Okay, let's tackle this question about the investigation of choice for blunt abdominal trauma with hematuria. First, I need to recall what the standard protocol is in such cases.

Blunt abdominal trauma can cause various injuries, and hematuria is a key sign. Hematuria typically points towards genitourinary system injury, especially the kidneys or bladder. The main concern here is to detect any significant injury that might require surgical intervention.

The classic approach for trauma patients with hematuria is to use imaging. The options might include CT scan, ultrasound, cystoscopy, or intravenous pyelogram. I remember that CT urogram is the gold standard now because it provides detailed images of the kidneys, ureters, and bladder, and can detect even minor injuries. It's also fast and widely available in trauma settings.

Wait, but maybe in some cases ultrasound is used first, like in the FAST exam. However, FAST is more for detecting free fluid (like blood) in the abdomen, not specifically for genitourinary injuries. So for hematuria, CT is better. Intravenous pyelogram is older and less commonly used now. Cystoscopy is invasive and not the first step unless there's a specific indication.

So the correct answer should be CT urogram. The other options are either less specific or outdated. Let me check the options again. The question didn't list them, but based on standard options, the correct one is CT urogram. The wrong options would include ultrasound, IV pyelogram, or maybe cystoscopy.

Clinical pearl: In trauma with hematuria, CT urogram is the investigation of choice. Don't rely on IV pyelogram or cystoscopy as first steps. Also, FAST is for peritoneal fluid, not GU details.

**Core Concept**
Blunt abdominal trauma with hematuria necessitates rapid identification of genitourinary (GU) injuries, particularly renal or bladder trauma. CT urogram is the gold standard due to its high sensitivity for detecting parenchymal, vascular, and collecting system injuries.

**Why the Correct Answer is Right**
CT urogram combines non-contrast CT for kidney stones, contrast-enhanced CT for parenchymal injuries, and excretory phase imaging for collecting system/ureteral trauma. It is superior to other modalities in detecting hematomas, lacerations, and urinary tract disruptions, guiding management decisions (conservative vs. surgical).

**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasound (e.g., FAST exam) detects peritoneal fluid but lacks sensitivity for subtle GU injuries.
**Option B:** Intravenous pyelogram (IVP) is obsolete in trauma; it fails to detect retroperitoneal injuries and has poor sensitivity for renal parenchymal damage.
**Option C:** Cystoscopy is invasive, not first-line, and risks iatrogenic injury in unstable patients.

**Clinical Pearl / High-Yield Fact**
In trauma patients with hematuria, **CT urogram** is the investigation of choice. Remember: FAST identifies free fluid but misses GU tract injuries; do not rely on IVP or cystoscopy for initial assessment.

**Correct Answer: D. CT urogram**

✓ Correct Answer: B. CECT