Abdo: Small Bowel Obstruction

Types of small bowel obstruction

• Adhesional IO is most common post surgery
• Mechanical
• Inflammatory
• Malignant
• Closed-Loop Obstruction

MECHANICAL: Cases 1 - 3

• Gallstone ileus
• Hernias: obturator, femoral, ventral

INFLAMMATORY: Cases 4 - 10

• ACE-inhibitor related angioedema
• Eosinophilic gastroenteritis
• Crohn's disease with fistulation
• Vasculitis - SLE most common, consider especially if there is also GU involvement
• Endometriosis - consider in young female with recurrent obstruction

Mimic of Inflammatory = Ischaemic - SMV thrombosis possible. SMA embolism possible

MALIGNANT: Cases 11 - 16

• Lymphoma - usually doesn't cause obstruction, but still can. Consider especially if other features like nodes, stomach involvement. Can help obviate surgical management. Usually treated with chemo
• Small bowel AdenoCA - look for cluster of regional lymph nodes especially helpful
• Carcinoid - Enhancing mesenteric implant with surrounding desmoplastic reaction. Arterial phase imaging is important to complete staging and evaluate underlying liver lesions
• Pseudomyxoma peritonei from mucinous tumour of the appendix. In this case, mucinous implant invades the SB wall
• Splenic flexure bulky tumour causing obstruction. Case 15 is bulky, Case 16 is more stricturing and classic apple core configuration with shouldering - Serous AdenoCA.

CLOSED LOOP: Cases 17 - 20

Spectrum of involvement

• Adhesive disease
• Internal hernia
• Volvulus

Both adhesion and internal hernias can become the lead point for volvulus.
Adhesive bands can also cause an internal hernia type defect resulting in obstruction

Adhesions cannot be seen, only can guess based on secondary features

Signs:

• Beak sign
• Asymmetric oedema
• Clustered loops, radial vessels
• Haemorrhage or hypoenhancement from ischaemia / congestion
• Dilated U or C loop
• Swirling, narrowed vessels