Case Report

All of the following necessitate sending bacterial stool cultures in patients with diarrhea for 2 days severe enough to keep them home from work except

A. age >75
B. bloody stools
C. dehydration
D. recent lung transplantation
E. temperature >38.5°C.
Answer / Explanation:

The answer is C.

Most causes of acute diarrhea are infectious. Dehydration is a feature of all infectious diarrheas and does not suggest bacterial etiology. Fever and bloody diarrhea are more suggestive. Immunocompromised hosts and the elderly are at greater risk for developing bacteremia and sepsis with certain pathogens, and they also may be less likely to have symptoms suggesting a bacterial pathogen. Stool cultures are typically sent in these populations unless symptoms are mild.


For Your Reference:

Related Topic:–Acute Diarrhea

Acute Diarrhea

Viruses are the most common cause of acute gastroenteritis in developing and developed countries. Bacterial and parasitic enteric infections are discussed in Chapters 40 and 41. Of the viral agents causing enteric infection, rotavirus, a 67-nm double-stranded RNA virus with at least eight serotypes, is the most common. As with most viral pathogens, rotavirus affects the small intestine, causing voluminous watery diarrhea without leukocytes or blood. In the United States, rotavirus mainly affects infants between 3 and 15 months. Peak incidence in the United States is in the winter with sporadic cases occurring at other times. The virus is transmitted via the fecal-oral route and survives for hours on hands and for days on environmental surfaces.
Rotavirus Infection

The incubation period for rotavirus is 24–48 hours. Vomiting is the first symptom in 80–90% of patients, followed within 24 hours by low-grade fever and watery diarrhea. Diarrhea usually lasts 4–8 days but may last longer in young infants or immunocompromised patients. The white blood cell count is rarely elevated. The stool sodium level is usually less than 40 mEq/L. As patients become dehydrated from unreplaced fecal water loss, they may become hypernatremic. The stool does not contain blood or white cells. Metabolic acidosis results from bicarbonate loss in the stool, ketosis from poor intake, and lactic acidemia from hypotension and hypoperfusion

Replacement of fluid and electrolyte deficits and ongoing losses is critical, especially in small infants. (Oral and intravenous therapy are discussed in Chapter 43.) The use of oral rehydration fluid is appropriate in most cases. The use of clear liquids or hypocaloric (dilute formula) diets for more than 48 hours is not advisable in uncomplicated viral gastroenteritis because starvation depresses digestive function and prolongs diarrhea.

Intestinal lactase levels are reduced during rotavirus infection. Brief use of a lactose-free diet is associated with a shorter period of diarrhea but is not critical to successful recovery in healthy infants. Reduced fat intake during recovery may decrease nausea and vomiting.

Antidiarrheal medications are ineffective (kaolin-pectin combinations) or even dangerous (loperamide, tincture of opium, diphenoxylate with atropine). Bismuth subsalicylate preparations may reduce stool volume but are not critical to recovery. Oral immunoglobulin or specific antiviral agents have occasionally been useful in limiting duration of disease in immunocompromised patients.

Specific identification of rotavirus is not required in every case, especially in outbreaks. Rotavirus antigens can be identified in stool or virus can be seen by scanning electron microscopy. False-positive results (which may actually be nonpathogenic rotavirus) are seen in neonates. Most children are infected with rotavirus more than once, with the first infection being the most severe. Some protective immunity is imparted by the first infection. Prevention of infection occurs primarily by good hygiene and prevention of fecal-oral contamination. The American Academy of Pediatrics issued guidelines in January 2007 recommending the routine use of bovine-based pentavalent rotavirus vaccine to be given orally to infants at 2, 4, and 6 months of age.
Other Viral Infections Causing Acute Diarrhea

Other viral pathogens causing diarrhea in children can be identified in stool by electron microscopy, viral culture, or enzyme-linked immunoassay. Depending on the geographic location, enteric adenoviruses (serotypes 40 and 41) or caliciviruses are the next most common viral pathogens in infants. The symptoms of enteric adenovirus infection are similar to those of rotavirus, but infection is not seasonal and duration of illness may be longer. The Norwalk agent (now called norovirus) is a calicivirus, a small RNA virus that mainly causes vomiting but can also cause diarrhea in older children and adults, usually in common source outbreaks. The duration of symptoms is short, usually 24–48 hours. Other potentially pathogenic viruses include astroviruses, corona-like viruses, and other small round viruses.

