Gastric outlet obstruction

Aetiology

• Previously mostly benign, but with the improved treatment of PUD, now 50-80% malignant
• Malignancy
  • 35% gastric CA
    • Adenocarcinoma 90%
  • 20% pancreatic CA
  • Gastric lymphoma
    • Most common of GIT lymphomas
    • Treat with CTX alone
  • Gallbladder CA with local extension
  • Duodenal CA - primary or mets
  • Gastric carcinoid
  • GIST
    • Interstitial cells of Cajal
• Benign
  • Intramural
    • PUD - rare complication (<5%)
      • Acutely - inflammatory swelling, accompanied by duodenal peristaltic dysfunction
      • Chronically - scarring at gastric outlet
      • Manage with medical therapy (PPIs, avoid risk factors), then endoscopic pneumatic dilation, then surgical (truncal vagotomy)
    • Crohn's - 5% show gastroduodenal involvement
      • Proximal Crohns = nonspecific gastritis type symptoms
    • Pyloric stenosis
    • Caustic injury due to poison ingestion
      • Occurs due to fibrosis, 6-12 weeks post injury
      • Incidence 5-10% after caustic ingestion
    • Gastric TB
    • Gastric volvulus - seen in older adults, generally related to hernia (greatest risk type III)
      • Borchardt's triad - sudden epigastric pain, intractible retching/vomiting, inability to pass NGT
      • True surgical emergency
      • CT - GOO with abnormal location of gastric outlet, non-passage of enteric contrast material, gastric wall thickening, adjacent fluid or fat stranding
      • CR - NGT coiled in gastric body, which is located in chest
      • Upper endoscopy can be both diagnostic and therapeutic
    • Post-surgical complications
  • Intraluminal
    • Bouveret syndrome - pyloric impaction of a gallstone
    • Large gastric polyps
    • Bezoars
    • PEG migration
  • External compression
    • Acute/chronic pancreatitis - 1-5% show GOO
      • Can occur with peripancreatic fibrosis or giant pseudocyst
    • Annular pancreas
  • Dysmotility

Pathophysiology

• Often see hypokalaemic, hypochloraemic metabolic alkalosis
  • Loss of gastric juice rich in hydrogen, chloride and potassium
  • Hypovolaemia causes ADH activation which causes hyponatraemia
  • Hypovolaemia and hyponatraemia activates RAAS
  • Kidney tries to correct hyponatraemia by exchanging sodium for hydrogen and potassium ions (under stimulation of RAAS), causing paradoxical aciduria and worsening alkalosis/hypokalaemia
  • Hypokalaemia is due to gastric and renal losses as well as intracellular shift to maintain membrane polarity

Clinical manifestations

• Nausea/vomiting - with undigested foodstuffs from days previously noted
  • No bile staining in vomit
• Epigastric pain - particularly post-prandial, and relieved by vomiting
• Weight loss
• Early satiety
• Abdo distension
• Examination
  • Succussion splash
    • Listen to abdomen while shaking patient from side to side
    • Pathologic if heard >3 hours post meal
  • Virchow's node/sister mary joseph node

Investigation

• Electrolyte abnormalities as above
• Plain film - enlarged gastric bubble
• Barium swallow - can show a complete obstruction, if no contrast in small bowel

Management

• Not a surgical emergency - aim to resuscitate, diagnose then treat
• NBM + IVF
  • Normal saline + potassium good for treating hypokalaemic, hypochloraemic metabolic alkalosis
• NGT
• Electrolyte replenishing
• PPI
• Endoscopy - rule out malignancy and assess for H. pylori infection
• Consider TPN + nutritional assessment
• Further management depends on cause

Gastric outlet obstruction secondary to PUD

• Results from chronic inflammation and scar formation
• Medical treatment
  • As above, with endoscopy and H. pylori testing
  • May be able to be treated conservatively, with oedema improving over time
• Endoscopic treatment
  • Endoscopic dilation +/- stenting is the mainstay of therapy
  • Novel techniques - US-guided gastric bypass and POEM
• Surgical treatment
  • Indications:
    • Obstruction refractory to endoscopic treatment
  • Gold standard operation is vagotomy and antrectomy
  • Other procedures
    • Bilroth II
    • Vagotomy with either Jaboulay gastroduodenostomy or gastrojejunostomy

Gastric resection

• May be able to just do a wedge resection
• Malignancy - if aiming for cure - oncologic gastric resection with wide margin
  • Distal stomach - needs a distal gastrectomy with a 6cm margin of normal gastric tissue
  • Billroth II technique preferred (decreased likelihood of obstructino with recurrence at anastamosis)