Endoscopic En Bloc Versus Piecemeal Resection of Large Nonpedunculated Colonic Adenomas : A Randomized Comparative Trial.

BACKGROUND: Endoscopic resection of adenomas prevents colorectal cancer, but the optimal technique for larger lesions is controversial. Piecemeal endoscopic mucosal resection (EMR) has a low adverse event (AE) rate but a variable recurrence rate necessitating early follow-up. Endoscopic submucosal dissection (ESD) can reduce recurrence but may increase AEs. OBJECTIVE: To compare ESD and EMR for large colonic adenomas. DESIGN: Participant-masked, parallel-group, superiority, randomized controlled trial. (ClinicalTrials.gov: NCT03962868). SETTING: Multicenter study involving 6 French referral centers from November 2019 to February 2021. PARTICIPANTS: Patients with large (≥25 mm) benign colonic lesions referred for resection. INTERVENTION: The patients were randomly assigned by computer 1:1 (stratification by lesion location and center) to ESD or EMR. MEASUREMENTS: The primary end point was 6-month local recurrence (neoplastic tissue on endoscopic assessment and scar biopsy). The secondary end points were technical failure, en bloc R0 resection, and cumulative AEs. RESULTS: In total, 360 patients were randomly assigned to ESD (n = 178) or EMR (n = 182). In the primary analysis set (n = 318 lesions in 318 patients), recurrence occurred after 1 of 161 ESDs (0.6%) and 8 of 157 EMRs (5.1%) (relative risk, 0.12 [95% CI, 0.01 to 0.96]). No recurrence occurred in R0-resected cases (90%) after ESD. The AEs occurred more often after ESD than EMR (35.6% vs. 24.5%, respectively; relative risk, 1.4 [CI, 1.0 to 2.0]). LIMITATION: Procedures were performed under general anesthesia during hospitalization in accordance with the French health system. CONCLUSION: Compared with EMR, ESD reduces the 6-month recurrence rate, obviating the need for systematic early follow-up colonoscopy at the cost of more AEs. PRIMARY FUNDING SOURCE: French Ministry of Health.

International Consensus Recommendations for Safe Use of LAMS for On- and Off-Label Indications Using a Modified Delphi Process.

INTRODUCTION: The study aimed to develop international consensus recommendations on the safe use of lumen-apposing metal stents (LAMSs) for on- and off-label indications. METHODS: Based on the available literature, statements were formulated and grouped into the following categories: general safety measures, peripancreatic fluid collections, endoscopic ultrasound (EUS)-biliary drainage, EUS-gallbladder drainage, EUS-gastroenterostomy, and gastric access temporary for endoscopy. The evidence level of each statement was determined using the Grading of Recommendations Assessment, Development, and Evaluation methodology.International LAMS experts were invited to participate in a modified Delphi process. When no 80% consensus was reached, the statement was modified based on expert feedback. Statements were rejected if no consensus was reached after the third Delphi round. RESULTS: Fifty-six (93.3%) of 60 formulated statements were accepted, of which 35 (58.3%) in the first round. Consensus was reached on the optimal learning path, preprocedural imaging, the need for airway protection and essential safety measures during the procedure, such as the use of Doppler, and measurement of the distance between the gastrointestinal lumen and the target structure. Specific consensus recommendations were generated for the different LAMS indications, covering, among others, careful patient selection, the preferred size of the LAMS, the need for antibiotics, the preferred anatomic location of the LAMS, the need for coaxial pigtail placement, and the appropriate management of LAMS-related adverse events. DISCUSSION: Through a modified international Delphi process, we developed general and indication-specific experience- and evidence-based recommendations on the safe use of LAMS.

Systematic Resection of the Visible Scar After Incomplete Endoscopic Resection of Rectal Neuroendocrine Tumors.

