Diagnostic and therapeutic strategies for colorectal tumor with positive muscle-retracting sign

Objectives

Endoscopic submucosal dissection (ESD) for colorectal tumors with positive muscle-retracting (MR) sign often results in incomplete resection or discontinuation owing to the difficulty of submucosal dissection. The present study aimed to evaluate the usefulness of endoscopic ultrasonography (EUS) in diagnosing the MR sign and performing ESD using the pocket-creation method (PCM).

Methods

Thirty-six cases of colorectal tumors with positive MR sign during ESD between January 2015 and December 2021 were retrospectively reviewed. Cases were divided into two groups: 1) the conventional method (CM) group, comprising 29 cases, and 2) the PCM group with seven cases, in which preoperative EUS and ESD using PCM were performed. Treatment outcomes were compared between the groups. The diagnostic yield of EUS for the MR sign was evaluated among large sessile tumors >20 mm in which preoperative EUS was performed.

Results

Histologic diagnosis was adenoma or Tis carcinoma in 12 cases (33%), T1 carcinoma in 18 cases (50%), T2 carcinoma in four cases (11%), and unevaluable in two cases (6%). The sensitivity and specificity of the EUS-MR sign for large sessile tumors were 87.5% and 83.3%, respectively. ESD was achieved in all cases in the PCM group, although it was discontinued in eight cases (28%) in the CM group. There were significant differences between the PCM and CM groups in en bloc resection (100% vs. 48%, p = 0.013) and R0 resection rates (71% vs. 31%, p = 0.049).

Conclusion

The MR sign can be predicted by preoperative EUS, and ESD using PCM allows en bloc resection.

Can underwater endoscopic mucosal resection be an alternative to conventional endoscopic mucosal resection for superficial non-ampullary duodenal epithelial tumors?

Objectives

Underwater endoscopic mucosal resection (UEMR) is a simpler procedure for superficial non-ampullary duodenal epithelial tumors (SNADET) than conventional endoscopic mucosal resection (cEMR). This study aimed to evaluate whether cEMR can be substituted by UEMR for SNADET in terms of effectiveness, safety, and learning curve.

Methods

A total of 157 consecutive patients with 203 SNADETs ≤20 mm in diameter, including 107 lesions resected by cEMR and 96 lesions resected by UEMR, between January 2019 and May 2023, were retrospectively recruited. The treatment outcomes were compared between the cEMR and UEMR groups. The risk factors for incomplete resection by UEMR were analyzed using univariate and multivariate analyses. Lesions in the UEMR group were divided chronologically into five periods; thereafter, the en bloc resection rate and procedure time were compared.

Results

No significant differences existed between the cEMR and UEMR groups in the mean procedure time (3.9 min vs. 3.6 min, p = 0.1380) or en bloc resection rate (91% vs. 94%, p = 0.4138). No perforation was observed in either group. Tumor size was an independent risk factor for incomplete resection using UEMR (p < 0.01). The history of biopsy was not associated with incomplete resection using UEMR. The en bloc resection rate of UEMR was 100% (20/20) in the first period and ranged from 90% to 100% over all periods.

Conclusion

UEMR is safe and effective for SNADET ≤20 mm, regardless of a history of biopsy, and is easy to learn. Thus, UEMR can serve as an alternative to cEMR.

Verrucous gastritis-like lesion in intramucosal Helicobacter pylori-uninfected signet ring cell carcinoma with poorly differentiated adenocarcinoma

In Japan, accessible Helicobacter pylori (Hp) eradication therapy is associated with an increase in the prevalence of gastric cancers (GCs) in Hp uninfected stomachs. Signet ring cell carcinoma (SRCC) is the most common of these GCs. Intramucosal SRCC with poorly differentiated adenocarcinoma (PDA) occurring in Hp uninfected gastric mucosa is rare; furthermore, many Hp uninfected pure SRCCs exhibit discoloration and flat or slightly depressed lesions, and morphological elevation is relatively rare. We report a case of intramucosal SRCC with PDA with an elevated, verrucous gastritis-like lesion in a 57-year-old male patient. In the present case, the PDA area showed dense tumor cell growth and coexisting desmoplastic and fibrotic reactions. Histopathology and immunohistochemical staining identified extensive fibromuscular obliteration with smooth muscle bundles extending from the muscularis mucosa into the lamina propria. The patient underwent curative endoscopic submucosal dissection. The reporting and analysis of such rare cases may lead to a better understanding of the characteristics of advanced Hp uninfected GCs.

Clinicopathological and genomic features of superficial esophageal squamous cell carcinomas in nondrinker, nonsmoker females

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is sometimes detected in non-drinker and non-smoker females who are considered to have very low risk of ESCC development in daily practice. This study examined the clinicopathological and genomic characteristics of ESCCs in females with no history of drinking and smoking.

METHODS

The sample comprised 118 ESCC lesions occurring in 95 female patients who underwent endoscopic submucosal dissection at our department between January 2008 and December 2019. The patients were categorized into two groups: 51 lesions in 49 patients with no history of drinking and smoking (nondrinker/nonsmoker [NDNS] group) and 69 lesions in 45 patients with a history of drinking or smoking (drinker/smoker [DS] group). We analyzed the differences in clinicopathological and cancerous genomic characteristics between the groups. Significant genomic alterations were validated using immunohistochemistry.

RESULTS

Multiple logistic regression revealed that older age, fewer multiple Lugol-voiding lesions (LVLs), and reflux esophagitis (RE) were independently associated with the occurrence of ESCCs in the NDNS group. ESCC lesions in the NDNS group were predominantly located in the mid-thoracic esophagus, posterior wall side, with 0-IIa, the aspect ratio of the lesion >2 (vertical/horizontal), and endoscopic keratinization. Genetic analysis showed that CDKN2A driver alterations were significantly more frequent and KMT2D alterations were significantly less frequent in the NDNS group than in the DS group. KMT2D alterations were strongly correlated with immunostaining.

CONCLUSION

Older nondrinker, nonsmoker females with RE and fewer multiple LVLs may develop longitudinal 0-IIa ESCC with keratinization of the posterior wall of the mid-thoracic esophagus. ESCCs in nondrinker, nonsmoker females had fewer KMT2D alterations and more CDKN2A alterations, which may be a biomarker for treatment.

Gel immersion EMR of small-bowel inflammatory fibroid polyp using double-balloon endoscopy

Video 1A case of an inflammatory fibroid polyp of the ileum that was safely resected using gel immersion EMR with double-balloon endoscopy.

