Editing Small bowel obstruction (section)

== '''Management principles''' ==

* Evaluate need for immediate operation (signs of strangulation or other specific aetiologies)
* If no indication for surgery, manage conservatively, with constant reassessment

=== '''Indications for surgery''' (based on Bologna guidelines 2017 for '''adhesive SBO''') ===

* On admission
** Clinically suspected strangulation/peritonitis (fever, tachycardia, leucocytosis, metabolic acidosis, continuous pain, radiological signs)
** Surgery in past 6/52 ''(UTD says trial non-op in these patients)''
** Irreducible hernia ''(or internal hernia)''
** No signs of resolution within 72hrs ''(in practice, this belongs to 'ongoing')''
* Ongoing
** Evolving peritoneal signs
** CRP >75
** WBC > 10 (persistently)
** Free intraperitoneal fluid > 500mL on CT
** Reduction of CT small bowel wall contrast enhancement
* Day 3
** Failed Gastrografin challenge
** Pain lasting 4 days or more
** Persistent ileus >72hrs
** NGT drainage volume >500mL on day 3

=== '''Non-operative management''' ===

* NBM + ice chips for comfort
* NGT 14 or 16Fr (check position ASAP to allow Gastrografin)
* IVF and electrolyte replacement
* Consider IDC
* Rationalise medications
* Antibiotics only if surgery is required
* Gastrografin given once outputs have settled to the point where it's safe to spigot NGT for 4-5 hours
** Note that '''GG does not increase the proportion of patients that avoid an operation''', but does decrease time to resolution (in patients that would have resolved anyway) and hospital stay. There is not strong evidence that it acts therapeutically.
** 100mL Gastrografin neat then spigot NGT until either patient opens bowels or patient has refractory nausea
** If no contrast in colon in 24/36hrs - surgery
*** Presence of GG in colon at 24 hours predicts non-op resolution with 97% specificity and 96% sensitivity
** Schein suggests give it 1-2 hours after NGT decompression

=== '''Specific situations:''' ===

* '''Complete SBO -''' monitor closely, generally needs OT
* '''Partial high-grade SBO (some gas in rectum) -''' initial observation, closely watched, may need theatre
* '''Partial low-grade SBO (bowels opening/passing flatus, but symptomatic on fluid intake) -''' can be safely watched in hospital
* '''SBO in virgin abdomen -''' Ask again about surgery, and check carefully for scars and hernias. Ask about history of trauma, and cancer that may have metastasised, and recent ingestion of bezoar-forming foods. According to one meta-analysis: 54% de novo adhesions, 11% malignancy, 2% internal hernia. The vast majority of patients will safely be managed non-operatively. It's worth thinking about outpatient workup for malignancy if non-op management is successful. This could be CT +/- MRI enteroclysis.
* '''SBO post-op -''' Mostly resolves with conservative management, consider TPN. >90% of early post-op obstructions are partial and will resolve spontaneously. However, need to be sure there are no signs of strangulation and no technical errors. Technical errors are more common after laparoscopic surgery, such as port site hernias.
* '''Recurrent SBO shortly after operation for same''' - initial non-op management. Very careful surgical technique. Many would advocate for prolonged non-op management and TPN until adhesions mature and the obstruction resolves. 
* '''Obstruction secondary to Crohn's -''' attempt conservative management with gut rest, TPN and steroids, involve medics, try to avoid OT. If have to operate, limited bowel resection or stricturoplasty.
* '''SBO with known intra-abdominal malignancy/potential recurrent malignancy -''' 30% have simple band adhesion, 30% need bowel resection, 30% inoperable - therefore probably deserve a laparotomy (aborting an operation may be better in many cases than not offering an operation that would have been simple). If they are already receiving palliative care input, and not far away from death, then less likely to offer an operation. 
* '''Malignant SBO (either primary or metastatic):''' median survival even with operation is 3-7 months, lower without (retrospective data), so a palliative procedure is not out of the question. Probably two types of patients - those with late cancer (do not operate), and those with first presentation of peritoneal disease (consider operating and debulking if good physiological reserve; think about patient's peritoneal carcinomatosis index (PCI)). Can sometimes offer bypass procedure.
* '''SBO secondary to abscess''' - percutaneous drainage may be sufficient, but laparotomy and washout may be the better option for large and established abscesses.
* '''SBO secondary to radiation enteropathy''' - follows a progressive course of gradually worsening partial obstructions, leading to a complete obstruction. Attempt to treat non-operatively, often with steroids. Can be a very difficult operation - paper-thin bowel, glued together and onto adjacent structures; accidental enterotomies are common and lead to fistulas. When longer segments are involved, bail out with an entero-enteric or entero-colic bypass. Poor prognosis no matter what you do.

=== '''Operation''' ===

* Midline laparotomy, taking care to avoid adhesions
* Lyse all adhesions necessary for safe visualisation of bowel
** It is not necessary to completely free the entire bowel - focus on the area of TP (and distal to that point if a bowel resection is performed)
** With frozen abdomen/bowel, you probably do need to release the entire bowel though.
** Enterotomies: leave superficial serosal tears alone, but repair anything where the mucosa pouts through the defect
* Run small bowel - start with a collapsed loop, and follow it proximally until the TP is identified. If no collapsed bowel is seen, start at ICV.
** If mass or neoplasm is encountered, needs to be resected with 8-10cm margins + lymphatics, and remember to look at abdomen for evidence of metastases
* Repair hernias - biologic mesh if contamination, otherwise synthetic as normal
* Evaluate bowel for ischaemia
** Fluoroscein dye - 500 to 1000mg IV in 10% solution - then use Wood's lamp to check perfusion
** Leave dusky bowel for 10 minutes and reassess before resecting
* Decompress the bowel by milking it back to the stomach

=== '''Selection criteria for laparoscopic surgery:''' ===

* Haemodynamic stability
* Absence of peritonitis or severe intra-abdominal sepsis
* Proximal (small bowel) obstruction - less distended
* Localised distension on radiography
* Absence of severe abdominal distension
* Anticipated single band
* Low anticipated Peritoneal Adhesion Index (i.e.: safe place to access abdomen)
** First episode SBO
* Experience/skill of surgeon
* Left upper quadrant/left flank usually the safest places to access abdomen. Use Hasson technique.