Study finds significant variation in anatomy of human guts
IMAGE: NEW RESEARCH FINDS THERE IS SIGNIFICANT VARIATION IN THE ANATOMY OF THE HUMAN DIGESTIVE SYSTEM, WITH PRONOUNCED DIFFERENCES POSSIBLE BETWEEN HEALTHY INDIVIDUALS. THE FINDING HAS IMPLICATIONS FOR UNDERSTANDING THE ROLE THAT THE DIGESTIVE TRACT’S ANATOMY CAN PLAY IN AFFECTING HUMAN HEALTH, AS WELL AS PROVIDING POTENTIAL INSIGHTS INTO MEDICAL DIAGNOSES AND THE MICROBIAL ECOSYSTEM OF THE GUT. IN THIS PHOTO, A RESEARCHER TAKES A GUT MEASUREMENT IN THE LAB. view more
CREDIT: LAUREN NICHOLS
New research finds there is significant variation in the anatomy of the human digestive system, with pronounced differences possible between healthy individuals. The finding has implications for understanding the role that the digestive tract’s anatomy can play in affecting human health, as well as providing potential insights into medical diagnoses and the microbial ecosystem of the gut.
“There was research more than a century ago that found variability in the relative lengths of human intestines, but this area has largely been ignored since then,” says Amanda Hale, co-first author of the study and a Ph.D. candidate at North Carolina State University. “When we began exploring this issue, we were astonished at the extent of the variability we found.”
“If you’re talking to four different people, odds are good that all of them have different guts, in terms of the relative sizes of the organs that make up that system,” says Erin McKenney, corresponding author of the study and an assistant professor of applied ecology at NC State. “For example, the cecum is an organ that’s found at the nexus of the large and small intestine. One person may have a cecum that is only a few centimeters long, while another may have a cecum the size of a coin purse. And we found similar variability for many digestive organs.”
In another striking example, the researchers found that women tend to have longer small intestines than men.
“Because having a longer small intestine helps you extract nutrients from your diet, this finding supports the canalization hypothesis, which posits that women are better able to survive during periods of stress,” says Hale.
“Given that there is more variation in human gut anatomy than we thought, this could inform our understanding of what is driving a range of health-related issues and how we treat them,” says McKenney. “Basically, now that we know this variability exists, it raises a number of research questions that need to be explored.”
For this study, the researchers measured the digestive organs of 45 people who donated their remains to the Anatomical Gifts Program at the Duke University School of Medicine.
In addition to shedding light on the unexpected variability in human anatomy, this project also led to rediscovering the importance of teaching anatomical variation to medical students.
“It’s particularly important in medical training, because if students are only learning about a ‘normal’ or ‘average’ anatomy, that means they are not going to be familiar with the scope of human variation,” says Roxanne Larsen, co-author of the paper and an associate professor of veterinary and biomedical sciences at the University of Minnesota. “It’s increasingly clear that the medical field is moving toward individualized medicine to improve patient outcomes and overall health and well-being. Garnering experience in understanding anatomical variation can play a critical role in helping future doctors understand the importance of individualized medicine.”
“We’re excited about this discovery and future directions for the work,” McKenney says. “It underscores just how little we know about our own bodies.”
The paper, “Hidden Diversity: Comparative Functional Morphology of Humans and Other Species,” will be published April 24 in the open-access journal PeerJ. The paper was co-authored by Janiaya Anderson, a former undergraduate at NC State; Colleen Grant, a former research scientist at NC State; and by Rob Dunn, William Neal Reynolds Distinguished Professor of Applied Ecology and Senior Vice Provost for University Interdisciplinary Programs at NC State.
JOURNAL
PeerJ
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Hidden Diversity: Comparative Functional Morphology of Humans and Other Species
ARTICLE PUBLICATION DATE
24-Apr-2023
Study finds stool transplants more effective than antibiotics for treating recurring, life-threatening gut infections
A new Cochrane Review has found that, compared with standard antibiotic treatment, stool transplantation can increase the number of people recovering from Clostridioides difficile (C. diff) infection from 40% to 77%
Peer-Reviewed PublicationA new Cochrane Review led by an Upstate Medical University professor has found that, compared with standard antibiotic treatment, stool transplantation can increase the number of people recovering from Clostridioides difficile (C. diff) infection, a condition which causes potentially life-threatening diarrhea. 77 percent of people who received a stool transplant did not experience reinfection within eight weeks, compared to 40 percent of those who received antibiotics alone.
