Gastric polypoid lesions detected on magnetic resonance cholangiopancreatography


 Background: On magnetic resonance cholangiopancreatography (MRCP) using a negative oral contrast agent, the gastric lumen appear dark, and gastric polypoid lesions can be seen. To our knowledge, there are no reports examining gastric polypoid lesions detected on MRCP.We exained the characteristics of gastric polypoid lesions detected on MRCP and discussed the management of the lesions.Material and Methods: MRCP images using a negative oral contrast agent were retrospectively evaluated in 1128 cases, and gastric polypoid lesions detected were investigated.Results: Gastric polypoid lesions were detected in 17 of the 1128 cases (1.5%) on MRCP. The mean patient age and gender were 66.7 years (range: 48-85 years) and 7 males / 10 females. A single lesion was detected in 4 cases, 2 to 4 lesions were detected in 6 cases, 5 to 10 lesions in 3 cases, and 11 or more in 4 cases. In 4 cases, the upper, middle, and lower portions of the stomach were occupied with polypoid lesions, in 4 cases, the upper and middle portions were occupied, in 1 case, the middle and lower portions were occupied, and in 8 cases, only the upper portion was occupied. One lesion was detected in 4 cases, 2 to 4 lesions were detected in 6 cases, 5 to 10 lesions in 3 cases, and 11 or more in 4 cases. The mean maximum diameter of the polypoid lesions was 7.8 mm (range: 4-16 mm). An upper endoscopy and forceps biopsy were performed in 9 of the 17 cases. The histological diagnosis was fundic gland polyps in 6 cases and hyperplastic polyps in 3 cases.Conclusion: Gastric polypoid lesions can rarely be detected on MRCP. The polypoid lesions were histologically fundic gland polyps or hyperplastic polyps. In the future, we will prospectively review more cases and examine indication of upper gastrointestinal endoscopy to gastric polypoid lesions detected on MRCP.

polyps in 6 cases and hyperplastic polyps in 3 cases.
Conclusion: Gastric polypoid lesions can rarely be detected on MRCP. The polypoid lesions were histologically fundic gland polyps or hyperplastic polyps. In the future, we will prospectively review more cases and examine indication of upper gastrointestinal endoscopy to gastric polypoid lesions detected on MRCP.

Background
Magnetic resonance cholangiopancreatography (MRCP) is a non-invasive magnetic resonance imaging used to visualize the biliary and pancreatic ducts. 1,2 This procedure exploits the water content in the relevant structures, while reducing the background signal from adjacent soft tissues by using a heavily T2-weighted sequence. 1,2 Negative oral contrast agents are administered prior to the examination, which shortens the T2 relaxation time and results in a reduced signal intensity from the uids in the upper gastrointestinal tract. [1][2][3] The negative oral contrast agents cause the gastric lumen to appear dark and can demonstrate gastric polypoid lesions on MRCP. 4 In the present study, we investigate the characteristics of gastric polypoid lesions detected on MRCP.

Patient Population
We retrospectively reviewed MRCP images obtained at our radiology department between January 1 and August 31, 2020 after obtaining approval from the ethical review board. A total of 1158 cases were examined, 18 cases who had undergone a gastrectomy and 12 cases with an insu cient negative contrast effect caused by gastric residuals, uid, and other secretions, were excluded from the study. Therefore, a total of 1128 cases were included in the study.
Imaging MRI scanning was conducted using 1.5-T MR scanners (Signa HD xt, GE Healthcare, Milwaukee, WI, USA or Ingenia Prodiva, Philips Healthcare, Best, Netherlands) or a 3.0-T MR scanner (Intera Achieva, Philips Healthcare, Best, Netherlands)). MRCP was performed with heavily T2-weighted sequences and a torso phased-array coil. Imaging took place after a 6-hour fasting period and immediately after the oral ingestion of manganese chloride tetrahydrate (Bothdel®, Kyowa Hakko Kirin, Chiyoda, Tokyo, Japan).

Evaluation of the images
Two experienced abdominal radiologists (with 9-and 28-years of experience) reviewed the MRCP images that were retrieved from the picture archiving and communication system at our hospital. Discordant interpretations were subsequently resolved by consensus between the two radiologists. Gastric polypoid lesions were de ned as nodules in the stomach, which demonstrated a high intensity with internal low intensity on 2D thick slab MRCP, in reference to axial and coronal T2-weighted SSTSE or SSFSE images ( Fig. 1).
The examination items were as follows: 1. The cases with gastric polypoid lesions were counted and the incidence rate was calculated.
2. The age and gender of these cases were investigated.
3. The portion of the stomach occupied by the polypoid lesions were investigated. The stomach was divided into three parts: upper, middle, and lower, which were divided according to the lines connecting the trisected points on the lesser and greater curvatures. Histological results obtained through a forceps biopsy or resection were investigated. Helicobactor pylori was investigated in samples of gastric biopsy specimens. Use of proton pump inhibitors was examined in the cases with fundic gland polyps.

Results
Characteristics of gastric polypoid lesions detected on MRCP are summarized in Table 1. Hyperplastic polyps 3 1. Polypoid lesions were detected in 17 of the 1128 examined cases, with an incidence rate of 1.5%.
3. In 4 cases, the upper, middle, and lower portions of the stomach were occupied with polypoid lesions, in 4 cases, the upper and middle portions were occupied, in 1 case, the middle and lower portions were occupied, and in 8 cases, only the upper portion was occupied.
4. One lesion was detected in 4 cases, 2 to 4 lesions were detected in 6 cases, 5 to 10 lesions in 3 cases, and 11 or more in 4 cases. 5. The mean maximum diameter of the polypoid lesions was 7.8 mm (range: 4-16 mm).
. An upper endoscopy was performed in 9 cases for evaluating causes of upper gastrointestinal symptoms (n = 4) and examining gastric polypoid lesions detected on MRCP (n = 5). In the remaining 8 cases, gastric polypoid lesions were not detected on MRCP in the initial radiology report. The mean interval between MRCP and endoscopy was 29 days (range; 0-91 days). The upper endoscopies showed gastric polyps in all cases and forceps biopsies were performed during this procedure. In 1 case, an endoscopic mucosal resection was performed. Histological results showed that the lesions were fundic gland polyps (Fig. 2) in 6 cases and hyperplastic polyps (Fig. 3) in 3 cases. Samples of gastric biopsy specimens were Helicobactor pylori negative in all of 9 cases. Two cases of the 6 cases with fundic gland polyps used proton pump inhibitors for 18 and 34 months.

Discussion
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 uidlled structures with a long T2-relaxation time and the adjacent soft tissue which with much shorter T2relaxation 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 respiratorytriggered 3D imaging are utilized. 1,2 The quality of MRCP is frequently degraded by superimposed high signal intensities of the uids in the upper gastrointestinal tract. Therefore, negative oral contrast agents are administered prior to the examination to reduce the superimposed uid signal. [1][2][3] The negative contrast effect is strong T2shortening 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][6][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 attened parietal and mucous cells. 8, 9 In the management, polypectomy is recommended to con rm 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][8][9] They are strongly associated with a chronic in ammatory 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][12][13][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 identi ed 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 [9].

Conclusion
Gastric polypoid lesions can rarely be detected on MRCP. The polypoid lesions were histologically fundic gland polyps or hyperplastic polyps. In the future, we will prospectively review more cases and examine    A 85-year-old female with gastric hyperplastic polyps. Dilation of the main pancreatic duct was detected during a screening ultrasound, therefore, a magnetic resonance cholangiopancreatography (MRCP) was