What is the best course of action for a patient with hyperglycemia, elevated Blood Urea Nitrogen (BUN) and creatinine levels, low estimated Glomerular Filtration Rate (eGFR), and hypocalcemia, indicating impaired renal function?

Management of Acute Kidney Injury with Hyperglycemia and Hypocalcemia

This patient requires immediate confirmation of chronicity through repeat testing within 1-2 weeks, urgent nephrology referral given the eGFR of 27 mL/min/1.73m², aggressive glycemic control, and evaluation for volume status to guide fluid management. 1

Immediate Diagnostic Priorities

Do not assume this is chronic kidney disease based on a single abnormal eGFR and creatinine measurement, as this could represent acute kidney injury (AKI) or acute kidney disease (AKD) rather than established CKD. 1 The critical first step is:

• Repeat creatinine and eGFR within 1-2 weeks to establish chronicity, which requires abnormalities persisting for at least 3 months 1
• Review any prior measurements of creatinine, eGFR, or urinalysis to determine if this represents acute deterioration versus chronic disease 1
• Obtain urine albumin-to-creatinine ratio (UACR) immediately, as both eGFR and albuminuria are required for complete CKD assessment 1
• Order imaging (renal ultrasound) to assess kidney size and cortical thickness, as reduced size suggests chronicity 1

Volume Status Assessment and Fluid Management

Determine volume status through specific physical examination including orthostatic vital signs, jugular venous pressure, peripheral edema, and mucous membrane moisture to differentiate hypovolemia requiring aggressive fluid resuscitation from euvolemia or hypervolemia. 2

• If hypovolemic: Administer isotonic saline at 15-20 mL/kg/hour to restore renal perfusion 2
• Monitor daily weights and strict intake/output to assess fluid balance trends 2
• Measure BUN and creatinine every 6-12 hours initially, then daily once stable 2

The BUN/creatinine ratio of 15.5 is within normal range (12-20), which argues against severe prerenal azotemia, though the elevated absolute values indicate significant renal impairment. 2

Urgent Nephrology Referral

Refer immediately to nephrology because the eGFR is 27 mL/min/1.73m², which is well below the threshold of 30 mL/min/1.73m² that mandates specialist evaluation. 1 This referral is classified as Grade A evidence and should occur regardless of whether this represents acute or chronic disease. 1

Additional indications for urgent referral include:

• Uncertainty about etiology of kidney disease (diabetic kidney disease versus other causes) 1
• Rapidly progressing kidney disease if repeat testing shows worsening 1
• Need for evaluation of potential complications of advanced CKD at this eGFR level 1

Hyperglycemia Management

Aggressively control the glucose of 180 mg/dL as hyperglycemia can independently elevate urinary albumin excretion and worsen kidney function. 1

• Target glucose control to reduce risk of diabetic kidney disease progression 1
• Marked hyperglycemia can falsely elevate UACR, so glucose control is essential before interpreting albuminuria results 1
• Adjust diabetes medications for reduced eGFR, as many require dose reduction or discontinuation at this level of kidney function 1

Hypocalcemia Management

The calcium of 8.4 mg/dL (just below 8.5 mg/dL lower limit) requires evaluation and management as hypocalcemia is expected with eGFR <60 mL/min/1.73m² due to impaired vitamin D activation and secondary hyperparathyroidism. 3

• Check intact parathyroid hormone (PTH), 25-hydroxyvitamin D, and phosphorus levels to evaluate for CKD-mineral bone disorder 3
• Metabolic abnormalities including hypocalcemia occur at higher eGFR levels than previously recognized, particularly in elderly patients 3
• Consider calcium and vitamin D supplementation based on PTH and vitamin D levels, guided by nephrology 3

Medication Review

Immediately review and stop all nephrotoxic medications, particularly NSAIDs which cause diuretic resistance and worsen renal function. 2

• Avoid NSAIDs unless absolutely essential 1, 2
• Review any ACE inhibitors or ARBs if prescribed - these should be continued if the patient has diabetes with albuminuria, but require close monitoring 1
• Monitor serum creatinine and potassium every 6-12 hours initially if on ACE inhibitors/ARBs 1, 2
• An increase in creatinine up to 50% above baseline or to 266 μmol/L (3 mg/dL) is acceptable with ACE inhibitor/ARB therapy 1
• Stop potassium supplements if on ACE inhibitors/ARBs to avoid hyperkalemia 2

Establishing Etiology

Determine the cause of kidney disease using clinical context, diabetes duration, presence of retinopathy, medication history, and family history. 1

• Diabetic kidney disease typically presents with long-standing diabetes, retinopathy, and albuminuria without hematuria 1
• However, diabetic kidney disease can be present at diagnosis in type 2 diabetes without retinopathy 1
• Consider kidney biopsy if atypical features present (rapid progression, absence of retinopathy in type 1 diabetes, active urinary sediment) 1

Monitoring Strategy

Serial monitoring is essential to determine trajectory and guide management:

• BUN, creatinine, and electrolytes every 6-12 hours initially, then daily once stable 2
• Repeat eGFR and UACR in 1-2 weeks to confirm chronicity 1
• If CKD is confirmed, monitoring frequency depends on stage: at eGFR 27 mL/min/1.73m² (stage 4), this requires at least quarterly monitoring 1

Critical Pitfalls to Avoid

• Do not delay nephrology referral - at eGFR 27 mL/min/1.73m², the patient needs at least 12 months of preparation for potential dialysis or transplantation 4
• Do not assume chronicity from single measurement - acute processes are reversible and require different management 1
• Do not stop ACE inhibitors/ARBs prematurely if diabetic kidney disease is present, as these provide mortality benefit despite temporary creatinine elevation 1
• Do not overlook volume status - prerenal azotemia from hypovolemia is reversible with appropriate fluid resuscitation 2