Okay, let's tackle this question about ureteric colic caused by a stone. The user wants a detailed explanation for an MCQ, so I need to make sure I cover all the sections they specified.

First, the core concept. Ureteric colic is due to a stone in the ureter, which causes obstruction and spasm. The key here is understanding the pathophysiology. The stone blocks urine flow, leading to increased pressure upstream, and the ureter's attempt to push the stone down causes colicky pain.

Next, the correct answer. The question is about the mechanism. The primary cause is the stone itself, so the answer should be that the stone causes mechanical obstruction and spasm. I need to explain how the stone leads to these effects, maybe mentioning the ureter's peristalsis and the resulting pain.

Now, the wrong options. I need to think of common distractors. Maybe options could include other causes of colic, like biliary colic or renal colic from other sources. Or perhaps options about infection or other urological issues. I should explain why each is incorrect, such as biliary colic being due to gallstones in the bile ducts, not the ureter.

Clinical pearl: Remember that ureteric colic is typically sharp, comes and goes, and radiates to the groin. Also, associated symptoms like hematuria and nausea are important. A mnemonic might help here, like "URETER" for the symptoms.

I need to check the character count and make sure each section is concise. Use bold for key terms. Avoid markdown except for the specified sections. Keep the language clear for postgraduate students. Make sure the correct answer is clearly stated at the end.

**Core Concept**
Ureteric colic results from **mechanical obstruction** of the ureter by a stone, triggering **spasm of the ureteral smooth muscle** and **distal urinary stasis**. This obstruction leads to **increased intraluminal pressure**, activating sensory nerves and causing severe, episodic pain.

**Why the Correct Answer is Right**
The correct answer is **mechanical obstruction of the ureter by a stone**. Stones in the ureter (typically 2–5 mm in size) cause **active peristalsis** as the ureter attempts to propel the stone distally, resulting in **colicky pain**. This obstruction also leads to **hydronephrosis** and **reflux of urine**, triggering **inflammation** and **neurogenic pain** via the **sympathetic nervous system**.

**Why Each Wrong Option is Incorrect**
**Option A:** *Biliary colic due to gallstones* is caused by **choledochoduodenal compression**, not ureteric obstruction.
**Option B:** *Renal colic* is a consequence of **stone formation in the kidney**, not the ureter, and lacks the **spastic component** of ureteric colic.
**Option C:** *Ureteric stricture* causes **chronic obstruction**, not the **acute, intermittent pain** characteristic of colic.

**Clinical Pearl / High-Yield Fact**
Remember the **classic triad** of ureteric colic: **severe flank pain radiating to the groin**, **hematur

✓ Correct Answer: B. Increased peristalsis of ureter to overcome the obstruction