Recommendations
Urgent
Check for signs of peritonitis and severe systemic illness or clinical deterioration, such as fever, leukocytosis, tachycardia, metabolic acidosis, or continuous pain.[11]
These may indicate that immediate surgery is required (i.e., for peritonitis, strangulated hernia, or bowel ischaemia).
They may indicate sepsis or acute kidney injury, which require treatment in their own right. See our topics Sepsis and Acute kidney injury for more information.
Check for faeculent vomiting. It is a sign that urgent management is required.
Assess whether urgent fluid resuscitation is needed. Indicators include:[13]
Systolic blood pressure less than 100 mmHg
Heart rate more than 90 beats per minute
Cold peripheries
Capillary refill time more than 2 seconds
Respiratory rate more than 20 breaths per minute
National Early Warning Score (NEWS2) of 5 or more ( NEWS2 Opens in new window)
Passive leg raising suggests fluid responsiveness.
In the community, if you suspect small bowel obstruction, refer the patient urgently to secondary care.[4]
Key Recommendations
The classical symptoms of small bowel obstruction are intermittent abdominal pain, distention, vomiting, nausea, and constipation (which can be absolute or partial).[4][14][15]
Use the following factors to establish the likelihood of adhesions, although the presence of adhesions can only be definitively confirmed by surgery.[14]
A history of previous episodes of bowel obstruction due to adhesions is a risk factor for adhesive bowel obstruction.[14]
Previous episodes of adhesions make this diagnosis more likely.
Previous surgery and conditions such as pelvic inflammatory disease, diverticulitis, and appendicitis can cause bowel adhesions.
Postoperative small bowel obstruction must be differentiated from postoperative ileus.[15]
Bowel obstruction may occur without a history of prior surgery.
Test for raised inflammatory markers (white blood cell count, C-reactive protein, platelet count).[4][14]
Check urea and electrolytes.[4][14] Significant fluid shifts can occur, resulting in metabolic acidosis, hypokalaemia, and acute kidney injury.
Investigate further, if needed, using blood gas analysis and lactate assay to look for poor tissue perfusion.[4]
Order a computed tomography scan of the abdomen and pelvis with oral and intravenous contrast according to local hospital protocols.[4][11][14][16] This will confirm small bowel obstruction or exclude other diagnoses.
Look for evidence of closed-loop small bowel obstruction or vascular compromise that require expedited surgical management.
Consider water-soluble contrast study in patients who fail to improve after 48 hours of non-operative management. The passage of contrast into the colon is a strong indication that surgery is unlikely to be required.[11]
Small bowel obstruction is a mechanical interruption of the patency of the gastrointestinal tract. The classical symptoms are intermittent abdominal pain, distention, vomiting, nausea, and constipation.[4][14][15]
Constipation can be:
Absolute – passage of neither stool nor flatus
Partial – passage of flatus and small amounts of stool.
Abdominal distention is a common sign, though it may be absent with more proximal obstruction.[15]
Postoperative pain or analgesia may mask the presenting symptoms.[15]
Obstruction may be partial or complete.
Faeculent vomiting suggests established obstruction that is relatively unlikely to settle without surgical intervention. It is also an indication that significant fluid shifts, dehydration, and nutritional insufficiency may be present.
Peritonitis and signs of clinical deterioration such as fever, leukocytosis, tachycardia, metabolic acidosis, or continuous pain may indicate a need for urgent surgical exploration.[11]
Not all of these symptoms may be present. In older patients, pain is often less prominent.[14]
Differentiate postoperative small bowel obstruction from postoperative ileus.[15] See our topic Ileus.
Consider a persistent ileus or obstruction if the patient fails to eat, pass flatus, or evacuate their bowel within 5 days after abdominal surgery.
If the patient has already passed flatus or stool and then ceases to do so, an obstruction may be a more likely cause than a persistent postoperative ileus.[15]
Practical tip
Stools may still be present in the rectum of patients with a relatively high obstruction who are admitted early after onset of symptoms. Patients may pass some liquid stool or mucus and report this as diarrhoea. It is vital to establish the volume as well as the looseness of a patient’s bowel motions. A low volume of loose stool is not diarrhoea. It is dangerous to conclude that a patient has gastroenteritis without clearly establishing the presence of true diarrhoea.
Take a detailed symptom history.
Ask about the onset and note the duration of the patient’s symptoms.
Ask about the nature of their symptoms:
Failure to pass stools or flatus
Any increase in stool frequency and decrease in volume
Fever
Abdominal pain, often described as cramping, intermittent, and severe. Ask about the frequency and duration. Constant pain is a sign of possible ischaemia[4]
Abdominal distention[15]
Nausea or vomiting – may occur after onset of pain; patient may be bilious
Urgently manage any patient with faeculent vomiting.