Predictive factors for esophageal stenosis in patients receiving prophylactic steroid therapy after endoscopic submucosal dissection for esophageal squamous cell carcinoma

BACKGROUND

Methods to prevent esophageal stenosis (ES) after endoscopic submucosal dissection (ESD) for superficial esophageal squamous cell carcinoma (ESCC) have received increasing attention. Although steroid administration is a prophylactic treatment, the risk factors for ES during prophylactic steroid therapy remain unknown. Therefore, this study aimed to retrospectively evaluate the risk factors for refractory ES in patients administered prophylactic steroids after ESD for ESCC.

METHODS

Among 795 patients with ESCC (854 lesions), 180 patients (211 lesions) administered local triamcinolone acetonide (TrA) and/or oral prednisolone were recruited for this study. We compared the total number of endoscopic balloon dilatation (EBD) procedures performed for post-ESD ES and clinical findings (tumor size, ESD history or chemoradiation therapy [CRT], entire circumferential resection, muscle layer damage, supplemental oral prednisolone administration, EBD with TrA injection, and additional CRT) between patients with refractory and non-refractory ES. EBD was continued until dysphagia resolved. We categorized cases requiring ≥ 8 EBD procedures as refractory postoperative stenosis and divided the lesions into two groups.

RESULTS

Multivariate logistic regression analysis revealed that factors such as ESD history, CRT history, tumor size, and entire circumferential resection were independently associated with the development of refractory ES. The withdrawal rates of EBD at 3 years were 96.1% (52/53) and 58.5% (39/59) in the non-refractory and refractory groups, respectively.

CONCLUSIONS

Our data suggest that entire circumferential resection and CRT history are risk factors for refractory post-ESD ES in ESCC, even with prophylactic steroid administration.

Comparison of clinical utility of deep learning-based systems for small-bowel capsule endoscopy reading

BACKGROUND AND AIM

Convolutional neural network (CNN) systems that automatically detect abnormalities from small-bowel capsule endoscopy (SBCE) images are still experimental, and no studies have directly compared the clinical usefulness of different systems. We compared endoscopist readings using an existing and a novel CNN system in a real-world SBCE setting.

METHODS

Thirty-six complete SBCE videos, including 43 abnormal lesions (18 mucosal breaks, 8 angioectasia, and 17 protruding lesions), were retrospectively prepared. Three reading processes were compared: (A) endoscopist readings without CNN screening, (B) endoscopist readings after an existing CNN screening, and (C) endoscopist readings after a novel CNN screening.

RESULTS

The mean number of small-bowel images was 14 747 per patient. Among these images, existing and novel CNN systems automatically captured 24.3% and 9.4% of the images, respectively. In this process, both systems extracted all 43 abnormal lesions. Next, we focused on the clinical usefulness. The detection rates of abnormalities by trainee endoscopists were not significantly different across the three processes: A, 77%; B, 67%; and C, 79%. The mean reading time of the trainees was the shortest during process C (10.1 min per patient), followed by processes B (23.1 min per patient) and A (33.6 min per patient). The mean psychological stress score while reading videos (scale, 1-5) was the lowest in process C (1.8) but was not significantly different between processes B (2.8) and A (3.2).

CONCLUSIONS

Our novel CNN system significantly reduced endoscopist reading time and psychological stress while maintaining the detectability of abnormalities. CNN performance directly affects clinical utility and should be carefully assessed.

Assessment of maxillary sinus fluid volume for postmortem diagnosis of drowning

INTRODUCTION

Drowning is a comprehensive and exclusive diagnosis at autopsy. Autopsy findings such as pleural effusion and waterlogged lungs contribute to the diagnosis. Herein, we aim to reveal the practical usefulness and postmortem changes of the maxillary sinus fluid volume to diagnose drowning.

METHODS

We evaluated 52 drowning and 59 nondrowning cases. The maxillary sinus fluid volume was measured using a computed tomography (CT) scan, and pleural effusion volume and lung weight were manually measured at autopsy. The utility of these three indices for diagnosing drowning and its postmortem changes was evaluated.

RESULTS

The maxillary sinus fluid volume was significantly higher in drowning cases than in other external causes and cardiovascular death cases. Receiver operating characteristic curve analysis revealed that a total maxillary sinus fluid volume >1.04 mL more usefully indicated drowning (odds ratio, 8.19) than a total pleural effusion volume >175 mL (odds ratio, 7.23) and a total lung weight >829 g (odds ratio, 2.29). The combination of maxillary sinus fluid volume and pleural effusion volume more effectively predicted drowning than one index alone. Moreover, the maxillary sinus fluid volume was less influenced by the postmortem interval than the other two indices up to a week after death.

CONCLUSION

Maxillary sinus fluid volume can be more useful than pleural effusion volume and lung weight with higher sensitivity and odds ratio for diagnosing drowning.

IMPLICATIONS FOR PRACTICE

Fluid accumulation in both the maxillary sinuses strongly predicts drowning in the postmortem imaging.

Long-term outcomes of patients with obscure gastrointestinal bleeding after negative capsule endoscopy

BACKGROUND AND AIM

Although small-bowel capsule endoscopy (CE) is widely used for obscure gastrointestinal bleeding (OGIB), long-term outcomes for OGIB patients after negative CE remain unclear. Herein, we defined negative CE as P0 (no bleeding potential) or P1 (less likely to bleed), based on the P classification using CE. We aimed to clarify long-term outcomes of patients with OGIB after negative CE.

METHODS

This single-center observational study enrolled 461 consecutive patients with OGIB who underwent CE from March 2014 to October 2021 and were followed up for >1 year. We examined rebleeding rates and predictive factors.

RESULTS

Two hundred and twenty-four (49%) patients had P0, and 237 (51%) had P1 findings. Rebleeding occurred in 9% and 16% of patients in the P0 and P1 groups, respectively. Two patients in the P0 group and 15 in the P1 group showed rebleeding from the small bowel. The rate of small-bowel rebleeding was significantly lower in the P0 group than that in the P1 group (1% vs 6%, P = 0.002), as was the cumulative rebleeding rate (P = 0.004). In the multivariate analysis, history of endoscopic hemostasis (hazard ratio [HR] = 15.958, 95% confidence interval [CI]:4.950-51.447, P < 0.001) and P1 CE findings (HR = 9.989, 95% CI: 2.077-48.030, P = 0.004) were independently predicted small-bowel rebleeding.

