INTESTINAL SURGERY II

Sigmoid volvulus, acquiredmegacolon andpseudo-obstructionJames Melling

Carol A Makin

Volvulus of the colon

AbstractThis article describes sigmoid volvulus, acquired megacolon/megarectum

and pseudo-obstruction, their associated features, clinical presentation,

investigation and management. These three disorders present acutely

with features of large bowel obstruction. Initial management for all

three is conservative in the absence of peritonitis or perforation. Inappro-

priate surgery may be associated with considerable morbidity and

mortality emphasizing the need for a good understanding of the disease

process and thorough investigation.

Keywords Acquired megacolon; acquired megarectum; large bowel

obstruction; Ogilvie’s syndrome; pseudo-obstruction; sigmoid volvulus

Sigmoidcolon

180

Sigmoid volvulus

Definition: Sigmoid volvulus occurs when a redundant loop of

sigmoid colon, not fixed by peritoneal attachments, twists

around its mesentery more than 180�. This produces a closed

loop bowel obstruction. The obstructed segment, being blocked

distally, is unable to decompress proximally (Figure 1). The

blood supply to the affected bowel is impaired due to the twisted

mesocolon, leading to ischaemia. Fermentation within the closed

loop produces gas and also increases the osmotic pressure

between intestinal contents and the capillaries, drawing fluid into

the bowel lumen. The bowel diameter increases, the tension in

the wall increases and this further impairs the blood supply

leading to worsening ischaemia and eventually perforation. As

the viability of the bowel becomes threatened, bacterial trans-

location occurs into the portal circulation leading to systemic

sepsis. Untreated, the volvulus will almost inevitably progress to

ischaemia, gangrene, perforation and death.

Incidence and aetiology: Sigmoid volvulus accounts for up to

6% of all intestinal obstructions in North America and Europe.

Here the typical patient is elderly, institutionalized, with poor

mobility and a history of chronic constipation. Co-morbidities

James Melling MBChB MRCS is a Clinical Research Fellow at the School of

Molecular and Clinical Cancer Medicine, University of Liverpool, UK.

Conflicts of interest: none declared.

Carol A Makin PhD FRCS is a Consultant Surgeon at the Princess

Elizabeth Hospital, Guernsey, Channel Islands, UK. Conflicts of interest:

none declared.

SURGERY 29:8 387

such as Parkinson’s disease, Alzheimer’s disease, and multiple

sclerosis are not unusual and electrolyte disturbance, particularly

hypokalaemia, should be excluded. Some individuals may have

an anatomical predisposition with a congenitally long, mobile

sigmoid loop. This, in association with a high dietary fibre

intake, may explain why sigmoid volvulus is particularly

common in India and Africa where it is the commonest cause of

bowel obstruction.1 Males appear to be troubled more often than

females.

Clinical presentation: Affected individuals present acutely with

signs and symptoms of large bowel obstruction e abdominal

pain, absolute constipation, distension (which may be asym-

metrically noted in the upper abdomen), tenderness and an

empty rectum. Vomiting is a late feature. In 50% of cases there is

a history of similar previous attacks which may have resolved

spontaneously with the passage of large quantities of flatus and

faeces.2 Signs of peritonitis and sepsis suggest ischaemia of the

volved loop.

Fulcrum forthe twist

Figure 1 Line drawing of a redundant sigmoid loop before and after

twisting 180�. Note long redundant sigmoid colon with a narrow based

mesentery leading to the twist (arrowed).

� 2011 Elsevier Ltd. All rights reserved.

INTESTINAL SURGERY II

In two-thirds of cases a plain abdominal X-ray will demon-

strate a dilated air-filled sigmoid colon exhibiting an inverted

U-shaped appearance which has been likened to a ‘coffee bean’.

The proximal large bowel will be dilated due to proximal

obstruction, with or without dilated small bowel depending on

the competency of the ileocaecal valve (Figure 2). An erect chest

X-ray looking for pneumoperitoneum, when negative, will help

to exclude perforation.

Computed tomography (CT) confirms classic appearances of

a whorl pattern in the mesocolon associated with a dilated

haustra-free sigmoid colon.

The colonoscopic appearances are both diagnostic and ther-

apeutic and are helpful in eliminating other causes of large bowel

obstruction (see below).

