User login
Evolving endpoints and treat-to-target strategies in inflammatory bowel disease (IBD) incorporate a need for more frequent assessments of the disease, including objective measures of inflammation.1,2 Intestinal ultrasound (IUS) is a noninvasive, well-tolerated,3 repeatable, point-of-care (POC) test that is highly sensitive and specific in detection of bowel inflammation, transmural healing,4,5 and response to therapy in both Crohn’s disease (CD) and ulcerative colitis (UC).6-8 As IUS is taking hold in the United States, there is a great need to teach the next generation of gastroenterologists about its value, how to incorporate it into clinical practice, and how to become appropriately trained and maintain competency.
Why incorporate IUS in the United States now?
As IBD management has evolved, so has the appreciation for the value of bedside IUS as a tool that addresses very real needs for the field. Unlike other parts of the world in which ultrasound skills are part of the training curriculum, this has not been the case in internal medicine and gastroenterology training in the United States. In addition, there have been no specific billing codes or clear renumeration processes outlined for IUS,9 nor have there been any local training opportunities. Because of these challenges, it was not until recently that several leaders in IBD in the United States championed the potential of this technology and incorporated it into IBD management. Subsequently, a number of gastroenterologists have been trained and are now leading the effort to disseminate this tool throughout the United States. A consequence of these efforts resulted in support from the Helmsley Charitable Trust (Helmsley) and the creation of the Intestinal Ultrasound Group of the United States and Canada to address the gaps unique to North America as well as to strengthen the quality of IUS research through collaborations across the continent.
What is IUS, and when is it performed?
IUS is a sonographic exam performed by a gastroenterology-trained professional who scans the abdominal wall (and perineum when the rectum and perineal disease is evaluated), using both a convex low-frequency probe and linear high-frequency probe to evaluate the small intestine, colon, and rectum. The bowel is composed of five layers with alternating hyperechoic and hypoechoic layers: the mucosal-lumen interface (not a true part of the bowel wall), deep mucosa, submucosa, muscularis propria, and serosa. (Figure)
The most sensitive parameter for assessment of IBD activity is bowel wall thickness (≤ 3 mm in the small bowel and colon and ≤ 4 mm in the rectum are considered normal in adults).8,10 The second key parameter is the assessment of vascularization, in which presence of hyperemia suggests active disease.11 There are a number of indices to quantify hyperemia, with the most widely used being the Limberg score.12 Additional parameters include assessment of loss of the delineation of the bowel wall layers (loss of stratification signifies active inflammation), increased thickness of the submucosa,13 increased mesenteric fatty proliferation (with increased inflammation, mesenteric fat proliferation will appear as a hyperechoic area surrounding the bowel), lymphadenopathy, bowel strictures, and extramural complications such as fistulae and abscess. Shear wave elastography may be an effective way to differentiate severe fibrotic strictures, but this is an area that requires more investigation.14
IUS has been shown to be an excellent tool in not only assessing disease activity and disease complication (with higher sensitivity than the Harvey-Bradshaw Index, serum C-reactive protein),15 but, unique to IUS, can provide early prediction of response in moderate to severe active UC.6,7 This has also been shown with transperineal ultrasound in patients with UC, with the ability to predict response to therapy as early as 1 week from induction therapy.16 Furthermore, it can be used to assess transmural healing, which has been shown to be associated with improved outcomes in Crohn’s patient, such as lower rates of hospitalizations, surgery, medication escalation, and need for corticosteroids.17 IUS is associated with great patient satisfaction and greater understanding of disease-related symptoms when the patient sees the inflammation of the bowel. (Table)
How can you get trained in IUS?
Training in IUS varies across the globe, from incorporation of IUS into the standard training curriculum to available training programs that can be followed and attended outside of medical training. In the United States, interested gastroenterologists can now be trained by becoming a member of the International Bowel Ultrasound Group (IBUS Group) and applying to the workshops now available. The IBUS Group has developed an IUS-specific training curriculum over the last 16 years, which is comprised of three modules: a 2-day hands-on workshop (Module 1) with final examination of theoretical competency, a preceptorship at an “expert center” with an experienced sonographer for a total of 4 weeks to complete 40 supervised IUS examinations (Module 2), and didactics and a final examination (Module 3). Also with support from Helmsley, the first Module 1 to be offered in the United States was hosted at Mount Sinai Medical Center in New York in 2022, the second was hosted at the University of Chicago in March 2023, and the third is planned to take place at Cedars-Sinai Medical Center in Los Angeles in March 2024.18 With the growing interest and demand for IUS training in the United States, U.S. experts are working to develop new training options that will be less time consuming, scalable, and still provide appropriate training and competency assessment.
