What are the typical clinical signs and symptoms of an ileus?

Clinical Signs of Ileus

Ileus presents with abdominal distension, absence of bowel sounds or hypoactive bowel sounds, intolerance to oral intake, nausea and vomiting, and failure to pass flatus or stool. 1, 2

Cardinal Clinical Features

Gastrointestinal Manifestations

• Abdominal distension is the most consistent physical finding, often accompanied by visible loops of dilated bowel 1, 2, 3
• Nausea and vomiting occur frequently, particularly when the obstruction involves more proximal segments 1, 3
• Failure to pass flatus or stool despite the urge, distinguishing ileus from simple constipation 1, 2
• Intolerance to oral diet with early satiety and postprandial discomfort 1
• Colicky abdominal pain may be present, though typically less severe than in mechanical obstruction 3

Physical Examination Findings

• Decreased or absent bowel sounds on auscultation, though this finding alone is neither sensitive nor specific 2
• Tympanic percussion over distended bowel loops 2
• Absence of peritoneal signs (no guarding, rigidity, or rebound tenderness) in uncomplicated ileus, which helps distinguish it from peritonitis 4, 2
• Palpable distended bowel loops in severe cases 5

Critical Distinguishing Features from Mechanical Obstruction

The key clinical challenge is differentiating functional ileus from mechanical small bowel obstruction, as management differs fundamentally. 2, 6

Features Suggesting Ileus Rather Than Mechanical Obstruction

• Gradual onset of symptoms rather than acute presentation 2
• Diffuse, generalized distension rather than localized 6
• Less severe pain that is constant rather than cramping/colicky 2, 3
• No "gush sign" on digital rectal examination (the pathognomonic finding of distal obstruction where passage of the examining finger releases accumulated proximal contents) 5

Red Flags Suggesting Mechanical Obstruction Requiring Urgent Intervention

• Severe, cramping colicky pain that comes in waves 2
• High-pitched or tinkling bowel sounds early in obstruction 2
• Localized tenderness or palpable mass 5
• Signs of peritonitis including fever, rigors, hemodynamic instability, or decreased bowel sounds progressing to silence 4

Associated Systemic Signs

Laboratory Abnormalities

• Electrolyte imbalances including hypokalemia, hyponatremia, or hypochloremia from vomiting and third-spacing 7
• Leukocytosis may occur but is not specific; marked elevation (>15 × 10⁹/L) suggests complications like ischemia or perforation 4
• Elevated serum lactate indicates possible bowel ischemia and requires urgent surgical evaluation 4
• Rising creatinine (>50% above baseline) from dehydration and prerenal azotemia 4

Systemic Manifestations

• Fever (>38.5°C) suggests complications such as bacterial translocation or perforation 4
• Hemodynamic instability including tachycardia and hypotension from fluid sequestration 4

Context-Specific Presentations

Postoperative Ileus

• Typically develops within 2 days of surgery, particularly abdominal procedures 1, 3
• Risk factors include significant blood loss, opioid analgesia, bowel manipulation, and electrolyte disturbances 3, 7
• Expected duration is 3-5 days for small bowel, longer for colon 1

Elderly Patients

• Many elderly patients present with signs consistent with ileus or bowel obstruction rather than classic appendicitis or other acute conditions 4
• Atypical presentations are common due to comorbidities and concurrent medications 4

Cancer-Related Ileus

• Patients with peritoneal carcinomatosis may have mixed mechanical and functional components that are difficult to distinguish 2
• Chronic opioid use for cancer pain can produce narcotic bowel syndrome mimicking or exacerbating ileus 5

Common Pitfalls to Avoid

• Do not rely solely on bowel sounds for diagnosis, as they correlate poorly with actual bowel function 2
• Do not dismiss symptoms in patients on opioids or anticholinergics without discontinuing these medications first, as they commonly cause pseudo-obstruction 5
• Do not delay imaging when clinical examination is equivocal; CT has 100% sensitivity and specificity for distinguishing ileus from complete mechanical obstruction 6
• Do not attribute all symptoms to IBS in patients with prior bowel surgery; nocturnal symptoms and steatorrhea are never features of IBS 4