Management: Initial management is aimed at symptom control

and resuscitation, including the correction of hypovolaemia and

electrolyte imbalance.

However, once established, spontaneous untwisting of the

volved sigmoid colon is rare and therefore a definitive treatment

plan is required. Individuals fall into two groups; those with no

evidence of peritonitis e no clinical, laboratory, or radiological

signs of bowel necrosis or perforation e and those with evidence

of peritonitis.

In the absence of peritonitis, endoscopic decompression and

derotation (untwisting) should be possible in 70e90% of cases.3

This can be attempted with either a rigid sigmoidoscope or

a colonoscope. Using small amounts of air and gentle pressure it

Figure 2 Abdominal X-ray demonstrating a sigmoid volvulus extending out

of the left iliac fossa (‘coffee bean’ appearance) with proximal colonic

dilatation.

SURGERY 29:8 388

is usually possible to advance the rigid sigmoidoscope or colo-

noscope to the twist at the rectosigmoid junction and then

through it into a voluminous sigmoid filled with gas and liquid

stool. A flatus tube may be left in place to maintain drainage. The

operator should wear protective clothing as decompression may

be associated with rapid egress of flatus and liquid stool. Endo-

scopic derotation buys time to optimize cardiopulmonary co-

morbidities in what is a high-risk group of patients, converting

an emergency situation to an elective one.3

If there is a failure to derotate the volvulus or where there are

clinical signs of peritonitis, perforation or ischaemia (as judged

by increasing pain, rising c-reactive protein (CRP) and white

blood cells (WBC) and free air on chest X-ray), surgery is indi-

cated without delay. Patients with ischaemia or perforations fare

poorly after surgery with mortality rates as high as 40%.4e6

Surgical options: Sigmoid volvulus is associated with a 90%

recurrence rate. All patients after initial endoscopic decompres-

sion should therefore be considered for definitive surgery.

Although general frailty, co-morbidities and poor WHO perfor-

mance status often makes it tempting to try and persist with

conservative management, the evidence suggests that even ASA-

4 patients with sigmoid volvulus do well with early surgical

intervention before recurrence of the volvulus with its associated

risks of colonic ischaemia.4 In the few patients without signifi-

cant co-morbidities there is an argument for proceeding straight

to surgery at the time of decompression. Only in exceptional

circumstances should alternatives to surgery be considered.

In the presence of viable colon, sigmoid colectomy and

primary anastomosis as a one-stage procedure during same

hospital visit is the procedure of choice. Bowel preparation and

on table lavage are not necessary. Surgery is aimed at preventing

the sigmoid colon twisting, therefore resection margins do not

need to be taken back to the twisted point in the bowel: any

convenient site will suffice, and the sigmoid colon will lift out

readily facilitating access.

Depending on bowel viability, surgical expertise, and the local

situation other surgical procedures commonly performed include

an end colostomy with closure of the rectal stump (Hartmann’s

procedure), a double-barrelled stoma as in PauleMikulicz’s

procedure, or subtotal colectomy and ileosigmoid anastomosis.

Where co-morbidities are such that the patient is considered

unfit for resectional surgery or general anaesthesia, fixation of

the volved sigmoid loop by percutaneous endoscopic sigmoido-

pexy has been advocated as a less invasive management plan.

The sigmoid loop must be decompressed and derotated first.

Then employing two or three percutaneous endoscopic gastro-

stomy (PEG) tubes or equivalent7 the redundant loop of bowel

can be triangulated and fixed.

Acquired megacolon/megarectum

Definition: An acquired megacolon occurs in adults who develop

chronic abnormal distension of the colon including the rectum

down to the level of the anal sphincters.

Incidence and aetiology: Because many cases are asymptomatic,

the true incidence of this condition is unknown. Those affected are

usually elderly with poor mobility and have many characteristics

� 2011 Elsevier Ltd. All rights reserved.

INTESTINAL SURGERY II

in common with individuals prone to sigmoid volvulus as

described above. Often no significant previous history of bowel

disturbance is reported although a history of regular laxative use

for constipationmay be given. Themegacolon is presumed to have

developed insidiously over years. For many years it has been

understood that progressive proximal distension and faecal

loading of the sigmoid colon predisposes to acute presentation

with sigmoid volvulus.8 Histology of the megacolon confirms the

presence of ganglion cells as distinct from the aganglionic findings

in Hirschprung’s disease.

