgery. 1997 Oct;122(4):661–7;discussion 7–8.

    Article  CAS  Google Scholar 

  14. Alvarez-Lobos M, Arostegui JI, Sans M, et al. Crohn’s disease patients carrying Nod2/CARD15 gene variants have an increased and early need for first surgery due to stricturing disease and higher rate of surgical recurrence. Ann Surg. 2005 Nov;242(5):693–700.

    Article  Google Scholar 

  15. Rufo PA, Bousvaros A. Current Therapy of Inflammatory Bowel Disease in Children. Paediatr Drugs. 2006;8(5):279–302.

    Article  PubMed  Google Scholar 

  16. Patel HI, Leichtner AM, Colodny AH, Shamberger RC. Surgery for Crohn’s disease in infants and children. J Pediatr Surg. 1997 Jul;32(7):1063–7; discussion 7–8.

    Article  CAS  Google Scholar 

  17. Dokucu AI, Sarnacki S, Michel JL, et al. Indications and results of surgery in patients with Crohn’s disease with onset under 10 years of age: a series of 18 patients. Eur J Pediatr Surg. 2002 Jun;12(3):180–5.

    Article  CAS  Google Scholar 

  18. Konno M, Kobayashi A, Tomomasa T, et al. Guidelines for the treatment of Crohn’s disease in children. Pediatr Int. 2006 Jun;48(3):349–52.

    Article  CAS  Google Scholar 

  19. Nissan A, Zamir O, Spira RM, et al. A more liberal approach to the surgical treatment of Crohn’s disease. Am J Surg. 1997 Sep;174(3):339–41.

    Article  CAS  Google Scholar 

  20. Berg DF, Bahadursingh AM, Kaminski DL, Longo WE. Acute surgical emergencies in inflammatory bowel disease. Am J Surg. 2002 Jul;184(1):45–51.

    Article  Google Scholar 

  21. Ecker KW, Gierend M, Kreissler-Haag D, Feifel G. Reoperations at the ileostomy in Crohn’s disease reflect inflammatory activity rather than surgical stoma complications alone. Int J Colorectal Dis. 2001 Apr;16(2):76–80.

    Article  CAS  Google Scholar 

  22. Froehlich F, Juillerat P, Mottet C, et al. Obstructive fibrostenotic Crohn’s disease. Digestion. 2005;71(1):29–30.

    Article  PubMed  Google Scholar 

  23. Karaoglu AO, Yukselen V. Obstructing Crohn’s disease of the duodenum: is surgery always mandatory? Int J Clin Pract. 2004 Feb;58(2):221–3.

    Article  CAS  Google Scholar 

  24. Heimann TM, Greenstein AJ, Lewis B, et al. Comparison of primary and reoperative surgery in patients with Crohn’s disease. Ann Surg. 1998 Apr;227(4):492–5.

    Article  CAS  Google Scholar 

  25. Solem CA, Loftus EV, Jr., Tremaine WJ, et al. Fistulas to the urinary system in Crohn’s disease: clinical features and outcomes. Am J Gastroenterol. 2002 Sep;97(9):2300–5.

    Article  Google Scholar 

  26. Present DH. Urinary tract fistulas in Crohn’s disease: surgery versus medical therapy. Am J Gastroenterol. 2002 Sep;97(9):2165–7.

    Article  Google Scholar 

  27. Gruner JS, Sehon JK, Johnson LW. Diagnosis and management of enterovesical fistulas in patients with Crohn’s disease. Am Surg. 2002 Aug;68(8):714–9.

    Google Scholar 

  28. Ben-Ami H, Ginesin Y, Behar DM, et al. Diagnosis and treatment of urinary tract complications in Crohn’s disease: an experience over 15 years. Can J Gastroenterol. 2002 Apr;16(4):225–9.

    Google Scholar 

  29. Akobeng AK, Suresh-Babu MV, Firth D, et al. Quality of life in children with Crohn’s disease: a pilot study. J Pediatr Gastroenterol Nutr. 1999 Apr;28(4):S37–9.

    Article  CAS  Google Scholar 

  30. Glehen O, Lifante JC, Vignal J, et al. Small bowel length in Crohn’s disease. Int J Colorectal Dis. 2003 Sep;18(5):423–7.

