Double Inferior Vena Cava with Major Predominance of the Left Inferior Vena Cava: A Cadaver Case Report.

We encountered a case of a double inferior vena cava with major predominance of the left inferior vena cava during an anatomical dissection course for medical students in 2015. The right inferior vena cava (normal inferior vena cava) was 2.0 mm wide, and the left inferior vena cava was 23.2 mm wide. The fine right inferior vena cava began at the right common iliac vein, ascended along the right side of the abdominal aorta, and then joined the left inferior vena cava at the level of the lower margin of the first lumbar vertebra. The dominant left inferior vena cava started from the left common iliac vein and ascended along the left side of the abdominal aorta. Most patients with a double inferior vena cava are asymptomatic, and these variants are incidentally detected by computed tomography or magnetic resonance imaging. Their presence may have significant implications for surgery, particularly abdominal surgery in patients with paraaortic lymphadenopathy and in those undergoing laparoscopic radical nephrectomy or inferior vena cava filter placement. We herein discuss the embryology of a double inferior vena cava based on detailed anatomical data of the variations of a double inferior vena cava, including those that require clinical attention.

The Key Structure of the Facial Soft Tissue: The Superficial Musculoaponeurotic System.

The superficial musculoaponeurotic system (SMAS) was advocated by Mitz and Peyronie in 1976. The concept of this superficial fascia was established by surgical findings of facelift surgery and is familiar to plastic surgeons and anatomists. However, detailed characteristics of this fascia are still not widely known among head and neck surgeons. Moreover, the SMAS is generally located at the parotid and cheek regions and divides facial fat into superficial and deep layers. The SMAS connects to the superficial temporal fascia cranially and to the platysma caudally. The frontal muscle and the peripheral part of the orbicularis oculi are also in the same plane. The exact expanse of the SMAS in the face is controversial. Some authors claimed that the SMAS exists in the upper lip, whereas others denied the continuity of the SMAS to the superficial temporal fascia in a histological study. There are various other opinions regarding SMAS aside from those mentioned above. The concept of the SMAS is very important for facial soft tissue surgeries because the SMAS is a good surgical landmark to avoid facial nerve injuries. Therefore, this article summarized SMAS from an anatomical point of view.

An Anatomical Dissection Method for Observation of Fibrous Facial Structures.

BACKGROUND: In recent years, structures including the superficial musculoaponeurotic system and retaining ligaments that support the facial soft tissue have been clarified. However, these structures are very difficult to observe in their entirety by the standard gross anatomical procedure (ie, dissection from superficial to deep layers). Furthermore, accurate descriptions of these structures are rare in both anatomical and plastic surgery textbooks. The aim of this study was to clarify the facial fibrous structures in a gross anatomical view. METHODS: The authors' novel method used soft facial tissue and bone. The tissue was fixed in gelatin and sectioned at a thickness of 5 to 10 mm. Each section was placed on a wooden board; the bone was then pinned, and the skin was pulled outward with sutures to hyperextend the soft tissue. Subsequently, the loose connective tissue was torn and fat tissue was removed under a surgical microscope. After the removal of fat tissue, the fibrous facial structures (eg, the superficial musculoaponeurotic system and retaining ligaments) could be observed clearly. RESULTS: The thickness of the sections allowed three-dimensional observation, such that a structure located deep within a section could be clearly observed. The expansion of soft tissue facilitated observation of the facial layer and fibrous structures, and the locations of nerves and vessels. Therefore, the facial layer structure was readily discerned. CONCLUSION: This method is likely to be very useful in the field of plastic surgery because it enabled intuitive identification of facial layers and their characteristics. CLINICAL RELEVANCE STATEMENT: The dissection method developed by the authors reveals the connected morphology of each tissue of the face, thus providing basic data for analyzing soft tissue changes due to aging and gravity. This will be useful for the development of anti-aging medicine.

Three sublayers in the SMAS: Observations of facial soft tissue using the stretched tissue dissection method focusing on the SMAS.