CONCLUSIONS

OGIB with P0 CE findings rarely showed rebleeding from the small bowel. Rebleeding may occur in patients with OGIB. Patients with history of endoscopic hemostasis for small-bowel lesions or P1 CE findings should be followed up intensively.

Disease surveillance evaluation of primary small-bowel follicular lymphoma using capsule endoscopy images based on a deep convolutional neural network (with video)

BACKGROUND AND AIMS

Capsule endoscopy (CE) is useful in evaluating disease surveillance for primary small-bowel follicular lymphoma (FL), but some cases are difficult to evaluate objectively. This study evaluated the usefulness of a deep convolutional neural network (CNN) system using CE images for disease surveillance of primary small-bowel FL.

METHODS

We enrolled 26 consecutive patients with primary small-bowel FL diagnosed between January 2011 and January 2021 who underwent CE before and after a watch-and-wait strategy or chemotherapy. Disease surveillance by the CNN system was evaluated by the percentage of FL-detected images among all CE images of the small-bowel mucosa.

RESULTS

Eighteen cases (69%) were managed with a watch-and-wait approach, and 8 cases (31%) were treated with chemotherapy. Among the 18 cases managed with the watch-and-wait approach, the outcome of lesion evaluation by the CNN system was almost the same in 13 cases (72%), aggravation in 4 (22%), and improvement in 1 (6%). Among the 8 cases treated with chemotherapy, the outcome of lesion evaluation by the CNN system was improvement in 5 cases (63%), almost the same in 2 (25%), and aggravation in 1 (12%). The physician and CNN system reported similar results regarding disease surveillance evaluation in 23 of 26 cases (88%), whereas a discrepancy between the 2 was found in the remaining 3 cases (12%), attributed to poor small-bowel cleansing level.

CONCLUSIONS

Disease surveillance evaluation of primary small-bowel FL using CE images by the developed CNN system was useful under the condition of excellent small-bowel cleansing level.

Indications for Dental Floss Clip Traction During Gastric Endoscopic Submucosal Dissection by Less-Experienced Endoscopists

PURPOSE

Dental floss clip (DFC) traction-assisted endoscopic submucosal dissection (ESD) is widely performed owing to its simplicity. This study aimed to clarify the appropriate indications for the DFC traction method in early gastric cancer when ESD is performed by less-experienced endoscopists.

METHODS AND METHODS

We retrospectively analyzed 1,014 consecutive patients who had undergone gastric ESD performed by less-experienced endoscopists between January 2015 and December 2020. Gastric ESD was performed without DFC in all cases before December 2017 [DFC (-) group, 376 cases], and ESD was performed with DFC in all cases after January 2018 [DFC (+) group, 436 cases]. The procedure time and rates of en bloc resection, complete resection, and adverse events of the groups were compared.

RESULTS

The procedure time did not differ significantly between the 2 groups. However, when comparing lesions >20 mm, the procedure time in the DFC (+) group was significantly shorter than that in the DFC (-) group (95±46 vs. 75±31, P<0.01). The procedure time for lesions located in the greater curvature of the upper or middle stomach and lesions >20 mm located in the lesser curvature side of the stomach in the DFC (+) group was significantly shorter than that in the DFC (-) group.

CONCLUSIONS

The indications for DFC during gastric ESD by less-experienced endoscopists include lesions located in the greater curvature of the upper or middle stomach, and lesions >20 mm located in the lesser curvature of the stomach.

Endoscopic findings suggestive of a high risk of non-radical cure after definitive chemoradiotherapy for cT1bN0M0 esophageal squamous cell carcinoma

BACKGROUND

Definitive chemoradiotherapy (DCRT) is a curative treatment option for cT1bN0M0 esophageal squamous cell carcinoma (ESCC); however, local residual disease and recurrence after complete remission may occur. We aimed to identify endoscopic findings associated with the risk of non-radical cure (local remnant or recurrence) after DCRT for cT1bN0M0 ESCC.

METHODS

We retrospectively analyzed 40 consecutive patients with cT1bN0M0 ESCC who had undergone DCRT between January 2007 and December 2017. We examined the endoscopic findings in patients with residual or recurrent (RR) disease (RR group) and those without RR disease [non-RR (NRR) group] after DCRT. We also evaluated outcomes after DCRT for each endoscopic finding.

RESULTS

There were 10 patients in the RR group and 30 patients in the NRR group. The RR group had a significantly larger tumor size and a higher proportion of lesions with type 0-I. The 5-year relapse-free survival rate was significantly lower in type 0-I and in the presence of B3 vessels. Endoscopic findings in 15 patients with cT1bN0M0 ESCC, type 0-I, who underwent DCRT revealed significantly more reddish lesions in the RR group compared to the NRR group.

CONCLUSIONS

cT1bN0M0 ESCC large size, with B3 vessels, and type 0-I has a high risk of non-radical cure after DCRT, especially the reddish type 0-I, which may need to be considered for treatment similar to advanced cancer, including surgery with preoperative DCRT.

Efficacy of the specialized scissor-type knife for gastric endoscopic submucosal dissection: a propensity score matched retrospective study

Background and study aims  Prevention of bleeding and perforation during gastric endoscopic submucosal dissection (ESD) is important. Scissor-type knives can accurately grasp and incise the targeted tissue using electrosurgical currents, thereby eliminating unexpected incisions. The SB Knife GX, a scissor-type knife specialized for gastric ESD, was released in June 2016 in Japan. The aim of the present study was to evaluate the efficacy and safety of gastric ESD using the SB Knife GX. Patients and methods  A total of 716 patients who underwent gastric ESD at Hiroshima University Hospital between July 2016 and December 2020 were retrospectively reviewed. From these, 671 patients underwent ESD using the IT Knife 2 (IT-2 group), while 45 underwent ESD using an SB Knife GX (SB-GX group). After propensity score matching, the procedure time, specimen size, en bloc and complete resection rates, and intraoperative bleeding, delayed bleeding, and perforation rates were evaluated. Results  No significant differences were observed in mean procedure time (SB-GX group: 115 ± 165 min; IT-2 group: 95 ± 61 min; P  = 0.82) and en bloc and complete resection rates between the two groups. Intraoperative bleeding rates were significantly lower in the SB-GX group than in the IT-2 group (18 % vs. 40 %; P  = 0.01), and there were no differences in delayed bleeding (4 % vs. 4 %) or perforation (0 % vs. 4 %) between the two groups. Conclusions  The SB Knife GX was proven to be useful for control of intraoperative bleeding during gastric ESD, although the procedure time tended to be longer.

