-
Vitamins and Hormones 2022Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC)... (Review)
Review
Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC) and their respective membrane receptors. Vitamin deficiency is mainly due to inadequate dietary intake in vegans, and B12 malabsorption is related to digestive diseases. This review explores the physiology of vitamin B12 absorption and the mechanisms and diseases that produce malabsorption. In the stomach, B12 is released from food carrier proteins and binds to HC. The degradation of HC by pancreatic proteases and the pH change trigger the transfer of B12 to IF in the duodenum. Cubilin and amnionless are the two components of the receptor that mediates the uptake of B12 in the distal ileum. Part of liver B12 is excreted in bile, and undergoes an enterohepatic circulation. The main causes of B12 malabsorption include inherited disorders (Intrinsic factor deficiency, Imerslund-Gräsbeck disease, Addison's pernicious anemia, obesity, bariatric surgery and gastrectomies. Other causes include pancreatic insufficiency, obstructive Jaundice, tropical sprue and celiac disease, bacterial overgrowth, parasitic infestations, Zollinger-Ellison syndrome, inflammatory bowel diseases, chronic radiation enteritis of the distal ileum and short bowel. The assessment of B12 deficit is recommended in the follow-up of subjects with bariatric surgery. The genetic causes of B12 malabsorption are probably underestimated in adult cases with B12 deficit. Despite its high prevalence in the general population and in the elderly, B12 malabsorption cannot be anymore assessed by the Schilling test, pointing out the urgent need for an equivalent reliable test.
Topics: Adult; Aged; Anemia, Megaloblastic; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Vitamin B 12; Vitamin B 12 Deficiency
PubMed: 35337622
DOI: 10.1016/bs.vh.2022.01.016 -
The Nursing Clinics of North America Sep 2018Malabsorption syndrome refers to the small intestines' inability to absorb certain nutrients and fluids. There are several common associated disorders, which may present... (Review)
Review
Malabsorption syndrome refers to the small intestines' inability to absorb certain nutrients and fluids. There are several common associated disorders, which may present with subtle and/or overt symptoms. With subtle symptoms, it is difficult to determine the cause, making diagnosis difficult or even inaccurate. Malabsorption can originate from an immune response, an inflammatory process, or alternation of the small intestines by surgical methods. This article reviews common malabsorption disease processes of the small bowel and the resulting pathophysiology. Diagnostic studies, treatment, and prognosis of various conditions within the malabsorption disease state are discussed.
Topics: Celiac Disease; Humans; Malabsorption Syndromes; Short Bowel Syndrome
PubMed: 30100002
DOI: 10.1016/j.cnur.2018.05.001 -
Gut Nov 2019Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in... (Review)
Review
Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in populations that maintain the ability to digest this disaccharide in adulthood. Lactase deficiency (LD) is the failure to express the enzyme that hydrolyses lactose into galactose and glucose in the small intestine. The genetic mechanism of lactase persistence in adult Caucasians is mediated by a single C→T nucleotide polymorphism at the LCTbo -13'910 locus on chromosome-2. Lactose malabsorption (LM) refers to any cause of failure to digest and/or absorb lactose in the small intestine. This includes primary genetic and also secondary LD due to infection or other conditions that affect the mucosal integrity of the small bowel. Lactose intolerance (LI) is defined as the onset of abdominal symptoms such as abdominal pain, bloating and diarrhoea after lactose ingestion by an individual with LM. The likelihood of LI depends on the lactose dose, lactase expression and the intestinal microbiome. Independent of lactose digestion, patients with visceral hypersensitivity associated with anxiety or the Irritable Bowel Syndrome (IBS) are at increased risk of the condition. Diagnostic investigations available to diagnose LM and LI include genetic, endoscopic and physiological tests. The association between self-reported LI, objective findings and clinical outcome of dietary intervention is variable. Treatment of LI can include low-lactose diet, lactase supplementation and, potentially, colonic adaptation by prebiotics. The clinical outcome of these treatments is modest, because lactose is just one of a number of poorly absorbed carbohydrates which can cause symptoms by similar mechanisms.
Topics: Humans; Lactose Intolerance; Malabsorption Syndromes
PubMed: 31427404
DOI: 10.1136/gutjnl-2019-318404 -
Gastroenterology Clinics of North... Jun 2021The term "small intestinal bacterial overgrowth" (SIBO) has been used to refer to a disorder resulting from the colonization of the small bowel by an increased number of... (Review)
Review
The term "small intestinal bacterial overgrowth" (SIBO) has been used to refer to a disorder resulting from the colonization of the small bowel by an increased number of microorganisms or by the presence of bacteria that are not usual constituents of this part of the gastrointestinal tract. Clinical presentations, often in patients with certain risk factors, can range from a full-blown malabsorption syndrome to such "functional" complaints as bloating and flatulence. SIBO is diagnosed by either culture of a small bowel aspirate or one of several breath tests. Treatment of SIBO entails risk factor modification, correction of nutritional deficiencies, and oral antibiotics.
