- Pictorial Review
- Open Access
Omental cakes: unusual aetiologies and CT appearances
© European Society of Radiology 2011
- Received: 24 February 2011
- Accepted: 5 May 2011
- Published: 22 May 2011
Omental cakes typically are associated with ovarian carcinoma, as this is the most common malignant aetiology. Nonetheless, numerous other neoplasms, as well as infectious and benign processes, can produce omental cakes.
A broader knowledge of the various causes of omental cakes is valuable diagnostically and to direct appropriate clinical management.
We present a spectrum of both common and unusual aetiologies that demonstrate the variable computed tomographic appearances of omental cakes.
The anatomy and embryology are discussed, as well as the importance of biopsy when the aetiology of omental cakes is uncertain.
The greater omentum plays a unique role in intraperitoneal pathology and the corresponding computed tomographic (CT) imaging of that pathology. As a predominantly fat-containing structure within the abdomen, its inherent contrast on CT makes inflammatory, infectious, and neoplastic processes more apparent. In time, these processes result in a diffuse thickening of the omentum, such that it changes from a barely discernible fatty band to a mass that can displace underlying bowel from the abdominal wall, i.e., the so-called “omental cake”. This classic radiological sign and its nuances stem from the early 1900s surgical literature .
Ovarian carcinoma is the most common prototype malignancy to produce omental cakes; however, numerous other malignancies may have a similar or forme fruste appearance. Moreover, several infections and other uncommon disease states also can produce omental cakes. We present various usual and unusual aetiologies and imaging characteristics of omental cakes, as well as the anatomy and embryology of the greater omentum. The role of percutaneous image-guided biopsy is discussed when the cause of omental cakes is uncertain.
While 100–150 cc of non-ionic iodinated intravenous contrast material (1.5-2 cc/s) is desirable to increase the intrinsic contrast of the images, it may not be necessary to diagnose the extent of an omental cake, unless knowledge of the extent is important to surgical planning. Frequently, however, intravenous contrast material is administered, mostly to evaluate coexisting liver or other solid organ disease. Oral contrast material is valuable to avoid confusing unopacified bowel loops with omental pathology and to define the extent of the omental findings .
The presence of associated intraabdominal and intrahepatic findings, such as hepatic metastases and lymphadenopathy, may be the only clues as to the origin of omental disease if the diagnosis is unknown; the appearance of the omental cake itself is non-specific with respect to the diagnosis . As there are many conditions that can produce an omental cake, the need for a specific diagnosis relies on percutaneous biopsy of the cake if the aetiology is unknown.
Ultrasound (US) and magnetic resonance imaging (MRI) also have been used to evaluate the greater omentum [8, 9]. US serves an alternative to CT in guiding biopsy of omental cakes . MRI demonstrates omental cakes and other peritoneal implants, but unless a gastrointestinal contrast agent is administered, there is inferior contrast resolution relative to CT . Thus, CT is the mainstay modality to image the greater omentum. Nevertheless, MRI may be utilized in patients with contraindications to CT (contrast sensitivity, pregnancy) or as an adjunct in patients with inconclusive CT findings. Delayed enhancement after gadolinium improves detection of peritoneal metastases . Furthermore, the use of diffusion-weighted MRI is emerging as a potential technique for omental and peritoneal metastases .
With regards to imaging findings, obvious careful search for the primary malignancy is important to determine the aetiology if the cause of the omental cake is unknown. Metastatic omental involvement occasionally may be heralded by abdominal pain secondary to bowel obstruction or intussusception in cases of gastrointestinal malignancies that metastasise to the small bowel.
Infectious diseases are rare causes of omental cakes. Typically, these diseases are the result of haematogenous, lymphatic, or direct spread of infectious organisms into the peritoneum.
Non-tuberculous mycobacterial infection, histoplasmosis, and omental paragonimiasis all have been reported to cause omental cakes [23, 24]. A unique feature of omental paragonimiasis is the multiple, irregularly shaped, conglomerate calcifications that sometimes occur .
