Chronic lower abdominal pain or discomfort

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7 Chronic lower abdominal pain or discomfort

John Kellow

Case

A 35-year-old florist presents to her doctor because of a 6-year history of recurrent episodes of lower abdominal pain associated with an erratic bowel habit. Her symptoms have been present intermittently for this period but over the past 12 months have become more frequent and severe, with pain occurring every few weeks and lasting for 4-5 days. The pain is situated in the left iliac fossa and left hypochondrium, and has a cramping nature. The pain can cause her to cease her current activities. Her bowel habit is characterised by an alternating pattern of loose frequent motions for several days followed by a hard dry motion every few days with associated straining and a sensation of incomplete evacuation. She complains of abdominal bloating, which has become more of a problem recently, and this is often accompanied by visible abdominal distension. She has no ‘alarm’ symptoms, with her appetite and weight well-maintained and no evidence of blood or mucus in her stools. She has no other significant medical illnesses, is a non-smoker and eats a balanced diet. There is no family history of gastrointestinal disease. Physical examination is normal with no evidence of abdominal tenderness, mass or other abnormality. Rectal examination is normal.

The patient had undergone a normal colonoscopy 3 years ago when she had experienced a similar exacerbation of these symptoms. A full blood count, C-reactive protein level, and coeliac serology are normal. The doctor makes the diagnosis of irritable bowel syndrome (IBS) and explains the possible origin of symptoms to the patient. He reassures her that IBS does not lead to more serious disease, although it may have a chronic and relapsing course. The patient has tried various dietary modifications previously without any improvement in her symptoms. She has also used a number of antispasmodic agents, both prescription and over-the-counter, with little improvement in her symptoms. She uses an osmotic laxative during the constipation phase and this is of some benefit to her. Her doctor suggests instituting low-dose therapy with a tricyclic antidepressant agent for its potential effects as a ‘visceral analgesic’. After 1 month of this therapy, the patient has noticed a definite improvement in symptoms and is willing to continue the medication in the longer term. The doctor suggests she returns for review in a further 3 months to discuss the ongoing use of this therapy.

Introduction

Chronic or recurrent lower abdominal pain is a common symptom and often represents a source of frustration and confusion to both patient and physician. Because the management of the large number of different causes of such pain can be quite specific, it is important to make a positive diagnosis of the cause of the abdominal pain. A precise history is especially important in this respect. The commonest causes are irritable bowel syndrome (IBS) and related functional bowel disorders. The separate entity of functional abdominal pain syndrome accounts for a small but important proportion of cases. These functional gastrointestinal disorders represent a substantial source of morbidity and cost to the community.

History

Compared to acute abdominal pain, the origin of chronic abdominal pain is often more difficult to diagnose, because the characteristics of the pain tend to be less specific and can be difficult for patients to describe. For example, even the terms used by patients to describe chronic abdominal pain vary greatly. In particular, some refer to pain, while others to discomfort, fullness or even indigestion. Nevertheless a skilled physician can make an accurate diagnosis, or at least narrow the range of possible diagnoses, even before the physical examination. At the outset, it is important to remember that the experience of pain includes several components: (1) nociception, whereby a noxious stimulus conveys an impulsive centrally; (2) conscious perception of this sensation; (3) an affective response such as distress; and (4) a behavioural response. The essential features that need to be elicited in the history are described below.

Site, radiation and referral of pain

It is helpful to ask the patient to indicate with his or her hand where the pain is felt; this is best elicited during the physical examination with the patient in the supine position. If the site of the pain is midline, the region on the abdomen can give a clue to the origin. For example, pain from the small bowel tends to be periumbilical, whereas pain from the colon tends to be perceived in the lower abdomen. The more the painful area can be localised (e.g. to a finger-tip point), the more likely it is that the site reflects the origin of the painful stimulus. Radiation of pain can be characteristic of certain organs. For example, pancreatic pain can be referred to the back, whereas radiation to the groin occurs in disorders of the ureter and testicle. However, in functional bowel disorders, such as IBS, the radiation of pain—at least pain arising from the colon—can be not only to any of these sites but also to various extraabdominal areas; it may also shift in location at various times in the one patient.

Character, intensity and duration of pain

The nature or character of the pain is important to define, as certain disorders are associated with pain of a particular quality. Thus the pain of intestinal obstruction is usually cramping, whereas pain of inflammatory origin is often continuous in nature. Other descriptions can be suggested to the patient by the examiner, or the patient can be asked to relate the current pain to previous pains he or she may have experienced. The intensity or severity of pain does not always provide reliable information, as individual responses to a given painful stimulus vary: thus, while one patient may describe very severe pain, to another it may be mild in intensity. Moreover, the intensity of pain cannot differentiate between ‘functional’ and ‘organic’ disorders. Sometimes, however, associated signs and the manner in which the patient describes the pain can give clues to the intensity. Asking the patient to rate the pain on a numerical scale from one to ten can be used to compare the intensity of recurrent episodes of pain. The mode of onset of pain can be helpful; in general, chronic lower abdominal pain has a gradual onset, with a slow increase in intensity, when compared with the sudden onset of pain from mechanical or vascular causes. Some types of recurrent lower abdominal pain, however, can occur in discrete episodes of sudden onset.

