The cisterna chyli: a systematic review of definition, prevalence, and anatomy.

The cisterna chyli is a lymphatic structure found at the caudal end of the thoracic duct that receives lymph draining from the abdominal and pelvic viscera and lower limbs. In addition to being an important landmark in retroperitoneal surgery, it is the key gateway for interventional radiology procedures targeting the thoracic duct. A detailed understanding of its anatomy is required to facilitate more accurate intervention, but an exhaustive summary is lacking. A systematic review was conducted, and 49 published human studies met the inclusion criteria. Studies included both healthy volunteers and patients and were not restricted by language or date. The detectability of the cisterna chyli is highly variable, ranging from 1.7 to 98%, depending on the study method and criteria used. Its anatomy is variable in terms of location (vertebral level of T10 to L3), size (ranging 2-32 mm in maximum diameter and 13-80 mm in maximum length), morphology, and tributaries. The size of the cisterna chyli increases in some disease states, though its utility as a marker of disease is uncertain. The anatomy of the cisterna chyli is highly variable, and it appears to increase in size in some disease states. The lack of well-defined criteria for the structure and the wide variation in reported detection rates prevent accurate estimation of its natural prevalence in humans.

The reliability of the measurement of muscle volume using magnetic resonance imaging in typically developing infants by two raters.

To assess intra-rater and inter-rater reliability of the manual segmentation of Magnetic Resonance Imaging (MRI) for the in vivo measurement of infant muscle volume of the knee extensor and flexor muscles by two raters. Muscles of the knee extensor and flexor muscle of ten typically developing infants (86 days ± 7 days) were scanned with MRI (Proton density sequence). Scans were then segmented using Slicer software, and volumes rendered by two raters. Intra-rater and inter-rater reliability were assessed using intra-class correlation (ICC), with mean difference (MD), standard error of the mean (SEM), and minimal detectable change (MDC) for each muscle calculated. ICCs for Intra-rater reliability of the segmentation process for the muscle volume of the muscles of the knee extensors and flexor muscles were 0.901-0.972, and 0.776-0.945 respectively, with inter-rater reliabilities between 0.914-0.954 and 0.848-0.978, for the knee extensor and flexors muscles respectively. For intra-rater reliability, MD ≤ - 0.47 cm3, MDCs for were < 1.09 cm3 and for inter-rater MD ≤ - 1.40 cm3, MDCs for were < 1.63 cm3 for all muscles. MRI segmentation for muscle volumes showed good to excellent reliability, though given the small volumes of the muscles themselves, variations between raters are amplified. Care should be taken in the reporting and interpretation of infant muscle volume.

The effect of needle length and skin to deltoid muscle distance in adults receiving an mRNA COVID-19 vaccine.

BACKGROUND: The mRNA COVID vaccines are only licensed for intramuscular injection but it is unclear whether successful intramuscular administration is required for immunogenicity. METHODS: In this observational study, eligible adults receiving their first ComirnatyTM/BNT162b2 dose had their skin to deltoid muscle distance (SDMD) measured by ultrasound. The relationship between SDMD and height, weight, body mass index, and arm circumference was assessed. Three needle length groups were identified: 'clearly sufficient' (needle exceeding SDMD by >5 mm), 'probably sufficient' (needle exceeding SDMD by ≤ 5 mm), and 'insufficient' (needle length ≤ SDMD). Baseline and follow-up finger prick blood samples were collected and the primary outcome variable was mean spike antibody levels in the three needle length groups. RESULTS: Participants (n = 402) had a mean age of 34.7 years, BMI 29.1 kg/m2, arm circumference 37.5 cm, and SDMD 13.3 mm. The SDMD was >25 mm in 23/402 (5.7%) and >20 mm in 61/402 (15.2%) participants. Both arm circumference (≥40 cm) and BMI (≥33 kg/m2) were able to identify those with a SDMD of >25 mm, the length of a standard injection needle, with a sensitivity of 100% and specificities of 71.2 and 79.9%, respectively. Of 249/402 (62%) participants with paired blood samples, there was no significant difference in spike antibody titres between needle length groups. The mean (SD) spike BAU/mL was 464.5 (677.1) in 'clearly sufficient needle length' (n = 217) compared with 506.4 (265.1) in 'probably sufficient' (n = 21, p = 0.09), and 489.4 (452.3) in 'insufficient needle length' (n = 11, p = 0.65). CONCLUSIONS: A 25 mm needle length is likely to be inadequate to ensure vaccine deposition within the deltoid muscle in a small proportion of adults. Vaccine-induced spike antibody titres were comparable in those vaccinated with a needle of sufficient versus insufficient length suggesting deltoid muscle deposition may not be required for an adequate antibody response to mRNA vaccines.

