A 40 year-old patient is admitted to your ward with a creatinine of 300. You notice that her creatinine one month ago was 95. She states that she has been “very sick” for the past week at home, and decided it was time to come to the hospital.
What steps would you take to further investigate the cause of this person’s acute kidney injury?
The differential diagnosis for an acute kidney injury (AKI) is extensive. A good history, physical exam, and ancillary lab tests can help make the correct diagnosis. An approach to this patient includes:
- History and associated symptoms
- Review medications
- Physical exam – vitals, postural BP and HR, volume status, including JVP
- Urinalysis – dipstick and microscopy (looking for casts if renal etiology)
- CBC, lytes, BUN
- Serial Cr
- Depending on results from microscopy, further investigations:
- CK (r/o myoglobin induced nephropathy)
- Serum protein electrophoresis/urine protein electrophoresis (r/o multiple myeloma)
- Peripheral blood film (look for cell fragments and r/o microangiopathy)
- Coagulation study and fibrinogen (r/o disseminated intravascular coagulopathy)
- Markers of inflammatory disease (i.e. ANA, ANCA, Anti-dsDNA)
- C3/C4/Ch50, anti-GBM antibody
- HepB, HIV serology (r/o secondary causes of AKI)
- Renal ultrasound (if suspect post-renal obstructive cause)
- Consider renal biopsy
- Call nephrology if no improvement within 24 hours
The differential diagnosis of AKI is:
- Pre-renal
- Hypovolemia – excessive diarrhea/vomiting without sufficient fluid intake
- Hemorrhaging – GI bleed
- Drug-induced –NSAIDs, ACEi
- Shock
- Nephrotic syndrome
- Cardiac failure
- Hepatic cirrhosis
- Renal
- Glomerular
- Inflammatory – post-infectious glomerular nephritis, cryoglobulinemia, Henoch-Schonlein purpura, Lupus nephritis, anti-glomerular basement membrane disease
- Thrombotic – DIC, thrombotic microangiopathy
- Interstitial
- Drug induced – NSAIDs, antibiotics
- Infiltrative – lymphoma
- Granulomatous – l sarcoidosis, tuberculosis
- Post-infective nephritis
- Pyelonephritis
- Tubular
- Ischemia – Acute tubular necrosis
- Toxins – drugs (i.e. aminoglycosides), myoglobin toxicity (i.e. from rhabdomyalisis)
- Hypercalcemia
- Immunoglobulin light chains (i.e. from multiple myeloma)
- Crystals – urate, oxalate
- Vascular
- Vasculitis
- Cryoglobulinemia
- Thrombotic microangiopathy
- Cholesterol emboli
- Renal artery or vein thrombosis
- Post-renal (obstructive)
- Kidney stone
- Pelvic malignancy
- Glomerular
Resources
- Hilton R. Acute renal failure. BMJ. 2006, 333:786-790.
- Lameire N, Van Biessen W, Vanholder R. Acute renal failure. Lancet. 2005, 365:417-430.
- Singri N, Ahya SN and Levin ML. Acute renal failure. JAMA. 2003, 289:747-751.