The overall duration of pain is often an important indicator of the significance of the disorder causing the pain—thus, continuous pain that has been present for months or years, in a patient not obviously unwell, is usually functional in origin. When pain is recurrent, the timing (frequency and duration, time of day) is important to establish, Pain that wakes the patient from sleep may indicate an organic disorder, although it can occur in the functional bowel syndromes. In this context, it is important to determine whether the patient actually wakes because of pain, or whether other factors initially wake the patient.

Modifying factors

Factors that modify the pain are also important. Routinely, the relationship of pain to meals, bowel motions, exertion, menstruation and sexual intercourse should be obtained. A diary of the timing of pain in relation to meals and other activities can help both the patient and the doctor to determine provoking or relieving factors. Patients often state that eating exacerbates the abdominal pain, and in some instances this can provide discrimination, such as mesenteric ischaemia with ‘intestinal angina’. In general, however, the timing of pain in relation to food intake is not of great help in diagnosing disorders causing chronic lower abdominal pain. Similarly, the type of food consumed is often not of great relevance, although excessive ingestion of sugars, such as lactose present in milk products, and fructose and sorbitol present in fruits, some soft drinks and confectionery, can be important. Since fructose is poorly absorbed, large amounts can overwhelm the absorptive capacity of the small intestine, leading to bloating, abdominal discomfort, flatulence and diarrhoea. Relief of pain by bowel movements or by passing flatus is suggestive of a colonic origin for the pain; such relief is usually perceived rapidly, and is often short-lived.

The associations of the pain are relevant; for example, colonic pain can be temporally associated with a change in stool form or frequency, a key feature of IBS. Episodes of pain related to menstruation raise the possibility of pelvic inflammatory disease or endometriosis; it should be remembered, however, that abdominal discomfort from a wide variety of causes can be aggravated premenstrually, and alterations in stool pattern are also common at this time.

Musculoskeletal causes of pain can be exacerbated by different postures or exercise and relieved by rest, although once again this distinction cannot be relied upon. The patient can be asked to demonstrate the postures that can bring on the pain. Pain originating in the anterior abdominal wall is aggravated when the abdominal wall is tensed by, for example, raising the lower limbs in the supine position.

Differential Diagnosis

The differential diagnosis of chronic or recurrent lower abdominal pain is wide. Traditionally, the two main categories are various ‘organic’ disorders and various ‘functional’ bowel disorders (Table 7.1). In the case of organic disorders, the cause can be identified and, if improved or eliminated, symptoms improve. In the case of functional disorders, there is no structural or biochemical explanation for the symptoms, although in some there may be an identifiable pathophysiological dysfunction present. The distinction between ‘organic’ and ‘functional’ disorders has become increasingly blurred, however, because of the finding of low-grade intestinal inflammation in some cases of IBS.

Table 7.1 Differential diagnosis of chronic or recurrent lower abdominal pain

‘Organic’ disorders ‘Functional’ disorders
Common

• Diverticulitis, diverticular stricture
• Lactase deficiency
• Gynaecological disease
• Intestinal obstruction (partial, subacute)
• Crohn’s disease (especially small bowel)

Uncommon

• Chronic intestinal pseudo-obstruction
• Mesenteric ischaemia
• Malignancy (e.g. ovarian carcinoma)
• Abdominal wall pain
• Spinal disease
• Testicular disease
• Metabolic disease, e.g. diabetes mellitus, familial Mediterranean fever, C1 esterase deficiency (angioneurotic oedema), porphyria, lead poisoning, tabes dorsalis, renal failure

Common

• IBS
• Functional abdominal bloating

Uncommon
Functional abdominal pain syndrome

‘Organic’ disorders

Diverticular disease

Uncomplicated diverticular disease of the colon is very common, and is not normally associated with symptoms. A proportion of individuals with diverticulosis, however, experience recurrent lower abdominal pain, predominantly in the left iliac fossa, and occasionally a change in bowel habit. These symptoms are similar to, and indeed can be indistinguishable from, IBS, and it is probable that the symptoms in these instances are due to the presence of concomitant irritable bowel. In severe diverticular disease, in contrast, the colonic lumen can become distorted and narrowed in the sigmoid colon; symptoms of partial bowel obstruction may then develop and produce recurrent lower abdominal, often left iliac fossa, pain. Diverticulitis is discussed in Chapter 4.