Topics: Anti-Bacterial Agents; Bacterial Infections; Breath Tests; Humans; Intestine, Small; Malabsorption Syndromes
PubMed: 34024452
DOI: 10.1016/j.gtc.2021.02.008 -
American Family Physician Aug 2016Children with very low weight for age or height and those who do not maintain an appropriate growth pattern may have failure to thrive (FTT), also known as weight... (Review)
Review
Children with very low weight for age or height and those who do not maintain an appropriate growth pattern may have failure to thrive (FTT), also known as weight faltering. If confirmed by repeated valid measurements, FTT should prompt a search for causes of undernutrition, including neglect, family food insecurity, and underlying medical conditions. Inadequate caloric intake is the most common cause of FTT, but inadequate nutrient absorption or increased metabolism is also possible. Difficulty attaining or maintaining appropriate weight is the first indication of FTT, and sustained undernutrition can impede appropriate height, head circumference, and the development of cognitive skills or immune function in extreme cases. Early identification and management of the issues causing undernutrition are critical. In most cases, an appropriate growth velocity can be established with outpatient management based on proper nutrition and family support. Primary care physicians can effectively treat most children with FTT, and subspecialist consultation or hospitalization is rarely indicated.
Topics: Adolescent; Body Weight; Child; Child, Preschool; Early Diagnosis; Early Medical Intervention; Energy Intake; Failure to Thrive; Growth Charts; Humans; Infant; Infant, Newborn; Malabsorption Syndromes; Malnutrition; Practice Guidelines as Topic
PubMed: 27548594
DOI: No ID Found -
American Family Physician Apr 2020Chronic diarrhea is defined as a predominantly loose stool lasting longer than four weeks. A patient history and physical examination with a complete blood count,...
Chronic diarrhea is defined as a predominantly loose stool lasting longer than four weeks. A patient history and physical examination with a complete blood count, C-reactive protein, anti-tissue transglutaminase immunoglobulin A (IgA), total IgA, and a basic metabolic panel are useful to evaluate for pathologies such as celiac disease or inflammatory bowel disease. More targeted testing should be based on the differential diagnosis. When the differential diagnosis is broad, stool studies should be used to categorize diarrhea as watery, fatty, or inflammatory. Some disorders can cause more than one type of diarrhea. Watery diarrhea includes secretory, osmotic, and functional types. Functional disorders such as irritable bowel syndrome and functional diarrhea are common causes of chronic diarrhea. Secretory diarrhea can be caused by bile acid malabsorption, microscopic colitis, endocrine disorders, and some postsurgical states. Osmotic diarrhea can present with carbohydrate malabsorption syndromes and laxative abuse. Fatty diarrhea can be caused by malabsorption or maldigestion and includes disorders such as celiac disease, giardiasis, and pancreatic exocrine insufficiency. Inflammatory diarrhea warrants further evaluation and can be caused by disorders such as inflammatory bowel disease, Clostridioides difficile, colitis, and colorectal cancer.
Topics: Adult; Celiac Disease; Chronic Disease; Diagnosis, Differential; Diarrhea; Humans; Immunoglobulin A; Inflammatory Bowel Diseases; Malabsorption Syndromes
PubMed: 32293842
DOI: No ID Found -
Gastroenterology Sep 2022The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that... (Review)
Review
The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldigestion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.
Topics: Blind Loop Syndrome; Breath Tests; Humans; Intestine, Small; Irritable Bowel Syndrome; Malabsorption Syndromes
PubMed: 35398346
DOI: 10.1053/j.gastro.2022.04.002 -
Current Gastroenterology Reports Jan 2019To critically review recent (past 3 years) literature on the definition, diagnosis, and management of small intestinal bacterial overgrowth (SIBO). (Review)
Review
PURPOSE OF REVIEW
To critically review recent (past 3 years) literature on the definition, diagnosis, and management of small intestinal bacterial overgrowth (SIBO).
