Causes of loose stools
Pro Research Analysisby 
Searched over 200M research papers
Common Causes of Loose Stools
Loose stools, often described as diarrhea, can result from a wide range of causes. These include infections, digestive disorders, genetic factors, dietary issues, and certain medical treatments or surgeries. The underlying mechanisms and specific causes can vary by age group and individual health status.
Infectious Causes of Loose Stools
Infections are a leading cause of loose stools, especially in children and in cases of acute diarrhea. Viruses (such as rotavirus and norovirus), bacteria (like Campylobacter and Shigella), and parasites (such as Cryptosporidium) are frequently identified as culprits, particularly in low- and middle-income countries and among young children. The prevalence and type of pathogen can vary by geography, age, and season 59. In children under five, rotavirus is a particularly common cause, while bacterial and parasitic infections are also significant contributors 59.
Non-Infectious and Functional Causes
Loose stools can also be caused by non-infectious factors. Functional gastrointestinal disorders, such as irritable bowel syndrome (IBS) and functional diarrhea, are common causes of chronic loose stools in adults. These conditions are often diagnosed when no clear structural or biochemical cause is found 3810.
Malabsorption and Digestive Disorders
Malabsorption syndromes, where the body cannot properly absorb nutrients, can lead to loose stools. Examples include celiac disease, pancreatic exocrine insufficiency, and bile acid malabsorption. These conditions often result in fatty or watery diarrhea, depending on the underlying problem 310. After certain surgeries, such as right-sided hemicolectomy for colon cancer, patients may experience chronic loose stools due to bile acid malabsorption or small intestinal bacterial overgrowth .
Genetic Factors
Genetic variations can also play a role. For example, hypomorphic variants in the sucrase-isomaltase (SI) gene are associated with congenital sucrase-isomaltase deficiency (CSID), which leads to chronic loose stools in children. Children with these genetic variants experience more frequent and severe gastrointestinal symptoms compared to those without the variants .
Dietary and Medication-Related Causes
Dietary factors, such as the ingestion of nonabsorbable, osmotically active substances (e.g., certain sugars or laxatives), can cause osmotic diarrhea, leading to loose stools. Medications, including antibiotics and some supplements, can also disrupt normal stool consistency 346. In neonates, the initiation of supplementary feeding and antibiotic use are notable contributors to loose stools, though most cases are non-infective .
Mechanisms Behind Stool Looseness
The consistency of stools is primarily determined by the ratio of fecal water to the water-holding capacity of insoluble solids. In diarrhea, an increase in fecal water or a decrease in insoluble solids can result in looser stools. Conditions like steatorrhea (excess fat in stools) and low output of insoluble solids can make stools looser even if the water content is not significantly increased .
Conclusion
Loose stools can be caused by a variety of factors, including infections, functional disorders, malabsorption syndromes, genetic variants, dietary habits, medications, and surgical interventions. The underlying mechanism often involves an imbalance between fecal water and the water-holding capacity of stool solids. Identifying the specific cause is important for effective management and treatment.
Sources and full results
Most relevant research papers on this topic
Determinants of decreased fecal consistency in patients with diarrhea.
Stool looseness in diarrhea is determined by the ratio of fecal water to insoluble solids' water-holding capacity, with steatorrhea stools being looser than nonsteatorrhea stools, and psyllium reducing looseness without changing water content.
Hypomorphic SI genetic variants are associated with childhood chronic loose stools
Non-Hispanic white children with chronic idiopathic loose stools have a higher prevalence of CSID-associated hypomorphic SI variants and a greater gastrointestinal symptom burden than those without such variants.
Chronic Diarrhea in Adults: Evaluation and Differential Diagnosis.
Chronic diarrhea in adults can be categorized into watery, fatty, or inflammatory types, with differential diagnosis based on the type of diarrhea and the underlying disorder.
Knowledge on home management of diarrhea among caregivers of children below five years with diarrhea in Ngandu Location, Nyeri County, Kenya
Diarrhea in children under five years is a major contributor to childhood illness and death in third-world countries, with risk factors including poor personal hygiene, unclean food, and unclean domestic water.
Loose stools in the early neonatal period.
Loose stools in newborns are more common in low birth weight babies, delivered by Cesarean section, and those with more than two children, but most are non-bacterial and non-infective, so caution is needed when administering antibiotics.
Chronic loose stools following right‐sided hemicolectomy for colon cancer and the association with bile acid malabsorption and small intestinal bacterial overgrowth
Chronic loose stools after right-sided hemicolectomy for colon cancer are associated with bile acid malabsorption and small intestinal bacterial overgrowth.
Pathogen-specific burdens of community diarrhoea in developing countries: a multisite birth cohort study (MAL-ED).
Single-pathogen strategies can reduce severe diarrhoeal disease, but their impact on total community diarrhoea incidence may be limited.
Chronic Diarrhea: Diagnosis and Management.
Chronic diarrhea is diagnosed using history and physical examination, with testing being necessary for alarm features or when a specific cause is unclear.
DOI