Introduction #
Scatology—the study of excrement—occupies a unique place in the history of medicine. What society long considered a taboo subject has become, in clinical practice, a powerful diagnostic tool and the foundation of revolutionary therapeutic approaches. From ancient diagnostic methods based on stool characteristics to modern fecal microbiota transplantation (FMT), scatology has evolved from empirical observation to a rigorous scientific discipline that transforms our understanding of health and disease.
History of Coprology: Diagnosis by Stool from Antiquity to the Nineteenth Century #
The Ancient World and Coprolological Diagnosis #
Ancient Egyptian medicine, the earliest documented medical system, already possessed sophisticated diagnostic methods. Egyptian physicians understood pulse assessment across different arteries and possessed knowledge of blood circulation. The ancient Greek historian Herodotus noted that Egyptians regularly purged their stomachs every month for three consecutive days by taking laxatives—indicating early understanding of the importance of intestinal function to overall health.
Although specific coprolological diagnostic methods are not documented as extensively in ancient Egyptian medical papyri as other diagnostic procedures, the very practice of regular bowel cleansing demonstrates awareness of the connection between digestive system status and organism health.
Coprology as a Scientific Discipline #
Coprology as a systematic medical discipline began to develop in the nineteenth century with advances in microbiology and laboratory diagnostics. The invention of the microscope allowed physicians to examine the composition of feces at the cellular level, identifying pathogenic microorganisms, parasites, occult blood, and other markers of gastrointestinal diseases.
By the late nineteenth and early twentieth centuries, coprolological examination became a standard component of clinical diagnosis, enabling detection of intestinal infections, absorption disorders, inflammatory bowel diseases, and other pathologies long before modern imaging methods became available.
Bristol Stool Scale: Standardizing Coprolological Assessment #
Development and Implementation #
In 1997, Bristol Royal Hospital developed the Bristol Stool Scale (BSS)—a diagnostic medical tool for classifying the form of human feces into seven categories. This scale became used in both clinical and experimental settings to assess the effectiveness of treatment for various intestinal diseases.
The BSS classification divides stool into seven types:
- Types 1 and 2 indicate constipation (hard, fragmented stool)
- Types 3 and 4 are considered ideal (easily passed, contain no excess liquid)
- Types 6 and 7 indicate diarrhea (loose or watery stool)
Clinical Significance and Validity #
The Bristol Scale became an important communication tool between physician and patient, and part of the diagnostic triad for Irritable Bowel Syndrome (IBS). Research showed that classification of volunteers by stool type correlated with stool water content, which increased in hard (types 1–2), normal (types 3–5), and loose stool (types 6–7).
According to a 2024 study published in Nature, BSS demonstrates substantial validity and reliability, although difficulties arise around clinical decision points (types 2, 3, 5, 6), requiring further study in larger clinical populations.
A recent study comparing stool assessment by healthcare workers and children showed that the modified scale for children (mBSFS-C) provides higher agreement and greater consistency in clinical evaluation of stool form.
Gut Microbiome: Revolution in Health Understanding #
The Human Microbiome Project #
The Human Microbiome Project (HMP), along with the Earth Microbiome Project and next-generation sequencing, advanced new genomic associations, connections with host genetics, and pathogen identification. The Integrative Human Microbiome Project (iHMP, Phase II) applied multi-omics strategies to study epidemiology, evolution, and diversity of gut microbial communities, going beyond taxonomic and functional profiling and laying the foundation for microbiome-based disease prevention, therapeutic interventions, and precision medicine.
Connection of Microbiome to Disease #
Dysbiosis of the gut microbiome is associated with various disorders, including gastrointestinal diseases such as Clostridioides difficile infection and inflammatory bowel diseases, as well as metabolic, neurological, and oncological conditions.
The rapidly growing field of microbiome-based therapeutics has attracted significant attention for its potential to revolutionize healthcare. The “Gut Microbiota for Health World Summit 2024” highlighted progress in this field, including recent successful implementation of two new fecal microbiota transplantation-based products into clinical practice.
Fecal Microbiota Transplantation (FMT): From Concept to Clinical Practice #
History and Mechanism of Action #
Fecal microbiota transplantation is a procedure involving transfer of fecal material from a healthy donor into the gastrointestinal tract of a recipient to restore normal composition of the intestinal microbiota. Although the idea of using feces for therapeutic purposes has ancient roots (fourth-century Chinese medicine used “yellow soup”), modern medical FMT practice began developing in the 1950s.
