From the Guidelines
Urinary creatinine is a crucial marker for assessing kidney function, and its measurement is essential for calculating the creatinine clearance rate, which estimates glomerular filtration rate (GFR) 1. When evaluating urinary creatinine, it's essential to consider factors such as muscle mass, age, sex, and diet, as these can affect creatinine levels.
- Normal urinary creatinine levels typically range from 800 to 2000 mg per day, though this varies based on individual characteristics.
- Low urinary creatinine may indicate poor kidney function, muscle wasting, or incomplete urine collection, while high levels can reflect increased muscle breakdown, high-protein diets, or certain medications.
- The measurement of creatinine clearance by using timed (for example, 24-hour) urine collections does not provide more accurate estimates of GFR than do prediction equations, as stated in the national kidney foundation practice guidelines for chronic kidney disease 1.
- The guidelines recommend obtaining 24-hour urine collections only for special clinical circumstances, and instead, suggest using prediction equations to estimate GFR 1.
- Urinary creatinine is also used to normalize other urinary measurements like protein or albumin to account for urine concentration differences.
- If abnormal results occur, follow-up testing may include blood creatinine measurement, additional kidney function tests, or repeated urine collection under supervision.
- The frequency of monitoring kidney function, including urinary creatinine, should be guided by the severity of chronic kidney disease (CKD) and the risk for progression, as outlined in the kidney disease: improving global outcomes 2012 clinical practice guideline 1.
From the Research
U Creatinine
- U creatinine, or urine creatinine, is a measure used to assess kidney function, often in conjunction with other tests such as the urinary albumin-to-creatinine ratio (UACR) 2.
- Serum creatinine is the most widely used functional biomarker of the kidney, but its use has substantial shortcomings, including limitations in accurately estimating static kidney function and detecting changes in kidney function 3.
- The urinary albumin-to-creatinine ratio (UACR) is used to define albuminuria, with a UACR ≥30mg/g Cr indicating albuminuria 2.
- Studies have investigated the effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) on kidney outcomes, including the reduction of serum creatinine levels and the risk of end-stage renal disease (ESRD) 2, 4, 5.
- ACE inhibitors and ARBs are recommended as first-line antihypertensive therapy in patients with hypertension and albuminuria, but their utilization in clinical practice has been found to be suboptimal, with a significant gap in preventive care delivery for adults with hypertension and albuminuria 6.