The majority of lipomas are asymptomatic and found incidentally. As they can be pedunculated (see below) they occasionally present as the leading point of an intussusception. When large they may develop mucosal ulceration and present with iron deficiency anaemia or positive faecal occult blood testing . Acute heavy bleeding is uncommon.
Gastrointestinal lipomas, like lipomas elsewhere, are composed of mature adipocytes with an enveloping fibrous capsule
The vast majority (90-95%) are submucosal, with only a small number subserosal, and can be sessile or pedunculated .
Fluoroscopy: Barium studies
Lipomas are usually submucosal or occasionally pedunculated. They usually have a very smooth surface, unless mucosal ulceration is present.
CT / MRI
On both CT and MRI lipomas are usually easy to diagnose on account of their density (-80 to -120 HU) / intensity following that of fat on all sequences. Lipomas are usually entirely of fat density without solid components. If a solid non-fat component is seen then the possibility of the mass representing a liposarcoma should be entertained, although these are exceedingly rare . Overlying ulceration may result in some non-fat density / intensity stranding near the mucosal surface.
Treatment and prognosis
As these are benign slow growing lesions, and usually little doubt exists in the diagnosis, no treatment is required. If symptomatic then local excision is sufficient .
Lipomas are common, nonepithelial, benign, fatty tumors that can be found throughout the gastrointestinal tract, although they are most frequently seen in the colon. Approximately 90% of colonic lipomas are located in the submucosa; the remainder of these tumors are subserosal or intramucosal in origin. The reported incidence of colonic lipomas ranges from 0.2% to 4.4%. Lipomas of the large intestine are most commonly seen (in order of decreasing frequency) in the cecum, ascending colon, and sigmoid colon. Of note, more than 70% of these tumors are located in the right hemicolon. Colonic lipomas are more common in women than in men, with a predilection for the right colon in women and the left colon in men. The mean age of patients with colonic lipomas falls within the sixth decade. Colonic lipomas vary in size from several millimeters to 30 cm. Lipomas are usually well-delineated, soft, ovoid, yellowish masses. These tumors can be found by themselves or in groups, and they can be sessile or pedunculated Several cases of primary colonic liposarcomas have been reported in the literature, whereas other lipomas are mostly seen in conjunction with retro-peritoneal liposarcomas.
Colonic lipomas are generally asymptomatic and are found incidentally during a colonoscopy or surgery for other conditions. Symptoms correlate with the size of the lipoma; lipomas larger than 4 cm in size become symptomatic in 75% of patients. Lipomas often present with vague symptoms—such as abdominal pain and/or alterations in bowel habits—and rarely manifest as gastrointestinal bleeding, perforation, or obstruction. Giant lipomas (>4 cm) are the most common benign tumors in the colon that cause intussusception, although no specific incidence data have been documented. Even patients with large lipomas may have nonspecific or intermittent symptoms, which causes delay and difficulty in making the diagnosis. Intussusceptions are usually limited to segment of the colon—either ascending, transverse, or descending—but can extend to more than segment in some cases. Large lipomas may develop superficial ulceration and bleeding and may present with a combination of symptoms. Due to similarities in age and symptoms, colonic lipomas may mimic malignancy in presentation.
Gould and associates present a case of a colonic lipoma that meets the typical age, gender, and symptoms of this tumor but not the typical location or appearance; the patient had a large mass with atypical characteristics (ulceration) on gross examination, an atypical site, and development of intussusception.
Characteristic radiographic findings—detected via barium enema, computed tomography scan, or magnetic resonance imaging—and endoscopic findings—as described in the case study by Gould and coworkers—are useful in the diagnosis of a typical lipoma.However, the presence of intussception, irregular margins, lymph node enlargement, or thickening of the bowel wall—in association with a mass seen on imaging—raises suspicion for a malignant etiology. Similarly, colonoscopic findings— such as the presence of a firm or fungating mass, ulceration, or necrosis—are concerning for malignancy. Even experienced endoscopists may mistake a large colonic lipoma for a large polyp or colorectal cancer .
Colonic lipomas that cause symptoms or pose a diagnostic dilemma, as in the case study reported by Gould and associates, should undergo evaluation with an eye toward resection.10 Both surgical and endoscopic techniques have been widely used in the management of colonic lipomas, although no consensus is available regarding which procedure takes precedence. Surgical therapy is more commonly used for large lesions, as in the case study by Gould and coworkers.10 As lipomas show no significant malignant degeneration, small (<2 cm) asymptomatic lipomas can be observed when unequivocally proven by biopsy or imaging to have typical findings on EUS. In the past, endoscopic resection has been thought to be associated with a higher risk of perforation and bleeding, but multiple case reports have recently demonstrated good success rates and acceptable complication rates. Because the vasculature, size, and extension of the muscularis propria or serosa into the pedicle determines the outcome of endoscopic resection, a detailed examination of the base of the lipoma during endoscopy guides decision-making regarding surgical versus endoscopic resection EUS can be valuable for obtaining such details and minimizing complications of endoscopic removal. Pedunculated lipomas up to 11 cm in size have been safely removed endoscopically via newer techniques, such as snare electrosurgery or endoloop ligation.
Surgical resection is the treatment of choice when giant lipomas are complicated by intussusception or bowel obstruction. Surgical resection should also be the first-line management for lipomas that are sessile, have limited peduncles, or have extension of serosa/muscularis propria into the pedicle. When attempted endoscopic resection fails, large lipomas should be removed surgically. Various surgical techniques—such as hemicolectomy, segmental resection of the involved colon, or local excision—have all been used with success. However, local excision should be considered whenever feasible in order to limit morbidity.
