Volvulus on X‑ray

Written by the X-Ray Atlas editorial team from the sources listed below · Medical review pending · Updated 24 October 2026 · Level: Intermediate

A volvulus is a twist of a loop of bowel around its own mesentery. The twist obstructs the bowel at two points, creating a closed loop that fills with gas and fluid, and it can cut off the blood supply, leading to ischaemia, gangrene and perforation. In adults, the large bowel is most often affected, especially the sigmoid colon, followed by the caecum. The abdominal X-ray (AXR) is often strongly suggestive, because a twisted, hugely distended loop has a characteristic shape. Telling sigmoid from caecal volvulus matters, because they are treated differently. This page covers both, plus gastric volvulus, with the signs, the mimics and the next steps.

1. How to look

On a supine AXR, start with the systematic abdominal approach. Then, when you see a very large gas-filled loop, ask:

1. Where does the loop arise: from the pelvis, or from the right iliac fossa?
2. Which way does its apex point: towards the right upper quadrant or the left upper quadrant?
3. Does it have haustra, or is it featureless?
4. What is the rest of the bowel doing: is the colon dilated proximal to it, or is the small bowel dilated with a collapsed colon?
5. Is there free gas?

2. Sigmoid volvulus

The sigmoid colon twists on a long, redundant mesentery. It is more common in older people, people in long-term care, those with chronic constipation, and people with neurological or psychiatric conditions, many of whom take drugs that slow the bowel. Signs on the AXR:

• Coffee bean sign (bent inner tube sign): a massively dilated, inverted U-shaped loop, usually without haustra, arising from the pelvis. The two limbs of the loop lie side by side, and their adjoining walls form a dense central line, giving the coffee bean shape.
• The apex points towards the right upper quadrant, often lying under the right hemidiaphragm, and classically above the level of T10.
• Northern exposure sign: the apex of the loop lies higher than the transverse colon.
• Liver overlap sign: the dilated loop overlaps the lower border of the liver.
• Left flank overlap sign: the loop overlaps the descending colon on the left.
• Frimann-Dahl sign: three dense lines (the walls of the loop) converge towards the point of obstruction, low in the left pelvis.
• The colon proximal to the twist may be dilated as well, with LBO appearances. See large bowel obstruction.

3. Caecal volvulus

Caecal volvulus happens when an abnormally mobile caecum and ascending colon twist. It tends to affect younger patients than sigmoid volvulus. Signs on the AXR:

• A dilated caecum displaced out of the right iliac fossa into the mid or left upper abdomen, so the apex points towards the left upper quadrant.
• A kidney bean or comma shape, sometimes with haustral markings still visible.
• Often a single long air–fluid level on an erect or decubitus film.
• Dilated small bowel, because the obstruction is at the start of the colon, with a collapsed distal colon.
• An empty right iliac fossa where the caecum should be.

A related condition, caecal bascule, is folding of the caecum upwards rather than twisting. It produces a dilated caecum in the mid-abdomen and can look similar.

4. Sigmoid versus caecal: side by side

Feature	Sigmoid volvulus	Caecal volvulus
Arises from	Pelvis	Right iliac fossa (now empty)
Apex points to	Right upper quadrant	Left upper quadrant or mid-abdomen
Shape	Coffee bean, inverted U	Kidney bean, comma
Haustra	Usually absent	Sometimes preserved
Rest of bowel	Proximal colon dilated	Small bowel dilated, distal colon collapsed
Typical patient	Older, institutionalised, constipated	Younger adult
Usual first treatment	Endoscopic decompression (flexible sigmoidoscopy, flatus tube) if no ischaemia	Surgery

Overall, sigmoid volvulus is the more common of the two in UK practice; most series report it as the majority of colonic volvulus cases.

5. Gastric volvulus

The stomach can twist around its long axis (organoaxial) or its short axis (mesenteroaxial), often in association with a large hiatus or paraoesophageal hernia. Imaging may show:

• a massively distended stomach in the left upper quadrant or in the lower chest;
• a double air–fluid level on an erect film;
• an NG tube that cannot be passed into the stomach.

The classic clinical picture is Borchardt's triad: severe epigastric pain, retching without producing vomit, and inability to pass an NG tube. Acute gastric volvulus is a surgical emergency because of the risk of gastric ischaemia. A retrocardiac gas-filled structure on a chest X-ray may be the first clue. See mediastinum and hila.

6. Midgut volvulus in children

In infants and young children, twisting of the small bowel around the superior mesenteric vessels because of malrotation is a different condition, presenting typically with bilious vomiting. The AXR may be normal or non-specific, and a normal film does not exclude it. It is a surgical emergency; the usual test is an upper gastrointestinal contrast study, and urgent surgical referral should not wait for imaging when the child is unwell. See the paediatric abdominal X-ray.

7. Pitfalls and mimics

• Pseudo-obstruction and a very redundant, dilated sigmoid colon in chronic constipation can look like volvulus. CT helps when it is unclear.
• Marked dilatation of the transverse colon can be mistaken for a sigmoid loop. Trace where the loop arises.
• Confusing caecal volvulus with a dilated stomach: check the position of the gastric bubble and the NG tube.
• Missing perforation: look for free gas, including Rigler's sign. See pneumoperitoneum.
• The film does not show ischaemia. Clinical signs (constant pain, peritonism, sepsis) and CT findings decide the urgency of surgery.

8. Next steps

• CT confirms the diagnosis when the AXR is not conclusive, shows the twist (the "whirl" of mesenteric vessels) and looks for ischaemia and perforation.
• Sigmoid volvulus without signs of ischaemia or perforation is usually decompressed endoscopically, with a flatus tube left in place. Recurrence is common, and elective surgery may be considered afterwards.
• Caecal volvulus is usually treated surgically; endoscopic decompression is rarely successful.
• Early surgical review, intravenous fluids and correction of electrolytes in all cases.

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	Coffee bean versus kidney bean, which quadrant the apex points to, and why the treatment differs.
Nurse	Recognise abdominal distension in at-risk patients, such as older people in long-term care with constipation. Care of the flatus tube after decompression.
Junior doctor	Recognise the shape, request CT when unsure, and involve surgeons and endoscopists early.
Radiographer	Include the full abdomen up to the diaphragm, because the apex of a sigmoid loop often sits high under the right hemidiaphragm.
Advanced / FRCR	Caecal bascule, the named signs of sigmoid volvulus, gastric volvulus types and CT whirl signs.

Practise on abdominal X-rays →

References

1. Radiopaedia. Sigmoid volvulus. radiopaedia.org
2. Radiopaedia. Caecal volvulus. radiopaedia.org
3. Radiology Masterclass. Large bowel obstruction. radiologymasterclass.co.uk
4. Royal College of Radiologists. iRefer. irefer.org.uk

For education only. Not a substitute for a formal report, senior review or your local policy. Never use this page to make decisions about a real patient.