Clinical presentation: This is similar to sigmoid volvulus.

However, the difference can be recognized by an intelligent rectal

examination when the examining digit enters a voluminous

empty rectum. Investigations are as outlined above, taking

particular care to ensure that the serum potassium and calcium

levels are not abnormally low.

Management: In addition to the general measures of symptom

control and rehydration, steps should be taken to ensure elec-

trolytes are maintained in balance particularly serum potassium

which may be chronically depleted. Regular, preferably daily,

rectal evacuation should be encouraged by means of stimulant

laxatives, suppositories, enemas, rectal examinations or procto-

scopy, even if only to release flatus.

Surgical options: The treatment for megacolon is primarily

conservative. However, these measures may fail and a fit patient

may be considered for a resection (usually subtotal colectomy)

with a primary anastomosis or stoma. When megacolon precedes

or co-exists with a sigmoid volvulus, the megacolon may not be

appreciated until the abdomen is open at surgery for volvulus.

The true diagnosis becomes obvious as the proximal and distal

bowel either side of the volved segment are both grossly dis-

tended. Following resection of the volved section of sigmoid

colon, a stapled anastomosis will not be possible due to the

diameter and thickness of the chronically distended bowel wall.

Faced with this situation it is tempting to perform a Hartmann’s

procedure or double-barrelled colostomy, however a hand-

sutured anastomosis without bowel preparation fares well

(second author’s personal observation). A one-stage procedure

needs to be combined with plans to keep the rectum evacuated as

described above.

Pseudo-obstruction

Definition: Acute colonic pseudo-obstruction, known as Ogil-

vie’s syndrome, is characterized by gross dilatation of the large

bowel in the absence of mechanical obstruction.

Incidence and aetiology: The exact incidence of colonic pseudo-

obstruction is unknown. It most commonly affects those inmiddle

age and is slightly more common in males (60%). Predisposing

factors include surgery particularly hip surgery, caesarean section,

and surgerywhich traumatizes the spine or retro peritoneum; drug

associated gastrointestinal hypomotility (e.g. clozapine used to

manage schizophrenia) probably through its anticholinergic and

antiserotonergic properties,9 and opiates; electrolyte imbalance

particularly low sodium and potassium; and scleroderma.

SURGERY 29:8 389

Trauma, infection and cardiorespiratory disease have also been

implicated. The cause of acute colonic pseudo-obstruction is

thought to be due to an alteration of the normal autonomic regu-

lation of colonic motor function e either by excessive para-

sympathetic suppression reducing colonic contractility or

excessive sympathetic stimulation decreasing motility.

Clinical presentation: Individuals with colonic pseudo-

obstruction present with the signs and symptoms of large bowel

obstruction namely abdominal distension, pain, nausea and

vomiting. Symptoms tend to develop over 3e7 days. When the

condition develops post operatively it is usually around day 5.

Clinical examination reveals a distended tympanitic abdomen and

bowel sounds may be present. Abdominal tenderness and fever,

when present, suggest ischaemia or perforation, and it is important

to realize that these changes can develop with this diagnosis.

Baseline blood tests may show electrolyte imbalance. A rising

CRP and WBC are indicative of ischaemia or perforation.

A plain abdominal X-ray will reveal dilated large bowel with

or without associated small bowel dilatation. In the absence of

a rectal lesion, the presence of dilatation right down to the

rectum supports a diagnosis of pseudo-obstruction. A caecal

diameter greater than 12 cm is associated with the risk of

perforation (as is the case in mechanical colonic obstruction).

A mechanical obstruction will need to be excluded by water

soluble contrast enema or computed tomography. The latter

investigation will also help exclude toxic dilatation secondary to

colitis.

