Pediatric Gastroenteritis Workup

Updated: Nov 26, 2018
  • Author: Randy P Prescilla, MD; Chief Editor: Russell W Steele, MD  more...
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Laboratory Studies

The vast majority of children presenting with acute gastroenteritis do not require serum or urine tests, as they are unlikely to be helpful in determining the degree of dehydration. In a meta-analysis of 6 studies, only serum bicarbonate (greater or less than 17) had statistically significant positive and negative likelihood ratios for detecting moderate dehydration. [16]

Clinically significant electrolyte abnormalities are rare in children with moderate dehydration. Any child being treated with intravenous fluids for severe dehydration, however, should have baseline electrolytes, bicarbonate, and urea/creatinine values tested. Laboratory tests are also indicated in patients with moderate dehydration whose history and physical examination are inconsistent with straightforward gastroenteritis.

Fecal leukocytes and stool culture may be helpful in children presenting with dysentery. Children older than 12 months with a recent history of antibiotic use should have stool tested for C difficile toxins. Those with a history of prolonged watery diarrhea (>14 days) or travel to an endemic area should have stool sent for ova and parasite tests.

Any child with evidence of systemic infection should have a complete workup, including CBC count and blood cultures. If indicated, urine cultures, chest radiography, and/or lumbar puncture should be performed.


Imaging Studies

Abdominal films are not indicated in the management of acute gastroenteritis. If the clinician suspects a diagnosis other than acute gastroenteritis based on history and physical examination findings, appropriate imaging modalities should be pursued.


Other Tests

Workup of acute gastroenteritis should begin by using elements of the history and physical examination to determine the level of dehydration. Both the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend using a simple dehydration scale to classify the total body water loss occurring with dehydration as minimal/none (< 3%), mild/moderate (3-9%), or severe (>10%) (see Table 1). [2] The World Health Organization (WHO) recommends a simpler system for use by both physicians and lay health workers, which classifies dehydration as none, some, or severe (see Table 2).

A meta-analysis of 13 separate studies looking at individual signs and symptoms of dehydration found that only abnormal capillary refill (>2 seconds), decreased skin turgor, and abnormal respiratory pattern (hyperpnea) had statistically and clinically significant positive and negative likelihood ratios for detecting dehydration in children. [16]

Several studies have found that combinations of clinical signs and symptoms may have better sensitivity and specificity for detecting dehydration in children than individual signs or symptoms. [16, 17, 18, 19, 20]

A study by Gorelick et al assessed the validity of a combination of 10 signs and symptoms similar to those recommended by the CDC. They found that the presence of 3 or more signs had a sensitivity of 0.87 and a specificity of 0.82 for detecting moderate dehydration. [18] The presence of 7 or more signs had a sensitivity of 0.82 and a specificity of 0.90 for detecting severe dehydration.

Parkin et al recently validated a an 8-point scale that assigns 0-2 points each to general appearance, sunken eyes, mucous membranes, and tears. [17] A score of 5-8 on this scale had a positive likelihood ratio of 5.2 and a negative likelihood ratio of 0.55 for the presence of moderate/severe dehydration in children with acute gastroenteritis.

Table 1. Assessment of Dehydration [2] (Open Table in a new window)

Symptom or Sign

No or Minimal Dehydration

Mild-to-Moderate Dehydration

Severe Dehydration

Mental status


Restless, irritable

Lethargic, unconscious


Drinks normally

Drinks eagerly

Drinks poorly

Heart rate


Normal to increased


Quality of pulses


Normal to decreased

Weak or not palpable



Normal or fast




Slightly sunken

Deeply sunken





Mouth and tongue




Skin fold

Instant recoil

Recoil < 2 seconds

Recoil >2 seconds

Capillary refill



Prolonged or minimal




Cold, mottled, cyanotic

Urine output




Table 2: Assessment of Dehydration [21] (Open Table in a new window)

Severe Dehydration

Two of the following signs:

  • Lethargic or unconscious

  • Sunken eyes

  • Not able to drink or drinking poorly

  • Skin pinch goes back very slowly

Some Dehydration

Two of the following signs:

  • Restless, irritable

  • Sunken eyes

  • Thirsty, drinks eagerly

  • Skin pinch goes back slowly

No Dehydration

Not enough of the above signs to classify as some or severe dehydration