How can you tell if you are experiencing intestinal blockage or just constipation?

Vomiting. Even severe constipation usually does not cause a person to vomit and be unable to hold down food and/or liquid. Green emesis is a sign of obstruction that is also not typical for constipation. The most immediate threats to people with a true blockage are dehydration, electrolyte imbalances, and death of bowel tissues. Blockages need to be evaluated and treated by a surgeon.