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Midgut volvulus

midgut volvulus is a complication of malrotated bowel and results in a proximal bowel obstruction and ischaemia.

Epidemiology

A midgut volvulus of malrotated bowel can potentially occur at any age but in approximately 75% of cases is within a month of birth 4,6, most within the first week 3, and 90% within 1 year 6.

Clinical presentation

Typically the neonate is entirely normal for a period before suddenly presenting with bilious vomiting. If the volvulus does not spontaneously reduce, then the venous obstruction created by the superior mesenteric vein wrapped around the superior mesenteric artery results in venous obstruction and gradual onset of ischaemia and eventual necrosis. As this occurs, the abdomen becomes swollen as fluid accumulates in the lumen of the bowel, and becomes tender. Eventually peritonitis and shock become established.

Radiographic features

Plain film

Unfortunately plain films are non-contributory appearing either normal early on, or having appearances of a bowel obstruction or even pneumoperitoneum later in the course of the disease. 

Occasionally complete obstruction can lead to distension of the duodenal bulb and stomach leading to a double bubble sign 7.

Contrast study

A paediatric upper gastrointestinal contrast study is the examination of choice when the diagnosis is suspected. Not only is it able to identify the volvulus, but even in instances where spontaneous reduction has occurred, the underlying malrotation will be evident.

In the setting of volvulus findings include:

  • corkscrew sign
  • tapering of beaking of the bowel in complete obstruction 3
  • malrotated bowel configuration

Contrast enemas have also been used historically. The theory being that in malrotation the large bowel will also be malrotated. Unfortunately in 20-30% of cases the caecum is normally located. The converse is also true, with position of the caecum in normal individuals being variable 3.

Ultrasound

Ultrasound findings include 1-5:

  • clockwise whirlpool sign
  • abnormal superior mesenteric vessels:
    • inverted SMA/SMV relationship
    • solitary hyperdynamic pulsating SMA
    • truncated SMA
    • inapparent SMV
  • abnormal bowel:
    • dilated duodenum proximal to obstruction
    • thickened wall of small bowel distal to obstruction
    • dilated fluid-filled loops of small bowel
  • free intra-abdominal fluid
CT

CT is often carried out in older patients, in which presentation is non-specific. 

Findings include:

  • whirlpool sign of twisted mesentery
  • malrotated bowel configuration
  • inverted SMA/SMV relationship
  • bowel obstruction
  • free fluid / free gas in advanced cases
Associations 8

Treatment and prognosis

Urgent surgical repair (Ladd procedure) is required to prevent ischaemia or to resect infarcted bowel loops. If resection is performed stomas are usually created. Additionally the Ladd bands are divided and the mesenteric pedicle widened. In some instances pexy of the duodenum and caecum may be performed although it is unclear if this is of benefit in preventing recurrence 6.  It should be noted that normal anatomical positioning is not achieved; the duodenum and small bowel remain on the right, and the caecum and colon are on the left side of the abdomen 6

Prognosis is dependent on the state of the small bowel and presence of systemic shock. In cases where no ischaemia of the bowel is present, and the child is otherwise well, prognosis is extremely good. Overall a mortality of 3-9% is reported 6.  

Small bowel obstruction for adhesions is seen a distant complication in 5-10% of cases.

Differential diagnosis

Vomiting in infancy has numerous causes and needs to be distinguished from normal possetting. Differential of a proximal obstruction includes 3,6,7:

 

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