New Endoscopic Approaches to Removing Colonic Lipomas

Colonic lipoma is one of several submucosal tumors (including other types of lipoma, leiomyoma, lymphangioma, neurofibroma, carcinoid tumor, sarcoma, and lymphoma) that are rarely encountered in clinical practice.¹ Unlike other submucosal tumors, colonic lipomas can be easily diagnosed because of their characteristic appearance. Fat is yellow, smooth, soft, and pliable; thus, a smooth, yellow-colored submucosal lesion with a “pillow sign” (a surface indentation observed upon pushing the mass with closed biopsy forceps during colonoscopy) is quite characteristic of a colonic lipoma. Performing a single biopsy of the lesion is useless, as the biopsy reaches only the surface mucosa. Repeated biopsies at the same spot may reveal underlying fat, which is known as the “naked fat sign.”² Colonic lipoma can be seen as an uniformly hyperechoic mass arising from the colonic wall on endoscopic ultrasonography^3,4 or as a pliable, spherical lesion with broad pedicles on barium enema.⁵ Confirmation of the diagnosis can be made by computed tomography scan or magnetic resonance imaging.^6,7

The majority of colonic lipomas are asymptomatic and found incidentally during colonoscopy. Lipomas larger than 2 cm may cause symptoms such as abdominal pain, bowel changes, and rectal bleeding; mimic cancer; or present as a life-threatening emergency with massive hemorrhage, obstruction, perforation, intussusception, or prolapse.^8–17

Management of colonic lipomas depends upon their size and clinical presentation. Although there is no need to remove small (<2 cm) asymptomatic lipomas, formal guidelines do not currently exist to aid clinicians regarding the need or frequency of follow-up. Surgical removal is indicated in patients with colonic lipomas who present with complications such as obstruction, intussusception, perforation, or massive hemorrhage.^18,19 Due to the fear of complications (such as bleeding or perforation after endoscopic snare resection), patients with asymptomatic colonic lipomas larger than 2 cm are referred for elective surgery.²⁰ Recent advances in endoscopic techniques allow endoscopic removal to be considered as an alternative to surgical removal of large colonic lipomas.^3,21–28

However, before endoscopic removal of large colonic lipomas, the following two questions should be considered:

1. Is the lesion sessile or pedunculated? Large ses sile lesions may be difficult to ensnare, as the snare tends to slip easily during closure. In addition, the low water content of fat makes it a poor conductor of electrosurgical current. The prolonged cautery required for cutting may lead to the transmission of thermal damage to underlying tissue and result in a perforation.²⁰ Surgery should be considered in these cases. However, endoscopic snare resection could be considered if the superficial nature of the lipoma and adequate separation of the lesion from the muscularis propria after saline injection can be confirmed by endosonography.^3,28

2. Is the pedicle free from muscle or serosa? Submucosal lipomas, as they enlarge, drag a pedicle that is free from muscle or serosa, and are safe to resect. Lipomas arising from the muscular or serosal layers lead to invagination of these layers into the pedicle as they enlarge into the lumen and are at risk for perforation during snare resection.^20,29 Although endoscopic ultrasound may assist in defining the layer structure of the stalk, experi ence with endoscopic ultrasound is limited in this area, and it is not easy to pass and interrogate the stalk with endosonography. Instead, the clinician could consider the use of probe sonography, as the ultrasound probe catheter can be easily inserted through the colonoscope.^3,28 Surgery should be considered in these cases as well, if the clinician cannot clearly define the nature of the pedicle (ie, whether there is muscle or serosa in the stalk).

Accordingly, one may wonder precisely what the role of the endoscopist is in the removal of colonic lipomas. Given the preceding discussion, it is crucial to be prepared to select the right lesion for removal and to prevent or treat colonic perforation by endoscopy. With expertise in the use of novel devices to approximate tissue—such as a nylon loop, clip device, or suturing device—the clinician could consider endoscopic removal of large pedunculated lipomas. When using these devices to remove colonic lipomas, it is recommended that endoscopists keep the following in mind:

1. In the case of a long pedicle, the endoloop should be far away from the snare. A little distance should be left on the pedicle in between the nylon (endo) loop and the electrical snare, so that enough stalk remains after snare resection for the endoloop to continue its grasp; ensnaring just above and close to the endoloop results in slippage of the endoloop from the retracting stalk, with the lost benefit of loop ligation to prevent bleeding or delayed perforation.^23,26

2. If there is not enough stalk on a short stalk to place the snare above the nylon loop, instead of electrosurgical snare resection, the polyp can be allowed to undergo slow ischemic necrosis after endoloop ligation. This process may require repeat application of an additional endoloop after a few weeks for complete resection of the lipoma.²⁵

Unlike snare use, loop ligation may be challenging for inexperienced endoscopists; hence, it is crucial to undergo training in the implementation of a loop to safely and effectively use it in clinical practice. The American Society of Gastrointestinal Endoscopy offers training courses in the use of novel devices to help the practicing gastroenterologist learn new tools and tricks of the trade.

As experience with the endoscopic management of large colonic lipomas is limited to only a few cases and it is difficult to recruit large numbers of patients to report adequate experience with this technique, case reports such as this one from El-Dika and colleagues help clinicians gather adequate data to pursue endoscopic resection of colonic lipomas with confidence.²³ Such reports, whether positive or negative, should be encouraged when addressing any challenge not routinely seen in clinical practice.