Bowel Obstruction

Introduction

Bowel obstruction is generally described as

  • Small Bowel (80%) or Large Bowel (20%)

  • Complete or partial

  • Simple or strangulated

Causes

Small Bowel Obstruction

  • Adhesions from previous surgery/infection (~75% of cases)

  • External Hernias – inguinal, femoral, incisional, umbilical

  • Neoplasms

  • Rarer causes = strictures e.g. IBD, internal hernias, foreign bodies

  • Paediatrics = Intussusception, malrotation, volvulus, congenital lesions

Large Bowel Obstruction

  • Neoplasm

  • Diverticulitis

  • Volvulus - Caecal or sigmoid.

    • Sigmoid more common in elderly, chronically constipated, neuro conditions

  • Rarer = Hernias, Strictures, IBD, Extra intestinal tumours, Faecal impaction

Clinical Features

Symptoms

Pain

  • Initially colicky. Can be more severe and constant with strangulation

Vomiting

  • Occurs more commonly and earlier in SBO. Bilious vomiting = proximal obstruction

  • Occurs later in LBO. Faeculant vomiting implies distal obstruction

Constipation/Not passing flatus

  • Late sign. Passing stool or flatus does NOT out rule diagnosis

Bloating

Signs

Signs of sepsis - concerning for perforation

Signs of dehydration

Abdominal Signs

  • Scars, Hernias, Distension (more common with LBO),

  • Tenderness. If frank rebound or rigidity concerning for peritonitis

  • Hypertympanic percussion note (more common in LBO)

  • Bowel Sounds – may initially be increased but over time become silent

Complications

Volume depletion  from vomiting and third space losses

Electrolyte disturbances

  • Hypokalaemia

  • Hyponatraemia

  • Hypernatraemia

  • metabolic alkalosis from vomiting

  • Lactic acidosis from ischaemia/sepsis

Strangulation of bowel

  • ischaemia

  • perforation & peritonitis

  • septicaemia

  • shock

  • death

Differential Diagnosis

 

Gastro-intestinal

  • Diverticulitis

  • Appendicitis

  • Psuedo-obstruction

  • Inflammatory bowel disease

  • Ileus

Vascular

  • Mesenteric ischaemic

  • Ruptured AAA

Infective / Inflammatory

  • Cholecystitis

  • Pancreatitis

  • Pelvic inflammatory disease (PID)

Metabolic

  • Diabetic ketoacidosis (DKA)

  • Hyperosmolar hyperglycaemic state (HHS)

Clinical Investigations

Bedside

  • Urinalysis – can aid in excluding UTI. Urinary BHCG in all women of child bearing age

  • VBG + Glucose – Looking for metabolic alkalosis (pH, HCO3, CO2, Lactate, electrolytes, BM, Hb)

  • ECG – mesenteric ischaemia more common with AFib

  • POCUS – out rule AAA/free fluid. SBO can be diagnosed by POCUS in experienced hands

Laboratory

  • FBC – may show leucocytosis

  • CRP – usually elevated

  • U&E – may show AKI if septic or dehydrated

  • LFT + Amylase – looking for other dx

  • CoAg – if on anticoagulants or going to OT.

Radiology

 
SBO+%2B+LBO.jpg

Abdominal X-Ray

AXR erect/supine – 75% sens, 50% spec for SBO

SBO - Valvulae conniventes are visible, predominantly centrally located dilated loops (>3cm) proximal to obstruction, > 5 air/fluid levels

LBO - Haustra visible, Peripherally located dilated loops (>6cm),  May be concurrent dilated small bowel, Rectum has little or no air, Pneumoperitoneum

Caecal Volvulus - single gas fluid level in dilated (>9cm) air filled caecum in mid abdomen of LUQ. “Kidney bean sign”

Sigmoid Volvulus - Single dilated loop of colon with both ends orientated towards pelvis. “Coffee bean sign”

Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 17957

Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 17957

Erect CXR

Looking for free air under diaphragm indicating perforation

Case courtesy of Dr Jeremy Jones, Radiopaedia.org, rID: 6135

Case courtesy of Dr Jeremy Jones, Radiopaedia.org, rID: 6135

CT Abdomen with Contrast

Gold standard. 95% sensitive and specific

Can establish diagnosis, level of obstruction, the cause and presence of complications

Management and Disposition

Initial Resuscitation

  • IV Access and fluids as clinically indicate

  • Pt may be in shock and require inotropes and organ support

Specific Treatment

  • Nil orally.

  • If vomiting prominent in SBO —> NG on free drainage

  • If septic consider broad spectrum IV antibiotics that provide gram negative and anaerobic cover as per local guidelines

    • e.g. IV Co-amoxiclav + IV Metronidazole

  • Large bowel obstruction/sigmoid volvulus —> decompression with rectal tube by surgeons may be effective

  • Laparotomy required if concern for ischaemia, perforation, peritonitis etc.

Symptomatic Treatment

  • Analgesia as required asap – usually IV opioid

  • Anti-emetic as required

Disposition

  • Refer all suspected cases to the on call surgical team for admission.

  • Conservative watch and wait vs operative management is a decision for the surgeons

 References

1.     Dunn et al. Chapter 37: Abdominal pain. Bowel Obstruction. “The Emergency Medicine Manual” 5th Edition. Vol 1.

This blog was written by Dr. Deirdre Glynn and was last updated in October 2020

Before you go have another look at the clinical case and see have your answers to any of the questions changed and if so how?