Utility of Common Bile Duct Identification on Biliary Ultrasound in Emergency Department Patients.

Background: Biliary ultrasound is often utilized in the evaluation of abdominal pain in the Emergency Department (ED). Common bile duct (CBD) identification is traditionally a standard component of the biliary ultrasound examination but can be challenging to perform for the novice sonographer. Previous work has demonstrated that CBD dilatation is rare in cases of cholecystitis with normal liver function tests (LFTs). We sought to assess the frequency of CBD dilatation in the subset of ED patients undergoing hepatobiliary ultrasound who have normal LFTs and an absence of gallstones or biliary sludge on ultrasound. We also performed an assessment of changes in CBD diameter by age and cholecystectomy status. Methods: This was a retrospective chart review at a single academic ED. Patients were enrolled in the study if they underwent a radiology performed (RP) hepatobiliary ultrasound within the 2 year study period. Records were reviewed for the presence of gallstones or sludge, CBD diameter, age, clinical indication for the ultrasound, and LFTs. Descriptive analyses were performed, and interobserver agreement among data abstractors was assessed by K analysis for the presence of CBD dilatation. The Mann-Whitney test was utilized to assess statistical significance in the comparison of differences between CBD diameters amongst age groups. Results: Of 1929 RP hepatobiliary ultrasounds performed in the study period, 312 were excluded and 1617 met inclusion criteria. Amongst these, there were 506 patients who had normal LFTs and an ultrasound with no stones or sludge. Ten patients within this group had a dilated CBD > 7 mm (1.98%, 95% CI of 1.08% to 3.6%). We also noted a statistically significant increase in CBD size in the older age cohort and in those individuals with a history of cholecystectomy. Conclusion: CBD dilation in ED patients who present with normal LFTs and an absence of gallstones and biliary sludge is rare. Physicians should be reassured that the routine identification of the CBD on ultrasound in this setting is of low yield and need not be pursued.

The common bile duct is often taught as part of the biliary point-of-care ultrasound examination. However, it is more challenging to identify than the gallbladder and thus may limit adoption of POCUS by ED physicians. Our study adds to the body of work demonstrating that omitting the common bile duct from an ultrasound evaluation is likely reasonable when both the gallbladder and liver function tests are normal. Our study also adds to the literature regarding the increase in common bile duct size with age and with post-cholecystectomy status.

Comparison of transvaginal ultrasound utilization between radiology and point of care ultrasound in first trimester pregnancy.

BACKGROUND: Transvaginal (TVUS) and transabdominal ultrasound (TAUS) are both utilized in the evaluation of early pregnancy patients. While many practitioners using point of care ultrasound (POCUS) will generally not pursue TVUS in cases where an intrauterine pregnancy (IUP) is visualized on TAUS, this may not be true in Radiology performed ultrasound. OBJECTIVES: To evaluate for differences in transvaginal ultrasound (TVUS) utilization between Radiology performed (RP) ultrasound and point of care ultrasound (POCUS) by Emergency Department (ED) physicians in early pregnancy patients. Secondarily, to assess length of stay (LOS) differences and the impact of specialized emergency ultrasound training on TVUS utilization. METHODS: This was a retrospective study at a single academic ED. Study population was all ED patients who underwent first trimester ultrasound during the one year period of March 1, 2021 to February 28, 2022. Variables evaluated were chief complaint, gestational age, LOS, TAUS and TVUS utilization, ultrasound findings, and ultrasound specialty training of the ED physician. RESULTS: There were 133 cases of POCUS ultrasound and 254 cases of RP ultrasound. All cases had TAUS imaging performed. Median LOS for patients when POCUS was utilized was 207 min (IQR 151-294) and 258 min (IQR 208-328) for those only using RP ultrasound, p ≤ 0.001. In the POCUS cohort, 38% (95% CI 30%-46%) received TVUS, while 94% received TVUS in the RP cohort (95% CI 90%-96%), p ≤ 0.001. Patients seen by ED faculty with ultrasound specialty training had TVUS 53% of the time (95% CI 41%-65%), while those seen by other ED faculty had TVUS 79% (95% CI 74%-83%) of the time, p = 0.035. CONCLUSION: POCUS in early pregnancy is associated with a significant reduction in TVUS usage. We suspect that POCUS users elect not to pursue TVUS after an IUP is identified on TAUS, while technicians perform protocol-based TVUS irrespective of TAUS findings. Patients seen by ultrasound trained ED physicians are less likely to receive TVUS.

