Intestinal Volvulus Workup

If malrotation is suspected (eg, in an infant with bilious vomiting), a diagnostic workup is mandatory. A few laboratory studies may be helpful in the management of a patient with malrotation. However, laboratory tests should not delay immediate surgical consultation and operation when volvulus is suspected; no laboratory tests are specific for this problem.

Imaging studies are an integral part of the diagnostic process for a patient suspected of having malrotation or other gastrointestinal (GI) obstruction. The most expeditious and definitive test is usually an upper GI contrast study, which is performed in real time to document the position of the ligament of Treitz and the possible presence of proximal intestinal obstruction.

Although various other studies may be useful as adjuncts or to encourage evaluation for malrotation and volvulus, the definitive diagnosis is made on the basis of findings from a contrast upper GI series, barium enema (BE), or laparotomy.

A complete blood count (CBC), clotting studies, electrolyte level tests, and blood glucose level tests are usually sufficient for preoperative evaluation. In the early stages, all blood test findings may be normal; however, as the disease progresses from mechanical obstruction to intestinal ischemia and necrosis, it produces electrolyte disturbances, elevated blood urea nitrogen (BUN) and creatinine levels, hypocarbia, and lactic acidosis.

CBC monitoring helps the physician assess the severity of illness. Ischemia may cause an elevation in the white blood cell (WBC) count. A very high WBC count may ominously suggest gangrene and sepsis. A decrease in hemoglobin and hematocrit may occur with venous oozing.

Regular electrolyte monitoring also assists the physician in assessing the severity of disease, as well as directing management and support. Abnormal electrolytes are a result of dehydration, sepsis, and acidosis. Bowel edema caused by volvulus and obstruction can lead to shifts of large amounts of fluid and electrolytes into the interstitial space and bowel lumen, leaving the patient intravascularly depleted even without the vomiting and diarrhea that often accompany this condition.

Common electrolyte abnormalities in such cases include hyponatremia, hyperkalemia, metabolic acidosis, increased BUN and creatinine levels, hypochloremia, and lactic acidosis. Careful monitoring and aggressive support of fluid and electrolyte status can treat or prevent dehydration and subsequent worsening of vascular compromise due to hypotension.

Findings ranging from occult to frank blood may be present in the stools of a child with malrotation, if mucosal ischemia has developed; therefore, heme testing of the stools of a child suspected to have malrotation may be useful.

The presence of blood suggests volvulus, at least intermittently, and should encourage expeditious transfer to the operating room once diagnosis is confirmed. However, the presence of melena or currant jelly stools is not necessarily predictive of bowel necrosis. Viable bowel may ooze blood secondary to venous congestion without arterial obstruction.

Plain abdominal radiography is useful, but findings are not definitive. This study may reveal the following:

• Normal gas pattern
• Gasless abdomen
• Dilated intestine suggestive of a paralytic ileus or mechanical obstruction
• Duodenal obstruction with a double bubble

In early cases, plain abdominal radiography may not be helpful, but oral contrast studies (see Contrast Radiography) may reveal malrotation and intestinal obstruction.

Ideally, abdominal radiographs should be obtained in 2 views (ie, supine, upright, or lateral recumbent). These views may reveal evidence of small bowel obstruction, including dilated small-bowel loops; marked gastric or proximal duodenal dilatation, with or without intestinal gas; and air-fluid levels.

The classic sign on abdominal radiography is the double bubble, indicative of gastric and duodenal dilatation (see the image below). Duodenal obstruction causes gastric and duodenal distention with a prominent duodenal bulb and air-fluid levels in the proximal duodenum and stomach on upright radiographs. The double-bubble sign may not be evident if the patient’s vomiting has cleared the proximal GI contents. In an older child, the sign may be absent during an asymptomatic period.