Predictive factors for the progression of primary localized stage small-bowel follicular lymphoma

BACKGROUND

Primary small-bowel follicular lymphoma (FL) is mainly diagnosed as a duodenal lesion during esophagogastroduodenoscopy. Recently, with the widespread use of small-bowel endoscopy, FL in the jejunum and ileum has been detected. Most patients with small-bowel FL are diagnosed at the localized stage, and a watch-and-wait policy is used. However, the predictive factors for the progression of small-bowel FL have not been clarified. This study retrospectively examined the predictive factors for the progression of primary localized stage small-bowel FL based on clinicopathological and endoscopic findings.

METHODS

We enrolled 60 consecutive patients with primary small-bowel FL diagnosed at two tertiary hospitals between January 2005 and December 2020, with localized stage, low grade, and low tumor burden with the watch-and-wait policy. We examined the predictive factors for progression according to the clinicopathological and endoscopic findings. Endoscopic findings were focused on the color tone, circumferential location of follicular lesions (circumference ≥ 1/2 or < 1/2), fusion of follicular lesions (fusion [ +] or [ -]), and protruded lesions (≥ 6 mm or < 6 mm).

RESULTS

Progressive disease was observed in 12 (20%) patients (mean observation period, 76.4 ± 55.4 months). In the multivariate analysis, "circumference ≥ 1/2" and "fusion (+)" were significant predictive factors for progression. According to the Kaplan-Meier analysis, progression-free survival was significantly shorter in the "circumference ≥ 1/2" and/or "fusion (+)" group than in the "circumference < 1/2" and "fusion ( -)" group.

CONCLUSIONS

Endoscopic findings of "circumference ≥ 1/2" and "fusion (+)" were significant predictive factors for the progression of primary localized stage small-bowel FL.

Diagnostic yield of proximal jejunal lesions with third-generation capsule endoscopy

Objectives

Capsule endoscopy (CE) has been shown to have poor diagnostic performance when the capsule passes quickly through the small bowel, especially the proximal jejunum. This study aimed to evaluate the diagnostic yield of proximal jejunal lesions with third-generation CE technology.

Methods

We retrospectively examined 138 consecutive patients, 76 (55.0%) of whom were men. The patients' median age was 70 years, and proximal jejunal lesions were detected by CE and/or double-balloon endoscopy at Hiroshima University Hospital between January 2011 and June 2021. We analyzed the diagnostic accuracy of CE for proximal jejunal lesions and compared the characteristics of the discrepancy between the use of CE and double-balloon endoscopy with Pillcam SB 2 (SB2) and Pillcam SB 3 (SB3).

Results

SB2 and SB3 were used in 48 (35%) and 90 (65%) patients, respectively. There was no difference in baseline characteristics between these groups. Small-bowel lesions in the proximal jejunum comprised 75 tumors (54%), 50 vascular lesions (36%), and 13 inflammatory lesions (9%). The diagnostic rate was significantly higher in the SB3 group than in the SB2 group for tumors (91% vs. 72%, p < 0.05) and vascular lesions (97% vs. 69%, p < 0.01). For vascular lesions, in particular, the diagnostic rate of angioectasia improved in the SB3 group (100%) compared with that in the SB2 group (69%).

Conclusions

SB3 use improved the detection of proximal jejunal tumors and vascular lesions compared with SB2 use.

Efficacy of single-balloon overtube for endoscopic submucosal dissection in the proximal colon: A propensity score-matched analysis

OBJECTIVES

A single-balloon overtube (SBO) can improve poor scope operability during colonic endoscopic submucosal dissection (ESD). We aimed to evaluate the clinical usefulness of SBO for ESD in the proximal colon and the predictive factors for cases in which SBO is useful.

METHODS

A total of 88 tumors located in the proximal colon resected by balloon-assisted ESD (BA-ESD) using SBO and 461 tumors resected by conventional ESD (C-ESD) between June 2015 and November 2020 were considered. Seventy-eight tumors each in the BA-ESD and C-ESD groups were matched by propensity score matching. ESD outcomes were compared between the groups, and a decision tree analysis was performed to explore the predictive factors for cases in which SBO is useful.

RESULTS

There were no significant differences between the groups in the major outcomes such as en bloc resection rate (95% vs. 99%, p = 0.17), R0 resection rate (92% vs. 96%, p = 0.30), mean dissection speed (16 mm²/min vs. 16 mm²/min, p = 0.53), and intraoperative perforation rate (5% vs. 6%, p = 0.73). Even when considering cases with poor preoperative scope operability, there were no significant differences between the groups. Comparison of tumors ≥40 mm in diameter between the groups confirmed that the intraoperative perforation rate was significantly lower in the BA-ESD group than in the C-ESD group (0% vs. 24%, p = 0.0188).

CONCLUSION

SBO is useful for ESD of tumors ≥40 mm in diameter in the proximal colon to prevent intraoperative perforation, which usually has a long procedure time.

Characteristics and Treatment Outcomes of Small-bowel Angioectasia in Systemic Sclerosis Patients: A Retrospective Observational Study

Objective Systemic sclerosis (SSc) is defined as an autoimmune disease presenting with fibrosis of various organs and vascular endothelial damage. Vascular lesions, including small-bowel angioectasias, are also frequently detected in SSc patients. Polidocanol injection (PDI) is a safe and effective hemostatic treatment for gastrointestinal bleeding. We evaluated the outcomes of PDI for small-bowel angioectasia in SSc patients. Methods We retrospectively evaluated 65 consecutive SSc patients (61 women; mean age, 64.3 years old) who underwent capsule endoscopy (CE) and/or double-balloon endoscopy at Hiroshima University Hospital between April 2012 and December 2019. Patients Patients were stratified according to the presence of small-bowel angioectasia. Among patients who underwent CE during the same period, those with small-bowel angioectasia without concomitant diseases were compared with SSc patients with small-bowel angioectasia. Clinical and endoscopic characteristics, treatment outcomes, and the incidence of metachronous small-bowel angioectasia after PDI were evaluated. Results SSc patients with small-bowel angioectasia exhibited significantly lower hemoglobin levels and a significantly higher incidence of skin telangiectasia than those without small-bowel angioectasia. On a multivariate analysis of the presence of small-bowel angioectasia, anemia and skin telangiectasia were significant independent factors. SSc patients with small-bowel angioectasia included a higher proportion of women and exhibited a significantly higher incidence of metachronous small-bowel angioectasia than X. The characteristics of small-bowel angioectasia and outcomes of PDI were not significantly different between the two groups. No post-treatment rebleeding cases or adverse events were noted. Conclusion CE should be performed for SSc patients with anemia and/or skin telangiectasia. PDI is effective for SSc patients with small-bowel angioectasia.

