The First Line Of Intestinal Defence

Students of science are now going to have to learn to draw yet another organ of the human anatomy. The extra effort is necessitated by a newly classified organ called the Mesentery, in the gastric tract. Said to be hiding in plain sight within our body since the start of the human evolutionary process, scientists have described the organ as a continuous lining within the intestinal cavity, which attaches the small intestines to the large intestine and colon. The organ was previously thought to have made up of fragmented tissues which formulated separate structures inst­ead of a continuous one.

The discovery and reclassification were made by two gastroenterologists, Dr J. Calvin Coffey and Dr D. Peter O’Leary from the University Hospital of Limerick in Ireland. In research spanning over five years, they worked on cadavers as well as live subjects through surgery and radiology to establish the continuity of the organ. In a paper published in the medical journal The Lancet, the doctors explained the function and anatomical importance of Mesentery. The paper also explains the role of the organ in diseases. “Our research has shown that when you peel away the membrane holding the Mesentery, one single substantial structure which is as long as two meters in length emerges,” says Coffey in a telephonic conversation with Outlook.

While Mesentery was part of medical literature, very little was known about the organ. Until the paper was published, not only was it considered just a fragmented expanse of tissue, treatments for diseases associated with the tissue were also difficult. The classification of Mesentery as an organ has established that the mesenteric structure is a discreet one and is present in the same manner in every human body, regardless of age, race and gender, making it the basis for classification as an organ.

Through the course of medical discoveries, Mesentery has come to be classified by several different researchers in different forms. Interestingly, one of the earliest depictions of the Mesentery, associated with small bowels and the colon, was done by Leonardo Da Vinci in the 14th century. Somehow, the classification was missed by clinical anatomists for several centuries. For long, Mesentery was drawn by medical illus­trators, surgeons and physicians as a fragmented mass. The next breakthrough came in 1879, when German medical researcher Karl Toldt identified Mesentery as associated with the colon, but was unable to show its continuity and instead only suggested that the structure was flattened against the abdominal wall.

Mesentery, even when not classified as a universal organ, always played an important role in gastrointestinal sciences. “While doctors practising med­icine had a physical understanding of the organ and most of the functions associated with it, somehow, research papers and medical literature did not reflect this knowledge completely,” says Coffey.

Coffey and his team’s research strove to not only show the continuity of the organ but also to merge findings of anatomists and surgeons. This was done through collaboration with different surgeons as well as anatomists, physicians and radiologists to look at the structure from different points of view and angles to establish uniformity. During their research, Coffey and his team observed over a thousand operations, detailing the way surgeons handled the mesenteric structure.

Technological advancements in medical science too have a major role to play in the discovery, or re-assessment, of the organ. A major part of the research was done by radiologists who used high contrast CT scans as well as CAT scans to look at the structure of the organ. Several samples were also taken from cadavers in conjunction with anatomists to perform histology—the microscopic study of cells and tissues. This is done primarily to establish that the complete organ is made of similar cells and tissues, as opposed to what was earlier understood of the organ.

So what is the role of Mesentery? According to Dr Ajay Bhalla, HOD and director, Gastroenterology and Hepatology, at Fortis Hospital, Noida, it’s a double fold of peritoneum—the lining of the abdominal cavity—that attaches our intestine to the wall of our abdomen, and keeps everything locked in place. Mesenteric attachment facilitates suspension of the colon. “The Mesentery incorporates the mesocolon, mesoappendix, mesosigmoid and mesorectum,” he says. Bhalla says the organ carries blood vessels to and from several organs within the intestinal structure and is extremely important in the proper functioning of all such org­ans. Any tear or twisting within the Mesentery can cause a blockage of blood flow or even lead to the organs within the gastric tract to become gangrenous. Recent studies have also shown that it is feasible that mesenteric suspension and attachment were important developments that facilitated vertical ambulation—the human ability to  walk on two legs—in Homo sapiens. This theory is, however, still in its nascent stages and needs further research to be confirmed.

The classification of the Mesentery as an organ can now help surgeons position it within the system of the body, according to doctors associated with the research. It also means that doctors can now repeatedly and reproducibly study the structure of the organ.

Though much is still not known about how the Mesentery might function as a continuous organ. Unlike the fragmented tissue it was earlier considered to be, it has opened up a major area of study of diseases associated with it. These diseases may be classified under two categories: primary mesenteropathies, which include all diseases which arise from the Mesentery itself; and secondary mesenteropathies, which arise from extrinsic sources and may affect the Mesentery.

Most primary diseases associated with the organ relate to the herniation and rotation of the Mesentery. Malrotation, a common disease, affects inf­ants and occurs when the Mesentery does not rotate as normal during the development of the embryo within the mother’s womb. Malrotation is considered one of the most common causes of fatality due to abdominal crisis in the first year of life.

Secondary diseases associated with the organ include diseases ranging from Crohn’s disease, which is an intestinal disorder, to diseases such as obesity, diabetes and metabolic syndrome. Scientists have discovered that Mesentery is the single biggest contributor to visceral adiposity, which regulates systemic concentration of C-reactive proteins, the deregulation of which causes obesity and diabetes.

The state of the organ also points to other diseases not related to the gastric track, according to Bhalla. He says that many surgeons are able to diagnose problems in other parts of the body by simply looking at the condition of the Mesentery. These include diseases such as tuberculosis, which presents as a “creeping fat kind of necrosis” in the Mesentery.

The classification of the organ is only the first step in developing an associated study around what is expected to be a new stream in medical sciences. The dissemination of this information to different circuits of medical practitioners has already started. “It is imp­ortant to inform practising doctors as well as students about the new developments so that they can be inculcated into the syllabus and medical techniques,” says Coffey.

One of the main ways to fast track this process is by communicating the developments to anatomists, says Coffey. Medical journals and books form the basis of new readings and information for most practitioners. Anatomists are responsible for the depiction of organs and other parts of the human body. The idea, according to the scientists who published the paper, is not to educate medical practitioners about the organ, but to change perspective on how they viewed it earlier. “The Mesentery is not an altogether new discovery. While some aspects of it were known, this classification puts it in a new light and ads to the information already available to physicians,” says Coffey. As part of updating this information, the oldest text, The Grey’s Anatomy, has already been updated to include Mesentery as a distinct organ. Curriculums for medical stude­nts have also been revised accordingly.

However, as in most medical discoveries, there is still a section of medical practitioners who are not completely convinced. Bhalla of Fortis says that the discovery is nothing more than an anatomic classification. “The Mes­entery has always been treated as an important part of the body. Its function is well understood and whenever invasive or exploratory surgery is performed, it is the first thing one checks,” he says, adding that the discovery doesn’t intrinsically change the way one practises science. He points out that the Mesentery is one of the few organs which are given as much importance as the heart in the human body.

While the classification of the Mes­entery as an organ does not change the structure already present within our bodies, it does, to an extent, change one’s understanding of it. Despite the different schools of thought, it also opens a specialised new field in medical sciences, which can prove to be vital  in future improvement in health outcomes. As far as advancements go, this is a big win for the medical community and the fut­ure health of mankind.