Normal small bowel wall characteristics on MR enterography

Single-cell atlas of the small intestine throughout the human lifespan demonstrates unique features of fetal immune cells

Proper development of mucosal immunity is critical for human health. Over the past decade, it has become evident that in humans, this process begins in utero. However, there are limited data on the unique features and functions of fetal mucosal immune cells. To address this gap, we integrated several single-cell ribonucleic acid sequencing datasets of the human small intestine (SI) to create an SI transcriptional atlas throughout the human life span, ranging from the first trimester to adulthood, with a focus on immune cells. Fetal SI displayed a complex immune landscape comprising innate and adaptive immune cells that exhibited distinct transcriptional programs from postnatal samples, especially compared with pediatric and adult samples. We identified shifts in myeloid populations across gestation and progression of memory T-cell states throughout the human lifespan. In particular, there was a marked shift of memory T cells from those with stem-like properties in the fetal samples to fully differentiated cells with a high expression of activation and effector function genes in adult samples, with neonatal samples containing both features. Finally, we demonstrate that the SI developmental atlas can be used to elucidate improper trajectories linked to mucosal diseases by implicating developmental abnormalities underlying necrotizing enterocolitis, a severe intestinal complication of prematurity. Collectively, our data provide valuable resources and important insights into intestinal immunity that will facilitate regenerative medicine and disease understanding.

The robotic-assisted free jejunal flap for neovaginal canal creation in gender-affirming vaginoplasties

INTRODUCTION

One of the biggest challenges with gender-affirming vaginoplasty was the creation of a long-lasting, durable, patent, and self-lubricating neovaginal canal that allowed for spontaneous, pain-free sexual intercourse. The jejunum was a durable, physiologic, and intestinal option to create the neovaginal canal that minimizes the adverse effects of skin graft, peritoneal, and colonic vaginoplasties. Free jejunal vaginoplasties had been performed in cis females for congenital genitourinary anomalies like Mullerian agenesis or after gynecologic-oncologic surgery but had yet to be reported for gender-affirming vaginoplasties. The purpose of this report was to present a technique for a physiologic, intestinal, gender-affirming vaginoplasty without the disadvantages of colonic vaginoplasties.

PATIENTS AND METHODS

This report presented six patients, all natal males who identified as female, undergoing robotic-assisted free jejunal flap gender-affirming vaginoplasty. Mean age was 35.8 years (range: 21-66). Mean body mass index was 33.2 kg/m2 (range: 28.0-41.0). The proximal aspect of the neovaginal canal was created intra-abdominally by elevating peritoneal flaps from the posterior bladder wall to be reflected downward into the external neovaginal canal. The jejunal flap was harvested. The greater saphenous vein was harvested to create an arteriovenous loop between the flap vessels and the recipient femoral artery in an end-to-side fashion and a branch of the femoral vein. The jejunal flap was passed intra-abdominally through the groin incision and then trans-peritoneally into the neovaginal canal. The jejunal segment was inset to the proximal peritoneal flaps and the distal inverted penoscrotal skin of the neovaginal introitus.

RESULTS

Mean length of the harvest jejunal segment was 19.2 cm (range: 15-20). Mean time to ambulation, foley removal, and first vaginal dilation were 3.3 (range: 3-4), 4.0 (range: 3-5), and 4.5 days (range: 4-6), respectively. By a mean follow-up duration of 8.0 months (range: 1-14), mean vaginal depth and diameter were 7.0 and 1.3 cm (range: 1.0-1.5), respectively. Two (33.3%) patients experienced postoperative complications, including groin hematoma (n = 1, 16.7%) and reoperation for correction of dehiscence of the jejunal flap to the vaginal introitus (n = 1, 16.7%).

CONCLUSION

Gender-affirming surgeons should consider a free vascularized segment of jejunum as an option to line the neovaginal canal in the correct patients.

Matrix metalloproteinases in intestinal fibrosis

Intestinal fibrosis is a common complication in patients with inflammatory bowel disease [IBD], in particular Crohn's disease [CD]. Unfortunately, at present intestinal fibrosis is not yet preventable, and cannot be treated by interventions other than surgical removal. Intestinal fibrosis is characterized by excessive accumulation of extracellular matrix [ECM], which is caused by activated fibroblasts and smooth muscle cells. Accumulation of ECM results from an imbalanced production and degradation of ECM. ECM degradation is mainly performed by matrix metalloproteinases [MMPs], enzymes that are counteracted by tissue inhibitors of MMPs [TIMPs]. In IBD patients, MMP activity [together with other protease activities] is increased. At the same time, CD patients have a generally lower MMP activity compared to ulcerative colitis patients, who usually do not develop intestinal strictures or fibrosis. The exact regulation and role[s] of these MMPs in fibrosis are far from understood. Here, we review the current literature about ECM remodelling by MMPs in intestinal fibrosis and their potential role as biomarkers for disease progression or druggable targets.

Gastrointestinal thickness, duration, and leak pressure of five intestinal anastomosis techniques in cats

OBJECTIVE

To compare time to construct completion and resistance to leakage for five intestinal anastomosis techniques in cats and to report normal feline gastrointestinal thickness.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Grossly normal intestinal segments (n = 120) from 10 fresh cat cadavers.

METHODS

A total of 8 cm segments of fresh feline cadaveric intestine were collected, and mural thickness was recorded. Segments were randomly allocated between a control group (n = 20 segments) and five treatment groups (20 segments/group with 2 segments/construct = 10 constructs per group): (1) hand-sewn anastomosis - simple interrupted (HSA-SI), (2) hand-sewn anastomosis - simple continuous (HSA-SC), (3) functional end-to-end stapled anastomosis (FEESA), (4) functional end-to-end stapled anastomosis with oversew (FEESA-O), (5) skin stapled anastomosis (SS). Time to construct completion, leakage location, initial leak pressure (ILP), and maximum intraluminal pressure (MIP) were compared.

RESULTS

Mean mural thickness ± SD (mm) for the stomach, duodenum, jejunum, and ileum were 1.66 ± 0.28, 2.05 ± 0.18, 2.28 ± 0.30, and 2.11 ± 0.39, respectively. ILPs (mean ± SD) for HSA-SI (165 ± 122 mmHg), HSA-SC (149 ± 83), FEESA-O (63 ± 25, FEESA (84 ± 59), SS (77 ± 56), and control segments (>500) were compared. There was no statistically significant difference in ILP (p > .08) or MIP (p > .084) between any treatment groups. Nonoversewn FEESAs were 2.4 times faster to perform compared to oversewn FEESA and SS groups, and 4.7 times faster than HSA (p < .001).

CONCLUSION

All anastomosis techniques provide resistance to leakage that is supraphysiological to that of the normal maximum intraluminal pressure. HSA take longer to complete than stapled anastomoses.

CLINICAL SIGNIFICANCE

All anastomotic techniques may be appropriate in cats. Hand-sewn anastomoses result in a longer surgical time.

Real-time multi-contrast magnetic particle imaging for the detection of gastrointestinal bleeding

Gastrointestinal bleeding, as a potentially life-threatening condition, is typically diagnosed by radiation-based imaging modalities like computed tomography or more invasively catheter-based angiography. Endoscopy enables examination of the upper gastrointestinal tract and the colon but not of the entire small bowel. Magnetic Particle Imaging (MPI) enables non-invasive, volumetric imaging without ionizing radiation. The aim of this study was to evaluate the feasibility of detecting gastrointestinal bleeding by single- and multi-contrast MPI using human-sized organs. A 3D-printed small bowel phantom and porcine small bowel specimens were prepared with a defect within the bowel wall as the source of a bleeding. For multi-contrast MPI, the bowel lumen was filled with an intestinal tracer representing an orally administered tracer. MPI was performed to evaluate the fluid exchange between the vascular compartment of the bowel wall and the lumen while a blood pool tracer was applied. Leakage of the blood pool tracer was observed to the bowel lumen. Multi-contrast MPI enabled co-registration of both tracers at the same location within the bowel lumen indicating gastrointestinal bleeding. Single- and multi-contrast MPI are feasible to visualize gastrointestinal bleeding. Therefore, MPI might emerge as a useful tool for radiation-free detection of bleeding within the entire gastrointestinal tract.

