<Tr> <Td> Urea </Td> <Td> 2.5 - 10.7 mmol / L </Td> <Td> 20--40 mg / dL </Td> </Tr> <Tr> <Td> Creatinine </Td> <Td> 62 - 106 μmol / L </Td> <Td> 0.7 - 1.2 mg / dL </Td> </Tr> <Table> <Tr> <Th> BUN: Cr </Th> <Th> Urea: Cr </Th> <Th> Location </Th> <Th> Mechanism </Th> </Tr> <Tr> <Td>> 20: 1 </Td> <Td>> 100: 1 </Td> <Td> Prerenal (before the kidney) </Td> <Td> BUN reabsorption is increased . BUN is disproportionately elevated relative to creatinine in serum . Dehydration or hypoperfusion is suspected . </Td> </Tr> <Tr> <Td> 10 - 20: 1 </Td> <Td> 40 - 100: 1 </Td> <Td> Normal or Postrenal (after the kidney) </Td> <Td> Normal range . Can also be postrenal disease . BUN reabsorption is within normal limits . </Td> </Tr> <Tr> <Td> <10: 1 </Td> <Td> <40: 1 </Td> <Td> Intrarenal (within kidney) </Td> <Td> Renal damage causes reduced reabsorption of BUN, therefore lowering the BUN: Cr ratio . </Td> </Tr> </Table> <Tr> <Th> BUN: Cr </Th> <Th> Urea: Cr </Th> <Th> Location </Th> <Th> Mechanism </Th> </Tr>

How do you calculate bun to creatinine ratio