Intestinal Volvulus 

Intestinal volvulus is defined as a complete twisting of a loop of intestine around its mesenteric attachment site. It is related to but not precisely synonymous with malrotation, a more general term used when the normal process of rotation and fixation of the midgut goes awry. Malrotation may lead to 2 critical complications: mechanical obstruction of the proximal intestine and twisting of the intestines with subsequent ischemia (with or without necrosis) of part or all of the midgut.

Volvulus can occur at various sites in the gastrointestinal (GI) tract, including the stomach, small intestine, cecum, transverse colon,^[1] and sigmoid colon. Midgut volvulus refers to twisting of the entire midgut around the axis of the superior mesenteric artery (SMA). Patients with intestinal malrotation are at risk for developing a midgut volvulus. This article primarily focuses on midgut volvulus because it is the most common type of volvulus and it can have devastating consequences if not promptly recognized. Midgut volvulus secondary to intestinal malrotation is more common in infants and children, but it can occur in persons of all ages. Sigmoid volvulus, more common in elderly persons, is also briefly discussed.

Volvulus involving the GI tract can cause severe clinical problems; the most feared complication is ischemia and necrosis of the entire midgut, which can be fatal.

In 1832, Reid described a malpositioned cecum, found in the left upper quadrant, in 2 autopsies.^[2] Mall first described the process of normal intestinal rotation during the embryologic period in 1898.^[3] The first clear description of anomalies of intestinal rotation and fixation (the clinical manifestations of which correlated with the observations of the embryologist His) was published by Dott in 1923.^[4]

In 1932, Ladd, the father of pediatric surgery in North America, published his landmark paper on congenital duodenal obstruction and presented a surgical correction for the anomaly described as congenital intestinal malrotation.^[5] This technique has been adopted as the standard therapy worldwide and is still the basis of surgical treatment today. Minor modifications have been reported, including the use of minimally invasive surgical techniques. The understanding of GI embryology heavily contributed to the development of a successful surgical treatment for this condition. The anatomical understanding of malrotation and volvulus is considered vital for the early recognition of the clinical presentations and implications of this abnormality.

Laboratory findings are nonspecific. Imaging studies are an integral part of the diagnostic process for a patient suspected of having malrotation or other GI obstruction. Confirmation and definitive diagnosis are accomplished more easily with an upper GI contrast series, but other imaging modalities can also be used (as will be discussed here).

The management of abnormalities of rotation and volvulus is well established. Treatment of midgut volvulus secondary to congenital intestinal malrotation is surgical; no other effective treatment is available. High priority must be placed on early recognition of midgut volvulus before serious complications develop. The surgical techniques used to treat this condition are discussed in this article.

The midgut is that portion of the intestine supplied by the SMA. It includes the distal duodenum, all of the jejunum and ileum, and the colon as far as the mid transverse. Normally, the duodenum courses posterior to the SMA and the superior mesenteric vein (SMV), and the transverse colon lies anterior to these vessels.

The bowel is relatively fixed at several points: the duodenum (including the duodenojejunal [DJ] junction), the ascending colon, the splenic flexure, and part of the descending colon. If the normal process of rotation and fixation fail to occur, the midgut may not be normally arranged and lacks physiologic points of fixation, and thus may be subject to twisting or volvulus.

Embryology of GI tract

A good understanding of the embryologic development of the GI tract is central to the understanding of malrotation and volvulus. At 4 weeks’ gestation, the GI system is a short, straight tube centrally located in the abdomen. During the fifth week, the first stage of rotation begins and lasts until the tenth week. As this tube grows and lengthens, it must leave the domains of the fetal abdominal cavity and thus herniates into the area of the umbilical cord, carrying its mesentery with its blood supply (ie, the SMA) as a central axis; it is in line with the omphalomesenteric duct, which is located at the apex of the herniation.

The prearterial segment includes the developing duodenum, the jejunum, and much of the ileum, whereas the postarterial segment becomes the terminal ileum, the cecum, the ascending colon, and part of the transverse colon.

While in this position (partially outside the fetal abdomen), the developing midgut begins to rotate. The DJ loop is first pushed inferiorly and to the right, possibly by the developing liver. Rotation is in a counterclockwise direction and continues in this fashion. This completes the first 90° of rotation. The cecocolic loop follows, moving to the left of the artery. The DJ loop then completes a second 90° of rotation, coming to rest inferior to the SMA.

The second stage of rotation occurs at 10-12 weeks’ gestation and involves the return of the intestine to the fetal abdominal cavity. Upon the return of the prearterial segment, the DJ loop completes another 90° of rotation for a total of 270°, coming to rest to the left of the SMA. The cecocolic loop also completes another 90° of rotation, coming to rest superior and anterior to the SMA.

