Prevalence
Causes
Clinical
features
Investigations
Therapy
Prognosis
|  | | | Investigations |
Calculate
-
the fractional excretion of sodium
c
[Urine Na x Plasma creatinine]/[Plasma Na x Urine creatinine] x 100
-
the fractional excretion of chloride c
[Urine Cl x Plasma creatinine]/[Plasma CL x Urine creatinine] x 100
Why?
A low fractional excretion of sodium or chloride makes pre-renal failure more likely
| Patient |
Target Disorder and
Reference Standard |
Diagnostic Test |
LR+
(95% CI)
|
Post-test Probability |
LR-
(95% CI)
|
Post-test Probability |
acute renal failure
c
(pre-test probability: 31%)
|
pre-renal failure
(possible cause and response to pre-renal therapy)
|
fractional excretion of sodium 1% or less
|
10
(3.9 to
26)
|
82% |
0.16
(0.055 to
0.45)
|
7% |
|
|
|
fractional excretion of chloride 1% or less
|
22
(5.8 to
87)
|
91% |
0.050
(0.0073 to
0.34)
|
2% |
A high urine osmolality makes pre-renal failure more likely
| Patient |
Target Disorder and
Reference Standard |
Diagnostic Test |
LR+
(95% CI)
|
Post-test Probability |
LR-
(95% CI)
|
Post-test Probability |
acute renal failure
c
(pre-test probability: 24%)
|
pre-renal failure
(response to pre-renal therapy)
|
urine osmolality > 500 mOsm/kg
|
7.9
(1.6 to
38)
|
71% |
0.79
(0.62 to
1.0)
|
20% |
|
internal medicine