Intestinal Malrotation

What happens in malrotation

Between about the 4th and 12th weeks of pregnancy, the developing intestine grows outside the abdomen, then returns and rotates 270 degrees counterclockwise before fixing in place. Normally, the small intestine ends up anchored diagonally across the back of the abdomen on a broad base, and the colon wraps around it.

In malrotation, this rotation and fixation are incomplete:

• the small bowel lies mostly on the right and the colon on the left
• the bowel hangs on a narrow stalk of blood vessels (the mesentery), which can twist
• abnormal bands of tissue (Ladd bands) can cross and compress the duodenum

Midgut volvulus

When the bowel twists around its narrow stalk, it blocks the intestine and cuts off blood flow to most of the small bowel and part of the colon. Within hours, the bowel can die. That is why bilious vomiting in a baby is treated as malrotation with volvulus until proven otherwise. See malrotation with volvulus.

Symptoms

In newborns and infants

Most symptomatic cases appear in the first month:

• green or yellow-green vomiting (bile), sudden onset
• irritability, drawing up legs, crying
• a swollen or tender abdomen (sometimes the belly looks normal early on)
• blood in the stool, a late and serious sign
• poor feeding, dehydration, lethargy and shock if untreated

In older children and adults

Malrotation can cause intermittent symptoms or be discovered by chance:

• recurrent abdominal pain and vomiting
• early fullness, poor weight gain or failure to thrive
• chronic diarrhea or malabsorption
• sudden acute volvulus at any age

Associated conditions

Malrotation is more common with:

• congenital diaphragmatic hernia, gastroschisis and omphalocele
• heterotaxy syndromes (abnormal arrangement of organs)
• duodenal atresia and some heart defects
• other bowel abnormalities such as Hirschsprung disease

Diagnosis

• Upper GI contrast study: the child drinks or is given contrast through a tube while X-rays track it. Normally, the duodenum crosses to the left of the spine; in malrotation, it stays on the right, and with volvulus shows a "corkscrew" pattern. This is the standard test.
• Ultrasound: can show reversal of the normal positions of the main intestinal artery and vein, or a "whirlpool" sign of twisting.
• Abdominal X-ray: may be normal early, or show obstruction.
• CT scan: often used in older children and adults.

Other causes of vomiting in infants include pyloric stenosis (non-green, projectile vomiting at 2 to 8 weeks) and intussusception, but green vomit points to a blockage beyond the stomach.

Treatment

The Ladd procedure

Surgery, open or laparoscopic, involves:

1. untwisting the bowel counterclockwise if volvulus is present
2. dividing the Ladd bands that compress the duodenum
3. widening the base of the mesentery to reduce the risk of future twisting
4. placing the small bowel on the right and the colon on the left
5. usually removing the appendix, because its position becomes abnormal

Any dead bowel is removed. If viability is uncertain, a "second look" operation 24 to 48 hours later may be done.

Incidental malrotation

When malrotation is found without symptoms, many surgeons recommend elective surgery in children because of the lifelong risk of volvulus. In adults, the decision is individualized.

Complications and outlook

Children treated before the bowel is damaged usually recover fully and grow normally. Complications can include:

• short bowel syndrome if a large length of bowel is lost, requiring specialized nutrition
• adhesions causing later bowel obstruction
• recurrent volvulus (uncommon after a Ladd procedure)
• ongoing feeding or motility problems in some children

Frequently asked questions

What is intestinal malrotation?

Intestinal malrotation is a birth defect in which the intestines do not rotate and fix in their normal position during fetal development. This leaves the bowel at risk of twisting (volvulus) and of being blocked by abnormal bands of tissue.

Why is green vomit in a baby an emergency?

Green or yellow-green vomit contains bile, which means a blockage below the stomach. In a baby, malrotation with volvulus must be ruled out immediately because twisted bowel can die within hours. Go to the emergency department right away.

How is malrotation treated?

It is treated with surgery called the Ladd procedure, which untwists the bowel if needed, divides abnormal bands, widens the base of the bowel's attachment and usually removes the appendix. Volvulus requires emergency surgery.

Can adults have intestinal malrotation?

Yes. Some people reach adulthood without symptoms, and malrotation is found on a scan, or causes recurrent pain, vomiting or sudden volvulus. Treatment decisions depend on symptoms and surgical opinion.