Not Only Length Matters! Impact of the Ileal Width on the Capacity of the Orthotopic Neobladder: The AADAPT Formula Tested on the Animal Model

Background

The capacity of a given shape of an orthotopic ileal neobladder (ONB) varies significantly, although the same length of preterminal ileum is utilised.

Objective

To investigate the variability of the human ileal width and to create a mathematical formula that calculates its impact on the neobladder capacity.

Design setting and participants

During 50 consecutive cases of robotic pelvic surgery, a segment of preterminal ileum was identified and the width was measured. A mathematical formula was created to calculate, for a given ileal length and width, the neobladder capacity and, for a given ileal width and neobladder capacity, the length of the (pre)terminal ileum to harvest. The accuracy of our model was tested on 28 pouches created by swine ileum.

Outcome measurements and statistical analysis

The interindividual variability of the ileal width and its impact on the ileal neobladder capacity was investigated.

Results and limitations

The mean hemicircumference of the human distal ileum is 2.43 ± 0.39 cm (range 2-3.5 cm). According to our geometric model and as confirmed in the swine model, an increase of 1 cm in ileal width increases the neobladder capacity by 85%. The Pearson correlation coefficient reported a strong positive relationship between the formula-calculated and effective volumes of the pouch (r = 0.97). Moreover, for the same target capacity, 1 cm of difference in the ileal width implies harvesting 20 cm less ileum. A lack of testing on humans and application only to spheroidal neobladders are the main limits.

Conclusions

The ileal width impacts the capacity of the ONB. For a given type of ONB, no standard length of ileum should be harvested; instead, the length should be tailored to the width of the ileum for a given patient. Clinical studies are required to confirm our model.

Patient summary

We demonstrated the variability of the ileal width among humans, and we provided a mathematical formula tested on swine that evaluates the impact of the ileal width on the capacity of the orthotopic ileal neobladder.

Small Bowel Imaging from Stepchild of Roentgenology to MR Enterography: Part I: Guidance in Performing and Observing Normal and Abnormal Imaging Findings

MRE has become a standard imaging test for evaluating patients with small bowel pathology, but the indications, interpretation of imaging findings, methodology, and appropriate use must be standardized and widely known. Several signs of small bowel damage in inflammatory and non-inflammatory small bowel pathology include strictures, abscess, inflammatory activity, sinus tract, wall edema, fistula, mucosal lesions, and mesentery fat hypertrophy, all of which are widely and accurately explained by MRE. MRE is a non-invasive modality that accurately assesses the intra-luminal, parietal, and extra-luminal small bowel. The differential MRE appearance allows us to distinguish between different small bowel pathologies, such as neoplastic and non-neoplastic small bowel diseases. The purpose of this paper is to present the MRE technique, as well as the interpretation of imaging findings, through the approach of a rigorous stepwise methodology.

Comparison between traumatic and atraumatic over-the-scope clips in patients with duodenal ulcer bleeding: a retrospective analysis with propensity score-based matching

BACKGROUND AND AIMS

Over-the-scope clips (OTSCs) substantially improved the endoscopic armamentarium for the treatment of severe GI bleeding and can potentially overcome limitations of standard clips. Data indicate a superiority of OTSCs in hemostasis as first- and second-line therapy. However, the impact of the OTSC designs, in particular the traumatic (-t) or atraumatic (-a) type, in duodenal ulcer bleeding has not been analyzed so far.

METHODS

This was a retrospective analysis of a prospective collected database from 2009 to 2020 of 6 German endoscopic centers. All patients who underwent emergency endoscopy and were treated using an OTSC for duodenal ulcer bleeding were included. OTSC-t and OTSC-a patients were compared by the Fisher exact test, χ2 test, or Mann-Whitney U test as appropriate. A propensity score-based 1:1 matching was performed to obtain equal distribution of baseline characteristics in both groups.

RESULTS

The entire cohort comprised 173 patients (93 OTSC-a, 80 OTSC-t). Age, gender, anticoagulant therapy, Rockall score, and treatment regimen had similar distributions in the 2 groups. However, the OTSC-t group showed significantly more active bleeding ulcers (Forrest Ia/b). Matching identified 132 patients (66 in both groups) with comparable baseline characteristics. Initial bleeding hemostasis (OTSC-a, 90.9%; OTSC-t, 87.9%; P = .82) and 72-hour mortality (OTSC-a, 4.5%; OTSC-t, 6.0%; P > .99) were not significantly different, but the OTSC-t group revealed a clearly higher rate of recurrent bleeding (34.9% vs 7.6%, P < .001) and necessity of red blood cell transfusions (5.1 ± 3.4 vs 2.5 ± 2.4 concentrates, P < .001).

CONCLUSIONS

For OTSC use, the OTSC-a should be the preferred option for duodenal ulcer bleeding.

Organization of the human intestine at single-cell resolution

The intestine is a complex organ that promotes digestion, extracts nutrients, participates in immune surveillance, maintains critical symbiotic relationships with microbiota and affects overall health1. The intesting has a length of over nine metres, along which there are differences in structure and function2. The localization of individual cell types, cell type development trajectories and detailed cell transcriptional programs probably drive these differences in function. Here, to better understand these differences, we evaluated the organization of single cells using multiplexed imaging and single-nucleus RNA and open chromatin assays across eight different intestinal sites from nine donors. Through systematic analyses, we find cell compositions that differ substantially across regions of the intestine and demonstrate the complexity of epithelial subtypes, and find that the same cell types are organized into distinct neighbourhoods and communities, highlighting distinct immunological niches that are present in the intestine. We also map gene regulatory differences in these cells that are suggestive of a regulatory differentiation cascade, and associate intestinal disease heritability with specific cell types. These results describe the complexity of the cell composition, regulation and organization for this organ, and serve as an important reference map for understanding human biology and disease.

Estimation of glucose rate of appearance in portal vein circulation using a phenomenological-based model

The joint work of the stomach and the small intestine plays a fundamental role in human digestion. In the stomach, food is turned into a semi-fluid mixture that is slowly released into the small intestine, where most enzymatic reactions occur, and nutrients are absorbed as they become available. This whole process is closely related to glucose homeostasis, mainly because of the appearance of glucose in the portal system and the energetic expenditure of the process itself. The current phenomenological-based model describes such effects of the digestive process on blood glucose concentration. It considers enzymatic and mechanical transformations, energetic expenditure, and the impact of macro-nutrients, fiber, and water on overall digestion and glucose absorption. The model estimates the rate of glucose appearance in the portal vein and is intended to be further integrated into existing models for other human organs and used in model-based systems such as an artificial pancreas with automated insulin delivery.

Repository Describing the Anatomical, Physiological, and Biological Changes in an Obese Population to Inform Physiologically Based Pharmacokinetic Models

Background

Obesity is associated with physiological changes that can affect drug pharmacokinetics. Obese individuals are underrepresented in clinical trials, leading to a lack of evidence-based dosing recommendations for many drugs. Physiologically based pharmacokinetic (PBPK) modelling can overcome this limitation but necessitates a detailed description of the population characteristics under investigation.

Objective

The purpose of this study was to develop and verify a repository of the current anatomical, physiological, and biological data of obese individuals, including population variability, to inform a PBPK framework.

Methods

A systematic literature search was performed to collate anatomical, physiological, and biological parameters for obese individuals. Multiple regression analyses were used to derive mathematical equations describing the continuous effect of body mass index (BMI) within the range 18.5–60 kg/m² on system parameters.