The mechanism of action of FMT is based on restoration of microbial diversity and functionality of the gut microbiome. In recurrent C. difficile infection, antibiotic therapy often disrupts normal microbiota, creating conditions for pathogen recolonization. FMT restores protective functions of the microbiome, including competition for nutrients, production of antimicrobial metabolites, and modulation of immune response.
FDA Status and Regulation #
The FDA approved two standardized microbiota-based therapeutic products—Rebyota™ (fecal microbiota, live-jslm) and Vowst™ (fecal microbiota spores, live-brpk)—for prevention of recurrent C. difficile infection. This became an important milestone in legitimizing FMT as a standard medical procedure.
Prior to this approval, FMT was applied under so-called FDA “enforcement discretion,” which permitted its use in recurrent C. difficile infection without formal approval as a new drug.
Clostridioides difficile and FMT Success #
Clinical Efficacy #
Clostridioides difficile infection (CDI) represents a serious clinical problem, particularly in cases of recurrent disease. FMT has demonstrated impressive efficacy in preventing CDI recurrence following antibiotic therapy—ranging from 80% to 95% success rates.
A meta-analysis showed that FMT has a 89% success rate in treating CDI, and long-term follow-up of patients who received FMT for treatment of recurrent CDI showed primary cure rates of 91%.
Clinical Guidelines #
FMT is recognized as a validated treatment method for recurrent or resistant C. difficile infection. Clinical practice guidelines, including recommendations from the Infectious Diseases Society of America and the American College of Gastroenterology, recommend FMT after the second recurrence—or third episode—of CDI.
A recent systematic review in 2025 confirmed the beneficial effects of FMT for recurrent Clostridioides difficile infection, establishing it as a first-line therapy in refractory cases.
Future Directions: Microbiome Therapies for Autism, Depression, and Obesity #
Autism Spectrum Disorder (ASD) #
Research shows promising results for microbiome-based therapies in autism. According to a 2025 systematic review, 15 randomized controlled trials (RCTs) were identified from 1,080 records in major medical databases through August 2024. Four randomized double-blind placebo-controlled clinical trials are planned to be completed in 2024 and 2025 involving adults aged 18–60 with autism and gastrointestinal problems, as well as children with autism.
One RCT, six non-randomized studies (all open clinical trials), and two retrospective studies examined the effect of fecal microbiota transplantation therapy in autism—all showed significant improvement in overall autism severity.
FMT consistently demonstrated the most positive results across all studies, particularly in reducing autism severity and improving gastrointestinal function. A long-term study of the benefits of microbiota transfer therapy on autism symptoms and gut microbiota showed sustained improvements.
Depression and Neuropsychiatric Conditions #
Recent neuroscience research has connected changes in microbiome and microbial metabolites with various neuropsychiatric disorders, such as autism, depression, anxiety, schizophrenia, eating disorders, and neurocognitive impairment.
Emerging applications highlight the potential of capsule-based fecal microbiota transplantation for neuropsychiatric conditions (e.g., depression and autism) via gut-brain axis signaling. The concept of “psychobiotics”—probiotics with potential mental health effects through the gut-brain axis—represents a contemporary approach to depression treatment.
Obesity and Metabolic Disorders #
Capsule-based fecal microbiota transplantation shows potential for treating metabolic disorders (e.g., obesity and hypertension) through modulation of gut-derived metabolites.
Research indicates that gut microbiome composition can influence energy metabolism, inflammation, and body weight regulation. Microbiota transplantation from lean donors to patients with obesity has in some studies shown improvement in metabolic parameters, although results require confirmation in large-scale controlled trials.
Future Research Directions #
Large-scale, well-controlled studies with standardized protocols, diverse populations, and long-term follow-up are necessary to establish definitive clinical guidelines. Additionally, personalized approaches based on microbiome profiling may enhance treatment efficacy by adapting interventions to individual gut microbiota compositions.
Microbiome-informed therapy adapted to individual microbial and genetic profiles will lead to improved health outcomes, opening a new era of effective, sustainable, and personalized healthcare.
Ethical Considerations: Stool Donation and Commercialization #
Fecal Matter Donation #
Stool donation for FMT raises unique ethical questions distinct from traditional biological material donation. The process requires careful screening of donors for infectious diseases, metabolic disorders, and other factors that may impact the safety and efficacy of the procedure.
