What are the causes of paralytic ileus?

Causes of Paralytic Ileus

Paralytic ileus is primarily caused by impaired intestinal motility due to neurological, inflammatory, metabolic, or pharmacological factors, with postoperative status and opioid medications being the most common precipitating factors. 1, 2

Postoperative Causes

• Abdominal surgery is a leading cause of paralytic ileus, with the severity related to the extent of intestinal manipulation during surgery 3, 1
• Laparoscopic approaches result in less severe ileus compared to open surgical procedures 4
• Fluid overload during perioperative management can significantly worsen and prolong postoperative ileus 3, 4
• Construction of defunctioning loop ileostomies during rectal resection increases the risk of prolonged postoperative paralytic ileus 5

Pharmacological Causes

• Opioid medications are major contributors to paralytic ileus through their inhibitory effects on intestinal motility 3, 1
• Anticholinergic medications (e.g., phenothiazines, tricyclic antidepressants) can cause severe dysmotility 3
• Other medications associated with paralytic ileus include:
  • Clozapine (with evidence for dose dependence) 3
  • Baclofen, buserelin, clonidine, fludaribine, phenytoin, and verapamil 3
  • Vincristine (directly neurotoxic, causing visceral neuropathy) 3

Neurological Causes

• Disorders affecting the parasympathetic or sympathetic nerves that innervate the gut can cause paralytic ileus 3
• Diabetes mellitus is the most common endocrine cause of autonomic neuropathy leading to gut dysmotility 3
• Other neurological conditions associated with paralytic ileus include:
  • Brainstem lesions and spinal cord injury 3
  • Multiple sclerosis and Parkinson's disease 3
  • Myotonic dystrophy and porphyria 3

Infectious and Inflammatory Causes

• Sepsis and severe systemic inflammatory response can trigger paralytic ileus 2
• Peritonitis from any cause can lead to paralytic ileus 2
• Specific infections associated with paralytic ileus include:
  • Strongyloidiasis hyperinfection syndrome in immunocompromised patients 2
  • Herpes viruses (Epstein-Barr virus and cytomegalovirus) 3
  • Polyoma viruses (John Cunningham virus) 3
  • Chagas' disease (South American trypanosomiasis) 3
  • Lyme disease and botulism 3

Metabolic and Electrolyte Causes

• Electrolyte abnormalities, particularly hypokalemia and hypomagnesemia, can cause paralytic ileus 4
• Hypothyroidism can lead to intestinal dysmotility 3
• Other metabolic disorders affecting gut motility can precipitate paralytic ileus 3

Autoimmune Causes

• Paraneoplastic syndromes, particularly with anti-neuronal nuclear antibody (ANNA-1 or anti-Hu), can cause enteral neuropathy 3
• Small cell lung cancer, carcinoid tumors, neuroblastoma, and thymoma with anti-neuronal nuclear antibodies can cause paralytic ileus 3
• Other auto-antibodies associated with dysmotility include:
  • Acetylcholinesterase receptor antibody (AchR) 3
  • Antibodies against voltage-gated potassium channel-complex (VGKC-complex) 3
  • Voltage-gated calcium channel antibodies (VGCC) 3

Toxic Causes

• Lead poisoning can be a rare reversible cause of paralytic ileus 3
• Various toxins affecting neuromuscular function can impair intestinal motility 3

Clinical Pearls and Pitfalls

• Postoperative ileus is the single largest factor influencing length of hospital stay after bowel resection 6
• Early mobilization helps stimulate bowel function and can prevent prolonged ileus 1, 4
• Thoracic epidural analgesia can significantly reduce the risk of postoperative ileus compared to systemic opioid analgesia 3, 4
• Prokinetic agents may help stimulate gastrointestinal motility in cases of paralytic ileus 1, 7
• Avoiding fluid overload is crucial as it can worsen intestinal edema and prolong ileus 3, 4