Diarrhea and Malabsorption Internal Medicine Update & Review Course Don Schoch, M.D. February 10, 2018

Conflicts None

Incidence Acute diarrhea in US 0.65 episodes per person per year Chronic diarrhea 5% of the US population per year

Commonly considered a decrease in the consistency of the stool Definition A symptom, not a disease General criteria Commonly considered a decrease in the consistency of the stool Consistency is determined by the ratio of the water binding ability of stool solids to total stool water. Stool solids: dietary fiber and bacterial cell walls Specific criteria (not absolute) More than three bowel movements a day Stool weight over 200 grams a day Small bowel delivers from 1 to 1.5 liters of water to the colon a day. Normal water absorption is 90%.

Pseudodiarrhea Formerly hyperdefecation Definition More than 3 bowel movements a day Normal stool weight May be more common that chronic diarrhea Seen with irritable bowel syndrome, anorectal disorders (proctitis), and fecal impaction

Determine if patient is having true diarrhea Take a detailed history Patients use the term diarrhea to describe a variety of symptoms Bristol stool chart is helpful Other possibilities Pseudodiarrhea Fecal incontinence Fictitious diarrhea

Determine if patient is having true diarrhea (cont.) Evaluation Check abdominal roentgenogram (KUB) Ask for an assessment of stool burden Stool chart in hospital Have patient use a “hat” Record time, volume, consistency

Pathophysiology Excess stool water Osmotic diarrhea Normal colonic mucosa can’t maintain an osmotic gradient Increased non absorbed stool contents increases stool water Common agents causing this Poorly absorbed anions and cations Magnesium, phosphate, sulfates Poorly absorbed sugars Mannitol, sorbitol Polyethylene glycol (GoLYTLEY, MiraLAX) Used clinically

Pathophysiology (cont.) Osmotic diarrhea Clinical feature Stops when fasting or when ingestion of agent stops

Secretory diarrhea Mechanism Net secretion of anions Net inhibition of Na absorption Causes Infection is the most common cause. Complex diarrhea Most causes of diarrhea are a combination Diarrhea is rarely just osmotic or secretory.

Clinical classification Time course Acute Less than four weeks Usually infectious Viral being most common Chronic Fatty diarrhea Inflammatory diarrhea Watery diarrhea Secretory Osmotic

Evaluation Acute Most patients do not require evaluation or intervention. Exceptions Poor oral intake Vomiting Immunocompromised

Initial evaluation When it lasts more than a few days or is complicated Labs CBC Renal panel Stool studies Fecal leukocytes Stool cultures Limited value in outpatients with negative fecal leukocytes

Evaluation (cont.) Acute diarrhea Clostridium difficile toxin History of antibiotics Institutional setting Cryptosporidium and Giardia lamblia ELISA tests for antigens Abdominal roentgenogram (KUB)

Chronic diarrhea More complex than acute diarrhea Rely on the categories to focus the evaluation Stool studies (partial list) Stool occult blood testing Osmotic gap Stool electrolytes Fecal leukocytes Stool fat Qualitative Quantitative Stool weight

Osmotic gap 290 mOsm/kg – 2(Na + K) Small gap (< 50 mOm/kg) Poorly absorbed electrolytes Large gap (>100 mOm/kg) Ingestion of a poorly absorbed substance Doesn’t involve measuring stool osmolality

Norovirus Causes acute diarrhea Highly contagious Sources Eating contaminated food and drinks Touching contaminated surfaces Person to person contact

Norovirus (cont.) The leading cause of illness from contaminated food Including raw shellfish Common cause of epidemics in the US Notoriety due to recent cruise ship outbreaks Also seen in day care, camps, schools, health care facilities Clinical features Diarrhea, nausea, abdominal cramps, and vomiting Lasts 24 to 48 hours No specific treatment is available.

55 year old female presents with abrupt onset of profuse watery diarrhea and occasional fecal incontinence for six weeks. She doesn’t have rectal bleeding. She is a runner. She has been using naproxen for tendonitis. PMH: Neg., Meds – naproxen only PE: unremarkable, Hemoccult® negative stool Labs: CBC, CMP, TSH - negative. Stools studies all negative, including: fecal leukocytes, qualitative stool for fecal fat, culture, Crypto. and Giardia stool antigens, C. dif.

The next best test is: Magnetic resonance enterography (small bowel imaging) Stool osmotic gap Stool for ova and parasites (warm purged stool is available in your lab) Colonoscopy with random biopsies Empiric course of Cipro

55 year old female presents with abrupt onset of profuse watery diarrhea and occasional fecal incontinence for six weeks. She doesn’t have rectal bleeding. She is a runner. She has been using naproxen for tendonitis. PMH: Neg., Meds – naproxen only PE: unremarkable, Hemoccult negative stool Labs: CBC, CMP, TSH - negative. Stools studies all negative, including: fecal leukocytes, qualitative stool for fecal fat, culture, Crypto. and Giardia stool antigens, C. dif.

Enterohemorrhagic Escherichia coli (EIEC) Causes acute hemorrhagic colitis Mainly E. coli O157:H7 Prevalence 15% to 36% of hemorrhagic colitis Epidemiology Most often caused by eating hamburger Cattle are the most important reservoir

Enterohemorrhagic Escherichia coli (cont.) Clinical findings Bloody diarrhea (95% of patients), nonbloody diarrhea, hemolytic-uremic syndrome (HHS), and thrombotic thrombocytopenic purpura (TTP) HUS Acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia

Enterohemorrhagic Escherichia coli (cont.) Treatment No studies to support efficacy of antibiotic treatment Some data to support an association between antibiotic use and HUS Routine use of antibiotics is not recommended Follow for development of HUS

Malabsorption Challenge is to recognize the subtle presentation Bloating Change in bowel habits Nutrient deficiencies Examples: B12, iron, calcium, magnesium

Pathophysiology Solubilization Digestion Liberation of substrates B12 bound to foods Chemical changes Changing the charge of iron Mucosal absorption Active & passive

Diseases causing malabsorption Note: Causes are extensive, following is only a partial list, includes only the most common causes Gastric diseases Gastric bypass Pancreatic diseases Pancreatic insufficiency Pancreatic tumors Discuss supplements and monitoring in Roux-en-Y gastric bypass patients.

Diseases causing malabsorption (cont.) Intestinal diseases Celiac disease Crohn’s disease Infections Giardia lamblia AIDS Whipple’s disease Small bowel bacterial overgrowth Endocrine Hyperthyroidism Systemic diseases Scleroderma

Fecal elastase-1  The most sensitive and specific indirect test of pancreatic function. An enzymatic product of pancreatic secretion Remains relatively stable during transport through the gastrointestinal tract. Levels <200 mcg/g is considered abnormal Between 200 mcg/g and 250 mcg/g may be considered borderline.

Fecal elastase-1  Sensitivity Mild: 63% Moderate: 100% Severe: 100% Specificity 93% Dilution can decrease the level Seen in watery diarrhea