Use the following factors to establish the likelihood of adhesions, although the presence of adhesions can only be definitively confirmed by surgery.[14]
A history of previous episodes of bowel obstruction due to adhesions is a risk factor for adhesive bowel obstruction.[14]
Previous episodes of adhesions make this diagnosis more likely.
Previous surgery and conditions such as pelvic inflammatory disease, diverticulitis, and appendicitis can cause bowel adhesions.
Ask about risk factors, including the following.
Previous abdominal surgery
This can lead to intra-abdominal adhesions that may cause obstruction. Open abdominal surgery carries a greater risk of intra-abdominal adhesion-related small bowel obstruction compared with laparoscopic surgery.[5][6][7] A history of previous episodes of bowel obstruction due to adhesions is a risk factor for adhesive bowel obstruction.[14]
Hernias
Inguinal, ventral incisional, umbilical, and parastomal hernias can lead to incarceration and intestinal obstruction.
Crohn's disease
Crohn’s disease can lead to the formation of an inflammatory phlegmon or fibrotic strictures that may obstruct the intestine. Crohn's strictures may give symptoms of intermittent obstruction.
Intestinal malignancy
A malignancy can cause an intestinal blockage, either from primary tumour or from metastases.
Appendicitis
This can lead to obstruction of the intestine due to the formation of an inflammatory phlegmon/abscess.
Foreign-body ingestion
This can cause a mass effect in the intestinal lumen and prevent the passage of intestinal contents.
Gallstone ileus
A mechanical obstruction results from a large gallstone passing through a cholecystoduodenal fistula. Less than 1% of cases of intestinal obstruction are derived from this aetiology.[17]
Malrotation of the gut
This is common as a paediatric condition, but rarely presents in adulthood.[18]
Intussusception
Occurs infrequently in adults and differs from childhood intussusception in its presentation and aetiology.[19]
Volvulus
A rare cause of an acute abdomen in adults.[20]
Ask about reproductive history and the possibility of pregnancy.
Ask about current or recent medication and alcohol consumption.
Check for pyrexia and tachycardia, and assess pain. These are signs of potential ischaemia, strangulation, or an obstructed hernia, all of which are indications for early surgery.[4]
Use an Airway, Breathing, Circulation, Disability, Exposure (ABCDE) approach to assess the patient.[21]
Signs of haemodynamic instability, including hypotension, tachypnoea, tachycardia, and low urine output, may indicate sepsis or shock, which require urgent management.[22] See our topics Sepsis and Shock for more information.
Remember that the patient’s status can change quickly.
Involve your senior team when needed.
Assess hydration. Check for signs of dehydration, such as:[14]
Tachycardia
Dry mucous membranes; check tongue and mouth
Hypotension
Altered mental state; drowsiness.
Assess the patient’s nutritional status using a score, such as the Malnutrition Universal Screening Tool (MUST).[16] MUST calculator Opens in new window MUST is a score that can be used to detect over- and under-nutrition and can be applied to adult patients in various care settings.[23]
Assess frailty using a score, such as the Rockwood frailty score.[16][24] Rockwood Clinical Frailty Scale Opens in new window
Abdominal examination
Examine the patient’s abdomen. Palpate for any mass, hernia, or tenderness.[4][14]
If you suspect a hernia, look for significant skin changes at the site, such as discoloration or erythema.
Look for scars indicative of prior surgery.
Localised or generalised guarding may indicate impending or actual perforation and are indications for urgent surgery in a patient with small bowel obstruction.[4][14]
Examine the groin for the presence of irreducible and/or strangulated hernias.
Practical tip
It is easy to miss a small obstructing (i.e., femoral) hernia in an obese patient. This underlines the importance of an early abdominal computed tomography scan in such patients.
Order a computed tomography (CT) scan of the abdomen and pelvis with oral and intravenous contrast according to local hospital protocols.[4][11][14][16]
Check the patient’s kidney function, as acute kidney injury may be a contraindication to a CT scan using a contrast agent.[16][25]
Use the CT scan to identify the level and cause of the obstruction, and therefore determine the management plan.[4]
CT scans have a high (approximately 90%) accuracy in predicting intestinal strangulation and therefore the need for urgent surgery.[14] CT is also useful in diagnosing ischaemia.[26]
The detail that a CT provides with regard to the severity and aetiology of the obstruction will help to establish the management plan.[11]
Do not use plain radiography of the chest and abdomen. It is unreliable and should only be used when CT is unavailable. Abdominal radiographs can be extremely difficult to interpret. Consult with radiology.[4]
Consider water-soluble contrast study in patients who fail to improve after 48 hours of non-operative management. The results may help predict the need for surgery.[11][27]
Evidence: Water-soluble contrast
Water-soluble contrast can be used to diagnose adhesive small bowel obstruction. There is debate around its therapeutic use.
