Interstitium Facts: Newfound Organ Likely The Biggest In Human Body

The interstitium is an organ that was recently discovered by researchers in the human body. Research, published in the journal Scientific Reports on Tuesday, stated a network of dense connective tissues and fluid-filled compartments has been termed interstitium, and is likely the biggest organ found in the human body.

"Initially, we were just thinking it's an interesting tissue, but when you actually delve into how people define organs, it sort of runs around one or two ideas: that it has a unitary structure or that it's a tissue with a unitary structure, or it's a tissue with a unitary function," said Dr. Neil Theise, professor of pathology at NYU Langone Health in New York, who was a co-senior author of the study.

"This has both," he said of the interstitium. "This structure is the same wherever you look at it, and so are the functions that we're starting to elucidate."

The organ is a “previously unappreciated fluid-filled interstitial space, draining to lymph nodes and supported by a complex network of thick collagen bundles,” according to the study’s authors.

"Interstitial" is a Latin word combining "inter" or "between," and "sistere" or "to place," which literally means "between the other places."

Scientists came across the newfound organ during endoscopies — a non-surgical procedure in which doctors use a small camera attached to a tube to examine the gastrointestinal tract. Living human tissue images could be seen after sensors analyzed the resulting fluorescent patterns.

As part of the study, researchers collected tissue from 12 cancer patients when they removed the pancreas and the bile duct.

"This fixation artifact of collapse has made a fluid-filled tissue type throughout the body appear solid in biopsy slides for decades, and our results correct for this to expand the anatomy of most tissues," Theise said in the statement. "This finding has potential to drive dramatic advances in medicine, including the possibility that the direct sampling of interstitial fluid may become a powerful diagnostic tool."

Earlier, researchers thought these tissue layers were a dense "wall" of collagen — the main structural protein found in skin and other connective tissues. But the new finding revealed this tissue is more like an "open, fluid-filled highway," supported by a lattice of thick collagen "bundles."

According to reports, the interstitium protects the body’s organs, muscles and other tissues from “bumps and shocks.” Researchers said interstitium could significantly advance the understanding of cancer and many other diseases.

“These anatomic structures may be important in cancer metastasis, edema, fibrosis and mechanical functioning of many or all tissues and organs,” the study’s authors wrote. "...We describe the anatomy and histology of a previously unrecognized, though widespread, macroscopic, fluid-filled space within and between tissues, a novel expansion and specification of the concept of the human interstitium."