Diarrhea
GENERAL PRINCIPLES
• Acute diarrhea consists of abrupt onset of #8805;3 unformed bowel movements in conjunction with associated symptoms such as tenesmus, fecal urgency, increased flatulence, nausea, or vomiting.37 Infectious agents, toxins, and drugs are the major causes of acute diarrhea.
In hospitalized patients, pseudomembranous colitis, antibiotic- or drug-associated diarrhea, and fecal impaction should be considered.38• Chronic diarrhea consists of passage of loose stools with or without increased stool frequency and urgency for more than 4 weeks.39
DIAGNOSIS
• Most acute infectious diarrheal illnesses last less than 24 hours and are likely caused by viruses; therefore, stool studies are unnecessary in short-lived episodes without fever, dehydration, or presence of blood or pus in the stool.38
• Stool cultures, Clostridioides difficile toxin assay, ova and parasite examinations, and sigmoidoscopy or colonoscopy may be warranted in patients with severe, prolonged, atypical symptoms, or in immunocompromised patients.
• The fecal osmotic gap [290-2(stool Na+ + stool K+)] can be calculated in patients with chronic diarrhea and voluminous watery stools. The osmotic gap is lt;50 mOsm/kg in secretory diarrhea but gt;125 mOsm/kg in osmotic diarrhea.
• A positive fecal occult blood test or fecal leukocyte test suggests inflammatory diarrhea.
• Steatorrhea is traditionally diagnosed by demonstration of fat excretion in stool of gt;7 g/d in a 72-hour stool collection while the patient is on a 100-g/d fat diet. Sudan staining of a stool specimen is an alternate test; gt;100 fat globules per high-power field (HPF) is abnormal.
• Laxative screening should be considered when chronic diarrhea remains undiagnosed.
Clinical Presentation
• Acute diarrhea
î Viral enteritis and bacterial infections with Escherichia coli and Shigella, Salmonella, Campylobacter, and Yersinia spp.
constitute the most common causes.î Pseudomembranous colitis is usually seen in the setting of antimicrobial therapy and is caused by toxins produced by C. difficile.40
î Giardiasis is confirmed by identification of Giardia lamblia trophozoites in the stool, in duodenal aspirate, or in small bowel biopsy specimens. A stool immunofluorescence assay is also available for rapid diagnosis.
î Amebiasis may cause acute diarrhea, especially in travelers to areas with poor sanitation and in men who have sex with men. Stool examination for trophozoites or cysts of Entamoeba histolytica or a serum antibody test confirms the diagnosis.
î Medications that can cause acute diarrhea include laxatives, antacids, cardiac medications (e.g., digitalis, quinidine), colchicine, and antimicrobial agents; symptoms typically respond to discontinuation.
î Graft-versus-host disease should be considered when diarrhea develops after organ transplantation, especially bone marrow transplantation; sigmoidoscopy with biopsies should be pursued to confirm this diagnosis.41
• Chronic diarrhea: After a careful history, a thorough physical examination, and routine laboratory tests, chronic diarrhea can typically be classified into one of the following categories: watery diarrhea (secretory or osmotic), inflammatory diarrhea, or fatty diarrhea (steatorrhea).39
TREATMENT
• Adequate hydration, including IV hydration in severe cases, is the most important treatment in managing diarrheal diseases. Oral rehydration salt (ORS) solutions are World Health Organization (WHO) recommended for optimized water absorption. High-sugar beverages should be avoided because they can exacerbate fluid losses in the absence of sufficient salt. Commercially prepared solutions are available in developed countries (e.g., Pedialyte).
• Antibiotic-associated diarrhea and C. difficile infections can be prevented by restricting high-risk antibiotic use and prescribing antibiotics based on sensitivity analysis.
• Symptomatic therapy is offered in simple self-limiting GI infections where diarrhea is frequent or troublesome, while diagnostic workup is in progress, when specific management fails to improve symptoms, and/or when a specific etiology is not identified.
î Loperamide, opiates (tincture of opium, belladonna, and opium capsules), and anticholinergic agents (diphenoxylate and atropine [Lomotil]) are the most effective nonspecific antidiarrheal agents.
î Pectin and kaolin preparations (bind toxins) and bismuth subsalicylate (antibacterial properties) are also useful in symptomatic therapy of acute diarrhea.
î Bile acid-binding resins (e.g., cholestyramine) are beneficial in bile acid-induced diarrhea.
î Octreotide is useful in hormone-mediated secretory diarrhea but can also be of benefit in refractory diarrhea.
Medications
• Empiric antibiotic therapy is only recommended in patients with moderate to severe disease and associated systemic symptoms while awaiting stool cultures. Antibiotics can increase the possibility of hemolytic-uremic syndrome associated with Shiga toxin-producing E. coli infections (E. coli O157:H7), especially in children and the elderly.42
• Oral vancomycin or fidaxomicin are the antibiotics of choice for pseudomembranous colitis. Metronidazole can be used intravenously together with vancomycin in fulminant disease with hypotension, shock, or ileus. Fecal microbiota transplant is a novel treatment option.43
• Symptomatic amebiasis is treated with metronidazole, followed by paromomycin or iodoquinol to eliminate cysts.
• Therapy for giardiasis consists of metronidazole or tinidazole, with quinacrine representing an alternative agent.
SPECIAL CONSIDERATIONS
• Opportunistic agents, including cryptosporidium, microsporidium, cytomegalovirus (CMV), Mycobacterium avium complex, and Mycobacterium tuberculosis, may cause diarrhea in patients with advanced HIV (CD4 counts lt;50 cells#8725;#956;L). However, C. difficile may be the most commonly identified bacterial pathogen.44
• Other causes of diarrhea in this population include sexually transmitted infections (e.g., syphilis, gonorrhea, chlamydia, herpes simplex virus [HSV]) and non-sexually transmitted infections (e.g., amebiasis, giardiasis, salmonellosis, shigellosis). Intestinal lymphoma and Kaposi sarcoma can also cause diarrhea.
• Stool studies (ova and parasites, culture), endoscopic biopsies, and serologic testing may assist in diagnosis. Management consists of specific therapy if pathogens are identified; symptomatic measures may be of benefit in idiopathic cases.
• Severe C. difficile infection can precipitate toxic megacolon, which necessitates surgical consultation.