Editing Small bowel obstruction (section)

== '''Aetiology of jejunal and ileal SBO''' ==
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|'''Extra-luminal'''
|Adhesions (65%)
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** Mostly from surgery, but can also be caused by peritonitis, diverticulitis, radiation enteritis, or PID
** Can be congenital
** Likely occurs more for pelvic procedures due to higher mobility of bowel
** Caused by fibrotic bands which are the end result of inflammation at sites of previous injury/surgery
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|Internal hernia
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|Midgut (small bowel) volvulus
|A huge load of high-fibre, indigestible food which arrives suddenly in an empty bowel, creating rotational-kinking forces.

Uncommon in the developed world.

Bowel found to be twisted around an unusually long mesentery, containing litres of clay-like undigested food.

Can occur in combination with sigmoid volvulus to form the ileosigmoid knot.

Urgent operation.
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|External hernia (10%)
|Typically inguinal or ventral hernia
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|Neoplastic
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** Carcinomatosis
** Extra-intestinal neoplasm
** Malignancy accounts for about 20% overall - mostly peritoneal carcinomatosis
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|Intra-abdominal abscess
|Commonly ruptured appendix, diverticulitis, or dehiscence of an anastomosis
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|'''Intra-mural'''
|Primary tumours (carcinoid, GIST, adenocarcinoma)
|Rare
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|Metastatic tumours (colon, ovarian, gastric, pancreatic, melanoma)
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|Malrotation
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|Duplications, cysts
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|IBD (5%)

* Acute inflammation and oedema
* Chronic strictures
* Also higher risk for malignancy
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** Close discussion with gastroenterologist regarding when surgery is indicated
** Remember Crohn's is incurable, and long-term goal is to minimise length of bowel resected
** Inflammatory strictures may be treatable with steroids
** Fibrotic strictures - adalimumab, endoscopic dilatation
** In these patients, consider nutritional status, immunosuppressants may inhibit wound healing and try to optimise
** 60% of medical treatment of strictures fails and 40% of endoscopic dilatation fails
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|Infections
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** TB
** Actinomycosis
** Diverticulitis
** Mesenteric adenitis
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|Traumatic
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** Haematoma
** Ischaemic stricture
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|Intussusception

* Rare in adults (1-5% of SBO)
* Benign lesions
** Meckel's
** Polyps 
* Malignant lesions
** Primary or metastatic tumour
* Other
** Anastomotic (e.g. retrograde intussusception of RYGB anastomosis)
** Adhesions
** IBD
** Idiopathic - no lead point 8-20%
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** Usually secondary to a pathological lead-point such as a polyp or tumour
** The lead point is pulled forward by normal peristalsis, resulting in telescoping of the intussusceptum (bowel with lead point) within the intussuscipiens (surrounding normal bowel)
** Malignancy rate varies depending on source - Sabiston says mostly benign in adults, as malignant lesions tend to obstruct via tumour infiltration and adhesions, rather than intussusception. But in the literature, around 60-70% seem to be malignant based on reviews as of 2024.
** Increased incidence along with AIDS - Kaposi, NHL, lymphoid hyperplasia
** Generally, resect. Can start laparoscopic and then in most hands exteriorise the segment through a mini-laparotomy. Perform an oncological resection if in doubt. If benign aetiology suspected, can reduce the intussusception prior to resection, to decrease the length of resection.
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|Endometriosis
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|Radiation enteropathy/stricture
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|'''Intra-luminal'''
|Gallstone
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|Enterolith
|Often originating from a jejunal diverticulum - see separate topic
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|Foreign body/bezoar

* Phytobezoars (vegetables or fruits - persimmons, popcorn)
* Trichobezoars (hair)
* Parasitic (ascaris lumbricoides in distal ileum)
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