Adenocarcinoma/diagnostic imaging; Carcinoid Tumor/diagnostic imaging; Ileal Neoplasms/diagnostic imaging; Jejunal Neoplasms/diagnostic imaging; Lipoma/diagnostic imaging; Lymphoma, Non-Hodgkin/diagnostic imaging; Peutz-Jeghers Syndrome/diagnostic imaging; Tomography, X-Ray Computed/methods; Adenocarcinoma/pathology; Administration, Oral; Barium Sulfate/administration & dosage; Biopsy; Carcinoid Tumor/pathology; Chi-Square Distribution; Contrast Media/administration & dosage; Enema; Female; Humans; Ileal Neoplasms/pathology; Ileum/pathology; Image Processing, Computer-Assisted; Injections, Intravenous; Jejunal Neoplasms/pathology; Jejunum/pathology; Lipoma/pathology; Lymphoma, Non-Hodgkin/pathology; Male; Methylcellulose/administration & dosage; Peutz-Jeghers Syndrome/pathology; Polyethylene Glycols/administration & dosage; Radiographic Image Enhancement; Sensitivity and Specificity