Peritoneal carcinomatosis is metastatic spread to the peritoneum, most commonly originating from intra-abdominal primary tumors such as ovary, colon, stomach, and pancreas. Tumor cells spread to the peritoneal cavity via free fluid, hematogenous, or lymphatic routes. Omental caking, peritoneal nodules/thickening, ascites, and mesenteric cake appearance are characteristic. Disease extent is assessed using the PCI (Peritoneal Cancer Index) scoring. Treatment includes cytoreductive surgery + HIPEC (hyperthermic intraperitoneal chemotherapy) or systemic chemotherapy. Prognosis depends on primary tumor type and residual disease volume.
Age Range
40-80
Peak Age
60
Gender
Female predominant
Prevalence
Common
Peritoneal carcinomatosis develops through tumor cell dissemination to the peritoneal cavity. The most common mechanism is serosal penetration and transperitoneal dissemination — tumor cells directly invade the peritoneum from the primary organ or are carried by free peritoneal fluid. After implanting on peritoneal surfaces, tumor cells grow through neovascularization and stromal reaction. The greater omentum is particularly a site of attraction for tumor cells because it contains lymphoid aggregates (milky spots) — these areas increase vascular permeability and facilitate tumor implantation. The diffuse infiltration seen as omental caking on imaging results from this process. Ascites arises from increased vascular permeability due to peritoneal irritation and lymphatic drainage obstruction by tumor. CT peritoneal nodules and thickening reflect tumor implant growth on peritoneal surfaces; enhancement indicates neovascularization.
Cake-like thickening formed by diffuse solid/nodular infiltration of greater omentum on CT. Normal omental fat replaced by tumoral soft tissue. Most recognized and pathognomonic finding of peritoneal carcinomatosis. Most prominently seen in peritoneal spread from ovarian, colonic, and gastric origin.
Diffuse cake-like thickening of greater omentum — normal fat tissue replaced by solid or nodular soft tissue infiltration. Omental cake typically located between anterior peritoneal surface and transverse colon. Shows heterogeneous enhancement. In advanced stages, appears as solid plaque covering the entire omentum.
Report Sentence
Diffuse cake-like soft tissue thickening of the greater omentum is observed, consistent with peritoneal carcinomatosis (omental caking).
Enhancing nodules and irregular thickening on parietal and visceral peritoneal surfaces. Nodules may range from millimetric to centimeter-sized plaques. Pelvic peritoneum, pouch of Douglas, paracolic gutters, and subdiaphragmatic areas are most commonly involved. Smooth thickening associates with benign ascites, while nodular/irregular thickening indicates malignant peritoneal disease.
Report Sentence
Enhancing nodular thickening on peritoneal surfaces is observed, consistent with peritoneal carcinomatosis.
Free or loculated ascites — ascites in peritoneal carcinomatosis typically shows higher density (>15 HU, proteinaceous). May contain septations and debris. Volume ranges from minimal to massive. Loculated ascites indicates peritoneal adhesions. Ascites density may be chylous (low), serous (intermediate), or hemorrhagic (high).
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Free fluid (ascites) is observed in the abdomen, consistent with malignant ascites in the context of peritoneal nodularity.
Nodular infiltration, thickening, and retraction of mesenteric leaves. Encasement of mesenteric vascular structures by tumor. In advanced stages, 'frozen pelvis' or 'frozen abdomen' appearance — bowel loops adherent and immobile. Mesenteric cake appearance together with omental cake indicates advanced peritoneal carcinomatosis.
Report Sentence
Nodular infiltration and retraction of mesenteric leaves is observed, consistent with peritoneal carcinomatosis.
Increased FDG uptake on peritoneal surfaces, omentum, and mesentery. Diffuse or focal uptake patterns may be seen. PET-CT can detect small peritoneal implants that may be missed on CT. SUVmax typically >2.5, varying with primary tumor type. Metabolic activity change is monitored as a critical parameter in treatment response follow-up.
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Increased FDG uptake on peritoneal surfaces and omentum on PET-CT is observed, consistent with peritoneal carcinomatosis.
