**Question:** The first to appear in a cause of acute intestinal obstruction is -

A. Inflammation
B. Tension
C. Peritonitis
D. Hypovolemic shock

**Correct Answer:** B. Tension

**Core Concept:** Acute intestinal obstruction is a life-threatening surgical emergency that occurs when there is a mechanical or functional obstruction in the gastrointestinal (GI) tract, preventing the normal passage of feces and/or fluids. The obstruction can be classified as complete (total) or partial (subtotal or intermittent). The onset of clinical manifestations depends on the cause and severity of the obstruction.

**Why the Correct Answer is Right:** In the scenario of complete or total intestinal obstruction, the primary manifestation is typically abdominal pain, which can be described as severe, crampy, and radiating to the back. This pain is due to the increased intraluminal pressure causing mechanical damage to the intestinal wall (ischemia) and subsequent inflammation.

**Why Each Wrong Option is Incorrect:**

A. Inflammation: Although inflammation is a common feature in intestinal obstruction, it is not the first clinical manifestation. Inflammation occurs after the initial increase in intraluminal pressure and ischemia.

B. Tension: While tension is a consequence of obstruction, it is not the first sign. Tension is a result of the increased intraluminal pressure causing damage to the intestinal wall and subsequent ischemia.

C. Peritonitis: Peritonitis is a late complication of severe intestinal obstruction, typically occurring after several days of unrelieved obstruction. It is not the first clinical manifestation.

D. Hypovolemic shock: Hypovolemic shock is a severe circulatory collapse resulting from inadequate blood volume and blood loss. It is not directly related to the initial clinical manifestation of intestinal obstruction.

**Clinical Pearl:** The first clinical sign in a patient with a complete intestinal obstruction is **abdominal pain** due to the increase in intraluminal pressure, leading to intestinal ischemia and damage. This prompts the body's defense mechanisms to act, including inflammation, tension, peritonitis, and hypovolemic shock, which occur sequentially.