**Core Concept**
Renovascular hypertension is a type of secondary hypertension caused by narrowing or blockage of the renal arteries, leading to reduced blood flow to the kidneys. This condition can be visualized on intravenous urography (IVU), a radiological imaging technique that uses contrast dye to visualize the urinary tract.

**Why the Correct Answer is Right**
On IVU, renovascular hypertension may be characterized by features such as delayed or non-opacification of the affected kidney, thinning of the renal parenchyma, and presence of collateral vessels. These changes occur due to the reduction in blood flow to the kidney, which leads to ischemia and subsequent changes in the renal architecture. The correct answer is associated with one of these characteristic features.

**Why Each Wrong Option is Incorrect**
* **Option A:** Delayed or non-opacification of the affected kidney is a feature of renovascular hypertension, making this option incorrect.
* **Option B:** Thinning of the renal parenchyma is also a common finding in renovascular hypertension, making this option incorrect.
* **Option D:** Presence of collateral vessels is a compensatory mechanism to bypass the narrowed or blocked renal artery, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that renovascular hypertension can be a challenging diagnosis, and IVU may not always be diagnostic. Other imaging modalities such as angiography or CT angiography are often used to confirm the diagnosis.

**Correct Answer: C.**