Pediatric paranasal sinuses-Development, growth, pathology, & functional endoscopic sinus surgery.

The paranasal sinuses (maxillary, frontal, ethmoid, and sphenoid sinuses) are complex anatomical structures. The development and growth of these have been investigated utilizing a number of different methods ranging from cadaveric analysis to modern cross sectional imaging with 3D modeling. An understanding of normal pediatric paranasal sinus embryology and development enables us to better determine when pathology may be affecting the normal developmental process. Cystic fibrosis, chronic sinusitis, deviated nasal septum and cleft lip and palate are some of the conditions which have been shown to effect paranasal sinus development to varying degrees. Functional endoscopic sinus surgery (FESS) is becoming increasingly common and an understanding of sinus anatomy together with when periods of rapid growth occur during childhood is important clinically. Although concerns have been raised regarding the impact of FESS on facial growth, there is limited evidence of this in regards to either changes in anthropomorphic measurements or clinical assessments of symmetry post operatively.

The reliability and validity of triceps surae muscle volume assessment using freehand three-dimensional ultrasound in typically developing infants.

This study assessed the intra-acquirer, intra- and inter-processor reliability, and validity of the in vivo assessment of the medial gastrocnemius (MG), lateral gastrocnemius (LG) and soleus (SOL) muscle volumes using freehand 3D ultrasound (3DUS) in typically developing infants. Reliability assessments of freehand 3DUS were undertaken in infants across three ages groups: three, six and twelve months of age, with validity testing completed against magnetic resonance imaging (MRI) in infants at 3 months of age. Freehand 3DUS scanning was carried out by a single acquirer, with two independent processors manually segmenting images to render volumes. MRI images were segmented independently by a separate processor, with the volumes compared to those obtained via freehand 3DUS. Reliability was assessed using intraclass correlation (ICC), coefficient of variance (CV) and minimal detectable change (MDC) across each assessment time point. Validity was assessed using the limits of agreement. ICCs for intra-acquirer reliability of the acquisition process for freehand 3DUS ranged from 0.91 to 0.99 across all muscles. ICCs for intra-processor and inter-processor reliability for the segmentation process of freehand 3DUS ranged from 0.80 to 0.98 across all muscles. Acceptable levels of agreement between muscle volume obtained by freehand 3DUS and MRI were found for all muscles; however, freehand 3DUS overestimated muscle volume of MG and LG and underestimate the SOL compared with MRI, with average absolute differences of MG = 0.3 ml, LG = 0.3 ml and Sol = 1.2 ml. Freehand 3DUS is a reliable method for measuring in vivo triceps surae muscle volume in typically developing infants. We conclude that freehand 3DUS is a useful tool to assess changes in muscle volume in response to growth and interventions in infants.

The effect of respiration and body position on terminal thoracic duct diameter and the lymphovenous junction: An exploratory ultrasound study.

The thoracic duct (TD) drains most of the body's lymph back to the venous system via its lymphovenous junction (LVJ), playing a pivotal role in fluid homeostasis, fat absorption and the systemic immune response. The respiratory cycle is thought to assist with lymph flow, but the precise mechanism underpinning terminal TD lymph flow into the central veins is not well understood. The aim of this study was to use ultrasonography (US) to explore the relationship between terminal TD lymph flow, the respiratory cycle, and gravity. The left supraclavicular fossa was scanned in healthy non-fasted volunteers using high-resolution (13-5 MHz) US to identify the terminal TD and the presence of a lymphovenous valve (LVV). The TD's internal diameter was measured in relation to respiration (inspiration vs. expiration) and body positioning (supine vs. Trendelenburg). The terminal TD was visualized in 20/33 (61%) healthy volunteers. An LVV was visualized in only 4/20 (20%) cases. The mean terminal TD diameter in the supine position was 1.7 mm (range 0.8-3.1 mm); this increased in full inspiration (mean 1.8 mm, range 0.9-3.2 mm, p < 0.05), and in the Trendelenburg position (mean 1.8 mm, range 1.2-3.1 mm, p < 0.05). The smallest mean terminal TD diameter occurred in full expiration (1.6 mm, range 0.7-3.1 mm, p < 0.05). Respiration and gravity impact the terminal TD diameter. Due to the challenges of visualizing the TD and LVJ, other techniques such as dynamic magnetic resonance imaging will be required to fully understand the factors governing TD lymph flow.

