Recommendations
Urgent
Identify large bowel obstruction as early as possible in any patient with abdominal pain and a change in bowel habit. It is a life-threatening surgical emergency.[3]
Arrange an urgent computed tomography (CT) scan of the abdomen and pelvis to be performed as soon as possible.[2][3][23] Use CT to differentiate genuine mechanical obstruction from pseudo-obstruction.[24]
CT may show evidence of a closed loop obstruction, which is a surgical emergency.
Identify peritonitis, as this requires urgent management.[3] Look for an acutely ill patient, presenting with fever, tachypnoea, tachycardia, and confusion.[5]
Palpate for tenderness over the caecum as this may indicate imminent perforation.[3] If detected in time, it can be managed before perforation occurs. Perforation is associated with a high mortality rate.[3]
Consider bowel perforation in a patient who acutely deteriorates.
Think ‘Could this be sepsis?’ based on acute deterioration in an adult patient in whom there is clinical evidence or strong suspicion of infection.[25][26][27]
Use a systematic approach, alongside your clinical judgement, for assessment; urgently consult a senior clinical decision-maker (e.g., ST3 level doctor in the UK) if you suspect sepsis.[25][26][28][29]
Refer to local guidelines for the recommended approach at your institution for assessment and management of the patient with suspected sepsis.
See Sepsis in adults.
Key Recommendations
The classical signs and symptoms are intermittent abdominal pain, distention, vomiting, nausea, and absolute constipation.[3] Perform blood tests (full blood count, electrolytes, urea/creatinine ratio, C-reactive protein, glucose) to understand and manage the metabolic consequences of large bowel obstruction.
Establish whether there is continuous pain. This may indicate bowel ischaemia.[3] Bear in mind that cessation of pain may be an indication of deterioration.
Aim to ultimately diagnose the underlying cause of the obstruction; specifically consider malignancy, benign stricture, pseudo-obstruction, and volvulus, as well as other more unusual mechanisms.
Large bowel obstruction is a life-threatening mechanical interruption of the patency of the gastrointestinal tract. The classical signs and symptoms are intermittent abdominal pain, distention, vomiting, nausea, and absolute constipation.[3] Continuous abdominal pain may indicate bowel ischaemia.[3]
Urgently exclude peritonitis and septic shock in an acutely unwell patient presenting with fever, tachycardia, tachypnoea, and confusion.[5] This may indicate a perforated bowel. Look for a tender abdomen, guarding, and absent bowel sounds.[5]
Practical tip
Sepsis
Consider bowel perforation in a patient who acutely deteriorates. Think 'Could this be sepsis?' based on acute deterioration in an adult patient in whom there is clinical evidence or strong suspicion of infection.[25][26][27] See Sepsis in adults.
The patient may present with non-specific or non-localised symptoms (e.g., acutely unwell with a normal temperature) or there may be severe signs with evidence of multi-organ dysfunction and shock.[25][26][27]
Remember that sepsis represents the severe, life-threatening end of infection.[30]
Use a systematic approach (e.g., National Early Warning Score 2 [NEWS2], alongside your clinical judgement, to assess the risk of deterioration due to sepsis.[25][26][27][28][31] Consult local guidelines for the recommended approach at your institution.
Arrange urgent review by a senior clinical decision-maker (e.g., ST3 level doctor in the UK) if you suspect sepsis:[29]
Within 30 minutes for a patient who is critically ill (e.g., NEWS2 score of 7 or more, evidence of septic shock, or other significant clinical concerns)
A patient is also at high risk of severe illness or death from sepsis if they have a NEWS2 score below 7 and a single parameter contributes 3 points to their NEWS2 score and a medical review has confirmed that they are at high risk.
Within 1 hour for a patient who is severely ill (e.g., NEWS2 score of 5 or 6) or within 1 hour of any intervention for suspected sepsis (antibiotics/fluid resuscitation/oxygen) if there is no improvement in the patient’s condition.