    Article  CAS  Google Scholar 

  31. Yamamoto T, Bain IM, Mylonakis E, et al. Stapled functional end-to-end anastomosis versus sutured end-to-end anastomosis after ileocolonic resection in Crohn’s disease. Scand J Gastroenterol. 1999 Jul;34(7):708–13.

    Article  CAS  Google Scholar 

  32. Ikeuchi H, Kusunoki M, Yamamura T. Long-term results of stapled and hand-sewn anastomoses in patients with Crohn’s disease. Dig Surg. 2000;17(5):493–6.

    Article  PubMed  CAS  Google Scholar 

  33. Tersigni R, Alessandroni L, Barreca M, et al. Does stapled functional end-to-end anastomosis affect recurrence of Crohn’s disease after ileocolonic resection? Hepatogastroenterology. 2003 Sep–Oct;50(53):1422–5.

    Google Scholar 

  34. Yamamoto T. Factors affecting recurrence after surgery for Crohn’s disease. World J Gastroenterol. 2005 Jul 14;11(26):3971–9.

    Google Scholar 

  35. Resegotti A, Astegiano M, Farina EC, et al. Side-to-side stapled anastomosis strongly reduces anastomotic leak rates in Crohn’s disease surgery. Dis Colon Rectum. 2005 Mar;48(3):464–8.

    Article  Google Scholar 

  36. Larson DW, Pemberton JH. Current concepts and controversies in surgery for IBD. Gastroenterology. 2004 May;126(6):1611–9.

    Google Scholar 

  37. Munoz-Juarez M, Yamamoto T, Wolff BG, Keighley MR. Wide-lumen stapled anastomosis vs. conventional end-to-end anastomosis in the treatment of Crohn’s disease. Dis Colon Rectum. 2001 Jan;44(1):20–5;discussion 5–6.

    Article  CAS  Google Scholar 

  38. Yamamoto T, Allan RN, Keighley MR. Strategy for surgical management of ileocolonic anastomotic recurrence in Crohn’s disease. World J Surg. 1999 Oct;23(10):1055–60; discussion 60–1.

    Article  CAS  Google Scholar 

  39. Scarpa M, Angriman I, Barollo M, et al. Role of stapled and hand-sewn anastomoses in recurrence of Crohn’s disease. Hepatogastroenterology. 2004 Jul–Aug;51(58):1053–7.

    Google Scholar 

  40. Smedh K, Andersson M, Johansson H, Hagberg T. Preoperative management is more important than choice of sutured or stapled anastomosis in Crohn’s disease. Eur J Surg. 2002;168(3):154–7.

    Article  PubMed  Google Scholar 

  41. Yamamoto T, Keighley MR. Stapled functional end-to-end anastomosis in Crohn’s disease. Surg Today. 1999;29(7):679–81.

    Article  PubMed  CAS  Google Scholar 

  42. Galandiuk S. Stapled and hand-sewn anastomoses in Crohn’s disease. Dig Surg. 1998;15(6):655.

    Article  PubMed  CAS  Google Scholar 

  43. Hashemi M, Novell JR, Lewis AA. Side-to-side stapled anastomosis may delay recurrence in Crohn’s disease. Dis Colon Rectum. 1998 Oct;41(10):1293–6.

    Article  CAS  Google Scholar 

  44. Colombel JF, Loftus EV, Jr., Tremaine WJ, et al. Early postoperative complications are not increased in patients with Crohn’s disease treated perioperatively with infliximab or immunosuppressive therapy. Am J Gastroenterol. 2004 May;99(5):878–83.

    Article  CAS  Google Scholar 

  45. Dietz DW, Fazio VW, Laureti S, et al. Strictureplasty in diffuse Crohn’s jejunoileitis: safe and durable. Dis Colon Rectum. 2002 Jun;45(6):764–70.

    Article  Google Scholar 

  46. Laurent S, Detry O, Detroz B, et al. Strictureplasty in Crohn’s disease: short- and long-term follow-up. Acta Chir Belg. 2002 Aug;102(4):253–5.

    CAS  Google Scholar 

  47. Hurst RD, Michelassi F. Strictureplasty for Crohn’s disease: techniques and long-term results. World J Surg. 1998 Apr;22(4):359–63.

    Article  CAS  Google Scholar 

  48. Poggioli G, Laureti S, Pierangeli F, Ugolini F. A new model of strictureplasty for multiple and long stenoses in Crohn’s ileitis: side-to-side diseased to disease-free anastomosis. Dis Colon Rectum. 2003 Jan;46(1):127–30.

