A 28-year-old woman is brought to the emergency department after a high-speed motor vehicle collision. She is haemodynamically stable (BP 126/80 mmHg, HR 88/min) with right-sided flank tenderness and microscopic haematuria. Abdominal examination reveals mild right costovertebral angle tenderness. What is the most appropriate investigation to confirm renal injury and determine its grade?

Explanation

## Investigation of Choice for Renal Injury Grading **Key Point:** Contrast-enhanced CT (CECT) abdomen and pelvis with arterial and delayed phases is the gold standard for diagnosis and grading of renal injuries. It detects parenchymal lacerations, vascular injuries, collecting system disruption, and retroperitoneal haematoma. ### Why CECT is Optimal for Renal Trauma 1. **Arterial phase** — detects active bleeding, pseudoaneurysms, and vascular injuries 2. **Delayed phase** — evaluates collecting system integrity, urine extravasation, and urinary obstruction 3. **Injury grading** — allows classification (Grade I–V per AAST) which guides management 4. **Associated injuries** — assesses contralateral kidney, other abdominal organs, and retroperitoneal structures 5. **Non-invasive** — preserves renal function and avoids contrast extravasation risk of retrograde studies ### Renal Injury Grading (AAST Scale) | Grade | Injury Description | Management | |---|---|---| | **I** | Contusion or small subcapsular haematoma (<10% surface) | Conservative | | **II** | Laceration <1 cm depth; haematoma 10–50% surface | Conservative | | **III** | Laceration >1 cm depth; >50% surface haematoma | Conservative or angioembolization | | **IV** | Laceration involving collecting system; renal artery thrombosis | Angioembolization or surgery | | **V** | Complete renal artery/vein injury; shattered kidney | Nephrectomy | **High-Yield:** Microscopic haematuria with blunt abdominal trauma warrants imaging. CECT is the only investigation that reliably grades injury and detects collecting system disruption. ### Comparison of Investigations | Investigation | Sensitivity | Specificity | Grading | Collecting System | Vascular Assessment | |---|---|---|---|---|---| | **CECT (arterial + delayed)** | 98–100% | 98–100% | Excellent (Grade I–V) | Excellent | Excellent | | **IVP** | 60–80% | Moderate | Poor | Moderate (delayed films) | None | | **Renal ultrasound** | 70–85% | Moderate | Poor | Limited | Doppler limited | | **Retrograde pyelography** | High | High | None | Good | None (invasive) | **Clinical Pearl:** IVP is rarely used in modern trauma because it lacks sensitivity for parenchymal injury, cannot grade severity, and requires delayed imaging. Retrograde pyelography is invasive and reserved for specific therapeutic indications (ureteral stent placement). **Mnemonic: CECT for Renal Trauma** — **C**ontrast-enhanced **C**T with **E**arly (arterial) and **T**imed (delayed) phases. ### Management Pathway ```mermaid flowchart TD A[Blunt flank trauma + haematuria]:::outcome --> B[CECT abdomen/pelvis<br/>arterial + delayed phases]:::action B --> C{Injury grade?}:::decision C -->|Grade I-III| D[Conservative management<br/>bed rest, analgesia<br/>serial imaging if Grade III]:::action C -->|Grade IV| E{Active bleeding?}:::decision E -->|Yes| F[Angioembolization]:::action E -->|No| G[Conservative with close monitoring]:::action C -->|Grade V| H[Nephrectomy]:::urgent D --> I[Follow-up imaging at 6-8 weeks]:::action ``` [cite:ATLS 10th Edition Ch 8]