A 4-year-old boy was brought to the emergency department by his parents due to severe abdominal pain. The pain started suddenly when he was having his breakfast in the morning. The pain is not associated with nausea, vomiting, diarrhea, or painful micturition. The patient has not passed stool in the last four days. He appears restless. Temperature is 37.4 C (99.2 F), pulse 112/min, respirations are 22/min, blood pressure is 100/80 mm of Hg. On examination, the abdomen is slightly distended with hyperactive bowel sounds. X-ray is shown in the exhibit below. Other examination findings are unremarkable. Abdominal ultrasonography reveals no abnormalities.