Capsule endoscopy findings reflect the gastrointestinal conditions of patients with systemic sclerosis

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and various internal organs. However, there is limited knowledge concerning small-bowel lesions. We evaluated the clinical state of patients with SSc according to the capsule endoscopy (CE) findings. Sixty-five consecutive patients with SSc (61 females; mean age, 64.3 years) underwent CE at Hiroshima University Hospital between April 2012 and December 2019. SSc was subclassified into diffuse and limited cutaneous SSc. Among the 65 patients, 55 (51 females; mean age, 64.5 years; diffuse cutaneous SSc, 27 patients) were evaluated for the presence of fibrosis in the gastrointestinal tract by biopsy. Small-bowel lesions were detected in 27 (42%) patients with SSc. Type 1b angioectasia (Yano-Yamamoto classification) was more frequent in limited cutaneous SSc patients (p = 0.0071). The average capsule transit time of the esophagus was significantly longer in diffuse cutaneous SSc patients (p = 0.0418). There were more cases of Type 1a angioectasia in SSc patients without fibrosis. The average capsule transit time of the esophagus was significantly longer in SSc patients with fibrosis. Thus, this study revealed that the frequency of small-bowel angioectasia and gastrointestinal motility in patients with SSc differed depending on SSc subclassification and the presence of fibrosis.

Exacerbation of Portal Hypertensive Enteropathy after Endoscopic Injection Sclerotherapy for Esophageal Varices

INTRODUCTION

Portal hypertensive enteropathy (PHE) is a well-known small-bowel lesion that occurs with liver cirrhosis (LC) and is associated with increased hepatic venous pressure. However, it is unclear how esophageal varices (EV) treatment actually affects PHE. We aimed to analyze the effects of EV treatment on PHE.

METHODS

Among LC patients who underwent capsule endoscopy (CE) more than twice to confirm PHE at our hospital from February 2009 to September 2018, we targeted those with no change in the Child-Pugh classification after EV treatment for the prevention of bleeding. Patients were assigned to groups based on the EV treatment method (endoscopic injection sclerotherapy [EIS] group or endoscopic variceal ligation [EVL] group). We analyzed the PHE findings before and after treatment, and we investigated changes in the collateral vein using computed tomography imaging.

RESULTS

We analyzed 42 LC patients (27 men; mean age, 65.3 years); 20 were in the EIS group and 22 were in the EVL group. Exacerbation of PHE was significantly prevalent in the EIS group (90%) compared to that in the EVL group (50%). CE of PHE showed significantly prevalent exacerbation of villous edema in the EIS group (65%) compared to that in the EVL group (23%). Stenosis or disappearance of the feeding vessel (55%) and exacerbation of the hepatofugal collateral vein (35%) were significantly prevalent in the EIS group.

CONCLUSIONS

EIS exacerbates PHE, especially villous edema, in LC patients with changes in collateral circulation.

Diagnostic Yield of Colon Capsule Endoscopy in Detection of Superficial Colorectal Lesions

BACKGROUND

The efficacy of second-generation PillCam -COLON2 capsule endoscopy (CCE2) in detecting colorectal superficial lesions remains unclear.

OBJECTIVE

We sought to determine the diagnostic yield of CCE2 in the detection of colorectal superficial lesions.

METHODS

We performed CCE2 in 60 consecutive patients between April 2011 and -December 2017. Lesions ≥6 mm in size were detected in 34 patients (25 males, average age: 60.5 years). We performed endoscopic resection and histopathological analysis of all resected lesions within 3 months after CCE2. We considered the optical colonoscopy (OC) findings as the gold standard and evaluated CCE2 sensitivity.

RESULTS

Sixty-seven lesions (≥6 mm) were detected via OC, with 27 colorectal superficial lesions and 40 protruded lesions. CCE2 sensitivity for ≥6-mm-sized, superficial, and protruded lesions was 84, 78, and 88%, respectively. No significant intergroup differences were observed. CCE2 false-negative colorectal superficial lesions accounted for 31% of right-sided colon lesions and 50% of sessile serrated adenomas/polyps (SSA/Ps). The CCE2 false-negative protruded lesions accounted for 17% of right-sided colon lesions.

CONCLUSION

CCE2 sensitivities for colorectal superficial and protruded lesions were not significantly different. However, flat-type SSA/Ps in the right colon, especially when the transit time is fast, have a risk of demonstrating CCE2 false-negative results.

Automatic detection and classification of protruding lesions in wireless capsule endoscopy images based on a deep convolutional neural network

BACKGROUND AND AIMS

Protruding lesions of the small bowel vary in wireless capsule endoscopy (WCE) images, and their automatic detection may be difficult. We aimed to develop and test a deep learning-based system to automatically detect protruding lesions of various types in WCE images.

METHODS

We trained a deep convolutional neural network (CNN), using 30,584 WCE images of protruding lesions from 292 patients. We evaluated CNN performance by calculating the area under the receiver operating characteristic curve (AUC), sensitivity, and specificity, using an independent set of 17,507 test images from 93 patients, including 7507 images of protruding lesions from 73 patients.

RESULTS

The developed CNN analyzed 17,507 images in 530.462 seconds. The AUC for detection of protruding lesions was 0.911 (95% confidence interval [Cl], 0.9069-0.9155). The sensitivity and specificity of the CNN were 90.7% (95% CI, 90.0%-91.4%) and 79.8% (95% CI, 79.0%-80.6%), respectively, at the optimal cut-off value of 0.317 for probability score. In a subgroup analysis of the category of protruding lesions, the sensitivities were 86.5%, 92.0%, 95.8%, 77.0%, and 94.4% for the detection of polyps, nodules, epithelial tumors, submucosal tumors, and venous structures, respectively. In individual patient analyses (n = 73), the detection rate of protruding lesions was 98.6%.

CONCLUSION

We developed and tested a new computer-aided system based on a CNN to automatically detect various protruding lesions in WCE images. Patient-level analyses with larger cohorts and efforts to achieve better diagnostic performance are necessary in further studies.