Follow your local protocol for investigation and treatment of all patients with suspected sepsis, or those at risk. Start treatment promptly. Determine urgency of treatment according to likelihood of infection and severity of illness, or according to your local protocol.[29][31]
In the community and in custodial settings: refer for emergency medical care in hospital (usually by blue-light ambulance in the UK) any patient who is acutely ill with a suspected infection and is:[26]
Deemed to be at high risk of deterioration due to organ dysfunction (as measured by risk stratification)
At risk of neutropenic sepsis.
See Sepsis in adults.
Take a careful history and detailed examination. See History and Examination below. The obstruction may be due to colorectal cancer or other non-malignant causes. Also consider constipation and faecal impaction developing in hospitalised patients.
Frequency of possible causes of large bowel obstruction[3]
Cause | Frequency |
|---|---|
Malignancy | 60% |
Diverticular strictures | 20% |
Volvulus | 5%[32] |
Acute sigmoid volvulus is torsion of the sigmoid colon around its mesenteric axis.[9][32] If not diagnosed and treated, it can result in life-threatening complications, such as bowel ischaemia, gangrene, and perforation.[32]
Aim to differentiate a mechanical obstruction from colonic pseudo-obstruction. Several conditions are associated with the development of colonic pseudo-obstruction. These include chest infection, myocardial infarction, renal failure, and Parkinson’s disease. Colonic pseudo-obstruction is also associated with trauma, recent major orthopaedic surgery such as hip replacement, the use of neuroleptics or opiates, and metabolic disturbances.[1][24] However, it is still important to rule out a mechanical obstruction in these patients. Use a CT scan to differentiate the two.[24] See Imaging below.
Urgently investigate and refer to a specialist any patients presenting with symptoms of colorectal cancer. These include:[19]
Abdominal pain
Abdominal mass
Change in bowel habit
Rectal bleeding or mucus
Microcytic anaemia
Weight loss.
Approximately 30% of colorectal cancer patients initially present to an emergency care setting.[3] See our topic Colorectal cancer.
Take a detailed symptom history.
Ask about the onset, and note the duration, of the patient’s symptoms.
A more abrupt onset might indicate a volvulus. A longer history of symptoms, accompanied by a change in bowel habit, might indicate a malignant cause.[3]
Ask about the nature of the symptoms.
Abdominal pain, often described as cramping, intermittent, and severe
Assess pain at presentation and throughout the admission.[6][23]
Establish whether there is continuous pain - this may indicate bowel ischaemia.[3]
Bear in mind that cessation of pain may be an indication of deterioration. There is anecdotal evidence that the bowel muscle becomes overstretched to a point that the muscle contractions causing the colicky pain cease.
Abdominal distention[3]
Look for abdominal distention on examination.[5]
The caecum is the commonest site of perforation through back pressure. Look for localised tenderness in the right iliac fossa as a sign that the underlying caecum is tearing. If found, investigate and treat urgently.
Nausea or vomiting[3]
Change in bowel habit
Ask about a change in bowel habit, such as complete failure to pass faeces or flatus.[5]
This usually occurs suddenly and is a dramatic change for the patient.
Some patients can continue to pass small volumes of stool or flatus in the early stages.
Stay vigilant for the combination of a dramatic reduction in stool volume associated with colicky abdominal pain.
A longer history of symptoms, accompanied by a change in bowel habit, might indicate a malignant cause.[3]
Rectal bleeding
Ask whether there is any rectal bleeding or blood in the stool.
Fever
May indicate an urgent complication of bowel obstruction, such as septic shock or impending perforation.[5]
May arise from concurrent illness or be implicated in a rarer cause of obstruction such as pelvic abscess or inflammatory bowel disease.
Tenesmus
Can imply rectal malignancy, inflammatory bowel disease, or radiotherapy-induced strictures.
Take a medical history. Ask about the following.
Colorectal adenomas or polyps
Patients with colorectal adenomas or polyps may go on to develop colorectal cancer.[19]
Current or previous malignancy
This could include an abdominal or gynaecological malignancy.
Ask about any signs and symptoms of an undiagnosed malignancy, such as rectal bleeding, recent weight loss, or a change in bowel habit.
Diverticular disease
May be a cause of strictures.
Inflammatory bowel disease
Current or previous hernia
A rare cause of large bowel obstruction.
Examine hernial orifices to detect an obstruction secondary to an irreducible hernia; most commonly seen in small bowel obstruction. See our topic Small bowel obstruction.