Results

In total, 209 studies were included in the database. The literature reported mostly BMI-related changes in organ weight, whereas data on blood flow and biological parameters (i.e. enzyme abundance) were sparse, and hence physiologically plausible assumptions were made when needed. The developed obese population was implemented in Matlab^® and the predicted system parameters obtained from 1000 virtual individuals were in agreement with observed data from an independent validation obese population. Our analysis indicates that a threefold increase in BMI, from 20 to 60 kg/m², leads to an increase in cardiac output (50%), liver weight (100%), kidney weight (60%), both the kidney and liver absolute blood flows (50%), and in total adipose blood flow (160%).

Conclusion

The developed repository provides an updated description of a population with a BMI from 18.5 to 60 kg/m² using continuous physiological changes and their variability for each system parameter. It is a tool that can be implemented in PBPK models to simulate drug pharmacokinetics in obese individuals.

Biomechanical characterization of the small intestine to simulate gastrointestinal tract chyme propulsion

Regular intestinal motility is essential to guarantee complete digestive function. The coordinative action and integrity of the smooth muscle layers in the small intestine's wall are critical for mixing and propelling the luminal content. However, some patients present gastrointestinal limitations which may negatively impact the normal motility of the intestine. These patients have altered mechanical and muscle properties that likely impact chyme propulsion and may pose a daily scenario for long-term complications. To better understand how mechanics affect chyme propulsion, the propulsive capability of the small intestine was examined during a peristaltic wave along the distal direction of the tract. It was assumed that such a wave works as an activation signal, inducing peristaltic contractions in a transversely isotropic hyperelastic model. In this work, the effect on the propulsion mechanics, from an impairment on the muscle contractile ability, typical from patients with systemic sclerosis, and the presence of sores resultant from ulcers was evaluated. The passive properties of the constitutive model were obtained from uniaxial tensile tests from a porcine small intestine, along with both longitudinal and circumferential directions. Our experiments show decreased stiffness in the circumferential direction. Our simulations show decreased propulsion forces in patients in systemic sclerosis and ulcer patients. As these patients may likely need medical intervention, establishing action concerning the impaired propulsion can help to ease the evaluation and treatment of future complications.

Demonstrating the benefits of corrective intraoperative feedback in improving the quality of duodenal hydrogel spacer placement

Purpose

Pancreatic cancer is the fourth leading cause of cancer‐related death with a 10% 5‐year overall survival rate (OS). Radiation therapy (RT) in addition to dose escalation improves the outcome by significantly increasing the OS at 2 and 3 years but is hindered by the toxicity of the duodenum. Our group showed that the insertion of hydrogel spacer reduces duodenal toxicity, but the complex anatomy and the demanding procedure make the benefits highly uncertain. Here, we investigated the feasibility of augmenting the workflow with intraoperative feedback to reduce the adverse effects of the uncertainties.

Materials and Methods

We simulated three scenarios of the virtual spacer for four cadavers with two types of gross tumor volume (GTV) (small and large); first, the ideal injection; second, the nonideal injection that incorporates common spacer placement uncertainties; and third, the corrective injection that uses the simulation result from nonideal injection and is designed to compensate for the effect of uncertainties. We considered two common uncertainties: (1) “Narrowing” is defined as the injection of smaller spacer volume than planned. (2) “Missing part” is defined as failure to inject spacer in the ascending section of the duodenum. A total of 32 stereotactic body radiation therapy (SBRT) plans (33 Gy in 5 fractions) were designed, for four cadavers, two GTV sizes, and two types of uncertainties. The preinjection scenario for each case was compared with three scenarios of virtual spacer placement from the dosimetric and geometric points of view.

Results

We found that the overlapping PTV space with the duodenum is an informative quantity for determining the effective location of the spacer. The ideal spacer distribution reduced the duodenal V33Gy for small and large GTV to less than 0.3 and 0.1cc, from an average of 3.3cc, and 1.2cc for the preinjection scenario. However, spacer placement uncertainties reduced the efficacy of the spacer in sparing the duodenum (duodenal V33Gy: 1.3 and 0.4cc). The separation between duodenum and GTV decreased by an average of 5.3 and 4.6 mm. The corrective feedback can effectively bring back the expected benefits from the ideal location of the spacer (averaged V33Gy of 0.4 and 0.1cc).

Conclusions

An informative feedback metric was introduced and used to mitigate the effect of spacer placement uncertainties and maximize the benefits of the EUS‐guided procedure.

Finite Element-Based Personalized Simulation of Duodenal Hydrogel Spacer: Spacer Location Dependent Duodenal Sparing and a Decision Support System for Spacer-Enabled Pancreatic Cancer Radiation Therapy

Purpose

Pancreatic cancer is the fourth leading cause of cancer-related death, with a very low 5-year overall survival rate (OS). Radiation therapy (RT) together with dose escalation significantly increases the OS at 2 and 3 years. However, dose escalation is very limited due to the proximity of the duodenum. Hydrogel spacers are an effective way to reduce duodenal toxicity, but the complexity of the anatomy and the procedure makes the success and effectiveness of the spacer procedure highly uncertain. To provide a preoperative simulation of hydrogel spacers, we presented a patient-specific spacer simulator algorithm and used it to create a decision support system (DSS) to provide a preoperative optimal spacer location to maximize the spacer benefits.

Materials and Methods

Our study was divided into three phases. In the validation phase, we evaluated the patient-specific spacer simulator algorithm (FEMOSSA) for the duodenal spacer using the dice similarity coefficient (DSC), overlap volume histogram (OVH), and radial nearest neighbor distance (RNND). For the simulation phase, we simulated four virtual spacer scenarios based on the location of the spacer in para-duodenal space. Next, stereotactic body radiation therapy (SBRT) plans were designed and dosimetrically analyzed. Finally, in the prediction phase, using the result of the simulation phase, we created a Bayesian DSS to predict the optimal spacer location and biological effective dose (BED).

Results

A realistic simulation of the spacer was achieved, reflected in a statistically significant increase in average target and duodenal DSC for the simulated spacer. Moreover, the small difference in average mean and 5th-percentile RNNDs (0.5 and 2.1 mm) and OVH thresholds (average of less than 0.75 mm) showed that the simulation attained similar separation as the real spacer. We found a spacer-location-independent decrease in duodenal V20Gy, a highly spacer-location-dependent change in V33Gy, and a strong correlation between L1cc and V33Gy. Finally, the Bayesian DSS predicted the change in BED with a root mean squared error of 3.6 Gys.

Conclusions

A duodenal spacer simulator platform was developed and used to systematically study the dosimetric effect of spacer location. Further, L1cc is an informative anatomical feedback to guide the DSS to indicate the spacer efficacy, optimum location, and expected improvement.

GRAPH-BASED SMALL BOWEL PATH TRACKING WITH CYLINDRICAL CONSTRAINTS

We present a new graph-based method for small bowel path tracking based on cylindrical constraints. A distinctive characteristic of the small bowel compared to other organs is the contact between parts of itself along its course, which makes the path tracking difficult together with the indistinct appearance of the wall. It causes the tracked path to easily cross over the walls when relying on low-level features like the wall detection. To circumvent this, a series of cylinders that are fitted along the course of the small bowel are used to guide the tracking to more reliable directions. It is implemented as soft constraints using a new cost function. The proposed method is evaluated against ground-truth paths that are all connected from start to end of the small bowel for 10 abdominal CT scans. The proposed method showed clear improvements compared to the baseline method in tracking the path without making an error. Improvements of 6.6% and 17.0%, in terms of the tracked length, were observed for two different settings related to the small bowel segmentation.

