Normal urine output (minimum): 0.5 to 1 ml/kg/hr daily
Oliguria: < 500 ml urine/ 24 hours
Anuria: < 100 ml urine/ 24 hours.
| Low urine output: potential causes |
| Prerenal: |
heart failure, shock, volume depletion, third spacing fluids, renal artery compromise |
| Renal: |
acute tubular necrosis, end-stage renal disease, interstitial disease, glomerular disease, drug induced: (Aminoglycosides, amphotericin B, cisplatin, colistin, cyclosporin, dextran, gallium, hydroxyurea, lithium, methicillin, methotrexate, methoxyflurane, nitrofurantoin, pentamidime, plicamycin, streptozocin, and vancomycin.), bilateral cortical necrosis |
| Post-renal: |
neurogenic bladder, obstruction of ureter, bladder neck, or urethra. |
| Differential diagnosis |
| Lab |
pre-renal |
renal |
| Urine/serum creatinine |
>40 |
<20 |
fractional excreted sodium:
[UNa/serum Na] / [Ucr/ serum creatinine] x 100 |
<1 |
>1 |
| Urine osmolality |
>500 |
<350 |
| Urinary sodium |
<20 |
>40 |
| Normal values: |
| Appearance |
straw or yellow colored / clear |
| Specific gravity: |
infant: 1.002 - 1.006
child and adult: 1.001 - 1.035 |
| pH |
Child and adult: 4.6 - 8 |
| Following substances should be negative: |
acetone, bilirubin, blood, glucose, nitrite, protein, leukocyte esterase. |
| WBC |
0 - 4/HPF |
| RBC |
Male: 0 - 3/HPF female: 0 - 5/HPF |
| Epithelial |
Occasional |
| Hyaline casts |
Occasional |
| Bacteria |
None |
|
|
| Bilirubin |
| Positive |
hepatitis, obstructive jaundice |
| Blood |
| Positive |
tumors, infection, trauma, hemolytic anemia, coagulopathy, interstitial nephritis, polycystic kidneys, kidney stones, burns, cystitis, prostatitis, pyelonephritis |
| Epithelial cells |
| Positive |
acute tubular necrosis, necrotizing papillitis |
| Glucose |
| Positive |
diabetes, cushing's disease, burns, steroids, hyperthyroidism, pancreatitis, pancreatic carcinoma, shock |
| Ketones |
| Positive |
diarrhea, vomiting, DKA, starvation, high fat diet, hyperthyroidism, pregnancy, febrile states. |
Leukocyte esterase (detects 5 or > WBC).
Used along with test for nitrites to detect UTI (predictive capacity: approximately 74 %). If both nitrites and leukocyte esterase are negative, there is a 97% chance that a UTI is not present. |
| Positive |
Infection |
| Nitrite |
| Positive |
Infection present. Nitrates are converted to nitrites by many strains of bacteria. |
| Protein |
| Positive |
glomerulonephritis, pyelonephritis, nephrotic syndrome, pre-eclampsia, malignancies, heavy exercise, stress, CHF, malignant hypertension |
|
