Omental Disease
Omental disease refers to any abnormality affecting the omentum, the apron-like fold of fatty tissue that hangs from the stomach and drapes over the intestines. The omentum has a genuine biological role—it wraps around areas of inflammation to wall them off, and it carries a dense population of immune cells—which is precisely why it becomes involved in so many abdominal conditions. Findings range from benign and self-limiting, such as omental infarction and inflammatory changes near an adjacent problem, to serious, such as omental caking from peritoneal spread of cancer. Because the omentum lies deep within the abdomen and cannot be examined directly, these conditions are identified almost entirely on imaging, most often CT.
What is it?
The omentum is a fold of peritoneum containing fat, blood vessels, lymphatic channels, and a dense population of immune cells. The greater omentum hangs down from the greater curvature of the stomach like an apron, draping over the small intestine and colon; the lesser omentum is a smaller fold connecting the stomach and first part of the duodenum to the liver.
The omentum is not passive tissue. It migrates toward areas of inflammation and injury, wraps around them, and helps wall off infection and perforation—a function that earned it the traditional description as the abdominal policeman. It contains specialized aggregates of immune cells known as milky spots, which sample fluid within the peritoneal cavity and mount immune responses.
These same properties explain why the omentum becomes involved in so many abdominal diseases. Its position draped over the bowel means it lies adjacent to almost any inflammatory process. Its rich blood supply and immune activity make it responsive to inflammation. And its milky spots, which efficiently capture material circulating in peritoneal fluid, also efficiently capture free-floating tumor cells—which is why the omentum is the most common site of peritoneal metastatic spread.
Omental disease is a descriptive category rather than a single diagnosis, encompassing several distinct entities.
Reactive omental inflammation is the most common finding by far. When any adjacent structure becomes inflamed—an appendix, a diverticulum, a gallbladder, the pancreas, a segment of bowel in Crohn’s disease—the nearby omental fat becomes inflamed and appears hazy or stranded on CT. This is usually a secondary observation rather than the main finding, resolves as the primary condition is treated, and requires no separate management.
Omental infarction occurs when part of the omentum loses its blood supply and the tissue dies. It may be primary, occurring without an obvious cause, or secondary to torsion of the omentum on its own axis, adhesions from prior surgery, a hernia, or trauma. It occurs more often on the right side, likely reflecting the greater length and mobility of the right portion of the greater omentum, and is more common in patients with obesity and in those who have had prior abdominal surgery. There is a recognized pediatric peak.
The clinical importance of omental infarction lies in what it mimics. It presents with acute, often sharp, localized right-sided abdominal pain that closely resembles appendicitis or cholecystitis, but typically without fever, marked leukocytosis, or the systemic illness those conditions produce. Before CT was widely used, many patients underwent surgery for presumed appendicitis and the diagnosis was made in the operating room. Today it is usually diagnosed on imaging, which has an important consequence: recognizing it allows conservative management and avoids an unnecessary operation.
A closely related entity is epiploic appendagitis, in which one of the small fat-filled projections along the surface of the colon—the epiploic appendages—undergoes torsion or venous thrombosis. It produces similarly localized pain, is likewise benign and self-limiting, and is likewise identified on CT and managed without surgery. The two are often discussed together because both are benign causes of acute localized abdominal pain that historically led to unnecessary operations.
Omental metastatic disease is the most consequential category. Cancer cells shed into the peritoneal cavity are efficiently trapped by the omentum’s milky spots, where they establish deposits. The result ranges from a few small nodules to extensive, confluent, sheet-like infiltration that replaces the normal fat—an appearance radiologists describe as omental caking, and one that is highly suggestive of peritoneal carcinomatosis.
The cancers most often responsible are ovarian, gastric, colorectal, pancreatic, and appendiceal, along with primary peritoneal carcinoma and mesothelioma. Ovarian cancer deserves particular mention because omental involvement is so characteristic that omentectomy is a standard part of staging and cytoreductive surgery even when the omentum appears normal, since microscopic deposits are common. Pseudomyxoma peritonei, usually arising from a ruptured appendiceal mucinous neoplasm, produces a distinctive pattern of gelatinous mucinous material distributed across the peritoneum and omentum.
