The hallmark symptom of sub-acute intestinal obstruction is intermittent abdominal pain due to partial and temporary blockage of the bowel lumen. This causes periods of bowel distension and contraction as the intestine attempts to overcome the obstruction, resulting in crampy, colicky pain that comes and goes. Unlike complete obstruction, vomiting and other symptoms are often less severe initially. Recognizing this symptom is crucial for timely diagnosis and management to prevent progression to complete obstruction and ischemia. Intermittent abdominal pain reflects the fluctuating nature of sub-acute obstruction and is key to identifying surgical urgency.

Reference: Bailey & Love’s Short Practice of Surgery, 27th Edition.