Differential Diagnosis for 18-Year-Old Male with Elevated Creatinine and AST
Single Most Likely Diagnosis
- Muscle injury or strenuous exercise: Elevated AST (aspartate aminotransferase) can be seen in muscle injury, and creatinine levels can also be affected by muscle mass and activity level. Given the patient's age and normal liver function tests (ALT and bilirubin), this is a plausible explanation.
Other Likely Diagnoses
- Dehydration: Dehydration can cause a rise in creatinine levels due to decreased renal blood flow. Although the patient's GFR is slightly decreased, dehydration could be a contributing factor.
- Rhabdomyolysis: Although less likely without significant muscle symptoms, rhabdomyolysis can cause elevated AST and creatinine levels.
- Nephrolithiasis (kidney stones): Kidney stones can cause a mild decrease in GFR and elevated creatinine levels, especially if there is an obstruction.
Do Not Miss Diagnoses
- Acute kidney injury (e.g., due to medication or toxin): It is crucial to rule out any potential causes of acute kidney injury, as prompt treatment can prevent long-term damage.
- Hemolysis: Although the CBC is normal, it is essential to consider hemolysis as a cause of elevated AST and creatinine levels, as it can have severe consequences if left untreated.
Rare Diagnoses
- Polycystic kidney disease (PKD): Although rare in young adults, PKD can cause elevated creatinine levels and decreased GFR.
- Wilson's disease: This genetic disorder can cause liver and kidney damage, leading to elevated AST and creatinine levels. However, it is relatively rare and typically presents with other symptoms.
- Mitochondrial myopathies: These rare genetic disorders can cause muscle weakness and elevated AST levels, potentially affecting kidney function.