bubble_chart Overview

Intestinal malrotation refers to the incomplete or abnormal rotational movement of the midgut during embryonic development, with the mesenteric artery as the axis, leading to variations in intestinal position and incomplete mesenteric attachment, which can cause intestinal obstruction or volvulus. It occurs in approximately 1 in 6,000 live births. Most cases present symptoms during the neonatal period, while a few manifest in infancy or childhood. The incidence is twice as high in males as in females.

bubble_chart Pathological Changes

If the normal rotation process of the intestinal tract is obstructed or abnormal at any stage, abnormal anatomical positions of the intestine can occur, leading to various types of intestinal obstruction and producing complex pathological conditions.

The pathological mechanisms of abnormal intestinal positions are: ① Obstruction or abnormal rotation of the intestinal tract during the embryonic stage, including an excessively large umbilical ring, non-rotation of the midgut, incomplete rotation, or reverse rotation; ② Hypoplasia of the intestinal tract; ③ The colonic mesentery is not attached, presenting as a dorsal common mesentery; ④ Due to developmental disorders of the intestinal tract or incomplete fixation of the mesentery, the proximal colon or small intestine loops continue to rotate, forming intestinal volvulus.

The types of abnormal intestinal rotation during the embryonic stage include:

(1) Non-rotation of the midgut: The midgut does not rotate when returning to the abdominal cavity, maintaining its original position. The small intestine and colon both hang from a common mesentery, with the root of the mesentery arranged sagittally in front of the spine, often accompanied by omphalocele and gastroschisis malformations.

(2) Incomplete intestinal rotation: The intestinal loop stops rotating after 90°. The small intestine hangs on the right side of the abdominal cavity, while the cecum and proximal colon are located on the left side, with the appendix in the lower left abdomen, which is a common rotational abnormality. The lower part of the duodenum does not cross the superior mesenteric artery but is located to the right of the mesentery root, with no duodenojejunal flexure. The terminal ileum enters the cecum from the right to the left. The ascending colon is in front of or to the left of the spine, and the duodenum, small intestine, and colon hang from a common free mesentery. The development of the colon itself positions the transverse colon horizontally, with the hepatic flexure of the proximal colon extending sharply to the right, and the duodenum and proximal colon are coiled.

(3) Abnormal intestinal rotation type I: The intestinal loop stops rotating after 180°. The lower part of the duodenum is behind the mesentery root, and the cecum and ascending colon are located at the midline of the abdomen, with sheet-like peritoneal adhesions or bands crossing the front of the second part of the duodenum and attaching to the right posterior abdominal wall. When the development of the proximal colon stalls, the cecum is on the right side of the spine in front of the duodenum, compressing the duodenum.

(4) Abnormal intestinal rotation type II: Such as reverse rotation or mixed rotation.

1. After rotating 90° counterclockwise, the midgut rotates 90°–180° clockwise, placing the descending part of the duodenum in front of the superior mesenteric artery.

2. The proximal colon migrates to the right, entirely or partially located in front of the duodenum and mesentery.

3. When the proximal colon and its mesentery shift to the right, the small intestine and mesenteric vessels are enveloped within the colonic mesentery, forming a mesocolic hernia. The ascending colon mesentery constitutes the hernia sac wall, and the small intestine inside the sac can become obstructed.

4. After rotating 180° clockwise, the transverse colon runs behind the peritoneum, while the small intestine and ascending colon are in normal positions. The transverse colon crosses behind, and the lower part of the duodenum is located in front. If the midgut continues to rotate 180° clockwise, intestinal volvulus occurs with the mesentery root as the axis, the cecum shifts to the left, and the duodenum is located on the right.

(5) Common mesentery: The ascending colon mesentery not attaching to the posterior abdominal wall is a combined abnormality of midgut malrotation, or it can be an isolated abnormality in normal intestinal rotation. In this case, the lower part of the duodenum is behind the superior mesenteric artery, and the duodenal flexure is on the left side of the abdomen. With a common mesentery, the mesentery root forms a slender stalk extending from below the pancreas and fanning out. The ascending colon is close to the right abdominal wall but without adhesions. If the ascending colon mesentery partially adheres to the posterior abdominal wall, the cecum and adjacent ascending colon remain free.

Associated malformations: Occur in 30–62% of cases. Half are duodenal atresia, with others including jejunal atresia, congenital megacolon, mesenteric cysts, etc.

bubble_chart Clinical Manifestations

It leads to three clinical issues: ① intestinal volvulus; ② duodenal obstruction, acute and chronic; ③ internal hernia. The age of onset varies, with newborns being the most common, accounting for about 80% of cases. Some cases present symptoms during childhood or adulthood, while a few cases show no clinical symptoms and are incidentally discovered during X-ray examinations or other surgeries.