Lactase deficiency

Lactose ingestion in lactase-deficient subjects can be associated with recurrent lower abdominal discomfort and diarrhoea. The prevalence of lactose intolerance varies widely according to race, for example 60% in Chinese people, 40% in eastern Mediterranean people and 10% in north-west Europeans. Affected individuals usually need to ingest a significant amount of lactose before noting symptoms. Even then, the symptoms may be more associated with concomitant IBS than lactose intolerance, as they do not necessarily improve with lactose restriction.

Gynaecological disorders

Endometriosis

Endometriosis may cause recurrent abdominal pain and bowel symptoms in women. Usually patients are under the age of 45 years and two-thirds are nulliparous. Symptoms may sometimes occur with the period (because the endometrial implants are influenced by hormonal changes; at termination of the menstrual cycle, endometrial engorgement and sloughing occurs). However, in many cases symptoms do not coincide with periods. Common symptoms include bloating, abdominal or pelvic pain, constipation or diarrhoea, proctalgia and lower back pain; indeed, irrespective of any bowel involvement, gastrointestinal symptoms have been shown to be nearly as frequent as gynaecological symptoms. Thus the gynaecological symptoms usually co-exist with the gastrointestinal symptoms (a clinical clue) and can include menstrual irregularity, dysmenorrhoea and dyspareunia. There may also be a history of infertility. Rectal examination may sometimes detect tender nodules or irregular induration. At sigmoidoscopy or colonoscopy, there may occasionally be findings of a submucosal mass, usually with overlying intact mucosa; biopsy may not be diagnostic because endometriosis is usually in the deeper layers. Barium studies may provide useful indirect evidence of the disease. Laparoscopy, the main diagnostic tool, allows direct visualisation and biopsy of serosal lesions, and also ablative therapy. Recurrence after surgical treatment is common. Hormonal therapy (usually oral contraceptives) may be useful in mild disease. Drugs such as danazol, a synthetic androgen, and antigonadotropins, such as gestrinone, are effective, but have a greater incidence of side effects than hormonal therapy. In cases with complicated bowel disease, surgical resection may be required. In incapacitating cases, a total abdominal hysterectomy and oophorectomy may be considered.

Pelvic inflammatory disease

Pelvic inflammatory disease, reflecting ascending infection of the endometrium or fallopian tubes, can be due to a number of pathogens including Neisseria gonorrhoeae and Chlamydia trachomatis; however, vaginal flora have also been implicated. With salpingitis, midline lower abdominal pain may be associated with a mucopurulent vaginal discharge and occasionally vaginal bleeding. Right iliac fossa pain and tenderness from periappendicitis can occur. Pelvic tenderness on bimanual pelvic examination is typical (uterine fundal tenderness may be due to endometritis whereas adnexal tenderness may be due to salpingitis, which is frequently bilateral). Gynaecological referral is indicated and laparoscopy is the most definitive method for diagnosis.

Adhesive enteropathy

Adhesive enteropathy is a controversial condition. The procedure of laparotomy is often followed by the development of some adhesions, and such adhesions are commonly encountered during a second laparotomy for some other reason. On most occasions these patients, when asked after that second operation, have had no symptoms referable to these adhesions. There are, however, a small group of patients who have chronic abdominal pain that may be due to the adhesions. The pain described by these patients is not colicky, as occurs in intestinal obstruction; it may be lateralised to one side or other. It tends not to be associated with other features of bowel obstruction, such as vomiting and constipation. Physical examination may reveal deep tenderness over the same area where the patient experiences the pain, and no signs of abdominal wall tenderness.

Investigation of these patients is usually not rewarding. Standard haematological and biochemical tests are negative. Intraabdominal imaging with ultrasound and computed tomography (CT) scans is also negative. Colonic imaging with barium enema is negative. A small bowel series or CT enterography is negative or equivocal; some minor irregularity, but short of a definite obstruction, may be found and the clinician can be left wondering whether the symptoms and the radiological abnormality are related. Many patients will have taken or be taking oral or even parenteral analgesics for relief. Most have seen several clinicians for their problems. Some patients will have been thought by their clinician to have a functional problem, not an organic disease. The clinical dilemma is: how much of the problem is organic and how much is functional? Unfortunately, there is no simple way of establishing the relative proportions. It is important that these patients be seen by a limited number of clinicians. It is also important that operation be left as the last resort because:

• dividing adhesions does not cure adhesions—they reform almost as soon as the abdomen is closed; and
• there is a risk of intraoperative perforation during adhesiolysis with possible progression to other infective complications in the postoperative period.
• the procedure is often time-consuming, because of the large number of adhesions that need to be divided.

Crohn’s disease

Crohn’s disease of the small intestine may produce recurrent mid to lower abdominal pain from inflammation, or symptoms of intermittent partial bowel obstruction from acute inflammation or stricturing disease (see Ch 15). Localised and minimal disease can be associated with delay before eventual diagnosis. Terminal ileal biopsy at colonoscopy enables confirmation of Crohn’s ileitis. Barium follow-through or CT or MRI enteroclysis can reveal evidence of likely small bowel Crohn’s disease. Capsule endoscopy of the small bowel avoids irradiation but is usually reserved for those where the clinical suspicion of Crohn’s disease remains despite negative other investigations.

