Q: What is a volvulus of the colon?
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A: The term volvulus originates from the Latin word volvere – to twist. Volvulus of the colon is a twist of the bowel along its own mesentery, which can cause complete or partial or obstruction of the bowel or impair the blood supply.
Q: Where are the locations of colonic volvulus?
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A: Colonic volvulus accounts for 10% - 15% of large bowel obstruction. Colonic volvulus may involve the sigmoid colon (60% - 75%), the cecum (25 - 33%), transverse colon (1% - 4%), and splenic flexure (1%).
Q: What are the general considerations about sigmoid volvulus?
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A: Sigmoid volvulus is the torsion of the sigmoid along its mesenteric axis, around a fulcrum point, leading to a closed-loop obstruction, which can cause ischemia, perforation, and death. The sigmoid is the most common site of colonic volvulus and accounts for 60%-75% of all cases of colonic volvulus. Sigmoid volvulus occurs most frequently in the elderly, who have an elongated and chronically dilated sigmoid colon. Some predisposing factors include congenital or acquired anatomical variations, such as a long sigmoid colonic redundancy with an elongated mesentery, a history of abdominal surgery, late pregnancy, mental retardation, chronic constipation, Chagas disease, a high-fiber diet, and hospitalization.
Q: Which are the clinical manifestations of sigmoid volvulus?
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A: The clinical diagnosis of sigmoid volvulus can be challenging because its clinical presentation has low specificity. The classic clinical manifestations include abdominal pain, constipation, and distention. Other clinical findings are diarrhea, vomiting, tense and tender abdomen, bright red blood in the stool, and sluggish gut sounds.
Q: What are the types of sigmoid volvulus?
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A: The types of sigmoid volvulus are organo-axial volvulus and mesentero-axial volvulus. In the organo-axial volvulus, there is no closed-loop obstruction because torsion occurs around the long axis of the loop, and there is no more than one complete turn, with only one transition point. In the mesenteric-axial volvulus, there is a closed-loop obstruction, in which the loop twists around its mesenteric axis.
Q: What are the radiographic features of the sigmoid volvulus?
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A: The radiological features include: - the absence of rectal gas; - the inverted V or U-shaped distended sigmoid; - the coffee bean sign, the coffee bean-like shape that the dilated sigmoid colon may assume; - the northern exposure sign, a dilated sigmoid colon arising from the pelvis and extending cranially beyond the level of the transverse colon; - the “bird beak” sign describes the smooth, tapering transition point of the obstruction; - white-stripe sign, which is an obliquely oriented vertical white line that represents the opposed walls of the dilated loop; - Frimann Dahl`s sign, the three lines converging towards the site of obstruction; - bent inner or ace of spades sign; - omega or horse-shoe sign.
Q: How can the enema study contribute in the context of sigmoid volvulus?
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A: The contrast enema allows easy distinction between large bowel obstruction and pseudo-obstruction, and it may confirm a colonic volvulus. However, it is generally not carried out due to the risk of impending gut ischemia or perforation. There is a bird beak sign in an enema study, a beak-shaped point, at the level of the distal aspect of the twist in the sigmoid, beyond which no contrast material passes, representing an abrupt termination of the contrast material column. The examination is performed under low pressure, without insufflation of the balloon.
Q: What are the CT findings and signs of the sigmoid volvulus?
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A: CT findings include: - X-marks-the-spot sign, which is the presence of two crossing sigmoid transition points at a single location; - split wall sign, caused by the separation of the loop walls by mesenteric fat; steelpan sign, which bears a close resemblance to the percussion instrument known as the steelpan; horseshoe or omega sign with hyperdense central bowel wall; - beak sign, which is better seen with the administration of rectal contrast; - inverted-U or V sign; - coffee beam sign; - whirl sign; - rectal decompression.
Q: How is the treatment of the sigmoid volvulus?
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A: The initial option for the treatment of sigmoid volvulus includes endoscopic decompression by either rigid or flexible sigmoidoscopy. The treatment may change to urgent laparotomy in the presence of clinical signs of peritonitis or CT findings revealing signs of bowel ischemia or perforation.
Q: What are the complications of sigmoid volvulus?
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A: The complications of sigmoid volvulus are closed-loop obstruction with a vascular compromise of the bowel wall, leading to ischemia, necrosis, and perforation. The CT findings of ischemia and perforation of large bowel wall include: - spontaneously increased attenuation of the large bowel wall (transmural hemorrhage necrosis); - the absence or decreased enhancement of the large bowel wall; - pneumatosis intestinalis or thickening of the large bowel wall each suggest ischemia; - pneumoperitoneum, which suggest perforation; - ascites or hemorrhage is usually present in the severe forms or sigmoid volvulus.