<prompt> In which one of the following conditions is gas under diaphragm not seenPerforated duodenal ulcerTyphoid perforationAfter laparotomySpontaneous rupture of oesophagus  <response>: After spontaneous rupture, the pressure in the oesophagus rapidly increases and burst at its weakest point in lower one-third, sending a stream of material into the mediastinum and often into the pleural cavity. Thus pneumomediastinum is formed Reference: Bailey and Love edition: 24 page no: 996 