Abdominal Pain (Adult, Chronic)

FGIDs are defined by the Rome Foundation as disorders of gut-brain interaction 2 and comprise a set of about 50 disorders characterised by persistent and recurring gastrointestinal symptoms. Many of these disorders include symptoms of abdominal pain, but other symptoms such as bloating, constipation and/or diarrhoea, nausea and vomiting may be present. Psychosocial disturbances are often associated.

The Rome Foundation has summarised diagnostic criteria for more than 50 types of FGID, in the ROME criteria - most recently in the ROME IV iteration 3 - based on symptoms and anatomical domains rather than physiological criteria , and classified by a combination of any of the following: motility disturbance , visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, and altered CNS processing 2-4

Symptom-based criteria are used to make a diagnosis, with judicious use of limited investigations in some patients.5

The commoner FGIDs that include abdominal pain as a usual dominant feature are Irritable Bowel Syndrome (IBS), Functional Dyspepsia, Centrally Mediated Abdominal Pain syndrome (formerly known as Functional Abdominal Pain Syndrome) and Functional Gallbladder and Sphincter of Oddi disorders 6. There are multiple syndromes and variables described by the Rome Foundation but only these four syndromes will be dealt with in this Pathway, being those where abdominal pain is often a dominant feature.

Irritable Bowel Syndrome is one of the Functional Gastro-intestinal Disorders (FGIDs) (or Gut-Brain Interaction disorders) defined by the Rome IV criteria72, 8 .  Essential criteria for diagnosis include:

• recurrent abdominal pain, occurring at least once per week for the past 3 months, with symptom onset at least 6 months before diagnosis.

• The pain should be associated with two or more of the following: 

• changes in defecation, stool frequency, or stool appearance, pain related to defecation.

IBS is classified into four subtypes: IBS with predominant constipation (IBS-C), IBS with predominant diarrhoea (IBS-D), IBS with mixed bowel habits (IBS-M) or IBS, unsubtyped. All of these are associated with abdominal pain.

Before diagnosing IBS, it is crucial to determine whether warning/alarm signs are present and investigate accordingly 9, 10. Warning (or alarm features) are as follows:

• onset of symptoms after the age of 50

• unintentional weight loss 

• overt gastrointestinal bleeding/blood in stool

• recent changes in bowel habits

• nocturnal passage of stools 

• palpable abdominal mass or lymphadenopathy

• family history of colon cancer or inflammatory bowel disease

• iron deficiency anaemia

• positive testing for faecal occult blood

In addition the American College of Gastroenterology Task force adds antibiotic use to its list of alarm features 11.

SEE Irritable bowel syndrome (suspected) for further details. 

The diagnostic criteria must include all of the following: 3, 12

1. Continuous or nearly continuous abdominal pain

2. No or only occasional relationship of pain with physiological events (e.g., eating, defecation or menses)

3. Pain limits some aspect of daily functioning

4. The pain is not feigned

5. Pain is not explained by another structural or functional gastrointestinal disorder or other medical condition

The criteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

This syndrome is a complicated heterogenous condition resulting from an interplay of physical stimuli with cognitive and emotional, psychosocial factors  12, 13.

The use of diagnostic tests will likely be determined on an individual patient basis, but the more invasive tests such as endoscopy and colonoscopy will probably be reserved for those patients with “alarm” symptoms or signs Irritable Bowel syndrome

The diagnostic criteria are as follows 3, 6:

• Post-prandial fullness

• Early satiety

• Epigastric pain or burning not associated with defaecation

• Absence of another medical condition (including at upper GI endoscopy) to explain the symptoms 

Criteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

However, symptoms alone are not reliable in distinguishing functional from organic causes of dyspepsia 14

Nevertheless, 80% of people with dyspepsia will be diagnosed with FD following endoscopy.15

The British Society of Gastroenterology guidelines on functional dyspepsia 16 make strong recommendations (albeit on the basis of low or very low quality evidence) that:

• most patients with dyspepsia will have functional dyspepsia (FD) as the underlying cause of their symptoms after investigation.