INTRODUCTION: When initial resection of rectal neuroendocrine tumors (r-NETs) is not R0, persistence of local residue could lead to disease recurrence. This study aimed to evaluate the interest of systematic resection of non-R0 r-NET scars. METHODS: Retrospective analysis of all the consecutive endoscopic revisions and resections of the scar after non-R0 resections of r-NETs. RESULTS: A total of 100 patients were included. Salvage endoscopic procedure using endoscopic submucosal dissection or endoscopic full-thickness resection showed an R0 rate of near 100%. Residual r-NET was found in 43% of cases. DISCUSSION: In case of non-R0 resected r-NET, systematic scar resection by endoscopic full-thickness resection or endoscopic submucosal dissection seems necessary.

Impact of Annual Case Volume on Colorectal Endoscopic Submucosal Dissection Outcomes in a Large Prospective Cohort Study.

INTRODUCTION: The adoption of colorectal endoscopic submucosal dissection (ESD) is still limited in the West. A recent randomized trial showed that ESD is more effective and only slightly riskier than piecemeal endoscopic mucosal resection; reproducibility outside expert centers was questioned. We evaluated the results according to the annual case volume in a multicentric prospective cohort. METHODS: Between September 2019 and September 2022, colorectal ESD was consecutively performed at 13 participating centers classified as low volume (LV), middle volume (MV), and high volume (HV). The main procedural outcomes were assessed. Multivariate and propensity score matching analyses were performed. RESULTS: Three thousand seven hundred seventy ESDs were included. HV centers treated larger and more often colonic lesions than MV and LV centers. En bloc , R0, and curative resection rates were 95.2%, 87.4%, and 83.2%, respectively, and were higher at HV than at MV and LV centers. HV centers also achieved a faster dissection speed. Delayed bleeding and surgery for complications rates were 5.4% and 0.8%, respectively, without significant differences. The perforation rate (overall: 9%) was higher at MV than at LV and HV centers. Lesion characteristics, but not volume center, were independently associated with both R1 resection and perforation. However, after propensity score matching, R0 rates were significantly higher at HV than at LV centers, and perforation rates were significantly higher at MV than at HV centers. DISCUSSION: Colorectal ESD can be successfully implemented in the West, even in nonexpert centers. However, difficult lesions must still be referred to experts.

EUS-guided hepaticojejunostomy in patients with history of total gastrectomy: a multicenter retrospective feasibility study (with video).

BACKGROUND AND AIMS: EUS-guided hepaticogastrostomy (EUS-HGS) is an effective biliary drainage technique for patients with altered anatomy or duodenal strictures. EUS-guided hepaticojejunostomy (EUS-HJS) can be used to create a fistula between the left hepatic duct and the jejunum in patients with a history of total gastrectomy. No specific data on this technique have been published. The aim of this study was to assess the feasibility and safety of EUS-HJS in patients with a history of total gastrectomy. METHODS: This retrospective multicenter study included all adult patients who underwent EUS-HJS at 3 tertiary French centers and 1 tertiary Swiss center between May 2011 and February 2023. The primary outcome was clinical success, which was defined as the disappearance of pruritus, jaundice, and/or cholangitis. An improvement in bilirubin >30% within the first week and/or bilirubin normalization within 1 month after the procedure were also considered indicators of clinical success. Secondary outcomes were technical success, rate of adverse events, need for endoscopic revision, possibility of resuming anticancer treatment, median survival, and technical differences compared with EUS-HGS. RESULTS: Twenty-one patients with history of complete gastrectomy who underwent EUS-HJS were included. Technical success was achieved in 100% of patients (95% confidence interval [CI], 85-100). Clinical success was achieved in 80% of patients (95% CI, 58-92). The incidence of recorded adverse events was 33% (95% CI, 17-55), with cholangitis being the most frequent adverse event. Seven patients (39%) were able to benefit from anticancer treatment after the procedure. Median survival time was 6 months (interquartile range, 1.5-12). CONCLUSIONS: EUS-HJS is an effective and feasible procedure for patients whose anatomy has been altered by total gastrectomy.