The bell-clapper deformity of the testis: The definitive pathological anatomy.

INTRODUCTION: The bell-clapper deformity (BCD) predisposes to intravaginal torsion (IVT) and is classically bilateral. The precise pathological definition of what constitutes a BCD is not clear. The current study aims to clarify the specific anatomic details of this anomaly. METHODS: A systematic review was performed utilizing the PRISMA principles. Studies are presented chronologically based on their level of evidence. They are further divided into study types: autopsy and operative studies of acute torsion, intermittent torsion and studies of the contralateral testis in vanishing testis. RESULTS: The bell-clapper deformity is best defined by complete investment of the testis, epididymis and a length of the spermatic cord by the tunica vaginalis. Based on autopsy studies the rate of BCD in scrotal testis varied from 4.9% to 16%; with bilaterality in 66%-100%. In cases of acute IVT bilaterality was noted in 54%-100%. The most disparate results were in cases of testicular regression syndrome where contralateral BCD was noted in 0%-87% of cases. CONCLUSION: We suggest future studies employ the strict anatomical definition above. As there is evidence of age-dependent investment of the testes, it will be important to develop age-standardized measurements of intravaginal length of spermatic cord. This critical morphometric measurement will allow a better understanding of the risk of IVT. LEVEL OF EVIDENCE: Systematic review of diagnostic studies: lowest level of evidence of included manuscripts Level IV (case-control studies with a poor reference standard).

Side predilection in congenital anomalies of the kidney, urinary and genital tracts.

BACKGROUND: There appear to be various patterns of sidedness with relation to the common urogenital malformations observed in pediatric urology. The objective of this statistical review was to synthesize this data and to assess if these patterns are significant. MATERIALS AND METHODS: Eighteen urogenital conditions were investigated and for each condition the five largest studies that noted laterality were included. The sidedness of each condition was then analysed for statistical significance. RESULTS: Three conditions had a statistically significant higher proportion on the right side: palpable undescended testis (63%, p = 0.0002), inguinal hernia (59%, p = 0.0001) and hydrocele (60%, p = 0.003). Three conditions were significantly more common on the left side: impalpable undescended testis (59%, p = 0.0008), renal agenesis (54%, p = 0.02) and vesico-ureteric junction obstruction (71%, p < 0.0001) while both pelvi-ureteric junction obstruction (62%, p = 0.09) and absent vas deferens (61%, p = 0.11) were trending towards significance. CONCLUSIONS: Various urogenital malformations display a predilection for one side. Proximal malformations tend to be more frequently seen on the left side, where as inguinoscrotal malformations are more frequently observed on the right. There is an increasing body of literature regarding aetiological factors for these conditions. However, our current understanding of the pathophysiology of these conditions does not completely explain this pattern of observation.

Understanding the Lingual Frenulum: Histological Structure, Tissue Composition, and Implications for Tongue Tie Surgery.

