Radiography
Findings
Abdominal radiographs are frequently performed in children with abdominal symptoms. In cases of simple malrotation, radiographs may appear normal.
In midgut volvulus, the classic radiographic finding is a partial duodenal obstruction (dilation of both the stomach and proximal duodenum, with a small amount of distal bowel gas). Complete obstruction of the duodenum may also be found. Less frequent, but more ominous, signs are a gasless abdomen, ileus, or a distal small bowel obstruction with multiple dilated loops and air-fluid levels. A normal abdominal film does not exclude malrotation.
An upper GI series is the preferred diagnostic test for malrotation with midgut volvulus and must be performed, unless a delay in surgical treatment will compromise outcome (as in the case of a moribund child). The upper GI series is performed with barium administered either orally or through a nasogastric tube. The normal DJJ lies to the left of the left-sided spinal pedicle at the level of the duodenal bulb on a true frontal view. The duodenal C-sweep courses posteriorly, inferiorly, anteriorly, and then superiorly.
The findings of a malrotation on upper GI series include the following:
- The DJJ is displaced downward and to the right on frontal view.
- The duodenum has an abnormal course on lateral view.
- Abnormal positioning of the jejunum (lying on right side of abdomen) should alert the physician to the possibility of a malrotation, but this finding should not be relied upon to either make or exclude the diagnosis.
In malrotation with midgut volvulus, the findings also include the following:
- A dilated, fluid-filled duodenum
- A proximal small bowel obstruction
- A "corkscrew" pattern (proximal jejunum spiraling downward in the right- or mid-upper abdomen in midgut volvulus, which is rare) (see Image 6)
- Mural edema and thick folds
Degree of Confidence
In malrotation without midgut volvulus, the degree of confidence on plain radiographs is low. Radiographs are rarely normal in malrotation with midgut volvulus, increasing the degree of confidence in this clinical scenario.
An upper GI series provides a high degree of confidence in the diagnosis of malrotation with midgut volvulus.
False Positives/Negatives
Radiographic false negatives: Normal radiographs are common with malrotation.
Radiographic false positives:
- Findings in midgut volvulus are nonspecific and can be seen in other conditions that may cause ileus or ischemia, such as acute pyelonephritis, appendicitis, and necrotizing enterocolitis.
- Duodenal obstruction, seen in midgut volvulus and malrotation, is also seen with duodenal stenosis, duodenal web, annular pancreas, preduodenal portal vein, and duodenal atresia.
- Upper GI series sensitivity is 85-95%, with a higher specificity (false positives are rare). Although a DJJ low and to the right of normal is a sensitive indicator of malrotation, this finding can also occur secondary to distended bowel, masses, and splenomegaly, especially in children younger than 4 years, whose mesenteric attachments are not as well fixed as they are in later years. Scoliosis makes it difficult to rule out malrotation because the normal bony landmarks are lost.
Computed Tomography
Findings
See Ultrasound.
Magnetic Resonance Imaging
Findings
Diagnosis of malrotation with midgut volvulus on fetal magnetic resonance imaging (MRI) has been reported.1 In practice, this is a difficult diagnosis to make, and MRI is not recommended in infants suspected of having malrotation with midgut volvulus.
Ultrasonography
Findings
Ultrasonography and CT may suggest the diagnosis of malrotation; however, their sensitivities and specificities are low compared to those of an upper GI series. An upper GI examination is mandatory to confirm the diagnosis, if it is suspected on CT or ultrasonography. If the superior mesenteric vein (SMV) lies to the left of or posterior to the SMA, malrotation is suggested; however, normal vascular positioning (the SMV being slightly ventral and to the right of SMA) can be seen in approximately 30% of patients with malrotation.The "whirlpool sign" on color Doppler ultrasonography shows mesentery and flow within the SMV wrapping around the SMA (in a clockwise direction), suggesting, but not entirely specific for, malrotation with midgut volvulus (see Image 8). A dilated, fluid-filled duodenum is frequently seen in patients who have obstruction without volvulus.
Degree of Confidence
The moderate-to-low degree of confidence associated with ultrasonography and CT necessitates an upper GI series to confirm the diagnosis.
False Positives/Negatives
Ultrasonography and CT have false-negative rates of approximately 30% and false-positive rates as high as 20%.
Nuclear Imaging
Findings
Nuclear medicine techniques do not provide sufficient resolution to confidently diagnose midgut volvulus; therefore, nuclear medicine is not a recommended imaging modality for the diagnosis this condition.
Angiography
Findings
Angiographic abnormalities with chronic volvulus have been well described, and they include proximal occlusion of the SMA, a "barber-pole sign" (whirling SMA and its branches), extensive collateral vessels, and thickening of the small bowel folds.
Angiography is not used to diagnose acute midgut volvulus.
Degree of Confidence
The degree of confidence is high, but this examination is rarely indicated.
False Positives/Negatives
Few false positives or false negatives are seen with angiography.
More on Midgut Volvulus |
| Overview: Midgut Volvulus |
 Imaging: Midgut Volvulus |
| Follow-up: Midgut Volvulus |
| Multimedia: Midgut Volvulus |
| References |
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References
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Further Reading
Keywords
malrotation with midgut volvulus, nonrotation, reverse rotation, malrotation
