X-ray Corner. Imaging of The Peritoneum and Mesentery. Pantongrag-Brown L. Case 1. A 47-year-old woman presenting with abdominal distension.

Transcription

1 X-ray Corner Pantongrag-Brown L THAI J GASTROENTEROL 2016 Vol. 17 No. 3 Sep. - Dec Pantongrag-Brown L Modern imaging modalities commonly used in peritoneum and mesentery include ultrasound (US), CT, and MRI. US is good for detection of ascites, but may be a limited tool for finding the etiologies of peritoneal and mesenteric diseases. CT or MRI is usually needed for further investigation. CT is slightly favorable to MRI for visualization of intra-abdominal cavity. This is because MRI is sensitive to bowel peristalsis and severe motion artifact may obscure the detail within the peritoneal cavity. In this article, several peritoneal and mesenteric abnormalities will be demonstrated, using case-based approach, and emphasizing on imaging findings. Case 1. A 47-year-old woman presenting with abdominal distension. Figure 1. Case 1. Advanced Diagnostic Imaging Center, Ramathibodi Hospital, Bangkok, Thailand. Address for Correspondence: Linda Pantongrag-Brown, M.D., Advanced Diagnostic Imaging Center, Ramathibodi Hospital, Bangkok, Thailand.

2 188 THAI J GASTROENTEROL 2016 Axial views of CT scan show multiple lymphadenopathy surrounding the abdominal aorta, giving the appearance of floating aorta sign. Some of large nodes show low-density necrosis. Minimal ascites is observed. D/Dx of multiple intra-abdominal lymphadenopathy includes lymphoma, metastasis, and TB. The appearance of necrotic nodes gives TB the most likely diagnosis. Nodal biopsy reveals caseous necrosis with positive acid fast bacilli. Final diagnosis is TB peritonitis. The floating aorta sign refers to displacement of the abdominal aorta away from the vertebral column. Any retroperitoneal mass arising posterior to the aorta can insinuate between the aorta and the vertebral column, and displace the aorta anteriorly; hence the term floating aorta sign. It is a radiographic/ CT sign of retroperitoneal mass or lymphadenopathy (1). The abdomen is the most common site of extrapulmonary tuberculosis, and peritoneal disease is the most common form within the abdomen. Abdominal tuberculosis can also involve the solid organs, gastrointestinal tract, mesentery and lymph nodes (2). CT imaging features seen with tuberculous peritonitis include nodular thickening of the peritoneum and mesentery, abnormal peritoneal or mesenteric enhancement, ascites, and low attenuating lymphadenopathy. Low-density lymphadenopathy is secondary to caseous necrosis and is a clue for prospective diagnosis of TB. Case 2. A 46-year-old woman presenting with abdominal distension. Figure 2. Case 2. Axial views of CT scan show nodular thickening of the peritoneum; nodular depositions along the liver surface, gastrohepatic ligament, and gastrosplenic ligament (thick arrows). Ascites and a thick omental cake are observed (thin arrows). Findings are consistent with peritoneal carcinomatosis. Primary tumor is ovarian cancer showing as a large, lobulated contour mass within the pelvis. Differential diagnosis of omental cake includes peritoneal carcinomatosis, pseudomyxoma peritonei,

3 Pantongrag-Brown L THAI J GASTROENTEROL 2016 Vol. 17 No. 3 Sep. - Dec peritoneal mesothelioma, peritoneal lymphomatosis, primary peritoneal serous carcinoma, and peritoneal TB. Searching for primary tumor within the abdomen will help pinpoint diagnosis towards carinomatosis peritonei, such as in this case. Common primaries include ovarian cancer, GI tract malignancy, breast cancer, lung cancer, and malignant melanoma (3). Case 3. A 47-year-old man, presenting with abdominal pain. Figure 3. Case 3. Axial views of CT scan show multiple homogeneous, bulky lymphadenopathy involving diaphragmatic, mesenteric and peri-aortic region. The aorta is lifted above the vertebral body, giving the appearance of the floating aorta sign. The stomach shows irregular thickened wall (arrow). Moderate amount of ascites is noted. D/Dx of multiple intra-abdominal lymphadenopathy includes lymphoma, metastasis, and TB. The appearance of bulky, homogeneous lymphadenopathy gives lymphoma the most likely diagnosis. Biopsy of the stomach confirms the diagnosis of lymphoma. Lymphoma can present as nodal or extra-nodal disease. Multiple sites and multiple organs of involvement are hallmark of lymphoma. The etiology is unknown but potential risk factors include viral infection (e.g. EBV, HTVL-1, HIV, HCV, HSV), bacterial infection (e.g. Helicobacter pylori), and chronic immunosuppression (e.g. post-transplantation) (4). Lymphoma is classified into Hodgkin lymphoma, and non-hodgkin lymphoma. Imaging characteristics will depend on the location and subtype of lymphoma. CT is usually the imaging of choice for staging of lymphoma.