Chronic intestinal pseudo-obstruction

This refers to a heterogeneous group of rare disorders affecting the neuromuscular apparatus of the bowel (Box 7.1). Recurrent symptoms of small or large bowel obstruction occur in the absence of luminal or extrinsic causes. Some cases can be associated with the ingestion of certain medications or secondary to rare metabolic or systemic disorders; others are idiopathic. Laparoscopic full-thickness jejunal biopsy is becoming increasingly utilised in order to obtain appropriate tissue for histological examination. Histology can provide clues as to the presence of myopathy, neuropathy or both, but in some cases no specific abnormalities can be demonstrated despite impressive clinical features. Therapies for the disorder are limited, and include symptomatic treatment, especially analgesia, nutritional support and treatment of complications. Drug therapy with prokinetic agents is not usually effective, especially in visceral myopathy. Antibiotics can be given for small bowel bacterial overgrowth. Surgical therapies include jejunostomy to facilitate enteral nutrition, venting gastrostomy or enterostomy to relieve abdominal distension, and resection of localised disease.

Box 7.1 Chronic intestinal pseudo-obstruction

Clinical features

• Abdominal pain—continuous or episodic
• Bloating and visible distension—continuous or episodic
• Vomiting—continuous or episodic
• Constipation (if predominant colonic involvement)
• Diarrhoea (if bacterial overgrowth from small bowel involvement)
• Dysphagia, chest pain (if oesophageal involvement)
• Weight loss (if reduced food intake or malabsorption)
• Palpable bladder (if megacystitis)
• Symptoms and signs of underlying cause (e.g. neurological, endocrine, connective tissue disease)

Diagnosis

• Imaging studies (plain films, barium contrast studies, CT scan, endoscopy), e.g. air/fluid levels, dilated gut segments
• Functional studies (gastric and small bowel transit, oesophageal manometry, gastroduodenal manometry, cystometrogram)
• Diagnostic laparotomy or laparoscopy (plus full-thickness biopsy of intestine)
• Specialised histochemical staining techniques of full-thickness biopsy (enteric nerves and ganglia, interstitial cells of Cajal, smooth muscle layers)
• Evaluate for underlying cause

Causes

Myenteric plexus disease

• Familial visceral neuropathies
• Sporadic visceral neuropathies, e.g. paraneoplastic (small-cell lung cancer)
• Hirschsprung’s disease

Smooth muscle disease

• Familial and sporadic visceral myopathies
• Scleroderma
• Polymyositis
• Amyloid

Endocrine disease

• Hypothyroidism
• Hypoparathyroidism
• Phaeochromocytoma

Drugs

E.g. phenothiazines, tricyclic antidepressants, clonidine, vinca alkaloids

Neurological disease

• Parkinson’s disease
• Progressive muscular dystrophy
• Myotonic dystrophy
• Familial autonomic dysfunction
• Mitochondrial myopathy

Abdominal angina (chronic mesenteric ischaemia)

This is an important condition to recognise. Usually this is due to atherosclerosis but the condition can also occur with vasculitis or other lesions of the splanchnic vessels. Abdominal pain occurs 10–30 minutes after eating, gradually increasing in severity and then slowly resolving over 1–3 hours. The pain can occur in the periumbilical region or in the epigastrium. The patient becomes afraid to eat and reduces the meal size to avoid pain, leading to substantial weight loss. The pain may be due to an increase in gastric blood flow after food enters the stomach, leading to ‘stealing’ of blood from the small intestine. On examination, there may be a systolic bruit in the abdomen, but this is non-diagnostic. Doppler flow studies of the celiac axis and superior mesenteric arteries are useful screening tests. Angiography is helpful to confirm the diagnosis if there is involvement of at least two of the three major arteries. However, as such abnormalities can occur in the absence of symptoms, this entity remains a largely clinical diagnosis.

Spinal disease

Referred abdominal pain from disorders affecting the spine can also occasionally lead to diagnostic difficulties. The abdominal pain is usually due to root irritation or compression associated with the spinal disease. Coughing, straining or sneezing typically increases the pain.

Diabetes mellitus

This disorder can cause abdominal pain due to diabetic radiculopathy or diabetic plexus neuropathy involving the thoracic nerve roots. Electromyographic studies of the anterior abdominal wall muscles can assist in making this diagnosis.

Familial Mediterranean fever

This autosomal-recessive disease is common in Europe and the Near East, and causes recurrent episodes of abdominal pain that may start in one quadrant and spread to involve the entire abdomen (due to peritonitis), associated with fever, There are often episodes of acute pleuritic pain with or without the abdominal pain; some patients have episodes of acute arthritis or painful erythematous areas of swelling, usually on the lower limbs. Leucocytosis and elevated C-reactive protein are characteristic features during attacks. The MEFV (for Mediterranean FeVer) gene responsible for the disease has been identified, and many mutations reported. Renal amyloidosis can complicate this disease. Prophylactic long-term use of colchicine reduces the number of acute attacks, and prevents renal amyloidosis.