The characteristics of the superficial musculoaponeurotic system (SMAS), including the morphology of each part and the connection between tissues, remain controversial. The purpose of this study is to clarify the anatomy of the SMAS using our new dissection method. In this study, six hemi-sides of heads from formalin-preserved cadavers were used. Three were used for creating a horizontal section and three were used for creating the section along the axial line perpendicular to the surface of the skin, resulting in a gradual change from the coronal section at the lateral to the sagittal section at the median. The resected head was cut into slices with widths of 7 mm. The stretched tissue dissection method was performed by fixing a tissue slice to a board and pulling the skin outward to stretch the soft tissue. Blunt dissection was then performed under a microscope. The SMAS comprises three layers: superficial, intermediate, and deep. The superficial layer is a thin membrane directly connecting to the septa in the subcutaneous fat. The deep layer is the connective tissue in contact with the sub-SMAS structure. The layer surrounded by the superficial and deep layer of the SMAS is the intermediate layer, containing connective tissue, adipose tissue, and facial muscles. The detailed findings of the SMAS obtained using this method resolve theoretical discrepancies and provide important insight for the field of facial surgery.

Bilateral Lateral Costal Branches of the Internal Thoracic Arteries: A Case Report.

We report a case of bilateral lateral costal branches (LCB) of the internal thoracic artery (ITA). On the left side, the ITA branched from the subclavian artery as a common trunk with the thyrocervical trunk. The left LCB flew into the collateral branch of the fifth intercostal artery after reaching the upper end of the sixth rib and after exiting the left ITA at the upper part of the first rib. The left ITA was disconnected near the second rib because it had been used for coronary artery bypass surgery. The right ITA arose from the anterior surface of the right subclavian artery just after the right ITA diverged from the brachiocephalic artery. The right LCB reached the upper end of the fifth rib and flew into the collateral branch of the fourth intercostal artery. The right ITA descended along the back of the costal cartilages as usual. The mechanism of the development of the LCB is thought to be due to a lateral longitudinal anastomosis connecting the inter-node arteries arising from the dorsal aorta during the embryonic phase. More anatomical and embryological studies are necessary to further elucidate this variant arterial branch.

A Retroaortic Left Renal Vein in a Female Cadaver.

We encountered a case of retroaortic left renal vein (RLRV) during an anatomical dissection course at our medical school in 2017. The case was a female cadaver who was 88 years old at death. Six roots of the left renal vein (RV) arose from the hilus of the kidney and joined to form one left renal vein, crossed dorsal to the abdominal aorta (AA) at the level of the second lumbar vertebra, and then drained into the inferior vena cava (IVC). Two roots joined at the right renal hilus to become the right RV to then drain into the IVC at the level of the first lumbar vertebral body. The reported frequency of RLRV is approximately 2%. Embryologically, the normal anastomosis of the left and right sub-cardinal veins results in the left RV traveling on the ventral surface of the AA. However, in the case presented here, the left RV traveled on the dorsal side of the AA due to the anastomosis of the left and right supra-cardinal veins and regression of the anastomosis between the left and right sub-cardinal veins. If both the dorsal and ventral anastomoses remain, the left RV travels on the dorsal and ventral sides of the aorta. Some of the clinical problems reported in association with RLRV are hematuria and abdominal pain, and the risk of damaging the RLRV during surgery of the posterior abdominal wall. Venous variants as reported herein should be kept in mind when interpreting imaging of the posterior abdominal wall or performing surgery or other invasive procedures near the RLRV.

Anatomical and Radiological Analyses of L-shaped Kidney with Vascular Anomalies.

L-shaped kidney is a congenital anomaly. The disorder results in the kidney appearing very similar in shape to horseshoe kidney (also a congenital anomaly), but either the right or left kidney is located at a position lower than the other kidney. In this report, we describe a woman with L-shaped kidney, identified during anatomical dissection, and compare the findings with clinical data obtained before her death. We discuss the embryology of L-shaped kidney based on detailed anatomical data on the kidney and its vascular system obtained by means of gross anatomical, radiological, and histological examinations. Our findings indicate the importance of detailed anatomical information when planning surgical procedures in patients with fused kidneys, as well as kidney transplantation, resection of renal carcinoma, or surgical treatment of abdominal aortic aneurysm.