Impact of surgery after endoscopically resected high-risk T1 colorectal cancer: results of an emulated target trial.

BACKGROUND AND AIMS: We aimed to compare the long-term outcomes of patients with high-risk T1 colorectal cancer (CRC) resected endoscopically who received either additional surgery or surveillance. METHODS: We used data from routine care to emulate a target trial aimed at comparing 2 strategies after endoscopic resection of high-risk T1 CRC: surgery with lymph node dissection (treatment group) versus surveillance alone (control group). All patients from 14 tertiary centers who underwent an endoscopic resection for high-risk T1 CRC between March 2012 and August 2019 were included. The primary outcome was a composite outcome of cancer recurrence or death at 48 months. RESULTS: Of 197 patients included in the analysis, 107 were categorized in the treatment group and 90 were categorized in the control group. From baseline to 48 months, 4 of 107 patients (3.7%) died in the treatment group and 6 of 90 patients (6.7%) died in the control group. Four of 107 patients (3.7%) in the treatment group experienced a cancer recurrence and 4 of 90 patients (4.4%) in the control group experienced a cancer recurrence. After balancing the baseline covariates by inverse probability of treatment weighting, we found no significant difference in the rate of death and cancer recurrence between patients in the 2 groups (weighted hazard ratio, .95; 95% confidence interval, .52-1.75). CONCLUSIONS: Our study suggests that patients with high-risk T1 CRC initially treated with endoscopic resection may not benefit from additional surgery.

The environmental impact of small-bowel capsule endoscopy.

INTRODUCTION: The environmental impact of endoscopy, including small-bowel capsule endoscopy (SBCE), is a topic of growing attention and concern. This study aimed to evaluate the greenhouse gas (GHG) emissions (kgCO2) generated by an SBCE procedure. METHODS: Life cycle assessment methodology (ISO 14040) was used to evaluate three brands of SBCE device and included emissions generated by patient travel, bowel preparation, capsule examination, and video recording. A survey of 87 physicians and 120 patients was conducted to obtain data on travel, activities undertaken during the procedure, and awareness of environmental impacts. RESULTS: The capsule itself (4 g) accounted for < 6 % of the total product weight. Packaging (43-119 g) accounted for 9 %-97 % of total weight, and included deactivation magnets (5 g [4 %-6 %]) and paper instructions (11-50 g [up to 40 %]). A full SBCE procedure generated approximately 20 kgCO2, with 0.04 kgCO2 (0.2 %) attributable to the capsule itself and 18 kgCO2 (94.7 %) generated by patient travel. Capsule retrieval using a dedicated device would add 0.98 kgCO2 to the carbon footprint. Capsule deconstruction revealed materials (e. g. neodymium) that are prohibited from environmental disposal; 76 % of patients were not aware of the illegal nature of capsule disposal via wastewater, and 63 % would have been willing to retrieve it. The carbon impact of data storage and capsule reading was negligible. CONCLUSION: The carbon footprint of SBCE is mainly determined by patient travel. The capsule device itself has a relatively low carbon footprint. Given that disposal of capsule components via wastewater is illegal, retrieval of the capsule is necessary but would likely be associated with an increase in device-related emissions.

Endoscopic submucosal dissection of appendicular lesions is feasible and safe: a retrospective multicenter study (with video).

BACKGROUND AND AIMS: Endoscopic submucosal dissection (ESD) is challenging for appendicular lesions. We report the outcomes of ESD in this context. METHODS: We collected data of ESD procedures for appendiceal neoplasia in a multicenter prospective registry. Main study endpoints were R0, en-bloc, and curative resection rates and adverse event rate. RESULTS: One hundred twelve patients were included, 47 (42%) with previous appendectomy. Fifty-six (50%) were Toyonaga type 3 lesions (15 [13.4%] postappendectomy). En-bloc and R0 resection rates were 86.6% and 80.4%, respectively, with no significant difference associated with different grades of appendiceal invasion (P = .9 and P = .4, respectively) or previous appendectomy (P = .3 for both). The curative resection rate was 78.6%. Additional surgery was performed in 16 cases (14.3%), including 10 (62.5%) Toyonaga type 3 lesions (P = .04). This included the treatment of 5 cases (4.5%) of delayed perforation and 1 acute appendicitis. CONCLUSIONS: ESD for appendicular lesions is a potentially safer and effective alternative to surgery for a significant proportion of patients.

