Acute Kidney Injury vs Acute Tubular Necrosis
Acute Kidney Injury and Acute Tubular Necrosis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Acute Kidney Injury vs Acute Tubular Necrosis at a glance
- Acute Kidney Injury: Abrupt decline in renal function categorized as prerenal, intrarenal, or postrenal.
- Acute Tubular Necrosis: Most common cause of intrinsic AKI; tubular epithelial injury from ischemia or nephrotoxins.
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Side-by-side comparison
| Feature | Acute Kidney Injury | Acute Tubular Necrosis |
|---|---|---|
| At a glance | Abrupt decline in renal function categorized as prerenal, intrarenal, or postrenal. | Most common cause of intrinsic AKI; tubular epithelial injury from ischemia or nephrotoxins. |
| Classic presentation | Asterixis, pericardial friction rub, and uremic frost suggest advanced uremia requiring urgent dialysis evaluation.; Often asymptomatic; detected on routine labs; Reduced urine output or change in urine appearance; Volume overload symptoms: dyspnea, edema, orthopnea (if oliguric); Uremic symptoms in advanced injury: nausea, anorexia,… | Muddy brown granular casts in urine sediment are pathognomonic for ATN.; Often asymptomatic AKI discovered on labs in ICU or postoperative setting; Oliguria or anuria common; nonoliguric ATN in 30-50% (better prognosis); Symptoms of underlying cause: sepsis, shock, recent surgery, exposure to nephrotoxin; Uremic symptoms if severe:… |
| Workup / key labs | KDIGO AKI: Stage 1 (Cr 1.5-1.9× baseline or +0.3 mg/dL; UOP <0.5 mL/kg/h × 6-12 h). Stage 2 (Cr 2.0-2.9× baseline; UOP <0.5 mL/kg/h × ≥12 h). Stage 3 (Cr ≥3× baseline, ≥4 mg/dL, or RRT initiation; UOP <0.3 mL/kg/h × ≥24 h or anuria ≥12 h).; BMP with serum creatinine and BUN — establish baseline and trajectory; Urinalysis with microscopy… | Clinical diagnosis: AKI meeting KDIGO criteria with characteristic sediment (muddy brown casts), FENa >2%, recent ischemic or nephrotoxic event, and exclusion of prerenal/postrenal/other intrinsic causes. Biopsy rarely needed.; BMP — rise in creatinine and BUN, often with hyperkalemia, acidosis; Urinalysis with microscopy — muddy brown… |
| Imaging | Renal ultrasound — rules out obstruction (hydronephrosis) and assesses kidney size/echogenicity; Bladder scan — postvoid residual >150-200 mL suggests outlet obstruction; CT without contrast if stones suspected | Renal ultrasound to exclude obstruction; kidneys typically normal-sized and echotexture; CT only if specific cause suspected (atheroembolic disease, masses) |
| First-line treatment | Identify and treat underlying cause (volume, sepsis, obstruction, nephrotoxin withdrawal); Prerenal: isotonic crystalloid (lactated Ringer's or normal saline) — balanced solutions preferred; Postrenal: relieve obstruction with Foley catheter, percutaneous nephrostomy, or ureteral stent; Stop nephrotoxins: NSAIDs, ACEi/ARB (if… | Remove or treat underlying cause: stop offending nephrotoxin, treat sepsis, restore perfusion; Optimize hemodynamics: target MAP ≥65 with isotonic crystalloid and vasopressors (norepinephrine first-line) as needed; Adjust renally cleared medications (vancomycin, gabapentin, opioids, DOACs); Avoid further insults: NSAIDs, ACEi/ARB during… |
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