© Turkish Society of Radiology 2009 T he diaphragm, which forms an anatomical wall between the thoracic and abdominal cavities, develops in the first to fourth months of gestation, along with the body wall muscles, septum transversum, pleuroperitoneal membranes, and mediastinal dorsal me- sentery of the esophagus (1, 2). Congenital disorders of the diaphragm result in fusion defects of the diaphragm or maldevelopment of the gut accompanied by closure of the diaphragm. Congenital diaphragmatic hernias are categorized as Bochdalek (posterolateral), Morgagni (anterior-retrosternal), and hi- atal hernias and septum transversum defect. Worldwide, congenital diaphragmatic hernias occur in one out of every 2,000–12,500 live births (3). First described in 1867 by Victor Alexander Bochdalek (4), Bochdalek hernia is the most common type of diaphragmatic hernia, accounting for 95% of cases. Most cases are symptomatic at birth, and are diagnosed in the neonatal period. In adults, most Bochdalek hernias are asymptomatic, and therefore their detection is usually incidental. The real prevalence in the popula- tion is unknown, with an estimated range between 0.17% and 12.7% (5–8). The widespread use of multi-detector row computed tomography (MDCT) for the evaluation of thoracic and abdominal disease, with its inherent rapid scan acquisition and thin collimation technique, has re- sulted in a significant increase in the incidental discovery of occult le- sions. Thus, the aim of this study was to determine the prevalence of asymptomatic incidental Bochdalek hernias detected by MDCT, and to investigate a possible relationship between Bochdalek hernia and body habitus. Materials and methods Study population Our institutional board on medical ethics approved this research study. Informed consent was not required for this retrospective analysis. Patient confidentiality was protected. We reviewed computer records of all patients who underwent MDCT of the chest and/or abdomen at our institution between February 1, 2007 and November 30, 2007. After excluding any patients with blunt or penetrating body trauma, and ab- dominal, thoracic, or diaphragm operations, 1,350 consecutive patients over the age of 18 years were included in the study. MDCT examinations were performed for various indications, including follow-up of known abdominal and chest and/or abdomen disorders, primary or metastatic tumor investigations, vascular pathology, and evaluation of infectious diseases. No MDCT scan had been obtained specifically to evaluate dia- phragmatic disease. ABDOMINAL IMAGING ORIGINAL ARTICLE Diagn Interv Radiol DOI 10.4261/1305-3825.DIR.2750-09.1 Prevalence and MDCT characteristics of asymptomatic Bochdalek hernia in adult population Osman Temizöz, Hakan Gençhellaç, Ensar Yekeler, Hasan Ümit, Ercüment Ünlü, Hüseyin Özdemir, M. Kemal Demir From the Departments of Radiology (O.T.  osmantemizoz@ gmail.com, H.G., E.Ü., H.Ö., M.K.D.), and Gastroenterology (H.Ü.), Trakya University Faculty of Medicine, Edirne, Turkey; and the Department of Radiology (E.Y.), İstanbul University Faculty of Medicine, İstanbul, Turkey. Received 26 March 2009; revision requested 6 May 2009; revision received 13 May 2009; accepted 20 May 2009. Published online 28 December 2009 DOI 10.4261/1305-3825.DIR.2750-09.1 PURPOSE To determine the frequency of asymptomatic incidental Bo- chdalek hernias in adults, using multidetector computed to- mography (MDCT), and to ascertain any possible relationship between Bochdalek hernia and age, gender, or body mass index (BMI). MATERIALS AND METHODS Seven hundred and forty-eight abdominal, and 602 chest MDCT scans, which had been performed for a variety of rea- sons on 1350 adults, were investigated retrospectively. Loca- tion and size of Bochdalek hernias seen on these scans were correlated with age, gender, and BMI. On the basis of BMI, patients with Bochdalek hernia were classified as group A (BMI <25) and group B (BMI ≥25). RESULTS A total of 171 Bochdalek hernias were identified in 142 of 1350 patients, ranging in age from 25 to 90 years (median age, 57.2), representing a prevalence of 10.5%. Sixty left- sided unilateral Bochdalek hernias (42.2%), 53 (37.4%) right- sided unilateral Bochdalek hernias, and 29 (20.4%) bilateral Bochdalek hernias were detected. Forty-five (31.6%) were categorized as small, 82 (57.8%) were medium-sized, and 15 (10.5%) were large. BMI was <25 in 62 patients (43.7%), and ≥25 in 80 patients (56.3%). Fourteen patients (9.9%) were young adults, while 86 (60.6%) were middle aged, and 42 (29.6%) were elderly. No statistically significant relationship was found between dimensions or hernia locations and age, gender, or BMI of patients with Bochdalek hernia. CONCLUSION In view of the high prevalence of Bochdalek hernia in our study (10.5%), the multiplanar and reconstruction features of MDCT seem to facilitate the diagnosis of asymptomatic inci- dental Bochdalek hernia. No relationship was found between asymptomatic incidental Bochdalek hernia and age, gender, or BMI in adults. Key words:  diaphragmatic hernia  prevalence  computed tomography