How do you integrate IUS into your practice?
The keys to integrating IUS are a section chief or practice manager’s support of a trainee or faculty member for both funding of equipment and protected time for training and building of the program, as well as a permissive environment and collegial relationship with radiology. An ultrasound machine and additional transducers may range in price from $50,000-$120,000. Funding may be a limiting step for many, however. A detailed business plan is imperative to the success and investment of funds in an IUS program. With current billing practices in place that include ”limited abdominal ultrasound” (76705) and “Doppler ultrasound of the abdomen” (93975),19 reimbursement should include a technical fee, professional fee, and if in a hospital-based clinic, a facility fee. IUS pro-fee combined with technical fee is reimbursed at approximately 0.80 relative value units. When possible, the facility fee is included for approximately $800 per IUS visit. For billing and compliance with HIPAA, all billed IUS images must be stored in a durable and accessible format. It is recommended that the images and cine loops be digitally stored to the same or similar platform used by radiologists at the same institution. This requires early communication with the local information technology department for the connection of an ultrasound machine to the storage platform and/or electronic health record. Reporting results should be standardized with unique or otherwise available IUS templates, which also satisfy all billing components.9 The flow for incorporation of IUS into practice can be at the same time patients are seen during their visit, or alternatively, in a dedicated IUS clinic in which patients are referred by other providers and scheduled back to back.
Conclusions
In summary, the confluence of treat-to-target strategies in IBD, new treatment options in IBD, and successful efforts to translate IUS training and billing practices to the United States portends a great future for the field and for our patients.
Dr. Cleveland and Dr. Rubin, of the University of Chicago’s Inflammatory Bowel Disease Center, are speakers for Samsung/Boston Imaging.
References
1. Turner D et al. Gastroenterology. Apr 2021;160(5):1570-83. doi: 10.1053/j.gastro.2020.12.031
2. Hart AL and Rubin DT. Gastroenterology. Apr 2022;162(5):1367-9. doi: 10.1053/j.gastro.2022.02.013
3. Rajagopalan A et al. JGH Open. Apr 2020;4(2):267-72. doi: 10.1002/jgh3.12268
4. Calabrese E et al. Clin Gastroenterol Hepatol. Apr 2022;20(4):e711-22. doi: 10.1016/j.cgh.2021.03.030
5. Ripolles T et al. Inflamm Bowel Dis. Oct 2016;22(10):2465-73. doi10.1097/MIB.0000000000000882
6. Maaser C et al. Gut. Sep 2020;69(9):1629-36. doi: 10.1136/gutjnl-2019-319451
7. Ilvemark J et al. J Crohns Colitis. Nov 23 2022;16(11):1725-34. doi: 10.1093/ecco-jcc/jjac083
8. Sagami S et al. Aliment Pharmacol Ther. Jun 2020;51(12):1373-83. doi: 10.1111/apt.15767
9. Dolinger MT et al. Guide to Intestinal Ultrasound Credentialing, Documentation, and Billing for Gastroenterologists in the United States. Am J Gastroenterol. 2023.
10. Maconi G et al. Ultraschall Med. Jun 2018;39(3):304-17. doi: 10.1055/s-0043-125329
11. Sasaki T et al. Scand J Gastroenterol. Mar 2014;49(3):295-301. doi: 10.3109/00365521.2013.871744
12. Limberg B. Z Gastroenterol. Jun 1999;37(6):495-508.
13. Miyoshi J et al. J Gastroenterol. Feb 2022;57(2):82-9. doi: 10.1007/s00535-021-01847-3
14. Chen YJ et al. Inflamm Bowel Dis. Sep 15 2018;24(10):2183-90. doi: 10.1093/ibd/izy115
15. Kucharzik T et al. Apr 2017;15(4):535-42e2. doi: 10.1016/j.cgh.2016.10.040
16. Sagami S et al. Aliment Pharmacol Ther. May 2022;55(10):1320-9. doi: 10.1111/apt.16817
17. Vaughan R et al. Aliment Pharmacol Ther. Jul 2022;56(1):84-94. doi: 10.1111/apt.16892
18. International Bowel Ultrasound Group. https://ibus-group.org/
19. American Medical Association. CPT (Current Procedural Terminology). https://www.ama-assn.org/amaone/cpt-current-procedural-terminology
Evolving endpoints and treat-to-target strategies in inflammatory bowel disease (IBD) incorporate a need for more frequent assessments of the disease, including objective measures of inflammation.1,2 Intestinal ultrasound (IUS) is a noninvasive, well-tolerated,3 repeatable, point-of-care (POC) test that is highly sensitive and specific in detection of bowel inflammation, transmural healing,4,5 and response to therapy in both Crohn’s disease (CD) and ulcerative colitis (UC).6-8 As IUS is taking hold in the United States, there is a great need to teach the next generation of gastroenterologists about its value, how to incorporate it into clinical practice, and how to become appropriately trained and maintain competency.
