Sigmoid volvulus

"Twisting of the sigmoid colon causing obstruction"

Epidemiology

• Causes about 10% of LBO
• Can be the initial presentation of Hirschsprung disease

Risk factors - mostly leading to chronic constipation

Patient

• Mean age 70
• Higher incidence in men
• Often institutionalised and debilitated due to underlying neurologic or psychiatric disease
• History of constipation - might cause elongation and dilation
• Can occur in younger patients with abnormal colonic motility

Anatomical

• Long redundant sigmoid colon with a narrow mesenteric attachment

Pathophysiology

• Occurs when an air-filled loop of sigmoid colon twists about its mesentery - usually clockwise
• Theorised to result from a narrowing of mesenteric base, and absence of usual sidewall adhesions, that can leave it vulnerable to twisting
• Obstruction of the lumen occurs at 180 degrees, and impairment of perfusion occur at 360 degrees
  • I think that some radiologists think the 180 degree twist is not volvulus
• 'Ileosigmoid knotting' occurs when the ileum wraps itself around the sigmoid, usually clockwise

Presentation

• Insidious onset of slowly progressive abdominal pain (continuous and severe, with superimposed colic), nausea, distension, constipation
• Usually present 3-4 days after symptom onset
• Might be 'emptiness' in LIF
• Fever, tachycardia, hypotension, guarding, rigidity, and rebound tenderness indicate perforation/peritonitis/reduced perfusion

Imaging

• Classic sign on XR, inverted U pointing to RUQ for sigmoid volvulus (which are 90% of them) - bent inner tube sign
• Differentiating between sigmoid and caecal volvulus on AXR
  • Northern exposure sign - apex of volvulus reaches above transverse - quite specific for sigmoid
  • Caecal volvulus usually has one air-fluid level, whereas sigmoid usually has 3+
  • Look for LBO in sigmoid volvulus
• Water-soluble enema - bird's beak deformity
• CT is very specific and sensitive - whirl sign at point of obstruction, bird's beak appearance of afferent and efferent segments, absence of rectal gas

Management

• Resuscitation
• Immediate surgery if there are signs of peritonitis/bowel compromise
  • Resect without detorting if the bowel is strangulated, to avoid reperfusion injury
• Otherwise endoscopic detorsion
  • Can be done with either rigid or flexi sig (flexi better, since you can see whether mucosa is ischaemic). If you fail with rigid, can try with flexi.
  • Leave a rectal tube in situ, attached to a bag
  • Successful in 60-90% of patients, although 70% have recurrence, so should have definitive operation in initial hospitalization. More likely to fail with caecum >10cm or gangrene. Aim to operate within 24-48 hours if successful. Operate immediately if unable to decompress endoscopically.
• Definitive operation
  • Get stoma marked if possible
  • Lower midline laparotomy (some say LIF muscle-splitting incision is less morbid and just as easy)
  • Hartmann's procedure if systemically compromised (50% need it)
  • Primary anastomosis if well +/- covering ileostomy
  • May require subtotal colectomy if LBO is compromising proximal colon
• Non-resectional surgery
  • Inferior - not recommended
  • Percutaneous endoscopic colostomy and percutaneous endoscopic sigmoidopexy are reserved for selected non-operative candidates, having had multiple recurrences. High incidence of complications.