Gynaecological conditions
Previous benign or malignant masses.
Pelvic abscess.
Endometriosis is a rare cause of bowel obstruction.
Diabetes
Diabetes is associated with a 30% higher risk of colorectal cancer.[19]
May predispose the patient to colonic volvulus or pseudo-obstruction.
Gut motility is altered in diabetes and is associated with autonomic dysfunction.
Previous abdominal surgery
May predispose the patient to colonic volvulus.
May indicate an ischaemic colonic stricture.
In particular, a previous colorectal resection has a low risk of anastomotic stricture, a rare cause of large bowel obstruction.
Megacolon
Megacolon from any cause may predispose the patient to colonic volvulus owing to the elongation of the colon on its mesentery.
Laxative abuse
Any condition that results in an elongated colon predisposes the patient to the development of colonic volvulus.
Typically these patients are constipated and may have abused laxatives in an attempt to improve their symptoms.
Previous radiotherapy
May be a cause of strictures.
Foreign body ingestion
A rare cause of bowel obstruction.
Ask about a family history.
Bowel cancers can be associated with hereditary factors.[19]
Establish the following lifestyle risk factors.
Age
For colorectal cancer, age-specific incidence rates increase steeply after age 50, with the highest rates above age 85 years.[19]
Obesity
Approximately 13% of bowel cancers in the UK have been linked to obesity.[19]
Diet
Consumption of red meat and processed meat has been associated with colorectal cancer.[19]
Alcohol consumption
Approximately 11% of bowel cancers in the UK have been linked to excessive alcohol consumption.[19]
Smoking
Approximately 8% of bowel cancers in the UK have been linked to tobacco smoking.[19]
Look for evidence of anaemia, dehydration, and weight loss.
Measure and document hydration status at presentation and throughout the admission.[6][23] Aim to minimise the risk of acute kidney injury.[6] See our topic Acute kidney injury.
Perform a cardiovascular and respiratory examination as preparation for surgery that is likely to be required.
Examine the patient’s abdomen.
Palpate for tenderness over the caecum as this may indicate imminent perforation.[3] Perforation is common in the caecum, when it occurs, as this is the thinnest-walled part of the large bowel.[1] If detected in time, it can be managed before perforation occurs. Perforation is associated with a higher mortality rate.[3]
The caecum is the commonest site of perforation through back pressure. Look for localised tenderness in the right iliac fossa as a sign that the underlying caecum is tearing. If found, investigate and treat urgently.
Look for abdominal distention or rigidity on examination.[5]
Rigidity implies peritonitis secondary to perforation.
Palpate for an abdominal mass, hernia, or tenderness.
Examine hernial orifices to detect an obstruction secondary to an irreducible hernia.
There may be hyperactive or absent bowel sounds.[5]
Perform a digital rectal examination in patients with colonic symptoms.[3]
Digital rectal examination can be used to diagnose low rectal cancer.[5]
Check for faecal impaction. This may mimic true bowel obstruction.[33] See our topic Constipation. Note the presence of hard faeces, which may indicate faecal impaction.
Note the presence of soft stools. This may indicate a partial obstruction.
An empty rectum may indicate a proximal obstruction.
In women, check for a pelvic mass suggestive of a gynaecological malignancy or abscess.
Computed tomography
Order an urgent computed tomography (CT) scan of the abdomen and pelvis to be performed as soon as possible.[2][6][24] Guidelines on acute abdominal pain from the Association of Surgeons of Great Britain recommend doing this within 24 hours.[3] However, in practice, CT for suspected large bowel obstruction should be performed sooner than that. Prompt radiological diagnosis helps to ensure admission to the correct specialty and avoid delays in treatment.[23]
Consider CT with intravenous contrast, according to local hospital protocols.[23]
Check the patient’s kidney function, as acute kidney injury may be a contraindication to a CT scan using a contrast agent.[23][34]
CT can be used to identify perforation and dilatation and stage malignant disease.[2][3][5] The detail that a CT scan provides with regard to the severity and aetiology of the obstruction will help to establish the management plan.
