What are the immediate assessment and management steps for a patient with suspected kidney failure?

Immediate Assessment and Management of Suspected Kidney Failure

For a patient with suspected kidney failure, immediately obtain serum creatinine with eGFR calculation, perform urinalysis with microscopy, assess volume status and vital signs, and obtain renal ultrasound to rule out obstruction—while simultaneously discontinuing all nephrotoxic medications and contrast agents. 1, 2, 3

Initial Clinical Assessment

Focused History

• Identify nephrotoxic exposures: NSAIDs, aminoglycosides, contrast media, ACE inhibitors/ARBs, proton pump inhibitors, and herbal supplements 2, 3
• Assess for systemic illness: Recent infections, sepsis, hypotension, cardiac surgery, or volume depletion episodes 2, 3
• Review chronic disease history: Diabetes, hypertension, heart failure, liver disease, and prior kidney disease 4, 2
• Determine symptom timeline: Abrupt versus gradual onset helps differentiate acute kidney injury (AKI) from chronic kidney disease (CKD) 2, 3

Physical Examination Priorities

• Hemodynamic assessment: Blood pressure (including orthostatic measurements), heart rate, jugular venous pressure, and peripheral perfusion 1, 2
• Volume status determination: Assess for signs of dehydration (dry mucous membranes, decreased skin turgor) versus volume overload (peripheral edema, pulmonary crackles, ascites) 1, 2, 3
• Abdominal examination: Palpate for bladder distension, masses, or costovertebral angle tenderness suggesting obstruction or infection 1
• Skin examination: Look for rashes suggesting systemic vasculitis or other autoimmune conditions 2

Essential Laboratory Evaluation

Immediate Blood Tests

• Serum creatinine with eGFR: Use the 2009 CKD-EPI equation as the primary marker for kidney function 1, 4
• Complete metabolic panel: Sodium, potassium, chloride, bicarbonate, calcium, phosphorus, magnesium, BUN, and glucose 1, 2, 3
• Complete blood count: Evaluate for anemia (suggesting chronicity) or infection 1, 2
• Calculate BUN/creatinine ratio: Ratio >20:1 suggests prerenal azotemia; <10:1 suggests intrinsic renal disease 2

Urine Studies

• Urinalysis with microscopy: Essential for detecting hematuria, pyuria, proteinuria, casts (red cell casts suggest glomerulonephritis; muddy brown casts suggest acute tubular necrosis), and crystals 1, 2, 3
• Fractional excretion of sodium (FENa): FENa <1% suggests prerenal cause; >2% suggests intrinsic renal disease (note: unreliable if patient recently received diuretics) 2, 3
• Urine albumin-to-creatinine ratio: Quantify proteinuria from untimed sample 1, 4

Additional Tests When Indicated

• Blood cultures: If fever or sepsis suspected 1
• C-reactive protein: If infection or inflammation suspected 1
• Uric acid and ionized calcium: For metabolic stone risk assessment if obstruction suspected 1

Imaging Studies

Primary Imaging

Renal ultrasound is the initial imaging modality for all patients with suspected kidney failure to rule out obstruction (hydronephrosis) and assess kidney size (small kidneys suggest chronicity). 1, 2, 3 This should be performed urgently but should not delay emergency interventions for life-threatening complications.

Advanced Imaging

• Contrast-enhanced CT with delayed urographic phase: Gold standard when ultrasound is inconclusive, obstruction is confirmed and requires localization, or when gross hematuria with trauma is present 1
• Avoid contrast in patients with eGFR <30 mL/min/1.73 m² unless absolutely necessary due to contrast-induced nephropathy risk 5

Categorizing the Etiology

Prerenal (Poor Perfusion)

• Clinical features: Volume depletion, hypotension, heart failure, cirrhosis, sepsis 2, 3
• Laboratory findings: BUN/creatinine ratio >20:1, FENa <1%, concentrated urine (specific gravity >1.020) 2

Intrinsic Renal (Kidney Parenchymal Damage)

• Acute tubular necrosis: History of ischemia, nephrotoxins; muddy brown casts on urinalysis 2, 3
• Acute interstitial nephritis: Recent medication exposure; white blood cell casts, eosinophiluria 2, 3
• Glomerulonephritis: Red blood cell casts, dysmorphic RBCs, proteinuria >20 RBCs per high-power field 5, 2

