Volvulus pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: ;Hadeel Maksoud M.D.[2]

Overview

Regardless of cause, volvulus causes symptoms by two mechanisms. One is bowel obstruction, manifested as abdominal distension and vomiting. The other is ischemia (loss of blood flow) to the affected portion of intestine. This causes severe pain and progressive injury to the intestinal wall, with accumulation of gas and fluid in the portion of the bowel obstructed. Ultimately, this can result in necrosis of the affected intestinal wall, acidosis, and death. Acute volvulus therefore requires immediate surgical intervention to untwist the affected segment of bowel and possibly resect any unsalvageable portion.

Pathophysiology

• The twisting of a mobile loop of bowel can happen spontaneously and may be congenital or acquired.
• Acquired causes of volvulus include:
  • Adhesions
  • Iatrogenic e.g. lower GI endoscopy
  • Bowel atony
  • Hirschsprung's disease
  • Pregnancy
• Congenital causes are discussed below.

Intestinal Malrotation in Neonates and Infants

Embryology

• Malrotation occurs when there is arrest of the normal rotation of the embryonic gut.
• During weeks 4 - 8 of development, the embryonic coelom, or cavity, normally cannot accommodate the rapidly expanding gastrointestinal (GI) tract.
• Consequently, the primary intestinal loop pushes back into the yolk stalk, and will become the future umbilicus.
• The direction in which the loop grows takes the axis of the future superior mesenteric artery.
• As the primary intestinal loop grows out of the abdomen, it begins to rotate by twisting 90 degrees counterclockwise.
• There are two factors that force this rotation:
  • The proximal bowel grows faster than the distal bowel.
  • The liver has rapidly develops.
• During weeks 8 - 10, the primary intestinal loop continues to grow and returns back into the abdomen cavity and a further 180 degree counterclockwise rotation occurs.
• Overall, the primary loop twists a total of 270 degrees in a counterclockwise direction.
• Once the primary loop is in its final position, fixation to the posterior abdominal wall begins.
• The proximal bowel portion including the stomach and duodenum are fixated early in gestation through the ligament of Treitz.
• The colon takes a longer time to become fixated and usually, fixation is completed near term.

Pathophysiology of Infantile and Neonatal Volvulus

• Normal gut development means that:
  • A wide-based mesentery will extend from the ligament of Treitz in the left upper quadrant to the ileocecal valve in the right lower quadrant.
  • The primary loop will continue its rotation whilst returning to the abdominal cavity.
  • Both proximal (duodenojejunal) and distal (cecocolic) limbs rotate at the same rate and to the same degree.
• Congenital volvulus happens when the following anomalies have occurred:
  • Narrow mesenteric base
    • The midgut becomes suspended by a narrow pedicle
  • Non-rotation
    • In non-rotation, the primary loop undergoes no further rotation during its return to the abdominal cavity.
    • The small bowel becomes located on the right whilst the colon is on the left of the abdomen.
    • Non-rotation is less dangerous than malrotation because in non-rotation, the mesentery is wider and the risk of volvulus is lower.
  • Malrotation
    • In malrotation, the proximal (duodenojejunal) limb remains in a position of non-rotation, and the distal (cecocolic) limb partially rotates (usually only 90 degrees instead of 180 degrees).
    • Consequently,the cecum is relocated to the mid-upper abdomen, instead of the right lower quadrant.
    • The abnormally-positioned cecum is attached by bands of peritoneum (Ladd bands) to the right lateral abdominal wall.
    • Ladd bands can cause compression and obstruction of the duodenum extrinsically.

• Other anomalies of rotation can rarely occur, these include:
  • Rotation of the proximal (duodenojejunal) limb is reversed resulting in a duodenum that is located anteriorly to the superior mesenteric artery.
  • Rotation of the distal (cecocolic) limb is reversed resulting in a transverse colon that is located posteriorly to the superior mesenteric artery.
  • Finally, a combination of reversed rotation of the proximal (duodenojejunal) limb with normal rotation of the distal (cecocolic) limb can lead to a paraduodenal hernia.
    • In this anomaly, anterior to the superior mesenteric artery lies the duodenum. Anterior to the duodenum, the distal (cecocolic) limb rotates normally.
    • The mesentery of the right colon creates a pouch, the small bowel then herniates into it.

Ileal and Sigmoid Volvulus

• The mesentery anchors the ileum and sigmoid colon to the abdominal wall.
• An air filled loop of the sigmoid colon or the ileum, sometimes, twists itself about the axis of the mesentery.
• The incidence of volvulus occurring increases with a redundant or longer than normal mesentery.
• If the degree of twisting is beyond 180 - 360 degress, then the bowel loop will become obstructed and ischemia will begin.
• Ileosigmoid knotting is a variant of sigmoid volvulus where the ileum wraps around the sigmoid in a clockwise direction.

Gastric Volvulus

• Normally, there are ligaments such as the gastrocolic, gastrohepatic, gastrosplenic and gastrophrenic ligaments that keeps the stomach in place by attaching it to other abdominal organs and the diaphragm.
• However, the stomach can twist around its horizontal or vertical axis.
• Gastric outlet obstruction may occur as a result of abnormal rotation more than 180 degrees.
• Chronic rotation can cause bleeding by decreasing venous return and increasing capillary pressure.

Cecal Volvulus

• The cecum is especially liable to being mobile congenitally.
  • The cecum becomes mobile when failure of the ascending colon mesentery to fuse with the posterior parietal peritoneum occurs.
  • Autopsy studies have shown that about 10-25% of the population have a mobile cecum and ascending colon sufficient to develop a volvulus.
  • A congenital mobile cecum can also cause mobile cecum syndrome.
• There are three types of cecal volvulus, type I and II are the most common, type III account for the remaining 20% of cases:
  • Type I
    • The cecum twists in a clockwise manner along its axis.
    • The cecum fills with air and remains in right lower quadrant.
  • Type II
    • The cecum and a proximal part of the ileum twist in a counterclockwise direction.
    • The cecum becomes inverted and is relocated to the left lower quadrant.
  • Type III
    • The cecum folds upwards and back on itself rather than rotating along its axis.

References