Experimental and Computational Studies of Peristaltic Flow in a Duodenal Model

We study peristaltic flow in a C-shaped compliant tube representing the first section of the small intestine—the duodenum. A benchtop model comprising of a silicone tube filled with a glycerol-water mixture deformed by a rotating roller was created. Particle image velocimetry (PIV) was used to image flow patterns for deformations approximating conditions in the duodenum (contraction amplitude of 34% and wave speed 13 mm/s). Reversed flow was present underneath the roller with fluid moving opposite to the direction of the peristaltic wave propagation. Deformations of the tube were imaged and used to construct a computational fluid dynamics (CFD) model of flow with moving boundaries. The PIV and CFD vorticity and velocity fields were qualitatively similar. The vorticity field was integrated over the imaging region to compute the total circulation and there was on average a 22% difference in the total circulation between the experimental and numerical results. Higher shear rates were observed with water compared to the higher viscosity fluids. This model is a useful tool to study the effect of digesta properties, anatomical variations, and peristaltic contraction patterns on mixing and transport in the duodenum in health and disease.

Over-the-scope clip-assisted endoscopic full-thickness resection has potential to treat complex nonampullary duodenal lesions: a single-center case series

BACKGROUND AND AIMS

The duodenum is considered a challenging area for the endoscopic resection of lesions. This study aimed to evaluate the efficacy and safety of over-the-scope clip (OTSC)-assisted endoscopic full-thickness resection (EFTR) for complex nonampullary duodenal lesions unsuitable for conventional resection techniques.

METHODS AND PATIENTS

We conducted a retrospective case review of 13 consecutive patients with complex nonampullary duodenal tumors that were unsuitable for conventional resection techniques; these patients underwent EFTR assisted with OTSC at Beijing Friendship Hospital, Capital Medical University from September 2015 to September 2020. The OTSC device was placed, and tumors were resected after the lesions were identified. Data were abstracted for demographics, lesion features, histopathologic diagnoses, technical success rates, complete resection (R0 resection) rates, and complications.

RESULTS

Thirteen patients with duodenal lesions (6 adenomas and 7 submucosal tumors with nonlifting signs, incomplete lifting signs, difficult locations, failed ESD/EMR attempts or suspected origin in the muscularis propria) subjected to EFTR were included. The sizes of all the lesions evaluated by endoscopy were smaller than 20 mm, and most of them (84.6%, 11/13) were smaller than 12 mm. All 13 applications of the clips, endoscopic resection and full-thickness resection were successful (13/13, 100%). Complete resection was achieved in 12 patients (12/13, 92.3%). There were no immediate or delayed complications, including bleeding, infection and perforation.

CONCLUSIONS

OTSC -assisted EFTR appears to be effective and safe for complex nonampullary duodenal lesions smaller than 20 mm (particularly those ≤ 10-12 mm) that are unsuitable for conventional resection techniques.

Tissue stress from laparoscopic grasper use and bowel injury in humans: establishing intraoperative force boundaries

Objectives

We aim to determine what threshold of compressive stress small bowel and colon tissues display evidence of significant tissue trauma during laparoscopic surgery.

Design

This study included 10 small bowel and 10 colon samples from patients undergoing routine gastrointestinal surgery. Each sample was compressed with pressures ranging from 100 kPa to 600 kPa. Two pathologists who were blinded to all study conditions, performed a histological analysis of the tissues. Experimentation: November 2018–February 2019. Analysis: March 2019–May 2020.

Setting

An inner-city trauma and ambulatory hospital with a 40-bed inpatient general surgery unit with a diverse patient population.

Participants

Patients were eligible if their surgery procured healthy tissue margins for experimentation (a convenience sample). 26 patient samples were procured; 6 samples were unusable. 10 colon and 10 small bowel samples were tested for a total of 120 experimental cases. No patients withdrew their consent.

Interventions

A novel device was created to induce compressive “grasps” to simulate those of a laparoscopic grasper. Experimentation was performed ex-vivo, in-vitro. Grasp conditions of 0–600 kPa for a duration of 10 s were used.

Results

Small bowel (10), M:F was 7:3, average age was 54.3 years. Colon (10), M:F was 1:1, average age was 65.2 years. All 20 patients experienced a significant difference (p<0.05) in serosal thickness post-compression at both 500 and 600 kPa for both tissue types. A logistic regression analysis with a sensitivity of 100% and a specificity of 84.6% on a test set of data predicts a safety threshold of 329–330 kPa.

Conclusions

A threshold was discovered that corresponded to both significant serosal thickness change and a positive histological trauma score rating. This “force limit” could be used in novel sensorized laparoscopic tools to avoid intraoperative tissue injury.

Frequency and significance of incidental liver lesions on MR enterography in adult patients

PURPOSE

To evaluate the frequency and significance of incidental liver lesions identified on MR enterography (MRE) examinations to determine if dedicated sequences for liver evaluation are necessary in the routine MRE protocol.

METHODS

A retrospective departmental database search identified 353 adult (212 women and 141 men; mean [±SD] age, 41.4 [17.0] years; range 18.1-91.9 years) MRE examinations performed in 2017. Radiology reports were reviewed for the presence and characterization of liver lesions, follow-up recommendation, and known malignancy. Follow-up cross-sectional imaging reports were reviewed for liver lesion stability. A senior abdominal radiologist with expertise in liver imaging categorized liver lesions as benign, indeterminate, or malignant and re-characterized indeterminate lesions using follow-up imaging as benign or malignant.

RESULTS

Seventy-nine MRE (22.4%) described liver lesions and follow-up imaging was recommended in 4/79 (5.1%). Seventy-six liver lesions (96.2%) were characterized as benign (cysts/hemangiomas) on routine interpretation and expert review. One of these was recommended for follow-up imaging on initial report, which was characterized as hemangioma by expert review. The remaining 3 lesions (3.8%) were characterized as indeterminate both by initial report and expert radiologist review but re-characterized as benign after reviewing follow-up examinations.

CONCLUSION

All incidental liver lesions identified on MRE in our cohort were benign. Therefore, additional sequences evaluating the liver are unnecessary for routine MRE.

Fasted and fed small bowel motility patterns at cine-MRI in chronic intestinal pseudo-obstruction

BACKGROUND

Chronic intestinal pseudo-obstruction (CIPO) is a severe intestinal motility disorder of which the pathophysiology is largely unknown. This study aimed at gaining insight in fasted and fed small bowel motility in CIPO patients using cine-MRI with caloric stimulation.

METHODS

Eight adult patients with manometrically confirmed CIPO were prospectively included. Patients underwent a cine-MRI protocol after an overnight fast, comprising fasting-state scans and scans after ingestion of a meal (Nutridrink, 300 kcal). Small bowel motility was quantified resulting in a motility score in arbitrary units (AU) and visually assessed by three radiologists. Findings were compared with those in 16 healthy volunteers.

KEY RESULTS

Motility scores (median, IQR) in CIPO patients were 0.21 (0.15-0.30) in the fasting state and 0.23 (0.15-0.27) directly postprandially. In healthy volunteers, corresponding motility scores were 0.15 (0.13-0.18) and 0.22 (0.19-0.25), respectively. The postprandial change in motility score was +1% (-19 to +21%) in CIPO and +39% (+23 to +50%) in healthy volunteers (p = 0.001*). Visual analysis revealed increased small bowel contractility in four, normal in two, and decreased in two CIPO patients.

CONCLUSIONS & INFERENCES

Surprisingly, we found hyperactive small bowel motility in half of the CIPO patients, suggestive of uncoordinated motility. A wide variation in motility patterns was observed, both higher, lower, and comparable contractility compared with healthy subjects. No clear postprandial activation was seen in patients. Cine-MRI helps to gain insight in this complex disease and can potentially impact treatment decisions in the future.

