A 32-year-old man sustains a crush injury to his right leg in a motor vehicle accident. He develops acute kidney injury 6 hours after injury. Which is the most common cause of acute kidney injury in crush syndrome?

Question

Accepted Answer

A. Myoglobinuria leading to acute tubular necrosis. ## Acute Kidney Injury in Crush Syndrome

**Key Point:** Myoglobinuria is the most common cause of acute kidney injury (AKI) in crush syndrome, accounting for the majority of renal complications in this setting.

### Pathophysiology of Myoglobinuric AKI

1. **Muscle injury** → Release of myoglobin from damaged skeletal muscle
2. **Myoglobin filtration** → Overwhelms renal tubular reabsorption capacity
3. **Acidic urine** → Myoglobin precipitates in distal tubules and collecting ducts
4. **Tubular obstruction + direct toxicity** → Acute tubular necrosis (ATN)
5. **Renal failure** → Oliguria, elevated creatinine, hyperkalemia

### Clinical Features of Crush Syndrome AKI

| Feature | Mechanism |
| --- | --- |
| Dark cola-colored urine | Myoglobinuria |
| Elevated CK (often >5000 IU/L) | Muscle necrosis |
| Hyperkalemia | Release from damaged muscle |
| Hypocalcemia | Precipitation in muscle; later hypercalcemia in recovery |
| Acidosis | Lactic acid from ischemic tissue |

**High-Yield:** The urine dipstick is **positive for blood** but **no RBCs on microscopy** — this is pathognomonic for myoglobinuria and distinguishes it from hematuria.

### Prevention and Management

- **Aggressive IV hydration** (goal urine output 200–300 mL/hr)
- **Alkalinization of urine** (sodium bicarbonate) to prevent myoglobin precipitation
- **Monitor CK, potassium, and renal function** closely
- **Dialysis** if severe hyperkalemia or refractory AKI develops

**Clinical Pearl:** Rhabdomyolysis from crush injury is the classic teaching example of myoglobinuric AKI in orthopedic trauma — more common than sepsis or direct thermal injury as a cause of AKI in the acute phase.

[cite:Robbins 10e Ch 20]

Answer

B. Hypovolemic shock from hemorrhage alone

Answer

C. Sepsis from wound contamination

Answer

D. Direct thermal injury to the renal parenchyma

A 32-year-old man sustains a crush injury to his right leg in a motor vehicle accident. He develops acute kidney injury 6 hours after injury. Which is the most common cause of acute kidney injury in crush syndrome?

Explanation

Acute Kidney Injury in Crush Syndrome

Pathophysiology of Myoglobinuric AKI

Clinical Features of Crush Syndrome AKI

Prevention and Management

Practice similar questions

Join our NEET PG community

Feature	Mechanism
Dark cola-colored urine	Myoglobinuria
Elevated CK (often >5000 IU/L)	Muscle necrosis
Hyperkalemia	Release from damaged muscle
Hypocalcemia	Precipitation in muscle; later hypercalcemia in recovery
Acidosis	Lactic acid from ischemic tissue