Role of magnetic resonance in bowel pathologies: Beyond inflammatory bowel disease

Table 1 Magnetic resonance imaging sequences, contrast requirements, key imaging findings, and main clinical indications for non-inflammatory bowel disease bowel pathologies

Condition	MRI sequences						IV contrast	Key findings	Main clinical indication
	T2/HASTE	T1	DWI	Post-Gd T1	MRE/enteric	MRA/flow
Celiac disease	√							Bowel dilatation; mural thickening; submucosal edema; jejunoileal fold pattern reversal; jejunization of ileum; lymphadenopathy	Not routine for diagnosis; problem-solving in nonspecific symptoms
Appendicitis	√		√					Dilated, fluid-filled appendix; wall thickening/T2 hyperintensity due to edema; periappendiceal inflammation; restricted diffusion	Equivocal US, particularly children or pregnancy
Diverticulitis	√	√	√					Diverticula; wall thickening; pericolonic fat stranding; phlegmon/abscess; perforation or fistula	Alternative in selected patients with suspected diverticulitis
Radiation enteritis	√			√	√		√	Wall thickening; mural enhancement; luminal narrowing; strictures; chronic obstruction	Post-radiotherapy abdominal symptoms or suspected chronic radiation enteropathy
Radiation colitis/proctitis	√			√			√	Wall thickening/T2 hyperintensity due to edema; mural enhancement; luminal narrowing; fibrosis/strictures; presacral or mesorectal fascial change	Suspected large-bowel radiation injury after pelvic irradiation
Fistulas	√	√		√			√	Fistulous tract; focal wall thickening; debris/air; fat stranding; abscess or fluid collections; pelvic-organ involvement	Define tract anatomy and associated complications
Bowel neoplasms	√	√		√	√		√	Annular/constricting lesion; polypoid intraluminal mass; exophytic mass; segmental thickening; obstruction, nodes, hemorrhage, necrosis	Detect, characterize, and stage bowel lesions and complications
Pouchitis	√	√		√			√	Pouch wall thickening > 2 mm; abnormal mural enhancement; peripouch fat infiltration; fluid collection or abscess; sinus tract or fistula	Evaluate mural inflammation and extraluminal complications after ileal pouch-anal anastomosis
Bowel obstruction	√	√			√			Dilated proximal loops; transition point; adhesions; collapsed distal bowel; visible obstructing cause when present	Radiation-sparing alternative in children, pregnancy, or high cumulative exposure risk
Intussusception	√				√			Bowel-within-bowel configuration; hyperintense intraluminal fluid; low/intermediate wall signal; perienteric edema; lead point	Problem-solving or incidental detection; assess obstruction or a lead point
Mesenteric ischemia	√			√		√	√	Mural thickening/edema; reduced or absent enhancement; mesenteric edema/ascites; vascular filling defect; pneumatosis or portomesenteric gas in severe cases	Best established for chronic mesenteric ischemia; MRA and flow MRI assess stenosis and postprandial flow

√: May be used for evaluation; Blank: Not routinely used or required for that indication; DWI: Diffusion-weighted imaging; Gd: Gadolinium; HASTE: Half-Fourier acquisition single-shot turbo spin-echo; IV: Intravenous; MRA: Magnetic resonance angiography; MRE: Magnetic resonance enterography; MRI: Magnetic resonance imaging; US: Ultrasound.

Table 2 Comparative magnetic resonance imaging features of common benign and primary malignant small bowel neoplasms

Category	Lesion	MRI features
Benign	Adenoma	Small, well-defined, intraluminal soft-tissue lesion, usually < 2 cm, with moderate enhancement
	Lipoma	Signal intensity identical to fat, hyperintense on T1 and T2, with signal loss on fat-suppressed sequences
	Hemangioma	T2 hyperintense and enhancing; cavernous subtypes may appear polypoid or submucosal
	Leiomyoma	Well-circumscribed, submucosal smooth-muscle tumor; homogeneous focal mass with uniform enhancement greater than adjacent bowel
Malignant	Adenocarcinoma	Annular or constricting lesion narrowing the lumen, often with irregular wall thickening and obstruction
	Neuroendocrine tumor	Hyperenhancing primary lesion; often isointense to adjacent musculature on T1 and isointense to mildly hyperintense on T2; may be associated with a mesenteric mass or desmoplastic reaction
	GIST	Exophytic, heterogeneously enhancing mass that may demonstrate necrosis or hemorrhage
	Lymphoma	Variable appearance, including long-segment involvement and aneurysmal dilatation; splenomegaly and lymphadenopathy may support the diagnosis

MRI: Magnetic resonance imaging; GIST: Gastrointestinal stromal tumor.