Can the Third Part of Duodenum Behind SMA Be Detected With Confidence on CT as a Proposed Mechanism for Imaging Suspected Malrotation in Children? A Preliminary Proof of Concept Study

Abstract

AimThe aims of this study were to determine frequency and reliability of computed tomography (CT) detection of anatomic landmarks for imaging suspected midgut malrotation in infants and children, and to calculate an estimated effective dose of an upper abdominal CT scan in our patient population.Materials and MethodsFifty consecutive pediatric patients who underwent a CT scan that included their upper abdomen between August 2016 and February 2018 were included. Four pediatric radiology consultants independently reviewed CT scans for detection of the third part of the duodenum and defined their confidence level of this through identification of continuity with the pyloric antrum, D1, D2, and D4 components of the duodenum, as well as the duodenojejunal flexure.Interobserver variability was assessed using Fleiss κ for agreement. A dose estimate, per scan, was calculated using the scanner dose-length product and published conversion factors by Deak.ResultsThirty patients were boys. The average age was 7.5 ± 5.4 years (6 days to 16 years). The D3 segment was definitely identified in 70% of scans, with 68% to 73%, moderate agreement between the readers and a Fleiss κ of 0.47 to 0.52. The DJ flexure was definitely identified in only 30.5% cases, with 35%, poor agreement between readers (Fleiss κ of 0.03). The average estimated dose for a targeted CT scan of the abdomen was 0.9 mSv (0.04–2.4 mSv).ConclusionsThe third part of the duodenum, which is integral in excluding malrotation on cross-sectional studies, was “definitely” identified in 70% of CT scans of children in our study, with 68% to 73% agreement between the readers and a Fleiss κ of 0.47 to 0.52.These preliminary proof of concept results demonstrating a combination of a comparable CT dose in relation to upper gastrointestinal contrast studies and an acceptable number of cases delineating the third part of the duodenum with moderate agreement are a first step in suggesting low-dose CT for an imaging diagnosis of malrotation. Malrotation can be excluded in cases where D3 is well demonstrated in the normal position, which negates the need to automatically refer children with bilious emesis to specialist centers for upper gastrointestinal contrast studies.

Quality and Diagnosis on the Lateral View of Pediatric Upper Gastro-Intestinal Series

“…Other imaging techniques for diagnosing malrotation and midgut volvulus include ultrasound, CT and MRI [18][19][20][21], where demonstration of a retroperitoneal duodenum passing the deep [posterior] to the superior mesenteric artery and vein is considered the normal anatomic arrangement. These diagnostic imaging modalities have not gained widespread acceptance.…”

“…Ultrasound is an obvious choice because of its low cost and lack of ionizing radiation, making it attractive for use in children, as well as its portability, allowing it to be used in the emergency room, in clinics and at the bedside. However, identifying the duodenum passing deep to the superior mesenteric artery (SMA)/superior mesenteric vein (SMV) on ultrasound is challenging or even impossible in some patients due to obscuring bowel gas in the stomach or other portions of the bowel [18]. MRI which also does not use ionizing radiation, may require anesthesia for children under six years of age, which increases the risk, causes delays and is often inaccessible during after-hours when these emergencies present.…”

“…MRI which also does not use ionizing radiation, may require anesthesia for children under six years of age, which increases the risk, causes delays and is often inaccessible during after-hours when these emergencies present. Using CT to identify the duodenal anatomy has been tested and can be achieved with high reliability, but even though CT scanners are widely available and radiologists of all levels have good expertise with CT, there is a reluctance to apply CT scans in children, due to the perceived risks of radiation [18]. The UGIS therefore remains the mainstay for diagnosing or excluding malrotation and midgut volvulus in children, and any mechanisms for improving the diagnostic yield, such as the use of the lateral view, should be entertained seriously.…”