A Reappraisal of Adult Thoracic and Abdominal Surface Anatomy Via CT Scan in Chinese Population

Clinical Anatomy 29:165–174 (2016) ORIGINAL COMMUNICATION A Reappraisal of Adult Thoracic and Abdominal Surface Anatomy via CT Scan in Chinese Population XIN-HUA SHEN,1† BAI-YAN SU,2† JING-JUAN LIU,2 GU-MUYANG ZHANG,2 2 2 3 1 HUA-DAN XUE, ZHENG-YU JIN, S. ALI MIRJALILI, AND CHAO MA * 1Department of Anatomy, Histology and Embryology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing, China 2Department of Radiology, Peking Union Medical College Hospital, Beijing, China 3Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand Accurate surface anatomy is essential for safe clinical practice. There are numerous inconsistencies in clinically important surface markings among and within contemporary anatomical reference texts. The aim of this study was to investi- gate key thoracic and abdominal surface anatomy landmarks in living Chinese adults using computed tomography (CT). A total of 100 thoracic and 100 abdominal CT scans were examined. Our results indicated that the following key surface landmarks differed from current commonly–accepted descriptions: the positions of the tracheal bifurcation, azygos vein termination, and pulmonary trunk bifurcation (all below the plane of the sternal angle at vertebral level T5–T6 in most individuals); the superior vena cava formation and junction with the right atrium (most often behind the 1st and 4th intercostal spaces, respectively); and the level at which the inferior vena cava and esophagus traverse the diaphragm (T10 and T11, respectively). The renal arteries were most commonly at L1; the midpoint of the renal hila was most frequently at L2; the 11th rib was posterior to the left kidney in only 29% of scans; and the spleen was most frequently located between the 10th and 12th ribs. A number of significant sex- and age-related dif- ferences were noted. The Chinese population was also compared with western populations on the basis of published reports. Reappraisal of surface anatomy using modern imaging tools in vivo will provide both quantitative and qualitative evidence to facilitate the clinical application of these key surface landmarks. Clin. Anat. 29:165–174, 2016. VC 2015 Wiley Periodicals, Inc. Key words: sternal angle; central veins; lung; diaphragm; kidney; spleen; surface anatomy Abbreviations used: AA, abdominal aorta; BCV, brachioce- Chinese Academy of Medical Sciences, School of Basic Medicine phalic vein; CC, costal cartilages; CT, computed tomography; Peking Union Medical College, Beijing 100005, China. ICS, intercostal space; IMA, inferior mesenteric artery; IVC, E-mail: [email protected] inferior vena cava; RA, right atrial; SMA, superior mesenteric †Xin-Hua Shen and Bai-Yan Su have contributed equally to this artery work. Contract grant sponsor: Peking Union Medical College Youth Research Fund #2015JCS001 (XS). Received 6 March 2015; Accepted 6 April 2015 *Correspondence to: Chao Ma, Ph.D., Department of Anatomy, Published online 29 May 2015 in Wiley Online Library Histology and Embryology, Institute of Basic Medical Sciences (wileyonlinelibrary.com). DOI: 10.1002/ca.22556 VC 2015 Wiley Periodicals, Inc. 166 Shen et al. INTRODUCTION sected the upper or lower half of a vertebra or the intervertebral disc (Mirjalili et al., 2012a, 2012b, Surface anatomy is essential for understanding 2012c, 2012d). basic topographical anatomy, examining patients, Thoracic CT scans from a total of 100 subjects interpreting diagnostic images, and performing sur- (52 females and 48 males) were analyzed. The mean gery or interventional procedures (Sayeed and Dar- age of the subjects was 53.5 6 12.8 years (range 23– ling, 2007; Elliott et al., 2010; Smith and Darling, 80). The surface anatomical characteristics of the 2011). However, traditional knowledge of human sur- sternal angle plane (SA plane) and related structures, face anatomy is largely derived from cadaver studies, central veins, cardiac apex, lungs, diaphragm, and entailing potential distortion from aging, disease, xiphisternal joint were analyzed as described below: comorbidity, postmortem changes, and embalming (Cunningham, 1893; Anson and McVay, 1936). Most traditional anatomical studies were performed before Sternal Angle the introduction of modern cross-sectional imaging, A horizontal line drawn through the manubrioster- but their descriptions have been reiterated in multiple nal joint was the SA plane (Fig. 1A). The exact verte- editions of anatomical and clinical texts with little con- bral level was determined by counting down from the sideration of their accuracy and therefore their utility. first thoracic vertebra identified by its articulation with There are numerous inconsistencies in clinically the first rib. Both vertebral level and vertical distance important surface markings among and within con- from the SA plane were recorded for four structures: temporary anatomical texts (Hale et al., 2010). There- the bifurcation of the trachea defined by the carina fore, it is essential for surface anatomy to be accurate (Fig. 1B); the aortic arch