Intraductal Tissue Sampling Device Designed for the Biliary Tract

Clinical sampling of tissue that is read by a pathologist is currently the gold standard for making a disease diagnosis, but the few minimally invasive techniques available for small duct biopsies have low sensitivity, increasing the likelihood of false negative diagnoses. We propose a novel biopsy device designed to accurately sample tissue in a biliary stricture under fluoroscopy or endoscopic guidance. The device consists of thin blades organized around the circumference of a cylinder that are deployed into a cutting annulus capable of comprehensively sampling tissue from a stricture. A parametric study of the device performance was done using finite element analysis; this includes the blade deployment under combined axial compression and torsion followed by an axial 'cutting' step. The clinical feasibility of the device is determined by considering maximum deployment forces, the radial expansion achieved and the cutting stiffness. We find practical parameters for the device operation to be an overall length of 10 mm and a diameter of 3.5 mm for a [Formula: see text] blade thickness, which allow the device to be safely deployed with a force of 10N and achieve an expansion over 3x its original diameter. A model device was fabricated with these parameters and a [Formula: see text] thickness out of a NiTi superalloy and tested to validate the performance. The device showed strong agreement with an equivalent numerical model, reaching a peak force within 2% of that predicted numerically and fully recovering after compression to 20% of its length. Clinical and Translational Impact Statement -This pre-clinical research conceptually demonstrates a novel expandable device to biopsy tissue in narrow strictures during an ERCP procedure. It can greatly improve diagnostic tissue yield compared to existing methods.

MRE Evaluation of Intestinal Inflammation: Qualitative and Quantitative Assessment

ABSTRACT

Magnetic resonance enterography (MRE) is a powerful tool for evaluation and management of patients with Crohn disease. Changes of active inflammation of the small bowel can reliably and reproducibly be detected and monitored. Findings indicative of active inflammation include bowel wall thickening, intramural edema and mural hyperenhancement. These changes are most commonly reported qualitatively; however, quantitative indices have also been developed and validated to measure and monitor inflammation both for clinical care and research purposes. This article describes the essential findings of active inflammation on MRE as well as the fundamentals of both qualitative and quantitative assessment and reporting.

Gastrointestinal thickness, duration, and leak pressure of six intestinal anastomoses in dogs

OBJECTIVE

To compare leak pressures and construct completion time of six intestinal anastomoses and report normal canine gastrointestinal thickness.

STUDY DESIGN

Experimental study.

ANIMALS

Grossly normal jejunal segments (n = 140) from 10 fresh canine cadavers.

METHODS

Gastrointestinal thickness was recorded. Eight-centimeter cooled canine cadaveric jejunal segments were randomly assigned to a control group (20 segments) and six treatment groups (20 segments/group [10 constructs/group]): (1) handsewn anastomosis (HSA), (2) functional end-to-end stapled anastomosis (FEESA)-blue thoracoabdominal (TA; FEESA-TAB), (3) FEESA-green TA (FEESA-TAG), (4) FEESA TA-gastrointestinal anastomosis (GIA), (5) FEESA with suture oversew (FEESA-O), and (6) skin staples (SS). Construct assembly time, initial leak pressure (ILP), maximum intraluminal pressure (MIP), and leakage location were compared.

RESULTS

Initial leak pressures (mean ± SD) for control (308.38 ± 115.91 mm Hg), HSA (41.96 ± 15.97), FEESA-TAB (31.71 ± 15.71), FEESA-TAG (27.24 ± 14.11), FEESA-GIA (25.62 ± 11.22), FEESA-O (31.01 ± 17.38), and SS (44.42 ± 28.88) groups were compared. No difference in ILP (P > .24) or MIP (P > .17) was detected between treatment groups. Sutured anastomoses took up to 10 times longer to complete (P = .0025). The stomach, duodenum, jejunum, and ileum mural thicknesses (mean ± SD) were 3.99 ± 0.44 mm, 2.34 ± 0.16, 2.49 ± 0.28, and 2.30 ± 0.31, respectively.

CONCLUSION

The ILP of all anastomoses exceeded maximum intraluminal peristaltic pressures. Stapled anastomoses were faster to complete.

CLINICAL SIGNIFICANCE

All anastomoses may be considered when performing an intestinal resection and anastomosis, with stapled anastomoses resulting in a shorter surgical time. Canine intestinal thickness may warrant use of a larger staple size.

A Review of Normal Intestinal Healing, Intestinal Anastomosis, and the Pathophysiology and Treatment of Intestinal Dehiscence in Foreign Body Obstructions in Dogs

Small intestinal anastomoses are commonly performed in veterinary medicine following resection of diseased or devitalized intestinal tissue. Traditionally, suture has been employed to anastomose intestinal ends. However, use of intestinal staplers has become increasingly popular due to the ability to produce a rapid anastomosis with purported superior healing properties. Under normal conditions, intestinal healing occurs in three phases: inflammatory, proliferative, and maturation. Dehiscence, a devastating consequence of intestinal anastomosis surgery, most often occurs during the inflammatory phase of healing where the biomechanical strength of the anastomosis is almost entirely dependent on the anastomotic technique (suture or staple line). The resulting septic peritonitis is associated with a staggering morbidity rate upwards of 85% secondary to the severe systemic aberrations and financial burden induced by septic peritonitis and requirement of a second surgery, respectively. Intraoperative and postoperative consideration of the multifactorial nature of dehiscence is required for successful patient management to mitigate recurrence. Moreover, intensive postoperative critical care management is necessitated and includes antibiotic and fluid therapy, vasopressor or colloidal support, and monitoring of the patient's fluid balance and cardiovascular status. An understanding of anastomotic techniques and their relation to intestinal healing will facilitate intraoperative decision-making and may minimize the occurrence of postoperative dehiscence.

Reference Values and Repeatability of Transabdominal Ultrasonographic Gastrointestinal Tract Thickness and Motility in Healthy Donkeys (Equus asinus)

The present study aimed to provide reference ranges for the wall thickness and motility pattern of the gastrointestinal tract from a sample of donkeys (Equus asinus) population using B-mode ultrasonography. In the present study, 30 clinically healthy donkeys (Equus asinus) (15 males and 15 females), aged 2-20 year old and weighed 100-280 kg were randomly selected for B-mode ultrasonographic scanning of the abdomen. The wall thickness of the stomach, duodenum, jejunum, left colon, right colon, and cecum was assessed. Moreover, the motility pattern of the duodenum, jejunum, left colon, right colon, and cecum was evaluated over a period of 3 minutes. Abdominal ultrasonographic scanning of the gastrointestinal tract of healthy donkeys explored that the stomach, duodenum, jejunum, left colon, right colon, and cecum could be visualized easily. The wall thickness of the stomach, duodenum, jejunum, left colon, right colon, and cecum was 7.0 ± 0.9 mm, 3.3 ± 1.0 mm, 5.4 ± 0.6 mm, 5.1 ± 0.5 mm, 5.4 ± 0.5 mm, and 5.4 ± 0.6 mm, respectively. The thickest part of the gastrointestinal tract is the stomach, whereas the thinnest part is the duodenum. The motility pattern of the duodenum, jejunum, left colon, right colon, and cecum was 7.7 ± 1.3 contractions/3 minutes, 6.9 ± 1.1 contractions/3 minutes, 4.1 ± 1.2 contractions/3 minutes, 5.5 ± 1.3 contractions/3 minutes, and 4.0 ± 0.8 contractions/3 minutes, respectively. Both the duodenum and jejunum contractions were significantly higher than that of the left colon, right colon, and cecum. This is the first study reporting the reference values for both the wall thickness and motility pattern of the gastrointestinal tract in healthy donkeys (Equus asinus) in Egypt. Good knowledge of these standard and reference values of the wall thickness and motility pattern of gastrointestinal tract structures represents a step in the early diagnosis of the gastrointestinal disorders, including colic in such animal species.

Backwash ileitis in ulcerative colitis: Are there MR enterographic features that distinguish it from Crohn disease?