Diagnostic endoscopic submucosal dissection for colorectal lesions with suspected deep invasion.

BACKGROUND: Endoscopic submucosal dissection (ESD) is potentially a curative treatment for T1 colorectal cancer under certain conditions. The aim of this study was to evaluate the feasibility and effectiveness of ESD for lesions with a suspicion of focal deep invasion. METHODS: In this retrospective multicenter study, consecutive patients with colorectal neoplasia displaying a focal (< 15 mm) deep invasive pattern (FDIP) that were treated by ESD were included. We excluded ulcerated lesions (Paris III), lesions with distant metastasis, and clearly advanced tumors (tumoral strictures). RESULTS: 124 patients benefited from 126 diagnostic dissection attempts for FDIP lesions. Dissection was feasible in 120/126 attempts (95.2 %) and, where possible, the en bloc and R0 resection rates were 95.8 % (115/120) and 76.7 % (92/120), respectively. Thirty-three resections (26.2 %) were for very low risk tumors, so considered curative, and 38 (30.2 %) were for low risk lesions. Noncurative R0 resections were for lesions with lymphatic or vascular invasion (LVI; n = 8), or significant budding (n = 9), and LVI + budding combination (n = 4). CONCLUSION: ESD is feasible and safe for colorectal lesions with an FDIP ≤ 15 mm. It was curative in 26.6 % of patients and could be a valid option for a further 30.6 % of patients with low risk T1 cancers, especially for frail patients with co-morbidities.

Endoscopic resection of early esophageal tumors in patients with cirrhosis or portal hypertension: a multicenter observational study.

BACKGROUND: Liver cirrhosis and esophageal cancer share several risk factors, such as alcohol intake and excess weight. Endoscopic resection is the gold standard treatment for superficial tumors. Portal hypertension and coagulopathy may increase the bleeding risk in these patients. This study aimed to assess the safety and efficacy of endoscopic resection for early esophageal neoplasia in patients with cirrhosis or portal hypertension. METHODS: This retrospective multicenter international study included consecutive patients with cirrhosis or portal hypertension who underwent endoscopic resection in the esophagus from January 2005 to March 2021. RESULTS: 134 lesions in 112 patients were treated, including by endoscopic submucosal dissection in 101 cases (75 %). Most lesions (128/134, 96 %) were in patients with liver cirrhosis, with esophageal varices in 71 procedures. To prevent bleeding, 7 patients received a transjugular intrahepatic portosystemic shunt, 8 underwent endoscopic band ligation (EBL) before resection, 15 received vasoactive drugs, 8 received platelet transfusion, and 9 underwent EBL during the resection procedure. Rates of complete macroscopic resection, en bloc resection, and curative resection were 92 %, 86 %, and 63 %, respectively. Adverse events included 3 perforations, 8 delayed bleedings, 8 sepsis, 6 cirrhosis decompensations within 30 days, and 22 esophageal strictures; none required surgery. In univariate analysis, cap-assisted endoscopic mucosal resection was associated with delayed bleeding (P = 0.01). CONCLUSIONS: In patients with liver cirrhosis or portal hypertension, endoscopic resection of early esophageal neoplasia appeared to be effective and should be considered in expert centers with choice of resection technique, following European Society of Gastrointestinal Endoscopy guidelines to avoid undertreatment.