Key ethical considerations include:
- Informed consent: donors must understand how their material will be used and what research may be conducted
- Confidentiality: protection of personal information of donors and recipients
- Long-term risks: insufficient understanding of long-term consequences of microbiota transfer
- Anonymity vs. traceability: balancing protection of donor identity with the need to track material source in case of complications
Commercialization of Microbiome Therapies #
FDA approval of commercial products Rebyota™ and Vowst™ marked the beginning of a new era in commercialization of microbiome-based therapies. This raises important ethical questions:
Accessibility and equity: commercial products may be more expensive than traditional FMT performed in clinical settings. There is risk that patients with limited financial resources may lose access to this effective therapy.
Patenting and monopolization: patenting of specific microbial strains or compositions may limit research and innovation in this field. The question of whether natural microbial communities can be patented remains subject to debate.
Stool banks: the emergence of commercial stool banks creates a new industry with questions about regulation, standardization, and donor compensation. Should stool donation be altruistic, or do donors have a right to compensation?
Medicalization of natural processes: there are concerns that commercialization may lead to unnecessary medicalization of conditions that could be treated with dietary and lifestyle changes.
Cultural and religious aspects: use of fecal material may conflict with cultural or religious beliefs of some populations, requiring culturally sensitive approaches to informed consent.
Regulation and Standardization #
With the development of the microbiome therapeutics industry comes a need for strict standards:
- Quality control: standardization of donor screening processes, material preparation and storage
- Clinical protocols: development of unified application protocols for various indications
- Post-market surveillance: long-term monitoring of safety and efficacy of commercial products
- International cooperation: harmonization of regulatory approaches between countries to facilitate research and knowledge sharing
Conclusion #
Medical scatology has traveled a remarkable path from ancient empirical observations to modern precision medicine. The Bristol Stool Scale standardized coprolological diagnosis, making it an objective and reproducible tool. The Human Microbiome Project revolutionized our understanding of the role of gut microbiota in health and disease.
Fecal microbiota transplantation, demonstrating outstanding results in treating recurrent C. difficile infection with success rates of 80–95%, opens new horizons for treatment of a wide spectrum of diseases—from autism and depression to obesity and metabolic disorders. FDA approval of the first commercial FMT-based products marks the transition of this therapy from experimental to mainstream clinical practice.
However, these achievements bring important ethical challenges. Questions of stool donation, commercialization of microbiome therapies, equitable access, and cultural sensitivity require careful attention as this field develops. The future of microbiome medicine lies in personalized approaches based on individual microbiome profiling, promising a new era of precise, effective, and sustainable therapy.
To realize this potential, large-scale clinical studies with standardized protocols, long-term follow-up, and attention to ethical aspects are necessary. Scatology, having overcome social taboos, is becoming one of the most promising areas of modern medicine, confirming that in science there are no “low” topics—only unexplored opportunities for improving human health.
Related Materials #
Sources #
- History of Medicine. Egypt — Habr
- Ancient Egyptian Medicine — Wikipedia
- Bristol stool scale — Wikipedia
- Development and validation of a gut motility based model — Nature Scientific Reports, 2024
- Validity and reliability of the Bristol Stool Form Scale — PubMed
- Comparison of the Bristol Stool Scale and modified version for children — PMC
- Fecal microbiota transplantation: Current evidence and future directions — Cleveland Clinic Journal of Medicine
- Treating Clostridium difficile Infection with Fecal Microbiota Transplantation — PMC
- Fecal Microbiota Transplantation: How & Why — Cleveland Clinic
- Faecal microbiota transplantation for recurrent Clostridioides difficile infection: An updated systematic review and meta-analysis — The Lancet eClinicalMedicine
- AGA Clinical Practice Guideline on Fecal Microbiota — Gastrojournal
- What’s New and What’s Next in Fecal Microbiota Transplantation? — PMC
- Beneficial effects of fecal microbiota transplantation in recurrent Clostridioides difficile infection — ScienceDirect
- Gut microbiome: a biomedical revolution — PubMed, 2024
- Microbiome 2.0: lessons from the 2024 Gut Microbiota for Health World Summit — PMC
- Advancing Gut Microbiome Research: Multi-Omics and Future Perspectives — PMC
- Microbiome-Driven Therapeutics: From Gut Health to Precision Medicine — MDPI
- Efficacy of gut microbiota-based therapy for autism Spectrum Disorder and ADHD — Taylor & Francis, 2025
- Microbiota-based interventions for autism spectrum disorder — Frontiers in Microbiology, 2025
- Long-term benefit of Microbiota Transfer Therapy on autism symptoms and gut microbiota — Scientific Reports
- The Power of Psychobiotics in Depression — MDPI Nutrients
- Advances in capsule-based fecal microbiota transplantation — Journal of Translational Medicine, 2025
FolkUp Research Lab | Lucerna