OBJECTIVE

To reveal the MR enterography (MRE) findings that distinguish backwash ileitis (BWI) from terminal ileitis due to Crohn's disease (CD) and to determine the usability of barium studies manifestations (ileocecal valve (ICV) gaping, terminal ileum dilatation) in MRE for the diagnosis of BWI in ulcerative colitis (UC) patients by pointing at the diagnostic performance of these imaging findings.

SUBJECTS-METHODS

The study population consisted of patients who were diagnosed as ulcerative colitis (UC), and underwent 1.5 T MRI between August 2011 and November 2017 to rule out small bowel involvement. The matched controls were comprised of Crohn's patients examined at the same period. Ileocolonoscopic/ histopathologic findings were accepted as reference standard. Mural/extramural changes in bowel segments, ileocecal valve (ICV) gaping, terminal ileum dilatation, restricted diffusion and anatomical extent of involvement were evaluated. In UC patients, the association between ICV gaping and terminal ileum dilatation and BWI was assessed by χ2 test. The diagnostic accuracy of these two findings in BWI was determined.

RESULTS

Sixty patients were included in the study (30 UC; 30 CD; mean age, 43 years in both groups). Ileocecal valve gaping and terminal ileum dilatation were significantly more frequent among BWI patients (p < 0.001) in UC. Patients with BWI showed a higher rate of pancolitis (88.9%). Median terminal ileum wall thickness was found to be significantly greater in patients with CD (p < 0.001).

CONCLUSION

In patients with definite diagnosis of UC, ileocecal valve gaping and terminal ileum dilatation suggest the development of BWI. However, these findings cannot be use to differentiate cause of terminal ileitis in patients with unconfirmed diagnosis and do not give reliable information about the causative factor of ileitis.

Winged Partially Covered Self-Expandable Metal Stent to Prevent Distal Migration in Malignant Gastric Outlet Obstruction

BACKGROUND

Through-the-scope implantation of self-expandable metal stents can be used for the palliation of malignant gastric outlet obstruction. Although covered stents were developed to prevent tumor ingrowth, often seen with uncovered stents, migration is still a major problem. Especially, surgical treatment is required for some patients if distal migration occurs.

AIMS

To evaluate the usefulness of the newly designed winged stent that was developed to prevent distal stent migration.

METHODS

This was a single-center, single-arm, retrospective study. A total of 63 inoperable cancer patients with symptomatic gastric outlet obstruction were reviewed to evaluate the safety and efficacy of a newly designed partially covered self-expandable metal stent with star-shaped wing flaps at the proximal end to reduce distal stent migration.

RESULTS

Technical and clinical successes were achieved in 100% and 87.3% of patients, respectively. The gastric outlet obstruction scoring system score significantly improved after stent placement (from median 1 to 2, P < 0.001). The median duration of stent patency was 147 days (interquartile range 76-201), and median duration of overall survival was 176 days (interquartile range 79-325). Stent migration was observed in seven patients (11.1%), and restenosis was developed in 12 patients (19.0%). All cases of migration were proximal, and no distal migration was observed. Endoscopic removal of migrated stents was performed successfully in all cases.

CONCLUSIONS

The newly designed winged stent showed feasible efficacy and safety for malignant gastric outlet obstruction. Furthermore, it effectively prevented distal stent migration.

Intestinal fibrosis

Extensive tissue fibrosis is the end-stage process of a number of chronic conditions affecting the gastrointestinal tract, including inflammatory bowel disease (Crohn's disease, ulcerative colitis), ulcerative jejunoileitis, and radiation enteritis. Fibrogenesis is a physiological, reparative process that may become harmful as a consequence of the persistence of a noxious agent, after an excessive duration of the healing process. In this case, after replacement of dead or injured cells, fibrogenesis continues to substitute normal parenchymal tissue with fibrous connective tissue, leading to uncontrolled scar formation and, ultimately, permanent organ damage, loss of function, and/or strictures. Several mechanisms have been implicated in sustaining the fibrogenic process. Despite their obvious etiological and clinical distinctions, most of the above-mentioned fibrotic disorders have in common a persistent inflammatory stimulus which sustains the production of growth factors, proteolytic enzymes, and pro-fibrogenic cytokines that activate both non-immune (i.e., myofibroblasts, fibroblasts) and immune (i.e., monocytes, macrophages, T-cells) cells, the interactions of which are crucial in the progressive tissue remodeling and destroy. Here we summarize the current status of knowledge regarding the mechanisms implicated in gut fibrosis with a clinical approach, also focusing on possible targets of antifibrogenic therapies.

Assessment of normal jejunum with diffusion-weighted imaging on MRE in children

BACKGROUND

Diffusion restriction has been utilized as a marker for bowel inflammation on magnetic resonance enterography (MRE). However, diffusion restriction has been seen in otherwise normal appearing small bowel in patients without active inflammation, with little published data on this subject.

OBJECTIVE

Assess diffusion restriction in normal loops of jejunum and to determine if there is a correlation to luminal distention, age, magnet field strength, slice thickness, and bowel segment location.

MATERIALS AND METHODS

A retrospective analysis of subjects with a normal MRE and clinical work-up was performed. The abdomen was divided into four quadrants. If available, two loops of jejunum were randomly chosen in each quadrant. Two radiologists evaluated the loops of jejunum for distension, wall thickness, enhancement and diffusion restriction. Disagreement was resolved by consensus. Presence of diffusion restriction was correlated with luminal distension, age, magnet field strength, slice thickness and abdominal quadrant.

RESULTS

One hundred ninety-seven loops of jejunum were evaluated in 39 subjects. Fifteen subjects (38.5%) had jejunal loops with diffusion restriction for a total of 28 loops. There was no correlation between diffusion restriction and luminal distension, age, magnet field strength or quadrant location (P>0.05, Pearson chi-squared test or Student's t-tests). Of the 15 subjects with a loop demonstrating diffusion restriction, additional loops with diffusion restriction were found in 40%. There was a very weak trend observed for greater slice thickness in patients with jejunal diffusion restriction (Student's t-test, P=0.10).

CONCLUSION

Jejunal diffusion restriction is a common finding in children with no clinical evidence of bowel pathology, irrespective of patient age, luminal distension, location of bowel loop and magnetic field strength. Further studies may be valuable in assessing the impact of slice thickness on subjective diffusion restriction in the jejunum.

In vivo performance of a visible wavelength optical sensor for monitoring intestinal perfusion and oxygenation

Traumatic injury resulting in hemorrhage is a prevalent cause of death worldwide. The current standard of care for trauma patients is to restore hemostasis by controlling bleeding and administering intravenous volume resuscitation. Adequate resuscitation to restore tissue blood flow and oxygenation is critical within the first hours following admission to assess severity and avoid complications. However, current clinical methods for guiding resuscitation are not sensitive or specific enough to adequately understand the patient condition. To better address the shortcomings of the current methods, an approach to monitor intestinal perfusion and oxygenation using a multiwavelength (470, 560, and 630 nm) optical sensor has been developed based on photoplethysmography and reflectance spectroscopy. Specifically, two sensors were developed using three wavelengths to measure relative changes in the small intestine. Using vessel occlusion, systemic changes in oxygenation input, and induction of hemorrhagic shock, the capabilities and sensitivity of the sensor were explored in vivo. Pulsatile and nonpulsatile components of the red, blue, and green wavelength signals were analyzed for all three protocols (occlusion, systemic oxygenation changes, and shock) and were shown to differentiate perfusion and oxygenation changes in the jejunum. The blue and green signals produced better correlation to perfusion changes during occlusion and shock, while the red and blue signals, using a new correlation algorithm, produced better data for assessing changes in oxygenation induced both systemically and locally during shock. The conventional modulation ratio method was found to be an ineffective measure of oxygenation in the intestine due to noise and an algorithm was developed based on the Pearson correlation coefficient. The method utilized the difference in phase between two different wavelength signals to assess oxygen content. A combination of measures from the three wavelengths provided verification of oxygenation and perfusion states, and showed promise for the development of a clinical monitor.

