Omental implant

The omentum accounts for the most common sites of peritoneal metastases, with the inframesocolic omentum more often involved than the supramesocolic omentum. Most common types of omental implants include a net-like pattern,nodules of various sizes, and broad, bandlike soft-tissue lesions, an omental cake (Fig. 10.8). Nodular enhancing implants and omental cake are typically located between the abdominal wall and bowel loops. 

Fig. 10.8a-d. Omental implants. Transaxial CT (a-c) and transaxial fat-saturated Tl-weighted image (d) in four different patients. Omental implants (arrows) may display a broad spectrum of findings ranging from a netlike pattern (a) to cottonlike (b) and nodular lesions (d). They are typically located between the abdominal wall and bowel loops. If they coalesce they are termed omental cake (c)... 

Repeated episodes of catheter obstruction by fibrin clots or omental encapsulation can be a problem during continuous peritoneal insulin infusion from implanted pumps (SEDA 20, 397). In the encapsulated tissue, collagen fibrosis, inflammatory reactions with lymphocytes, and amyloid-like deposits reacting to anti-insulin antibodies can occur higher macrophage chemotaxis may also promote these processes. 

Presence of ascites, omental involvement, serosal implants, mesenteric involvement, peritoneal implants, and interruption of the anterior peritoneal line are the most frequently described ultrasonographic findings in patients with peritoneal metastasis. Accessory findings are represented by liver metastasis, lymphadenopathies, and gallbladder... 

Netlike omental involvement is more difficult to evaluate. Implants of the diaphragm consist of nodular or plaquelike lesions. Peritoneal implants of liver or spleen may result in scalloping of the surface. Ligaments may appear thickened due to peritoneal metastases. Implants on bowel or mesentery can cause tethering of loops and may lead to obstruction. Bowel obstruction,however, results more commonly from intestinal wall involvement than from serous implants. Mesenteric lesions appear as thickening of the root of the mesentery, and often display a stellate radiating pattern. 

Stage III consists ofextrapelvic peritoneal implants and/or inguinal or retroperitoneal lymphadenopathy. Peritoneal lesions outside the pelvis, omental, or mesenteric implants are typical findings in stage III ovar-... 

Regarding Y-shaped tubular scaffolds, a limited experimentation has been conducted. Sekine et al. [ 130] implanted a Y-shaped Marlex mesh tube in dogs. The tubes were reinforced with polypropylene spiral and coated with collagen from porcine skin. Six of the 20 dogs have survived after experimentation. The main causes of death were obstmction of the main bronchus, omental necrosis, and air leakage. The same prosthesis was grafted as tracheobronchial bifiircalion replacement after 5 years, the scaffold was completely incorporated. Neitho- stenosis nor dehiscence was observed, and a functional airway was revealed [131]. 

None of the currently reported sites employed for islet transplantation, i.e., the liver, the spleen, beneath the renal capsule and the omental porch and the peritoneal cavity, " combine the capacity to bear high numbers of islets and retrievability of the islet graft. However, a site with both features may be a mandatory for large-scale clinical transplantation of encapsirlated islets, because such grafts stiU have their functional limitations and, therefore, may require repeated replacement. Recently, the concept of an intraperitoneally implanted solid support as a transplantation site for genetically-engineered cells has been proposed." Such a solid support may serve as a transplantation site for pancreatic islets as, theoretically, it allows for implantation of high numbers of islets that can be readily retrieved. 

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