Configurations of the segmental and subsegmental bronchi and arteries in the right upper lobe of the human lung with special reference to their concomitant relations and double subsegmental arterial supply

Determining Tracheobronchial Tree with Anatomical Dissection: 204 Cases

OBJECTIVES

There are various anatomic variations in the tracheobronchial system. The frequency in studies with bronchoscopy was contradictory. This study aimed to investigate the tracheobronchial tree of the deceased patients with anatomical dissection.

MATERIAL AND METHODS

We made anatomical dissections on 204 cases in the Council of Forensic Medicine, Ministry of Justice. The deceased patients who were older than 12 years of age and of Turkish origin were included in this study consecutively.

RESULTS

Of the 204 cases, 161 (78.9%) were males and 43 (21.1%) were females. The mean age was 44.15±19.23 years. Anatomical variations were found to be present in 200 cases (98% of total). The highest degree of variation of the right upper lobe was noted to be 16.6% (34/204). An anomalous arrangement (with three segments or different placement) of the middle lobe was noted in 16.1% of cases. For the basal lower lobe, b8+(b9+b10) pattern and basal orifice with four segments were noted to be the most frequent anatomical variant in the right and left lungs, respectively. The most frequent tracheobronchial variations were as follows: apical basal lobe with two subsegments in the right and left (39.7%), left lower lobe basal orifice with four segments (34.8%), left upper lobe with three segments (25.5%), and right lower lobe basal orifice with three main segmental bronchi (21.1%).

CONCLUSION

The tracheobronchial tree exhibits highly individualistic features. The knowledge of the frequency of different variations obtained in different studies and normal anatomic variants in return makes doing therapeutic or diagnostic interventions easier and more accurate.

Left/right difference in the course and division of the pulmonary arterial branches in the lung upper lobe: A study using human embryos and early fetuses

Although left/right differences in a configuration of the pulmonary artery (PA) and its branches are well known, there is little information as to when and how such differences are established. Examination of serial sagittal sections of 25 embryos and fetuses at 6-7 weeks of gestation demonstrated that, at O'Rahilly stages 18-20, the right earliest first branch of PA originated in the anterior side of the upper lobar bronchus and overlay the upper bronchi, in contrast to the left branch which was located posteriorly and constricted medially by the upper posterior bronchus B1 + 2b. The right earliest branch was most likely to correspond to the future superior trunk, while the left branch might be a lingual artery. At stages 21-23, the upper posterior parenchyma was still underdeveloped in the left lung, since the ductus arteriosus and the left common cardinal vein seemed to make the left upper thoracic cavity narrow. Conversely, in the right lung, the thick S2 seemed to require a double arterial supply from both the superior and inferior arterial trunks. On the left, A3 originated at the lung apex and took a long descending course along the lung anterior surface. This high position of A3 might soon be corrected by an increased volume of S3. Overall, in contrast to the lower and middle lobes, early-developed branches of the PA did not accompany upper segmental and subsegmental bronchi. A mechanism "differential growth" seemed to explain how to correct the fetal morphology to provide the adult morphology with variations.

Three-dimensional analysis of the segmental arrangement of lower lung lobes in human fetuses: is this arrangement a miniature version of adult morphology?

