Comparison of ultrasonography with computed tomography in the diagnosis of incisional hernias

D. den Hartog 0 1 A. H. M. Dur 0 1 A. G. A. Kamphuis 0 1 W. E. Tuinebreijer 0 1 R. W. Kreis 0 1 0 A. G. A. Kamphuis Department of Radiology, Red Cross Hospital , Vondellaan 13, 1942 LE Beverwijk, The Netherlands 1 D. den Hartog (&) A. H. M. Dur W. E. Tuinebreijer R. W. Kreis Department of Surgery, Red Cross Hospital , Vondellaan 13, 1942 LE Beverwijk, The Netherlands Background The objective of this study is to determine the reliability and validity of ultrasonography (US) in diagnosing incisional hernias in comparison with computed tomography (CT). The CT scans were assessed by two radiologists in order to estimate the inter-observer variation and twice by one radiologist to estimate the intra-observer variation. Patients were evaluated after reconstruction for an abdominal aortic aneurysm or an aortoiliac occlusion. Methods Patients with a midline incision after undergoing reconstruction of an abdominal aortic aneurysm or aortoiliac occlusion were examined by CT scanning and US. Two radiologists evaluated the CT scans independently. One radiologist examined the CT scans twice. Discrepancies between the CT observations were resolved in a common evaluation session between the two radiologists. Results After a mean follow-up of 3.4 years, 40 patients were imaged after a reconstructed abdominal aortic aneurysm (80% of the patients) or aortoiliac occlusion. The prevalence of incisional hernias was 24/40 = 60.0% with CT scanning as the diagnostic modality and 17/40 = 42.5% with US. The measure of agreement between CT scanning and US expressed as a Kappa statistic was 0.66 (95% conWdence interval [CI] 0.45-0.88). The sensitivity of US examination when using CT as a comparison was 70.8%, the speciWcity was 100%, the predictive value of a positive US was 100%, and the predictive value of a negative US was 69.6%. The likelihood ratio of a positive US was inWnite and that of a negative US was 0.29. The inter- and intraobserver Kappa statistics were 0.74 (CI 0.54-0.95) and 0.80 (CI 0.62-0.99), respectively. Conclusions US imaging has a moderate sensitivity and negative predictive value, and a very good speciWcity and positive predictive value. Consistency of diagnosis, as determined by calculating the inter- and intra-observer Kappa statistics, was good. The incidence of incisional hernias is high after aortic reconstructions. - Incisional hernias, ventral hernias that manifest themselves through an operation scar, are a serious common complication of abdominal surgery. Incisional hernias occur in 1123% of laparotomies and can give rise to serious morbidity, such as strangulation and incarceration [1]. Often, the diagnosis can be made on clinical examination. However, small hernias and hernias in obese patients can be diYcult to diagnose. Diagnostic tools such as ultrasonography (US) and computed tomography (CT) are commonly used for imaging hernias. Most incisional hernias noted at cross-sectional imaging are incidental Wndings encountered during radiological examination for unrelated clinical problems. However, accurate demonstration of the size and location of the hernial oriWce may be useful in assessing the success of hernia repair. The accuracy of these methods and their place in the clinical management of hernias have not yet been fully determined. In cases in which there is clinical uncertainty of the diagnosis of an incisional hernia, US or CT scanning can be used. The validity and inter-observer reliability of CT in the diagnosis of incisional, inguinal, and femoral hernias have been described in a preliminary study of 24 patients [2]. In this study, the gold standard was the situation found at operation. For two observers, the sensitivity was 0.83 and 0.83, the speciWcity 0.83 and 0.67, the positive predictive value 0.94 and 0.88, and the negative predictive value 0.63 and 0.5, respectively. The inter-observer Kappa statistic was 0.87. Although the ultrasonographic features of ventral hernias have been described, the reliability and validity of US in the diagnosis of ventral hernias have not been systematically studied [35]. A literature search did not reveal the existence of any systematic comparisons of CT scanning and US for use in the diagnosis of incisional hernias. However, an observational study compared ultrasound with CT scanning without describing reliability and validity [6]. The objective of this study is to determine the reliability and validity of US in the diagnosis of incisional hernias. CT scanning was used as a comparison in the determination of the validity. A gold standard was lacking because these patients were not operated after the diagnosis of an incisional hernia. The study population was composed of a group of patients who had previously undergone open reconstruction for abdominal aortic aneurysm or aortoiliac occlusive disease. Patients with an abdominal aortic aneurysm have a high incidence of ventral hernias. For instance, in a study comparing US and magnetic resonanc (...truncated)