Radiological Differences Between Caecal and Sigmoid Volvulus
The key radiological distinction is that sigmoid volvulus shows a "coffee bean sign" projecting toward the upper abdomen (sometimes above the transverse colon), while caecal volvulus presents as a distended loop extending from the right lower quadrant to the epigastrium or left upper quadrant with absent haustral markings.
Plain Abdominal Radiograph Findings
Sigmoid Volvulus
- Classic "coffee bean sign" - a massively dilated loop projecting toward the upper abdomen 1
- "Northern exposure sign" - the dilated sigmoid extends above the transverse colon 1
- The apex of the distended loop points superiorly and to the right 1
- Air-fluid levels may be present in the distended sigmoid 1
Caecal Volvulus
- Distended loop with its long axis extending from the right lower quadrant to the epigastrium or left upper quadrant 2
- Absent colonic haustral pattern in the distended segment 2
- Air-fluid colonic level may be visible in the left hypochondrium when the caecum has rotated to that position 3
- The distended caecum appears as a rounded focal collection of air-distended bowel, typically in the upper left quadrant 2
CT Imaging Findings
Sigmoid Volvulus
- "Whirl sign" - representing twisted colon and mesentery around the mesenteric vascular pedicle 1, 4
- Dilated sigmoid colon with air/fluid levels 1, 4
- Two transition points are typically visualized at the site of torsion 1
- The sigmoid can be either mesenteroaxial (twisting around mesenteric axis) or organoaxial (twisting around long axis), though this distinction does not predict outcomes 5
- Sigmoid distension ≥9 cm predicts increased recurrence risk 5
Caecal Volvulus
- Spiraled loops of the collapsed cecum creating a "whirl sign" in the twisted mesenteric vessels 2
- Low-attenuating fatty mesentery from the twisted bowel 2
- Rounded focal collection of air-distended bowel with haustral creases in the upper left quadrant 2
- Signs of intestinal malrotation may be present as a predisposing factor 3
- The caecum and ascending colon are displaced from their normal right lower quadrant position 3, 2
Location-Specific Patterns
Sigmoid volvulus demonstrates asymmetric gaseous abdominal distention with emptiness of the left iliac fossa, which is pathognomonic but challenging to detect clinically 1. On imaging, the massively dilated sigmoid occupies the central and upper abdomen 1.
Caecal volvulus shows the distended caecum displaced to abnormal positions - most commonly the left upper quadrant or epigastrium - with the right lower quadrant appearing relatively empty 3, 2.
Contrast Enema Findings (When Applicable)
- "Bird's beak sign" at the point of colonic torsion confirms sigmoid volvulus 1
- Water-soluble contrast is strongly preferred over barium 1
- Contraindicated when perforation is suspected 1
- This modality is less commonly used for caecal volvulus diagnosis 6
Signs of Complications on Imaging
Both conditions can show:
- Free air indicating perforation (best seen on chest radiograph or CT) 1
- Bowel wall thickening, pneumatosis, or lack of enhancement suggesting ischemia 1
- Intravenous contrast on CT facilitates diagnosis of colonic ischemia 1
Clinical Context for Interpretation
The radiological findings must be interpreted with clinical context: sigmoid volvulus typically affects elderly, institutionalized patients with chronic constipation 1, 4, while caecal volvulus more commonly affects younger females (age ≤60 years) 4. Sigmoid volvulus represents 75% of colonic volvulus cases, while caecal volvulus accounts for 22-30% 7, 6, 2.