Knowledge of the lung segment system is essential for understanding human anatomy and has great clinical relevance. The arrangement of 11 segments, including the S* or subsuperior segment, and its individual variations, are considered to be the same in fetal and adult lungs. The present study assessed the topographical anatomy of lower segmental and subsegmental bronchi by computer-assisted three-dimensional imaging of serial sagittal sections of both lungs of 22 embryos and fetuses of gestational age 6-7 weeks (crown-rump length 15.0-28.5 mm). Long inferior courses of B8b (basal) and B10c (medial) were observed in sagittal sections of both lungs. B8a (lateral) and B10b (lateral) in the right lungs were consistently underdeveloped, with S9 occupying most of the lateral half of the lower lobe. In some samples, B6b (lateral) did not reach the lateral surface. The lateral dominance of S9 was also seen in the left lungs. Some B* candidates were present, but B7 candidates were absent. Lateral and posterior expansions of S6b, S8a and S10b to cover S9 were observed in additional midterm and near-term lung sections, indicating that the original S9 dominance was 'corrected' by an increase in lung volume. Delayed growth of the lower lateral subsegments might induce mechanical stress, resulting in aberrant notches or fissures, such as those separating an independent posterior lobe. The segmental arrangement of fetal lungs was not stable, but was altered over a long fetal period after the complete subsegmental division of the bronchi, except for the minor bronchi B* and B7.

Fetal development of the minor lung segment

The mediobasal segment (S7) of the right lung has been considered to correspond to the cardiac lobe generally seen in mammals. To investigate fetal development of the right mediobasal segmental bronchus (B7), we examined paraffin-embedded serial sections of 15 embrynic and fetal lungs at 7-8 weeks (serial sections) as well as semiserial sections of 8 fetuses at 15-18 weeks (semiserial sections). All of the smaller specimens did not contain B7, but 2 of the 8 larger specimens carried B7: one was found in the immediately anterior side of the inferior pulmonary vein, while in the other, the subdivisions (B7a, B7b) were overriding the vein. Although the incidence might be underestimated because of observations using semiserial sections, the B7 was most likely to develop secondarily during a period from 8 to 15 weeks. Fetal topographical changes (mainly, the descent) of the middle lobe and the inferior pulmonary vein might relate with the secondarily budding of B7. The present result does not reduce a clinical relevance of B7 as a segmental bronchus of the lung segment system.

Evaluation of subsubsegmental pulmonary arteries of the posterior and anterior segments of the right upper lobe using multidetector row computed tomography with multiplanar reconstruction images

PURPOSE

We evaluated the patterns of subsubsegmental pulmonary arteries of the right upper lobe (posterior segment: S2; anterior segment: S3) with multiplanar reconstruction (MPR) images by multidetector row computed tomography (MDCT).

MATERIALS AND METHODS

A total of 64 patients who had undergone MDCT scans were included in the study. The subsubsegmental arteries were named by adding "i" or "ii" as the superior or the inferior branch, respectively, of the subsegmental arteries. The subsubsegmental arteries of S2 (A2ai, A2aii, A2bi, A2bii) and S3 (A3ai, A3aii, A3bi, A3bii) were evaluated as arising from either the recurrent artery (RA) or the ascending artery (AA).

RESULTS

A2ai originated from the RA and AA in 43 and 21 patients, respectively. The corresponding numbers were 32 each for A2aii; 28 and 36 for A2bi; 23 and 41 for A2bii; 60 and 4 for A3ai; 43 and 21 for A3aii; 59 and 5 for A3bi; and 54 and 10 for A3bii.

CONCLUSION

The branching pattern of the subsubsegmental pulmonary arteries in the right upper lobe (S2 and S3) could be visualized using MDCT with MPR images.

Human situs inversus of the thoracoabdominal structures

Situs inversus totalis is well known, but its comprehensive description has been rare, especially on the internal view of the heart. For discussions based on recent results in developmental biology, the present study demonstrates a region- or part-specific manner of the inverted morphology found in a male donated cadaver and discusses the pathogenetic mechanisms of situs inversus in the human. Therein, clearly inverted morphologies existed in the coronary vessels, the apex position (dextracardia), connections between the heart and great vessels, the internal view of the atrium, the aortic arch with the three major branches, lung and liver segments and abdominal gastrointestinal tract. However, the ventricular internal view suggested incomplete laterality, such as tricuspid atrioventricular valves for both ventricles. The cardiac conductive system appeared not to be inverted but abnormal. The thoracic aorta and pulmonary artery took an L-spiral position with modifications. The inferior vena cava was located on the right side of the abdominal aorta. However, the left-sided kidney was located superior to the right-sided kidney. Similarly, the testicular vessels did not exhibit a clearly inverted morphology, but were almost normal. Therefore, the posterior mediastinal and retroperitoneal structures appeared to exhibit neutral laterality, incomplete inverted morphology or even normal morphology. According to the personal history and present histology, this specimen was unlikely to correspond to Kartagener's syndrome. The present observations seem to be consistent with recent findings in mutant models of laterality disturbances, in which a single gene or molecule is responsible for the changes in a region-specific manner.

