Comprehensive Stool Analysis + Parasitology - 1 Day

The colonic microbiome comprises hundreds of bacterial species, predominantly anaerobic genera including Bacteroides, Firmicutes (Faecalibacterium, Ruminococcus, Clostridium clusters), Bifidobacterium, and Lactobacillus. These organisms ferment dietary fibre to short-chain fatty acids, synthesise vitamins, maintain epithelial barrier integrity, and modulate local and systemic immune responses. Commensal balance — termed eubiosis — is disrupted by antibiotics, diet, infection, and inflammation.

Semi-quantitative culture or molecular enumeration of major commensal groups helps identify dysbiosis — reduced diversity, overgrowth of facultative aerobes, or loss of beneficial anaerobes — that may contribute to diarrhoea, constipation, and systemic inflammation. Patterns of imbalance guide therapeutic decisions around prebiotics, probiotics, dietary modification, and antimicrobial therapy.

Opportunistic enteric bacteria — including certain E. coli pathotypes, Klebsiella, Proteus, Pseudomonas, and Clostridium difficile — are present at low levels or absent in healthy stool. Under antibiotic pressure, immune compromise, or dysbiosis they may proliferate and contribute to colitis, systemic translocation, or infection beyond the gut.

Detection and semi-quantitative grading of opportunistic organisms inform targeted antimicrobial therapy and guide interpretation of gastrointestinal symptoms. Clostridium difficile is a common cause of antibiotic-associated diarrhoea; overgrowth of Klebsiella or pathogenic E. coli can perpetuate dysbiosis and mucosal inflammation.

Yeasts, particularly Candida albicans and non-albicans Candida species, may colonise the gastrointestinal tract transiently or persistently. In healthy hosts they are kept in check by commensal bacteria and mucosal immunity. Antibiotic use, immunosuppression, and carbohydrate-rich diets can promote fungal overgrowth.

Moderate to heavy yeast growth, especially with symptoms of bloating, diarrhoea, or systemic 'yeast syndrome' complaints, may warrant antifungal therapy and dietary modification. Candida overgrowth is a recognised sequela of broad-spectrum antibiotic use and is implicated in some cases of irritable bowel syndrome.

Intestinal parasites — protozoa (Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Blastocystis hominis, Dientamoeba fragilis) and helminths (roundworms, tapeworms, flukes) — are acquired through contaminated food, water, or contact. Concentrated wet-mount microscopy, trichrome staining, and antigen or molecular detection methods improve sensitivity over single routine ova-and-parasite examination.

Detection of pathogenic protozoa or helminths explains persistent diarrhoea, abdominal pain, malabsorption, and eosinophilia. Giardia and Cryptosporidium are common in travellers and those with waterborne exposure; Blastocystis and Dientamoeba are more controversial but are treated when symptomatic. Antigen or PCR methods are more sensitive than microscopy alone for many species.

Calprotectin is a calcium- and zinc-binding protein abundant in neutrophil cytoplasm. It is released into the intestinal lumen during mucosal inflammation and is stable in stool for several days at room temperature. Faecal calprotectin correlates with neutrophil infiltration of the mucosa and is used as a non-invasive marker of inflammatory bowel disease activity.

Elevated calprotectin distinguishes organic inflammatory disease (Crohn's disease, ulcerative colitis, infectious colitis) from functional disorders such as irritable bowel syndrome. It is used to screen for IBD in patients with chronic diarrhoea, to monitor disease activity, and to detect subclinical relapse. Values above 150–250 µg/g strongly suggest active inflammation warranting endoscopy.

Secretory IgA is the predominant immunoglobulin in mucosal secretions, produced by plasma cells in the lamina propria and transported across the epithelium as a dimeric molecule bound to secretory component. It binds luminal antigens and microbes, preventing their adhesion to and penetration of the epithelium, and is a key component of mucosal immunity.

Low faecal sIgA may reflect mucosal immune deficiency, chronic stress, malnutrition, or dysbiosis, and is associated with increased susceptibility to enteric infection and food sensitivities. Elevated sIgA can indicate an active mucosal immune response to pathogens or chronic antigen exposure. Interpretation is exploratory; clinical utility is debated and thresholds are not standardised.

Pancreatic elastase-1 is a protease synthesised by pancreatic acinar cells, secreted into the duodenum, and stable during intestinal transit. Its concentration in stool reflects exocrine pancreatic output and is not degraded by pancreatic enzyme replacement therapy, making it a specific marker of endogenous pancreatic function.

Faecal elastase-1 is the non-invasive test of choice for screening exocrine pancreatic insufficiency — seen in chronic pancreatitis, cystic fibrosis, pancreatic cancer, and coeliac disease. Values below 200 µg/g prompt consideration of pancreatic enzyme replacement; below 100 µg/g is diagnostic of severe insufficiency. False-positive (low) results occur with watery diarrhoea due to dilution.

Stool pH reflects the balance of fermentation (short-chain fatty acid production, which lowers pH) and putrefaction (ammonia and other alkaline metabolites, which raise pH). Low pH indicates robust carbohydrate fermentation by commensal anaerobes; high pH may reflect reduced fibre fermentation, bacterial overgrowth, or protein maldigestion.

Faecal pH is an indirect marker of colonic fermentation and microbial metabolism. Persistently alkaline stool (pH >7.5) can suggest dysbiosis with reduced saccharolytic fermentation or increased proteolytic activity. Interpretation is exploratory and must be read alongside other microbiome and digestive markers.

Short-chain fatty acids are the principal end-products of anaerobic bacterial fermentation of dietary fibre in the colon. Butyrate is the preferred fuel for colonocytes and maintains epithelial barrier integrity; propionate and acetate have systemic metabolic effects. SCFA production depends on fibre intake, microbiome composition, and colonic transit time.

Low butyrate production is implicated in inflammatory bowel disease, colorectal cancer, and metabolic syndrome. Measuring faecal SCFA profiles can guide dietary fibre modification and prebiotic or probiotic therapy. Interpretation is exploratory; clinical thresholds are not standardised and the field is evolving.