Why incorporate IUS in the United States now?
As IBD management has evolved, so has the appreciation for the value of bedside IUS as a tool that addresses very real needs for the field. Unlike other parts of the world in which ultrasound skills are part of the training curriculum, this has not been the case in internal medicine and gastroenterology training in the United States. In addition, there have been no specific billing codes or clear renumeration processes outlined for IUS,9 nor have there been any local training opportunities. Because of these challenges, it was not until recently that several leaders in IBD in the United States championed the potential of this technology and incorporated it into IBD management. Subsequently, a number of gastroenterologists have been trained and are now leading the effort to disseminate this tool throughout the United States. A consequence of these efforts resulted in support from the Helmsley Charitable Trust (Helmsley) and the creation of the Intestinal Ultrasound Group of the United States and Canada to address the gaps unique to North America as well as to strengthen the quality of IUS research through collaborations across the continent.
What is IUS, and when is it performed?
IUS is a sonographic exam performed by a gastroenterology-trained professional who scans the abdominal wall (and perineum when the rectum and perineal disease is evaluated), using both a convex low-frequency probe and linear high-frequency probe to evaluate the small intestine, colon, and rectum. The bowel is composed of five layers with alternating hyperechoic and hypoechoic layers: the mucosal-lumen interface (not a true part of the bowel wall), deep mucosa, submucosa, muscularis propria, and serosa. (Figure)
The most sensitive parameter for assessment of IBD activity is bowel wall thickness (≤ 3 mm in the small bowel and colon and ≤ 4 mm in the rectum are considered normal in adults).8,10 The second key parameter is the assessment of vascularization, in which presence of hyperemia suggests active disease.11 There are a number of indices to quantify hyperemia, with the most widely used being the Limberg score.12 Additional parameters include assessment of loss of the delineation of the bowel wall layers (loss of stratification signifies active inflammation), increased thickness of the submucosa,13 increased mesenteric fatty proliferation (with increased inflammation, mesenteric fat proliferation will appear as a hyperechoic area surrounding the bowel), lymphadenopathy, bowel strictures, and extramural complications such as fistulae and abscess. Shear wave elastography may be an effective way to differentiate severe fibrotic strictures, but this is an area that requires more investigation.14
IUS has been shown to be an excellent tool in not only assessing disease activity and disease complication (with higher sensitivity than the Harvey-Bradshaw Index, serum C-reactive protein),15 but, unique to IUS, can provide early prediction of response in moderate to severe active UC.6,7 This has also been shown with transperineal ultrasound in patients with UC, with the ability to predict response to therapy as early as 1 week from induction therapy.16 Furthermore, it can be used to assess transmural healing, which has been shown to be associated with improved outcomes in Crohn’s patient, such as lower rates of hospitalizations, surgery, medication escalation, and need for corticosteroids.17 IUS is associated with great patient satisfaction and greater understanding of disease-related symptoms when the patient sees the inflammation of the bowel. (Table)
How can you get trained in IUS?
Training in IUS varies across the globe, from incorporation of IUS into the standard training curriculum to available training programs that can be followed and attended outside of medical training. In the United States, interested gastroenterologists can now be trained by becoming a member of the International Bowel Ultrasound Group (IBUS Group) and applying to the workshops now available. The IBUS Group has developed an IUS-specific training curriculum over the last 16 years, which is comprised of three modules: a 2-day hands-on workshop (Module 1) with final examination of theoretical competency, a preceptorship at an “expert center” with an experienced sonographer for a total of 4 weeks to complete 40 supervised IUS examinations (Module 2), and didactics and a final examination (Module 3). Also with support from Helmsley, the first Module 1 to be offered in the United States was hosted at Mount Sinai Medical Center in New York in 2022, the second was hosted at the University of Chicago in March 2023, and the third is planned to take place at Cedars-Sinai Medical Center in Los Angeles in March 2024.18 With the growing interest and demand for IUS training in the United States, U.S. experts are working to develop new training options that will be less time consuming, scalable, and still provide appropriate training and competency assessment.