Automatic detection of blood content in capsule endoscopy images based on a deep convolutional neural network

BACKGROUND AND AIM

Detecting blood content in the gastrointestinal tract is one of the crucial applications of capsule endoscopy (CE). The suspected blood indicator (SBI) is a conventional tool used to automatically tag images depicting possible bleeding in the reading system. We aim to develop a deep learning-based system to detect blood content in images and compare its performance with that of the SBI.

METHODS

We trained a deep convolutional neural network (CNN) system, using 27 847 CE images (6503 images depicting blood content from 29 patients and 21 344 images of normal mucosa from 12 patients). We assessed its performance by calculating the area under the receiver operating characteristic curve (ROC-AUC) and its sensitivity, specificity, and accuracy, using an independent test set of 10 208 small-bowel images (208 images depicting blood content and 10 000 images of normal mucosa). The performance of the CNN was compared with that of the SBI, in individual image analysis, using the same test set.

RESULTS

The AUC for the detection of blood content was 0.9998. The sensitivity, specificity, and accuracy of the CNN were 96.63%, 99.96%, and 99.89%, respectively, at a cut-off value of 0.5 for the probability score, which were significantly higher than those of the SBI (76.92%, 99.82%, and 99.35%, respectively). The trained CNN required 250 s to evaluate 10 208 test images.

CONCLUSIONS

We developed and tested the CNN-based detection system for blood content in CE images. This system has the potential to outperform the SBI system, and the patient-level analyses on larger studies are required.

Clinical usefulness of a deep learning-based system as the first screening on small-bowel capsule endoscopy reading

BACKGROUND AND AIM

To examine whether our convolutional neural network (CNN) system based on deep learning can reduce the reading time of endoscopists without oversight of abnormalities in the capsule-endoscopy reading process.

METHODS

Twenty videos of the entire small-bowel capsule endoscopy procedure were prepared, each of which included 0-5 lesions of small-bowel mucosal breaks (erosions or ulcerations). At another institute, two reading processes were compared: (A) endoscopist-alone readings and (B) endoscopist readings after the first screening by the proposed CNN. In process B, endoscopists read only images detected by CNN. Two experts and four trainees independently read 20 videos each (10 for process A and 10 for process B). Outcomes were reading time and detection rate of mucosal breaks by endoscopists. Gold standard was findings at the original institute by two experts.

RESULTS

Mean reading time of small-bowel sections by endoscopists was significantly shorter during process B (expert, 3.1 min; trainee, 5.2 min) compared to process A (expert, 12.2 min; trainee, 20.7 min) (P < 0.001). For 37 mucosal breaks, detection rate by endoscopists did not significantly decrease in process B (expert, 87%; trainee, 55%) compared to process A (expert, 84%; trainee, 47%). Experts detected all eight large lesions (>5 mm), but trainees could not, even when supported by the CNN.

CONCLUSIONS

Our CNN-based system for capsule endoscopy videos reduced the reading time of endoscopists without decreasing the detection rate of mucosal breaks. However, the reading level of endoscopists should be considered when using the system.

Artificial intelligence using a convolutional neural network for automatic detection of small-bowel angioectasia in capsule endoscopy images

BACKGROUND AND AIM

Although small-bowel angioectasia is reported as the most common cause of bleeding in patients and frequently diagnosed by capsule endoscopy (CE) in patients with obscure gastrointestinal bleeding, a computer-aided detection method has not been established. We developed an artificial intelligence system with deep learning that can automatically detect small-bowel angioectasia in CE images.

METHODS

We trained a deep convolutional neural network (CNN) system based on Single Shot Multibox Detector using 2237 CE images of angioectasia. We assessed its diagnostic accuracy by calculating the area under the receiver operating characteristic curve (ROC-AUC), sensitivity, specificity, positive predictive value, and negative predictive value using an independent test set of 10 488 small-bowel images, including 488 images of small-bowel angioectasia.

RESULTS

The AUC to detect angioectasia was 0.998. Sensitivity, specificity, positive predictive value, and negative predictive value of CNN were 98.8%, 98.4%, 75.4%, and 99.9%, respectively, at a cut-off value of 0.36 for the probability score.

CONCLUSIONS

We developed and validated a new system based on CNN to automatically detect angioectasia in CE images. This may be well applicable to daily clinical practice to reduce the burden of physicians as well as to reduce oversight.

The Clinical Usefulness of the PillCam Progress Indicator for Route Selection in Double Balloon Endoscopy

Objective The utility of capsule endoscopy (CE) findings in the route selection for double balloon endoscopy (DBE) has not been adequately discussed. The PillCam Progress Indicator in the RAPID 6.5 software program graphically demonstrates the progress of the capsule endoscope through the small-bowel. This study aimed to clarify the usefulness of the PillCam Progress Indicator in choosing the initial DBE route. Methods We retrospectively examined 50 consecutive patients with 50 target lesions detected on both CE and DBE at Hiroshima University Hospital from January 2011 to February 2018. In this study, we selected antegrade DBE on the basis of % Capsule Progress <50% as a clinical trial. The association between the PillCam Progress Indicator data and the DBE route to the target lesion was analyzed. Results The target lesion was reached via the initial DBE route in 96% (48/50) of cases. The cutoff values for selecting an antegrade route for DBE were 50% for % Capsule Progress and 42% for % SB Time. At the cutoff value, the sensitivity, specificity, and positive and negative predictive values for route selection were 100%, 91%, 93%, and 100% for % Capsule Progress and 96%, 91%, 93%, and 95% for % SB Time. Conclusion The PillCam Progress Indicator was useful for determining the appropriate initial DBE route.

Subjective Evaluation of Denture Adhesives: A Multicenter Randomized Controlled Trial

INTRODUCTION

Many reports show that denture adhesives improve the retention and stability of dentures. However, few randomized controlled trials have examined the effects of denture adhesives.

OBJECTIVE

This 10-center randomized controlled trial with parallel groups involving 200 edentulous patients wearing complete dentures aimed to evaluate the effects of short-term use of cream and powder denture adhesives.

METHODS

Patients were allocated into 2 cream- and powder-type adhesive groups and 1 control group. Intervention groups were treated with the 2 adhesives (1 each), and the control group received saline solution. Adhesive or control was applied to the denture-mucosal surface for 4 d, and data at baseline and after day 4 of intervention (i.e., 8 meals) were obtained. Patient satisfaction was evaluated with a 100-mm visual analog scale. Oral health-related quality of life was measured with the Japanese version of the Oral Health Impact Profile for Edentulous Patients. Perceived chewing ability was evaluated by a questionnaire regarding ease of chewing and swallowing food. Between-group comparisons were performed with Kruskal-Wallis tests with the Mann-Whitney U test adjusted by Bonferroni correction. Within-group comparisons of pre- and postintervention measurements were performed with the Wilcoxon signed-rank test. Intention-to-treat analysis was also performed.