•  a full blood count is performed in patients aged ≥55 years with dyspepsia and coeliac serology in all patients with FD and overlapping irritable bowel syndrome (IBS)-type symptoms.

• in the absence of upper gastrointestinal alarm symptoms or signs, clinicians should diagnose FD in the presence of bothersome epigastric pain or burning, early satiation and/or postprandial fullness of greater than 8 weeks duration.

•  if no other upper gastrointestinal alarm symptoms or signs are reported, urgent endoscopy is warranted in patients aged ≥55 years with dyspepsia with weight loss, or those aged >40 years from an area at an increased risk of gastric cancer or with a family history of gastro-oesophageal cancer.

• non-urgent endoscopy is considered in patients aged ≥55 years with treatment-resistant dyspepsia or dyspepsia with either a raised platelet count or nausea or vomiting or low haemoglobin.

• urgent abdominal CT scanning is considered in patients aged ≥60 years with abdominal pain and weight loss to exclude pancreatic cancer.

It is also recommended on the basis of high level evidence that all other patients with dyspepsia are offered non-invasive testing for Helicobacter pylori (‘test and treat’) and, if infected, given eradication therapy.

Chronic abdominal wall pain (CAWP) is a relatively common and underdiagnosed and misdiagnosed cause of chronic abdominal pain 17, 18, estimated to be the cause of symptoms in 10-30% of patients with chronic abdominal pain 18. One study found that in patients referred with abdominal pain, chronic abdominal wall pain comprised 7.8 percent of a cohort of 1708 patients 19. Patients are often over-investigated for intra-abdominal visceral causes of their pain 18 19 .

There are various causes of CAWP, depending on which part of the abdominal wall is affected. The most frequent is Anterior Cutaneous Nerve Entrapment Syndrome (ACNES) 20. Terminal branches of lower thoracic intercostal nerves are ‘entrapped’ in abdominal muscles causing localized neuropathic pain that is usually experienced as ventral abdominal wall pain at the lateral edge of the rectus abdominis in a highly specific localised area.

Diagnosis is facilitated by the physician’s awareness of the condition and can be confirmed by history and physical examination. The latter identifies a localized small focus of tenderness and a positive Carnett test, in which tenderness stays the same or worsens when the patient tenses the abdominal muscles, suggesting abdominal wall pain 20. A local anaesthetic injection can confirm the diagnosis when there is 50% postprocedural pain improvement.

Ultrasound examination may help rule out other abdominal wall pathologies (such as hernias) and guide therapeutic injections to the trigger point. Other causes of CAWP include hernias and post-surgical complications as well as multiple more rare conditions 20.

Functional biliary pain is defined in the Rome IV criteria as follows 3:

Pain located in the epigastrium and/or right upper quadrant and all of the following:

1. Builds up to a steady level and lasts 30 minutes or longer

2. Occurring at different intervals (not daily)

3. Severe enough to interrupt daily activities or lead to an emergency department visit

4. Not significantly (<20%) related to bowel movements

5. Not significantly (<20%) relieved by postural change or acid suppression

In addition, the pain may be associated with, nausea and vomiting, radiation to the back and/or right infra subscapular region, waking from sleep.

The Rome Criteria categorise functional biliary disorders into Functional gallbladder disorder and Sphincter of Oddi (SO) Dysfunction.

This is defined by the Rome consensus as biliary pain in a patient with an intact gallbladder without stones or sludge 21.It is thus a diagnosis of exclusion. This must include the features of biliary pain Functional Gallbladder and Sphincter of Oddi disorders in addition to an absence of gallstones on imaging, or other structural abnormality. Ultrasound is the usual primary investigation, but endoscopic ultrasound is more accurate in detecting small calculi, sludge and small tumours.

The diagnosis is supported by a low ejection fraction on gallbladder scintigraphy and normal liver enzymes, conjugated bilirubin, and amylase/lipase. It should be noted that a delayed emptying of the gallbladder on cholecystokinin-stimulated cholescintigraphy (CCK-CS) lacks specificity for functional gallbladder disorder and its predictive value for selecting patients for cholecystectomy is uncertain.

