Ileus Causes and Associated Factors

Postoperative and Post-Traumatic Causes

• Abdominal surgery is the most common cause of ileus, resulting from manipulation during surgery, anesthetics, and opioid use 2, 1
• Trauma, especially abdominal trauma, can lead to ileus through inflammatory mechanisms and neural disruption 1, 3

Inflammatory and Infectious Causes

• Sepsis and systemic inflammatory response syndrome can cause ileus through inflammatory mediators 1
• Peritonitis from any cause can trigger ileus 3
• Intestinal inflammation due to inflammatory bowel disease, especially ulcerative colitis, can cause ileus 4, 5
• Infections such as Chagas' disease, Lyme disease, and viral infections, including Epstein-Barr virus, cytomegalovirus, and JC virus, can cause ileus 6

Metabolic and Endocrine Causes

• Electrolyte disturbances, particularly hypokalemia, hypocalcemia, and hypomagnesemia, can cause ileus 1, 3
• Endocrine disorders, including hypothyroidism, diabetes mellitus, hypoparathyroidism, and Addison's disease, can cause ileus 7, 1
• Uremia and other metabolic derangements can cause ileus 3

Medication-Related Causes

• Opioids are a major cause of ileus through their action on μ-opioid receptors in the gastrointestinal tract 1
• Anticholinergics, including phenothiazines and tricyclic antidepressants, can cause ileus 6, 1
• Other medications associated with ileus include verapamil, clozapine, baclofen, buserelin, clonidine, fludaribine, and phenytoin 6
• NSAIDs can exacerbate ileus, particularly in patients with inflammatory bowel disease or after surgery 5

Neurological Causes

• Primary visceral neuropathies affecting the enteric nervous system can cause ileus 6
• Secondary neuropathies, such as those associated with Parkinson's disease, multiple sclerosis, autonomic neuropathy, spinal cord injury, and brainstem lesions, can cause ileus 6, 7

Autoimmune and Paraneoplastic Causes

• Paraneoplastic syndromes, particularly associated with small cell lung cancer, thymoma, neuroblastoma, and carcinoid tumors, can cause ileus 6
• Autoimmune disorders with anti-neuronal antibodies, such as anti-Hu, CRMP5, and AchR, can cause ileus 6
• Scleroderma and other connective tissue diseases affecting gut motility can cause ileus 3

Toxin-Related Causes

• Lead poisoning can cause ileus 6
• Botulism can cause ileus 6

Vascular Causes

• Mesenteric ischemia can cause ileus through damage to the intestinal muscle and nerves 7

Diagnostic Approach

• Clinical presentation of ileus includes abdominal distension, absence of bowel sounds, nausea, vomiting, and lack of flatus or bowel movements 1
• Radiological findings typically show dilated bowel loops with air-fluid levels but no transition point 1
• CT scan is the most useful imaging modality to differentiate between ileus and mechanical obstruction 1