| Parameter 1 | Parameter 2 | Description | Comments |
|---|---|---|---|
| Common Reference Ranges | Adults | 8-20 mg/dL 2.9-7.1 mmol/L | |
| Pediatrics | 4-20 mg/dL | < 1 year old | |
| Critical value | A. > 40 mg/dL B. > 100 mg/dL C. > 20 mg/dL increase in 24 h | A. Unexpected; no dehydration B. Risk of uremia C. Consistent with new renal failure | |
| Natural substance? | Yes | Nitrogenous end-product of protein metabolism | |
| Inherent activity? | No | No normal physiologic activity | |
| Location | Production | Liver | From Ammonia and CO2 |
| Storage | Not stored | ||
| Secretion/excretion | Excreted unchanged via glomerular filtration | Some secretion and reabsorption | |
| Major causes of ... | High results | Renal dysfunction Dehydration and high-protein diet | Table 1 |
| Associated Signs & Symptoms | Signs & Symptoms of renal failure and uremic syndrome | Decreasing urine output, etc. | |
| Low results | Hepatic failure cachexia | Also overhydration | |
| Associated Signs & Symptoms | Signs & Symptoms of underlying disorder | Does not cause signs & symptoms directly | |
| After insult, time to ... | Initial elevation | 6 - 12 hrs | Depends on cause |
| Peak values | 6 hrs - 6 days | Assumes insult not removed | |
| Normalization | 6 hrs - 6 days | Assumes insult removed and no permanent damage | |
| Drugs often monitored with test | Aminoglycosides, Amphotericin B, gallium, lithium, diuretics | Table 3 | |
| Causes of spurious results | Falsely Elevated | Chloral hydrate | Assay dependent |
| Falsely Lowered | Chloramphenicol and streptomycin | Assay dependent Sodium fluoride in collection tube depresses results of urease assays |
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was last updated January 1, 1998.