Midgut volvulus

Midgut volvulus is a complication of malrotated bowelbowel malrotation. It may result in proximalwill often present as small bowel obstruction with resultant ischaemia ifbilious vomiting. If prompt treatment is not instigated, there is a risk of small bowel ischaemia.

Epidemiology

A midgutMidgut volvulus of malrotated bowel can potentially occur at any age, but in approximatelyabout 75% of cases occur within a month of birth ^4,6. Most of these are within the first week ³, with 90% occurring within 1 yearin the under ones 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 incauses progressive venous obstruction and, gradual onset of ischaemia, and eventual necrosis.

As this occurs, the abdomen becomes swollen and tender as fluid accumulates in the lumen of the bowel, and becomes tender. Eventually, in severe, untreated cases, peritonitis and shock become establishedcan result in severe morbidity and, sometimes, mortality.

Pathology

Midgut volvulus occurs as a complication of intestinal malrotation.

Associations

These include ⁸ Malrotation describes incomplete intestinal rotation that should occur during fetal life. Normal intestinal rotation results in:

• gastroschisis

  a duodenal loop that crosses the midline

• omphalocele

  the DJ flexure to the left of midline at the level of the pylorus

• diaphragmatic hernia

  central small bowel

• duodenal or jejunal atresia

  the caecum in the right iliac fossa

• peripheral large bowel

Radiographic features

Plain radiograph

Unfortunately, plain radiographsPlain radiograph findings are non-contributory appearing eithernonspecific. They may be normal early on, or having appearances ofshow developing bowel obstruction or evenas time progresses. Later, in untreated patients, they may show pneumoperitoneum later in the course of the diseasewhere obstructed, ischaemic bowel perforates.

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

Fluoroscopy

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 or 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 the position of the caecum in normal individuals being variable ³.

Ultrasound

Ultrasound findingsis helpful when volvulus is confidently identified. Findings in volvulus 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 the obstruction

  • thickened wall of small bowel distal to the 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

Treatment and prognosis

Urgent resuscitation and surgical repairintervention is required in confirmed or suspected midgut volvulus.

Surgically, the bowel is devolved to allow restoration of blood supply and resection of any non-viable loops is performed (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 (surgical fixation) of the duodenum and caecum may be performed although it is unclear if this is of benefit in preventing recurrence ⁶.  It

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, the prognosis is extremely good. Overall mortality of 3-9% is reported ⁶.  

Small bowel obstruction for adhesions is seen as 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:

• pyloric stenosis: vomiting will be non-bilious and projectile

• congenital obstruction

  • duodenal web

  • duodenal atresia

  • intestinal atresia

  • annular pancreas

• meconium ileus

• intussusception

• external compression of the dudenum

  • choledochal cyst

  • mesenteric duplication cyst

  • intramural duodenal haematoma

  • preduodenal portal vein

  • retroperitoneal tumour

  • superior mesenteric artery syndrome