Choroid plexus arteriovenous malformations: A systematic review.

To systematically review the reported outcomes and complications of different treatment options for choroid plexus arteriovenous malformations (AVMs), specifically focusing on surgical resection and endovascular embolization. A systematic literature review was performed using a PubMed query for studies published between January 1975 and July 2021. All studies describing the clinical presentation, management, and outcome of confirmed choroid plexus AVM cases were included. A total of 20 studies were included in the final analysis. Of these, 18 were singlepatient case reports, one article contained two patients, and a single study was a cohort of 24 patients. Patient age ranged from one day to 61 years, with a mean of 31.8±20.4 years. Most choroid plexus AVMs were located in the lateral ventricles (14 patients, 70.0%), while there were four (20.0%) located in the third ventricle, and two in the fourth ventricle (10.0%). Almost all patients were treated with surgical resection (18 patients, 90%). In 14 patients (77.8%), complete resection of the AVM was achieved. A residual AVM was reported in one case (5.6%). Most patients were reported to have improved from their presentation status over time (14 patients, 70.0%). Presence or absence of long-term sequelae (e.g., neurologic deficits) were reported for 14 patients (70%). Eleven of these patients (78.6%) were reported to have no neurological sequelae. While data on choroid plexus AVMs remains limited, the available evidence suggests gross total resection of lesions in this location can be safely achieved with subsequent reduction in preoperative symptoms.

The probability of speciation on an interaction network with unequal substitution rates.

Speciation is characterized by the development of reproductive isolating barriers between diverging groups. A seminal paper of a mathematical model of speciation was published by Orr (1995), extended by Livingstone et al. (2012) to incorporate interaction networks. Here, we further develop the model to take into account the possibility of different substitution rates for network nodes of different connectivity. Mathematically, this amounts to sampling nodes from an undirected graph where the inclusion probability for a given node depends on its degree (number of connecting edges). We establish formulas for the rate of speciation and identify a crucial parameter that is a measure of the deviation from simple random sampling.

A stochastic model for the development of Bateson-Dobzhansky-Muller incompatibilities that incorporates protein interaction networks.

Speciation is characterized by the development of reproductive isolating barriers between diverging groups. Intrinsic post-zygotic barriers of the type envisioned by Bateson, Dobzhansky, and Muller are deleterious epistatic interactions among loci that reduce hybrid fitness, leading to reproductive isolation. The first formal population genetic model of the development of these barriers was published by Orr in 1995, and here we develop a more general model of this process by incorporating finite protein-protein interaction networks, which reduce the probability of deleterious interactions in vivo. Our model shows that the development of deleterious interactions is limited by the density of the protein-protein interaction network. We have confirmed our analytical predictions of the number of possible interactions given the number of allele substitutions by using simulations on the Saccharomyces cerevisiae protein-protein interaction network. These results allow us to define the rate at which deleterious interactions are expected to form, and hence the speciation rate, for any protein-protein interaction network.

Using student-generated UV-induced Escherichia coli mutants in a directed inquiry undergraduate genetics laboratory.

We report a thematic sequence of directed inquiry-based labs taking students from bacterial mutagenesis and phenotypic identification of their own self-created mutant, through identification of mutated genes by biochemical testing, to verification of mutant alleles by complementation, and finally to mutant allele characterization by DNA sequence analysis. The lab utilizes UV mutagenesis with wild-type Escherichia coli and a UV-sensitive isogenic derivative optimized for undergraduate use. The labs take advantage of the simplicity of E. coli in a realistic genetic investigation using safe UV irradiation methods for creation and characterization of novel mutants. Assessment data collected over three offerings of the course suggest that the labs, which combine original investigation in a scientifically realistic intellectual environment with learned techniques and concepts, were instrumental in improving students' learning in a number of areas. These include the development of critical thinking skills and understanding of concepts and methods. Student responses also suggest the labs were helpful in improving students' understanding of the scientific process as a rational series of experimental investigations and awareness of the interdisciplinary nature of scientific inquiry.