Angioneurotic oedema

This is an autosomal-dominant disease associated with functional C1 esterase deficiency in which there are recurrent attacks of abdominal colic. There are no urticarial skin lesions but there may be episodes of laryngeal oedema. The diagnosis is suggested by a family history. In myeloproliferative disorders, an acquired form of C1 esterase deficiency has been reported.

Lead poisoning

In adults, abdominal pain associated with anaemia, renal disease, peripheral neuropathy, ataxia, memory loss and headache may occur in lead poisoning. Lead lines (a thin blue-black pigmented line along the gingival margin) may be evident. The pain of lead colic, as well as that of porphyria, can be difficult to distinguish from intestinal obstruction.

Acute intermittent porphyria

This is a rare autosomal-dominant condition. Abdominal pain is the most common symptom and is typically steady and poorly localised although it may be colicky in nature. Other symptoms include nausea and vomiting, constipation, tachycardia and hypertension, mental symptoms, pain in the limbs and elsewhere, sensory loss and muscle weakness, as well as urinary retention. Drugs, infections and surgery can precipitate attacks.

Tabes dorsalis

Acute attacks of pain may occur in the abdomen, although pain in the legs is more common. Loss of position sense leads to gait ataxia in 50% of patients. Neurological signs in the legs (e.g. loss of reflexes and impaired position and vibratory sense) are usually present.

‘Functional’ bowel disorders

These disorders are the most common causes of chronic or recurrent lower abdominal pain or discomfort.

Based on characteristic symptom clusters, a number of functional bowel disorders can be recognised.

Irritable bowel syndrome

This disorder is defined (Rome III diagnostic criteria) as at least 6 months of recurrent abdominal pain or discomfort (≥ 3 days per month), associated with two or more of the following:

• improvement with defecation; and/or
• onset associated with a change in frequency of stool; and/or
• onset associated with a change in form (appearance) of stool.

The presence of the following symptoms increases confidence in the diagnosis: abnormal stool frequency; abnormal stool form (lumpy/hard or loose/watery stool); abnormal stool passage (straining, urgency of feeling of incomplete evacuation); passage of mucus; and bloating or a feeling of abdominal distension. These symptoms often occur in discrete episodes, varying in frequency and severity, and are present without abnormalities on radiological, endoscopic and laboratory investigations. IBS accounts for 5% or more of attendances to general practitioners and 20–50% of referrals to gastroenterologists. It is twice as common in females as males, and half of the patients are younger than 35 years of age.

Functional bloating

This disorder is defined (Rome III diagnostic criteria) as at least 3 days per month of symptoms of (1) recurrent feeling of bloating or visible distension; and (2) insufficient criteria for diagnosis of functional dyspepsia, IBS or other functional gastrointestinal disorders. The term ‘bloating’ is used to indicate a sensory or perceptual phenomenon while ‘distension’ is used to denote an actual increase in abdominal girth. The symptoms in this condition are not usually constant or unremitting. Distension may require clothing to be loosened, tends to be minimal on waking and to increase as the day goes on. There may be accompanying increased passage of flatus and, less often, borborygmi. Bloating and/or distension are also common in IBS, but are accompanied by abdominal pain and bowel dysfunction.

Functional abdominal pain syndrome

This disorder (also known as chronic idiopathic abdominal pain) occurs far less frequently than either of the above disorders. It is defined (Rome III diagnostic criteria) as at least 6 months of (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) some loss of daily functioning; (4) the pain is not feigned; and (5) insufficient symptoms to meet criteria for another functional gastrointestinal disorder that would explain the pain.

The description of the pain does not fit a recognisable specific disorder, and the nature and site may change with repeated descriptions. During history taking, symptom-reporting behaviours should be noted. These include verbal and non-verbal expression of varying pain intensity, urgent reporting of intense symptoms, minimising or denying a role for psychosocial factors, requesting additional diagnostic studies, focusing attention on complete recovery, seeking health care frequently, taking limited personal responsibility for self-management, and making requests for narcotic analgesics.

