Small bowel obstruction

Acute, mechanical small bowel obstruction is a common surgical emergency  It is universally fatal if left untreated, progressing to intestinal necrosis, perforation, sepsis, and multisystem organ failure.

Step 1: Pathway Entry

Symptoms to consider: Abdominal pain, bloating, nausea, vomiting, inability to pass flatus or stool

Signs to consider: Abdominal distension, abdominal tenderness, peritonitis, hyperactive and high pitched bowel sounds, presence of hernias

Common risk factors in adults:

  • Previous abdominal or pelvic surgery (with the formation of intra-abdominal adhesions).

  • Abdominal wall or groin hernia, such as inguinal hernia with incarceration

  • Intestinal inflammation, such as diverticulitis or Crohn's disease

  • Intestinal malignancy (prior hx or risk factors for neoplasm)

Rare causes include radiation enteritis, foreign body ingestion, intra-abdominal abscess (e.g. perforated appendicitis/diverticulitis), gallstone ileus, intestinal bezoar, intussusception and volvulus.

Step 2: Is the Patient Stable?

  • Initiate resuscitation measures if required.

  • Consideration of other life-threatening diagnoses with similar symptoms (Perforated viscus, Pancreatitis, AAA)

Step 3: Detailed Initial Assessment

  • In the stable patient a thorough assessment is the next step including a detailed history, a detailed examination, blood tests including FBC, EUC, LFTs, lipase, BSL, an ECG and a CXR. Beta-HCG in women of childbearing age, VBG for lactate.

  • If an alternative diagnosis is made at this time then the steps further down the pathway can be curtailed.

Step 4: Imaging

Plain films: Initial imaging should include upright CXR and erect/supine AXR films (or lateral decubitus film if the patient cannot sit upright) - these have a sensitivity of 70-83% and specificity of 67-83% for small bowel obstruction. Plain film findings that suggest small bowel obstruction include:

  • Dilated loops of bowel with air fluid levels - presence of >5 fluid levels.
  • Proximal bowel dialation with distal bowel collapse - proximal small bowel dilated more than >2.5cm.
  • Gasless abdomen

CT abdomen: provides more information than plain films. May be useful to identify the specific site (i.e. transition point) and severity of the obstruction (partial vs complete). It will also give information about the aetiology, by identifying hernias, masses or inflammatory changes, and potential complications, such as ischaemia or perforation.

Step 5: Management

Emergency surgery is indicated in:

  • Perforation or impending perforation

  • Strangulated small bowel obstruction

Patients considered for emergency surgery should be receive preoperative antibiotic prophylaxis and made NBM in preparation for surgery in addition to supportive case detailed below.

All patients should receive supportive care:

  • NBM until surgical review

  • IV fluids

  • Monitoring of urine output

  • Analgesia

  • Anti-emetics can be a useful for emesis and/or nausea in cases where surgery is contraindicated (ondansetron 4mg IV q8H prn)

    • NG tube for gastric decompression only when vomiting or severe symptoms as a result of gastric distention

Patients who do not require emergency surgery are initially treated conservatively for 48-72 hours. Failure to respond to conservative treatment would lead to consideration for surgery.

Gastrografin may be diagnostic and therapeutic in SBO due to surgical adhesions. The appearance of water-soluble contrast in the colon on an abdominal X ray within 24 hours of its administration predicts resolution of an adhesive small bowel obstruction. While gastrografin does not reduce the need for surgery it does reduce hospital stay in those patients who do not require surgery.

© Agency for Clinical Innovation 2020

Send us feedback on the site