**Core Concept**
Atherosclerotic occlusive disease at the bifurcation of the aorta (Leriche syndrome) is a condition characterized by narrowing or blockage of the aortic bifurcation, leading to reduced blood flow to the lower extremities. This condition is often associated with atherosclerosis, which involves the buildup of plaque in the arterial walls.

**Why the Correct Answer is Right**
The classic symptoms of Leriche syndrome include intermittent claudication, impotence, and decreased or absent pulses in the lower extremities. These symptoms are due to the reduced blood flow to the lower extremities, which affects the muscles and other tissues. The symptoms are a result of the decreased oxygen and nutrient delivery to the affected areas.

**Why Each Wrong Option is Incorrect**
**Option A:** Intermittent claudication is a classic symptom of Leriche syndrome, making this option incorrect.
**Option B:** Impotence is also a common symptom of Leriche syndrome, making this option incorrect.
**Option C:** Decreased or absent pulses in the lower extremities are characteristic of Leriche syndrome, making this option incorrect.
**Option D:** Diarrhea is not a symptom of Leriche syndrome, making this the correct answer.

**Clinical Pearl / High-Yield Fact**
Leriche syndrome is often associated with atherosclerosis, which can also affect other areas of the body, such as the coronary arteries, leading to conditions like angina pectoris or myocardial infarction.

**Correct Answer:** D. Diarrhea