Malabsorption Flashcards
What is Maldigestion?
impaired breakdown of nutrients, luminal phase (eg pancreatic insufficiency)
What is Malabsorption?
defective mucosal uptake and transport of adequately digested nutrients. Selective or global.
What is Malassimilation?
Encompasses maldigestion and malabsorption
What are the three processes of the luminal phase of absorption?
- Nutrient hydrolysis
- Fat solubilisation
- Lumenal availability
Describe nutrient hydrolysis
- Enzyme deficiency: pancreatic insufficiency
- Enzyme inactivation: ZE syndrome
- Inadequacy of mixing: rapid transit, surgical resection
Describe fat solubilisation
- Decreased bile salts: cholestasis, cirrhosis
- Bile salt deconjugation: bacterial overgrowth
- Bile salt loss: ileal disease or resection
Describe lumenal availability
- Bacterial consumption of nutrients (bacterial overgrowth): B12 deficiency
- Decreased intrinsic factor (pernicious anaemia): B12 deficiency
What are the processes of the mucosal phase of absorption?
- Brush border hydrolysis
- Epithelial transport
Describe brush border hydrolysis
lactase deficiency (post gastroenteritis, alcohol, radiation)
Describe epithelial transport
- Reduced absorptive surface - resection
- Damaged absorptive surface – coeliac disease, tropical sprue, Crohn’s disease, ischaemia
- Infections – Giardia, SIBO
- Infiltration – lymphoma, amyloid
Describe the post-mucosal phase of absorption
Post-absorptive processing – lymphatic obstruction (lymphangectasia, neoplastic, TB)
What are the clinical features of malabsorption?
- Diarrhoea and weight loss despite adequate intake
- Bloating, distention, cramps, borborygmi (bowel sounds)
- Lethargy, malaise
- Symptoms often mild, non-specific
- Malabsorption can be global, or specific nutrients
- Malabsorption syndrome (steatorrhoea, distention, weight loss, oedema) is a RARE presentation
What are the clues in the history?
- Weight loss
- Diarrhea/Steatorrhoea (fat, bile salts)
- Abdominal distension/gas (carbohydrate)= lactose intolerance
- Intestinal “angina” (vasculopathy, impaired circulation to intestine so mesenteric ischaemia)
- Metabolic bone disease (calcium and B12)
- GI surgery
- Pancreatitis
- Cystic fibrosis
- Alcohol
- FHx coeliac
What is the evidence of malnutrition in the skin?
- angular cheilitis (cracking of skin), glossitis
- dermatitis herpetiformis
- oedema
What is the evidence of malnutrition neurologically (B12)?
- Peripheral neuropathy
- Ataxia (posterior column)
- Psychosis, dementia
How can laboratory results indicate malnutrition?
- Microcytosis: iron deficiency (common in coeliac, otherwise suspect GI blood loss)
- Macrocytosis (RBC too big): B12, folate deficiency, but also common in coeliac, alcohol
- Elevated ALP +/- low Ca
- Hypoalbuminaemia (protein malabsorption)
- Evidence of multiple nutritional deficiencies
What are the main causes of malabsorption?
- Coeliac disease
- Pancreatic insufficiency
- Small bowel overgrowth (SIBO)
What are the other causes of malabsorption?
Pernicious anaemia (B12) Bile acid malabsorption (BAM) Intestinal resection Vascular insufficiency Crohn’s disease Lactase deficiency Cholestasis Giardiasis Lymphoma Lymphatic obstruction TB Tropical sprue Whipple’s disease Zollinger Ellison syndrome Amyloid
Describe diagnostic testing for malabsorption
-Testing for malabsorption (eg faecal fat, D-xylose test) rarely used / available
-Unless strong pointers to one cause, investigate non-invasively for the 3 commonest causes first
=Tissue Transglutaminase (TTG) – Coeliac disease
=Faecal elastase – Pancreatic insufficiency
=Glucose H2 breath test - SIBO
-Then if clinically suspected move on to more targeted investigation
What other investigations are there for malabsorption?