Use of endoscopic submucosal dissection or full-thickness resection device to treat residual colorectal neoplasia after endoscopic resection: a multicenter historical cohort study.

INTRODUCTION : Residual colorectal neoplasia (RCN) after previous endoscopic mucosal resection is a frequent challenge. Different management techniques are feasible including endoscopic full-thickness resection using the full-thickness resection device (FTRD) system and endoscopic submucosal dissection (ESD). We aimed to compare the efficacy and safety of these two techniques for the treatment of such lesions. METHODS : All consecutive patients with RCN treated either using the FTRD or by ESD were retrospectively included in this multicenter study. The primary outcome was the R0 resection rate, defined as an en bloc resection with histologically tumor-free lateral and deep margins. RESULTS : 275 patients (median age 70 years; 160 men) who underwent 177 ESD and 98 FTRD procedures for RCN were included. R0 resection was achieved in 83.3 % and 77.6 % for ESD and FTRD, respectively (P = 0.25). Lesions treated by ESD were however larger than those treated by FTRD (P < 0.001). The R0 rates for lesions of 20-30 mm were 83.9 % and 57.1 % in the ESD and FTRD groups, respectively, and for lesions of 30-40 mm were 93.6 % and 33.3 %, respectively. On multivariable analysis, ESD procedures were associated with statistically higher en bloc and R0 resection rates after adjustment for lesion size (P = 0.02 and P < 0.001, respectively). The adverse event rate was higher in the ESD group (16.3 % vs. 5.1 %), mostly owing to intraoperative perforations. CONCLUSION: ESD is effective in achieving R0 resection for RCN whatever the size and location of the lesions. When residual lesions are smaller than 20 mm, the FTRD is an effective alternative.

The reversion variant (p.Arg90Leu) at the evolutionarily adaptive p.Arg90 site in CELA3B predisposes to chronic pancreatitis.

A gain-of-function missense variant in the CELA3B gene, p.Arg90Cys (c.268C>T), has recently been reported to cause pancreatitis in an extended pedigree. Herein, we sequenced the CELA3B gene in 644 genetically unexplained French chronic pancreatitis (CP) patients (all unrelated) and 566 controls. No obvious loss-of-function variants were identified. None of the six low-frequency or common missense variants detected showed significant association with CP. Nor did the aggregate rare/very rare missense variants (n = 14) show any significant association with CP. However, p.Arg90Leu (c.269G>T), which was found in four patients but no controls, and affects the same amino acid as p.Arg90Cys, serves to revert p.Arg90 to the human elastase ancestral allele. As p.Arg90Leu has previously been shown to exert a similar functional effect to that of p.Arg90Cys, our findings not only confirm the involvement of CELA3B in the etiology of CP but also pinpoint a new evolutionarily adaptive site in the human genome.

Safety of endoscopic retrograde cholangiopancreatography in the pediatric population: a multicenter study.

INTRODUCTION: The aims of this retrospective multicenter study were to assess the technical success and adverse events of endoscopic retrograde cholangiopancreatography (ERCP) procedures in children in French and Belgian centers. METHODS: All children aged 1 day to 17 years who underwent ERCP between January 2008 and March 2019 in 15 tertiary care hospitals were retrospectively included. RESULTS: 271 children underwent 470 ERCP procedures. Clinical long-term follow-up was available for 72 % of our patients (340/470 procedures). The median age at intervention was 10.9 years. ERCP was therapeutic in 90 % (423/470) and diagnostic in cases of neonatal cholestasis in 10 % of the patients. The most common biliary indication was choledocholithiasis; the most common pancreatic indication was chronic pancreatitis. Biliary cannulation was successful in 92 % of cases (270/294); pancreatic cannulation in 96 % of cases (169/176); and planned therapeutic procedures in 92 % of cases (388/423). The overall complication rate was 19 % (65/340). The most common complication was post-ERCP pancreatitis (PEP) in 12 % of cases (40/340) and sepsis in 5 % (18/340). On univariate analyses, pancreatic stent removal was protective against PEP (odds ratio [OR] 0.1, 95 % confidence interval [CI] 0.01 - 0.75; P = 0.03), and sepsis was associated with history of liver transplantation (OR 7.27, 95 %CI 1.7 - 31.05; P = 0.01). Five patients had post-ERCP hemorrhage and two had intestinal perforation. All complications were managed with supportive medical care. There was no procedure-related mortality. CONCLUSION: Our cohort demonstrates that ERCP can be performed safely with high success rates in many pancreaticobiliary diseases of children. The rate of adverse events was similar to that in previous reports.

