JH IM Board Review - Disorders of the Small and Large Intestine I Flashcards
Diseases that affect the intestinal system are likely to interfere with at least one of these 2 functions and lead to problems with:
- Motility.
2. Malabsorption.
Diarrhea - General principles - Definition:
Incr. in fluidity, frequency, or volume of stool output.
==> Usually results in increased daily stool weight (>200g/day).
Diarrhea can be described by many features:
- Osmotic vs secretory.
- Bloody vs nonbloody.
- Inflammatory vs non inflammatory.
- Steatorrhea vs normal fat content.
- Infectious vs non infectious.
5 Mechanisms of diarrhea:
- Osmotic.
- Secretory.
- Abnormal motility.
- Abnormal mucosa/Exudative.
- Anorectal dysfunction.
Osmotic - Comments:
- Small stool volume.
- Osmolar gap present.
- Stops with fasting.
- Stool pH <6.
Secretory - Comments:
- Large volume of stool.
- No osmolar gap.
- Persistent diarrhea with fasting.
Abnormal motility - Comments:
Bacterial overgrowth motility usually secondary to decreased motility.
Abnormal mucosa/ exudative - Comments:
Volume can be small or large.
Anorectal dysfunction:
Small volume of stools.
Osmotic - Examples:
- Maldigestion of carbs (eg lactose, fructose).
- Ingestion of nonabsorbed solutes (eg mannitol, sorbitol).
- Ingestion of poorly absorbed salts (magnesium, hydroxide).
Secretory - Examples:
- Bacterial toxins (eg cholera, E.coli).
- Hormonal secretagogues (Eg VIP, serotonin).
- Gastric hypersecretion (eg Z-E).
- Laxatives (eg senna, phenolphthalein).
- Bile salt malabsorption.
Abnormal motility/exudative - Examples:
- IBD.
- Bacterial pathogens (eg Salmonella, Shigella).
- Vasculitis.
- Radiation enteritis.
- Severe diverticulitis.
- Ischemic injury.
Anorectal dysfunction - Examples:
- Neurologic disease.
- Postsurgical complication.
- IBD.
Osmotic diarrhea - Features:
- Diarrhea stops when oral intake stops.
2. Volume is usually LESS THAN 1lt/day.
Altered motility - INCREASED:
- Causes decreased contact time between the gut and digesting food (chyme).
- Leads to less absorption and large amounts of fluid delivered to the colon.
Altered motility - Decreased motility:
- Causes bacterial overgrowth.
2. Leads to impaired bile salt malabsorption.
Altered mucosa and exudative diarrhea:
- Inflamed or ulcerated mucosa permits mucus, blood, and pus to leak into lumen.
- Diarrhea can result directly from the increased osmotic load, increased motility (stimulation of the enteric nervous system), or secretion of the products of inflammation.
- Stool volume can be large or small, depending on the part of the bowel affected.
BLOODY diarrhea can be related to:
- Campylobacter.
- Shigella.
- Salmonella.
- E.coli.
- Amebiasis.
- IBD.
- Malignancy.
- Adenocarcinoma.
- Colitis (ischemic or infectious).
Anorectal dysfunction or injury:
- Leads to the inability to retain feces.
2. Characterized by fecal incontinence and small-volume stools.
Most diarrheal illnesses have more than …?
One mechanism of stool generation (eg diseases of malabsorption).
Acute diarrhea:
- Usually self-limited (shorter than 4 weeks’ duration).
- Most cases infectious.
- Consider medications (eg laxatives, Mg-containing antacids, PPIs, colchicine, furosemide).
If abdominal pain and bloody diarrhea occur together in a patient older than 50 or with known vascular disease …?
Consider ISCHEMIC COLITIS.
Chronic diarrhea - Lasts:
Longer than 4 weeks.
Steatorrhea is defined as …?
More than 7g of fat/day over 72h fecal fat collection while on a high-fat diet (100g fat/day).
Associated signs/symptoms that suggest an organic rather than a functional (IBS) cause are:
- Fever.
- Weight loss.
- Arthritis.
- Anemia.
- Signs of malabsorption.
Acute diarrhea in an immune-competent patient does NOT require …?
Evaluation. UNLESS signs of:
- Dehydration.
- Bloody stools.
- Fever.
- Severe abdominal pain.
Selected causes of chronic diarrhea - Infections:
- Amebiasis.
- Giardiasis.
- C.diff.
- HIV enteropathy.
- Yersinia.
- Campylobacter.
- Cryptosporidium.
- Cyclospora.
- Intestinal schistosomiasis.
Selected causes of chronic diarrhea - Inflammatory:
- IBD.
- Microscopic colitis.
- Eosinophilic gastroenteritis.
Selected causes of chronic diarrhea - Hormonal abnormalities/tumors:
- Diabetes.
- Hyperthyroidism.
- Adrenal insufficiency.
- VIPomas.
- Carcinoid syndrome.
- Medullary thyroid cancer.
- Gastrinoma.
- Mastocytosis.
Selected causes of chronic diarrhea - Nonendocrine neoplasms:
- Villous adenoma secreting bicarbonate.
2. Obstructive colon cancer causing impaction and overflow diarrhea of liquid feces.
Selected causes of chronic diarrhea - Steatorrheal causes - maldigestion:
- Pancreatic exocrine insufficiency.
- Bacterial overgrowth.
- Liver disease.
Selected causes of chronic diarrhea - Steatorrheal causes - mucosal malabsorption:
- Celiac sprue.
- Tropical sprue.
- Whipple.
- Ischemia.
Selected causes of chronic diarrhea - Structural:
- Bile salt diarrhea after ileal resection.
- Vagotomy.
- Short bowel syndrome.
Selected causes of chronic diarrhea - Osmotic:
- Laxatives (Mg).
- Carb enzyme deficiencies (eg lactase).
- Sorbitol.
- Lactulose ingestion.
Selected causes of chronic diarrhea - Functional:
IBS.
Selected causes of chronic diarrhea - Anorectal dysfunction:
Neurologic.
Stool electrolytes (Na and K) for calculating osmolar gap:
Osmolar gap = 290 - (Na + K) x 2.
If >40 ==> OSMOTIC diarrhea likely.
If <40 ==> SECRETORY diarrhea likely.
Nutrient malabsorption - Proximal small bowel:
- Iron.
- Calcium.
- Folate.
Iron malabsorption:
- Glossitis.
- Pallor.
- Anemia.
- Pica.
Calcium malabsorption:
- Bone pain.
- Tetany.
- Osteoporosis.
Folate malabsorption:
- Glossitis.
- Pallor.
- Anemia.
- Depression.
Nutrient malabsorption - Distal small bowel:
ADEK + B12.
VitA malabsorption:
- Night blindness.
- Hyperkeratosis.
- Corneal ulcers.
VitD malabsorption:
- Bone pain.
- Muscle weakness.
- Osteomalacia.
VitE malabsorption:
- Peripheral neuropathy.
2. Retinopathy.