Acute intestinal obstruction is characterized by -a) Vomiting is common in duodenal obstructionb) Pain after each attack of vomiting is characteristic of ileal obstructionc) In colonic obstruction distension is common than vomitingd) X-ray erect posture is diagnostice) Colicky pain to steady pain indicates strangulation
Clinical features of small intestinal obstruction
Abdominal pain

Pain is crampy in nature and tends to be more severe the distal the obstruction.
the pain occurs in paroxysms and the patient is relatively comfortable in the intervals between the pain.
audible borborygmi are often noted by the patient simultaneously with the paroxysm of pain.
the pain may become less severe as, distention progresses, probably because motility is impaired in the edematous intestine.
when strangulation occurs, the pain becomes steady and more localized without a colicky component.

Vomiting

Vomiting is almost invariable, and it is earlier and more profuse the higher (proximal) the obstruction.
the vomits initially contains bile and mucus and remains as such if the obstruction is high (proximal) in the intestine.
the more distal the obstruction, the more likely it is that vomits will become feculent. 
Vomiting follows the onset of pain after an interval that varies directly with the level of obstruction.

Constipation and Obstipation

constipation and obstipation will eventually occur in complete obstruction, but some stools and gas may pass initially after the onset of symptoms. In some patients diarrhea may also be seen initially, due to increased peristalsis.

Abdominal distention

abdominal distention occurs as the obstruction progresses and the proximal intestine becomes increasingly dilated.
it is minimal to absent in proximal obstruction, but is pronounced in more distal obstruction.

Temperature

is normal or mildly elevated

Blood in the stool

is rare but does occur in cases of intussusception, or ischemic injury.

Plain radiograph of abdomen

will show dilated small bowel loops with air fluid levels in a ladder-like pattern. These feature are absent in proximal obstruction, early obstruction or closed-loop obstruction.
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