This document discusses diagnostic techniques for gastrointestinal conditions. It mentions that Hirschsprung's disease involves dilation of the sigmoid colon and rectosigmoid junction. Diagnosis relies on identifying the transition from normal to dilated areas of the colon on imaging without colonic washouts or excessive barium. It also notes that arteriography can locate bleeding sites in the gastrointestinal tract but radionuclide studies using labeled red blood cells or colloid are often as accurate and simpler. Endoscopy can diagnose and treat conditions like Barrett's esophagus.