Major anatomical variations of the tracheobronchial tree: bronchoscopic observation

Fiberoptic and rigid bronchoscopy are widely used diagnostic and therapeutic tools in pulmonary medicine. Investigators often neglect the bronchial variations; however, bronchial variations may have important implications for bronchoscopy, brachytherapy, pulmonary resections and intubations. It is accepted that anatomic variations of the airways are due to anomalies in the development of the lungs. As a result, lung buds grow to an inappropriate number or arise at atypical sites. In the present study, we tried to determine the incidence of bronchial variations in our region. We investigated 2550 consecutive reports of bronchoscopy retrospectively. Major variations of the tracheobronchial tree were found in 2.6% of patients examined by bronchoscopy. The most frequent finding was a bifurcate pattern in the right upper lobe (47.7%). The variations were localized to the right upper lobe in 71.6% of patients. Male predominance was observed in all anatomic variations except one.

Arterial supply and biliary drainage of the dorsal liver: a dissection study using controlled specimens

Liver surgeons favor using the entity called the 'dorsal liver' (i.e. the caudate lobe and other paracavally located liver parenchyme of segments 7 and 8). According to minute dissection of 48 livers, we describe the territories of the left/right portal veins, hepatic ducts and hepatic arteries in the dorsal liver. In the caudate lobe, the right hepatic artery, rather than the left hepatic artery (23/48 vs 19/48 for right vs left, respectively), tended to supply the 'left' portal vein territory. Similarly, paradoxical drainage patterns, such as the right hepatic duct draining the left portal vein territory, were found in seven of 48 livers. In the territory of the hilar bifurcation, right hepatic artery dominance was also evident and various bile drainage patterns were found. These included double drainage by the bilateral hepatic ducts (3/48) and drainage into the confluence of bilateral ducts (6/48). In contrast, the arterial supply and biliary drainage of the paracavally located parenchyme of segments 7 and 8 usually depended on the proper segmental arteries and ducts and their variations were within the range of those found in other parts of the right lobe. Therefore, the dorsal liver concept may not be anatomical but, rather, simply aimed at usefulness in surgery. Nevertheless, clear subdivision of the caudate lobe according to biliary drainage and/or arterial supply seemed difficult because of the paradoxical relatioships among the portal vein, hepatic artery and bile duct. Consequently, the present results support extended surgery based on the dorsal liver concept for carcinomas involving the caudate lobe.

Are difficulties during transbronchial lung biopsy/brushing through a fiberoptic bronchoscope based on the bronchial anatomy?