RESULTS

Between-group comparisons showed no significant differences for general satisfaction or Oral Health Impact Profile for Edentulous Patients. However, significant differences in satisfaction with various denture functions with cream- and powder-type adhesives were seen in pre- and postintervention comparisons (P < 0.05). Significant differences were also observed for perceived chewing ability of hard foods (P < 0.05).

CONCLUSION

These results suggest that although denture adhesives do not invariably improve denture function, they do affect subjective evaluations and possibly chewing of hard foods. Therefore, the effects of denture adhesive use are insufficient to resolve any fundamental dissatisfaction with dentures ( ClinicalTrials.gov NCT01712802 ).

KNOWLEDGE TRANSFER STATEMENT

The results of this study suggest that denture adhesives should be applied under certain conditions; however, an appropriate diagnosis is important before application. These practice-based data provide information to establish evidence-based guidelines for applying denture adhesives.

Automatic detection of erosions and ulcerations in wireless capsule endoscopy images based on a deep convolutional neural network

BACKGROUND AND AIMS

Although erosions and ulcerations are the most common small-bowel abnormalities found on wireless capsule endoscopy (WCE), a computer-aided detection method has not been established. We aimed to develop an artificial intelligence system with deep learning to automatically detect erosions and ulcerations in WCE images.

METHODS

We trained a deep convolutional neural network (CNN) system based on a Single Shot Multibox Detector, using 5360 WCE images of erosions and ulcerations. We assessed its performance by calculating the area under the receiver operating characteristic curve and its sensitivity, specificity, and accuracy using an independent test set of 10,440 small-bowel images including 440 images of erosions and ulcerations.

RESULTS

The trained CNN required 233 seconds to evaluate 10,440 test images. The area under the curve for the detection of erosions and ulcerations was 0.958 (95% confidence interval [CI], 0.947-0.968). The sensitivity, specificity, and accuracy of the CNN were 88.2% (95% CI, 84.8%-91.0%), 90.9% (95% CI, 90.3%-91.4%), and 90.8% (95% CI, 90.2%-91.3%), respectively, at a cut-off value of 0.481 for the probability score.

CONCLUSIONS

We developed and validated a new system based on CNN to automatically detect erosions and ulcerations in WCE images. This may be a crucial step in the development of daily-use diagnostic software for WCE images to help reduce oversights and the burden on physicians.

Management of occult obscure gastrointestinal bleeding patients based on long-term outcomes

BACKGROUND

There is no consensus regarding the management of occult obscure gastrointestinal bleeding (OGIB) patients without a confirmed bleeding source. This study aimed to consider the management of occult OGIB patients based on their long-term outcomes.

METHODS

We retrospectively enrolled 357 consecutive occult OGIB patients (203 men; mean age: 59.7 years) who underwent capsule endoscopy (CE) at Hiroshima University Hospital, Japan and were followed up for more than 12 months (mean follow-up period; 50.2 months). Patients were divided into three groups as follows: Group A consisted of 98 of 157 patients who had positive findings and indication for treatment, Group B consisted of 59 of 157 patients who had positive findings but no indication for treatment, and Group C consisted of 200 patients who had negative small-bowel findings. We examined the rate of positive CE findings, detection rate and details of bleeding sources, overt bleeding rate, the rate of anemia exacerbation, 5-year anemia exacerbation rate, and overall survival rate.

RESULTS

The positive CE findings rate was 44% (157/357) and detection rate of bleeding source was 27% (98/357). The details of Group A were as follows: angioectasia (n = 61), nonspecific ulceration (n = 10), nonsteroidal anti-inflammatory drug-induced ulcer (n = 8), and others (n = 19). The details of Group B were as follows: erythema (n = 31), angioectasia (n = 25), and others (n = 3). There were no patients with overt bleeding in Group B. Although six patients had anemia exacerbation in Group B, they had angioectasia without a bleeding source.

CONCLUSION

The long-term outcomes of occult OGIB patients were good. Occult OGIB patients without bleeding source lesions may not require follow-up CE.

Clinical significance of small-bowel villous edema in patients with liver cirrhosis: A capsule endoscopy study

BACKGROUND AND AIM

The relationship between the presence of villous edema (VE) in portal hypertensive enteropathy and clinical factors remains unclear. The aim of this study was to reveal the clinical factors related to VE in patients with liver cirrhosis (LC), and investigate the clinical significance of VE.

METHODS

Between February 2009 and September 2016, 363 consecutive patients with LC underwent capsule endoscopy for diagnosing portal hypertensive enteropathy at Hiroshima University Hospital. We evaluated the relationship between the presence of VE and patients' clinical characteristics, findings of esophagogastroduodenoscopy and computed tomography, and survival time.

RESULTS

Villous edema was observed in 131 patients (36%), and severe lesions were found in 71 (20%). The presence of VE was significantly greater in patients with Child-Pugh classification B or C, esophageal varices, portal hypertensive gastropathy (PHG), ascites, portal vein thrombosis (PVT), and splenomegaly. In multivariate analysis, Child-Pugh class B or C, esophageal varices, PVT, and splenomegaly were significant predictive factors for the presence of VE. Severe VE was significantly greater in patients with Child-Pugh class B or C, serum albumin level ≤ 3.2 mg/dL, PHG, and PVT. In multivariate analysis, PHG, Child-Pugh class B or C, PVT, were significant predictive factors for severe VE.

CONCLUSIONS

Clinical factors related to portal hypertension were significantly correlated with VE. In particular PVT was correlated with the appearance and exacerbation of VE. Periodic capsule endoscopy in LC patients may lead to early detection of portal hypertension and PVT.

Safety and efficacy of self-expandable metallic stents in malignant small bowel obstructions

In this report, we present 3 cases of malignant small bowel obstruction, treated with palliative care using endoscopic self-expandable metallic stent (SEMS) placement, with the aim to identify the safety and efficacy of this procedure. Baseline patient characteristics, procedure methods, procedure time, technical and clinical success rates, complications, and patient outcomes were obtained. All 3 patients had pancreatic cancer with small bowel strictures. One patient received the SEMS using colonoscopy, while the other 2 patients received SEMS placement via double balloon endoscopy using the through-the-overtube technique. The median procedure time was 104 min. The technical and clinical success rates were 100%. Post-treatment, obstructive symptoms in all patients improved, and a low-residue diet could be tolerated. All stents remained within the patients until their deaths. The median overall survival time (stent patency time) was 76 d. SEMS placement is safe and effective as a palliative treatment for malignant small bowel obstruction.