How do you integrate IUS into your practice?
The keys to integrating IUS are a section chief or practice manager’s support of a trainee or faculty member for both funding of equipment and protected time for training and building of the program, as well as a permissive environment and collegial relationship with radiology. An ultrasound machine and additional transducers may range in price from $50,000-$120,000. Funding may be a limiting step for many, however. A detailed business plan is imperative to the success and investment of funds in an IUS program. With current billing practices in place that include ”limited abdominal ultrasound” (76705) and “Doppler ultrasound of the abdomen” (93975),19 reimbursement should include a technical fee, professional fee, and if in a hospital-based clinic, a facility fee. IUS pro-fee combined with technical fee is reimbursed at approximately 0.80 relative value units. When possible, the facility fee is included for approximately $800 per IUS visit. For billing and compliance with HIPAA, all billed IUS images must be stored in a durable and accessible format. It is recommended that the images and cine loops be digitally stored to the same or similar platform used by radiologists at the same institution. This requires early communication with the local information technology department for the connection of an ultrasound machine to the storage platform and/or electronic health record. Reporting results should be standardized with unique or otherwise available IUS templates, which also satisfy all billing components.9 The flow for incorporation of IUS into practice can be at the same time patients are seen during their visit, or alternatively, in a dedicated IUS clinic in which patients are referred by other providers and scheduled back to back.
Conclusions
In summary, the confluence of treat-to-target strategies in IBD, new treatment options in IBD, and successful efforts to translate IUS training and billing practices to the United States portends a great future for the field and for our patients.
Dr. Cleveland and Dr. Rubin, of the University of Chicago’s Inflammatory Bowel Disease Center, are speakers for Samsung/Boston Imaging.
References
1. Turner D et al. Gastroenterology. Apr 2021;160(5):1570-83. doi: 10.1053/j.gastro.2020.12.031
2. Hart AL and Rubin DT. Gastroenterology. Apr 2022;162(5):1367-9. doi: 10.1053/j.gastro.2022.02.013
3. Rajagopalan A et al. JGH Open. Apr 2020;4(2):267-72. doi: 10.1002/jgh3.12268
4. Calabrese E et al. Clin Gastroenterol Hepatol. Apr 2022;20(4):e711-22. doi: 10.1016/j.cgh.2021.03.030
5. Ripolles T et al. Inflamm Bowel Dis. Oct 2016;22(10):2465-73. doi10.1097/MIB.0000000000000882
6. Maaser C et al. Gut. Sep 2020;69(9):1629-36. doi: 10.1136/gutjnl-2019-319451
7. Ilvemark J et al. J Crohns Colitis. Nov 23 2022;16(11):1725-34. doi: 10.1093/ecco-jcc/jjac083
8. Sagami S et al. Aliment Pharmacol Ther. Jun 2020;51(12):1373-83. doi: 10.1111/apt.15767
9. Dolinger MT et al. Guide to Intestinal Ultrasound Credentialing, Documentation, and Billing for Gastroenterologists in the United States. Am J Gastroenterol. 2023.
10. Maconi G et al. Ultraschall Med. Jun 2018;39(3):304-17. doi: 10.1055/s-0043-125329
11. Sasaki T et al. Scand J Gastroenterol. Mar 2014;49(3):295-301. doi: 10.3109/00365521.2013.871744
12. Limberg B. Z Gastroenterol. Jun 1999;37(6):495-508.
13. Miyoshi J et al. J Gastroenterol. Feb 2022;57(2):82-9. doi: 10.1007/s00535-021-01847-3
14. Chen YJ et al. Inflamm Bowel Dis. Sep 15 2018;24(10):2183-90. doi: 10.1093/ibd/izy115
15. Kucharzik T et al. Apr 2017;15(4):535-42e2. doi: 10.1016/j.cgh.2016.10.040
16. Sagami S et al. Aliment Pharmacol Ther. May 2022;55(10):1320-9. doi: 10.1111/apt.16817
17. Vaughan R et al. Aliment Pharmacol Ther. Jul 2022;56(1):84-94. doi: 10.1111/apt.16892
18. International Bowel Ultrasound Group. https://ibus-group.org/
19. American Medical Association. CPT (Current Procedural Terminology). https://www.ama-assn.org/amaone/cpt-current-procedural-terminology
Evolving endpoints and treat-to-target strategies in inflammatory bowel disease (IBD) incorporate a need for more frequent assessments of the disease, including objective measures of inflammation.1,2 Intestinal ultrasound (IUS) is a noninvasive, well-tolerated,3 repeatable, point-of-care (POC) test that is highly sensitive and specific in detection of bowel inflammation, transmural healing,4,5 and response to therapy in both Crohn’s disease (CD) and ulcerative colitis (UC).6-8 As IUS is taking hold in the United States, there is a great need to teach the next generation of gastroenterologists about its value, how to incorporate it into clinical practice, and how to become appropriately trained and maintain competency.