Omental caking is frequently accompanied by ascites—fluid accumulation in the abdominal cavity—and by peritoneal nodules elsewhere, and the combination substantially raises the likelihood of malignancy.
Infectious causes include tuberculous peritonitis, which is an important consideration worldwide and can closely mimic peritoneal carcinomatosis on imaging, producing omental thickening, ascites, and peritoneal nodularity. Features that may favor tuberculosis include smooth rather than nodular peritoneal thickening and high-density ascites, but the overlap is substantial and tissue diagnosis is often required. This distinction genuinely matters, since one condition is curable with antibiotics and the other is not.
Omental abscess can arise from a perforated appendix, diverticulitis, a perforated ulcer, or postoperative infection, often with the omentum having wrapped around the source.
Primary omental tumors are rare and include lipoma, leiomyosarcoma, liposarcoma, solitary fibrous tumor, and gastrointestinal stromal tumors extending from the stomach. Desmoid tumors can involve the omentum as well as the mesentery and abdominal wall.
Omental cysts, usually lymphatic malformations, are uncommon and behave similarly to mesenteric cysts.
Omental torsion without infarction, omental hernia—where omental fat protrudes through an abdominal wall defect and is the most common content of many hernias—and omental hematoma following trauma, surgery, or anticoagulation complete the picture.
Symptoms depend entirely on the cause and are often absent.
Omental infarction produces localized abdominal pain that comes on over hours to a day or two, is often sharp or aching, is worse with movement or coughing, and is typically right-sided. Patients are usually not systemically unwell, which is a useful clue.
Malignant omental disease is often insidious. Early symptoms are vague—bloating, early satiety, mild abdominal discomfort, reduced appetite—and easily attributed to other causes. This nonspecific presentation is one reason ovarian cancer is frequently diagnosed at an advanced stage. As disease progresses, increasing abdominal girth from ascites, unintentional weight loss, fatigue, a palpable mass, and bowel symptoms from tethering or obstruction develop.
Tuberculous peritonitis typically produces fever, night sweats, weight loss, abdominal distension, and abdominal discomfort developing over weeks to months.
Evaluation is imaging-led.
CT of the abdomen and pelvis with intravenous contrast is the primary test. Normal omentum appears as uniform fat. CT distinguishes focal fatty inflammatory change with a hyperattenuating rim, typical of omental infarction; discrete masses; scattered nodules; and confluent soft tissue infiltration replacing the fat, the pattern of omental caking. Critically, CT also surveys for a source—an ovarian mass, a gastric or colonic tumor, an appendiceal lesion, ascites, peritoneal nodularity, or liver metastases—which frequently establishes the context.
MRI offers superior soft tissue characterization, and diffusion-weighted sequences improve detection of small peritoneal deposits, making it useful in selected staging situations.
Ultrasound identifies omental thickening and ascites, is useful for guiding paracentesis and biopsy, and is often the first test when abdominal distension is the presenting problem.
PET-CT is used for staging and treatment response in many cancers, though it has limitations for small-volume peritoneal disease and for mucinous tumors, which may be less metabolically active.
Blood tests support rather than establish the diagnosis, and typically include a complete blood count, inflammatory markers, liver and kidney function, albumin, and tumor markers where relevant—CA-125 in suspected ovarian cancer, though it is not specific and rises in many benign conditions including inflammation, endometriosis, and liver disease.
Ascitic fluid analysis is often the first invasive step when ascites is present, providing cell count, protein and albumin levels, culture, and cytology. Cytology can confirm malignancy but a negative result does not exclude it, since sensitivity is limited.
Image-guided core needle biopsy of thickened omentum is a well-established, relatively safe route to a definitive tissue diagnosis and is often preferred over surgical biopsy. Where imaging cannot distinguish tuberculosis from carcinomatosis, or where cytology is negative but suspicion persists, laparoscopy with direct visualization and targeted biopsy provides the answer.
Important to Know
Management diverges sharply depending on which entity is present, and distinguishing benign self-limiting conditions from malignant infiltration is the central task. Care is typically coordinated by general surgeons and gastroenterologists in the acute setting, and by gynecologic, surgical, and medical oncology teams when malignancy is involved.