The patient in the case study by Gould and colleagues was appropriately managed by surgical resection of the colonic segment containing the mass and intussus-ception. Based upon histopathology, the resected mass was later found to be a lipoma.
Spontaneous expulsion of lipomas secondary to autoamputation has been reported in the literature. Both surgical and endoscopic resection of colonic lipomas show good outcomes with no known recurrence after complete removal.18 The key take-home message should be that while most colonic lipomas are small and asymptomatic, larger lesions may mimic polyps or tumors, cause a variety of symptoms, and warrant surgery.
Bauer reported the first case of a colonic lipoma in 1757.1 Lipomas are benign, nonepithelial tumors that can be found anywhere in the gastrointestinal tract, but most are located in the colon.1 As a benign lesion, they rank second in frequency only to benign adenomatous polyps. Pathologically, they are spherical deposits of adipose tissue in the bowel wall, in a submucosal, pedunculated, sessile, or very rarely annular position.2–4 When on a stalk, this psuedopedicle is felt to develop from continuous extrusion of the lipoma due to the peristalsis of the colon.3 Ninety percent of colonic lipomas lie in the submucosa; the remainder are subserosal.5 They have been noted to occur 1.5 to 2.0 times more frequently in women, and most patients are in their fifth or sixth decade of life.6 They are more frequently located on the right side, particularly in the cecum.1,7 They are multiple in up to 26% of cases.8 A review of over 10 000 colonoscopies found 16 lipomas with a distribution of 63% in the right colon and 37% in the left colon. Although they are the second most common benign colonic tumor, they are rare lesions with an incidence reported between 0.2 to 2.6%.A review of several major autopsy and clinical reports reveals an incidence of 0.26%.
They are often found incidentally during colonoscopy or radiologic imaging. On contrast enema, lipomas appear circular, ovoid, well-demarcated, and smooth. A barium enema will show a radiolucent mass, and they may fluctuate in size and shape during the study. Radiolucency and the “squeeze sign” (change in size and shape during peristalsis) have been considered pathognomonic of colonic lipomas. On CT, the lipoma has a uniform appearance and density with absorption densities of -80 to -120 Hounsfield units to confirm the fatty composition. Meglumine diatrizoate (Gastrografin) should be administered as a dilute enema to maximize the imaging of the lipoma. A radiologic diagnosis can be made definitively in less than 20% of patients.
Endoscopy, which locates a mass consistent with a lipoma, may reveal the “cushion sign” whereby a sponge-like impression is made as biopsy forceps are passed in the lesion and it then regains its original shape as they are withdrawn.11 Also the “naked fat sign” occurs after a biopsy is taken from the mucosa revealing fat protruding from the site. The specimen is also noted to float if extracted and placed in formalin. The mucosa will “tent” over the mass if it is grasped with forceps as it detaches from the lipomatous mass below it. Any of these findings are highly indicative of a benign lipoma.
Small colonic lipomas are rarely symptomatic, but when >2 cm, they can result in persistent or intermittent abdominal pain, bloating, changes in bowel habits, gastrointestinal bleeding, bowel obstruction, or intussusception. Among symptomatic patients, abdominal pain (23%) and rectal bleeding (20%) are the most common complaints with anemia, weight loss, nausea, vomiting, and abdominal distention being less commonly reported.1 Roughly 25% of all colonic lipomas are found to be symptomatic. Clinical proficiency helps distinguish this entity from other more common disease processes, such as chronic cholecystitis, diverticulosis, diverticulitis, colonic polyps, or malignancy, as its symptomatology can overlap significantly0 Imaging with a contrast-enhanced abdominal CT scan can help delineate a benign colonic lipoma from other disease processes. Any deviation from the CT scan characteristics as described in this patient may indicate the presence of a malignancy. Colonoscopy is mandatory to locate, visualize, and biopsy the lesion. Endoscopic or surgical removal is indicated for symptomatic colonic lipomas or when malignancy is suspected or known. Although large colonic lipomas have been removed endoscopically, a greater risk of colon perforation exists when they are broad-based, intramural, or when they are >2 cm. Endoscopic ultrasound and injection of the base with epinephrine or saline is reported to help decrease this complication. Specifically, endoscopic ultrasonography can demonstrate whether the lipoma extends into the muscularis propria, a risk factor for perforation that should preclude endoscopic removal. Some lesions that are concealed behind mucosal folds or colonic flexures cannot be removed colonoscopically, and this worsens the risk of perforation after endoscopic removal. Recent literature to support the use of endoscopic ultrasound during excision has shown that lipomas can be removed safely by endoscopy if they are >2 cm; however, we recommend laparoscopic excision until this technique is more widely practiced.
Surgical removal usually involves limited resection or colotomy with lipomectomy.20 Multiple operative techniques ranging from laparotomy with enucleation, colotomy, and segmental colonic resection have been described. Laparoscopic colon resection in the face of a known lipoma results in improved cosmesis, decreased length of stay, shorter disability, decreased adhesion formation, less postoperative pain, and faster return of bowel function. Segmental resection or colostomy with resection and closure are both feasible where indicated.
We have adopted a clinical algorithm whereby symptomatology determines whether the patient will undergo radiologic or endoscopic evaluation. Radiologic identification leads to colonoscopic evaluation, and small lipomas <2 cm are removed endoscopically. If the mass is >2 cm or suspicious for malignancy, laparoscopic excision is performed with colotomy and closure or partial colectomy when indicated. For tumors of the rectosigmoid, transanal resection is possible.
Gastrointestinal tract lipomas | Radiology Reference Article | Radiopaedia.org
Large Colonic Lipomas
Laparoscopic Management of Colonic Lipomas: A Case Report and Review of the Literature
Last edited by Medical Photos; 09-14-2015 at 05:41 PM.
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