Peritoneal sarcoidosis is a rare extrathoracic manifestation of systemic sarcoidosis characterized by non-caseating granulomatous inflammation of the peritoneum, omentum, or mesentery. Peritoneal involvement is seen in <5% of all sarcoidosis patients. Histopathologically, well-formed non-caseating granulomas (which may contain Schaumann and asteroid bodies) are diagnostic. CT shows peritoneal/omental thickening, multiple small soft tissue nodules, and abdominal lymphadenopathy. Differential diagnosis from peritoneal carcinomatosis is critical. Serum ACE level may be elevated but has low specificity. Treatment with corticosteroids is effective and most cases respond well.
Age Range
20-50
Peak Age
35
Gender
Equal
Prevalence
Rare
Sarcoidosis is a T-helper lymphocyte-mediated granulomatous disease of unknown etiology. In peritoneal involvement, peritoneal macrophages and T-lymphocytes form organized non-caseating granulomas in response to antigen stimulation. These granulomas consist of epithelioid histiocytes, giant cells (Langhans type), and surrounding lymphocytes. The non-caseating feature distinguishes from TB, as there is no central necrosis — this explains the absence of low-density central necrosis on CT. Granulomas accumulate as small nodules on peritoneal surfaces, and these nodules appear as enhancing soft tissue nodules on CT. Abdominal lymph nodes are also involved through lymphatic drainage. ACE is secreted from granuloma cells and serum levels may reflect disease activity. Chronic inflammation may lead to peritoneal fibrosis and ascites development.
Multiple small, homogeneously enhancing, non-necrotic peritoneal nodules on CT — accompanied by bilateral hilar and mediastinal lymphadenopathy. This combination is highly characteristic of peritoneal involvement of systemic sarcoidosis.
Multiple small (<1 cm), well-defined, homogeneously enhancing soft tissue nodules on peritoneal surfaces on CT. Omental thickening ('omental cake'-like but thinner and nodular). Peritoneal thickening may be diffuse or focal. Small amount of ascites may accompany. Nodules are small and smooth-contoured, different from the thick, irregular implants in carcinomatosis.
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Multiple small, homogeneously enhancing nodules and diffuse peritoneal thickening are seen on peritoneal surfaces; may be consistent with peritoneal sarcoidosis.
Multiple enlarged abdominal lymph nodes — retroperitoneal, mesenteric, and at the porta hepatis level. Lymph nodes are homogeneous, non-necrotic, moderately enhancing. No central necrosis (differentiating from TB). Diagnostic value increases when accompanied by bilateral hilar and/or mediastinal lymphadenopathy.
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Multiple enlarged, homogeneous, non-necrotic retroperitoneal and mesenteric lymph nodes are seen; sarcoidosis should be considered as the leading diagnosis in the presence of bilateral hilar LAP.
Peritoneal nodules show low to intermediate signal on T2-weighted images. The fibrotic content of sarcoid granulomas creates T2 hypointensity. This differs from the T2 hyperintensity of carcinomatous implants. Lymph nodes also show homogeneous, intermediate signal on T2.
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Peritoneal nodules show low to intermediate signal on T2-weighted sequence; this finding consistent with granulomatous disease is valuable in differentiation from carcinomatosis.
Peritoneal nodules and lymph nodes show moderate FDG uptake on PET-CT. FDG uptake reflects active granulomatous inflammation. Decrease in FDG uptake is used for treatment response assessment. FDG uptake overlapping with malignancy may complicate differential diagnosis.
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Moderate FDG uptake is seen in peritoneal nodules and abdominal lymph nodes on PET-CT; consistent with active granulomatous disease, but malignancy should be excluded.
Hepatosplenomegaly and millimetric hypodense nodules in liver/spleen may be seen on non-contrast CT. These nodules represent hepatic and splenic granulomas. Combined with peritoneal involvement, shows the extent of abdominal sarcoidosis.
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Millimetric hypodense nodules are seen in the liver and spleen with hepatosplenomegaly; consistent with hepatosplenic granulomas and should be evaluated in the context of sarcoidosis.
Peritoneal nodules and lymph nodes may show mild to moderate diffusion restriction on DWI. ADC values are intermediate and generally higher than malignant lesions. This reflects cellular density in active granulomatous inflammation. DWI is useful for monitoring treatment response — diffusion restriction decreases with treatment.
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Peritoneal nodules show mild diffusion restriction on DWI; ADC values are higher than malignant lesions, consistent with granulomatous disease.
Criteria
Discrete nodules on peritoneal surfaces. Most common form. Carcinomatosis differential important.
Distinct Features
Small (<1 cm), well-defined, homogeneously enhancing nodules on CT; low to intermediate T2 signal.
Criteria
Smooth or mildly irregular peritoneal thickening. Ascites may accompany. Mesothelioma and TB differential.
Distinct Features
Smooth-contoured peritoneal thickening on CT; accompanied by non-necrotic lymphadenopathy.
Criteria
Nodular thickening or mass in omentum. May have omental cake-like appearance but is thinner and more nodular.
Distinct Features
Thinner than ovarian carcinoma omental cake; homogeneous enhancement; ascites amount usually small.
Distinguishing Feature
Carcinomatous implants are larger, irregularly marginated and T2 hyperintense; sarcoid nodules are small, well-defined and T2 hypointense. Carcinomatosis has primary tumor history.
Distinguishing Feature
TB peritonitis lymph nodes show central necrosis (rim enhancement); sarcoidosis lymph nodes enhance homogeneously without necrosis.
Distinguishing Feature
Lymphoma shows larger conglomerate lymph node masses and sandwich sign; sarcoidosis shows smaller, scattered lymph nodes and bilateral hilar LAP.
Distinguishing Feature
Mesothelioma shows thicker, irregular peritoneal thickening and large pleural effusion; sarcoidosis shows thin, nodular thickening and small ascites.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthPeritoneal sarcoidosis diagnosis must be confirmed by biopsy because differential diagnosis from carcinomatosis and TB is critical. Laparoscopic biopsy demonstrating non-caseating granuloma is the gold standard. Corticosteroids (prednisolone 20-40 mg/day) are effective in treatment and most cases respond well. Methotrexate or azathioprine is used in steroid-resistant cases. Treatment response is monitored with CT and serum ACE. Prognosis is generally good and mortality is low.
Peritoneal sarcoidosis is rare but important to recognize. Corticosteroid therapy is effective. Biopsy may be needed for differential diagnosis from lymphoma and TB. Non-caseating granulomas establish histologic diagnosis.