01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Sigmoid volvulus occurs when a mobile, elongated sigmoid colon rotates around its mesenteric attachment. The twist blocks the lumen at two points and can impair venous drainage before arterial perfusion is lost. The resulting distension is therefore not simply severe constipation: the same anatomical event can obstruct transit and threaten the blood supply. Chronic constipation, reduced mobility, institutional care and neuropsychiatric disease are common contexts, although the condition is not confined to older people. A history of previous successful decompression is a warning about recurrence rather than evidence that the next episode will also be uncomplicated.
Treatment has two linked aims: relieve the acute twist safely and reduce the likelihood of another episode. Endoscopic detorsion is valuable when bowel viability is reasonably preserved and the patient is physiologically suitable. It provides decompression and a direct view of the accessible mucosa. Failure to pass the twist safely, evidence of gangrene, perforation or severe deterioration changes the pathway to surgery. After successful decompression, the redundant sigmoid remains, so symptom resolution alone is an incomplete long-term plan. Decisions about resection should be made during the same admission, with attention to frailty, consent, capacity and the morbidity of both intervention and non-intervention.
Key points
- In a stable patient without suspected ischaemia, perforation or peritonitis, urgent flexible endoscopic detorsion can decompress the sigmoid and inspect its mucosa.
- Peritonitis, shock, nonviable mucosa or failed detorsion requires urgent operative assessment and usually resection; do not persist with unsafe endoscopy.
- A decompression tube can maintain initial relief after detorsion, but it does not remove the anatomical tendency to twist again.
- Offer definitive sigmoid resection during the index admission when appropriate because recurrence after decompression alone is common and potentially lethal.
- CT is valuable when the diagnosis is uncertain or a complication is suspected; normal lactate and absence of guarding cannot independently establish viability.
- Frailty changes the balance between resection, selected fixation and recurrent obstruction; document the patient’s goals and the agreed escalation plan.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Redundant mobile sigmoid
An elongated sigmoid with a narrow mesenteric attachment can rotate more readily. Chronic constipation and prolonged colonic distension may accompany this vulnerable anatomy in affected patients.
Immobility and neurological illness
Reduced mobility, institutional care and neuropsychiatric conditions commonly coexist with sigmoid volvulus. Medication-related constipation and difficulty communicating early symptoms can contribute to delayed recognition.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Twisting of the mesentery
Rotation obstructs the sigmoid lumen at its entry and exit points. The closed loop progressively fills with gas and fluid while the mesenteric vessels become compressed.
- 2Venous congestion and infarction
Venous outflow obstruction causes oedema and rising wall pressure. Continued twisting can then compromise arterial delivery, progressing from reversible injury to gangrene and perforation.
- 3Persistent anatomical susceptibility
Endoscopic detorsion restores luminal flow but leaves the redundant colon in place. That remaining mobility explains why successful initial decompression does not eliminate recurrence risk.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Progressive tympanic distension, constipation and abdominal discomfort are common; vomiting often appears later. Obtain collateral information about baseline bowel habit and the onset of symptoms when cognitive or communication difficulties limit the history. Do not mistake chronic laxative use for proof that this episode is uncomplicated constipation.
Constant or intensifying pain, new tenderness, guarding, shock or fever can indicate infarction or perforation. These signs require immediate senior surgical involvement. Ischaemia may develop before overt peritonitis, so their absence is not a sufficient reason to delay an otherwise concerning presentation.
Ask how earlier episodes were diagnosed and treated, whether a tube remained in place and whether definitive surgery was discussed. Recurrent admissions may progressively reduce function and expose the patient repeatedly to ischaemia and emergency surgery. The burden of repeated “successful” detorsions belongs in the treatment discussion.
A markedly dilated colon beyond the sigmoid or longstanding megarectum suggests more extensive dysmotility. Distinguish this chronic background from simple acute upstream distension because it can affect the required extent of resection and the risk of recurrence in retained bowel.
