## Core Concept
Unilateral renal trauma refers to injury occurring to one kidney. This type of trauma can result from various causes such as direct blows to the flank, motor vehicle accidents, or falls. The consequences and management of unilateral renal trauma depend on the severity of the injury, which can range from minor contusions to severe lacerations or even vascular injuries.

## Why the Correct Answer is Right
In unilateral renal trauma, several physiological and pathological changes can occur to compensate for the injury. One key aspect is the body's attempt to maintain blood pressure and perfusion to vital organs.

## Why Each Wrong Option is Incorrect
- **Option A:** Hematuria is a common presentation of renal trauma, including unilateral, due to the injury to the renal parenchyma or the collecting system.
- **Option B:** A decrease in renal function on the affected side can occur due to the direct injury to the kidney, leading to impaired filtration and excretion.
- **Option C:** Contral and ipsilateral responses can occur; however, specific systemic responses like hypertension might not directly relate to unilateral trauma without considering the overall clinical context, including potential complications.
- **Option D:** The activation of the renin-angiotensin-aldosterone system (RAAS) leading to hypertension is more complex and generally not a direct consequence of unilateral renal trauma unless there's a specific scenario like renal artery stenosis post-trauma.

## Clinical Pearl / High-Yield Fact
A critical point to remember is that in cases of unilateral renal trauma, especially if the injury is severe, the priority is to assess for complications such as bleeding, urinary extravasation, and vascular injury. The management often involves monitoring, with surgical intervention reserved for severe cases or those with complications.

## Correct Answer: D.