Pathophysiology and causes
Normally, between 4 and 12 weeks of intrauterine development, the intestine undergoes a complex 270-degree counterclockwise rotation. If this process is disrupted, malrotation occurs. By itself, it is not a disease, but it leads to a dangerous anatomical defect—shortening of the root of the small bowel mesentery.
This shortened root becomes the axis around which the midgut can twist, forming a volvulus (volvulus). As a result of the twist, the superior mesenteric vessels are compressed, arterial inflow and venous outflow are disrupted, which rapidly leads to ischemic necrosis of the intestinal wall. Without timely treatment, this condition has an extremely high mortality rate.
The pathology may be isolated, but is sometimes associated with other anomalies:
- Heterotaxy syndromes.
- Hirschsprung disease (Hirschsprung disease).
- Prune-belly syndrome (prune-belly syndrome).
- Cloacal exstrophy and intestinal neuronal dysplasia.
- Congenital diaphragmatic hernias, gastroschisis, and omphalocele (in these conditions, the intestine always exhibits malrotation, but volvulus after surgical correction is rare).
Clinical presentation
Manifestations depend on the patient's age and the degree of intestinal obstruction:
- Neonates (symptomatic): this is the most vulnerable group. Volvulus manifests in the first few days of life with bilious vomiting. The appearance of bile in vomitus is a critical signal indicating an obstruction distal to the ampulla of Vater.
- Older children: symptoms are often nonspecific. Periodic or chronic abdominal pain, diarrhea, vomiting, and failure to thrive may occur. Volvulus should be suspected in cases of recurrent pain accompanied by bilious vomiting.
- Adults: in this age group, malrotation and volvulus are extremely rare.
Plain radiography
A plain abdominal radiograph alone does not allow for a definitive diagnosis, as there are no specific findings for malrotation. The findings may be completely normal in incomplete obstruction or intermittent volvulus. However, the method is critical for assessing the severity of the condition:
- Tight volvulus (tight volvulus): complete duodenal obstruction is visible with gas distension of the stomach and the proximal duodenum.
- Classic presentation: partial obstruction with distension of the stomach, duodenum, and a small amount of gas in the distal segments. It may mimic the "double bubble" sign (double bubble) characteristic of duodenal atresia.
- Closed-loop pattern: an extremely unfavorable sign. Edematous loops with thickened walls and pneumatosis are visible, indicating small bowel necrosis.
- Gasless abdomen (gasless abdomen): a consequence of prolonged vomiting, closed-loop type obstruction (while bowel viability is maintained), or massive midgut necrosis.
Upper GI contrast study
If an infant has bilious vomiting and partial obstruction, contrast imaging is indicated (usually barium, but surgeons may prefer water-soluble contrast prior to urgent surgery). The main goal of the study is to precisely determine the position of the duodenojejunal flexure (DJF). Normally, on a supine radiograph, it is located to the left of the vertebral pedicle roots at the level of the duodenal bulb. In malrotation, the flexure is displaced inferiorly and to the right.
Key radiological signs of volvulus:
- Corkscrew sign (corkscrew pattern): spiral twisting of the duodenum and jejunum around the mesenteric vessels. This is an absolutely pathognomonic sign of midgut volvulus.
- Abrupt cut-off sign (abrupt cut-off): sudden cessation of the contrast column in the third part of the duodenum.
Technical nuance: the stomach should not be overfilled with contrast, otherwise it will obscure the DJF directly or due to rapid "flooding" of the duodenum. An alternative method is placing an enteral tube into the first part of the duodenum (D1) for targeted duodenography, which eliminates the overlapping stomach shadow.
To memorize the radiological appearance of volvulus on contrast imaging, use the wine bottle analogy: the "Corkscrew" (spiral course of the bowel around the vessels) leads to the "Cut-off" (sudden cessation of contrast) unless the "cork" (surgical treatment) is removed in time.
Class and exam questions
Does malrotation always lead to volvulus?
No, malrotation itself is not a pathology. However, it causes shortening of the mesenteric root, which creates the anatomical prerequisite (axis) for the twisting of intestinal loops.
What to do if a neonate develops bilious vomiting?
This is an absolute indication for emergency diagnostic imaging. If the plain radiograph shows complete obstruction or there are clinical signs of peritonitis, the infant is immediately transferred to the operating room without contrast studies.
Can a diagnosis be made based on plain radiography alone?
No, a plain radiograph lacks specific signs of volvulus and may even be normal. To confirm the diagnosis in partial obstruction, an upper GI contrast study is required.
What else to study on this topic
- Differential diagnosis of bilious and non-bilious vomiting in neonates
- Duodenal atresia and stenosis ("double bubble" sign)
- Meconium ileus and its complications (meconium peritonitis, pseudocyst)
- Congenital gastric obstruction and enteric duplication cysts
- Apple-peel syndrome in jejunoileal atresia
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Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.