The double-bubble is often accompanied by a relative paucity of lower GI gas. This is highly suggestive of volvulus or duodenal stenosis and atresia. A double-bubble sign with paucity of lower GI gas combined with clinical signs and symptoms of distress, such as fever, lower abdominal distention, melena, or hemodynamic instability, suggests volvulus and possibly gangrene and should lead directly to laparotomy. In this situation, pneumatosis coli may be observed on plain radiographs and is an ominous sign.

Nonspecific radiographic findings are more common in older children. The chronicity of their condition usually allows some adaptation. Their obstruction, by necessity, must be more partial and intermittent, allowing GI contents and gas passage into lower GI areas.

Normal findings on plain radiographs in a child of any age with clinical signs and symptoms of malrotation can give the physician a false sense of security, creating a dangerous situation for the patient. In the presence of clinical suspicion, contrasted studies (eg, an upper GI) are warranted for confirmation.

In sigmoid volvulus, as contrasted to midgut volvulus, plain radiography may reveal a characteristically distended sigmoid colon.

Upper GI versus lower GI imaging

The diagnosis of malrotation can be confirmed with upper or lower GI contrast study findings. However, over the past 7 decades, controversy has emerged over the use of the upper GI series versus the use of the lower GI series (contrast enema). Physicians have been reluctant to administer a barium meal to infants suspected of obstruction; hence the popularity of BE.

The upper GI series provides more information regarding the degree of obstruction and the actual location of proximal GI anatomy. BE findings are more likely to be inconclusive; furthermore, BE impedes reading of any subsequent upper GI study, owing to the presence of contrast in the colon.

In 1992, Ford et al found that a limited upper GI study using only 5 mL of barium was well tolerated and allowed visualization of anatomy and subsequent BE if needed, as in the case of complete obstruction with necessary observation of lower anatomy.^[11]

Overall, most centers prefer upper GI imaging for the radiologic evaluation of malrotation and midgut volvulus. In neonates, a contrast enema is useful in ruling out intestinal atresia, meconium ileus, Hirschsprung disease, and other rare causes of intestinal obstruction.

Upper GI series

Confirmation and definitive diagnosis are accomplished more easily with an upper GI contrast series. If volvulus is present, signs include incomplete duodenal obstruction, usually at the third portion of the duodenum (see the image below).

The proximal duodenum is often dilated with a “bird’s-beak” obstruction (see the first image below) and a spiral or corkscrew duodenal configuration (see the second and third images below). This is a result of the abnormal positioning and the adhesive obstruction of Ladd bands.

The duodenojejunal (DJ) junction in malrotation is misplaced, either at or to the right of the midline. The fourth part of the duodenum and the ligament of Treitz are not visible to the left of the midline between the lesser and greater curvatures of the stomach.

Although most malrotations may be diagnosed by following the passage of contrast to the ligament of Treitz, continuing the study through the small bowel is important. Here the proximal jejunal loops are observed in an abnormal position, usually leading down to the right lower quadrant. The walls of the small bowel may also appear to be thickened.

Specificity of upper GI studies in detecting malrotation is almost 100%, but their sensitivity for detecting midgut volvulus is only 54%, reflecting the importance of clinical judgment in diagnosis.

Contrast enema

If the findings on the upper GI study are nonspecific and suggestion of malrotation continues, a contrast enema may be administered, preferably of barium. However, the results are not reliable if a midgut volvulus is present. In patients with bilious vomiting and a low clinical suspicion for midgut volvulus, lower GI imaging may be used to rule out colonic obstruction due to conditions such as atresia, Hirschsprung disease, and meconium ileus or meconium plug; it may actually prove to be therapeutic.

The sign sought with this study is an abnormally placed cecum, high in the right upper quadrant, midline, or on the left side (see the image below). BE results can be obscured. A high or mobile cecum can be considered normal in the absence of other abnormalities and is present in as much as 16% of the population. Additionally, barium often refluxes into the terminal ileum, confusing the identification of the cecum, especially in the newborn.