Omental infarction is managed conservatively in most cases. Treatment consists of analgesia, usually with NSAIDs where appropriate, and observation. Symptoms typically improve over one to two weeks, though imaging changes can persist for months and may be seen on later scans without indicating ongoing disease. The main value of correctly identifying it on CT is avoiding an operation the patient does not need. Laparoscopic resection of the infarcted segment is reserved for severe or persistent pain, failure to improve, diagnostic uncertainty, or the development of complications such as abscess formation. Epiploic appendagitis is managed the same way.
Reactive omental inflammation requires no treatment beyond addressing the adjacent condition responsible for it, and resolves alongside it.
Tuberculous peritonitis is treated with prolonged multi-drug antituberculous therapy under specialist supervision. The critical step is making the diagnosis in the first place, since the imaging appearance overlaps substantially with peritoneal carcinomatosis, and treating one as the other has serious consequences in both directions. Laparoscopic biopsy is frequently required and is diagnostically reliable.
Malignant omental disease is managed within the overall oncologic plan rather than as an isolated problem, and the approach depends on the primary cancer, its extent, and the patient’s condition.
In ovarian cancer, omentectomy is a standard component of staging and cytoreductive surgery, performed even when the omentum looks normal, because microscopic disease is common and its identification changes staging and treatment. Cytoreductive surgery aiming for complete removal of visible disease, combined with platinum-based chemotherapy, is the foundation of treatment, with the sequence of surgery and chemotherapy individualized.
For selected patients with peritoneal disease from appendiceal, colorectal, and some other primaries, cytoreductive surgery combined with heated intraperitoneal chemotherapy is offered at specialized centres. This is a major operation with meaningful morbidity, appropriate for carefully selected patients with disease confined to the peritoneum, and patient selection is as important as the technique itself. Pseudomyxoma peritonei is a particular indication where this approach has substantially changed outcomes.
Systemic chemotherapy, targeted therapy, and immunotherapy are used according to tumor type and molecular characteristics. Peritoneal disease can respond less predictably to systemic therapy than disease elsewhere, partly because drug penetration into the peritoneal cavity is limited, which is part of the rationale for intraperitoneal approaches.
Symptomatic ascites is managed with paracentesis for relief, and for recurrent accumulation an indwelling tunnelled peritoneal catheter allows drainage at home and can substantially improve quality of life. Diuretics are less effective for malignant ascites than for ascites from liver disease.
Supportive and palliative care has a meaningful role in advanced peritoneal disease, addressing pain, nausea, appetite, bowel obstruction, and ascites. Early involvement of palliative care alongside active treatment improves symptom control and quality of life and is not a substitute for cancer treatment.
Follow-up depends on the diagnosis. Omental infarction generally requires no imaging follow-up once the diagnosis is confident and symptoms resolve. Indeterminate omental thickening in a patient without a known cancer may be reassessed with short-interval imaging or proceed directly to biopsy depending on the level of concern. Malignant disease follows protocol-based oncologic surveillance.
Care is typically coordinated across surgery, gastroenterology, gynecology, oncology, infectious disease, and radiology depending on the cause. Imaging, laboratory, and clinical findings are interpreted alongside the patient’s symptoms, examination, cancer history, exposure history, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding that some omental findings are benign and self-limiting, that omental infarction resolves without surgery even though the pain is significant, that imaging changes can outlast symptoms, why a biopsy may be needed to distinguish infection from cancer, and which symptoms warrant prompt evaluation all contribute to appropriate care and reduce unnecessary anxiety.
Red flag symptoms include progressive abdominal distension or increasing abdominal girth; unintentional weight loss; persistent bloating, early satiety, or reduced appetite lasting more than a few weeks, particularly in women, where these are recognized early symptoms of ovarian cancer; a palpable abdominal mass; persistent or worsening abdominal pain; fever with night sweats; crampy pain with vomiting, distension, and inability to pass gas or stool, suggesting bowel obstruction; jaundice; new leg swelling; shortness of breath from a large volume of ascites; and any of these in a patient with a known cancer. These warrant prompt medical evaluation, as they may indicate peritoneal malignancy, infection, or bowel obstruction.