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Letter to the Editor: “Sigmoid volvulus: identifying patients requiring emergency surgery with the dark torsion knot sign”

by Dr. Sabri Selcuk Atamanalp (ssa@atauni.edu.tr)

Sigmoid volvulus: identifying patients requiring emergency surgery with the dark torsion knot sign

Dear Editor,

I read with great interest the article written by Heo et al [1] on the relationship between dark torsion knot sign at computed tomography (CT) and complicated sigmoid volvulus (SV). SV, the wrapping of the sigmoid colon around itself causing a colonic obstruction, is rare worldwide. But it is common in my practicing area, Eastern Anatolia [2]. My colleagues and I have 53 years of history and 1,026 cases of experience with SV, which is the largest published single-center SV series in the world [3]. In light of our comprehensive experience, my comments relate to the authors’ new description and its area of utilization.

Heo et al [1] define the sudden loss of mucosal enhancement at torsion knot as ‘dark torsion knot sign’ in SV. According the authors, this sign, which is easily recognisable by radiologists, is a significant predictor of bowel ischemia or gangrene with 78% of sensitivity and 98% of specificity rates. In conclusion, the authors suggest emergent surgery instead of endoscopic detorsion in patients with the dark torsion knot sign at CT [1]. As known, bowel ischemia or gangrene is a catastrophic complication of SV, which worsens the prognosis by increasing the mortality rate from 0-40% to 3.7-80%. Although some clinical and laboratory findings including melanotic stool, fever, abdominal guarding, rebound tenderness, shock, somnolence, leucocytosis, and metabolic acidosis suggest the bowel gangrene, except for melanotic stool, they are not pathognomonic [4]. Although CT is highly diagnostic in SV [5], if there is no contraindication, sigmoidoscopy is a unique method to identify the mucosal viability [6]. Additionally, endoscopic detorsion is the best treatment way in uncomplicated and non-gangrenous cases. Following a successful endoscopic detorsion, elective colectomy is suggested in nonelderly and well-conditioned patients [7]. It is well known that, in SV, the mortality and morbidity rates are 0-2% and 5-15% in elective surgery, while 5-50% and 30-60% in emergent surgery [8]. Even if the dark torsion knot sign suspects bowel ischemia or gangrene in most cases, in my opinion and experience, to perform emergent surgery instead of sigmoidoscopic examination in all SV patients with this sign may be unnecessary at least in some cases.

Second, in the authors’ series, two cases with irreversible bowel ischemia or necrosis seem as treated with elective surgery [1]. As known, the presence or suspicion of the bowel ischemia or gangrene requires an emergent surgery following an early and effective resuscitation. Additionally, if bowel ischemia or gangrene is determined during endoscopy in patients with SV, the procedure is terminated to perform an emergent surgery. If endoscopic detorsion is tried in such cases, bowel perforation or absorption of toxic materials from viable mucosa causing toxaemia and shock are the potential risks. For these reasons, ischemic or gangrenous cases have limited time to treat [9]. However, elective surgery requires a one to five day-preparation period [7]. Therefore, in my opinion and experience, time-consuming procedures such as elective surgery are not suitable treatment options for ischaemic or gangrenous cases.

I congratulate the authors for their interesting study including a new description, and I look forward their opinions regarding my discussions.