Diarrhea, Chronic

Key Features

Essentials of Diagnosis

• Diarrhea present for > 4 weeks

• Before embarking on extensive work up, common causes should be excluded, including medications, chronic infections, and irritable bowel syndrome

• Classification

  • Medications

  • Osmotic diarrhea

  • Secretory conditions

  • Inflammatory conditions

  • Malabsorption conditions

  • Motility disorders

  • Chronic infections

  • Systemic disorders

General Considerations

• Medications that can commonly cause diarrhea include

  • Cholinesterase inhibitors

  • Selective serotonin reuptake inhibitors

  • Angiotensin II-receptor blockers

  • Proton pump inhibitors

  • Nonsteroidal anti-inflammatory drugs

  • Metformin

  • Allopurinol

  • Orlistat

• Osmotic diarrheas

  • Commonly caused by carbohydrate malabsorption, laxative abuse, and malabsorption syndromes

  • Resolve during fasting

• Secretory diarrhea

  • Caused by increased intestinal secretion or decreased absorption

  • There is little change in stool output during fasting

• Inflammatory conditions (ulcerative colitis, Crohn disease) often have diarrhea present

• The major causes of malabsorption are small intestinal mucosal diseases, intestinal resections, lymphatic obstruction, small intestinal bacterial overgrowth, and pancreatic insufficiency

• Motility disorders are secondary to systemic disorders, radiation enteritis, or surgery that lead to rapid transit or to stasis of intestinal contents with bacterial overgrowth, malabsorption

• Immunocompromised patients are susceptible to Microsporidia, Cryptosporidium, cytomegalovirus, Isospora belli, Cyclospora, and Mycobacterium avium-intracellulare infections

• Chronic systemic conditions such as thyroid disease, diabetes mellitus, and collagen vascular disorders may cause diarrhea through alterations in motility or intestinal absorption

Demographics

• Lactase deficiency

  • Occurs in 75% of nonwhite adults and 25% of whites

  • May be acquired with viral gastroenteritis, medical illness, or gastrointestinal surgery

Clinical Findings

Symptoms and Signs

• Osmotic diarrheas

  • Abdominal distention

  • Bloating

  • Flatulence due to increased colonic gas production

• Secretory diarrhea

  • High-volume (> 1 L/day) watery diarrhea

  • Dehydration

  • Electrolyte imbalance

• Inflammatory conditions

  • Abdominal pain

  • Fever

  • Weight loss

  • Hematochezia

  • Pus may be present

• Malabsorption syndromes

  • Weight loss

  • Osmotic diarrhea

  • Malodorous stool

  • Steatorrhea

  • Nutritional deficiencies

Differential Diagnosis

• Common

  • Irritable bowel syndrome

  • Parasites

  • Caffeine

  • Laxative abuse

• Osmotic

  • Lactase deficiency

  • Medications: antacids, lactulose, sorbitol, olestra

  • Factitious: magnesium-containing antacids or laxatives

• Secretory

  • Hormonal: Zollinger-Ellison syndrome (gastrinoma), carcinoid, VIPoma, medullary thyroid carcinoma, adrenal insufficiency

  • Laxative abuse: cascara, senna

  • Medications

  • Microscopic colitis

• Inflammatory conditions

  • Inflammatory bowel disease

  • Cancer with obstruction and pseudodiarrhea

  • Radiation colitis

• Malabsorption

  • Small bowel: celiac disease, Whipple disease, tropical sprue, eosinophilic gastroenteritis, small bowel resection, Crohn disease

  • Lymphatic obstruction: lymphoma, carcinoid, tuberculosis, M avium-intracellulare infection, Kaposi sarcoma, sarcoidosis, retroperitoneal fibrosis

  • Pancreatic insufficiency: chronic pancreatitis, cystic fibrosis, pancreatic cancer

  • Bacterial overgrowth, eg, diabetes mellitus

  • Reduced bile salts: ileal resection, Crohn disease, postcholecystectomy

• Motility disorders

  • Irritable bowel syndrome

  • Postsurgical: vagotomy, partial gastrectomy, blind loop with bacterial overgrowth

  • Systemic disease: diabetes mellitus, hyperthyroidism, scleroderma

  • Caffeine or alcohol use

• Chronic infections

  • Parasites: giardiasis, amebiasis, strongyloidiasis

Diagnosis

Laboratory Tests

• Obtain complete blood count, serum electrolytes, liver biochemical tests, calcium, phosphorus, ...