Unusual muscle of the anterior neck: cadaveric findings with surgical applications.

The omohyoid muscle typically has an inferior belly originating from the superior border of the scapula, and then passes deep to the sternocleidomastoid muscle where its superior belly passes almost vertically upward next to the lateral border of sternohyoid to attach to the inferior border of the body of the hyoid bone lateral to the insertion of sternohyoid. Herein, we report an unusual variant of the omohyoid and sternohyoid muscles. As the omohyoid muscle is commonly used as a surgical landmark during neck dissections, knowledge of its variations such as the one described in the current report is important to surgeons.

Tortuous Common Carotid Artery: A Report of Four Cases Observed in Cadaveric Dissections.

A tortuous common carotid artery poses a high risk of injury during tracheotomy. Preoperative diagnosis is therefore important to avoid serious complications. We found four cases of tortuous common carotid artery during an anatomical dissection course for students. The first case was a 91-year-old woman who had bilateral tortuous common carotid arteries without arteriosclerosis. Case 2 was a 78-year-old woman who had bilateral tortuous common carotid arteries without arteriosclerosis. Case 3 was an 86-year-old woman who died from bladder cancer and who also had a right tortuous common carotid artery without arteriosclerosis. Case 4 was an 89-year-old woman who had bilateral tortuous common carotid arteries and a tortuous brachiocephalic artery with severe arteriosclerosis. Case 4 was also examined using computed tomography to evaluate the arteriosclerosis. Computed tomography revealed severe calcification of the vascular wall, which was confirmed in the aortic arch and origins of its branches. In all four cases, the tortuosity was located below the level of the thyroid gland. Based on prior study results indicating that fusion between the carotid sheath and visceral fascia was often evident at the level of the thyroid gland, we speculated that the major region in which tortuosity occurs is at the same level or inferior to the level of the thyroid gland.

A Rare Case of an Artery Passing through the Median Perforating Canal of the Mandible.

Along with the popularization of dental implant surgery, there has been considerable research on the lingual foramen using cone-beam computed tomography. Anatomical research has also revealed that the arteries entering the lingual foramina are branches of the submental and sublingual arteries. There have been no reports, however, of the submental or sublingual artery entering the mandible from the lingual foramen, perforating it, and then distributing to the inferior labial region. A 69-year-old man who donated his body to our department in 2015 was dissected. The mandible with overlying soft tissue of the mental region was resected and examined with microcomputed tomography, which showed that the canal perforated from the lingual foramen to the midline of the labial cortical plate. The canal was thus named the median perforating canal. To the best of our knowledge, there have been no other reports of a perforating artery of the mandible, so this case is thought to be rare. Hence, the existence of perforating arteries, such as in the present case, should be taken into consideration in preoperative diagnoses such as for dental implant surgery. Thus, the fusion of anatomical and radiological study is useful and necessary to understand surgical anatomy.

Gross Anatomical Dissection of a Horseshoe Kidney: The Eighth Specimen in Our Medical School.

Horseshoe kidney is a known congenital renal anomaly. During a gross anatomy dissection course for students in 2014, a horseshoe kidney was found in an 80-year-old female. The isthmus was formed by the fusion of the right and left kidneys at their lower poles and resulted in a U-shaped kidney. Both sides of the renal hilum opened ventrally. Four surplus renal arteries entered the horseshoe kidney. The first surplus renal artery arose from the right side of the abdominal aorta, and entered the lower part of the renal hilum. The second surplus artery arose from the ventral side of the abdominal aorta, and entered the left inferior part of the left renal hilum.The third surplus artery also arose from the ventral side of the abdominal aorta and entered the inferior border of the left part of the isthmus. The fourth surplus artery arose from the bifurcation of the common iliac arteries and distributed to the inferior border of the middle of the isthmus. One surplus renal vein arose from the lower border of the middle of the isthmus, descended dorsally to the abdominal aorta and the right common iliac artery, and then entered the upper wall of the left common iliac vein. The isthmus was made up of renal parenchymal structures. These findings will be useful as regards research and surgery on the horseshoe kidney. This was the eighth case of horseshoe kidney in our laboratory.