    Article  CAS  Google Scholar 

  49. Shatari T, Clark MA, Yamamoto T, et al. Long strictureplasty is as safe and effective as short strictureplasty in small-bowel Crohn’s disease. Colorectal Dis. 2004 Nov;6(6):438–41.

    Article  CAS  Google Scholar 

  50. Sampietro GM, Cristaldi M, Maconi G, et al. A prospective, longitudinal study of nonconventional strictureplasty in Crohn’s disease. J Am Coll Surg. 2004 Jul;199(1):8–20;discussion -2.

    Article  Google Scholar 

  51. Michelassi F, Upadhyay GA. Side-to-side isoperistaltic strictureplasty in the treatment of extensive Crohn’s disease. J Surg Res. 2004 Mar;117(1):71–8.

    Article  Google Scholar 

  52. Tonelli F, Fedi M, Paroli GM, Fazi M. Indications and results of side-to-side isoperistaltic strictureplasty in Crohn’s disease. Dis Colon Rectum. 2004 Apr;47(4):494–501.

    Article  Google Scholar 

  53. Eisenberger CF, Izbicki JR, Broering DC, et al. Strictureplasty with a pedunculated jejunal patch in Crohn’s disease of the duodenum. Am J Gastroenterol. 1998 Feb;93(2):267–9.

    Article  CAS  Google Scholar 

  54. Milsom JW, Hammerhofer KA, Bohm B, et al. Prospective, randomized trial comparing laparoscopic vs. conventional surgery for refractory ileocolic Crohn’s disease. Dis Colon Rectum. 2001 Jan;44(1):1–8; discussion -9.

    Article  CAS  Google Scholar 

  55. Dutta S, Rothenberg SS, Chang J, Bealer J. Total intracorporeal laparoscopic resection of Crohn’s disease. J Pediatr Surg. 2003 May;38(5):717–9.

    Article  CAS  Google Scholar 

  56. Tilney HS, Constantinides VA, Heriot AG, et al. Comparison of laparoscopic and open ileocecal resection for Crohn’s disease: a metaanalysis. Surg Endosc. 2006 Jul;20(7):1036–44.

    Article  CAS  Google Scholar 

  57. Bonnard A, Fouquet V, Berrebi D, et al. Crohn’s disease in children. Preliminary experience with a laparoscopic approach. Eur J Pediatr Surg. 2006 Apr;16(2):90–3.

    Article  CAS  Google Scholar 

  58. Maartense S, Dunker MS, Slors JF, et al. Laparoscopic-assisted versus open ileocolic resection for Crohn’s disease: a randomized trial. Ann Surg. 2006 Feb;243(2):143–9; discussion 50–3.

    Article  Google Scholar 

  59. Casillas S, Delaney CP. Laparoscopic surgery for inflammatory bowel disease. Dig Surg. 2005;22(3):135–42.

    Article  PubMed  Google Scholar 

  60. Hirayama I, Ide M, Shoji H, et al. Laparoscopic-assisted partial ileectomy for Crohn’s disease associated with chronic anemia due to frequent hemorrhage. Hepatogastroenterology. 2005 May–Jun;52(63):823–5.

    Google Scholar 

  61. Huilgol RL, Wright CM, Solomon MJ. Laparoscopic versus open ileocolic resection for Crohn’s disease. J Laparoendosc Adv Surg Tech A. 2004 Apr;14(2):61–5.

    Article  Google Scholar 

  62. von Allmen D, Markowitz JE, York A, et al. Laparoscopic-assisted bowel resection offers advantages over open surgery for treatment of segmental Crohn’s disease in children. J Pediatr Surg. 2003 Jun;38(6):963–5.

    Article  Google Scholar 

  63. Shore G, Gonzalez QH, Bondora A, Vickers SM. Laparoscopic vs conventional ileocolectomy for primary Crohn’s disease. Arch Surg. 2003 Jan;138(1):76–9.

    Article  Google Scholar 

  64. Wu JS, Birnbaum EH, Kodner IJ, et al. Laparoscopic-assisted ileocolic resections in patients with Crohn’s disease: are abscesses, phlegmons, or recurrent disease contraindications? Surgery. 1997 Oct;122(4):682–8;discussion 8–9.