The third and final phase of rotation occurs after 12 weeks’ gestation. The cecum completes its final descent to the right lower quadrant, accomplishing another 90° of rotation for a total of 270°. Once this descent is completed, the intestine becomes fixed to the posterior abdominal wall. The DJ junction is fixed to the left of the aorta, anterior to the left renal vein at the ligament of Treitz, and the cecum forms attachments to the right iliac fossa. These 2 points of attachment leave the mesentery and its blood supply broad-based and fixed. At this point, the GI tract has returned to the peritoneal cavity and the abdominal wall of the fetus has completely formed and closed at the level of the umbilicus.

Arrest of development at any stage not only changes the anatomic placement of organs but, perhaps most important, narrows the mesenteric base and impairs fixation, leaving the bowel at high risk for volvulus.

Rotational abnormalities

The common rotational abnormalities may be broadly grouped according to the stage at which they occur, as follows:

• Arrest in the first phase leaves the bowel herniated into the umbilical cord region, covered by a membrane, creating the so-called omphalocele; this is often accompanied by other congenital abnormalities (eg, cardiac and urogenital defects)
• Arrest in the second phase may result in nonrotation, incomplete rotation, hyperrotation, or reversed rotation; gastroschisis and diaphragmatic hernias seem to potentially also occur during this period. mesocolic paraduodenal hernias also occur during the late second phase and early third phase
• Arrest in the third phase results in a mobile cecum, an unattached duodenum, or an unattached small bowel mesentery, which allows cecal volvulus and internal hernias

It is important to note that intestinal malrotation may occur as an isolated event or in association with other types of congenital anomalies as listed above.

Nonrotation is the most common abnormality and results from failure of normal counterclockwise rotation around the SMA. Rotation may be completely absent or arrested at 90°. The small intestine remains entirely to the right of the artery, with the cecum at or near the midline and the colon in the left abdomen. This variant of malrotation is usually considered benign, given the fact that it may not cause any symptoms unless a volvulus develops.

In nonrotation, the proximal jejunum and colon pass very closely to the SMA, leaving a narrow pedicle as the base of the mesentery. This is sometimes called the “bell-clapper” or the omega configuration and leaves the midgut highly susceptible to volvulus and infarction. In addition, the peritoneal attachments of the cecum pass anterior and lateral to the duodenum, which may lead to some degree of extrinsic duodenal obstruction (a common cause of intermittent bilious vomiting).

Incomplete rotation is the next most common rotational abnormality, involving arrest of rotation at or near 180°. It is the most important form of malrotation. In this condition, midgut rotation is incomplete, the DJ loop remains to the right of the SMA, and the ileocecal loop comes to lie in the right upper quadrant, anterior to the SMA and closely related to the duodenum.

With incomplete rotation, the entire midgut is attached by a very narrow pedicle, consisting mostly of the SMA and the SMV. Twisting or volvulus of this pedicle may occur, leading to ischemia and mechanical obstruction of the intestine, which may lead to intestinal necrosis (see the image below). The ischemia begins with venous congestion, which progresses to arterial occlusion, and, finally, bowel necrosis.

As previously described, abnormal cecal peritoneal bands that cross over the duodenum in the right upper quadrant may be found in cases of malrotation. These abnormal cecal attachments are called Ladd bands. In both nonrotation and incomplete rotation, cecal bands may cause obstruction and ischemia before birth, leading to congenital duodenal atresia or stenosis. Therefore, the patency of the duodenum should be checked routinely during corrective surgery. In addition, intermittent antenatal volvulus may cause varying degrees of ischemia, leading to atresia or duplication of parts of the jejunum and ileum. In many cases, the abnormal Ladd bands cause only partial and intermittent obstruction, which can manifest as intermittent episodes of bilious vomiting and/or feeding intolerance.

Mixed rotational abnormalities are more uncommon and varied. Hyperrotation may narrow the SMA pedicle or lead to a confusing clinical picture in appendicitis. Failure of descent of the cecum may be inconsequential or may lead to cecal volvulus. Reversed rotation results in a 90° clockwise rotation, leaving the transverse colon behind the SMA and the duodenum anterior to the artery. In this case, the transverse colon may herniate into a mesocolic pocket or become obstructed by the SMA (also described as an internal hernia).

Mesocolic paraduodenal hernias occur with failure of fixation to the posterior abdominal wall. Spaces remain between the mesentery and the wall, allowing possible sequestration and strangulation of bowel segments. This occurs more often on the left and is associated with nonrotation. Right-side hernia is associated with congenital short bowel.