Prognostic factors associated with six month mortality of critically ill elderly patients admitted to the intensive care unit with severe acute cholangitis.

BACKGROUND: Little is known about the outcomes of elderly patients admitted to the intensive care unit (ICU) with severe acute cholangitis (SAC). The objectives were to describe the 6-month mortality in patients with SAC ≥75 years and to identify factors associated with this mortality. METHODS: Bi-center retrospective study of critically ill elderly patients with SAC conducted between 2013 and 2017. Demographic and clinical variables of ICU and hospital stays with a 6-month follow-up were analyzed. RESULTS: 85 patients, with a median [Q1-Q3] age of 83 [80-89] years were enrolled of whom 51 (60%) were men. SAC was due to choledocholithiasis in 72 (85%) patients. Median [Q1-Q3] ICU length of stay was 3 [2-6] days. Median [Q1-Q3] admission SAPS II was 50 [42-70]. The ICU and 6-month mortality rates were 18% and 48% respectively. Multivariate analysis showed that malnutrition (OR = 34.5, 95% CI [1.4-817.9]) and a decrease in SOFA score at 48 h (OR by unit 0.7, 95% CI [0.5-0.9]) were associated with higher 6-month mortality. CONCLUSION: In their decision-making process, ICU physicians and hepato-pancreato-biliary surgeons could use these data to estimate the probability of survival of an elderly patient presenting with SAC and to offer time-limited trials of intensive care. TRIAL REGISTRATION: NCT03831529.

Clinical outcome in patients treated with endoscopic submucosal dissection for superficial Barrett's neoplasia.

BACKGROUND AND STUDY AIMS: The role of endoscopic submucosal dissection (ESD) in Barrett's neoplasia is ill-defined, although it might provide a higher curative resection rate and better histologic assessment than endoscopic mucosal resection (EMR). We aimed to assess efficacy, safety, and long-term results of ESD. PATIENTS AND METHODS: A retrospective analysis was done of 75 consecutive patients with Barrett's esophagus who underwent ESD between January 2007 and February 2014. ESD was performed for visible lesions that were multiple, larger than 15 mm, or poorly lifting, or suspected of submucosal infiltration. The primary end point was the rate of curative resection of carcinoma. RESULTS: Median patient age was 68 years (interquartile range [IQR] 61 - 76), median follow-up was 20 months (IQR 8.5 - 37.5), and median maximum specimen diameter was 52.5 mm (IQR 43 - 71). En bloc resection rate was 90 % (66 /73), and rates of curative resection of carcinoma and high grade dysplasia/carcinoma were 85 % (47 /55) and 64 % (42 /66), respectively. G3 differentiation and invasion to greater than pT1m2 were observed in 25 % (14 /55) and 67 % (37 /55) of patients with adenocarcinoma, respectively. There were 5 early ( < 48 hours) adverse events (2 delayed hemorrhages and 3 perforations), all treated endoscopically. No ESD-specific death occurred. Esophageal strictures developed in 60 % of patients, all treated endoscopically. Additional treatment (median sessions 2 [IQR 2 - 3]) for residual Barrett's esophagus were recommended to 62 % (42 /68). At latest follow-up, complete remission of neoplasia and intestinal metaplasia was found in 92 % (54 /59) and 73 % (43 /59) of patients, respectively. CONCLUSION: ESD appears to be safe and effective, with a high rate of curative resection of carcinoma. ESD should be considered for patients with Barrett's neoplasia at risk of incomplete resection or poor pathologic assessment with conventional EMR.