SOD arises most commonly, but not exclusively, as recurrent biliary pain after cholecystectomy for cholecystolithiasis.

Biliary type pain is the most common symptom, but pancreatic pain or pancreatitis may also occur.

It is estimated that about half of such cases are due to fibrotic stricture of the SO, and half due to a motility/functional cause (“dyskinesia”).

The diagnosis of biliary SOD requires the exclusion of organic pathology such as  choledocholithiasis and ampullary/periampullary tumours .Pancreatic SOD may present with pancreatic pain related to recurrent episodes of pancreatitis; exclusion of other causes of “idiopathic” recurrent pancreatitis is required.

1. Functional Biliary Sphincter of Oddi Disorder

SOD causing biliary-type pain was previously classified into three types under the Milwaukee classification 21:

Type I : patients with a dilated bile duct and abnormal liver tests, 

Type II involves one of those criteria but not both,

Type III: have none of those criteria. 

Most patients with Type I prove to have organic stenosis of the sphincter rather than a functional disorder; these patients can benefit from sphincterotomy. A 2014 multicentre study examined sphincter ablation in type III patients and found no benefit 22. Sphincterotomy in such patients is associated with a significant morbidity. Endoscopic sphincterotomy is not advised for Type III SOD i.e. those patients with biliary pain but no abnormality of liver function tests or biliary dilatation23, 24.

The above classification has now been largely abandoned in favour of the functional ROME IV characterisation 3 which defines the criteria for functional biliary sphincter disorder as follows (and corresponds to Type II of the previous classification, described above) :

SOD must include the features of biliary pain Functional Gallbladder and Sphincter of Oddi disorders. In addition, elevated liver enzymes or dilated bile duct on imaging should be present (but not both), as well as an absence of bile duct stones on imaging, or other structural abnormality. Supportive features are: normal amylase/lipase (these may be raised in some episodes of pain); abnormal sphincter of Oddi manometry; hepatobiliary scintigraphy (value disputed).

For patients with biliary pain, the exclusion of organic biliary disease is required (for example, retained bile duct stones – especially in post-cholecystectomy patients; post-surgical biliary strictures; ampullary and periampullary tumours) or, particularly if the pain is atypical, non-biliary pathology.

Investigation of suspected Functional Biliary Sphincter of Oddi Disorder

Apart from standard laboratory tests, imaging may include the following:

Abdominal ultrasound and IV-contrast-enhanced multidetector CT are the first-line imaging tests. Ultrasound is reliable in diagnosing gallstones in patients with an intact gallbladder but neither US nor CT are reliable enough to exclude bile duct calculi (the reported sensitivity of ultrasonography is variable and ranges from 22% to 75% for common bile duct stones. MDCT has a sensitivity, ranging from 65% to 88% 25. US and CT are useful in the diagnosis of a variety of other causes of right upper abdominal pain (such as hepatic lesions).

Ampullary tumours are difficult to diagnose on US or CT but a dilated bile duct in the presence of abnormal liver function tests will lead to further investigation.

A mass lesion within the pancreas is better detected with CT than US.

It should be noted that dilatation of the common bile duct on ultrasound in a post-cholecystectomy patient is a difficult finding to interpret. There is mixed evidence as to whether the bile duct enlarges after cholecystectomy. In addition, increasing age and narcotic use causes bile duct dilatation. 21.

In the diagnosis of biliary pain, if first-line tests are negative or equivocal for organic disease, CT cholangiography, MRI/MRCP, EUS, Hepatic scintigraphy, endoscopy and ERCP are possible second line investigations:

There is a lack of randomised trials of these diagnostic tests, largely due to the absence of a suitable gold standard. 

Sphincter of Oddi manometry is not widely undertaken due to its significant morbidity (post-procedure pancreatitis in about 10%) 24, and its validity is uncertain 21.

CT Cholangiography

CT cholangiography provides excellent visualization of biliary anatomy and filling defects, with up to 95% sensitivity and specificity for choledocholithiasis. 