Sclerosing omentitis and amyloidosis both may involve the greater omentum and contain scattered calcifications that mimic the appearance of metastatic ovarian cancer or treated peritoneal mesothelioma . Associated calcifications in the subcutaneous tissues, kidneys, and urethra may be additional clues of the presence of amyloidosis .
One study reported a sensitivity of 89.5%, specificity of 100%, and accuracy of 92% in the detection of malignancy in 25 percutaneous CT-guided large-needle core biopsies of omental lesions. Furthermore, they were able to obtain a specific diagnosis of the malignancy in 78.9% (15/19) of cases . In another study of 111 percutaneous image-guided peritoneal and omental biopsies, the overall diagnostic rate was 89%, with a sensitivity of 93% and specificity of 86% . Moreover, the authors concluded that a second malignancy was revealed in approximately 10% of patients with a known primary cancer (8/79), such as non-Hodgkin’s lymphoma .
The risk of serious complications is minimal with these relatively superficial omental biopsies. It should be noted, however, that although omental involvement can be both conspicuous and relatively straightforward to biopsy, early cases may be subtle and challenging both to visualize and to biopsy.
If there is any question of where the cake-bowel interface is, bowel opacification with oral contrast should be administered to avoid inadvertent needle puncture of the gastrointestinal tract. US also may be used in cases of unexplained ascites with a thickened omentum. One study showed that of 258 patients with nodules in the greater omentum, definitive diagnoses were achieved in 94.57% of cases by US-guided biopsy .
While ovarian carcinoma is the prototype omental cake, many malignancies from a wide spectrum of primary sites and organ systems can produce this appearance. Although malignancy is by far the most common aetiology of omental cakes, numerous benign causes exist as well. The non-specific CT appearances of omental cakes make the need for a pathological diagnosis paramount for proper treatment if the primary diagnosis is unknown. The typical omental cake, located superficially within the abdomen, is ideally suited to percutaneous CT or US-guided biopsy for primary diagnosis and staging.
- Wilson T (1913) Gelatinous glandular cysts of the ovary, and the so-called pseudomyxoma of the peritoneum. Proc R Soc Med 6 (Obstet Gynaecol Sect):9–42Google Scholar
- Miller Q, Kline AL (2008) Solid Omental Tumours. eMedicine.com http://emedicine.medscape.com/article/193622-overview. Image modified and reprinted with permission from eMedicine.com, 2010
- Sompayrac SW, Mindelzun RE, Silverman PM, Sze R (1997) The greater omentum. AJR Am J Roentgenol 168:683–687PubMedView ArticleGoogle Scholar
- Krist LFG, Kerremans M, Broekhuis-Fluitsma DM, Eestermans IL, Meyer S, Beelen RHJ (1998) Milky spots in the greater omentum are predominant sites of local tumour cell proliferation and accumulation in the peritoneal cavity. Cancer Immunol Immunother 47:205–212PubMedView ArticleGoogle Scholar
- Platell C, Cooper D, Papadimitriou JM, Hall JC (2000) The omentum. World J Gastroenterol 6:169–176PubMedGoogle Scholar
- Cooper C, Jeffrey RB, Silverman PM, Federle MP, Chun GH (1986) Computed tomography of omental pathology. J Comput Assist Tomogr 10:62–66PubMedView ArticleGoogle Scholar
- Healy JC, Reznek RH (1998) The peritoneum, mesenteries, and omenta: normal anatomy and pathological processes. Eur Radiol 8:886–900PubMedView ArticleGoogle Scholar
