Age prevalence, prior abdominal operations in internal abdominal hernias Senthil Nachimuthu, Department of Surgery, Hinchingbrooke Hospital, Huntingdon, Cambridgeshire, UK 14 July 2008 Dear Sir / Madam, I read with great interest about the article "Incarcerated transmesosigmoid hernia presenting in a 60-year-old man: a case report" by Danielle Collins and co-workers. I really appreciate the authors enthusiasm in presenting a case of internal abdominal hernia (IH) which, although rare, is increasing in incidence. At the same time I like to draw attention on two aspects of the conclusional remarks. First of all, it was mentioned in the conclusion that congenital internal hernias are more common in the paediatric population(1). It was originally thought that IH were more common in the paediatric age group but subsequent studies show that adult and elderly seem to have greater prevalence than the children(2) and the mean age was reported between 38 and 45 years(3). The authors have quite rightly ackowledged that recently the incidence of transmesenteric hernias is increasing. These hernias have a bimodal distribution, occurring in both paediatric and adult patients. In fact they are the most common type of IH in children, occurring in 35% of this patient population(4)(5)(6). However, there is a second peak of occurrence in the adult population, and in this subset of patients, the cause is iatrogenic, usually related to prior abdominal surgery, especially with Roux-en-Y anastomosis, trauma, or inflammation.(7)(8)(9) Second, it was also mentioned in the conclusion that in cases of small bowel obstruction without previous abdominal surgery, a congenital internal hernia should be considered. I completely agree with the above mentioned fact but one has to consider IH as a cause for small bowel obstruction even in patients with previous abdominal operations as the incidence of IH is rising with the frequent performance of liver transplantation and gastric bypass surgery for bariatric treatment(3)(7)as well as any gastrointestinal surgery involving creation of Roux loop. Finally I once again congratulate the authors interests in reporting this special clinical entity of IH. (1)Janin Y, Stone AM, Wise L: Mesenteric hernia. Surg Gynecol Obstet 1980, 150:747-754.(2)Blachar A, Federle MP: Internal hernia: an increasingly common cause of small bowel obstruction. Semin Ultrasound CT MR 2002, 23:174-183. (3)Blachar A, Federle MP, Pealer KM, Ikramuddin S, Schauer PR. Gastrointestinal complications of laparoscopic Roux-en-Y gastric bypass surgery: clinical and imaging findings.Radiology 2002; 223:25-632 (4)Ghahremani GG: Abdominal and pelvic hernias. In Textbook of Gastrointestinal Radiology. 2nd edition. Edited by: Gore RM, Levine MS. Philadelphia, PA: Saunders; 2000:1993-2009. (5)Mathieu D, Luciani A. Internal abdominal herniations. AJR 2004; 83:397–404(6)Renvall S, Niinikoski J. Internal hernia after gastric operations. Eur J Surg 1999; 157:575–577(7)Blachar A, Federle MP. Bowel obstruction following liver transplantation: clinical and CT findings in 48 cases with emphasis on internal hernia. Radiology 2001; 218:384-388(8)Blachar A, Federle MP, Dodson SF: Internal hernia: clinical and imaging findings in 17 patients with emphasis on CT criteria. Radiology 2001, 218:68-74.(9)Blachar A, Federle MP, Brancatelli G, Peterson MS, Oliver JH 3rd, Li W. Radiologist performance in the diagnosis of internal hernia by using specific CT findings with emphasis on Transmesenteric hernia. Radiology 2001; 221:422–428. Competing interests None.