Colonic Volvulus




Introduction


In this chapter, we review the presentation, diagnostic strategy, and treatment algorithms for colonic volvulus.


Colonic volvulus is the torsion of a mobile loop of bowel with an elongated mesentery and a narrow pedicle. The twisting of the bowel around its mesenteric blood supply leads to acute luminal obstruction and decreased blood flow to the bowel wall that can progress to ischemia, infarction, and, eventually, perforation. Volvulus is rare in developed countries, where it is the cause of 2.5% of all cases of large bowel intestinal obstruction (LBO). However, volvulus causes up to 80% of LBO cases worldwide and remains the third leading cause of LBO behind cancer and diverticulitis. Volvulus must be distinguished from all other causes of colonic distention, including neoplasms, diverticulitis, inflammatory bowel disease, Ogilvie syndrome, Hirschsprung disease, and ileus.


Two main types of volvulus present in adults: sigmoid and cecal. Historically, 60% of colonic volvulus cases were sigmoid, with cecal volvulus accounting for 20% to 40%. However, the incidence of cecal volvulus has been increasing in developed countries, while the incidence of sigmoid volvulus remains stable. A recent United States–based study found cecal volvulus in approximately 60% of patients and sigmoid volvulus in 40%. Less common is transverse colon volvulus, which occurs in 2% to 4% of cases. The types of volvulus differ dramatically in their patient population and management.




Cecal Volvulus


Background and Demographics


Cecal volvulus presents when there is both an abnormally mobile ascending colon and a fixed point for the mobile segment to twist around. The main predisposing condition is failed fusion of the ascending colon to the retroperitoneum, a congenital anomaly found in 10% to 22% of individuals. This condition creates a mobile, intraperitoneal ascending colon that can twist around its own mesentery. Other risk factors are adhesions from previous surgery and an abdominal mass that serves as a fulcrum for rotation. No geographic distribution has been identified, but incidence is increased in developed countries with higher rates of previous abdominal surgery. Compared with sigmoid volvulus, cecal volvulus occurs more frequently in a younger (mean age 53 years), female population.


Pathophysiology


Two classic volvulus patterns exist—axial torsion (true cecal or cecocolic) and mesentericoaxial (cecal bascule). Axial torsion presents in two thirds of cecal volvulus cases. In this subtype, the distal ileum and ascending colon twist 180 to 360 degrees around each other along the longitudinal axis of the ascending colon. This torsion is similar to sigmoid volvulus, except it occurs in a clockwise direction. This form has a high mortality, because the mesenteric torsion is associated with vascular compromise, which can lead to ischemic gangrene and perforation. The cecal bascule subtype presents in one third of cecal volvulus cases. The cecum folds on itself anteromedially over the ascending colon, creating a ball-valve type obstruction at the level of the ileocecal valve. Because no torsion of the ileocolic mesentery is present, vascular compromise is rare and occurs only when significant distention prevents the cecum from unfolding into its normal position. Several risk factors have been identified, including congenital bands, cathartics, a high-fiber diet, previous pelvic surgery, and pregnancy.


Signs and Symptoms


Cecal volvulus presents with symptoms of a distal small bowel obstruction—colicky abdominal pain, nausea, vomiting, and obstipation. Eighty-five percent of affected patients have acute obstruction at presentation. A constricting band is found across the ascending colon intraoperatively.


Diagnostic Imaging


On an abdominal radiograph, the small bowel is distended, whereas the distal colon is decompressed. The classic radiograph finding is a round loop of air-distended bowel with haustral markings directed toward the left upper quadrant ( Fig. 52-1 ). In axial torsion, the medially placed ileocecal valve indents the dilated cecum, giving the characteristic “coffee bean” shape. With cecal bascule, the redundant cecum flips up medially into the upper abdomen, causing a dilated cecum and small bowel. Plain radiographs are insufficient to confirm cecal volvulus in 33% to 85% of cases. Barium enema demonstrates a “bird’s beak” or column cutoff sign in the right colon and is diagnostic in 88% of cases. However, performance of this study may unnecessarily delay surgery, so it should not be used routinely. A computed tomography (CT) scan is the test of choice. Pathognomonic CT signs include dilated small bowel and cecum centered on the whirled mesentery (“the whirl sign”) and an ileocecal twist. CT delineates the cause and level of high-grade obstruction and provides evidence of closed-loop obstruction or ischemia, facilitating timely management. However, almost 50% of cases are not diagnosed until laparotomy.




FIGURE 52-1


Radiographic findings of cecal volvulus.


Treatment


Prompt diagnosis and surgery can prevent the complications of cecal volvulus, which include closed-loop bowel obstruction and vascular compromise, gangrene, perforation, and death. The overall complication rate (17%) and mortality rate (<1%) are relatively low. The choice of surgery depends on the patient’s clinical condition. In severely debilitated patients, cecostomy is a reasonable option but is associated with a wound infection rate of 40% to 50% and recurrence rates up to 5%. Endoscopic decompression has been used but is less effective than for sigmoid volvulus, and the success rate is only 15% to 20%. Cecopexy—that is, fixation of the right colon and cecum—is associated with recurrent volvulus in 20% to 30% of patients. Percutaneous decompressive cecostomy performed under CT guidance has also been described an alternative to colonoscopy and surgical cecostomy for treatment of massive cecal distention in poor surgical candidates. Because all nonoperative techniques have high recurrence and complication rates, a right hemicolectomy with primary ileocolic anastomosis is the procedure of choice in a fit patient.

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Jul 15, 2019 | Posted by in GENERAL | Comments Off on Colonic Volvulus
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