CASE: This is a 18 year old female who presents to the emergency department with severe pain in her lower right quadrant abdomen for the past two weeks. She describes the pain as sharp and worse than being stabbed by a knife. Prior history of fever and chills. There is some suggestion of urgency, but no dysuria. She feels nauseated and but has not vomited. Her LMP was four weeks ago and she denies any possibility of pregnancy. Her past medical history is unremarkable. There is no family history of kidney stones. Examination: VS T36.7 (oral), P89, R 20, BP 90/60, oxygen saturation in room air 99%. She is alert and cooperative. She is uncomfortable, but she does not appear to be in severe pain. HEENT unremarkable. Neck supple. Heart regular without murmur. Lungs clear. No chest tenderness. Her abdomen is soft and non-tender on palpation. Bowel sounds are normoactive. There is no rebound tenderness. Her abdomen is tender over in the right upper quadrant. Her distal pulse are good. She is able to move all her extremities well and she speaks well. Blood studies are drawn and an IV is started. Her urine pregnancy test is negative and she is sent to radiology for an abdominal series. Radiology Investigations Results 1.Blood tests: CBC, metabolic profile all within normal limits 2.Plain X-Ray abdomen: mass of faeces in the RUQ, preliminary diagnosis constipation. Patient is given laxatives both oral and enema. Second x-ray reveals no obstruction. One week later patient still has RUQ pain, but x-ray is clear. 3.Abdominal Ultrasound: no clinical evidence, all organs healthy. Question: differencial diagnosises?