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

• Symptoms of intestinal obstruction: Pain, vomiting, distention and constipation • Pain is the first symptom encountered; it occurs suddenly and is usually severe. Pain in Intestinal Obstruction • It is colicky in nature and is usually centred on the umbilicus (small bowel) or lower abdomen (large bowel) • The pain coincides with increased peristaltic activity • With increasing distension, the colicky pain is replaced by a mild constant diffuse pain • The development of severe pain is indicative of the presence of strangulation • Pain may not be a significant feature in postoperative simple mechanical obstruction and does not usually occur in paralytic ileus