Management of Patients Following Detection of Unsuspected Colon Lesions by PET Imaging  Michael Lin, Jenn Hian Koo, David Abi–Hanna  Clinical Gastroenterology and Hepatology  Volume 9, Issue 12, Pages 1025-1032 (December 2011) DOI: 10.1016/j.cgh.2011.06.028 Copyright © 2011 AGA Institute Terms and Conditions

Figure 1 (A) Maximum intensity projection image of a 43-year-old man with newly diagnosed follicular grade 1 lymphoma, with abdominal and right inguinal lymphadenopathy (stage II), who underwent FDG PET scan for staging. He was known to have type 2 diabetes on metformin therapy. The scan demonstrated abnormal focal, moderately increased FDG uptake at the known sites of lymphoma (arrows) as well as moderate to intense diffuse FDG uptake throughout the bowel (arrowheads), most markedly in the large intestines. There was also physiological urinary tracer pooling in the bladder and physiological FDG accumulation in the brain, myocardium, and liver. (B) A repeat PET scan was performed 4 days later after 72 hours of withholding metformin, with resolution of reactive bowel uptake and better visualization of known sites of lymphoma. Physiological tracer uptake in the collecting system of the kidneys and intense urinary tracer pooling in the bladder were also noted. Clinical Gastroenterology and Hepatology 2011 9, 1025-1032DOI: (10.1016/j.cgh.2011.06.028) Copyright © 2011 AGA Institute Terms and Conditions

Figure 2 (A) Maximum intensity projection image of staging FDG PET scan of a 61-year-old man with newly diagnosed non–small cell lung cancer. The known primary malignancy in the lower lobe of the right lung (arrow) demonstrated moderately increased FDG uptake. In addition, there was unexpected focal uptake in the ascending colon (arrowhead) and at the rectosigmoid junction (curved arrow). There was physiological urinary tracer excretion in the kidneys and bladder and prominent tracer pooling along the right ureter. (B) Transaxial CT and combined PET-CT images demonstrated focal intense FDG uptake in the ascending colon at the site of bowel wall thickening. Biopsy revealed a synchronous adenocarcinoma. (C) At colonoscopy, a circumferential, ulcerated, and obstructing adenocarcinoma was evident. The patient subsequently had a right hemicolectomy. (D) Transaxial CT and combined PET-CT also demonstrated focal uptake at the rectosigmoid junction, and at colonoscopy, a 15-mm pedunculated tubular adenoma with low-grade dysplasia was removed. Clinical Gastroenterology and Hepatology 2011 9, 1025-1032DOI: (10.1016/j.cgh.2011.06.028) Copyright © 2011 AGA Institute Terms and Conditions

Figure 3 (A) A 63-year-old woman with newly diagnosed poorly differentiated squamous cell lung cancer presented for a staging FDG PET-CT. Maximum intensity projection image demonstrated the known primary malignancy in lower lobe of left lung (arrow) with intense FDG uptake. In addition, there was unexpected mild to moderate focal uptake (maximum SUV, 5.4) at the rectosigmoid junction (curved arrow), best localized on the transaxial combined PET-CT image (B). (C) There was no anatomic abnormality observed on the concurrent low-dose CT component of PET-CT. She successfully underwent lobectomy for stage 1A lung cancer in August 2009. The colorectal lesion, however, was not further investigated until 14 months later when she presented with 20-kg weight loss, abdominal bloating, and pain. She subsequently underwent a colonoscopy and a laparoscopic anterior resection, which revealed a 35-mm moderately differentiated adenocarcinoma in the rectosigmoid at the site of FDG uptake on PET scan, with 1/6 lymph node metastatic involvement (pathologic stage T3N1;IIIB). Clinical Gastroenterology and Hepatology 2011 9, 1025-1032DOI: (10.1016/j.cgh.2011.06.028) Copyright © 2011 AGA Institute Terms and Conditions

Figure 4 (A) Transaxial CT and combined PET-CT scan demonstrated incidental focal increased FDG uptake at the rectosigmoid junction (circled in green) of an 80-year-old man with newly diagnosed Hodgkin's disease. Maximum SUV of the bowel lesion was 12.5. (B) At colonoscopy of the same patient, a 15-mm pedunculated rectal polyp was removed, and histology revealed a tubulovillous adenoma with low-grade dysplasia. (C) In another patient with melanoma, incidental focal uptake in the rectum was noted with similar level of metabolic activity (maximum SUV, 12.3), and a 40-mm synchronous rectal primary malignancy was found. Clinical Gastroenterology and Hepatology 2011 9, 1025-1032DOI: (10.1016/j.cgh.2011.06.028) Copyright © 2011 AGA Institute Terms and Conditions

Figure 5 Management schema for incidental colonic lesions detected on FDG PET. Clinical Gastroenterology and Hepatology 2011 9, 1025-1032DOI: (10.1016/j.cgh.2011.06.028) Copyright © 2011 AGA Institute Terms and Conditions