The Many Faces of the Angry Peritoneum

Abstract

The peritoneum is a thin membrane that lines the abdominal cavity and covers the abdominal organs. It serves as a conduit for the spread of various pathological processes, including gas and fluid collections, inflammation, infections, and neoplastic conditions. Peritoneal carcinomatosis is the most common and well-known pathology involving the peritoneum, typically resulting from the dissemination of gastrointestinal and pelvic malignancies. However, numerous benign and malignant peritoneal diseases can mimic the imaging appearance of peritoneal carcinomatosis. The aim of this review is to revisit the anatomy of peritoneal compartments and elucidate the patterns of peritoneal disease spread. Emphasis is placed on identifying the distinctive imaging features of both neoplastic and non-neoplastic peritoneal diseases that differ from peritoneal carcinomatosis.

Keywords: disease pathways; peritoneal carcinomatosis; peritoneum.

Figure 1

PC from gastric adenocarcinoma. An old man who underwent gastrectomy for gastric adenocarcinoma 2 years before. At follow up, axial CECT shows subtle soft tissue mass occupying the periportal space with vessel occlusion ((a), arrow), macro-nodular thickening of the posterior parietal peritoneum ((b), arrow), and micro-nodular thickening of the falciform ligament and posterior diaphragmatic peritoneal reflection ((c), arrow).

Figure 2

(a) PC from sigmoid carcinoma. An old woman. Follow-up CECT shows a macro-nodular implant located on the anterior abdominal wall (arrow) and a subtle deposit of the visceral peritoneum lining the last ileal loop (theca pattern, dashed arrow). (b) (Different case to (a)) PC from carcinoma of the colon. A middle-aged man. Follow-up CECT shows massive thickening of the omentum called an “omental cake” (star). Diffuse thickening of the peritoneal layer is also visible (arrow).

Figure 3

PC from pancreatic adenocarcinoma. An old woman with unresectable adenocarcinoma of the body–tail of the pancreas. CECT shows the primitive lesion ((a), coronal plane, asterisk) and large subcapsular deposits with splenic invasion along the lower surface of the left diaphragm ((a), arrow), micro-nodular omental deposits ((b) arrow and (d) dashed arrow), deposits along the left paracolic gutter ((d), arrow), and secondary lesions to both the ovaries ((c), asterisk).

Figure 4

PC from ovary carcinoma. CECT of an old woman with large heterogeneus mass of the ovary (mass-like) with psammoma body ((d), arrow) and large confluent solid implants forming mass-like PC. Note the large nodules which are not cleavable from the stomach and duodenum ((a), axial, arrow, and (b), sagittal plane, arrow) and from the ascending colon ((c), axial plane, arrow).

Figure 5

Peritoneal mesothelioma. An old man with abdominal pain. CECT on the axial plane reveals a large solid heterogeneous mass not cleavable to the cecum ((a), arrow) located in the mesentery ((b), arrow) along the large omentum ((c,d) arrows) and along the serosal surface of the small bowel ((d), dashed arrow).

Figure 6

Peritoneal sarcomatosis. A middle-aged man. CECT was made during follow-up after GIST removal. In the first image, ((a), arrow) a hypervascular solid nodule is depicted in the mesentery. After 6 months, the same nodule became larger (CT (b), arrow) and showed FDG uptake at PET-CT (c).

Figure 7

Angiomyofibroblastoma. A middle-aged woman. CT and MRI show a voluminous non-infiltrative peritoneal and pelvic lesion encasing the small bowel loops ((a): coronal portal venous phase CT; (b): axial T2-weighted MRI; (c): axial venous phase MRI. Indicated by arrows).

Figure 8

Peritoneal lymphomatosis (large B-cell lymphoma). A middle-aged woman with large B-cell lymphoma involving the left kidney, the pancreas, and the retroperitoneal space ((a), asterisk) with peritoneal lymphomatosis. CECT on the axial plane shows omental caking ((b), dashed arrow), solid tissue along the left iliac vessels ((b), arrow), and peritoneal seeding along the peritoneum which covers the pelvic wall ((c), arrow). (FDG) PET-CT shows diffuse FDG uptake of the lymphoma and peritoneal diffusion sites (d).

Figure 9

Peritoneal metastasis from ileal carcinoid. A middle-aged man with abdominal pain and episodes of subocclusion. CECT is made and shows a solid large mesenteric mass with a stellate appearance ((a,b), arrow). Focal vascularized thickening of the adjacent small bowel wall is visible and there is suspicion of a primary neuroendocrine tumor ((a), dashed arrow). Small nodules are visible along the large omentum and are indicative of peritoneal seeding ((a), large arrow).