Clinical Evaluation

The extent of the evaluation will depend on the age of the patient and the duration and severity of symptoms. Based on a detailed history and general abdominal examination, the organ and disease process most likely to be involved should be defined. In the history, ‘alarm features’ such as the presence of fever, weight loss, rectal bleeding or steatorrhoea are all strong pointers towards the presence of organic disease (Box 7.2). As well as the aspects of the pain discussed earlier, further questions are often required to elicit specific information, such as new exacerbating factors to the pain (e.g. dietary change or change in medication), worry about serious disease (especially cancer), new life stresses, the presence of psychological or psychiatric disorders, or impairment in the patient’s daily functioning. The family history can be very relevant. Because the functional bowel disorders cannot be established by any investigation, it is important to take a structured history, noting the features that support these diagnoses (see the definitions earlier), as well as those that suggest another cause for the symptoms. In some of these disorders (e.g. IBS), upper gastrointestinal symptoms, such as heartburn, dyspepsia, nausea and excessive belching, are frequently present, and non-gastrointestinal symptoms such as fatigue, dysmenorrhoea, migraine and symptoms of bladder irritability are also common. Moreover, in IBS for example, the history is often prolonged with symptoms dating from a relatively early age, and the course is characterised by exacerbations and remissions.

Box 7.2 Clinical features against the diagnosis of a functional bowel disorder

• First onset of symptoms in an elderly patient
• Symptoms waking the patient from sleep
• New symptoms after a prolonged period of stable symptoms
• Progressive, steady worsening of symptoms
• Weight loss
• Dysphagia
• Evidence of bleeding or dehydration
• Evidence of steatorrhoea
• Recurrent vomiting
• Fever
• Elevated C-reactive protein
• Anaemia or leucocytosis
• Blood, pus or excess fat in stool
• Hypokalaemia or persistent diarrhoea during fasting
• Stool weight greater than 350 g/day

Physical examination

Abnormal findings, apart from abdominal tenderness, are not common. Tenderness is often present over the colon in IBS, especially the sigmoid, although this region can be palpable and tender in healthy subjects. It is important to consider the abdominal wall as a possible origin of pain, and specifically test for tenderness confined to this region.

The presence of an abdominal mass raises the possibility of complicated diverticular disease or Crohn’s disease, while an abdominal aortic aneurysm should be palpable. Enlarged lymph nodes (e.g. supraclavicular) may indicate the presence of malignancy. Small bowel malignancies such as lymphoma, although rare, should be considered where appropriate. Rarely, coeliac disease may be associated with abdominal pain. External hernias should be excluded. The testes should be palpated for tenderness and masses. Pelvic masses or tenderness present on rectal examination may indicate a gynaecological cause.

Investigations

Investigations are dictated by the findings on history and physical examination, and the age of the patient. These may be performed to exclude or confirm the likely diagnosis and may include colonic investigation with sigmoidoscopy, colonoscopy or barium enema. Abdominal and/or pelvic ultrasonography, small bowel radiology, CT or MRI enteroclysis, or lactose tolerance testing may also be required. Screening blood tests are often performed, even if there are no specific causes discovered from the history and examination. Haematological tests include full blood count, blood film, C-reactive protein and, if indicated, iron studies, folate and vitamin B12 levels. Biochemical tests include liver function tests, serum albumin, electrolytes and urea—these are usually unhelpful. In cases of suspected IBS, however, coeliac serology, particularly tissue transglutaminase assay, is a recommended screening test. Stool testing for ova, cysts or parasites, and faecal antigens such as for Giardia spp. can be considered in some cases. There is increasing interest in the role of faecal calprotectin as a simple and non-invasive method to indicate the presence of colorectal inflammation, but further studies are required. Highly specialised investigations, such as ultrasound with Doppler flow studies and mesenteric angiography, or tests to diagnose the metabolic disorders above, may be warranted. Capsule endoscopy can be considered where a more definitive examination of the small intestine is warranted.

If organic colonic disease is suspected, full colonic investigation by colonoscopy or sigmoidoscopy and barium enema or CT colography is indicated. In patients 50 years of age or older, especially in those with a change in preexisting symptoms, or in patients with a family history of colorectal carcinoma or colonic polyps, colonoscopy is the preferred investigation to rule out colorectal neoplasia.

Where an abnormality is detected by laboratory or radiological studies, it is always important to consider whether this is likely to be the cause of the patient’s symptoms. When functional bowel disease is suspected, a protracted or piecemeal approach to investigation should be avoided, as it is likely to increase patient uncertainty and anxiety. If the diagnosis remains in doubt, it may be useful to see and investigate the patient during an acute exacerbation of pain. Rare causes should be considered and checked at this stage and appropriate other investigations, e.g. abdominal x-ray during an attack of pain, performed if indicated. ‘Diagnostic’ laparotomy is almost invariably non-contributory in cases of chronic abdominal pain already investigated as above. However, laparoscopy may enable the identification of recurrent intestinal obstruction from adhesions, which has escaped identification using other modalities.

Irritable Bowel Syndrome (IBS)

Pathophysiology

The pathogenesis of IBS is unknown. A number of physiological factors, however, appear to be associated with the disorder. Digestive tract dysmotility and hypersensitivity are likely to underlie the gut symptoms in these disorders. A variety of modulatory factors can affect the degree of digestive tract dysmotility and hypersensitivity. These factors are discussed below and include external factors such as psychosocial distress and local factors such as the intestinal microflora and specific nutrients.

