When to worry about creatinine levels

When to worry about creatinine levels?

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When to worry about creatinine levels

Creatinine is the breakdown product of creatine phosphate in muscle. It is produced at a fairly constant rate from muscle and depends on muscle mass. Thus, males have more creatinine levels than females because of more muscle mass in males. Creatinine is the most widely used marker of GFR for kidney function assessment.

Creatinine is not bound to plasma proteins so freely filtered by glomerulus. It is not reabsorbed by the renal tubules and only a small amount is secreted by the tubules So with a constant muscle mass, changes in serum creatinine reflect changes in the renal function.

Serum creatinine concentration does not increase until more than 50% of renal function has been lost.

Normal Range of Creatinine Level

The normal range for creatinine levels can vary slightly depending on the laboratory and the specific reference range used. However, as a general guideline, the normal range for creatinine levels in adults is typically around 0.6 to 1.2 milligrams per deciliter (mg/dL) for males and 0.5 to 1.1 mg/dL for females. It's important to remember that these are just approximate values and can vary depending on factors such as age, muscle mass, and overall health.

Causes of increased Serum Creatinine level

The causes of increased serum creatinine levels are

  • Large muscle mass
  • Rhabdomyolysis
  • Renal failure
  • Drugs: Trimethoprim, cimetidine  
  • Acute kidney injury
  • Nephrotic syndrome
  • Pyelonephritis

 

Risk Factors of Increased Creatinine Level

Certain conditions can lead to increase the creatinine level which is not related to renal injury like

  • Muscle Injury
  • Burns
  • Dehydration
  • Hemorrhage, Surgery
  • Sepsis
  • Pregnancy

 

Acute Kidney Injury (AKI)

Acute Kidney Injury is the sudden loss of kidney function or acute kidney damage which is usually reversible. Acute Kidney Injury (AKI) is characterized by increased serum creatinine level, impaired urinary output, electrolyte imbalance, edema, etc. 

When to worry about creatinine levels?

Serum creatinine level is the most important specific indicator of kidney function assessment. Raised or fluctuation in the creatinine level indicates of sort of kidney function impaired through there could be other causes of raised creatinine level other than renal causes.

When the serum creatinine level is less than 1.5 times from the baseline within the past 48 hours, one should be worried about Acute Kidney Injury (AKI). If there is an increase in serum creatinine level of more than 0.3 mg/dL over the past 48 hours or more than 1.5 times above the baseline line, one should be worried about Acute Kidney Injury (AKI).

One should worry about the increased creatinine level when it is associated with:
  • Impaired urinary output i.e. Oliguria (Less than 0.5 mL/kg per hour for >6 hours)
  • Evidence of fluid retention (Eg. Edema )
  • Electrolytes imbalance like hyperkalemia, Hyperphosphatemia
  • Metabolic acidosis

 

Common Causes of Acute Kidney Injury 

Acute Kidney injury (AKI) is one of the leading causes of increased serum creatinine levels. The decrease in the renal blood flow is one of the major factors for AKI like dehydration, blood loss, sepsis, burn, etc.

Prerenal causes of AKI

  • Dehydration
  • Blood Loss
  • Sepsis
  • Burn

Renal causes of AKI (Damage to Kidney tissue)

  • Glomerulonephritis
  • Acute tubular necrosis
  • Vasculitis
  • Acute intestinal nephritis

Post-renal causes of AKI

  • Urine outflow obstruction like stones & tumors in the urinary tract

 

AKIN Criteria for Acute Kidney Injury (AKI)

According to the AKIN (Acute Kidney Injury Network) criteria, at least 1 or more than 1 of the following criteria must be fulfilled within the last 48 hours for considering the Acute Kidney injury (AKI). AKI diagnostic criteria are:

  • Absolute increased in serum creatinine level ?0.3 mg/dL (?26.4 ?mol/L)
  • Serum creatinine level ?1.5 times above the baseline
  • Urine output less than 0.5 mL/kg per hour for more than 6 hours

 

Staging of AKI according to AKIN criteria 

To access the severity of AKI, staging of AKI is done under AKIN criteria.

Stage Creatinine level Urine Output
Stage 1 Absolute increase of creatine level ?0.3 mg/dL or
?1.5-2 times creatinine level from baseline		 Less than 0.5 mL/kg per hour for >6 hours
Stage 2 Creatinine level > 2-3 times above the baseline Less than 0.5 mL/kg per hour for >12 hours
Stage 3 Creatinine level > 3 times above the baseline, or
Increased creatinine level ? 4.0 mg/dL, or
On renal replacement therapy (eg. dialysis)		 Less than 0.3 mL/kg per hour for ?24 hours, or
Anuria for 12 hours

 

Importance of creatinine level

Creatinine levels are an important indicator of kidney function. Typically, creatinine levels are measured through a blood test, and elevated levels can suggest potential kidney problems. The specific threshold at which creatinine levels are considered worrisome may vary depending on factors such as age, gender, muscle mass, and the laboratory reference range used.
However, as a general guideline, here are some situations where higher creatinine levels may be a cause for concern:

1. Chronic Kidney Disease (CKD): If a person has known kidney disease, any increase in creatinine levels should be monitored closely. The stage of CKD is often determined by the estimated glomerular filtration rate (eGFR) calculated using creatinine levels.

2. Acute Kidney Injury (AKI): In cases of sudden kidney injury, a significant rise in creatinine levels over a short period of time can indicate acute kidney damage. AKI can occur due to various reasons such as dehydration, medication side effects, infections, or reduced blood flow to the kidneys.
criteria for acute kidney injury:
- rise of serum creatinine from baseline to at least more or equal to 0.3 mg/dl within 48hrs OR,
- serum creatinine at least 50% higher (1.5 times) than baseline within  week OR,
- reduction in urine output to less than 0.5 ml/kg/hr for longer than 6 hrs.

3. Medications and toxins: Certain medications and toxins can cause kidney damage, leading to elevated creatinine levels. It is important to monitor creatinine levels when using medications that are known to have nephrotoxic (kidney-damaging) effects, such as certain antibiotics or non-steroidal anti-inflammatory drugs (NSAIDs).

4. Dehydration: Dehydration can result in temporarily higher creatinine levels. It is crucial to ensure adequate hydration before interpreting elevated creatinine levels, as dehydration can cause a false impression of kidney dysfunction.

5. Other medical conditions: High creatinine levels can also be associated with conditions such as urinary tract obstruction, rhabdomyolysis (muscle breakdown), and certain autoimmune diseases. Monitoring creatinine levels helps evaluate kidney involvement in these conditions.

It is important to note that creatinine levels should be evaluated alongside other clinical information and medical history. 

It's also worth noting that creatinine levels alone do not provide a complete picture of kidney function. The estimated glomerular filtration rate (eGFR), which takes into account creatinine levels, age, gender, and other factors, is a more comprehensive measure of kidney function. Your healthcare provider can evaluate your creatinine levels and other factors to assess your kidney health accurately.