Figure 10

Mesenteric pseudocyst. A middle-aged woman with abdominal pain and a palpable mass in the right hypocondrium. US reveals a large cystic anechoic mass of unknown origin located next to the liver hilum with a thin nonvascularized septum ((a), arrow; star on the septum). CE-CT shows a large cystic mass located anteriorly to the ascending colon ((b,c): arrows). A small amount of fluid which may be secondary to cyst rupture is visible in the pelvis ((d): arrow).

Figure 11

Epiploic appendagitis. A middle-aged man with abdominal pain mainly located on the left upper quadrant. Portal venous phase CT shows a fat-density, round, and small lesion surrounded by a high-attenuation rim (hyperattenuating ring sign) abutting anteriorly the descending colon ((a): axial, (b): coronal, and (c): sagittal images; arrows).

Figure 12

Perigastric appendagitis. A middle-aged woman with mild abdominal pain. At CT, a heterogeneous, fat-density, ovoidal lesion with mild surrounding fat stranding along the course of the gastrohepatic ligament is visible (arrow).

Figure 13

Mesenteric panniculitis. A middle-aged man, asymptomatic. CECT, made for blunt abdominal trauma, reveals hypertrophy of the mesenteric adipose tissue with soft tissue infiltration, a ring of normal fat surrounding the vessels and lymph nodes (fat ring sign) and a pseudocapsule ((a): coronal and (b): axial, arrows). MRI is made for further investigation: no significant restriction of diffusion is found (c) and mild hyperintensity is found on the T2-weighted image (d).

Figure 14

Subperitoneal spread of necrotizing pancreatitis. A middle-aged man with acute necrotizing pancreatitis. CECT made at follow-up after 7 days from the onset of the abdominal symptoms. Large necrotic collections are visible involving the pancreatic gland and the peripancreatic tissue (a). Small micro-nodular seeding of necrosis is visible along the posterior parietal peritoneum ((a,b), arrows), typical of pancreatitis and secondary to subperitoneal spread.

Figure 15

Pelvic inflammatory disease (PID). Two young women with a long history of pelvic pain and purulent vaginal discharge. In the first case, portal venous phase abdominal CT is performed (a) and shows the increased attenuation of the pelvic fat, peritoneal fluid with peritoneal enhancement (arrow), and complex solid-cystic-enhancing masses in both adnexal regions (asterisks); Chlamydia trachomatis is detected as the causal agent. In the second case, pelvic MRI is performed. On T2-weighted axial images (b), left tubal distention with thickened walls (arrow) is appreciable. On contrast-enhanced fat-saturated T1-weighted axial images (c), increased enhancement of the peritoneal spaces as well as of the left salpinx (arrow) is evident. The etiology in this case is polymicrobial.

Figure 16

Tubercular peritonitis. A young woman with progressive abdominal pain and an increased abdominal circumference. Portal venous phase abdominal CT is performed due to the suspicion of oncological disease and shows abundant peritoneal fluid associated with diffuse and smooth thickening of the parietal peritoneum ((a): coronal and (b): axial, arrows) with no focal thickening or nodules.

Figure 17

Retractile mesenteritis as an outcome of atypical micobatteriosis. A middle-aged woman with an old and long history of atypical micobatteriosis. CECT during follow-up shows a spiculated mesenteric mass with the same calcified foci ((a): coronal, (b,c): axial plane; arrows).

Figure 18

Post-traumatic mesenteric injuries. Total-body CECT made for a middle-aged man after a car accident. CECT reveals mesenteric blood infiltration ((a), asterisks) with active contrast leaking during the post-contrast arterial phase ((b), arrow).

Figure 19

Hemoperitoneum. A young woman with acute subacute abdominal pain, anemisation, and no history of trauma. Free fluid was detected at ultrasound and portal venous phase abdominal CT was requested. Coronal CT reconstruction (a) shows a diffuse peritoneal effusion. On axial reconstruction (b), the peritoneal fluid shows high attenuation values in the dependent portions (52 HU). Moreover, the right ovary appears increased in size (arrow). The patient underwent explorative laparotomy, and a ruptured luteal cyst in the right adnexa was detected as the cause of the hemoperitoneum.

Figure 20

Splenosis. A middle-aged man with previous surgical intervention of a left emicolectomy and splenectomy. At CECT, rounded solid nodules (arrows) are seen in the left hypochondrium, with inhomogeneous enhancement in the arterial phase (a) and homogeneous enhancement in the portal phase (b).