Lingual frenotomy has become an increasingly common surgical procedure, performed for a broad range of indications from birth through adulthood. This study utilizes histology to define the structure and tissue composition of the lingual frenulum and floor of mouth (FOM) fascia. En bloc specimens of anterior tongue, lingual frenulum, and FOM tissues were harvested from ten embalmed adult cadavers. An additional three fresh tissue cadaveric specimens were frozen with the tongue supported in an elevated position, to enable harvesting and paraffin embedding of the elevated lingual frenulum as a discrete specimen. All 13 specimens were prepared as ten-micron coronal sections using stains to determine the general morphology of the lingual frenulum, its relationship to neighbouring structures (Mason's Trichrome), presence of elastin fibers (Verhoeff-van Gieson), and collagen typing (Picrosirius Red). Our results have shown a submucosal layer of fascia spanning horizontally across the FOM was present in all specimens, with variability in fascial thickness and histologic composition. This FOM fascia suspends the sublingual glands, vessels, and genioglossus from its deep surface. The elevated lingual frenulum is formed by a central fold of this FOM fascia together with the overlying oral mucosa with variability in fascial thickness and composition. With tongue elevation, the fascia mobilizes to a variable extent into the fold forming the frenulum, providing a structural explanation for the individual variability in lingual frenulum morphology seen in clinical practice.

Reappraisal of the classical abdominal anatomical landmarks using in vivo computerized tomography imaging.

INTRODUCTION: With expanding scope of interventions it becomes mandatory to have correct and evidence-based knowledge of surface anatomy of internal abdominal structures. Information available in text books is derived from work done on cadaveric studies. Current study was designed to provide data of key abdominal surface anatomical landmarks and their variations in living subjects using CT imaging of adult population. MATERIALS AND METHODS: Cross-sectional study was conducted using 100 abdominopelvic CT scans of patients of Indian origin. RESULTS: Vertebral levels of origin of celiac trunk varied from T11 to L1/2 intervertebral disc, superior mesenteric artery from T12 to L2, inferior mesenteric artery from L2 to L4 and aortic bifurcation from L3 to L5. Origin of both renal arteries varied between T12 and L2 and the formation of inferior vena cava varied from L3 to L5. Vertebral levels of upper pole of both kidneys ranged from T11 to upper L3. Spleen was related to 9th to 11th ribs in 36% and 10th to 12th ribs in 34% scans. Most common vertebral levels of subcostal plane, planum supracristale and planum intertuberculare noticed were lower L2, L4 and lower L5, respectively. CONCLUSIONS: Data derived from imaging investigations of living subjects and variations from the conventional descriptions observed in the current study might be helpful for clinicians.

The 3-D muscular structure of the human pancreaticobiliary junction

The musculature of the human pancreaticobiliary junction (PBJ) is implicated in several pathologies and is of significance to clinicians who perform endoscopic retrograde cholangiopancreatography (ERCP). This study sought to describe the musculature of the human PBJ by generating a three-dimensional reconstruction of histologic sections. A single pancreaticoduodenal specimen was removed en bloc from an embalmed cadaver with no pancreaticoduodenal disease. Sections were stained with Masson's trichrome and the staining pattern of muscle fibers was used to generate information regarding their location and orientation. The outline of groups of muscle fibers taken from photomicrographs of alternate thin serial sections were highlighted based upon their orientation (circular or longitudinal) and location (duodenal or papillary). Data point co-ordinates were used to create a 3-D image reconstruction.A total of 91 composite serial cross-sections were reconstructed. Circular and longitudinal muscle fibers formed a completely investing muscle layer around both the bile and pancreatic ducts, and there was a clear distinction between the intrinsic muscles of the PBJ and those of the duodenal wall. Circular fibers were particularly dense distal to the confluence of the ducts. Longitudinal fibers were incompletely distributed around the pancreaticobiliary sphincter and did not extend to the tip of the major duodenal papilla. This model supports the well-established concept of an intrinsic pancreaticobiliary sphincter composed of circular and longitudinal muscle fibers, distinct from the surrounding duodenal muscle. Targeting the distal end of the PBJ during ERCP would only partially disrupt this muscular sphincter mechanism

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Therapeutic delivery to the peritoneal lymphatics: Current understanding, potential treatment benefits and future prospects.

