The National Institutes of Health announced Thursday a five-year, $40 million initiative to investigate whether the dark-purple organ situated behind the human stomach serves any quantifiable biological purpose. Officials cautioned that while preliminary observational data suggests the spleen does physically exist, any claims regarding its day-to-day function remain highly speculative.
The multi-center cohort study, set to begin enrolling participants at Johns Hopkins Medicine and the Mayo Clinic later this fall, aims to establish a baseline understanding of what the 150-gram mass of lymphatic tissue has been doing inside the abdominal cavity. Researchers stressed that previous anatomical textbook models associating the spleen with red blood cell filtration were largely based on small sample sizes and anecdotal, non-blinded observations by 19th-century surgeons.
While a majority of the population appears to harbor a spleen, we must strongly caution against the premature assumption that it is actively participating in the immune system.
The grant will primarily fund a longitudinal trial in which clinicians will monitor the upper left quadrants of 5,000 healthy adults to see if the organ eventually does something. However, trial designers warn that any observed correlation between a patient's overall health and the physical presence of the organ does not necessarily indicate causation, noting that the spleen could simply be a benign anatomical bystander taking up space near the diaphragm.
Pending the publication of peer-reviewed findings, current NIH guidance advises primary care physicians to continue ignoring the organ during routine physicals to avoid confounding variables. A subset of the $40 million has reportedly been earmarked for a secondary meta-analysis to investigate the gallbladder, which researchers caution may simply be a small, naturally occurring bag of gravel.