Assess the patient’s usual mobility, nutrition, cognition, living arrangements and care requirements before the acute illness. Invite appropriate geriatric and anaesthetic assessment. A discussion should address survival, recovery and independence as well as the technical possibility of an operation.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Prompt imaging matched to stabilityFirst step - Why
- Establish sigmoid twisting and look for complications that alter the decompression route.
- Interpretation and limitations
- A characteristic coffee-bean loop on a film may support an uncomplicated recurrence in a stable patient. Contrast-enhanced CT is appropriate when the cause is uncertain or ischaemia or perforation is suspected; look for the mesenteric whirl, transition points, enhancement and extraluminal gas.
- 02
Blood gas, lactate and physiological assessment - Why
- Look for systemic consequences while avoiding false reassurance from a single result.
- Interpretation and limitations
- Acidosis or increasing lactate heightens concern, but normal lactate can coexist with bowel ischaemia. Repeated observations and the abdominal examination are essential. Anaesthetic and operative preparation should continue if the clinical picture already warrants intervention.
- 03
Renal profile, electrolytes and blood count - Why
- Assess dehydration, concurrent illness and correctable risks before treatment.
- Interpretation and limitations
- Poor intake and vomiting can precipitate renal dysfunction, especially in frail patients. Potassium and other electrolyte disturbances need management, but correcting them does not untwist a mechanically obstructed sigmoid. Check blood availability if resection is likely.
- 04
Therapeutic flexible sigmoidoscopy with mucosal assessment - Why
- Detorse viable bowel and judge whether endoscopic treatment remains appropriate.
- Interpretation and limitations
- The endoscopist must negotiate the transition safely, achieve decompression and assess the mucosa. Advanced ischaemic change or evidence of perforation requires stopping and urgent surgical management. A technically passed scope without sustained decompression or adequate viability assessment is not a completed treatment.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Obstructing sigmoid cancer
A fixed malignant narrowing may produce similar distension and constipation. CT can identify a focal tumour rather than the converging limbs and mesenteric rotation of volvulus.
Acute colonic pseudo-obstruction
Functional dilatation can be striking but lacks a mechanical twist. Distinguishing the two is essential because their pharmacological and endoscopic strategies are different.
Caecal volvulus
A displaced distended caecum may mimic a large sigmoid loop on a film. CT localisation matters because caecal volvulus usually requires surgery rather than endoscopic detorsion.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Acute treatmentChoose detorsion or immediate resectionFirst stepA sigmoid volvulus is diagnosed and bowel viability must guide treatment.+
- 1Resuscitate, keep the patient nil by mouth and obtain senior surgical review. Shock, peritonitis, suspected infarction or perforation calls for urgent surgery; antibiotics for suspected contamination accompany source control rather than replace it.
- 2If the patient is stable and there is no evidence of threatened viability or perforation, arrange urgent flexible endoscopic detorsion by an experienced operator. Assess mucosa and stop if gangrene is seen or safe progress cannot be made.
- 3After successful detorsion, leave an appropriate decompression tube when feasible and provide a care plan that maintains its function. ACPGBI describes a short period, commonly one to three days, rather than treating the tube as permanent prevention.
- 4Reassess promptly after the procedure for pain relief, reduced distension and physiological improvement. Failure, immediate recurrence or deterioration requires renewed operative consideration.
02Worked caseSuccessful decompression followed by preventionA 77-year-old independently living man presents with his first sigmoid volvulus.+
- 1He has two days of distension and constipation, pulse 92 and a soft tympanic abdomen without guarding. CT confirms a sigmoid twist with preserved enhancement and no free gas; lactate is 1.5 mmol/L, interpreted as supportive rather than proof of viability.
- 2Following surgical assessment and resuscitation, flexible sigmoidoscopy crosses the transition safely, shows viable mucosa and releases gas and stool. A decompression tube is left and monitored, and the abdomen becomes visibly softer.
- 3Over the next day the patient remains comfortable with improving intake and renal function. The team assesses baseline fitness and explains the substantial risk of recurrence after detorsion alone, including the possibility of infarction during a future attack.
- 4DefinitiveHe elects definitive treatment. After optimisation, sigmoid colectomy is performed during the same admission; the remaining bowel is healthy without chronic megacolon, and a primary anastomosis is appropriate to the operative findings.