    Article  CAS  Google Scholar 

  65. Milsom JW. Laparoscopic surgery in the treatment of Crohn’s disease. Surg Clin North Am. 2005 Feb;85(1):25–34;vii.

    Google Scholar 

  66. Seymour NE, Kavic SM. Laparoscopic management of complex Crohn’s disease. Jsls. 2003 Apr–Jun;7(2):117–21.

    Google Scholar 

  67. Benoist S, Panis Y, Beaufour A, et al. Laparoscopic ileocecal resection in Crohn’s disease: a case-matched comparison with open resection. Surg Endosc. 2003 May;17(5):814–8.

    Article  CAS  Google Scholar 

  68. Evans J, Poritz L, MacRae H. Influence of experience on laparoscopic ileocolic resection for Crohn’s disease. Dis Colon Rectum. 2002 Dec;45(12):1595–600.

    Article  Google Scholar 

  69. Watanabe M, Ohgami M, Teramoto T, et al. Laparoscopic ileocecal resection for Crohn’s disease associated with intestinal stenosis and ileorectal fistula. Surg Today. 1999;29(5):446–8.

    Article  PubMed  CAS  Google Scholar 

  70. Uchikoshi F, Ito T, Nezu R, et al. Advantages of laparoscope-assisted surgery for recurrent Crohn’s disease. Surg Endosc. 2004 Nov;18(11):1675–9.

    CAS  Google Scholar 

  71. Hasegawa H, Watanabe M, Nishibori H, et al. Laparoscopic surgery for recurrent Crohn’s disease. Br J Surg. 2003 Aug;90(8):970–3.

    Article  CAS  Google Scholar 

  72. Thaler K, Dinnewitzer A, Oberwalder M, et al. Assessment of long-term quality of life after laparoscopic and open surgery for Crohn’s disease. Colorectal Dis. 2005 Jul;7(4):375–81.

    Article  CAS  Google Scholar 

  73. Andersson P, Olaison G, Hallbook O, Sjodahl R. Segmental resection or subtotal colectomy in Crohn’s colitis? Dis Colon Rectum. 2002 Jan;45(1):47–53.

    Article  CAS  Google Scholar 

  74. Martel P, Betton PO, Gallot D, Malafosse M. Crohn’s colitis: experience with segmental resections;results in a series of 84 patients. J Am Coll Surg. 2002 Apr;194(4):448–53.

    Article  Google Scholar 

  75. Bernell O, Lapidus A, Hellers G. Recurrence after colectomy in Crohn’s colitis. Dis Colon Rectum. 2001 May;44(5):647–54;discussion 54.

    Article  CAS  Google Scholar 

  76. Fichera A, McCormack R, Rubin MA, et al. Long-term outcome of surgically treated Crohn’s colitis: a prospective study. Dis Colon Rectum. 2005 May;48(5):963–9.

    Article  Google Scholar 

  77. Rieger N, Collopy B, Fink R, et al. Total colectomy for Crohn’s disease. Aust N Z J Surg. 1999 Jan;69(1):28–30.

    Article  CAS  Google Scholar 

  78. Proctor ML, Langer JC, Gerstle JT, Kim PC. Is laparoscopic subtotal colectomy better than open subtotal colectomy in children? J Pediatr Surg. 2002 May;37(5):706–8.

    Article  CAS  Google Scholar 

  79. Sandborn WJ, Fazio VW, Feagan BG, Hanauer SB. AGA technical review on perianal Crohn’s disease. Gastroenterology. 2003 Nov;125(5):1508–30.

    Article  Google Scholar 

  80. Judge TA, Lichtenstein GR. Treatment of fistulizing Crohn’s disease. Gastroenterol Clin North Am. 2004 Jun;33(2):421–54, xi-xii.

    Google Scholar 

  81. Regueiro M, Mardini H. Treatment of perianal fistulizing Crohn’s disease with infliximab alone or as an adjunct to exam under anesthesia with seton placement. Inflamm Bowel Dis. 2003 Mar;9(2):98–103.

    Article  Google Scholar 

  82. Topstad DR, Panaccione R, Heine JA, et al. Combined seton placement, infliximab infusion, and maintenance immunosuppressives improve healing rate in fistulizing anorectal Crohn’s disease: a single center experience. Dis Colon Rectum. 2003 May;46(5):577–83.

    Article  Google Scholar 

  83. Poritz LS, Rowe WA, Koltun WA. Remicade does not abolish the need for surgery in fistulizing Crohn’s disease. Dis Colon Rectum. 2002 Jun;45(6):771–5.