- Stool microbiology (Giardia)
- Faecal calprotectin (Crohn’s)
- 7alpha-cholestenone or SeHCAT test (Bile acid malabsorption)
- Lactose H2 breath test
- Small intestinal biopsy (coeliac, Giardia, Crohn’s, Whipples, tropical sprue, lymphangectasia, lymphoma)
- Small bowel imaging (BaFT, MRI, Capsule)
- CT/CT angiogram (pancreatic disease, mesenteric ischaemia
What is Coeliac Disease?
Small bowel disorder characterized by: -mucosal inflammation -villous atrophy -crypt hyperplasia which occur upon exposure to dietary gluten and which demonstrate improvement after withdrawal of gluten from the diet.
What are the possible causes of coeliac disease?
-Genetic predisposition – HLA DQ2, DQ8 (25% population vulnerable)
-Exposure to gluten (gliaden) in wheat, barley, rye
-Gliaden-reactive T lymphocytes
-Tissue transglutaminase antibodies
=Enteropathy
=Prevalence up to 1/100
=Many subclinical or asymptomatic
- Clinically overt
- Undiagnosed, silent
- Latent (potential)
What are the clinical symptoms of coeliac disease?
- Diarrhoea
- Anaemia
- Dyspepsia
- Abd pain, bloating
- Weight loss
- Mouth ulcers
- Fatigue
- Neuropsychiatric symptoms
What is the classic presentation of coeliac disease (historical)?
- Childhood
- FTT / Weight loss
- Short stature
- Malnutrition
- Steatorrhoea
- Delayed puberty
- Osteomalacia
- Myopathy
What are the clues on investigation for coeliac disease?
- Anaemia (microcytic, macrocytic)
- Iron, folate deficiency
- Macrocytosis without anaemia
- Hyposplenic blood film
- Low calcium, elevated Alk Phos
- Raised transaminases
- Hypoalbuminaemia
What other disease is coeliac disease associated with?
Osteoporosis Infertility Dermatitis herpetiformis Lymphocytic colitis Ulcerative jejunitis Lymphoma Type1 Diabetes Thyroid disease Autoimmune liver disease Sjogren’s syndrome Down’s syndrome Cerebellar ataxia Other malignancies
Describe diagnosis of coeliac disease
Serological markers
-Anti-tissue transglutaminase antibody (IgA) (TTG) Sensitivity and specificity >95%
=Anti-endomysial antibody (IgA)
=Anti-gliadin antibody (IgA, IgG)
Small intestinal biopsy
What endoscopic changes can be seen in coeliac disease?
- Scalloping
- Loss of Kerkring’s folds
- Mosaic pattern
What is the treatment for coeliac disease?
- Gluten free diet (life-long)
- Dietician
- Nutritional supplements
- Screen for complications – bone disease
- Very rarely, need for immunosuppressant medication for refractory cases
Describe Pancreatic exocrine insufficiency (PEI)
- Pancreas produces 1.5L/day of bicarbonate and enzyme-rich fluid
- Enzymes for digestion of fat, protein, CHO
- Lipolytic activity declines first so fat absorption mainly affected
- Overt clinical consequences unlikely unless 90% of function lost
- Steatorrhoea, weight loss, vitamin deficiency (A,D,E,K), also more minor symptoms
What are the causes of PEI?
- Chronic pancreatitis
- Pancreatic cancer
- Cystic fibrosis (obstruction)
- Haemochromatosis
- Pancreatic resection
- Gastric resection
What are the causes of chronic pancreatitis?
- Alcohol – 80% present with pain
- Duct obstruction – tumours, stones
- Cystic fibrosis, other genetic causes
- Systemic disease eg SLE= atrophy
- Autoimmune (IgG4) pancreatitis
Describe cystic fibrosis
- Autosomal recessive, CFTR gene
- Impairment in bicarbonate and chloride secretion – thick sticky mucus
- Pancreatic involvement most common GI problem, esp in more severe genotypes
- 85% affected, starts v early.