Patterns of variation in the evolution of carotenoid biosynthetic pathway enzymes of higher plants.

Cellular metabolic networks depend on the products of many loci for proper functioning. These interrelationships between loci at the phenotypic level raise the question of whether they evolve independently. Previous research has demonstrated that in the anthocyanin pathway, which produces important secondary metabolites in plants, the genes encoding downstream enzymes show an increased rate of change at nonsynonymous sites when compared with upstream loci due to relaxed constraint. To test whether this pattern exists more broadly, we compared a set of 4 genes encoding enzymes of the carotenoid biosynthetic pathway, which produces a set of distinct colored secondary metabolites in plants. Comparisons between copies of phytoene desaturase, zeta-carotene desaturase, lycopene beta-cyclase, and zeaxanthin epoxidase from 6 taxa indicate that the 3 upstream enzymes (phytoene desaturase, zeta-carotene desaturase, and lycopene beta-cyclase) have similar proportions of codons under selective constraint, whereas the most downstream enzyme (zeaxanthin epoxidase) has more codons evolving under relaxed constraint. Overall, nonsynonymous substitution rates appear to be highest for zeaxanthin epoxidase, whereas synonymous substitution rates were highest for the intermediate enzyme lycopene beta-cyclase. Analysis of codon bias shows that only lycopene beta-cyclase may be under slight selection pressure for codon usage. Taken together, these results show that the enzymes of the carotenoid biosynthetic pathway are under strong selective constraint but that the most downstream enzyme is under the least constraint.

Using variable rate models to identify genes under selection in sequence pairs: their validity and limitations for EST sequences.

Using likelihood-based variable selection models, we determined if positive selection was acting on 523 EST sequence pairs from two lineages of sunflower and lettuce. Variable rate models are generally not used for comparisons of sequence pairs due to the limited information and the inaccuracy of estimates of specific substitution rates. However, previous studies have shown that the likelihood ratio test (LRT) is reliable for detecting positive selection, even with low numbers of sequences. These analyses identified 56 genes that show a signature of selection, of which 75% were not identified by simpler models that average selection across codons. Subsequent mapping studies in sunflower show four of five of the positively selected genes identified by these methods mapped to domestication QTLs. We discuss the validity and limitations of using variable rate models for comparisons of sequence pairs, as well as the limitations of using ESTs for identification of positively selected genes.

Chromosomal evolution and speciation: a recombination-based approach.

Although karyotypic differences between species have long been recognized, the question of whether these mutations play a causal role in speciation remains unanswered. This is because most models of chromosomal speciation focus on underdominance, which presents a theoretical paradox in that the strength of an underdominant barrier is inversely proportional to its fixation probability. To counter this problem, a new model has been proposed that focuses on the modification of effective recombination rates, whereby rearrangements facilitate the build up of linkage disequilibrium in the presence of gene flow. This model is discussed, along with new supporting data from the Solanaceae.

Major ecological transitions in wild sunflowers facilitated by hybridization.

Hybridization is frequent in many organismal groups, but its role in adaptation is poorly understood. In sunflowers, species found in the most extreme habitats are ancient hybrids, and new gene combinations generated by hybridization are speculated to have contributed to ecological divergence. This possibility was tested through phenotypic and genomic comparisons of ancient and synthetic hybrids. Most trait differences in ancient hybrids could be recreated by complementary gene action in synthetic hybrids and were favored by selection. The same combinations of parental chromosomal segments required to generate extreme phenotypes in synthetic hybrids also occurred in ancient hybrids. Thus, hybridization facilitated ecological divergence in sunflowers.

Rice genomes: a grainy view of future evolutionary research.

The draft genome sequences from two subspecies of rice are powerful new tools for gene discovery in the grasses. Genome-wide comparisons of gene content and order will also shed new light on evolutionary processes.