Cytomegalovirus rarely causes diarrhea in immunocompetent children but may cause erosive colitis or enteritis in immunocompromised hosts. Cytomegalovirus enteritis is particularly common after bone marrow transplantation and in late stages of HIV infection.
Chronic Diarrhea

Bowel habits are variable, making specific diagnosis of chronic diarrhea difficult. Some infants normally have 5–8 stools daily. A gradual or sudden increase in the number and volume of stools to more than 15 g/kg/d combined with an increase in fluidity should raise a suspicion that an organic cause of chronic diarrhea is present. Diarrhea may result from (1) interruption of normal cell transport processes for water, electrolytes, or nutrients; (2) decrease in the surface area available for absorption secondary to shortened bowel or mucosal disease; (3) increase in intestinal motility; (4) increase in unabsorbable osmotically active molecules in the intestinal lumen; (5) increase in intestinal permeability, leading to increased loss of water and electrolytes; and (6) stimulation of enterocyte secretion by toxins or cytokines. The most common entities causing chronic diarrhea are listed below. Malabsorption syndromes, which also cause chronic or recurrent diarrhea, are considered separately.
Noninfectious Causes of Chronic Diarrhea

Antibiotic Therapy

Diarrhea is reported in up to 60% of children receiving antibiotics. Only a tiny fraction of these patients have C difficile–related pseudomembranous enterocolitis. Eradication of normal gut flora and overgrowth of other organisms may cause diarrhea. Most antibiotic-associated diarrhea is watery, is not associated with systemic symptoms, and decreases when antibiotic therapy is stopped.
Extraintestinal Infections

Infections of the urinary tract and upper respiratory tract (especially otitis media) are at times associated with diarrhea. The mechanism is obscure. Antibiotic treatment of the primary infection, toxins released by infecting organisms, and local irritation of the rectum (in patients with bladder infection) may play a role.

Malnutrition is associated with an increased frequency of enteral infections. Decreased bile acid synthesis, decreased pancreatic enzyme output, decreased disaccharidase activity, altered motility, and changes in the intestinal flora all may cause diarrhea. Severely malnourished children are at higher risk of enteric infections because of depressed immune functions, both cellular and humoral.
Diet and Medications

Overfeeding may cause diarrhea, especially in young infants. Relative deficiency of pancreatic amylase in young infants causes osmotic diarrhea after starchy foods. Fruit juices, especially those high in fructose or sorbitol, produce diarrhea because these osmotically active sugars are poorly absorbed. Intestinal irritants (spices and foods high in fiber) and histamine-containing or histamine-releasing foods (eg, citrus fruits, tomatoes, fermented cheeses, red wines, and scombroid fish) also cause diarrhea.

Laxative abuse in association with eating disorders or Münchausen syndrome by proxy can cause unpredictable diarrhea. A high concentration of magnesium in the stool may indicate overuse of milk of magnesia or other magnesium-containing laxatives. Detection of other laxative preparations in the stool or circulation requires sophisticated analysis not available in most laboratories. A high index of suspicion and careful observation may be required to make this diagnosis.
Allergic Diarrhea

Diarrhea resulting from allergy to dietary proteins is a frequently entertained but rarely proven diagnosis. Gastrointestinal symptoms from protein allergy are more common in infants younger than age 12 months, who may experience mild to severe colitis with diarrhea and rectal bleeding in response to cow's milk protein—either ingested directly or in minute quantities in maternal breast milk. A personal or family history of atopy is common in these infants. Skin testing is not reliable. Double-blind oral challenge with the suspected food under careful observation is necessary to confirm intestinal protein allergy. In the breast-fed infant, maternal avoidance of milk protein may be effective in reducing the signs of colitis. Substituting a protein hydrolysate formula for cow's milk–based formula may reduce symptoms. Allergic colitis in young infants is self-limited, usually disappearing by 8–12 months of age. The condition does not require treatment if the infant is thriving and the colitic symptoms are mild. Colonoscopy is not required for diagnosis, but rectal biopsies, if performed, show mild lymphonodular hyperplasia, mucosal edema, and slight eosinophilia. Allergies to fish, peanuts, and eggs are more likely to be lifelong and more likely to be IgE mediated. Multiple food allergy (more than three) is rare.

Older children may develop a celiac-like syndrome secondary to milk protein with flattening of small bowel villi, steatorrhea, hypoproteinemia, occult blood loss, and chronic diarrhea. Skin testing is not reliable since it detects circulating antibodies, not the T-cell–mediated responses that are probably responsible for food sensitivity reactions. Double-blind oral challenge with the suspected food under careful observation is necessary to confirm intestinal protein allergy. Small bowel biopsy findings are obvious but nonspecific. The diagnosis is often confirmed by dietary trial followed by disappearance of occult blood in the stool and improvement in other symptoms.

