MRCP is widely used to investigate pancreatico-biliary disorders and serves as a non-invasive alternative to endoscopic retrograde cholangiopancreatography. 1, 2 MRCP makes use of heavily T2-weighted sequences, thus exploiting the inherent differences in the T2-weighted contrast between stationary fluid-filled structures with a long T2-relaxation time and the adjacent soft tissue which with much shorter T2-relaxation time in the abdomen. 1, 2 A half-Fourier single- shot echo train spin sequence is utilized because of a higher signal-to noise ratio and contrast-to-noise ratio, and a lower sensitivity to motion and susceptibility to artefacts. 1, 2 Commonly, breath-hold 2D single-shot thick slab imaging and respiratory-triggered 3D imaging are utilized. 1, 2
The quality of MRCP is frequently degraded by superimposed high signal intensities of the fluids in the upper gastrointestinal tract. Therefore, negative oral contrast agents are administered prior to the examination to reduce the superimposed fluid signal. 1–3 The negative contrast effect is strong T2-shortening caused by high concentrations of manganese or iron in the agents. 1–3 Negative oral contrast agents cause the gastric lumen to appear dark, and can show gastric polypoid lesions as high signal on MRCP. 4
The majority of gastric polyps are fundic gland polyps (FGPs) and HPs (HPs), and are often incidentally found during endoscopies. FGPs are the most common polyps found in the stomach, which were observed in 0.8–23% of all endoscopies. 5–7 They are associated with familial adenomatous polyposis and proton pump inhibitor use. 7,8 They usually present as multiple small polypoid nodules in the gastric fundus and body. These lesions vary in size from 1 mm to 8 mm. 8,9 Endoscopically, they are typically sessile, shiny, translucent, and pale to pinkish in color, resembling the surrounding mucosa. 9,10 Histologically, they contain dilated oxyntic glands lined by flattened parietal and mucous cells. 8,9 In the management, polypectomy is recommended to confirm the diagnosis and to rule out dysplasia or adenocarcinoma in FGPs measuring > 1 cm in diameter and polyps that are ulcerated or located in the antrum. 8,9
HPs are the second most common type of gastric polyp after FGPs. 7–9 They are strongly associated with a chronic inflammatory trigger such as chronic gastritis from a Helicobacter pylori infection. 8–10 Most HPs are solitary, but occasionally there may be more than one. They most commonly occur in the antrum but can develop anywhere in the stomach. 8–10 Endoscopically, HPs are typically red in color, sessile or pedunculated, and less than 2 cm in diameter. 8–10 Histologically, they are characterized by dilated, elongated, and tortuous foveolae lined by hyperplastic gastric mucin-containing epithelial cells. 8–10 They are reported to be found in 0.6 to 2.1% of patients with gastric cancer. 11–14 And, HPs also denote an increased risk of neoplasia in the surrounding abnormal gastric mucosa and are associated with the occurrence of synchronous cancer elsewhere in the gastric mucosa. In the manegement, the size cutoff for resection is debatable as well, with some authors recommending a 2-cm minimum for polypectomy, while others recommend resection of all polyps greater than 0.5 cm.
In the present study, gastric polypoid lesions were identified on MRCP in 1.5% of cases. MRCP demonstrated gastric polypoid lesions with a high intensity with internal low intensity on MRCP. It was considered that the high intensity correlates with secretion in the dilated glands and foveolae, and the internal low intensity correlates with the stroma in the polyps.
The limitations of this study are: (i) it is a retrospective study; (ii) the cohort is large (1128 cases), but gastric polypoid lesions were detected in only 17 cases, of which 8 cases were not pathologically diagnosed. (iii) gastric adenomas which are precursors to gastric cancer and well differentiated tubular adenocarcinomas were not included in the present study. We consider that they can be shown as gastric polypoid lesions with a high intensity on MRCP due to internal tubular structure .