Diffusion restriction in peritoneal nodules and omental cake on DWI — hyperintense on high b-value (b=800-1000), hypointense on ADC map. Diffusion restriction reflects high cellularity of tumor deposits. MRI, especially with DWI, is superior to CT in detecting small peritoneal implants.
Report Sentence
Diffusion restriction on peritoneal surfaces and omental cake on DWI is observed, consistent with peritoneal carcinomatosis.
Nodular thickening of peritoneal surfaces in the setting of ascites on US. Omental cake may appear as hyperechoic or heterogeneous mass. Septated ascites favors malignant ascites. US is superior to CT in fluid-solid differentiation and septation detection but limited in assessing full extent of peritoneal disease.
Report Sentence
Nodular thickening of peritoneal surfaces in the setting of ascites on US is observed, consistent with malignant peritoneal disease.
Criteria
Peritoneal spread from ovarian malignancy. Most commonly high-grade serous carcinoma. Bilateral ovarian mass + omental cake + ascites triad is classic presentation. Elevated CA-125 supports diagnosis. Subtype with best prognosis with cytoreductive surgery + chemotherapy.
Distinct Features
Bilateral ovarian masses, massive ascites, elevated CA-125, supracolic and infracolic involvement
Criteria
Peritoneal spread of colorectal cancer. More common in mucinous type or T4 tumors. Omental cake along with mesenteric nodules and peritoneal implants are seen. HIPEC + cytoreductive surgery is particularly effective in limited peritoneal disease (PCI <20).
Distinct Features
Colon primary mass, mucinous implants (low density), elevated CEA, may accompany liver metastases
Criteria
Peritoneal spread of mucinous tumor from appendix or ovary. Accumulation of gel-like mucinous material in peritoneal cavity. Low-density (<20 HU) cystic/gelatinous collections, scalloping (indentation of liver and spleen surfaces), and peritoneal mucinous implants are characteristic on CT.
Distinct Features
Low-density mucinous collections, liver/spleen scalloping, appendiceal mass, indolent course
Criteria
Peritoneal spread of gastric cancer. Particularly high risk in diffuse type (linitis plastica) and T3-T4 stage. Krukenberg tumor (ovarian metastasis) may accompany. Prognosis is generally poor. Douglas pouch involvement (Blumer shelf) may give characteristic rectal examination finding.
Distinct Features
Gastric wall thickening, Krukenberg tumor, Douglas pouch involvement, poor prognosis
Distinguishing Feature
Peritoneal lymphomatosis shows homogeneous soft tissue thickening while carcinomatosis shows nodular thickening; lymphoma typically has less ascites with accompanying retroperitoneal lymphadenopathy
Distinguishing Feature
Mesenteric lymphoma forms prominent masses with 'sandwich sign'; peritoneal carcinomatosis is characterized by diffuse peritoneal thickening and omental caking
Distinguishing Feature
Intra-abdominal abscess shows rim enhancement, gas bubbles, and perifocal inflammation; carcinomatosis shows nodular solid enhancement and omental caking; fever and leukocytosis in clinical context favor abscess
Distinguishing Feature
Peritoneal endometriosis shows T1 hyperintense (hemorrhagic content) lesions typically in young women with pelvic pain and dysmenorrhea; carcinomatosis shows T1 hypointense nodules with malignancy history in older patients
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralPeritoneal carcinomatosis indicates advanced-stage malignancy and requires multidisciplinary tumor board evaluation. Cytoreductive surgery + HIPEC can improve survival in appropriate patients (low PCI, good performance status). Biopsy is needed for histopathological confirmation and primary site identification. CA-125, CEA, and other tumor markers aid primary site investigation. Palliative care planning should be initiated early.
Peritoneal carcinomatosis generally indicates advanced-stage disease and carries poor prognosis. Cytoreductive surgery with HIPEC (hyperthermic intraperitoneal chemotherapy) can improve survival in selected patients. PCI (peritoneal carcinomatosis index) is used for staging.