From the Guidelines
A BUN/creatinine ratio of 70 in a 3-year-old is significantly elevated and requires immediate medical attention. Normal BUN/creatinine ratios typically range from 10:1 to 20:1, so a ratio of 70 suggests severe dehydration or possible pre-renal acute kidney injury 1. This child should be evaluated promptly in an emergency department for IV fluid rehydration, typically with isotonic fluids like normal saline at a rate determined by the degree of dehydration (often 20 mL/kg bolus initially). The elevated ratio occurs because dehydration causes increased reabsorption of urea (measured as BUN) in the kidneys while creatinine clearance remains relatively stable initially.
Common causes in children include gastroenteritis with vomiting and diarrhea, inadequate fluid intake, or excessive fluid losses from fever or heat exposure. According to the pRIFLE definition of AKI in children, which is referred to in the KDIGO guidelines 1, a change in eGFR or an increase in creatinine can be used to stage AKI. However, in this case, the focus should be on addressing the possible dehydration and pre-renal acute kidney injury. Parents should monitor for decreased urination, dry mouth, absence of tears when crying, and lethargy.
Laboratory tests including electrolytes, complete blood count, and urinalysis will likely be needed to assess the full extent of the condition and guide ongoing management. It is essential to note that AKI can be reversible or can lead to CKD, and prompt intervention is critical to prevent long-term kidney damage 1. The child's condition should be closely monitored, and further testing, such as renal biopsy, may be indicated if the condition does not improve with treatment.
Key considerations in the management of this child include:
- Prompt evaluation and treatment in an emergency department
- IV fluid rehydration with isotonic fluids
- Monitoring for signs of dehydration and AKI
- Laboratory tests to assess the extent of the condition
- Possible further testing, such as renal biopsy, if the condition does not improve with treatment.
From the Research
Significance of Elevated BUN/Creatinine Ratio
- An elevated BUN/creatinine ratio in a 3-year-old can indicate dehydration or prerenal azotemia 2, 3, 4.
- The studies provided do not directly address the significance of an elevated BUN/creatinine ratio in a 3-year-old, but they do discuss the effects of dehydration and rehydration on various biochemical measures, including creatinine levels 2, 3, 4.
- In the context of dehydration, an elevated BUN/creatinine ratio may suggest that the child is not producing enough urine or is experiencing a decrease in renal function 3.
- However, it is essential to note that the studies provided do not offer conclusive evidence on the significance of an elevated BUN/creatinine ratio in a 3-year-old, and further research would be necessary to determine its clinical implications 2, 3, 4.
Rehydration and Biochemical Measures
- The studies suggest that rehydration with balanced solutions, such as Ringer's lactate, may result in a slight reduction in hospital stay and improved biochemical outcomes, including a higher increase in blood pH and bicarbonate levels 2.
- However, the evidence is uncertain regarding the effect of balanced solutions on mortality during hospitalization in severely dehydrated children 2.
- Rehydration with 0.9% saline solution + 2.5% glucose may improve clinical scores and be used as an alternative and safe way for intravenous rehydration in children with mild-to-moderate dehydration 3.
- The choice of rehydration fluid, either Normal Saline (NS) or Ringer Lactate (RL), may not significantly affect the change in serum sodium levels during correction of severe dehydration in children with acute diarrhea 4.