Acute Ileal Diverticulitis: Computed Tomography and Ultrasound Findings
Executive Summary
Acute ileal diverticulitis (AID) is an exceptionally rare condition that frequently mimics the clinical presentation of acute appendicitis. Due to its low prevalence and nonspecific symptoms, AID is often misdiagnosed, historically leading to high mortality rates ranging from 25% to 50%. This briefing synthesizes clinical data and radiological findings from a 15-year retrospective study of 17 confirmed cases.
The critical takeaways for clinicians and radiologists are:
Clinical Presentation: AID typically presents as right lower quadrant (RLQ) pain in elderly patients (median age 59), often accompanied by leukocytosis and elevated C-reactive protein (CRP).
Radiological Markers: Both Computed Tomography (CT) and Ultrasonography (US) demonstrate high diagnostic utility. Key markers include ileal wall thickening, identification of an inflamed diverticular sac on the mesenteric side, and surrounding mesenteric fat infiltration.
Management Shifts: While historically treated via exploratory laparotomy, modern imaging allows for accurate preoperative diagnosis, facilitating successful conservative management with antibiotics, even in cases involving localized perforation.
Introduction to Ileal Diverticular Disease
Non-Meckel ileal diverticula are acquired "false" diverticula, consisting only of the mucosa, submucosa, and serosa. They are distinct from Meckel diverticula, which are congenital "true" diverticula containing all four layers of the intestinal wall, including the muscular layer.
Pathophysiological Characteristics
Location: Non-Meckel diverticula are almost exclusively located along the mesenteric border.
Prevalence: Acquired jejunoileal diverticula are rare, with incidence rates between 0.5% and 2.3%. Only 20% of these occur in the ileum, and only 10% of those develop complications, making AID an extremely rare clinical entity.
Anatomy: They are commonly found near the ileocecal valve, likely due to increased intraluminal pressure and the specific vascular architecture (larger vasa recta) of that region.
Clinical Presentation and Diagnostic Challenges
The primary challenge of AID is its tendency to masquerade as other common causes of acute abdominal pain.
Patient Profile and Symptoms
Based on the study of 17 patients (11 men, 6 women):
Primary Complaint: Abdominal pain localized to the RLQ was present in 82.3% of cases.
Associated Symptoms: Febrile sensations (46.7%), vomiting, chills, and diarrhea.
Laboratory Findings: Leukocytosis (>10,000/mL) was observed in 80% of patients, and 100% of tested patients showed elevated CRP levels.
Initial Misdiagnosis: The most common provisional impressions included appendicitis, stump appendicitis, cholecystitis, and fever of unknown origin.
Radiological Analysis
The advent of multi-detector CT (MDCT) and high-resolution US has shifted the diagnostic paradigm from exploratory surgery to non-invasive identification.
Computed Tomography (CT) Findings
CT is highly effective in visualizing the hallmarks of AID. The study identified several consistent features:
Ultrasonography (US) and Color Doppler Imaging (CDI)
US serves as a vital screening tool, particularly in excluding appendicitis. Modern US machines provide high spatial resolution for bowel imaging.
Diverticular Sac: 100% of cases showed an outpouching inflamed sac connecting to the ileum.
Fat Infiltration: 100% of cases showed peridiverticular inflamed fat, appearing as non-compressible hyperechoic fat.
Vascularity: 100% of cases showed increased color flow to the diverticulum and surrounding fat on Color Doppler Imaging (CDI).
Layering: 94.1% of patients exhibited ileal wall thickening while maintaining a preserved layering pattern.
Complications and Perforation Analysis
Perforation is the most significant complication of AID. In the study, the perforation group (n=7) was compared against the non-perforation group (n=9).
Perforation Markers
Perforation is identified via CT or US through:
Abscess formation.
Extraluminal fluid with air.
Focal defects in the diverticular sac.
Extraluminal air bubbles (appearing as tiny hyperechoic reverberating dots on US).
Comparison of Clinical Outcomes
The study noted that the size of the inflamed diverticulum was significantly smaller in the perforation group, likely because the sac collapses following the release of contents into the extraluminal space.
Management and Outcomes
Historically, surgical intervention was the standard for perforated AID. However, current evidence suggests that conservative management is often sufficient.
Antibiotic Therapy: 15 out of 17 patients in the study were treated successfully with oral or intravenous antibiotics.
Conservative Recovery: 16 out of 17 patients (94.1%) fully recovered without surgical intervention, including those with localized perforations or abscesses, provided there was no evidence of generalized peritonitis.
Surgical Referral: Surgery is generally reserved for cases that do not respond to conservative measures or those presenting with generalized peritonitis.
Conclusion
Acute ileal diverticulitis, while rare, must be included in the differential diagnosis for elderly patients presenting with acute RLQ pain and a normal appendix. Accurate diagnosis relies on recognizing the mesenteric location of the inflamed diverticulum and associated ileal wall thickening. Both CT and US are complementary and highly effective in identifying these markers, allowing for a shift toward conservative, non-operative management and improved patient outcomes.