Some of the difficulties encountered during transbronchial lung biopsy through a flexible bronchofiberscope are due to anatomical reasons, namely the branching angles of some subsegmental bronchi from their mother bronchi are large, and differences in branching angles during respiration may also be large. This makes insertion of forceps difficult. We have sometimes experienced difficulties reaching the target lesion during a transbronchial approach. Which subsegmental bronchi make transbronchial lung biopsy/brushing difficult, and are such difficulties due to anatomical reasons? To answer these questions, we firstly surveyed 10 bronchologists regarding which five subsegmental bronchi they considered to be the most difficult for transbronchial biopsy/brushing. We then measured the branching angles of subsegmental bronchi in 106 cadaver lungs. Finally, in six volunteers, we also measured differences in branching angles of the subsegmental bronchi between the point of forced inspiration and the point of forced expiration on CT images. According to the survey, left B(1+2)c was considered to be the most difficult for insertion by nine doctors, followed by bilateral B6a by seven, right B1a by five, left B3a by five and left B(1+2)a by four. The results of our dissections showed that a branching angle of over 60 masculine was present in more than 10% of specimens in B3a, B6a and B6c in the right lung and in B(1+2)c, B3a, B6a and B6c in the left lung. In addition, three-dimensional reconstructed images revealed that the angles of some subsegmental bronchi changed during respiration. Inter-individual variations were present in most subsegmental bronchi. The direction of movement of each subsegmental bronchus during respiration varied. In addition, maximum degrees of difference in angles between volunteers were sometimes as much as 80 degrees . In conclusion, branching angles of subsegmental bronchi from their mother bronchi are large in B3a, B6a and B6c in the right lung and in B(1+2)c, B3a, B6a and B6c in the left lung. Most of these correspond to those which many bronchologists felt to be difficult for insertion. In addition, changes in the angles of subsegmental bronchi during respiration are likely to partially account for difficulties encountered during transbronchial approaches.

Anatomic Evaluation of Postural Bronchial Drainage of the Lung With Special Reference to Patients With Tracheal Intubation

BACKGROUND

Although several sequences of specific postures, each corresponding to a particular lung segment, have been recommended for therapeutic bronchial drainage, these are based on little or no anatomic evidence. Moreover, because these sequences are too complex, especially for intubated patients, they require simplification.

MATERIALS AND METHODS

The courses of the segmental bronchi B(1), B(2), B(1 + 2), B(3), and B(6) and their subsegmental bronchi are extremely variable. This can result in a small branching angle at the subsegmental bronchial origin. Using 106 lungs, we measured the branching angles of the subsegmental bronchi and examined their running directions in each posture of the sequences recommended for bronchial drainage.

RESULTS

A small branching angle (< 120 degrees ) at the subsegmental bronchial origin was sometimes evident, and this made postural drainage difficult. Drainage of B(3) and B(6) was often difficult because they formed angles of < 45 degrees from the horizontal in certain postures (supine for B(3) and prone for B(6)). Further, we found a 45 degrees rotative prone position effective for draining B(1)a and B(6).

CONCLUSION

Our anatomic findings predicted increased effectiveness in a sequence of postures: supine, 45 degrees rotative prone with left side up, 45 degrees rotative prone with right side up, and return to supine for simple, safe, and effective bronchial drainage, especially for patients with tracheal intubation. The 10 degrees right-side-up supine and 45 degrees rotative prone with head raised 45 degrees positions seemed helpful if added to the basic sequence.

Human liver caudate lobe and liver segment

Recently, the caudate lobe has seemed to be the final target for aggressive cancer surgery of the liver. This lobe has five surfaces: the dorsal, left and hilar-free surfaces and the right and ventral-border planes. Surgeons have divided the caudate lobe into three parts: Spiegel's lobe, which is called the 'caudate lobe and papillary process' by anatomists, the caudate process, viewed as almost the same entity by anatomists, and the paracaval portion corresponding to the dorsally located parenchyma in front of the inferior vena cava. All three parts are supplied by primary branches originating from the left and right portal veins, including the hilar bifurcation area. The hilar bifurcation branch often (50%) supplies the paracaval portion and it sometimes (29%) extends its territory to Spiegel's lobe. It was postulated by Couinaud that the paracaval portion or the S9 is not defined by its supplying portal vein branch but by its 'dorsal location' in the liver. Couinaud's caudate lobe or dorsal-liver concept cause, and still now causes, great logical confusion for surgeons. We attempt here to describe the margins of the lobe, border branches of the portal vein, the left/right territorial border of the portal vein or Cantile's line and other topics closely relating to the surgery within these contexts. Finally, the caudate lobe as a liver segment will be discussed.