Use the CT scan to identify the level and cause of the obstruction, and therefore determine the management plan.[23]
Use CT to differentiate between obstruction and pseudo-obstruction.[24]
CT evidence of a non-adhesional cause (tumour, hernia, or volvulus) or evidence of bowel ischaemia is an indication for surgery.[3]
CT can show whether the ileocaecal valve is patent.
With gas trapped inside and continuing to enter the colon, pressure within the large bowel will continue to increase and cannot flow back into the small bowel. This is known as closed loop obstruction and is a surgical emergency. It leads to a rapid increase in distension and intraluminal pressure, with early vascular occlusion. It can cause ischaemia and result in perforation.[1]
In particular, perform a CT scan if the patient is over 50 and presenting with abdominal pain, due to the risk of occult malignancy in this group.[3]
Ultrasound
Ultrasound has been shown to have a comparable accuracy to CT scans in the detection of small bowel obstruction but diagnostic criteria and accuracy for large bowel obstruction are less well defined.[35] One proposed criteria include dilated large intestine (>4.5 cm) and presence of abdominal A-lines (gastrointestinal intraluminal air).[36]
Water-soluble contrast study
Consult radiology if considering water-soluble contrast study.
It is not frequently used in most UK hospitals. Water-soluble contrast study is less sensitive than CT for identifying perforation of the bowel.[3]
Compared with plain radiography, the addition of contrast (given to the patient as an enema) to the plain radiograph improves the diagnostic accuracy in suspected large bowel obstruction.[37]
Lower gastrointestinal endoscopy or flexible sigmoidoscopy
Use lower gastrointestinal endoscopy or flexible sigmoidoscopy to confirm a diagnosis of mechanical obstruction or to decompress a volvulus or pseudo-obstruction.[9] However, this can introduce more gas into the large bowel and increase the distention in the case of a stricture.
Plain radiography
Do not routinely use plain radiography of the chest and abdomen. It is unreliable and diagnosis usually requires further imaging with CT; it should only be used when CT is unavailable.[38] Abdominal radiographs can be extremely difficult to interpret. Consult with radiology.
Use imaging to confirm the diagnosis of obstruction. Use the results of laboratory investigations to understand and manage the metabolic consequences of large bowel obstruction.
Perform the following blood tests.
Full blood count[3]
White blood cell count >10,000/mm3 is a non-specific marker of inflammation. It may indicate bowel perforation or necrosis.[5]
Neutrophilia may indicate bowel perforation or necrosis.[5]
A low haematocrit may indicate blood loss caused by an underlying disease. Occasionally blood can be lost into an obstructed bowel, a potential sign of intestinal necrosis.
Iron deficiency anaemia may be a sign of colorectal cancer.[19]
Urgently investigate and refer men and non-menstruating women with iron deficiency anaemia, as 10% of such patients will have colorectal cancer.[19]
Electrolytes[3]
Electrolyte imbalances are often seen in patients with bowel obstruction – in particular, low potassium. This may be caused by fluid loss into the obstructed bowel or through vomiting.
Patients on renal dialysis can have symptoms of ileus due to electrolyte imbalance.[39]
C-reactive protein (CRP)[3]
Elevated CRP (>75 mg/L) may indicate inflammation.
Urea/creatinine ratio
Elevated levels suggest dehydration/hypovolaemia and increased risk for development of severe disease.
Dehydration may result in acute kidney injury.
Serum amylase/lipase
Can be elevated with any significant intra-abdominal event.
Glucose[3]
Clotting, group and save, or cross-match
If you anticipate surgery.[3]
Arterial blood gases (including lactate)[3]
An elevated lactate reading indicates poor tissue perfusion. It is not diagnostic for intestinal ischaemia.
Lactic acidosis may indicate perforation or necrosis.[5]
Any evidence of bowel ischaemia, strangulation, or an obstructed hernia is an indication for early surgery.[3]
Also consider the following investigations in specific circumstances.
Urine or serum beta–human chorionic gonadotrophin (hCG) in women of childbearing age.[3]
Consult with gynaecology if positive.
Urinalysis[3]
Electrocardiogram
Request for patients over 50 years of age, or those with a history of cardiac disorder.[3]
Perform as part of a standard cardiovascular examination in preparation for surgery.
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