First Things First (assess & treat for the following)

The first step in dealing w/ gut dysmotility is to differentiate ileus from obstruction. Whereas ileus typically resolves w/ supportive care only, & without sequelae, obstruction rarely resolves w/out surgical intervention & can have serious consequences if not aggressively managed.

• Ileus is functional failure (no demonstrable obstruction) of the gut to propel contents & can be classified as:
  • Adynamic ileus is an inhibition of the neuromuscular complex, also referred to as pseudo-obstruction.
    • Primary adynamic ileus is idiopathic (ie, Ogilvie’s syndrome).
    • Most adynamic ileus is secondary to well-known causes:
      • Postop ileus related to CNS & neural reflexes, hormones, medication & anesthetic agents is normal when it involves the small bowel for up to 24 hrs, the stomach up to 48 hrs & the colon for up to 72 hrs.
      • When postop ileus is prolonged or recurrent, considerations should include:
        • Intra-abdominal inflammation
        • Systemic sepsis
        • Intra-abdominal or retroperitoneal hematoma
        • Occult wound infection
      • Commonly seen after trauma, including:
        • Spinal cord injury
        • Spine fracture
        • Rib fractures
        • Pelvic fracture
      • Common w/ pulmonary atelectasis or pneumonia in the basal segments
      • Drugs that inhibit gut motility include:
        • Narcotics
        • Anticholinergic agents
        • Antihistamines
        • Psychotropic drugs such as haloperidol or tricyclic antidepressants
        • Phenothiazines
        • Ganglionic blocking agents
      • Metabolic causes of ileus are common:
        • Hypokalemia
        • Hyponatremia
        • Hypomagnesemia
      • Other metabolic causes include:
        • Uremia
        • Diabetes
        • Hypoparathyroidism
      • Miscellaneous causes
        • Scleroderma
        • Amyloidosis
  • Spastic ileus is related to hypermotility where uncoordinated peristalsis fails to push contents through.
  • Ischemic ileus is related to vascular occlusion & infarction of the myoelectric components.

• Obstruction is the physical barrier to movement of bowel contents. In general, the 3 categories include:
  • Extraluminal causes
    • Adhesions
    • Hernias
    • Carcinomas
    • Abscesses
  • Lesions intrinsic to the bowel wall
    • Primary tumors
    • Inflammatory bowel disease (Crohn’s disease)
  • Intraluminal causes
    • Gallstones
    • Enteroliths
    • Foreign bodies
    • Bezoars
  • 80% of bowel obstruction involves the small bowel; the most common etiologies are:
    • Postop adhesions (65-80%); pelvic procedures, specifically gynecologic, appendectomy & colorectal resection, account for 60% of obstructions due to adhesions
    • Hernia (15-25%)
      • Ventral hernia is the most common.
      • Inguinal & internal hernias are common.
      • Less common are femoral, obturator, lumbar & sciatic.
    • Tumors (10-15%)
      
      • The majority are metastatic lesions that implant through hematogenous spread to the peritoneum.
      • Large intra-abdominal tumors can cause obstruction from extraluminal compression.
      • Obstructing primary small bowel tumors are rare.
    • Crohn’s disease (5%) is the 4th leading cause of small bowel obstruction.
      • Inflammation & edema that resolves w/ nonoperative mgt
      • Stricture that may require resection & reanastomosis or stricturoplasty
    • Abscess can cause obstruction by involving a portion of the intestinal wall, by adhesion or as a result of localized ileus & functional obstruction. Common etiologies include:
      • Ruptured appendix
      • Diverticulitis
      • Dehiscence of abdominal anastomosis
    • Miscellaneous other etiologies include:
      • Intussusception, more common in children; in adults is usually associated w/ a lead point such as a polyp, tumor or Meckel’s diverticulum
      • Enteroliths from jejunal diverticula
      • Foreign bodies
      • Phytobezoars
  • 20% of obstructions involve the colon; the most common etiologies include:
    • Cancer (60%)
    • Diverticulitis (15%)
    • Volvulus (15%)

If obstruction is present, the second step is to determine whether & how urgently surgical intervention is needed.

• Only about 20% of partial obstructions will require surgical intervention, which can usually be done on a semi-elective (planned) basis.

• Complete obstruction almost always requires surgical intervention, usually on an emergency basis.

• The vast majority of obstructions are classified as simple, implying an intact blood supply (ie, gallstone ileus).

• Strangulated obstruction implies mesenteric vessel occlusion & is associated w/ a higher morbidity & mortality; therefore, early recognition is important.

• Closed loop obstruction involves occlusion of both afferent & efferent limbs of bowel & is especially dangerous because of rapid progression to strangulation & perforation even before clinical evidence of obstruction. The following closed loop obstructions require emergent surgical intervention if bowel resection is to be avoided:
  • Volvulus
  • Incarcerated ventral hernia
  • Congenital bands
  • Adhesions
  • Malrotation
  • Internal hernia