Anaphylactic, IgE-mediated reactions to foods can occur. After ingestion, the patient quickly develops vomiting, then diarrhea, pallor, and hypotension. In these cases, skin testing is positive. Food challenges should be undertaken in a setting in which resuscitation can be performed as there is often a progressively more severe reaction with subsequent ingestions. The close association between ingestion and symptoms usually leaves little doubt about the diagnosis.
Chronic Nonspecific Diarrhea

Chronic nonspecific diarrhea is the most common cause of loose stools in thriving children. The typical patient is a healthy child aged 6–20 months who has three to six loose mucoid stools per day during the waking hours. The diarrhea worsens with a low-residue, low-fat, or high-carbohydrate diet and during periods of stress and infection. It clears spontaneously at about age 3½ years (usually coincident with toilet training). No organic disease is discoverable. Possible causes include abnormalities of bile acid absorption in the terminal ileum, incomplete carbohydrate absorption (excessive fruit juice ingestion seems to worsen the condition or in some cases is the primary cause), and abnormal motor function. Family history of functional bowel disease is common. Stool tests for blood, white cells, fat, parasites, and bacterial pathogens are negative.

The following measures are helpful: use of a slightly high-fat (about 40% of total calories), low-carbohydrate, high-fiber diet; avoidance of between-meal snacks; avoidance of chilled fluids, especially fruit juices. Loperamide (0.1–0.2 mg/kg/d in two or three divided doses) is often helpful. Cholestyramine (2–4 g in divided doses) or psyllium agents (1–2 tsp twice daily) are sometimes used.
Secretory Diarrhea

Certain malignancies of childhood (neuroblastoma, ganglioneuroma, metastatic carcinoid, pancreatic VIPoma, or gastrinoma) may secrete substances such as gastrin and vasoactive intestinal polypeptide (VIP) that promote small intestinal secretion of water and electrolytes. Children may present with large-volume, chronic and intermittent watery diarrhea that does not cease when they discontinue oral feedings. Fat malabsorption is not characteristic. The serum potassium level is often low because of stool losses. The hallmark of the diarrhea is that, unlike osmotic and infectious viral diarrheas, the sodium content of stool water is high, usually between 90 and 140 mEq/L of stool. Other signs and symptoms are associated with specific tumors. Neuroblastoma and ganglioneuroma produce elevations in urinary homovanillic acid and vanillylmandelic acid. Metastatic carcinoid produces characteristic flushing and sweating. Gastrinoma may produce multiple duodenal ulcers (Zollinger-Ellison syndrome).

In all secretory diarrheas, a careful radiologic search for a tumor is indicated. Intraendoscopic ultrasound examination may reveal small tumors in the bowel wall or pancreatic head. Bacterial overgrowth of the small bowel in patients with short bowel, cancer chemotherapy, or anatomic abnormalities may be associated with enterotoxins that promote secretory diarrhea. Cholera is the best known bacterial secretory diarrhea. Its enterotoxin stimulates cyclic adenosine monophosphate in the enterocyte, which promotes salt and water secretion.
Infectious Causes of Chronic Diarrhea

Most infections of the GI tract are acute and resolve spontaneously or with specific antibiotic therapy. Organisms most prone to cause chronic or recurrent diarrhea in immunocompetent children are Giardia lamblia, Entameba histolytica, Salmonella spp, and Yersinia.

Chronic diarrhea is common in immune deficiency states, especially IgA deficiency and T-cell abnormalities. The cause of is often common bacterial, viral, fungal, or parasitic organisms usually considered nonpathogenic (rotavirus, Blastocystis hominis, Candida), or unusual organisms (cytomegalovirus, Cryptosporidium, Isospora belli, Mycobacterium spp, microsporidia, and algal organisms such as cyanobacteria).

Between 50% and 60% of patients with idiopathic acquired hypogammaglobulinemia have steatorrhea and intestinal villous atrophy. Lymphonodular hyperplasia of the small intestine is prominent. Patients with congenital or Bruton-type agammaglobulinemia usually have diarrhea and abnormal intestinal morphology. Patients with isolated IgA deficiency have chronic diarrhea, a celiac-like picture, lymphoid nodular hyperplasia, and are prone to giardiasis. Patients with isolated cellular immunity defects, combined cellular and humoral immune incompetence, and HIV infection may have severe chronic diarrhea leading to malnutrition. Often the cause is not found. The incidence of disaccharidase deficiency is high. Chronic granulomatous disease may be associated with intestinal symptoms suggestive of chronic inflammatory bowel disease. A rectal biopsy may reveal the presence of typical macrophages.

Treatment must be directed toward correcting the immunologic defect. Specific treatments are available or are being developed for many of the unusual pathogens causing diarrhea in the immunocompromised host. Thus, a vigorous diagnostic search for specific pathogens is warranted in these individuals.