25 26. A major drawback of this technique is the associated risks of contrast-induced allergic reactions. In addition, the opacification of the bile ducts is dependent on liver function.

MRI/MRCP vs Endoscopic ultrasound in bile duct stone diagnosis:

The choice between these tests may depend on local availability and expertise 27 as they have similar accuracies. Both can be used to exclude bile duct stones, and peri-ampullary tumours as a cause of biliary pain.

A 2015 meta-analysis 28 reported the sensitivity and specificity of MRCP for bile duct calculi as 90% and 95%, respectively. A 2023 meta-analysis 29 comparing EUS and MRCP in the diagnosis of choledocholithiasis reported EUS to have pooled sensitivity and specificity of 96% and 92%, respectively. MRCP had pooled sensitivity and specificity of 85% and 90%, respectively. There was little difference concerning specificity, although EUS likely provides a higher sensitivity and accuracy for diagnosing choledocholithiasis, compared to MRCP.

EUS is also useful in excluding microlithiasis within the bile duct (defined as calculi <3mm in size) 30 which may be a cause of biliary pain 31.

However, MRI performed in conjunction with MRCP has the advantage over EUS of being able to visualise the entire liver to exclude hepatic causes of RUQ pain.

It is reasonable, therefore, to consider EUS and MRCP as complimentary.

Hepatic scintigraphy (Cholescintigraphy)

The transit time from hepatic hilum to duodenum is measured. This correlates to SO basal pressure. The results show variable sensitivity and specificity 21, 24 but may predict the outcome of sphincterotomy in SOD 24. A negative result does not exclude SOD.

ERCP

This may be performed concurrently to SO manometry, but as the latter is rarely performed, the question of ERCP as an exclusively imaging procedure is more relevant. ERCP is largely  reserved for patients who do need manometry or for those predicted to require endoscopic therapy 21.

ERCP can also be performed to enable microscopic examination of bile to exclude microlithiasis (see above). However, EUS is able detect microlithiasis less invasively.

1. Functional Pancreatic Sphincter of Oddi Disorder

The previous method of classifying Functional Pancreatic Sphincter disorders (the Milwaukee classification 32, 33) has now largely been superceded by the ROME IV criteria 3 which define the condition as:

• Documented recurrent episodes of pancreatitis (typical pain with amylase or lipase >3 times normal and/or imaging evidence of acute pancreatitis)

• Other aetiologies of pancreatitis to be excluded

• Negative endoscopic ultrasound

• Abnormal sphincter manometry

Diminished flow of pancreatic secretions through the Sphincter of Oddi (SO) may be caused by sphincter stenosis and /or sphincter dyskinesia 34. These conditions are included under the label of Sphincter of Oddi dysfunction and may lead to recurrent episodes of abdominal pain and pancreatitis.

SOD is regarded as a cause of idiopathic pancreatitis – acute or recurrent i.e., when all other possible causes have been ruled out - it is a diagnosis of exclusion 24.

The prevalence of SOD among patients with idiopathic recurrent acute pancreatitis or pancreatic pain is uncertain but is regarded as significant. 

Patients with unexplained episodes of pancreatitis are often found to have raised sphincter pressures 21. However, there is up to a 50% recurrence rate in 2 years of pancreatitis after sphincterotomy (versus 3.5 times the rate in those with raised pressures but without treatment). In a 2012 study of patients with SO dysfunction, there did not appear to be a difference in preventing recurrent episodes, whether only biliary sphincterotomy or a combination of biliary and pancreatic sphincterotomy was performed 35.

The diagnosis of pancreatic sphincter dysfunction as a cause of pancreatitis is, in an individual patient, one of exclusion. Apart from the major causes of recurrent

pancreatitis (eg alcohol, drugs, choledocholithiasis), more subtle causes (such as small ampullary or peri-ampullary tumours., intraductal tumours, Intraductal Papillary Mucinous Neoplasms, biliary sludge or microlithiasis) need to be excluded – often by a combination of imaging tests as described below.