Postrenal (Obstruction)

• Clinical features: Older men with prostatic hypertrophy, history of nephrolithiasis, pelvic malignancy 1, 2
• Imaging: Hydronephrosis on ultrasound, bladder distension 1, 2

Differentiating Acute from Chronic Kidney Disease

A single abnormal test is insufficient—persistence of abnormalities for >3 months is required to diagnose CKD. 1, 4

Indicators of Chronicity

• Small kidneys on ultrasound (<9 cm in adults) 2, 3
• Anemia disproportionate to degree of kidney dysfunction 2, 3
• Hyperphosphatemia, hypocalcemia, elevated parathyroid hormone 4, 3
• Prior laboratory values showing elevated creatinine 1, 4

Acute-on-Chronic Presentation

Many patients have both AKI superimposed on CKD. Review past creatinine measurements to establish baseline kidney function. 1, 4

Immediate Management Principles

Fluid Management

• Prerenal azotemia: Fluid resuscitation with isotonic crystalloid (normal saline or lactated Ringer's) 2, 3
• Volume overload: Loop diuretics (furosemide) for pulmonary edema or severe peripheral edema 3
• Avoid hypotonic fluids and colloids in most situations 2

Medication Management

• Discontinue nephrotoxic agents immediately: NSAIDs, aminoglycosides, vancomycin (unless treating life-threatening infection), ACE inhibitors/ARBs (temporarily in AKI), contrast agents 5, 2, 3
• Adjust drug dosing for renal function: Many antibiotics, oral hypoglycemics, and other medications require dose reduction 5, 4
• Avoid oral phosphate-containing bowel preparations in patients with eGFR <60 mL/min/1.73 m² 5

Treat Life-Threatening Complications

• Hyperkalemia: Calcium gluconate for cardiac protection, insulin with dextrose, sodium polystyrene sulfonate, or dialysis if refractory 2, 3
• Severe metabolic acidosis: Sodium bicarbonate or dialysis 2, 3
• Volume overload refractory to diuretics: Urgent dialysis 2, 3
• Uremic symptoms: Pericarditis, encephalopathy, or bleeding require urgent dialysis 5, 3

Relieve Obstruction

If postrenal obstruction is identified, urgent urological consultation for bladder catheterization, nephrostomy tube placement, or surgical intervention is required. 1, 2

Nephrology Referral Criteria

Immediate Nephrology Consultation Required

• AKI without clear reversible cause 5, 3
• Stage 3 AKI or higher (creatinine ≥3× baseline or ≥4.0 mg/dL) 5, 3
• Abrupt sustained decrease in eGFR >20% after excluding reversible causes 5
• Urinary red cell casts or >20 RBCs per high-power field sustained and unexplained 5
• Need for renal replacement therapy 2, 3
• Refractory hyperkalemia, severe acidosis, or electrolyte abnormalities 5, 3

Urgent Referral (Within Days)

• eGFR <30 mL/min/1.73 m² (CKD stages G4-G5) 5
• Persistent proteinuria >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol) where kidney biopsy may be indicated 5
• Hypertension refractory to ≥4 antihypertensive agents 5
• Suspected glomerulonephritis or vasculitis 5
• Hereditary kidney disease or polycystic kidney disease 5

Timely Referral for RRT Planning

Refer patients with progressive CKD when the risk of kidney failure within 1 year is 10-20% or higher using validated risk prediction tools to avoid late referral (defined as <1 year before dialysis initiation). 5 Early referral is associated with reduced mortality, shorter hospitalizations, better dialysis access preparation, and increased uptake of peritoneal dialysis. 6, 7

Common Pitfalls to Avoid

• Delaying nephrology referral in elderly patients or those with multiple comorbidities: These patients benefit equally from specialist input 6, 7
• Assuming stable creatinine means no action needed: Review trend over time; even stable stage 4 CKD requires nephrology involvement 5
• Using contrast imaging without considering kidney function: Always check eGFR before contrast administration 5
• Continuing ACE inhibitors/ARBs during AKI: Temporarily discontinue until kidney function stabilizes 5, 2
• Failing to recognize acute-on-chronic kidney disease: Requires treatment of acute component while planning for chronic management 4, 3
• Inadequate assessment of volume status: Both volume depletion and overload worsen outcomes 2, 3