4 190 THAI J GASTROENTEROL 2016 Case 4. A 57-year-old man presenting with abdominal pain and weight loss. Figure 4. Case 4. Axial views of CT scan shows marked thickened wall of the stomach (thin arrow) with multiple mesenteric lymphadenopathy. A large omental cake (thick arrow) displaces bowel loops inwardly. Minimal ascites is noted. Differential diagnosis of omental cake includes peritoneal carcinomatosis, pseudomyxoma peritonei, peritoneal mesothelioma, peritoneal lymphomatosis, primary peritoneal serous carcinoma, and peritoneal TB. In this case, an irregular gastric mass, associated with lymphadenopathy makes lymphoma, and primary gastric cancer with nodal metastasis the most likely diagnosis. Biopsy of the gastric wall reveals primary adenocarcinoma. Adenocarcinoma is the most common gastric malignancy, representing over 95% of malignant tumors of the stomach (5). Endoscopy is regarded as the most sensitive and specific diagnostic method in patients suspected of gastric cancer. Endoscopy allows direct visualization of the tumor, and biopsy for tissue diagnosis. However, imagings are often the initial examination that raise suspicion for gastric carcinoma. Moreover, CT is currently the modality of choice for staging, because it can help identify the primary tumor, assess the local spread, and detect nodal involvement and distant metastasis. Case 5. A 65-year-old man presenting with abdominal pain and distension. Figure 5. Case 5.

5 Pantongrag-Brown L THAI J GASTROENTEROL 2016 Vol. 17 No. 3 Sep. - Dec Axial views of CT scan show massive ascites with calcified, thick pleural plaque (thin arrow). Omental cake and peritoneal depositions (thick arrows) are observed. Small bowel loops are matted and conglomerated in the central abdomen. Differential diagnosis of omental cake includes peritoneal carcinomatosis, pseudomyxoma peritonei, peritoneal mesothelioma, peritoneal lymphomatosis, primary peritoneal serous carcinoma, and peritoneal TB. In this case, a calcified pleural plaque is a clue of possible asbestos exposure or chronic infection. Therefore, peritoneal mesothelioma or TB peritonitis is the most likely diagnosis. Biopsy of the omental cake reveals peritoneal mesothelioma. Peritoneal mesothelioma is an uncommon primary tumor of the peritoneal lining. It shares epidemiological and pathological features with but is less common than its pleural counterpart. As with pleural mesothelioma, there is also a strong association with asbestos exposure. Presence of calcified pleural or peritoneal plaque is an important characteristic of asbestos exposure. Peritoneal mesothelioma is a malignant tumor but tend to be localized. Metastasis to distant organs and lymphadenopathy are uncommon (6). Case 6. A 35-year-old female presenting with abdominal discomfort. Figure 6. Case 6. US and CT scan show multiloculated cysts involving the entire lower abdomen. The cysts insinuate around the tissue and does not cause small bowel obstruction. D/Dx of multiloculated cysts in a relatively young female include cystic mesothelioma, lymphangioma, and cystic tumor of the ovary. Biopsy of the lesion confirms the diagnosis of cystic mesothelioma. Cystic mesothelioma is relatively rare and occur predominantly in young to middle-aged women. In contrast to malignant peritoneal mesothelioma, this tumor has no association with asbestos exposure, but it is commonly associated with a history of previous abdominal surgery or pelvic inflammatory disease. Involvement of the pelvic region is characteristic. Cystic mesothelioma is considered benign but recurrence is common after surgical resection (7).

6 192 THAI J GASTROENTEROL 2016 Case 7. A 73-year-old man presenting with abdominal mass. Figure 7. Case 7. Small bowel follow-through study shows dilated and thickened small bowel loops encircling around a soft-tissue lesion. CT scan shows a calcified mesenteric mass, associated with surrounding linear strandings, radiating from the central calcification to the adjacent small bowel loops. Surrounding small bowels show diffuse thickened wall and tethering towards linear strandings. D/Dx of calcified mesenteric mass includes mesenteric carcinoid, retractile mesenteritis, lymphoma, and metastasis. The triad of a calcified mesenteric mass, radiating strands, and adjacent bowel-wall thickening is highly suggestive of carcinoid tumor. Surgery was performed and pathology confirms the diagnosis of mesenteric carcinoid. Mesenteric carcinoid tumor is almost always due to a metastasis from a carcinoid tumor of the small bowel beyond the ligament of Treitz. Primary carcinoid tumor of the mesentery is rare. Indeed, its existence is questionable, because the primary site within the small bowel could be occult. The nidus of tumor growth within the mesentery is probably lymph node. The characteristic CT finding is a triad of a calcified mesenteric mass, radiating strand, and adjacent bowelwall thickening (8). The linear radiating strands observed in the mesentery are due largely to the fibrotic process. This profound desmoplastic response is caused by hormonally active substances, especially serotonin, secreted by carcinoid tumor. These same hormones also provoke desmoplastic effects within the bowel wall and along the mesenteric vessels, resulting in ischemia and edema of the surrounding small bowel loops.