defined by the apex of its and evidence-based. Modern cross-sectional imaging concavity (Fig. 1C); the level of the azygos vein/supe- techniques such as computed tomography (CT) offer rior vena cava (azygos/SVC) junction defined by the the opportunity to reassess the accuracy of surface center of the azygos vein at this junction (Fig. 1D); anatomy in relatively large numbers of living individu- and the pulmonary trunk bifurcation represented by a als. Recently, a series of studies using analyses of point midway between the midpoints of the left and adult CT scan images have promoted quantitative and right pulmonary arteries at their origin (Fig. 1E) (Mir- qualitative re-examination of surface anatomy land- jalili et al., 2012a). marks (Mirjalili et al., 2012a,b,c,d). However, there has been no such study on the Chinese (Han nationality) population. In this study, we investigated key tho- Central Veins racic and abdominal surface anatomy landmarks in living Chinese adults using CT imaging. The results for The origin of the brachiocephalic vein (BCV) was different age and sex groups were compared with identified as the junction of the subclavian and inter- each other and with commonly accepted descriptions nal jugular veins on coronal scans and its position rel- of surface anatomy, and also with similar studies in ative to a square encompassing the limits of the western populations. ipsilateral sternoclavicular joint (behind but within the square, lateral, medial, superior, or inferior) was recorded. The formation of the SVC was defined by the union of the BCVs in the coronal plane. The SVC/ MATERIALS AND METHODS right atrial (SVC/RA) junction was defined as the site where the SVC and right auricle merged in the sagittal All subjects were adult Chinese (Han nationality). and axial planes. The cranio-caudal level of SVC sur- Age and gender were recorded but body mass index face anatomy was referenced to the costal cartilages was not available. (CC) and anterior intercostal space (ICS) (Mirjalili Adult CT scans were acquired in the hospital using et al., 2012a). a dual-source dual-energy scanner (Siemens SOMA- TOM Definition Flash, Erlangen, Germany) with slice thickness 1.5 mm. All scans were taken in the supine Cardiac Apex position at end-tidal inspiration with both upper limbs abducted. Scans from patients with the following con- The cardiac apex was defined as the most lateral ditions were excluded from further analysis: kyphosis point of the left border of the heart and was recorded (Fon et al., 1980), scoliosis (Cobb, 1948), abnormal with reference to the CC, anterior ICS, and anterior lordosis (Vialle et al., 2005), a distorting mass or fluid ends of the ribs, together with the distance from the collection, and obvious visceromegaly. All scans cardiac apex to the midline. were enhanced with iodinated intravenous contrast and were analyzed by dual consensus reporting Lungs (Murphy et al., 2010) following multiplanar recon- struction on a Siemens Syngo.via (version VA11B_ The anterior and posterior lower borders of the HF03) workstation. lung midway between the midline and the lateral tho- The vertebral levels of major planes, vessels and racic wall (at the corresponding level of the domes of viscera in the thorax and abdomen were determined the diaphragm) were assessed in relation to the CC on sagittal scans; each was recorded as the level at and ICS. The vertebral level of the inferior border of which a horizontal line intersected the anterior border the lung immediately adjacent to the vertebral column of the vertebral column, according to whether it inter- was recorded. The inferior border of the lung in the Thoracic and Abdominal Surface Anatomy 167 Fig. 1.(A) The vertebral level of the SA plane (lower T4) on a sagittal CT scan. (B– E) The carina (B), aortic arch (C), azygos/SVC junction (D), and pulmonary trunk bifurcation (E) were first identified by scrolling scans and their vertical position relative to the SA plane was then determined from sagittal projections. midaxillary line was not assessed because there is no the umbilicus. For the celiac trunk, superior mesen- precise radiological definition of this line. teric artery (SMA), left and right renal arteries, and inferior mesenteric artery (IMA), the vertebral level of the midpoint of the origin of the artery from the Diaphragm abdominal aorta (AA) was determined from sagittal The domes of the diaphragm were identified in and axial scans (Fig. 2A). For the AA bifurcation and axial scans and their cranio-caudal level was recorded the IVC formation, the apex of the angle between the in relation to the CC, anterior ICS, and anterior ends common iliac arteries and veins, respectively, was of the ribs. The vertebral levels at which the inferior selected and both vertebral level and distance from vena cava (IVC), esophagus, and aorta passed the midline were determined (Fig. 2B). The distance through or behind the diaphragm were identified from from the AA bifurcation to the supracristal plane and sagittal scans (Mirjalili et al., 2012a).

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