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Answer 10

6 month-old female with chronic parenteral nutrition dependence secondary to microvillus inclusion disease presents for routine outpatient visit. History notable for increased stool output after exposure to older sibling with rotavirus. Physical exam is notable for decreased weight, lung sounds clear, no edema exam, no signs or symptoms of heart failure.
 
Labs:
Detail
Value
Normal
Flag
Sodium
130 mmol/L
 135-148 Low
Potassium
3.3 mmol/L
 3.20-4.50  
Chloride
95 mmol/L
 96-109 Low
Bicarbonate
15 mmol/L
 22-30 Low
Blood urea nitrogen
30 mg/dL
 7-18 High
Creatinine
0.9 mg/dL
 0.5-1.2  
Glucose
90 mg/dL
 66-199  
Calcium
12.5 mg/dL
 8.4-10.5 High
Magnesium
2 mg/dL
 1.6-2.6  
Phosphate
4.5 mg/dL
 2.7-4.9  
 
What is the most likely explanation for his labs:
 

A. Vitamin D deficiency

B. Dehydration

C. Vitamin A toxicity

D. Volume overload

E. Adrenal insufficiency

 

The correct answer is b. Dehydration.  Usually with dehydration from diarrhea, you will see normal or high plasma sodium, because the water is lost in excess of the sodium, which will tend to increase the plasma sodium concentration. However, patients with microvillus inclusion disease may have very high electrolyte losses in their stool, including sodium and potassium. In the setting of hypovolemia, serum calcium concentration rises – although total body calcium amount stays the same. Patients with volume overload will have unexplained increased weight and edema. Adrenal insufficiency presents with hypoglycemia, hyponatremia and hyperkalemia.