Volvulus

Volvulus of the midgut may result in several manifestations, depending on the degree of twisting. Venous and lymphatic obstructions occur first because of lower intravascular pressures. Vascular congestion leads to bowel edema and possible oozing of blood, potentially causing GI bleeding. Lymphatic congestion causes the formation of a mesenteric cyst and/or chylous ascites. It is not uncommon to find chylous fluid in the peritoneal cavity and enlarged lymph nodes at the time of corrective surgery for malrotation and volvulus.

If volvulus is intermittent, children may have chronic malabsorption from congestion and edema or intermittent bouts of symptoms, usually vomiting and possibly alternating diarrhea and constipation. Arterial compromise is seen when the twisting is significant enough to occlude venous and arterial vessels. This represents an acute and dangerous event. Sequelae include (in order of less to more severe) ischemia, mucosal necrosis, intramural air formation, bacterial translocation, gram-negative sepsis, full-thickness intestinal wall necrosis, perforation, peritonitis, and death.

Other congenital abnormalities

Malrotation is often associated with other congenital abnormalities, and, in some regions, as many as 62% of cases are associated with these abnormalities. This is important for several reasons.

First, some abnormalities (eg, polysplenia, asplenia, and congenital abdominal wall defects) are commonly associated with malrotation, and their presence should automatically lead to an investigation for malrotation. Patients with congenital wall defects, by definition, have some degree of malrotation, which should be evaluated during correction of the defect. Rotational anomalies in conjunction with dextroisomerism or levoisomerism should point to possible polysplenia or an asplenia syndrome. These syndromes have devastating effects on outcomes, especially asplenia.

Second, and perhaps most important, mortality related to malrotation and its correction is strongly correlated with the presence or absence of other congenital abnormalities. Serious anomalies may raise the risk of mortality 22 times. Physicians treating patients with malrotation must be aware of the possibility of other associated congenital abnormalities.

Developmental abnormalities such as gastroschisis, omphalocele, and congenital diaphragmatic hernia are associated with displacement of the abdominal contents outside the domain of the abdominal cavity. Since such developmental abnormalities occur at the time of fetal intestinal growth and rotation, they typically result in intestinal malrotation. Malrotation has also been described in also association with duodenal atresia, Meckel diverticulum, intussusception, small bowel atresia, prune belly syndrome, gastric volvulus, persistent cloaca, Hirschsprung disease, and extrahepatic biliary anomalies.

Specific causes of malrotation are unknown, although repeated associations have been made with congenital syndromes such as Down syndrome and the VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association of anomalies. Because malrotation is an embryologic development abnormality, it may be assumed that any interference during critical periods of fetal development can lead to malrotation.

Associated anomalies include the following:

• Trisomy 21
• Congenital heart disease
• Imperforate anus
• Ileal and jejunal atresia or duplication
• Omphalocele
• Duodenal atresia and stenosis
• Diaphragmatic hernia
• Meckel diverticulum
• VACTERL association
• Trisomy 13, trisomy 18
• Esophageal atresia
• Situs inversus and asplenia (may be associated with biliary atresia)
• Kidney abnormalities
• Agenesis of corpus callosum
• Pyloric stenosis
• Annular pancreas
• Erythroblastosis
• Intussusception
• Cystic fibrosis
• Meconium ileus
• Hirschsprung disease
• Duodenal web
• Biliary atresia

United States statistics

Malrotation is estimated to occur in 1 per 500 live births. Autopsy studies have reported a 0.2-1% incidence of malrotation in the total population; however, clinical discovery is achieved in only 1 per 600 live births. Increasingly, many cases are diagnosed at the time of laparotomy for other GI anomalies.

A mobile cecum or a high cecum (found in the right upper quadrant) may be considered a minor rotational abnormality, and it should not be the cause of any major medical problems. It has been recorded in 6-16% of the total population. Its incidence is slightly higher in the immature infant abdomen and may confuse the diagnosis of true malrotation.

International statistics

Overall, the incidence of volvulus internationally is similar to the incidence in the United States. Sigmoid volvulus in adult patients is more common in developing nations than in the United States, probably because of dietary differences in terms of fiber. Chagas disease in Brazil may account for a significant proportion of cases in that country in children and adults.

Age-related demographics

Of those in whom midgut volvulus occurs, 68-71% are neonates. Most cases occur by age 2 months, but as many as 41% of cases occur at an older age. Again, as previously mentioned, sigmoid volvulus is more common in elderly persons.

Symptomatic malrotation is much more common in younger children: children younger than 1 year account for 75-90% of cases, with 50-64% of cases occurring in infants younger than 1 month and 25-40% of cases occurring in the first week of life.

Sex-related demographics

Overall, no significant sex predilection has been established. However, midgut volvulus predominates in male infants. During the first week of life, the ratio of male-to-female presentation is 2:1. In the 25% of patients diagnosed with this condition after age 1 year, the male-to-female ratio equalizes, creating an overall 3:2 male-to-female ratio. Reasons for the slight male predominance are largely unknown.