Why incorporate IUS in the United States now?
As IBD management has evolved, so has the appreciation for the value of bedside IUS as a tool that addresses very real needs for the field. Unlike other parts of the world in which ultrasound skills are part of the training curriculum, this has not been the case in internal medicine and gastroenterology training in the United States. In addition, there have been no specific billing codes or clear renumeration processes outlined for IUS,9 nor have there been any local training opportunities. Because of these challenges, it was not until recently that several leaders in IBD in the United States championed the potential of this technology and incorporated it into IBD management. Subsequently, a number of gastroenterologists have been trained and are now leading the effort to disseminate this tool throughout the United States. A consequence of these efforts resulted in support from the Helmsley Charitable Trust (Helmsley) and the creation of the Intestinal Ultrasound Group of the United States and Canada to address the gaps unique to North America as well as to strengthen the quality of IUS research through collaborations across the continent.
What is IUS, and when is it performed?
IUS is a sonographic exam performed by a gastroenterology-trained professional who scans the abdominal wall (and perineum when the rectum and perineal disease is evaluated), using both a convex low-frequency probe and linear high-frequency probe to evaluate the small intestine, colon, and rectum. The bowel is composed of five layers with alternating hyperechoic and hypoechoic layers: the mucosal-lumen interface (not a true part of the bowel wall), deep mucosa, submucosa, muscularis propria, and serosa. (Figure)
The most sensitive parameter for assessment of IBD activity is bowel wall thickness (≤ 3 mm in the small bowel and colon and ≤ 4 mm in the rectum are considered normal in adults).8,10 The second key parameter is the assessment of vascularization, in which presence of hyperemia suggests active disease.11 There are a number of indices to quantify hyperemia, with the most widely used being the Limberg score.12 Additional parameters include assessment of loss of the delineation of the bowel wall layers (loss of stratification signifies active inflammation), increased thickness of the submucosa,13 increased mesenteric fatty proliferation (with increased inflammation, mesenteric fat proliferation will appear as a hyperechoic area surrounding the bowel), lymphadenopathy, bowel strictures, and extramural complications such as fistulae and abscess. Shear wave elastography may be an effective way to differentiate severe fibrotic strictures, but this is an area that requires more investigation.14
IUS has been shown to be an excellent tool in not only assessing disease activity and disease complication (with higher sensitivity than the Harvey-Bradshaw Index, serum C-reactive protein),15 but, unique to IUS, can provide early prediction of response in moderate to severe active UC.6,7 This has also been shown with transperineal ultrasound in patients with UC, with the ability to predict response to therapy as early as 1 week from induction therapy.16 Furthermore, it can be used to assess transmural healing, which has been shown to be associated with improved outcomes in Crohn’s patient, such as lower rates of hospitalizations, surgery, medication escalation, and need for corticosteroids.17 IUS is associated with great patient satisfaction and greater understanding of disease-related symptoms when the patient sees the inflammation of the bowel. (Table)
How can you get trained in IUS?
Training in IUS varies across the globe, from incorporation of IUS into the standard training curriculum to available training programs that can be followed and attended outside of medical training. In the United States, interested gastroenterologists can now be trained by becoming a member of the International Bowel Ultrasound Group (IBUS Group) and applying to the workshops now available. The IBUS Group has developed an IUS-specific training curriculum over the last 16 years, which is comprised of three modules: a 2-day hands-on workshop (Module 1) with final examination of theoretical competency, a preceptorship at an “expert center” with an experienced sonographer for a total of 4 weeks to complete 40 supervised IUS examinations (Module 2), and didactics and a final examination (Module 3). Also with support from Helmsley, the first Module 1 to be offered in the United States was hosted at Mount Sinai Medical Center in New York in 2022, the second was hosted at the University of Chicago in March 2023, and the third is planned to take place at Cedars-Sinai Medical Center in Los Angeles in March 2024.18 With the growing interest and demand for IUS training in the United States, U.S. experts are working to develop new training options that will be less time consuming, scalable, and still provide appropriate training and competency assessment.
