Which of the following occurs first in the order of effects due to an intestinal obstruction?

In the context of an intestinal obstruction, the site of the obstruction is the initial event in the sequence of physiological responses. The obstruction itself, whether it's due to a physical blockage (like a tumor or impacted feces) or functional issues (like paralysis of the intestinal muscles), creates a focal point in the digestive tract where normal peristalsis cannot occur. This interruption often leads to initial swelling and can set off a cascade of further effects, including increased pressure along the affected segment.

Following the identification of the obstruction site, the increased pressure on the intestinal wall usually happens as a direct consequence. This increased pressure can lead to various complications, including severe vomiting and prolonged ischemia, as the obstruction progresses and disturbs normal blood flow and function in the intestines.

Thus, recognizing the site of the obstruction is crucial because it is the starting point that dictates the subsequent physiological changes and symptoms associated with intestinal obstruction.