The interest in approaches to deliver therapeutics to the lymphatic system has increased in recent years as the lymphatics have been discovered to play an important role in a range of disease states such as cancer metastases, inflammatory and metabolic disease, and acute and critical illness. Therapeutic delivery to lymph has the potential to enhance treatment of these conditions. Currently much of the existing data explores therapeutic delivery to the lymphatic vessels and nodes that drain peripheral tissues and the intestine. Relatively little focus has been given to understanding the anatomy, function and therapeutic delivery to the peritoneal lymphatics. Gaining a better understanding of peritoneal lymphatic structure and function would contribute to the understanding of disease processes involving these lymphatics and facilitate the development of delivery systems to target therapeutics to the peritoneal lymphatics. This review explores the basic anatomy and ultrastructure of the peritoneal lymphatics system, the lymphatic drainage pathways from the peritoneum, and therapeutic and delivery system characteristics (size, lipophilicity and surface properties) that favour lymph uptake and retention after intraperitoneal delivery. Finally, techniques that can be used to quantify uptake into peritoneal lymph are outlined, providing a platform for future studies.

Defining the anatomy of the neonatal lingual frenulum.

The lingual frenulum is recognized as having the potential to limit tongue mobility, which may lead to difficulties with breastfeeding in some infants. There is extensive variation between individuals in the appearance of the lingual frenulum but an ambiguous relationship between frenulum appearance and functional limitation. An increasing number of infants are being diagnosed with ankyloglossia, with growing uncertainty regarding what can be considered "normal" lingual frenulum anatomy. In this study, microdissection of four fresh tissue premature infant cadavers shows that the lingual frenulum is a dynamic, layered structure formed by oral mucosa and the underlying floor of mouth fascia, which is mobilized into a midline fold with tongue elevation and/or retraction. Genioglossus is suspended from the floor of mouth fascia, and in some individuals can be drawn up into the fold of the frenulum. Branches of the lingual nerve are located superficially on the ventral surface of the tongue, immediately beneath the fascia, making them vulnerable to injury during frenotomy procedures. This research challenges the longstanding belief that the lingual frenulum is a midline structure formed by a submucosal "band" or "string" and confirms that the neonatal lingual frenulum structure replicates that recently described in the adult. This article provides an anatomical construct for understanding and describing variability in lingual frenulum morphology and lays the foundation for future research to assess the impact of specific anatomic variants of lingual frenulum morphology on tongue mobility. Clin. Anat. 32:824-835, 2019. © 2019 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

T2 relaxation time measurements in tibiotalar cartilage after barefoot running and its relationship to ankle biomechanics.

The influence of ankle kinematics and plantar pressure from mid-range barefoot running on T2 relaxation times of tibiotalar cartilage is unknown. This study aimed to quantitatively evaluate the T2 relaxation time of tibiotalar cartilage and ankle biomechanics following 5 km barefoot running. Twenty healthy runners (who had no 5 km barefoot running experience) underwent 3.0-Tesla magnetic resonance (MR) scans and assessment of running gait before and after 5 km barefoot running. Participants were divided into two groups consisting of marathon-experienced (n = 10) and novice (n = 10) with equal number of males and females in each group. Three musculoskeletal radiologists measured T2 relaxation times in 18 regions of the ankle cartilage: anterior zone, central zone, and posterior zone, or lateral, middle, and medial sections in the sagittal plane. Three-dimensional ankle kinetics, kinematics, and plantar pressure were all also assessed during barefoot running. In the novice group, the T2 relaxation time in the posterior zone of tibial cartilage (p = 0.001) and lateral section in both tibial (p = 0.02) and talar (p = 0.02) cartilage were significantly increased after barefoot running. Ankle kinematics exhibited significant changes in females. Plantar loading was shifted from the medial to lateral aspect after running. This included a significant reduction in the loading under the toes and the 1st, 2nd and 3rd metatarsals, with a significant increase under the 4th and 5th metatarsals and lateral midfoot. The results suggest that plantar pressure may directly lead to local increases in cartilage T2 signal, which was not associated with changes in ankle kinematics.

The effect of supine positioning on maternal hemodynamics during late pregnancy.