Race-related demographics

No known racial difference has been reported.

The prognosis of midgut volvulus depends on prompt recognition before bowel necrosis occurs. In general, rapid diagnosis and immediate intervention for correction improve overall prognosis in all age groups. Younger children are at higher risk and require more aggressive support and treatment. Patients with other congenital defects have a poorer prognosis, depending on the severity of the abnormality.

The morbidity and mortality of malrotation and volvulus have decreased significantly since the advent of surgical correction. Early mortality figures ranged from 23% to 33%, mostly resulting from the sequelae of major bowel resection with bowel dysfunction and malnutrition. With the development of total parenteral nutrition and improved nutritional support, survival has increased. Current mortality figures range from about 3% to 9% overall.

In addition, improved understanding of the pathophysiology and the associated anomalies has allowed more prompt diagnosis. Clinical awareness of the association of malrotation with other anomalies and increased sensitivity to the importance of minor symptoms (eg, bilious vomiting) has led to improved diagnosis, allowing for correction of malrotation before life-threatening volvulus occurs. The significance of rapid diagnosis is evident in the high mortality (≤33%) still associated with diagnostic delay, especially in very young persons.

Messineo et al determined that the most important factors influencing mortality were the presence of necrotic bowel, associated abnormalities, and younger age.^[6] Risk of mortality increases 25 times in the presence of bowel necrosis and is influenced heavily by the length of viable bowel. The investigators found that the survival rate was maintained above 93% with 10%, 25%, and 50% of the bowel necrosed but that it fell to 35% with the loss of 75% of the length of the small bowel.

Messineo et al also found that the presence of other serious abnormalities increased the risk of mortality by a factor of 22. Given the high association of malrotation with other congenital anomalies, this risk factor heavily affects mortality figures. In addition, the authors determined that patients who died after surgery had a significantly lower median age (4 days versus 30 days).

The most common cause of death in patients who develop a volvulus is sepsis. Other noted causes are pneumonia, intracranial hemorrhage, short-bowel syndrome, malnutrition, renal failure or hepatic failure, continued small bowel obstruction, and other life-threatening anomalies.

Causes of long-term postoperative morbidity include adhesive bowel obstruction, short-bowel syndrome, and recurrent volvulus. Adhesive obstruction has been noted in 1-10% of these patients postoperatively and can contribute to renewed symptoms of partial to complete obstruction.

Short-bowel syndrome may occur after resection of a significant length of necrotic bowel. Children with malrotation and volvulus comprise 18% of the population of patients with short-bowel syndrome, which can result in chronic learning and psychomotor disabilities as well as the obvious risk of malnutrition.

Recurrent volvulus can occur in patients with intestinal malrotation that was successfully treated with a Ladd procedure (see Treatment). The operation for malrotation decreases the risk of intestinal volvulus, but several cases have been reported in which volvulus developed weeks and even months and years after Ladd procedure.^[7]

The significant recurrence rate (7%) for midgut volvulus after the Ladd procedure has resulted in several attempts over the past century to augment this operation with fixation of the cecum and duodenum; however, overall results of fixation procedures have not shown improvement in outcomes. The fixation itself can be a source of volvulus, internal hernias, and intestinal obstruction. Therefore, patient and family education on the signs and symptoms of obstruction and volvulus has proved to be the only effective prevention of the consequences of recurrent volvulus.

In general, in the absence of other significant abnormalities or bowel necrosis secondary to midgut volvulus, morbidity and mortality of malrotation and its correction are low, and these children can be expected to do well, with an excellent chance of total resolution of related symptoms. Volvulus has been reported in 45-80% of infants with malrotation and is much more life threatening. Surgical correction is mandatory as long as the patient is stable enough to undergo the procedure and general anesthesia.

In addition, malrotation places the infant at increased risk for intussusception. Waugh syndrome, the presence of intussusception and malrotation, was first described in 1911. Poor fixation of the cecum allowing easier ileal advancement is noted in almost all infants with intussusception and is central to the pathophysiology of malrotation.

Patients who are asymptomatic and whose condition is undiagnosed before age 2 years may never become symptomatic; however, without operation, malrotation is estimated to result in volvulus in 1 out of 3 patients.

It is important to provide patient education on recurrence of symptoms after surgery or before surgery, if delayed. Patients and their family members should understand and be sensitive to any obstructive symptoms, especially signs and symptoms of volvulus.

Any intolerance of food or continued abdominal symptoms may warrant reexploration of the abdomen, particularly if associated with bilious vomiting. In addition, instruct patients to inform any physician they visit of their medical history of volvulus, especially if the appendix is left in situ.