Normal small bowel and colonic motility

In the small intestine, intermittent segmenting and propulsive contractions occur after ingestion of food, mixing it with digestive secretions and transporting the chyme aborally. Each propagated contraction is preceded by a propagated relaxation, a phenomenon termed the ‘peristaltic reflex’. The overall duration and intensity of postprandial motor activity depends upon the caloric content and the proportion of fat, carbohydrate and protein in the meal. The jejunum acts primarily as a mixing and conduit segment, while the ileum, which has specialised absorptive properties, retains chyme until digestion and absorption are largely complete. The terminal ileum and ileocolonic junction control the rate of emptying of ileal contents into the colon. In between meals, and particularly during sleep, motility in the stomach and small intestine undergoes regular cycles of activity every few hours, termed ‘migrating motor complexes’. These complexes migrate slowly along the small bowel, clearing away residual food and secretions.

In the colon, proximal colonic motor activity normally promotes the mixing of contents, absorption of water and electrolytes, and metabolism of colonic contents by bacteria. The rectosigmoid region stores faeces and generates specific motor programs enabling convenient elimination. Contractions in the colon occur at irregular intervals; there are two main types: individual phasic contractions and high-amplitude propagated contractions or giant migrating contractions. The latter are the main propulsive motor events in the colon, producing the so-called mass movements. After eating, colonic motor activity and tone increases (the gastrocolic reflex) in both the proximal and distal colon. Intestinal gas originates from three sources: the majority (about 70%) from swallowed air, a proportion from gases (carbon dioxide, hydrogen and methane) produced by bacterial fermentation of incomplete absorbed food and fibre in the colon, and a very small amount in the way of diffusion from the blood. On the average diet, material takes up to 3 days to pass through the colon, accounting for about 90% of whole gut transit time in healthy subjects.

Gastrointestinal sensorimotor dysfunction

Up-regulation of the sensory pathways travelling from the gut to the central nervous system appears to account for a heightened perception of normal gut sensations arising from intestinal distension and contraction (visceral hypersensitivity). This phenomenon of hypersensitivity may result in abdominal discomfort or pain; it may also trigger disordered gut motility and/or alterations in gut secretion or absorption, resulting in an erratic bowel habit. Exaggerated patterns of contraction, especially postprandially, have been observed in the small and large intestine; the gastrocolic reflex can be delayed and prolonged.

Altered motor activity affects gut transit. Thus, delayed transit through the small and large intestine, and increased absorption of water, can lead to symptoms of constipation, while accelerated transit may result in diarrhoea. Uncoordinated or abnormally high pressure contractions may lead to distension of the intestinal lumen, or trap pockets of intestinal gas that distend the bowel and produce abdominal pain. Stools of small or ‘normal’ volume that are passed more frequently may result from the combined effect of rapid small bowel transit, colonic dysmotility and rectal hypersensitivity to distension. In the majority of patients a trigger factor producing gut hypersensitivity is not found.

In some patients (up to 25%), IBS symptoms appear to be precipitated by an attack of infective diarrhoea or gastroenteritis, perhaps due to occult damage to the enteric nervous system. Increased numbers of lymphocytes, mast cells and enteroendocrine cells have also been demonstrated in biopsies from the colon in this ‘postinfective’ IBS. Altered permeability in the small intestine can occur. Symptoms in this disorder can persist for months, years or even a lifetime. There is no evidence that colonisation of the intestine with Candida albicans is a cause of IBS.

Behavioural factors

No specific personality type has been shown to be at special risk for development of IBS. Psychological stress, especially chronic stress, is associated with the onset and exacerbation of symptoms in some patients. It is unknown, however, whether the common associations of depression and anxiety are cause or effect. Psychological factors are also important because they influence the individual’s decision to seek medical attention as well as the ability to cope with the symptoms.

Dietary factors

Eating often provokes symptoms in patients with IBS. In general, meals high in fat move slowly through the gut, and in IBS this may exacerbate symptoms such as bloating and constipation. Foods such as baked beans, cabbage and brussels sprouts, and sugars such as fructose and sorbitol, may exacerbate symptoms in patients with complaints of excessive bloating and rectal flatus.

Patients frequently associate ingestion of specific food items with the development of symptoms. Although this may be a chance association, there is evidence that a non-immunological gut reaction may occur to a variety of foods such as dairy products, caffeine, onions, tomatoes and citrus fruits. Such food intolerance should be distinguished from the rare condition of true food allergy. Only a very small proportion of patients with IBS appear to have true allergic or immunological responses to specific foods.

Treatment

Management is outlined in Box 7.3. Therapy begins at the initial consultation, where it is essential to establish rapport with patients and secure their confidence. This is achieved by a process of reassurance regarding the genuine nature of the symptoms. Many patients have been told that they are not suffering from a significant illness; the patient should be reassured that IBS is a well recognised and common, though benign and chronic, clinical entity.