RECENT FINDINGS
While various series continue to illustrate the occurrence of SIBO in disease states where well-known risk factors for its occurrence are present (hypochlorhydria, disorders of intestinal structure or motor function, pancreatic insufficiency, and chronic liver disease, for example), the current challenge is in defining the limits of SIBO. Is SIBO truly common among those with "functional" gastrointestinal symptoms where there is no evidence of maldigestion or malabsorption; the original hallmarks of SIBO? Our attempts to address this question continue to be hampered by the limitations of our diagnostic tool kit. There is hope-the application of modern molecular techniques to the study of the small intestinal microbiome, together with some innovative sampling techniques, such as real-time intestinal gas sampling, may soon allow us to truly define the spectrum of SIBO. SIBO, once removed from its original confines as a cause of malabsorption syndrome, has proven to be an elusive and moving target. Only the most rigorous studies employing validated methodologies will finally corral this mysterious entity.
Topics: Blind Loop Syndrome; Breath Tests; Humans
PubMed: 30645678
DOI: 10.1007/s11894-019-0671-z -
Seminars in Respiratory and Critical... Dec 2019Optimal nutrition support has been integral in the management of cystic fibrosis (CF) since the disease was initially described. Nutritional status has a clear... (Review)
Review
Optimal nutrition support has been integral in the management of cystic fibrosis (CF) since the disease was initially described. Nutritional status has a clear relationship with disease outcomes, and malnutrition in CF is typically a result of chronic negative energy balance secondary to malabsorption. As the mechanisms underlying the pathology of CF and its implications on nutrient absorption and energy expenditure have been elucidated, nutrition support has become increasingly sophisticated. Comprehensive nutrition monitoring and treatment guidelines from professional and advocacy organizations have unified the approach to nutrition optimization around the world. Newborn screening allows for early nutrition intervention and improvement in short- and long-term growth and other clinical outcomes. The nutrition support goal in CF care includes achieving optimal nutritional status to support growth and pubertal development in children, maintenance of optimal nutritional status in adult life, and optimizing fat soluble vitamin and essential fatty acid status. The mainstay of this approach is a high calorie, high-fat diet, exceeding age, and sex energy intake recommendations for healthy individuals. For patients with exocrine pancreatic insufficiency, enzyme replacement therapy is required to improve fat and calorie absorption. Enzyme dosing varies by age and dietary fat intake. Multiple potential impediments to absorption, including decreased motility, altered gut luminal bile salt and microbiota composition, and enteric inflammation must be considered. Fat soluble vitamin supplementation is required in patients with pancreatic insufficiency. In this report, nutrition support across the age and disease spectrum is discussed, with a focus on the relationships among nutritional status, growth, and disease outcomes.
Topics: Adult; Child; Cystic Fibrosis; Disease Progression; Energy Intake; Enzyme Replacement Therapy; Exocrine Pancreatic Insufficiency; Humans; Infant, Newborn; Malabsorption Syndromes; Malnutrition; Neonatal Screening; Nutritional Status; Nutritional Support; Risk
PubMed: 31659726
DOI: 10.1055/s-0039-1696726 -
Nutrients Apr 2021Numerous disorders can alter the physiological mechanisms that guarantee proper digestion and absorption of nutrients (macro- and micronutrients), leading to a wide... (Review)
Review
Numerous disorders can alter the physiological mechanisms that guarantee proper digestion and absorption of nutrients (macro- and micronutrients), leading to a wide variety of symptoms and nutritional consequences. Malabsorption can be caused by many diseases of the small intestine, as well as by diseases of the pancreas, liver, biliary tract, and stomach. This article provides an overview of pathophysiologic mechanisms that lead to symptoms or complications of maldigestion (defined as the defective intraluminal hydrolysis of nutrients) or malabsorption (defined as defective mucosal absorption), as well as its clinical consequences, including both gastrointestinal symptoms and extraintestinal manifestations and/or laboratory abnormalities. The normal uptake of nutrients, vitamins, and minerals by the gastrointestinal tract (GI) requires several steps, each of which can be compromised in disease. This article will first describe the mechanisms that lead to poor assimilation of nutrients, and secondly discuss the symptoms and nutritional consequences of each specific disorder. The clinician must be aware that many malabsorptive disorders are manifested by subtle disorders, even without gastrointestinal symptoms (for example, anemia, osteoporosis, or infertility in celiac disease), so the index of suspicion must be high to recognize the underlying diseases in time.
Topics: Anemia; Humans; Infertility; Intestinal Absorption; Intestinal Mucosa; Intestine, Large; Intestine, Small; Malabsorption Syndromes; Nutrients; Osteoporosis
PubMed: 33920345
DOI: 10.3390/nu13041254