Laboratory assessment

In the past a number of laboratory tests were used to evaluate a child with diarrhea and/or vomiting. Because ORT has become the preferred method of treating diarrhea, routine laboratory testing is no longer necessary. Adequate therapy can be given for most children with acute diarrhea without laboratory testing. Most episodes of diarrhea are self-limiting.

Indications for laboratory testing are:

1. Child with severe dehydration or shock

2. Child receiving intravenous rehydration therapy

3. Suspicion of electrolyte imbalance like hypernatremia or hypokalemia

4. Child with dysentery

Stool examination is seldom required in children with acute watery diarrhea. Child with dysentery may show stool with a large number of leucocytes

indicating an inflammatory bacterial process. In the absence of gross blood or leucocytes, costly stool culture has very low yield and is rarely necessary. If the stool pH is less than 5.5 various other noninfectious causes like lactose intolerance should

be considered. Serum electrolytes, blood urea nitrogen and creatinine levels do not change the initial management approach in most patients. Serum electrolytes should be obtained in a child who shows signs of electrolyte imbalance. High urine specific gravity may indicate severe dehydration when combined with history of reduced urine output. In persistent diarrhea, stool microscopy, pH, reducing substances, culture may be needed.