C. diff is a bacterium that can cause life-threatening diarrheal illness in individuals with an unhealthy mixture of gut bacteria, known as dysbiosis. The most common cause of dysbiosis is treatment with antibiotics, and while antibiotics can be very effective against bacterial infections, they can also harm the beneficial bacteria colonizing the gut, known as the intestinal microbiome. Usually this ecosystem of “good” bacteria recovers quickly, but occasionally “bad” species like C. diff take over and cause serious diarrhea.
The standard treatment of C. diff infection includes antibiotics, which may further exacerbate dysbiosis. This can lead to a vicious cycle of brief treatment effect followed by a recurrent infection. This happens in nearly a third of infected individuals. According to the CDC, every year there are around a quarter of a million C. diff infections in the US alone, causing approximately 12,000 fatalities.
Transplanting healthy donor stool into a gut with dysbiosis is intended to balance the gut microbes and reestablish a healthy microbiome, thus significantly reducing the risk of C. diff recurring. Stool donation operates much the same way as blood donation. Donors are screened for diseases and infections before they can donate their stool. The stool can be transplanted via colonoscopy, nasogastric or nasoduodenal tube, enema or via a capsule. The US Food and Drug Administration has recently approved a stool transplant product for prevention of recurrence of C. diff that can be administered as enema.
The new Cochrane Review, led by pediatric gastroenterologist Aamer Imdad MBBS, examined data from six clinical trials with a total of 320 adults that assessed the efficacy and safety of stool transplantation for the treatment of repeated C. diff infection. Two studies were conducted in Denmark, and one each in the Netherlands, Italy, Canada, and the United States. Most of the included studies compared stool transplantation with a standard antibiotic treatment using vancomycin, which is commonly used for this kind of infection.
The review found that stool transplantation leads to a larger increase in resolution of repeated infections of C. diff than other treatments studied, as well as a decrease in side effects when compared with standard treatment using antibiotics.
“After a person with a C. diff infection gets treated with antibiotics, there is about a 25 percent chance that they will have another episode of C. diff infection in the next 8 weeks”, Imdad said. “The risk of recurrence increases to about 40 percent with the second episode and to nearly 60 percent with the third episode. So, once you are in this cycle, it gets more and more difficult to break out of it. Stool transplants can reverse the dysbiosis and thus decrease the risk of recurrence of the disease.”
A second Cochrane Review, also led by Dr. Imdad, looks at the use of stool transplants for the treatment of inflammatory bowel disease (IBD), a term mainly used to describe two conditions: ulcerative colitis and Crohn's disease. The review shows promising results for ulcerative colitis; however, the data is not conclusive yet. Results for Crohn’s disease are even less conclusive. More research will be required before stool transplants can be considered for the treatment of IBD.
Imdad collaborated with doctors around the country on both studies, including Nathan Zev Minkoff, a graduate from the Norton College of Medicine, Upstate students Natasha Pandit and Muiz Zaman, Class of 2023 in the Norton College of Medicine and Melissa Medina, Class of 2026 in the Department of Public Health and Preventative Medicine, on the C-diff study. The other collaborators included Dr. Maribeth Nicholson and Dr. Sari Acra from Vanderbilt University Medical Center, Dr. Scheherzade Asalam from University of Nebraska, Dr. Emily E Tanner Smith from University of Oregon, Dr. Oscar Gomez from University of Buffalo and Dr. Joseph Zackular from University of Pennsylvania.
JOURNAL
Cochrane Database of Systematic Reviews
METHOD OF RESEARCH
Systematic review
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Fecal microbiota transplantation for thetreatment of recurrent Clostridioidesdifficile (Clostridium difficile)
ARTICLE PUBLICATION DATE
24-Apr-2023
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