- 5He returns to oral intake and mobilises without signs of leak. At follow-up he has resumed his usual activities and has no further obstructive episode. The final explanation connects the first procedure’s immediate relief with the second procedure’s removal of the recurrent anatomical risk.
03Individual definitive careWhen standard resection carries major riskDefinitiveDetorsion has succeeded, but frailty or severe comorbidity makes the next step difficult.+
- 1Discuss the expected burdens of surgery, recurrent volvulus and repeated admissions with the patient and the multidisciplinary team. If capacity is lacking, follow a documented best-interests process incorporating prior wishes and the views of those close to the patient.
- 2Where resection presents prohibitive risk, selected endoscopic fixation or percutaneous endoscopic colostomy may be considered in an experienced service. Explain tube care, migration, infection and peritonitis risks; this is not a harmless equivalent of colectomy.
- 3EscalationIf a nonoperative long-term plan is chosen, make the recurrence and emergency escalation plan explicit. Confirm which treatments the patient would want if a future episode involves infarction or perforation, and communicate this plan across care settings.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Ischaemia and gangrene
Compromised mesenteric blood flow can kill the twisted segment. Neither a normal early lactate nor an initially soft abdomen reliably excludes evolving injury.
Perforation and septic shock
Loss of bowel integrity releases organisms and intestinal contents into the peritoneum. This can cause rapidly worsening shock and requires urgent consideration of operative source control.
Recurrent obstruction
A further twist can occur after an apparently complete recovery from detorsion. Repeated episodes carry renewed risks of infarction, hospital admission and loss of functional independence.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Observe the abdomen, pain and physiological response immediately after detorsion. Ongoing tenderness or systemic deterioration requires assessment for missed ischaemia, incomplete reduction or perforation despite an initially successful procedure.
- Check the decompression tube’s position and function within the endoscopy team’s instructions. Loss of output with renewed distension should trigger review, rather than blind manipulation that risks injury.
- Follow hydration, renal function and electrolytes while restoring intake and mobility. Treat contributing constipation after the obstruction has resolved, without implying that laxatives alone prevent recurrent twisting.
- Before discharge, verify that the definitive plan has a responsible team, timing and documented patient agreement. Frailty assessment and a decision against surgery are active clinical decisions that need the same clarity as a booked operation.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Mucosa and mechanism
Flexible endoscopy has an advantage over blind tube passage because it can inspect the mucosa as well as decompress the lumen. Its role depends on careful selection and technical judgment. Forceful attempts at detorsion in an ischaemic segment risk perforation and delay the resection the patient needs.
Recurrence estimates vary
Guidelines describe high recurrence after detorsion alone, with many series reporting roughly half or more of patients affected. The exact percentage depends on follow-up, selection and competing mortality. The clinically useful conclusion is the need for a definitive discussion, not a promise that one quoted number predicts an individual outcome.
Megacolon changes the operation
In established diffuse megacolon with sigmoid volvulus, removing only the sigmoid may leave abnormal bowel liable to further obstruction. WSES supports more extensive colectomy in this setting, although the evidence is limited. This refers to concomitant chronic colonic dysfunction, not every acutely distended colon upstream of a twist.
Reconstruction follows the patient
Emergency sigmoid resection can end in an anastomosis, a protected anastomosis or an end colostomy. Viability, contamination and physiological reserve determine the balance. Infarcted bowel requires careful handling and source control; the wish to avoid a stoma must not take precedence over an unsafe reconstruction.
11Common pitfallsFrequent interpretation and management errors.
- 01
Labeling a repeated volvulus as benign because earlier episodes resolved endoscopically overlooks the risk of infarction during any subsequent attack.
- 02
Continuing endoscopy after gangrenous mucosa is identified can perforate the colon and postpone necessary resection; stop and escalate immediately.
- 03
Discharging after detorsion without a documented recurrence-prevention discussion leaves the main anatomical problem and the future emergency plan unresolved.
- 04
Equating advanced age with prohibitive operative risk obscures differences in frailty, baseline function, patient goals and the burden of another emergency admission.