Quantitative analysis of masticatory activity during unilateral mastication using muscle fMRI

OBJECTIVE

Quantitative analysis of the activities of all masticatory muscles is required to elucidate the mechanism of stomatognathic dysfunction. Electromyography can be used to record the activity of masticatory muscles, but quantification of the overall activity of every masticatory muscle has not been accomplished because of methodological limitations. In this study, we used muscle functional magnetic resonance imaging for simultaneous quantification of the overall activities of the masseter, medial pterygoid and lateral pterygoid muscles during unilateral gum chewing.

METHODS

Seven healthy male volunteers participated in the study. We evaluated changes in the mean proton transverse relaxation time in the bilateral masseter, medial pterygoid and lateral pterygoid muscles before and after unilateral gum chewing, and to quantify the overall activity of these muscles simultaneously during unilateral gum chewing.

RESULTS

After 5 min of chewing, the activity of the ipsilateral masseter was highest among the six muscles, followed by the ipsilateral medial pterygoid, contralateral lateral pterygoid and contralateral masseter muscles.

CONCLUSION

These results affirm the importance of the ipsilateral masseter muscle and quantitatively demonstrate the important contribution of the ipsilateral medial pterygoid and contralateral lateral pterygoid muscles during unilateral mastication.

Tumor immunotherapy targeting WT1 (Wilms’ tumor gene) peptide for bone and soft-tissue sarcomas: A preliminary report

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Background: WT1 (Wilms’ tumor gene) is originally isolated as a tumor-suppressor gene in a subset of Wilms’ tumors, however, recent studies have indicated its oncogenic activity in various types of cancers, and demonstrated that WT1-specific cytotoxic T lymphocytes specifically kill WT1-expressing cancer cells, thus WT1 protein can be a molecular target for cancer immunotherapy as an attractive tumor rejection antigen. However, WT1 expression in human bone and soft-tissue sarcomas has been poorly understood. Methods: 1) The expression levels of WT1 gene were examined in 36 cases of various types of human bone and soft-tissue sarcomas using quantitative RT-PCR method. They included 12 MFH (11 soft-tissue, 1 bone), 9 osteosarcomas, 6 synovial sarcomas, 4 myxoid liposarcomas, 3 MPNST, one each case of angiosarcoma and clear cell sarcoma. 2) Then, we conducted a phase I/II clinical trial of tumor-specific immunotherapy targeting WT1 peptide for various kinds of cancers including 12 patients with locally advanced and/or metastatic sarcoma (bone 2, soft-tissue 10) which showed WT1 expression and HLA -A*2402. Patients were intracutaneously injected with 3.0mg of HLA- A*2402-restricted natural/or modified 9-mer WT1 peptide emulsified with Montanide ISA51 adjuvant weekly. After 12-times injection, clinical response was evaluated by RECIST. Results: 1) 28 (78%) out of 36 cases of various types of bone and soft-tissue sarcomas overexpressed the WT1 gene, and its expression at the protein level was confirmed by immunohistochemical analysis, suggesting a possibility of immunotherapy using WT1 peptide vaccine for sarcomas. 2) The clinical responses included 4 SD and 7 PD with a case of long-standing SD over 1.5 years. One patient discontinued treatment with patient's decision. There were no patients with objective response (PR/CR). Conclusion: The present preliminary study suggested that tumor immunotherapy using WT1 peptide vaccine can be a new treatment strategy for patients with bone and soft-tissue sarcomas.

No significant financial relationships to disclose.

The Wilms’ tumor gene WT1-GFP knock-in mouse reveals the dynamic regulation of WT1 expression in normal and leukemic hematopoiesis

The Wilms' tumor gene WT1 is overexpressed in most of human leukemias regardless of disease subtypes. To characterize the expression pattern of WT1 during normal and neoplastic hematopoiesis, we generated a knock-in reporter green fluorescent protein (GFP) mouse (WT1(GFP/+)) and assayed for WT1 expression in normal and leukemic hematopoietic cells. In normal hematopoietic cells, WT1 was expressed in none of the long-term (LT) hematopoietic stem cells (HSC) and very few (<1%) of the multipotent progenitor cells. In contrast, in murine leukemias induced by acute myeloid leukemia 1 (AML1)/ETO+TEL/PDGFbetaR or BCR/ABL, WT1 was expressed in 40.5 or 38.9% of immature c-kit(+)lin(-)Sca-1(+) (KLS) cells, which contained a subset, but not all, of transplantable leukemic stem cells (LSCs). WT1 expression was minimal in normal fetal liver HSCs and mobilized HSCs, both of which are stimulated for proliferation. In addition, overexpression of WT1 in HSCs did not result in proliferation or expansion of HSCs and their progeny in vivo. Thus, the mechanism by which expansion of WT1-expressing cells occurs in leukemia remains unclear. Nevertheless, our results demonstrate that the WT1(GFP/+) mouse is a powerful tool for analyzing WT1-expressing cells, and they highlight the potential of WT1, as a specific therapeutic target that is expressed in LSCs but not in normal HSCs.

Functional properties and regional differences of human masseter motor units related to three-dimensional bite force

The aim of this study was to estimate numerically the properties of masseter motor units (MUs) in relation to bite force magnitude and direction three-dimensionally and to confirm the hypothesis that the properties differ between different parts of the muscle by means of simultaneous recording of MU activity along with the MU location and three-dimensional (3D) bite force. The MU activity of the right masseter of four healthy men was recorded using a monopolar needle electrode in combination with a surface reference electrode. The location of the needle electrode was estimated stereotactically with the aid of magnetic resonance images and a reference plate. The magnitude and direction of the bite force was recorded with a custom-made 3D bite force transducer. The recorded bite force was displayed on a signal processor, which enabled the participant to adjust the direction and magnitude of the force. The activities of 65 masseter MUs were recorded. Each MU had specific ranges of bite force magnitude and direction (firing range: FR) and an optimum direction for recruitment (minimum firing threshold: MFT). There was a significant negative correlation between MFT and FR width. There were functional differences in MU properties between the superficial and deep masseter and between the superficial layer and deep layer in the superficial masseter. These results indicate that the contribution of human masseter motor units to bite force production is heterogeneous within the muscle.