Introduction: Recent studies have demonstrated an association between maternal supine sleep position and an increased risk of late stillbirth. During late pregnancy, the gravid uterus compresses the inferior vena cava (IVC) when a woman lies in the supine position. The azygos system of veins is the dominant pathway of collateral venous return back to the heart in the event of acute obstruction of the IVC. It is suggested that this pathway provides adequate collateral venous circulation in the event of IVC compression in the supine position during late pregnancy. Objective: Investigate the effect of supine positioning on maternal hemodynamics during late pregnancy and the role of collateral venous circulation. Methods: Ethics approval was obtained and 12 women with singleton pregnancies between 35- and 38-week gestation underwent magnetic resonance imaging in the supine and left lateral decubitus positions using a Skyra 3T system (Siemens). Phase-contrast images were evaluated to measure cardiac output, blood flow through the azygos vein, and blood flow through the abdominal aorta (AA) and IVC at two levels: at the level of aortic bifurcation and immediately above the renal veins. Results: The supine position was associated with a 16.4% reduction in cardiac output when compared to the left lateral position. In addition, blood flow through the IVC decreased at its origin by 85.3% and by 44.4% at the level of the renal veins. Blood flow through the azygos vein increased in the supine position by 220%. Blood flow through the AA at the level of the renal veins did not differ significantly; however, it is reduced by 32.3% at the level of the aortic bifurcation. Conclusions: Women in late pregnancy experience an increase in collateral venous blood flow when lying supine, likely as a response to marked compression of the IVC in this position. However, cardiac output and aortic blood flow were found to decrease while in the supine position.

Benign Posttraumatic Pseudopneumoperitoneum.

OBJECTIVE: The objective of our study was to retrospectively determine the anatomic distribution of chest wall ectopic gas resembling pneumoperitoneum (i.e., pseudopneumoperitoneum) and its relationship with trauma mechanisms and clinical outcomes using CT. MATERIALS AND METHODS: Investigators from two separate trauma referral centers screened 492 chest, abdomen, and pelvis CT examinations of patients who had sustained any form of trauma between 2010 and 2015. After excluding 186 patients with recognized causes of ectopic gas, 306 patients (211 men and 95 women; mean age, 44.5 years; range, 6-95 years) remained for analysis by two radiology residents in center 1 and a radiology resident in center 2. Positive cases were reviewed by all investigators, including an experienced fellowship-trained abdominal radiologist. The anatomic location of the pseudopneumoperitoneum, injury severity score, trauma velocity (high speed vs low or unknown speed), trauma mechanism, clinical findings on follow-up, and exploratory laparotomy data were collected for patients with pseudopneumoperitoneum. Two hundred consecutive nontrauma CT examinations from 2015 were selected as control cases by a resident in center 1. The t test and chi-square test were used for determining associations. RESULTS: Pseudopneumoperitoneum was identified in 5.2% of patients, occurring bilaterally adjacent to the lower six costochondral junctions, and was significantly more common with high-velocity trauma than with low-velocity trauma (p = 0.010). None of the patients with pseudopneumoperitoneum had evidence of perforated hollow viscus at surgery (n = 2) or on clinical follow-up (n = 14). No patients had unnecessary surgery due to pseudopneumoperitoneum. CONCLUSION: Pseudopneumoperitoneum is a posttraumatic phenomenon centered near the lower six costochondral junctions. Recognizing these findings may help prevent unnecessary laparotomy in the trauma setting.

The collateral venous system in late pregnancy: A systematic review of the literature.

Recent literature has reported an association between maternal supine sleep position and stillbirth during late pregnancy. In this position the gravid uterus almost completely obstructs the inferior vena cava. A small number of women experience supine hypotension, thought to be due in part to inadequate collateral venous circulation. The aim of this paper is to review the literature describing the anatomy of the collateral venous system and in particular the azygos system, the abdominal portion of which has not been well studied. A systematic review was conducted using the electronic databases: Medline, Embase, Scopus, and Google Scholar. Relevant anatomical and radiological literature concerning the azygos system in particular was reviewed. The search was limited to adult human studies only. The collateral venous system can be divided into superficial, intermediate and deep systems. The azygos system in particular provides immediate collateral venous circulation in the event of acute inferior vena caval obstruction. The abdominal portion of this pathway, including the ascending lumbar vein, has not been well studied and there are certain variations that can render it ineffective. In conclusion, the collateral venous system provides an alternative route for blood to flow back to the systemic circulation when acute occlusion of the inferior vena cava occurs in the supine position during late pregnancy. However, certain anatomical variations can render this pathway ineffective, and this could have implications for the development of supine hypotension and stillbirth in late pregnancy. Clin. Anat. 30:1087-1095, 2017. © 2017 Wiley Periodicals, Inc.