    Article  Google Scholar 

  84. Galandiuk S, Kimberling J, Al-Mishlab TG, Stromberg AJ. Perianal Crohn’s disease: predictors of need for permanent diversion. Ann Surg. 2005 May;241(5):796–801; discussion -2.

    Article  Google Scholar 

  85. Rintala RJ, Lindahl HG. Proctocolectomy and J-pouch ileo-anal anastomosis in children. J Pediatr Surg. 2002 Jan;37(1):66–70.

    Article  CAS  Google Scholar 

  86. Su FW, Beckman DB, Yarnold PA, Grammer LC. Low incidence of complications in asthmatic patients treated with preoperative corticosteroids. Allergy Asthma Proc. 2004 Sep–Oct;25(5):327–33.

    Google Scholar 

  87. Marchal L, D’Haens G, Van Assche G, et al. The risk of post-operative complications associated with infliximab therapy for Crohn’s disease: a controlled cohort study. Aliment Pharmacol Ther. 2004 Apr 1;19(7):749–54.

    Article  CAS  Google Scholar 

  88. Rutgeerts P. Review article: recurrence of Crohn’s disease after surgery - the need for treatment of new lesions. Aliment Pharmacol Ther. 2006 Oct;24 Suppl 3:29–32.

    Article  Google Scholar 

  89. Sorrentino D, Terrosu G, Avellini C, et al. Prevention of postoperative recurrence of Crohn’s disease by infliximab. Eur J Gastroenterol Hepatol. 2006 Apr;18(4):457–9.

    Article  Google Scholar 

  90. Lemann M. Review article: can post-operative recurrence in Crohn’s disease be prevented? Aliment Pharmacol Ther. 2006 Oct;24 Suppl 3:22–8.

    Article  CAS  Google Scholar 

  91. Sandborn WJ, Feagan BG. The efficacy of azathioprine and 6-mercaptopurine for the prevention of postoperative recurrence in patients with Crohn’s disease remains uncertain. Gastroenterology. 2004 Sep;127(3):990–3.

    Article  CAS  Google Scholar 

  92. Rutgeerts P. Strategies in the prevention of post-operative recurrence in Crohn’s disease. Best Pract Res Clin Gastroenterol. 2003 Feb;17(1):63–73.

    Article  CAS  Google Scholar 

  93. Stephens M, Batres LA, Ng D, Baldassano R. Growth failure in the child with inflammatory bowel disease. Semin Gastrointest Dis. 2001 Oct;12(4):253–62.

    CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Division of Pediatric Surgery, The University of North Carolina Chapel Hill, CB# 7223, 3010 Old Clinic Building, Chapel Hill, NC 27599, USA

    Daniel von Allmen

Authors
  1. Daniel von Allmen
    View author publications

    You can also search for this author in PubMed Google Scholar

Editor information

Editors and Affiliations

  1. Attending Physician, Division of GI Hepatology and Nutrition, Director Endoscopy Suite, The Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA

    Petar Mamula M.D. (Assistant Professor of Pediatrics) (Assistant Professor of Pediatrics)

  2. Attending Physician, Children’s Center for Digestive Health, Greenville Hospital System University Medical Center, University of South Carolina School of Medicine, Greenville, South Carolina, USA

    Jonathan E. Markowitz M.D., M.S.C.E. (Associate Professor of Clinical Pediatrics) (Associate Professor of Clinical Pediatrics)

  3. Attending Physician and Director, Inflammatory Bowel Disease Center Division of GI, Hepatology and Nutrition. The Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA

    Robert N. Baldassano M.D. (Professor) (Professor)

Rights and permissions

Reprints and permissions

Copyright information

© 2008 Springer Science+Business Media, LLC

About this chapter

Cite this chapter

Allmen, D.v. (2008). Surgical Management of Crohn’s Disease. In: Mamula, P., Markowitz, J.E., Baldassano, R.N. (eds) Pediatric Inflammatory Bowel Disease. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-73481-1_35

Download citation

  • DOI: https://doi.org/10.1007/978-0-387-73481-1_35

  • Publisher Name: Springer, Boston, MA

  • Print ISBN: 978-0-387-73480-4

  • Online ISBN: 978-0-387-73481-1

  • eBook Packages: MedicineMedicine (R0)

Publish with us

Policies and ethics

Search

Navigation