Omental caking | Radiology Signs

Answer:

Omental caking represents diffuse infiltration and thickening of the omentum by soft-tissue density material, most commonly resulting from advanced intraperitoneal malignancy. The primary causes include metastatic spread from ovarian carcinoma (most frequent malignant etiology), gastric carcinoma, colonic carcinoma, and pancreatic carcinoma, with less common causes including endometrial carcinoma, bladder cancer, renal cell carcinoma, hepato-biliary malignancies, melanoma, lung cancer, and breast cancer. Metastatic involvement reaches the omentum through four routes: direct extension, intraperitoneal seeding, hematogenous spread, and lymphatic spread. Non-malignant causes include tuberculous peritonitis, bacterial and fungal infections, and lymphomas such as Non-Hodgkin’s lymphoma or MALT lymphoma. Associated clinical presentations vary widely depending on etiology but commonly include ascites, abdominal pain, weight loss, gastric distention, and fever when infectious etiologies are present.

Why is it called so?

The term omental cake derives from the characteristic appearance of the affected omentum, which transforms from its normal barely discernible fatty band into a thickened, mass-like structure that resembles the texture and appearance of a cake. This descriptive terminology has been established in surgical and radiological literature since the early 1900s and reflects the visual analogy between the pathologically altered omentum and a solidified cake-like mass.

Pathophysiology

The greater omentum, an extension of visceral peritoneum containing predominantly fatty tissue with fine vasculature, normally appears as bands of fatty tissue on imaging. The omentum contains specialized lymphoid tissue called milky spots distributed throughout its structure in highest concentration in the greater omentum. These milky spots function as part of the omental role as the abdominal policeman, involved in pathogen clearance from the peritoneum, but simultaneously serve as potential traps for intraperitoneal metastases, particularly through intraperitoneal seeding. When disease processes such as malignancy, infection, or inflammation affect the omentum, localized or diffuse infiltration of omental fat occurs by soft-tissue density material. This infiltrative process progressively replaces normal fatty tissue with solid material, resulting in thickening of the omentum. The earliest manifestations appear as smudged or permeated appearance of omental fat on CT, which progresses to more extensive nodular and heterogeneous thickening as disease advances. The thickened omentum may displace underlying bowel from the abdominal wall and often floats within ascitic fluid, creating the characteristic cake-like appearance on cross-sectional imaging.