A rapidly rising creatinine with decreasing urine output signals acute kidney injury and must be reported.
Before you read
Test yourself first: 3 questions
Question 1 of 3
The nurse reviews the chart of a client with CKD. Which laboratory result is consistent with this diagnosis?
Answer: A. CKD is defined by a sustained reduction in kidney function, reflected by an elevated serum creatinine and a decreased glomerular filtration rate (GFR below 60 mL/min for 3 months or more). A normal creatinine with high GFR would indicate healthy kidneys. The hallmark labs are rising creatinine, rising BUN, and falling GFR.
Question 2 of 3
The nurse reviews a serum creatinine of 4.2 mg/dL and a BUN of 60 mg/dL. These results most strongly indicate which problem?
Answer: A. An elevated creatinine (normal 0.6-1.2) with an elevated BUN (normal 10-20) reflects impaired renal function. Creatinine is the most specific marker of glomerular filtration, so a marked rise signals acute or chronic kidney injury.
Question 3 of 3
The nurse is reviewing labs for a client in the oliguric phase of acute kidney injury. Which finding is expected?
Answer: A. In the oliguric phase of AKI, the kidneys cannot excrete waste or regulate electrolytes, so BUN and creatinine rise and potassium increases (hyperkalemia). Urine output falls below 400 mL/day. A low potassium and high urine output are typical of the diuretic (recovery) phase, not the oliguric phase.
Keep the streak going with more questions like these, each with a full rationale.
What is creatinine and bun?
Creatinine is the more reliable indicator because it is produced steadily by muscle and cleared by the kidneys, while BUN is influenced by hydration, diet, and bleeding. A rising creatinine signals declining renal function and the need to adjust nephrotoxic and renally cleared medications.
Key points to remember
- Creatinine is a more specific marker of kidney function than BUN.
- An elevated BUN with a normal creatinine often reflects dehydration rather than kidney disease.
- A BUN-to-creatinine ratio above about 20 to 1 suggests a prerenal cause such as dehydration.
- Rising creatinine often requires dose reduction or holding of renally cleared and nephrotoxic drugs.
- GFR estimated from creatinine stages chronic kidney disease severity.
- Many contrast studies and nephrotoxic antibiotics require checking renal function first.
Nursing priorities
- Monitor intake, output, and daily weights to evaluate fluid status and kidney perfusion.
- Review medications for nephrotoxic agents and renally cleared drugs needing adjustment.
- Ensure adequate hydration when a prerenal cause such as dehydration is suspected.
- Hold or question nephrotoxic drugs and contrast in patients with rising creatinine.
- Trend creatinine and GFR to detect worsening renal function early.
Labs & values
Patient teaching
- Stay well hydrated unless fluids are restricted, and tell providers about all medications and NSAID use.
- Attend follow-up labs to monitor kidney function, especially with diabetes or high blood pressure.
Red flags: report now
- A rapidly rising creatinine with decreasing urine output signals acute kidney injury and must be reported.
- Urine output under 30 mL per hour is a sign of inadequate kidney perfusion requiring escalation.
- Never give nephrotoxic drugs or contrast without checking renal function in an at-risk patient.
References
Clinical references for this topic