Management: Having confirmed the diagnosis of pseudo-

obstruction management is conservative. Electrolyte distur-

bance should be corrected. Drugs should be reviewed and

medications affecting colonic motility discontinued. Laxatives

should be avoided and, traditionally, mobilization has been

encouraged. The distended colon may need to be repeatedly

decompressed by insertion of a rectal tube or by employing the

colonoscope.10 Colonoscopy allows the colonic mucosa to be

inspected for necrotic patches and ideally the caecum should be

visualized. With these measures approximately 85% of cases will

resolve within 48 hours.11

Neostigmine an acetylcholinesterase inhibitor has been

successfully used to enhance colonic motor activity in cases of

pseudo-obstruction.12 A dose of 2 mg is given intravenously over

3e5 minutes. It has a rapid onset of action and cardiac monitoring

is recommended due to potential bradycardia. Acetylcholines-

terase inhibitors can be given orally where they have a longer

action, either Neostigmine at a dose of 15 mg, or pyridostigmine

started at 10mg, both twice daily.13 Once a regular bowel habit has

been established they may be discontinued. Contraindications

include the presence of ischaemia or perforation, uncontrolled

arrhythmias, bronchospasm and renal insufficiency.

Other medical therapies have been reported as having anec-

dotal success such as erythromycin and 5-HT receptor agonists

including ondansetron, but these have a pro-kinetic effect on the

stomach and small bowel and have not been proven to be of

benefit in colonic pseudo-obstruction.14

Surgery is obviously necessary in the presence of ischaemia or

peritonitis. However, significant morbidity andmortality has been

reported in relation to bowel resection for pseudo-obstructionwith

� 2011 Elsevier Ltd. All rights reserved.

INTESTINAL SURGERY II

an overall mortality rate of 15%, rising to 27.5% in association

with clozapine9 and 40% in the presence of spontaneous

perforation.11 A

REFERENCES

1 Cirocchi R, Farinella E, La Mura F, et al. The sigmoid volvulus: surgical

timing and mortality for different clinical types. World J Emerg Surg

2010; 5: 1.

2 Brown SR, Adam IJ. Intestinal obstruction. Surgery 2002; 20: 157e64.

3 Connolly S, Brannigan AE, Heffeman E, Hyland JMP. Sigmoid volvulus:

a 10-year audit. Ir J Med Sci 2002; 171: 216e7.

4 Larkin JO, Thekiso TB, Waldron R, et al. Recurrent sigmoid volvulus e

early resection may obviate later emergency surgery and reduce

morbidity and mortality. Ann R Coll Surg Engl 2009; 91: 205e9.

5 Safioleas M, Ahatziconstantinou C, Felekouras E, et al. Clinical

considerations and therapeutic strategy for sigmoid volvulus in the

elderly: a study of 33 cases. World J Gastroenterol 2007; 13: 921e4.

6 Raveenthiram V, Madiba TE, Atamanalp SS, et al. Volvulus of the

sigmoid colon. Colorectal Dis 2010; 12: 712.

SURGERY 29:8 390

7 Pinedo G, Kirberg A. Percutaneous endoscopic sigmoidopexy in

sigmoid volvulus with T-fasteners: report of two cases. Dis Colon

Rectum 2001; 44: 1867e9.

8 Lockhart-Mummery P. Volvulus of a Mega-colon. Proc R Soc Med

1933; 26: 1451.

9 Palmer SE, McLean RM, Ellis PM, et al. Life-threatening clozapine-

induced gastrointestinal hypomotility: an analysis of 102 cases. J Clin

Psychiatry 2008; 69: 759e68.

10 Rex DK. Colonoscopy and acute colonic pseudo-obstruction.

Gastrointest Endosc Clin N Am 1997; 7: 499e508.

11 Saunders M. Acute colonic pseudo-obstruction. Curr Gastroenterol

Rep 2004; 6: 410e6.

12 Ponec RJ, Saunders MD, Kimmey MB. Neostigmine for the treatment

of acute colonic pseudo-obstruction. N Engl J Med 1999; 341:

137e41.

13 O’Dea CJ, Brookes JH, Wattchow DA. The efficacy of treatment of

patients with severe constipation or recurrent pseudo-obstruction

with pyridostigmine. Colorectal Dis 2010; 12: 540e8.

14 De Giorgio R, Knowles CH. Acute colonic pseudo-obstruction. Br J

Surg 2009; 96: 229e39.

� 2011 Elsevier Ltd. All rights reserved.