<prompt> Best investigation to diagnose Meckels diverticulum?X-ray abdomenUltrasonographyBarium studyTc 99m Pertectinate scan  <response>: Ans. d Tc 99m Pertectinate scan Ref. LB 25thII59An aphorism attributed to Dr Charles Mavo is: a Meckels diverticulum is frequently suspected, often sought for and seldom foundMECKELS DIVERTICULUM present in 2 per cent of the population; it is situated on the antimesenteric border of the small intestine, commonly 60 cm from the ileocaecal valve, and is usually 3-5cm long. Many variations occur 2 per cent- 2 feet - 2 inches. In 20 per cent of cases the mucosa contains heterotopic epithelium, namely, gastric, colonic or sometimes pancreatic tissue. Meckels diverticulum can he very difficult to demonstrate by contrast radiology; small bowel enema would be the most accurate investigation. Technetium-99m scanning In cases of repeated gastrointestinal haemorrhage of unknown cause where a Meckels diverticulum is suspected the abdomen is imaged with gamma camera after the injection of 30-100 mic Ci 111-370 x 1010 Bq of 99Tc-labelled pertechnetate intravenously. This may localise heterotopic gastric mucosa revealing the site of a Meckels diverticulum in 90 per cent of cases. Exceptionally a Meckels diverticulum is found in an inguinal or a femoral hernia sac - Littres hernia.RadiopharmaceuticalCritical organDisease imaged1. Salivary glandTc-99m pertectinate2. PET-sestamibi fusion scanTc99m-sestamibiTc99m-201 thaliumsubtraction scanParathyroid3. 1-131, 1-125, 1-123Thyroid4. Tc99m-MDPBone5. Tc-99m pertechnetateMeckels diverticulum, gastric mucosa, intestine, thyroid, choroid plexus6. Tc-99m DTPAMAG3Renal GFR7. Tc-99m DMSARenal cortical function8. Xe-127, Xe-133, Kr-81mLung VP scan, trachea9. Tc-tagged RBCsSpleen, Gl bleeding10.Tc-99m HMPAOBrain scan11.Stress induced thalium-201Tc99m Stannous pyrophosphate Reversible myocardial ischemia12.TetrafosminAcute myocardial infarction heart13. HIDADISIDABiliary scintigraphy14.Tc-99m sulfur colloidLiver pathologies15.67Ga111lndium labeled WBCIntraabdominal abscess and inflammatory bowel disease16. DOPA-PET MIBGMRIExtraadrenal pheochromocytoma17.Selenium methioninePancreas18.SRS OctreoscanPancreatic neuroendocrine tumors 