- Que Y, Tao C, Wang Y et al (2009) Nodules in the thickened greater omentum: a good indicator of lesions? J Ultrasound Med 28:745–748PubMedGoogle Scholar
- Chou CK, Liu GC, Su JH, Chen LT, Sheu RS, Jaw TS (1994) MRI demonstration of peritoneal implants. Abdom Imaging 19:95–101PubMedView ArticleGoogle Scholar
- Forstner R (2007) Radiological staging of ovarian cancer: imaging findings and contribution of CT and MRI. Eur Radiol 17:3223–3235PubMedView ArticleGoogle Scholar
- Whittaker CS, Coady A, Culver L, Rustin G, Padwick M, Padhani AR (2009) Diffusion-weighted MR imaging of female pelvic tumours: a pictorial review. Radiographics 29:759–774PubMedView ArticleGoogle Scholar
- Walkey MM, Friedman AC, Sohotra P, Radecki PD (1998) CT manifestations of peritoneal carcinomatosis. AJR Am J Roentgenol 150:1035–1041View ArticleGoogle Scholar
- Hamrick-Turner JE, Chiechi MV, Abbitt PL, Ros PR (1992) Neoplastic and inflammatory processes of the peritoneum, omentum, and mesentery: diagnosis with CT. Radiographics 12:1051–1068PubMedView ArticleGoogle Scholar
- Tartar VM, Heiken JP, McClennan BL (1991) Renal cell carcinoma presenting with diffuse peritoneal metastases: CT findings. J Comput Assist Tomogr 15:450–453PubMedView ArticleGoogle Scholar
- Kim YS, Cho OK, Song SY, Lee HS, Rhim HC, Koh BH (1998) Peritoneal lymphomatosis: CT findings. Abdom Imaging 23:87–90PubMedView ArticleGoogle Scholar
- Yoo E, Kim JH, Kim MJ et al (2007) Greater and lesser omenta: normal anatomy and pathologic processes. Radiographics 27:707–720PubMedView ArticleGoogle Scholar
- Pickhardt PJ, Bhalla S (2005) Primary neoplasms of peritoneal and sub-peritoneal origin: CT findings. Radiographics 25:983–995PubMedView ArticleGoogle Scholar
- Ha HK, Jung JI, Lee MS et al (1996) CT differentiation of tuberculous peritonitis and peritoneal carcinomatosis. AJR Am J Roentgenol 167:743–748PubMedView ArticleGoogle Scholar
- Hanson RD, Hunter TB (1985) Tuberculous peritonitis: CT appearance. AJR Am J Roentgenol 144:931–932PubMedView ArticleGoogle Scholar
- Ha HK, Lee HJ, Kim H et al (1993) Abdominal actinomycosis: CT findings in 10 patients. AJR Am J Roentgenol 161:791–794PubMedView ArticleGoogle Scholar
- Dooley DP, Reddy RK, Smith CE (1994) Coccidioidomycosis presenting as an omental mass. Clin Infect Dis 19:802–803PubMedView ArticleGoogle Scholar
- Eyer BA, Qayyum A, Westphalen AC, Yeh BM, Joe BN, Coakley FV (2004) Peritoneal coccidioidomycosis: a potential CT mimic of peritoneal malignancy. Abdom Imaging 29:505–506PubMedView ArticleGoogle Scholar
- Scott WW Jr, Fishman EK (1990) Extramedullary hematopoiesis mimicking the appearance of carcinomatosis or peritoneal mesothelioma: computed tomography demonstration. Gastrointest Radiol 15:82–83PubMedView ArticleGoogle Scholar
- Jeong WK, Kim Y, Kim YS et al (2002) Heterotopic paragonimiasis in the omentum. J Comput Assist Tomogr 26:1019–1021PubMedView ArticleGoogle Scholar
- Coumbaras M, Chopier J, Massiani MA, Antoine M, Boudghene F, Bazot M (2001) Diffuse mesenteric and omental infiltration by amyloidosis with omental calcification mimicking abdominal carcinomatosis. Clin Radiol 56:674–678PubMedView ArticleGoogle Scholar
- Pombo F, Rodriguez E, Martin R, Lago M (1997) CT-guided core-needle biopsy in omental pathology. Acta Radiol 38:978–981PubMedView ArticleGoogle Scholar
- Souza FF, Mortelé KJ, Cibas ES, Erturk SM, Silverman SG (2009) Predictive value of percutaneous imaging-guided biopsy of peritoneal and omental masses: results in 111 patients. AJR Am J Roentgenol 192:131–136PubMedView ArticleGoogle Scholar