7 Pantongrag-Brown L THAI J GASTROENTEROL 2016 Vol. 17 No. 3 Sep. - Dec Case 8. A 58-year-old man presenting with abdominal mass. Figure 8. Case 8. Small bowel follow-through study shows a large abdominal mass displacing small bowel loops peripherally. CT scan confirms a large, well-defined mass with relatively homogeneous density and moderate vascularity. D/Dx of a large mesenteric mass includes desmoid tumor, mesenteric sarcoma (e.g. leiomyosarcoma, liposarcoma, MFH), and lymphoma. Surgery was performed and proved to be a desmoid tumor. Desmoid tumor is derived from musculo- apo- neurotic structures throughout the body. In spite of its large size, the tumor tends to be homogeneous and welldefined on CT, which is an important clue to diagnosis. In the mesentery, the mass may occur sporadically or be associated with familial adenomatous polyposis (FAP) and Gardner syndrome. Desmoid tumor has a tendency to recur, even after complete surgical resection (9). Case 9. A 55-year-old man presenting with abdominal mass. Figure 9. Case 9.

8 194 THAI J GASTROENTEROL 2016 Axial views of CT scan shows a large mesenteric mass, displacing small bowel loops peripherally. The mass contains fatty strands (arrow). D/Dx of a large mesenteric mass includes desmoid tumor, mesenteric sarcoma (e.g. leiomyosarcoma, liposarcoma, MFH), and lymphoma. A fatty strands within the mass are suggestive of liposarcoma. Surgery was performed and proved to be liposarcoma. Liposarcoma is a malignant tumor of fatty tissue and is the malignant counterpart to a benign lipoma. Liposarcoma is thought to originate from mesenchymal cells, and retroperitoneum is the most common site within the abdomen. Primary mesenteric liposarcoma is rare. Among the malignant mesenteric tumors, lymphoma is the most common followed by leiomyosarcoma. The treatment of choice for liposarcoma is surgical excision with appropriate margins followed by radiation with or without adjuvant chemotherapy in high risk patients (10). CONCLUSIONS Nine cases of peritoneal and mesenteric diseases are illustrated, emphasizing on the imaging appearances. These cases are as following: 1. Neoplastic pathology: a. Peritoneal carcinomatosis, primary ovarian cancer b. Peritoneal carcinomatosis, primary gastric cancer c. Peritoneal mesothelioma d. Cystic mesothelioma e. Lymphoma f. Mesenteric liposarcoma g. Mesenteric carcinoid tumor h. Mesenteric desmoid tumor 2. Infectious/inflammatory pathology: a. Peritoneal TB REFERENCES 1. Havrilla TR, Reich NE, Haaga JR. The floating aorta in computerized tomography: a sign of retroperitoneal pathology. Clin Imag p Suri S, Gupta S, Suri R. Computed tomography in abdominal tuberculosis. Br J Radiol 1999;72: Levy AD, Shaw JC, Sobin LH. Secondary tumors and tumorlike lesions of the peritoneal cavity: imaging features with pathologic correlation. Radio Graphics 2009; 29: Frampas E. Lymphomas: Basic points that radiologists should know. Diagn Interv Imaging 2013;94: Horton KM, Fishman EK. Current role of CT in imaging of the stomach. Radio Graphics 2003;23: Park JY, Kim KW, Kwon H, et al. Peritoneal Mesotheliomas: clinicopathologic features, CT findings, and differential diagnosis. AJR 2008;191: Weiss SW, Tavassoli FA. Multicystic mesothelioma: an analysis of pathologic findings and biologic behavior in 37 cases. Am J Surg Pathol 1988;12: Pantongrag-Brown L, Buetow PC, Carr NJ, et al. Calcification and fibrosis in mesenteric carcinoid tumor: CT findings and pathologic correlation. AJR 1995;164: Faria SC, Iyer RB, Rashid A, et al. Desmoid tumor of the small bowel and the mesentery. AJR 2004; 183: Jain SK, Mitra A, Kaza RCM, et al. Primary mesenteric liposarcoma: an unusual presentation of a rare condition. J Gastrointest Oncol 2012;3: