Volvulus in Intestinal Malrotation: Whirlpool Sign and SMA/SMV Inversion on Ultrasound
Clinical Context
Assessment of the orientation of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV) should be documented to exclude midgut malrotation, particularly when findings are negative for hypertrophic pyloric stenosis (HPS) (Hagen-Ansert, 2023).
Normal SMA/SMV Relationship
Normally, the spatial relationship of the SMA and SMV is evaluated in the transverse plane of the abdomen at the level of the pancreas. Demonstration of normal vessel orientation allows exclusion of anomalies associated with midgut malrotation (Hagen-Ansert, 2023).
Signs of Malrotation and Volvulus
Positive findings in midgut malrotation may manifest as:
— inability to demonstrate normal SMA/SMV relationship (vessel inversion);
— whirlpool sign of these vessels, reflecting volvulus (Hagen-Ansert, 2023).
Scanning Planes for Vessel Assessment
| Plane | Anatomy |
|---|---|
| Transverse | Pancreatic head / IVC / SMV |
| Transverse | Pancreatic body and tail / SMV / SMA |
| Longitudinal | Body and tail / aorta |
IVC — inferior vena cava; SMA — superior mesenteric artery; SMV — superior mesenteric vein (Hagen-Ansert, 2023).
Specific quantitative threshold criteria (e.g., angles or degree of rotation) are not provided in the source fragments [clarification needed].
Frequently asked questions
In which plane should the SMA/SMV relationship be assessed?
In the transverse plane of the abdomen at the level of the pancreas (Hagen-Ansert, 2023).
What is considered a positive sign of malrotation on ultrasound?
Inability to demonstrate normal vessel relationship or whirlpool sign of the SMA/SMV (Hagen-Ansert, 2023).
When is assessment of SMA/SMV particularly important?
When findings are negative for hypertrophic pyloric stenosis (HPS), to exclude midgut malrotation (Hagen-Ansert, 2023).
What does normal SMA/SMV relationship indicate?
Demonstration of normal vessel orientation excludes anomalies associated with midgut malrotation (Hagen-Ansert, 2023).