In malrotation, the contrast enema usually reveals the cecum in the right upper quadrant (see the image below). Outside the newborn period, an upper GI contrast study is more commonly performed in children who develop symptoms and signs suggestive of volvulus after their bowels have “opened up.” Malrotation should be suspected if the ligament of Treitz is not positioned to the left of the midline at or above the level of the duodenal bulb. The upper GI study may also reveal a swirling or corkscrew pattern within the bowel, leading to an obstruction.

Failure to recognize malrotation has been observed with lower GI imaging in 5-20% of patients with a normally located cecum.

In patients with sigmoid volvulus, lower GI imaging reveals dilated rectosigmoid loops with an abrupt inability to pass contrast beyond obstruction.

The use of ultrasonography in the diagnosis of malrotation has been investigated, although it usually is not very helpful and is not recommended in evaluating such patients.

Ultrasonography may reveal a midline abdominal mass with dilated collateral mesenteric vessels and whirling small intestinal loops, shown as sonolucent layers. In some cases, it may reveal intraluminal fluid or edema in the bowel wall. If performed for other reasons, it may reveal persistent distention of the duodenum as it courses around the head of the pancreas.

Although not usually necessary, ultrasonography may reveal abnormalities of intestinal rotation based on vascular anatomy. In many patients with malrotation, the normal anatomic relationship between the superior mesenteric artery (SMA) and the superior mesenteric vein (SMV) is altered, with the artery lying anterior or even to the right of the vein (see the image below). On the other hand, a normal anatomic relation between SMA and SMV does not rule out malrotation. Reminding physicians that patients with malrotation always have a left-sided SMV postoperatively is helpful.

Dufour et al, in a study examining more than 300 patients with ultrasonography, found that an SMV to the left of the SMA was highly suggestive of malrotation, whereas an anterior SMV was questionable.^[12] Positioning of the mesenteric vessels was normal in 326 patients, 9 of whom had malrotation. On the basis of these results, Dufour et al recommended upper GI studies for any suspected malrotation; however, if ultrasonography is used to evaluate abdominal symptoms, useful information may be obtained from the placement of the mesenteric vessels.

Computed tomography

The use of computed tomography (CT) scanning in the diagnosis of malrotation has also been investigated. Abdominal contrast CT has a high sensitivity for demonstrating small bowel obstruction.^[13] The finding of multiple and posterior location of transition points within the small bowel (segments where dilated small bowel is immediately followed by collapsed bowel) is predictive of volvulus (see the image below).

The “whirl sign” (clockwise or counterclockwise twisting of the bowel that extends for at least 180°) can also be seen on CT scans in the mesentery of the midgut when a frank volvulus is present.

Laparoscopy

An article published by Hsiao and Langer reviewed the utility of laparoscopy for evaluating rotation and fixation anomalies in children with diagnostic or equivocal imaging results. In 41 % of children with diagnostic imaging, a discrepancy was found by laparoscopy. Similarly, in 32% of children with equivocal imaging, laparoscopy demonstrated a rotational anomaly that placed them at risk for midgut volvulus.^[14]

Nuclear imaging

Rarely, lymphatic obstruction leads to mesenteric cyst formation and chylous ascites. In this case, a dense liver can be visualized pushed medially by chylous ascites (less dense) in the paracolic gutters.

The histology of the affected bowel is related to the degree of vascular compromise. The venous obstruction caused by volvulus may cause venous engorgement and edema. Arterial obstruction can result in various stages of ischemia, ranging from a mild degree to frank necrosis and gangrene, complete with neutrophilic infiltration.

Lymphatic obstruction, which results in chylous ascites, may show enlargement of the lacteals, which are found within the intestinal villi. In the case of malrotation without volvulus, bowel histology may be normal.

Associated abnormalities cause their own histologic changes. For instance, peptic ulcer disease has a high correlation with malrotation in older children and adults; therefore, gastric and duodenal erosions may be present.