There are clear benefits of using oral water-soluble contrast to predict the need for surgery.
A systematic review (published in 2016) found 13 diagnostic studies (838 patients). The presence of contrast in the colon on abdominal x-ray 4 to 36 hours after administration had a sensitivity of 92% and a specificity of 93% in predicting resolution of the obstruction without surgery. Diagnostic accuracy increased if the x-ray was taken after 8 hours.[27]
There is debate around the use of oral water-soluble contrast to treat adhesive small bowel obstruction, and further evidence has made this more controversial.
The systematic review above (published 2016) also considered the therapeutic role of oral water-soluble contrast and found 12 studies (653 patients). Administration of water-soluble contrast reduced the need for surgery (odds ratio 0.55, P=0.003), time to resolution (weighted mean difference [WMD] -28.25 hours, P <0.00001), and hospital stay (WMD -2.2 days, P <0.00001). There were no significant adverse effects on morbidity or mortality.[27]
A 2017 randomised trial (242 patients) compared gastrografin with a saline placebo. The need for surgery was similar (24% with gastrografin versus 20% with saline). Length of hospital stay was not significantly different (3.8 days with gastrografin versus 3.5 days with saline, P=0.19).[28]
A systematic review (search dates January 2000 to November 2018) included 9 studies in 879 patients in its meta-analysis. The administration of oral water-soluble contrast reduced the length of hospital stay (WMD -0.15 days, P <0.0001). This difference, which amounts to 3.6 hours, was not considered clinically significant. Oral water-soluble contrast did not reduce the need for surgery (relative risk [RR] 0.84, P <0.009) or mortality (RR 0.99, P <1.000).[29]
Adverse events are uncommon. Serious but rare adverse events with gastrografin administration include anaphylaxis and aspiration pneumonia.[30] Due to its iodine content, gastrografin is contraindicated in patients with hyperthyroidism. It is also contraindicated in pregnant women.
Use a multidetector CT scanner and multiplanar reconstruction, if available. They aid in the diagnosis and localisation of small bowel obstruction.[11][31]
Laboratory investigations are key to understanding and managing the metabolic consequences of small bowel obstruction.
Perform the following blood tests.
Full blood count
White blood cell count >10,000/mm 3 is a non-specific marker of inflammation.[14]
A low haematocrit may indicate blood loss caused by an underlying disease or into an obstructed bowel, a potential sign of intestinal necrosis.
Electrolytes
An elevated urea and creatinine may indicate dehydration.
Measure and document hydration status in all patients presenting with symptoms of acute bowel obstruction in order to minimise the risk of acute kidney injury.[16]
Other electrolyte imbalances are often seen in patients with bowel obstruction – in particular, low potassium.[4][14]
Patients on renal dialysis can have symptoms of ileus due to electrolyte imbalance.[32]
C-reactive protein (CRP)
Urea/creatinine ratio
Elevated levels suggest dehydration/hypovolaemia and increased risk for development of severe disease.
Dehydration may result in acute kidney injury.[14]
Serum lipase or amylase
Use serum lipase testing (if available) in preference to serum amylase.[33][34]
Serum lipase and amylase have similar sensitivity and specificity but lipase levels remain elevated for longer (up to 14 days after symptom onset versus 5 days for amylase), providing a higher likelihood of picking up a diagnosis of pancreatitis in patients with a delayed presentation.[35]
A result >3 times the upper limit of the normal range confirms the diagnosis of acute pancreatitis in a patient with acute upper abdominal pain.[36]
Acute pancreatitis is an important differential diagnosis for a patient presenting with acute, severe abdominal pain.
Glucose
Clotting, group and save, or cross-match
If you anticipate surgery.[4]
Arterial blood gases (including lactate)[4]
An elevated lactate reading indicates poor tissue perfusion. It is not diagnostic for intestinal ischaemia.
Any evidence of bowel ischaemia, strangulation, or an obstructed hernia is an indication for early surgery.[4]
Also perform the following investigations.
Urine or serum beta–human chorionic gonadotrophin (HCG) in women of childbearing age.
Consult with gynaecology if positive.[4]
Urinalysis
Perform if urinary symptoms are present; do not diagnose a urinary tract infection by urinalysis alone.
Perform an ECG on patients over 50 years of age, or those with a history of cardiac disorder.[4]
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