Ampullary tumors: French Intergroup Clinical Practice Guidelines for diagnosis, treatments and follow-up (TNCD, SNFGE, FFCD, UNICANCER, GERCOR, SFCD, SFED, ACHBT, AFC, SFRO, RENAPE, SNFCP, AFEF, SFP, SFR).

BACKGROUND: Management of ampullary tumors (AT) is challenging because of a low level of scientific evidence. This document is a summary of the French intergroup guidelines regarding the management of AT, either adenoma (AA) or carcinoma (AC), published in July 2023, available on the website of the French Society of Gastroenterology (SNFGE) (www.tncd.org). METHODS: A collaborative work was conducted under the auspices of French medical, endoscopic, oncological and surgical societies involved in the management of AT. Recommendations are based on recent literature review and expert opinions and graded in three categories (A, B, C), according to quality of evidence. RESULTS: Accurate diagnosis of AT requires at least duodenoscopy and EUS. All patients should be discussed in multidisciplinary tumor board before treatment. Surveillance may only be proposed for small AA in familial adenomatous polyposis. For AA, endoscopic papillectomy is the preferred option only if R0 resection can be achieved. When not possible, surgical papillectomy should be considered. For AC beyond pT1a N0, pancreaticoduodenectomy is the procedure of choice. Adjuvant monochemotherapy (gemcitabine, 5FU) may be proposed. For aggressive tumors (pT3/T4, pN+, R1, poorly differentiated AC, pancreatobiliary differentiation) with high risk of recurrence, 6 months polychemotherapy (CAPOX/FOLFOX for the intestinal subtype and mFOLFIRINOX for the pancreatobiliary or the mixed subtype) may be a valid alternative. Clinical and radiological follow up is recommended for 5 years. CONCLUSIONS: These guidelines help to homogenize and highlight unmet needs in the management of AA and AC. Each individual case should be discussed by a multidisciplinary team.

Methyl donor deficiency affects small-intestinal differentiation and barrier function in rats.

Dietary methyl donors and their genetic determinants are associated with Crohn's disease risk. We investigated whether a methyl-deficient diet (MDD) may affect development and functions of the small intestine in rat pups from dams subjected to the MDD during gestation and lactation. At 1 month before pregnancy, adult females were fed with either a standard food or a diet without vitamin B12, folate and choline. A global wall hypotrophy was observed in the distal small bowel (MDD animals 0·30 mm v. controls 0·58 mm; P< 0·001) with increased crypt apoptosis (3·37 v. 0·4%; P< 0·001), loss of enterocyte differentiation in the villus and a reduction in intestinal alkaline phosphatase production. Cleaved caspase-3 immunostaining (MDD animals 3·37% v. controls 0·4%, P< 0·001) and the Apostain labelling index showed increased crypt apoptosis (3·5 v. 1·4%; P= 0·018). Decreased proliferation was observed in crypts of the proximal small bowel with a reduced number of minichromosome maintenance 6 (MDD animals 52·83% v. controls 83·17%; P= 0·048) and proliferating cell nuclear antigen-positive cells (46·25 v. 59 %; P= 0·05). This lack of enterocyte differentiation in the distal small bowel was associated with an impaired expression of ß-catenin and a decreased ß-catenin-E-cadherin interaction. The MDD affected the intestinal barrier in the proximal small bowel by decreasing Paneth cell number after immunostaining for lysosyme (MDD animals 8·66% v. controls 21·66%) and by reducing goblet cell number and mucus production after immunostaining for mucin-2 (crypts 8·66 v. 15·33%; villus 7 v. 17%). The MDD has dual effects on the small intestine by producing dramatic effects on enterocyte differentiation and barrier function in rats.