- Commonly leads to PEI in childhood
How is PEI diagnosed?
-Risk factors (alcohol, CF)
-Symptoms
-Pancreatic imaging (CT, MRI)
-Tests of exocrine pancreatic function
=Direct – eg Secretin stimulation tests (sensitive but cumbersome)
=Indirect – eg Faecal elastase, Pancreolauryl (only reliably detect moderate to severe PEI)
What is the treatment for PEI?
- Pancreatic enzyme replacement
- Taken with meals and snacks
- Gastric acid suppression
- Vitamin supplements
Describe Small Intestinal bacterial overgrowth (SIBO)
- Normally 105 to 109 bacteria/ml present in distal small bowel
- Colon has up to 1012 bacteria/ml
- Mostly Gram- aerobic bacteria in ileum, Gram+ anaerobic bacteria in colon
- In bacterial overgrowth this balance is lost
- Increasingly recognised as a feature in other conditions – liver disease, IBS, obesity, CF, coeliac disease
- Overestimated how many patient have this
What are the causes of bacterial overgrowth?
-Stasis
– Strictures
=Crohn’s disease
=Tuberculosis
–Hypomotility
=Old age
=Opiate analgesics
=Diabetes
=Systemic sclerosis
-Blind loops, Diverticulae
-Immunodeficiency
-?Obesity
What are blind loops?
- Stagnant loop out of continuity with gut so growth
- Billroth 2 partial gastrectomy
- Gastric bypass
What are the consequences of bacterial overgrowth?
- Vitamin B12 malabsorption
- Bile acid deconjugation
- Intraluminal protein utilization
- Brush border damage
- Ulceration of mucosa
- Bowel dysmotility
Describe diagnosis of SIBO
- Quantitative culture of jejunal fluid is the gold standard (> 105/mL is abnormal)
- Glucose/Hydrogen breath test more practical (not accurate)
- Small bowel radiology to look for anatomical abnormalities
What is the treatment for SIBO?
- Treatment with 2 weeks of antibiotics e.g. tetracycline, ciprofloxacin, rifaximin
- Often needs repeat treatment
Describe Bile Acid Malabsorption (BAM)
- Bile acids specifically absorbed in ileum
- Cause secretory diarrhoea in colon
- Affected by ileal disease or resection
- Also impaired in post- cholecystectomy, rapid transit and other malabsorptive states
- Primary BAM may reflect over-production rather than malabsorption (receptors defective)
What are the types of bile acid malabsorption?
-Type 1 =Ileal disease or resection -Type 2 =Idiopathic -Type 3 =Assoc with cholecystectomy, rapid transit, coeliac, SIBO, chronic pancreatitis
What is used to investigate BAM?
Serum 7-alpha cholestenone
SeHCAT retention
What is the treatment for BAM?
Cholestyramine
Colesevelam
Describe Giardia lamblia
-Non-invasive pathogen
-Malabsorption due to multiple factors
=Brush border damage
=Reduction in absorptive surface
=Bile acid utilization
=Induction of hypermotility
=Enterotoxin
-Treatment of choice is metronidazole
Which other parasites cause malabsorption?
-Protozoa =Isospora belli =Cryptosporidium =Microsporidia (Enterocytozoon bieneusi) -Tapeworms (blood loss and iron deficiency) =Taenia saginata (beef tapeworm) =Hymenolepis nana (dwarf tapeworm) =Diphyllobothrium latum (fish tapeworm) -Nematodes =Strongyloides =Capilliarasis
Describe Whipple’s disease
- Uncommon bacterial infection in older men
- Caused by Tropheryma whippleii
- Presents with diarrhoea, arthritis, fever, cough, headache, muscle weakness
- Intestinal mucosa is infiltrated by foamy macrophages containing PAS-positive material
- Antibiotic therapy for months to years.
