## Core Concept
The question tests the understanding of the consequences of ureteral occlusion, which is a critical consideration in surgical procedures. Ureteral occlusion can lead to various complications, including obstructive nephropathy. The underlying principle here involves the pathophysiology of urinary tract obstruction.

## Why the Correct Answer is Right
The correct answer, **D. Hydronephrosis**, is right because occlusion of the ureter causes a blockage in the flow of urine from the kidney to the bladder. This blockage leads to the accumulation of urine in the renal pelvis and calyces, causing them to dilate, a condition known as **hydronephrosis**. This is a direct and immediate consequence of ureteral obstruction.

## Why Each Wrong Option is Incorrect
- **Option A: Complete renal atrophy** - While prolonged obstruction can lead to renal atrophy due to increased pressure and potential ischemia, it is not the immediate consequence.
- **Option B: Hematuria** - Hematuria (blood in the urine) can occur due to various reasons, including stones or trauma, but it is not a direct consequence of ureteral occlusion.
- **Option C: Renal failure** - Renal failure can occur if the obstruction is bilateral or if the obstruction in a single functioning kidney is not relieved. However, it is not as immediate or direct a consequence as hydronephrosis.
- **Option E: Hypertension** - Hypertension can be associated with renal disease, including obstructive nephropathy, but it is not an immediate consequence of acute ureteral occlusion.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **hydronephrosis** can be a silent condition and might not present with pain if the obstruction develops slowly. It's a critical diagnosis to consider in patients with a history of pelvic or abdominal surgery, given the risk of inadvertent ureteral injury.

## Correct Answer: D. Hydronephrosis