Snapshot A 47-year-old woman on the surgery floor complains of abdominal pain and bloating. She was admitted for appendicitis and underwent a laparoscopic appendectomy 2 days ago. She reports feeling fine since the surgery and denies any fever, swelling, hematuria, hematochezia, or nausea. Her last bowel movement was 3 days ago and she denies any flatulence. A physical examination is unremarkable except for a lack of bowel sounds. Introduction Clinical definition medical condition characterized by the disruption of the normal coordinated propulsive motor activity (peristalsis) of the gastrointestinal tract without any structural/mechanical obstruction Epidemiology Demographics gastrointestinal/abdominal surgery is the most common cause Risk factors gastrointestinal surgery electrolyte imbalance (e.g., hypokalemia or hypercalcemia) diabetes medications (e.g., opioids or antimuscarinics) spinal cord injury severe illness hypothyroidism acute intermittent porphyria ETIOLOGY Pathogenesis the degree of intestinal paralysis does not need to be complete but enough to functionally prohibit the passage of food leading to intestinal blockage normal gastrointestinal motility is controlled and facilitated by a complex network of various neural networks and neurohumoral peptides enteric nervous system, which is the intrinsic neural network of the gastrointestinal system extrinsic network consists of the visceral sensory afferents of the vagus, splanchnic, and pelvic nerves as well as the visceral motor efferent of the autonomic nervous system gastrointestinal dysmotility can result from various mechanisms inflammation (e.g., surgery or severe illness) neural reflexes neurohumoral peptides (e.g., certain medications) Presentation Symptoms abdominal pain rarely presents as the colicky pain present in mechanical bowel obstruction nausea vomiting vague discomfort Physical exam abdominal distension lack of bowel sounds on auscultation in contrast to the high-pitched tinkling sounds in mechanical bowel obstruction no abdominal tenderness imaging Abdominal radiograph best initial test supine and upright views positive findings may show dilated loops of bowel without a transition zone, air-fluid levels, and air in the colon and rectum allows for rule out of other causes of abdominal pain (e.g., perforated viscus) Studies Diagnostic testing diagnostic approach diagnosis is often based on clinical presentation followed by rule out of other causes of bowel obstruction studies laboratory studies are to be ordered given the clinical presentation to determine etiology/cause electrolyte panel hypokalemia and hypercalcemia may worsen ileus; hypomagnesemia can lead to hypokalemia creatinine and blood urea nitrogen uremia can lead to ileus liver function tests, amylase, and lipase pancreatitis may lead to ileus thyroid panel hypothyroidism may lead to ileus Differential Mechanical bowel obstruction differentiating factors physical examination will demonstrate high-pitched tinkling and history will often include colicky abdominal pain Pancreatitis differentiating factors although can lead to paralytic ileus, patients with pure pancreatitis will not have dilated bowels on imaging Treatment First-line supportive management NPO or dietary restriction if severe, nasogastric suction with parenteral nutrition IV fluids address underlying etiology remove offending medication if applicable replace electrolytes facilitate bowel movements lactulose erythromycin neostigmine for severe cases thought to have a neurological component (e.g., Oglivie syndrome) Complications Perforation Bowel necrosis/ischemia Peritonitis Hemodynamic instability Death