Accessory mental foramina and nerves: Application to periodontal, periapical, and implant surgery.

Recent studies investigating accessory mental foramina using developments in diagnostic imaging have primarily defined the morphology of the foramina; however, few studies have described the structures passing through them. Additional clinical knowledge of the foramina is therefore required for preoperative diagnosis prior to surgery, including implant, periodontal and periapical surgery. In this study, we investigated the accessory mental foramina and the associated nerves and arteries in donated cadaveric mandibles using anatomical and radiological observation methods. We examined 63 mandibles with overlying soft tissue by cone-beam computed tomography and noted the existence of the accessory mental foramina. Mandibles with accessory mental foramina were subsequently analyzed. Additionally, the neurovascular bundles passing through these foramina were dissected using anatomical methods.The incidence of accessory mental foramina was 14.3%. The larger foramina tended to be located anteriorly or superiorly and proximal to the mental foramen, while the smaller foramina tended to be located posterosuperiorly and distal to the mental foramen. The mental foramen ipsilateral to the accessory mental foramen was smaller than the one contralateral to it. The comparatively distant and large accessory mental foramen included an artery.This study elucidated the relationship between accessory mental foramina and the associated nerves and arteries. We believe that the results will contribute to the clinical dentistry field.

Contrast imaging study of the horseshoe kidney for transplantation.

In the surgical setting, horseshoe kidneys (HKs) may be a cause for confusion because of their complicated morphology, especially in the vicinity of the vascular and urinary collecting systems around the isthmus of the HK. In the patients with HK, analysis of the anatomical structure of the isthmus is both useful and necessary. The aim of this study is to observe the vascular and collecting system of the HK using anatomical and contrast imaging technique, then make use of the knowledge for clinical anatomy. A HK voluntarily donated post-mortem to our department in 2013 by an 80-year-old woman was dissected. The gross anatomy of this HK was reported. In this study, we additionally analyzed this kidney using micro-computed tomography with both colored and colorless contrast media after the kidney was made transparent. Contrast imaging clearly revealed that each of the five renal arteries, including the three surplus renal arteries, entering the HK distributed blood to different regions. Neither side of the urinary collecting system crossed the midline of the isthmus. Two surplus renal veins emerged from the HK and two ureters descended dorsal to the isthmus. These observations show that gross anatomical observation and contrast imaging of the HK can provide very important surgical information. Our results can contribute to both better understanding of fundamental knowledge and progress in the surgery of HKs such as in the setting of biopsy and transplantation.

Anatomical Research of the Three-dimensional Route of the Thoracodorsal Nerve, Artery, and Veins in Latissimus Dorsi Muscle.

BACKGROUND: The latissimus dorsi (LD) muscle flap has been widely used in facial reanimation surgery. However, there are no standards to what degree the muscle flap may be safely thinned because the three-dimensional positional relationship of thoracodorsal artery, vein, and nerve inside the LD muscle is poorly understood. METHODS: From 18 formalin-fixed cadavers, we made 36 transparent specimens of LD muscles using a newly developed decoloration technique. In 26 specimens, nerve staining (Sihler's staining method) and silicone rubber (Microfil) injection to the thoracodorsal artery were performed, and the relationship of the artery and the vein was examined in 10 specimens. RESULTS: The thoracodorsal artery and vein always ran parallel in a deeper layer compared to the nerve. The thoracodorsal nerve constantly existed in a deeper layer than half (50%) of the muscle in the range of use of the muscle flap in facial reanimation surgery. CONCLUSIONS: The thoracodorsal nerves ran in a shallower layer, and the depth to the nerve in the muscle flap in actual facial reanimation surgery is safe enough to avoid damage to the nerves. The LD muscle may be thinned to half its original thickness safely.