How do you integrate IUS into your practice?
The keys to integrating IUS are a section chief or practice manager’s support of a trainee or faculty member for both funding of equipment and protected time for training and building of the program, as well as a permissive environment and collegial relationship with radiology. An ultrasound machine and additional transducers may range in price from $50,000-$120,000. Funding may be a limiting step for many, however. A detailed business plan is imperative to the success and investment of funds in an IUS program. With current billing practices in place that include ”limited abdominal ultrasound” (76705) and “Doppler ultrasound of the abdomen” (93975),19 reimbursement should include a technical fee, professional fee, and if in a hospital-based clinic, a facility fee. IUS pro-fee combined with technical fee is reimbursed at approximately 0.80 relative value units. When possible, the facility fee is included for approximately $800 per IUS visit. For billing and compliance with HIPAA, all billed IUS images must be stored in a durable and accessible format. It is recommended that the images and cine loops be digitally stored to the same or similar platform used by radiologists at the same institution. This requires early communication with the local information technology department for the connection of an ultrasound machine to the storage platform and/or electronic health record. Reporting results should be standardized with unique or otherwise available IUS templates, which also satisfy all billing components.9 The flow for incorporation of IUS into practice can be at the same time patients are seen during their visit, or alternatively, in a dedicated IUS clinic in which patients are referred by other providers and scheduled back to back.
Conclusions
In summary, the confluence of treat-to-target strategies in IBD, new treatment options in IBD, and successful efforts to translate IUS training and billing practices to the United States portends a great future for the field and for our patients.
Dr. Cleveland and Dr. Rubin, of the University of Chicago’s Inflammatory Bowel Disease Center, are speakers for Samsung/Boston Imaging.
References
1. Turner D et al. Gastroenterology. Apr 2021;160(5):1570-83. doi: 10.1053/j.gastro.2020.12.031
2. Hart AL and Rubin DT. Gastroenterology. Apr 2022;162(5):1367-9. doi: 10.1053/j.gastro.2022.02.013
3. Rajagopalan A et al. JGH Open. Apr 2020;4(2):267-72. doi: 10.1002/jgh3.12268
4. Calabrese E et al. Clin Gastroenterol Hepatol. Apr 2022;20(4):e711-22. doi: 10.1016/j.cgh.2021.03.030
5. Ripolles T et al. Inflamm Bowel Dis. Oct 2016;22(10):2465-73. doi10.1097/MIB.0000000000000882
6. Maaser C et al. Gut. Sep 2020;69(9):1629-36. doi: 10.1136/gutjnl-2019-319451
7. Ilvemark J et al. J Crohns Colitis. Nov 23 2022;16(11):1725-34. doi: 10.1093/ecco-jcc/jjac083
8. Sagami S et al. Aliment Pharmacol Ther. Jun 2020;51(12):1373-83. doi: 10.1111/apt.15767
9. Dolinger MT et al. Guide to Intestinal Ultrasound Credentialing, Documentation, and Billing for Gastroenterologists in the United States. Am J Gastroenterol. 2023.
10. Maconi G et al. Ultraschall Med. Jun 2018;39(3):304-17. doi: 10.1055/s-0043-125329
11. Sasaki T et al. Scand J Gastroenterol. Mar 2014;49(3):295-301. doi: 10.3109/00365521.2013.871744
12. Limberg B. Z Gastroenterol. Jun 1999;37(6):495-508.
13. Miyoshi J et al. J Gastroenterol. Feb 2022;57(2):82-9. doi: 10.1007/s00535-021-01847-3
14. Chen YJ et al. Inflamm Bowel Dis. Sep 15 2018;24(10):2183-90. doi: 10.1093/ibd/izy115
15. Kucharzik T et al. Apr 2017;15(4):535-42e2. doi: 10.1016/j.cgh.2016.10.040
16. Sagami S et al. Aliment Pharmacol Ther. May 2022;55(10):1320-9. doi: 10.1111/apt.16817
17. Vaughan R et al. Aliment Pharmacol Ther. Jul 2022;56(1):84-94. doi: 10.1111/apt.16892
18. International Bowel Ultrasound Group. https://ibus-group.org/
19. American Medical Association. CPT (Current Procedural Terminology). https://www.ama-assn.org/amaone/cpt-current-procedural-terminology