Pocket Pediatrics: The Massachusetts General Hospital for Children Handbook of Pediatrics (Pocket Notebook Series), 2 Ed.

ACUTE DIARRHEA

Definition (Pediatr Rev 1989;11:6)

• > nml stool output (>10 cc/kg/d) or Δ in character, usually ↑ # BMs/d; WHO crit >3 stools/d

• Young infants have intestinal mucosa permeable to water; have greater net fluid loss

• 80% fluid absorption at small bowel; processes affecting SB have rapid dehydration

• Generally duration <14 d; longer than 14 d considered persistent/chronic diarrhea

Pathophysiology (Arch Dis Child 1997;77:201)

• 4 basic processes: Secretory, cytotoxic, osmotic, and inflammatory

• Secretory: 2/2 infectious enterotoxin (cholera, ETEC), metabolic/endocrine (hyperthyroid, VIPoma, ZES), or exogenous toxic agent (colchicines)

• Enterotoxin → ↑ secretion fluids/lytes via mucosal crypt cells or blocks villi absorp

• Cytotoxic: 2/2 destruction of mucosal cells of small intestine, generally 2/2 viral infection (rota, Norwalk), similar changes in celiac disease, can result in 2° osmotic diarrhea

• Osmotic: Seen in malabsorptive conditions, unabsorbed substance in lumen reaches osmotically active concentration causing water influx (i.e., lactose intolerance)

• Determined by fecal osmotic gap (FOG) = serum osm − 2(stool Na + stool K)

• FOG >100–120 is osmotic diarrhea; use serum osm to avoid error 2/2 transit time. If serum osm unavailable, can use stool osm but less accurate

• Inflammatory: 2/2 damage to intestinal lining w/ bloody stools, fecal leukocytes, and tenesmus, generally involves large intestine and terminal ileum

• Invasive organisms: Yersinia, Campylobacter, Salmonella, Shigella, EHEC

Etiology

History

• Hx recent consumption raw milk, salad, undercooked meat/poultry, unpurified H2O, recent Abx, immunocompromised, sick contacts, FHx GI dz (IBD), blood in stool

Clinical Manifestation

• In absence of bloody stools, hydration is 1° determinant of severity

• Check glucose (r/o DKA), and U/A (r/o UTI)

• With bloody diarrhea, need to rule out life-threatening conditions, surgical disease

• Intussusception: 6–12 mo (up to 2 yr), intermittent severe abd pain, “currant jelly stool” (late finding, vascular congestion/ischemia), palpable “sausage” on exam

• Cdiff colitis: Hx of recent antibiotic use, labs w/ inc WBC, fever, abd distention

Diagnostic Evaluation

• Fecal leukocytes: W/ methylene blue >1 WBC/HPF; 52% sens, 88% spec for +stool cx (outpts only), for C. diff 14% sens, 90% spec (J Clin Microbiol 2001;39:266)

• Cdiff toxin: ELIZA; 73.3% sens, 97.6% spec, PCR 93.3% sens, 97.4% spec (Clin Infect Dis 2007;45:1152). Pts <1 yr generally w/ asymp carriage

• O&P: Single test sens 72%, but 93% NPV if prevalence of infxn <20% in pop; gold std 3 samples (Clin Infect Dis 2006;42:972)

• Stool culture: Gold standard but important to assess which agents involved

• Fecal Osm Gap = Stool Osm − 2([stool Na] − [stool K]), >100–120 osmotic diarrhea; <100 secretory diarrhea

• Stool-reducing substances: Benedict test w/ hydrolysis assesses for reducing sugars (malabsorption) in stool; 72% sens, 73% spec (Arch Dis Child 1997;77:201)

• Fecal elastase-1: Test to differentiate pancreatic from nonpancreatic steatorrhea; only 68% sens and 59% spec for pancreatic insufficiency (Neth J Med 2004;62:286)

• Rotavirus ELISA: 70–98% sens, 71–100% spec (Pediatr Rev 2007;28:183)

Treatment (Pediatrics 1996;97:424; Pediatr Drugs 2003;5:151)

• Etiology dependent; generally supportive mgmt always a component

• ORT is as effective as IVF in >95% of cases for mild to moderate dehydration

• Early refeeding w/ milk or food after rehydration does not prolong diarrhea (CD007296); may reduce duration of diarrhea by ½ d though not proven

• Routine use of antidiarrheals is not supported and may have serious consequences

• Bacterial/presumed bacterial colitis; abx if severe dz or if pt immunocompromised, hx of chronic GI disease (Infect Dis Clin North Am 2005;19:585)

• Abx shorten course Shigella, no effect on Campylobacter, may prolong Salmonella

• Reported inc risk of HUS following abx for EHEC, not seen in meta-analysis

• Cdiff: Rx w/ metronidazole +/− PO Vanco × 10 d beyond other abx; 40% need re-Rx

Complications

• Hemolytic uremic syndrome: Microangiopathic hemolytic anemia, ↓ plts, fever, ARF, after bloody diarrhea 2/2 E. coli O157:H7; 5–10% ∼5–10 d after diarrhea

• Shigella assoc w/ CNS sx (incl szr, obtundation, death, Ekiri syndrome), reactive arthritis (HLA-B27+) and myocarditis

• Campylobacter associated with Guillain–Barré syndrome

• Postenteritis enteropathy: Loss of intestinal digestive and absorptive functions

• Can be of variable severity from lactose intolerance to total dysfunction

• Hx of recurrent diarrhea and FTT in infant

• ↑ risk if no breast-feeding, use of hypotonic rehydration or restriction of intake

• Rx w/ lactose-free, sucrose-free, full strength formula, support volume status w/ IVF, may need TPN/PPN as well; usually w/ complete recovery