Investigation of suspected Functional Pancreatic Sphincter of Oddi Disorder

Organic causes of pancreatic pain and recurrent acute pancreatitis (RAP) need to be excluded, including alcohol, drugs and biliary calculi as well as intrinsic pancreatic disease such as Intraductal Papillary Mucinous Neoplasms.

Some of these causes can be excluded by careful history taking. Biliary calculi are investigated as described above, in the section on Functional Biliary Sphincter of Oddi Disorder.

• Multidetector CT or MRI/MRCP may be performed for pancreatic disease as well as duodenoscopy and endoscopic ultrasound. 

Non-invasive methods of assessing sphincter dysfunction can be assessed by measuring the size of the pancreatic duct at MRI 34 before and after Secretin administration. Further research is required.

• Secretin-enhanced MRI: Although a 2007 study reported that results of secretin-enhanced MRI does not reliably correlate with sphincter manometry 36, it may predict the outcome of sphincterotomy. It may be useful for selecting patients with Type 2 SO dysfunction (Milwaukee classification) for sphincterotomy 36.

• Ultrasound with secretin enhancement (either transabdominal 37 or endoscopic ultrasound 38 has also been used but  with variable results and there is a lack of recent research data on this technique.

• Endoscopic ultrasound is recommended by the American Gastroenterology Association guidelines  in unexplained acute and recurrent pancreatitis 39. The guidelines also state that MRI/ MRCP is a reasonable complementary or alternative test dependent on local expertise and availability.

Endoscopic ultrasound is accurate in detecting small tumours and bile duct stones 30, as well as quite subtle changes of chronic pancreatitis39. In addition, a recent  study has shown that the diagnostic yield of EUS is higher than Secretin-enhanced MRCP in patients with idiopathic acute pancreatitis, in showing causes such as cholelithiasis, pancreas divisum and IPMN  40.

• Sphincter manometry (via the endoscope, often performed at the same time as ERCP) is controversial , given the relatively high incidence of post-procedure side-effects 24.

Sphincter of Oddi manometry reveals a hypertensive sphincter of Oddi pressure, with a basal biliary or pancreatic sphincter pressure > 40 mmHg in 15–72% of patients with RAP initially diagnosed as idiopathic 41.

However, although considered the gold standard test for SOD diagnosis, SO manometry requires skilled endoscopists and highly specialized equipment not widely available. It is associated with up to 30% of post-manometry pancreatitis, and is not confirmatory in ~ 13–40% of patients ultimately diagnosed with type I SOD 42. Therefore, SOM is nowadays rarely employed.

Endoscopic sphincterotomy remains controversial in this condition. A prospective randomized controlled trial 35 showed no difference between dual endoscopic sphincterotomy and biliary endoscopic sphincterotomy alone in preventing recurrent acute pancreatitis. 

Methods of treatment of patients with sphincter dysfunction, apart from sphincterotomy, include injection of Botulinum toxin into the sphincter, and a trial of temporary stenting 21.

In patients with known or suspected AAAs, the development of abdominal and/or back pain should be regarded as requiring emergency specialist referral 43, and may indicate aneurysmal instability, impending rupture, or a contained leak.

AAA patients may present or develop abdominal and /or back pain or present with peripheral embolization and/or mesenteric ischaemia.

Although the definition of symptomatic non-ruptured aneurysm varies, there may be tenderness on palpation,evidence of peripheral emboli with no other obvious source, or unexplained back or abdominal pain.

Symptomatic non-ruptured AAAs have a higher rupture risk than asymptomatic AAAs. If point-of-care Ultrasound is available, this should be performed urgently. If this is not available or is positive or equivocal, urgent specialist referral is required 43.

Following urgent specialist referral, patients with a symptomatic non-ruptured AAA may be considered for a brief period of rapid assessment and optimisation followed by urgent repair under optimal conditions (ideally during working hours) 44.

Chronic mesenteric ischaemia

Crohns disease (suspected)

chronic RUQ pain

bowel obstruction (suspected)

Irritable bowel syndrome (suspected)

Dyspepsia

Endometriosis (suspected)

Pelvic inflammatory disease (suspected)

Loin pain (renal colic)

chronic pancreatitis