Endoscopic full-thickness resection of gastric and duodenal subepithelial lesions using a new, flat-based over-the-scope clip

Background

Surgical resection of upper gastrointestinal (GI) subepithelial tumors (SETs) is associated with significant morbidity and mortality. A new over-the-scope (OTS) clip can be used for endoscopic full-thickness resection (eFTR). We aimed to prospectively evaluate feasibility and safety of upper GI eFTR with a new, flat-based OTS clip.

Methods

Consecutive patients with a gastric or duodenal SET < 20 mm were prospectively included. After identification of the lesion, the clip was placed and lesions were resected. Patients were followed for 1 month to assess severe adverse events (SAEs); 3–6 months after eFTR, endoscopy was performed.

Results

eFTR was performed on 13 lesions in 12 patients: 7 gastric and 6 duodenal SETs. Technical success was achieved in 11 cases (85%). In all 11 cases, R0-resection was achieved. In all 6 duodenal cases and in one gastric case, FTR was achieved (64%). One SAE (pain) was observed after eFTR of a gastric SET. After eFTR of duodenal SETs, several SAEs were observed: perforation (n = 1), microperforation (n = 3), and hemorrhage (n = 1). During follow-up endoscopy, the clip was no longer in situ in most patients (7 of 10; 70%).

Conclusions

eFTR with this new flat-based OTS clip is feasible and effective. Although gastric eFTR was safe, eFTR in the duodenum was complicated by (micro)perforation in several patients. Therefore, the design of the clip or the technique of resection needs further refinement to improve safety of resection of SET in thin-walled areas such as the duodenum before being applied in clinical practice.

Dutch trial register: NTR5023.

Electronic supplementary material

The online version of this article (10.1007/s00464-017-5989-8) contains supplementary material, which is available to authorized users.

Mass-forming lesions of the duodenum: A pictorial review

Recent advances in imaging have resulted in marked changes in the investigation of the duodenum, which still remains primarily evaluated with videoendoscopy. However, improvements in computed tomography (CT) and magnetic resonance (MR) imaging have made detection and characterization of duodenal mass-forming abnormalities easier. The goal of this pictorial review was to illustrate the most common conditions of the duodenum that present as mass-forming lesions with a specific emphasis on CT and MR imaging. MR imaging used in conjunction with duodenal distension appears as a second line imaging modality for the characterization of duodenal mass-forming lesions. CT remains the first line imaging modality for the detection and characterization of a wide range of duodenal mass-forming lesions.

In-silico and in-vitro investigation of a photonic monitor for intestinal perfusion and oxygenation

The quantification of visceral organ oxygenation after trauma-related systemic hypovolemia and shock is critical to enable effective resuscitation. In this work, a photoplethysmography-based (PPG) sensor was specifically designed for probing the perfusion and oxygenation condition of intestinal tissue with the ultimate goal to monitor patients post trauma to guide resuscitation. Through Monte Carlo modeling, suitable optofluidic phantoms were determined, the wavelength and separation distance for the sensor was optimized, and sensor performance for the quantification of tissue perfusion and oxygenation was tested on the in-vitro phantom. In particular, the Monte Carlo simulated both a standard block three-layer model and a more realistic model including villi. Measurements were collected on the designed three layer optofluidic phantom and the results taken with the small form factor PPG device showed a marked improvement when using shorter visible wavelengths over the more conventional longer visible wavelengths. Overall, in this work a Monte Carlo model was developed, an optofluidic phantom was built, and a small form factor PPG sensor was developed and characterized using the phantom for perfusion and oxygenation over the visible wavelength range. The results show promise that this small form factor PPG sensor could be used as a future guide to shock-related resuscitation.

Theoretical investigation of transgastric and intraductal approaches for ultrasound-based thermal therapy of the pancreas

Background

The goal of this study was to theoretically investigate the feasibility of intraductal and transgastric approaches to ultrasound-based thermal therapy of pancreatic tumors, and to evaluate possible treatment strategies.

Methods

This study considered ultrasound applicators with 1.2 mm outer diameter tubular transducers, which are inserted into the tissue to be treated by an endoscopic approach, either via insertion through the gastric wall (transgastric) or within the pancreatic duct lumen (intraductal). 8 patient-specific, 3D, transient, biothermal and acoustic finite element models were generated to model hyperthermia (n = 2) and ablation (n = 6), using sectored (210°–270°, n = 4) and 360° (n = 4) transducers for treatment of 3.3–17.0 cm³ tumors in the head (n = 5), body (n = 2), and tail (n = 1) of the pancreas. A parametric study was performed to determine appropriate treatment parameters as a function of tissue attenuation, blood perfusion rates, and distance to sensitive anatomy.

Results

Parametric studies indicated that pancreatic tumors up to 2.5 or 2.7 cm diameter can be ablated within 10 min with the transgastric and intraductal approaches, respectively. Patient-specific simulations demonstrated that 67.1–83.3% of the volumes of four sample 3.3–11.4 cm³ tumors could be ablated within 3–10 min using transgastric or intraductal approaches. 55.3–60.0% of the volume of a large 17.0 cm³ tumor could be ablated using multiple applicator positions within 20–30 min with either transgastric or intraductal approaches. 89.9–94.7% of the volume of two 4.4–11.4 cm³ tumors could be treated with intraductal hyperthermia. Sectored applicators are effective in directing acoustic output away from and preserving sensitive structures. When acoustic energy is directed towards sensitive structures, applicators should be placed at least 13.9–14.8 mm from major vessels like the aorta, 9.4–12.0 mm from other vessels, depending on the vessel size and flow rate, and 14 mm from the duodenum.

Conclusions

This study demonstrated the feasibility of generating shaped or conformal ablative or hyperthermic temperature distributions within pancreatic tumors using transgastric or intraductal ultrasound.

Magnetic resonance enterography: A stepwise interpretation approach and role of imaging in management of adult Crohn's disease

Crohn's disease (CD) is a chronic inflammatory bowel disease that often requires frequent imaging of patients in order to detect active disease and other complications related to disease activity. While endoscopy is the gold standard for diagnosis, it may be contraindicated in some patients and has a limited role in detecting deep submucosal/mesenteric diseases and intra abdominal complications. In recent years, magnetic resonance enterography (MRE) has evolved as a noninvasive, radiation free imaging modality in the evaluation of patients with CD. This review article will focus on role of MRE in imaging patients with CD with emphasis on technical considerations, systematic image interpretation, differential diagnoses, and the role of imaging in deciding treatment options for patients.

Ex vivo motility in the base of the rabbit caecum and its associated structures: an electrophysiological and spatiotemporal analysis

We examined the coordination between contractile events at different sites in the basal portion of the rabbit caecum and its associated structures that were identified by electrophysiological recordings with simultaneous one-dimensional, and a novel two-dimensional, spatiotemporal mapping technique. The findings of this work provide evidence that the caecum and proximal colon/ampulla coli act reflexly to augment colonic outflow when the caecum is distended and mass peristalsis instituted, the action of the latter overriding the inherent rhythm and direction of haustral propagation in the adjacent portion of the proximal colon but not in the terminal ileum. Further, the findings suggest that the action of the sacculus rotundus may result from its distension with chyme by ileal peristalsis and that the subsequent propagation of contraction along the basal wall of the caecum towards the colon may be augmented by this local distension.

