1. Goligher J, Duthie H, Nixon H. Fisura anal. In: Cirugía del ano, colon y recto. 2 ed. Barcelona: Salvat; 1987. p. 143-158.

2. Lowney J, Fleshman J. Benign disorders of the anorectum (pelvic floor, fissures, hemorrhoids, and fistulas). In: Ashley S, Zinner M, editores. Maingot´s abdominal operations.11ed. United States of America: McGraw-Hill; 2007. p. 663-691.

3. McCallion K, Gardiner K. Progress in the understanding and treatment of chronic anal fissure. Postgrad Med J 2001; 77: 753-758.

4. Ortiz H, Marzo J, Armendáriz P, DeMiguel M, Blasi M. Fisura de ano. Alteraciones de la continencia y de la calidad de vida durante la enfermedad y a los 6 meses de la esfinterotomía lateral interna subcutánea. Cir. Esp 2005; 77(2): 91-95.

5. Eisenhammer, S.The surgical correction of chronic internal anal(sphincteric) contracture. S Afr Med J, 1951; 25: 486-489.

6. Giral A, Memisoğlu K, Gültekin Y, İmeryüz N, Kalayc C, Ulusoy N et al. Botulinum toxin injection versus lateral internal sphincterotomy in the treatment of chronic anal fissure: a non-randomized controlled trial. BMC Gastroenterol, 2004; 22: 4-7.

7. Garcia-Granero E, Muñoz-Forner E, Mínguez M, Ballester C, García-Botello S, Lledó S. Tratamientos de la fisura anal crónica. Cir. Esp, 2005; 78(3): 24-27.

8. Steele S, Madoff R. Systematic review: the treatment of anal fissure. Aliment Pharmacol Ther, 2006; 24: 247-257.

9. P, Gupta. Treatment of fissure in ano-revisted. African Health Sciences, 2004; 4(1): 58-62.

10. Gui D, Cassetta E, Anastasio G, Bentivoglio A, Giorgio M, Albanese A. Botulinum toxin for chronic anal fissure. Lancet, 1994; 344: 1127-1128.

11. Briceño H, Vitale M. Comparación del tratamiento de la fisura anal con toxina botulinica y esfinterotomia lateral interna abierta (tesis de especialización). Caracas: UCV, 2003.

12. Brisinda G, Albanese A, Cadeddu F, Bentivoglio A, Mabisombi A, Marniga G, et al. Botulinum neurotoxin to treat chronic anal fissure: results of a randomized „Botox vs. Dysport‟ controlled trial. Aliment Pharmacol Ther, 2004; 19: 695–701.

13. Tankova L, Yoncheva K , Muhtarov M, Kadyan H, Draganov V. Topical mononitrate treatment in patients with anal fissure. Aliment Pharmacol Ther , 2002; 16: 101-103.

14. Novell F, Novell-Costa F, Novell J. Topical glyceryl trinitrate in the treatment of anal fissure. Rev Esp Enferm Dig. 2004; 96(4): 255-258. 17

15. Gonzalez C, Orsini O. Fisura anal cronica: tratamiento con nitroglicerina tópica Vs esfinterotomia lateral interna (tesis de especialización). Caracas: UCV, 2004.

16. Brisinda G, Giorgio M, Bentivoglio A, Cassetta E, Gui D, Albanese A. A comparison of injections of botulinum toxin vs. topical nitroglycerin ointment for chronic anal fissure. N Engl J Med 1999; 341: 65-69.

17. Sardiñas C. Fisura anal. In: Proctología para cirujanos generales. Caracas: Disinlimed; 2002. p. 93-107.

18. Rakinic J. Anal Fissure. Clinics in colon and rectal surgery, 2007; 20 (2): 133-137.

19. Eisenhammer S.The evaluation of the internal anal esphincterotomy operation with special reference to anal fissure. Surg Gyn Obst, 1959; 109: 583-590.

20. Arabi Y, Alexander-Williams J, Keighley M. Anal pressures in hemorrhoids and anal fissure. Am J Surg, 1977: 134: 608-610.

21. Herzig D, Kim C. Anal fissure. Surg Clin N Am, 2010; 90: 33–44.

22. Bhardwaj R, Hoyle C, Vaizey C, Boulos P. Neuromyogenic properties of the internal anal sphincter: therapeutic rationale for anal fissures, Gut, 2000; 46: 861–868.

23. Sanchez A, Arroyo A, Pérez F, Serrano P, Candela F, Tomás A, et al. Open lateral internal anal sphincterotomy under local anesthesia as the gold standard in the treatment of chronic anal fissures. A prospective clinical and manometric study. Rev Esp Enferm Dig, 2004; 96(12): 856-863.

24. Arroyo A, Pérez-Vicente F, Serrano P, Candela F, Sánchez A, Pérez-Vázquez M, Calpena R. Tratamiento de la fisura anal crónica; revisión de conjunto. Cir Esp, 2005; 78(2): 68-74.

25. Siegel S, Castellan N. Estadística No Paramétrica Aplicada a la Conducta. México: Trillas; 1995. p. 437.

26. Daniel, W. Bioestadística. Base para el análisis de las Ciencias de la Salud. 4ed. México: Limusa-Wiley; 2002. p. 910.

27. Abcarian H, Lakshmanan S, Read D, Roccaforte P. The role of internalsphincter in chronic anal fissure. Dis Colon Rectum, 1982; 25:525-30.

28. Farouk R, Duthie G, MacGregor A, Bartolo D. Sustained internal anal sphincter hypertonia in patients with chronic anal fissure. Dis Colon Rectum, 1994; 37: 424-9.

29. Pascual M, Courtier R, Gil M, Puig S, Serrano A, Andreu M et al. Estudio ecográfico y manométrico del esfínter anal interno en individuos con fisura anal crónica. Cir Esp 2005; 77(1): 27-30. 18

30. Scholefield H, Bock J, Marla B, Richter H, Athanasiadis S, Pröls M, Herold A. A dose finding study with 0.1%, 0.2%, and 0.4% glyceryl trinitrate ointment in patients with chronic anal fissures. Gut, 2003; 52:264–269.

31. Carapeti E, Kamm M, McDonald P, Chadwick S, Melville D, Phillips R. Randomised controlled trial shows that glyceryl trinitrate heals anal fissures, higher doses are not more effective, and there is a high recurrence rate. Gut, 1999; 44:727–730.

32. Kenny S, Irvine T, Driver C, Nunn A, Losty P, Jones M, et al. Double blind randomised controlled trial of topical glyceryl trinitrate in anal fissure. Arch Dis Child, 2001; 85:404–407.

33. Ahmada J, Andrabi S, Rathore M. Comparison of topical glyceryl trinitrate with lignocaine ointment for treatment of anal fissure: A randomised controlled trial. Int J Surg, 2007; 5:4 2 9 – 4 3 2.

34. Radwan M, Ramdan K, Abu-Azab I, Abu-Zidan F. Botulinum toxin treatment for anal fissure. African Health Sciences, 2007: 7(1): 14-17.

35. Lysy J, Israelit-Yatzkan Y, Sestiery-Ittah M, Weksler-Zangen S, Keret D, Goldin E. Topical nitrates potentiate the effect of botulinum toxin in the treatment of patients with refractory anal fissure. Gut , 2001; 48:221–224.