After birth, infants pass normal meconium, and symptoms typically appear around the 3rd to 5th day, mainly manifesting as vomiting and other symptoms of high intestinal obstruction. Intermittent vomiting, with bile in the vomitus, no abdominal distension, and no positive signs. In cases of complete obstruction, vomiting becomes persistent and frequent, accompanied by dehydration, emaciation, and constipation. If complicated by intestinal volvulus, the symptoms become more severe, with coffee-ground-like vomitus, bloody stools, fever, and shock, along with abdominal distension and peritoneal irritation signs. Early diagnosis and prompt treatment are essential.

In infants and young children, cases often present as chronic duodenal obstruction, with intermittent symptoms that can often be relieved. Manifestations include emaciation and poor nutritional development. Acute intestinal obstruction may also occur, requiring emergency treatment.

Approximately 20% of cases are accompanied by hyperbilirubinemia, the cause of which remains unclear. It may be due to the compression of the common bile duct by the dilated stomach and duodenum. Compression of the portal vein and mesenteric veins may reduce blood flow, leading to compensatory increases in hepatic arterial blood flow, causing untreated indirect bilirubin to re-enter circulation. Additionally, reduced portal vein blood flow may result in hepatic hypoxia, affecting the formation of enzyme systems.

bubble_chart Diagnosis

In any newborn presenting with symptoms of high intestinal obstruction, where the vomitus contains a large amount of bile, and who has previously passed normal meconium, the diagnosis of intestinal malrotation should be considered and can be confirmed by X-ray examination. An abdominal plain film may show dilation of the stomach and duodenum with fluid levels, while the small intestine is only minimally filled with gas. A barium enema serves as the primary diagnostic tool, verifying the position of the cecum; if the cecum is located in the upper abdomen or left abdomen, the diagnosis is confirmed. However, a mobile cecum or filling of the intestinal lumen with barium may cause the cecum to shift downward, so a normal cecal position does not rule out intestinal malrotation. When malrotation, duodenal atresia or stenosis, and annular pancreas all present with high intestinal obstruction and differentiation is difficult, excessive examinations should be avoided, and early surgical exploration is warranted.

In older infants and children with incomplete duodenal obstruction, a small amount of diluted barium or iodized oil can be swallowed for examination. This may reveal contrast retention in the duodenum, with only a small amount entering the jejunum, and occasionally, the duodenal-jejunal loop may appear vertically oriented instead of following the normal curved path. If complex intestinal patterns are observed, this suggests the presence of midgut volvulus.

bubble_chart Treatment Measures

Asymptomatic individuals should not undergo surgery and should be observed. Symptoms of obstruction or acute abdominal pain are indications for surgery, and early surgical intervention is required. Intestinal bleeding or signs of peritonitis indicate torsion and necessitate emergency treatment.

A transverse abdominal incision is made during surgery to fully expose the intestines. The surgeon must have a thorough understanding of such malformations to correctly interpret the abnormal findings during the procedure and provide appropriate treatment. Otherwise, improper handling may occur, leading to persistent symptoms. When assessing the condition of the intestines, attention should be paid to the relationship between the lower duodenum and the root of the mesentery, as well as the local anatomical position of the proximal colon. Often, the entire intestine needs to be exteriorized from the abdominal cavity. Only after untwisting the torsioned intestine in a clockwise direction can the type of intestinal malrotation be identified.

If the intestinal position is normal but there is a common mesentery, the cecum should be fixed from the ascending colon to the right lateral parietal peritoneum. To prevent abnormal mobility of the structure and avoid obstruction caused by the small intestine becoming trapped between the colonic mesentery and the posterior parietal peritoneum, the ascending mesocolon can be obliquely fixed to the dorsal parietal peritoneum from the ileocecal region to the duodenojejunal flexure.

For type I and type II intestinal malrotation, the membranous bands and adhesions should be released, the duodenum thoroughly dissected, the cecum freed, and the torsioned intestine reduced. The duodenum should be positioned along the right rectus abdominis, the small intestine placed on the right side of the abdominal cavity, and the cecum and colon placed on the left side (Ladd's procedure). The appendix is routinely removed to prevent future misdiagnosis.

In cases of retropositioned transverse colon, often due to reverse rotation, reduction requires rotating the torsioned intestine 360° counterclockwise. This moves the retroperitoneal transverse colon anterior to the root of the mesentery. The cecum and ascending colon are then fixed to the right parietal peritoneum, and the lower duodenum anterior to the mesenteric vessels is shifted to the right side of the abdomen to prevent compression. This alleviates mesenteric venous stasis caused by reverse rotation, restoring normal flow.

bubble_chart Prognosis

The follow-up results confirmed that the surgical outcome was favorable. Although the small intestine mesentery remains free and theoretically carries a risk of recurrent volvulus, clinical experience has shown that recurrence is rare. However, intermittent abdominal pain may persist, along with persistent digestive and absorption disorders, leading to anemia and low plasma protein levels. The extent of nutritional absorption impairment after resection of necrotic bowel depends on the length and function of the remaining intestine. Most fatal cases are associated with other congenital anomalies.