Multimodality imaging of diseases of the duodenum

The duodenum is a unique segment of intestine, occupying both intra and extra-peritoneal locations. There is a wide spectrum of abnormalities of the duodenum that range from congenital anomalies to traumatic, inflammatory, and neoplastic entities. The duodenum may be overlooked on cross-sectional imaging due to its location and small size. Duodenal pathologies may, therefore, be missed or wrongly diagnosed. Knowledge about duodenal pathologies and optimal imaging techniques can increase diagnostic yield and permit optimal patient management. Conventionally, the duodenum was evaluated with upper GI studies on fluoroscopy; however, endoluminal evaluation is better performed with endoscopy. Additionally, a broad array of cross-sectional imaging modalities permits comprehensive assessment of the duodenum and surrounding viscera. While endoscopic sonography is increasingly used to locally stage duodenal malignancies, MDCT remains the primary modality widely used in the detection and characterization of duodenal abnormalities. MRI is used as a "problem solving" modality in select conditions. We present a comprehensive review of duodenal abnormalities with an emphasis on accurate diagnosis and management.

PhytobezoarInduced Small Bowel Obstruction in a Young Male with Virgin Abdomen

Phytobezoars are a rare cause of small bowel obstruction. Such cases are most commonly associated with previous abdominal surgery or poor dentition or psychiatric conditions. A 40 year old man with a virgin abdomen and excellent dentition and no underlying psychiatric condition presented with an acute abdomen. CT scan revealed a transition point between dilated proximal loops of small bowel and collapsed distal loops. Exploratory laparotomy revealed a phytobezoar unable to be milked into the cecum and an enterectomy with primary anastamosis was performed without complication. A detailed history revealing several less common predisposing factors for phytobezoars should increase clinical suspicion of a phytobezoarinduced small bowel obstruction in the setting of an acute abdomen. Vigilance in presentations of an acute abdomen improves the usefulness of medical imaging, such as a CT, to detect phytobezoars. Understanding mechanisms of phytobezoar formation helps guide management and may prevent surgery.

Parameterization of small intestinal water volume using PBPK modeling

To facilitate accurate predictions of oral drug disposition, mechanistic absorption models require optimal parameterization. Furthermore, parameters should maintain a biological basis to establish confidence in model predictions. This study will serve to calculate an optimal parameter value for small intestinal water volume (SIWV) using a model-based approach. To evaluate physiologic fidelity, derived volume estimates will be compared to experimentally-based SIWV determinations. A compartmental absorption and transit (CAT) model, created in Matlab-Simulink®, was integrated with a whole-body PBPK model, developed in PK-SIM 5.2®, to provide predictions of systemic drug disposition. SIWV within the CAT model was varied between 52.5mL and 420mL. Simulations incorporating specific SIWV values were compared to pharmacokinetic data from compounds exhibiting solubility induced non-proportional changes in absorption using absolute average fold-error. Correspondingly, data pertaining to oral administration of acyclovir and chlorothiazide were utilized to derive estimates of SIWV. At 400mg, a SIWV of 116mL provided the best estimates of acyclovir plasma concentrations. A similar SIWV was found to best depict the urinary excretion pattern of chlorothiazide at a dose of 100mg. In comparison, experimentally-based estimates of SIWV within adults denote a central tendency between 86 and 167mL. The derived SIWV (116mL) represents the optimal parameter value within the context of the developed CAT model. This result demonstrates the biological basis of the widely utilized CAT model as in vivo SIWV determinations correspond with model-based estimates.

Magnetic resonance enterography in the evaluation of Crohn's disease: a primer for the gastroenterologist

The assessment of disease location, severity, and complications is critical in guiding the choice of Crohn's disease therapy. Cross-sectional imaging studies have therefore had a paramount role in accurately staging Crohn's disease. Traditionally, computed tomography was the test of choice in confirming/excluding strictures, fistulae, and abscesses. Magnetic resonance imaging is now replacing computed tomography because it eliminates radiation risks. This review provides a primer for the gastroenterologist on magnetic resonance enterography in Crohn's disease.

Comparison of 3% sorbitol vs psyllium fibre as oral contrast agents in MR enterography

OBJECTIVE

To compare the degree of small bowel distension achieved by 3% sorbitol, a high osmolarity solution, and a psyllium-based bulk fibre as oral contrast agents (OCAs) in MR enterography (MRE).

METHODS

This retrospective study was approved by our institutional review board. A total of 45 consecutive normal MRE examinations (sorbitol, n = 20; psyllium, n = 25) were reviewed. The patients received either 1.5 l of 3% sorbitol or 2 l of 1.6 g kg(-1) psyllium prior to imaging. Quantitative small bowel distension measurements were taken in five segments: proximal jejunum, distal jejunum, proximal ileum, distal ileum and terminal ileum by two independent radiologists. Distension in these five segments was also qualitatively graded from 0 (very poor) to 4 (excellent) by two additional independent radiologists. Statistical analysis comparing the groups and assessing agreement included intraclass coefficients, Student's t-test and Mann-Whitney U-test.

RESULTS

Small bowel distension was not significantly different in any of the five small bowel segments between the use of sorbitol and psyllium as OCAs in both the qualitative (p = 0.338-0.908) and quantitative assessments (p = 0.083-0.856). The mean bowel distension achieved was 20.1 ± 2.2 mm for sorbitol and 19.8 ± 2.5 mm for psyllium (p = 0.722). Visualization of the ileum was good or excellent in 65% of the examinations in both groups.

CONCLUSION

Sorbitol and psyllium are not significantly different at distending the small bowel and both may be used as OCAs for MRE studies.

ADVANCES IN KNOWLEDGE

This is the first study to directly compare the degree of distension in MRE between these two common, readily available and inexpensive OCAs.

Small Bowel Imaging: Clinical Applications of the Different Imaging Modalities—A Comprehensive Review

In the last years, MR and CT techniques have been optimized for small bowel imaging and are playing an increasing role in the evaluation of small bowel disorders. In comparison to traditional barium fluoroscopic examinations, spatial and temporal resolution is now much more improved partially thanks to modern bowel distending agents. However, there is a global interest in implementing techniques that either reduce or eliminate radiation exposure. This is especially important in patients with chronic diseases such as inflammatory bowel disease who may require multiple studies over a lifetime. Owing to the excellent soft tissue contrast, direct multiplanar imaging capabilities, new ultrafast breath-holding pulse sequences, lack of ionizing radiation, and availability of a variety of oral contrast agents, MR is well suited to play a critical role in the imaging of small bowel disorders.

Prospective evaluation of magnetic resonance enterography for the detection of mesenteric small bowel tumours

PURPOSE

To prospectively evaluate magnetic resonance (MR) enterography for detecting mesenteric small-bowel tumours (MSBTs) and assess the added value of gadolinium-chelate injection.

MATERIAL AND METHODS

Over a 2-year period MR enterography examinations of 75 patients (33 men, 42 women; mean age, 53.8 years; range, 19-85) with suspected MSBT were blindly analysed by two readers for the presence of MSBT. Sensitivities, specificities, predictive positive values (PPVs), negative predictive values (NPVs) and accuracies of MR enterography for the detection of MSBT were calculated on per-patient and per-lesion bases. The McNemar test was used to compare sensitivities and specificities of the unenhanced and gadolinium-enhanced sets of MR enterographies.

RESULTS

Thirty-seven MSBTs were pathologically confirmed in 26 patients. The mean tolerance score of the examinations was 0.7. On a per-patient basis, sensitivity, specificity, PPV, NPV and accuracy for detection of MSBT were 96 % [95 % CI, 89-100 %], 96 % [90-100 %], 93 % [83-100 %], 98 % [94-100 %] and 96 % [92-100 %], respectively. On a per-lesion basis, sensitivity and PPV were 70 % [56-85 %] and 93 % [83-100 %], respectively. Gadolinium injection yielded higher sensitivities on both bases (P = 0.008).

CONCLUSION

MR enterography is an accurate and well-tolerated imaging modality for detecting MSBT. Intravenous administration of gadolinium-chelate improves sensitivity for MSBT detection.

KEY POINTS

• MR enterography accurately detects mesenteric small bowel tumours. • MR enterography is a well-tolerated imaging technique. • Intravenous administration of gadolinium chelate improves sensitivity for detecting small-bowel tumours.