Volvulus of the Stomach and Small Bowel

Epidemiology

Volvulus of the small bowel is more common in children and is most often secondary to malrotation. The incidence of SBV in adults varies considerably in different parts of the world, being uncommon in Western countries but more of a health care burden in Central Africa, Middle East, Asia, and the Indian subcontinent. No population-based studies have been reported from European, African, or Asian countries, making an assessment of the true incidence difficult. Retrospective studies dating back several decades suggest that the annual occurrence of SBV is 1.7 to 5.7 in North America and Western Europe, as compared with 6 to 37.5 patients diagnosed with SBV/year in Africa, Middle East, and Asia. Case series from the Western countries estimate that SBV accounts for 1.7% to 8% of all bowel obstructions and 4% to 13% of all small bowel obstructions. In Nepal, Uganda, Iran, and India 3.5% to 37% of all obstructions and 18.5% to 51.5% of all small bowel obstructions are attributable to SBV.

Coe et al. published results from a US population-based study using the Nationwide Inpatient Sample (1998–2010), a 20% stratified sample of US hospitals. Of the 2.065 million hospitalizations for bowel obstruction (representing an estimated 10.33 million hospitalizations across the United States) there were 20,680 cases of SBV, representing an incidence of 1%. Females were more often affected (56.6%), with the mean age of the patient population being 66 years, which is similar to previous studies reported from the Western countries. In contrast, the overwhelming majority of patients presenting with SBV in Nepal, India, Iran, and Afghanistan were young males.

Etiology

SBV is categorized as primary or secondary. Primary SBV occurs without predisposing factors or underlying anatomic abnormalities. In the African, Asian, and Middle Eastern countries 31% to 100% of patients with SBV have no other underlying pathology, whereas less than 30% (10% to 30%) of patients with SBV in the Western world and Far East share this etiology. The underlying cause of primary SBV is poorly understood, and several anatomic and dietary factors have been implicated. Primary SBV in developing nations correlates with lower socioeconomic status, with a vast majority of affected individuals being laborers and farmers. The consumption of large infrequent meals consisting of vegetables and high-fiber along with manual labor in an upright position has been postulated to account for this condition. SBV has been observed in Afghanistan during the month of Ramadan, when Muslims ingest large quantities of high-fiber food after prolonged fasting. De Souza reported 12 cases of primary SBV over a 2-year period in a Ugandan tribe who consumed a large amount of a beer rich in serotonin. A recent review from Spain noted an association of primary SBV with diabetic neuropathy and its altered small bowel motility.

Anatomically, the small bowel in high-risk populations has been observed to have a longer mobile mesentery with a narrower insertion and a lack of mesenteric fat. Patients with SBV in the Eastern countries have firm, muscular abdomens, theoretically limiting the mobility of bowel in the anteroposterior plane. It is thus postulated that females are less often diagnosed with primary SBV in the developing countries, their abdominal wall laxity from childbearing conferring an advantage. These observations support a popular theory that rapid filling of a segment of proximal intestine with high-bulk chyme pulls the heavier loops down into the left pelvis where there is little resistance and displaces the empty distal bowel loops upward toward the right upper abdomen, thereby initiating the torsion around the superior mesenteric vessels.

In contrast, secondary SBV is caused by predisposing factors, either congenital or acquired, and is more common than primary SBV in North America and Western Europe. In secondary SBV the intestine is twisted around an underlying point of fixation, and as the loop fills with fluid, peristalsis exacerbates the torsion, causing a closed-loop obstruction. By far the most common cause of secondary SBV are postoperative adhesions. Case reports have described a number of other lead points, including small bowel and mesenteric tumors, mesenteric lymph nodes, Meckel diverticulum, malrotation, small intestinal diverticula, ascariasis, tuberculous adhesions, and stomas. In pregnancy, SBV is the second most common cause of small bowel obstruction after adhesions.

In 56% to 80% of cases of primary SBV the intestinal torsion is clockwise, as it is for neonatal midgut volvulus associated with congenital malrotation. However, congenital malrotation causing volvulus rarely manifests in delayed fashion. Among all patients hospitalized for SBV (20,680), Coe et al. identified only 169 adult patient with malrotation (0.82%). In most case series the ileum was most often affected segment of small bowel.

Table 73.1 compares six case series of SBV, illustrating some of the differences between primary and secondary SBV between the Western countries and parts of Africa and Asia.