Small bowel lipoma is a benign mesenchymal tumor composed of mature adipose tissue in a submucosal location. It is one of the most common benign tumors of the small intestine, accounting for approximately 20-25% of all gastrointestinal lipomas. It most commonly occurs in the ileum. Most are asymptomatic and discovered incidentally; large lipomas (>2 cm) can cause intussusception, obstruction, or GI bleeding. Diagnosis is usually definitive with homogeneous fat density (-50 to -100 HU) on CT. T1 hyperintensity and signal loss on fat suppression on MRI confirm the diagnosis. Lipomas do not undergo malignant transformation; symptomatic ones are treated with surgical or endoscopic resection.
Age Range
35-75
Peak Age
55
Gender
Equal
Prevalence
Uncommon
Small bowel lipomas originate from hamartomatous accumulation of mature adipocytes in the submucosal layer. They are surrounded by a thin fibrous capsule and show slow growth in the submucosa. The tumor forms an intraluminal mass by polypoid protrusion into the small bowel lumen. As it grows, erosion and ulceration of the overlying mucosa may develop — causing GI bleeding. Due to the soft and compressible nature of the lipoma, it may change shape during bowel peristalsis ('squeeze sign'). Large lipomas can cause intussusception as a lead point — peristaltic waves push the lipoma distally, dragging the adjacent segment along. Fat density (-50 to -100 HU) on CT is pathognomonic because mature adipose tissue contains triglycerides, and the low molecular weight and low electron density of triglycerides weakly attenuate X-rays. On MRI, the short T1 relaxation time of fat is reflected as T1 hyperintensity, and signal loss with frequency-selective fat suppression confirms fat content.
Well-defined submucosal mass at homogeneous fat density (-50 to -100 HU) on CT — pathognomonic for lipoma. Density value is precisely determined by ROI measurement. As no other small bowel lesion has fat density, this finding is diagnostic.
Well-defined, round/oval submucosal mass at homogeneous fat density (-50 to -100 HU) on CT. The lesion shows polypoid protrusion into the bowel lumen. Thin capsule is rarely visible. Homogeneous fat density is pathognomonic and no other lesion shows these density values. Lesion size is generally 1-5 cm.
Report Sentence
Well-defined submucosal mass at homogeneous fat density (-... HU) in the small bowel is consistent with lipoma.
Homogeneously hyperintense submucosal lesion on T1-weighted MRI — isointense to subcutaneous fat. Signal intensity equals subcutaneous fat, confirming fat content. Thin capsule may be visible as a thin hypointense line on T1. The lesion is smooth-marginated and homogeneous.
Report Sentence
Submucosal lesion hyperintense on T1 isointense to subcutaneous fat in the small bowel is consistent with lipoma.
Homogeneous signal loss in the lesion on fat suppression sequences (STIR or frequency-selective fat-sat) — definitive confirmation of fat content. The lesion that is hyperintense on T1 becomes completely dark with fat suppression. This finding confirms the diagnosis of lipoma and distinguishes from other T1-hyperintense lesions such as melanoma metastasis and hemorrhagic lesions.
Report Sentence
Homogeneous signal loss on fat suppression in the T1-hyperintense submucosal lesion in the small bowel confirms the diagnosis of lipoma.
No enhancement in the lesion on contrast-enhanced CT — density difference <10 HU between pre and post-contrast. Smooth, well-defined margins. Surrounding bowel wall is normal. In large lesions, a thin enhancing line over the lesion (preserved mucosa) may be seen.
Report Sentence
Non-enhancing, smooth-marginated submucosal lesion at fat density in the small bowel is consistent with lipoma.
Hyperechoic, homogeneous, well-defined submucosal mass on B-mode US. The lesion is markedly hyperechoic compared to surrounding bowel wall. No posterior acoustic shadowing. May show shape change with compression ('squeeze sign'). No vascularity on color Doppler.
Report Sentence
Hyperechoic, homogeneous, avascular submucosal lesion in the small bowel is consistent with lipoma.
Intermediate to high signal intensity on T2-weighted MRI — isointense to subcutaneous fat. T2 signal is lower than CSF but higher than muscle. Complete signal loss on STIR sequence confirms the diagnosis.
Report Sentence
Submucosal lesion isointense to subcutaneous fat on T2 in the small bowel with complete signal loss on STIR confirms the diagnosis of lipoma.
Criteria
Well-encapsulated submucosal lesion composed of homogeneous mature adipose tissue
Distinct Features
Homogeneous fat density, no enhancement, usually asymptomatic, no malignant transformation risk
Criteria
Lipoma larger than 4 cm — high risk of intussusception and obstruction
Distinct Features
High probability of being symptomatic, intussusception lead point, mucosal erosion and GI bleeding, surgical indication
Criteria
Multiple lipomas in the small bowel — usually distributed in jejunum and ileum
Distinct Features
Increased intussusception risk, each at homogeneous fat density, multiple fat-density polypoid lesions on CT
Distinguishing Feature
GIST is a heterogeneously enhancing mass at soft tissue density (30-60 HU); does not show fat density. GIST is usually larger, shows exophytic growth, and may contain central necrosis.
Distinguishing Feature
Hemangioma shows intense enhancement and T2 hyperintensity; does not show fat density. May have phleboliths. Does not show signal loss on fat suppression.
Distinguishing Feature
Carcinoid is a hypervascular solid mass, does not show fat density. Mesenteric retraction and calcified mesenteric mass (desmoplasia) are characteristic.
Distinguishing Feature
Lymphoma shows homogeneous wall thickening or mass at soft tissue density; no fat density. Aneurysmal dilatation and sandwich sign may accompany.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
12-monthSmall bowel lipomas are benign lesions and do not undergo malignant transformation. Asymptomatic small lipomas (<2 cm) do not require treatment. Symptomatic lipomas (bleeding, obstruction, intussusception) are treated with surgical resection or endoscopic polypectomy. Homogeneous fat density on CT is diagnostic and biopsy is not needed.
Small bowel lipoma is benign and requires no follow-up or treatment when typical imaging features are present. Large lipomas may cause intussusception or obstruction requiring surgery.