Editing Small bowel obstruction (section)

== Imaging ==

=== '''AXR''' - sensitivity 66% ===

* Best role is for follow-up of patients with chronic obstruction being managed non-operatively
* Supine/prone signs:
** Dilated gas or fluid-filled small bowel >3cm
** Dilated stomach
** Small bowel dilated out of proportion to colon
** Stretch sign
** Absence of rectal gas
** Gasless abdomen
** Pseudotumour sign
* Upright/left lateral decubitus signs:
** Multiple air fluid levels
** Air fluid levels longer than 2.5cm
** Air fluid levels in same loop of small bowel of unequal lengths
** String of beads sign
*

=== '''CT''' - SBO is a CLINICAL diagnosis, CT is to find the cause and evaluate for strangulation ===

* IV contrast only (PO contrast takes time, interferes with view of the colonic wall, and may be poorly tolerated)
* Small bowel faeces sign - immediately proximal to transition point, caused by stasis
* Transition point DOES NOT predict need for operation (although controversial)
* Free fluid commonly present, however large volume ascites is concerning
* Indications for immediate intervention - ischaemia, closed loop obstruction, perforation
* Complete SBO - significantly distended bowel, failure to pass stool or flatus, lack of air in distal small bowel or colorectum
** Virtually always leads to operation
* Closed-loop obstruction - concerning for ischaemia due to increased intra-luminal pressures - evaluate for other signs of ischaemia
* '''CT findings associated with ischaemia:'''
** Bowel wall - decreased, delayed enhancement; mural thickening >3mm; pneumatosis intestinalis
** Mesentery - venous congestion and engorgement; mesenteric oedema; mesenteric haemorrhage
** Other - portal or mesenteric venous gas; free fluid or ascites
** Note that these are all late signs compared to the clinical findings of strangulation above

=== '''Barium enteroclysis''' ===

* Continuous fluoroscopy or radiographs at frequent intervals
* Theoretically allows details imaging of the entire small bowel
* Has been suggested for patients with low-grade recurrent SBO

=== '''MRI''' ===

* No better than CT

=== '''USS''' ===

* Has been described for use in pregnant patients