<prompt> A 56-year-old woman has not passed stools for the last 14 days. Xray shows no air fluid levels. Probable diagnosis is -Paralytic ileusAganglionosis of the colonIntestinal pseudo-obstructionDuodenal obstruction  <response>: The information provided in the question is too less, but we have to come to a diagnosis based on the provided information. Lets see each option one by one.Paralytic ileusmultiple air fluid levels are noted, hence ruled out.Aganglionosis of the colon or Hirshprungs ds.presents in infancy or childhood hence ruled outDuodenal obstructionmultiple air-fluid levels are not noted, but the dominant symptom is recurrent, vomiting, which is not mentioned, hence ruled out.Intestinal pseudo-obstructionits the most likely diagnosis, as air-fluid levels are not seen in it.Harrison writes - The symptom of chronic pseudo-obstruction are chronic or intermittent constipation, crampy abdominal pain, anorexia and bloating. Abdominal x-rays reveal gaseous distention of the large and small bowel and occasionally of the stomach. Air-fluid levels are unusual and should raise the possibility of mechanical obstruction.Acute pseudoobstruction involves only the colon and presents with features of colonic obstruction as described before. Air-fluid level is also not a feature of colonic obstruction.About the fluid levels remember the following pointsup to 3 to 5 fluid levels less than 2.5 cm in length may be normal.multiple air-fluid levels are a feature of mechanical small intestinal obstruction and paralytic liens. They are not seen in colonic obstruction and pseudo-obstruction.They may be seen in colonic obstruction if the ileocecal valve is incompetent. 