Box 7.3 Management of IBS

• Complete history and examination are essential. A positive diagnosis of IBS can be made by history.
• Avoid protracted investigation.
• Reassure the patient that:

– diagnosis is correct;
– symptoms are produced by gut sensorimotor dysfunction;
– there is no predisposition to other bowel disorders such as cancer.

• Use simple dietary modifications and non-drug therapy initially, according to predominant symptoms.
• Assure the patient that opportunity for review is available during difficult times, or if new symptoms develop.
• Inform the patient of the likelihood of residual symptoms persisting or recurring from time

The patient should be made aware at the outset that investigations will probably be negative, but that they serve to confirm the initial diagnosis of IBS. An explanation about the possible mechanism of symptoms should be given. This depends on an assessment of the patient’s level of sophistication, but always needs to be sympathetic and unhurried. Patient information leaflets and diagrams can be very helpful, but do not substitute for individual explanation and discussion. At the follow-up visit the physician should check how much the patient has really understood.

A concise dietary history should focus on fibre intake, fat and specific carbohydrate ingestion, and any possible food intolerances (e.g. dairy products, soft drinks, some ‘diet’ confectionery, gas-producing foods, or other specific foods). The pattern of symptoms in relation to the patient’s day, including work, eating, exercise and sleeping habits can then be broadened into a discussion about stresses at work and at home.

The presence of psychological disorders and, if possible, their onset in relation to the onset of gastrointestinal symptoms should be ascertained. It is important to consider why the patient is seeking help now. A careful history to identify possible precipitating or contributing factors should lead to advice about simple lifestyle modifications. It is essential for the patient to understand that IBS is generally a chronic condition, in which exacerbations and remissions are often a feature. Notwithstanding this pattern of the disorder, the patient should be advised to report any changes in symptoms that develop over the years. A discussion of prognosis is important and is often overlooked; it is important to reassure patients that the condition does not predispose to other gut disorder, particularly malignancy, and to inform them that residual symptoms may persist despite therapy.

Diet and the role of fibre

Foods and beverages that clearly and consistently provoke symptoms should be avoided. If bloating and flatulence are prominent symptoms, the patient should be advised to eat slowly, to avoid smoking and chewing gum, and to try to avoid excessive air swallowing associated with belching.

Although it is controversial whether dietary fibre supplementation is of any greater overall benefit, a stool bulking by a regular increased intake of fibre-rich foods (e.g. cereals, wholemeal bread and unprocessed wheat bran) and/or proprietary bulking agents should be trialled in most patients. Fibre supplementation should be introduced gradually and continued for at least 1 month before its effect is judged. Patients should be made aware that too much fibre can produce excessive intestinal gas and cause bloating and flatus. Proprietary bulking agents (e.g. those containing psyllium or ispaghula) may be less likely to cause this problem than bran. A trial of stool bulking is less likely to be effective in patients with diarrhoea-predominant IBS. In selected cases, where there is a high suspicion of food intolerance, a symptom and food diary may enable the patient to recognise specific items more readily.

Medications

The decision to use a medication in IBS depends on the severity of symptoms and their influence on the quality of life of the patient. The choice of medication depends on the pattern of symptoms. Randomised, placebo-controlled trials of traditional pharmacotherapeutic agents in IBS have generally been disappointing. However, for predominant diarrhoea, antidiarrhoeal drugs such as loperamide have been shown to be effective. For predominant constipation, in addition to a trial of stool bulking, an increase in fluid intake, and regular exercise, osmotic laxatives such as magnesium-containing salts (e.g. Epsom salts), polyethylene glycol compounds or lactulose are safe and can be effective. Anticholinergic agents (such as hyoscine butylbromide or hydrobromide, hyoscyamine sulfate or dicyclomine) or antispasmodic agents (such as mebeverine) may be helpful in some individuals with prominent abdominal pain, especially if it is meal-related. However, differentiation from the placebo response is difficult. Ideally, drugs such as those above should be used in the short term only, and the dose adjusted depending on the timing and severity of symptoms. Moreover, it should be appreciated that such medications target only one symptom—abdominal pain, diarrhoea or constipation—and may not improve (indeed in some cases can worsen) other aspects of the symptom complex.

A number of complementary medicine compounds have shown promise in the treatment of IBS. These include several types of probiotic agents and herbal preparations. There is evidence that Bifidobacterium infantis 35624 has greater efficacy in reducing abdominal pain, bloating, straining and overall IBS symptoms than other strains. Further studies are required to investigate other such compounds, and to determine the mechanisms of action of those agents exhibiting efficacy.

If there is no improvement

It is important to assess whether the patient can cope with ongoing symptoms, or still fears that some other underlying diagnosis is being overlooked. In this latter group, continued reassurance may be necessary. It is also important to re-emphasise to the patient the limitations of current therapies and that treatment strategies are not aimed at a cure, which in most is not achievable.

A small (non-antidepressant) dose of tricyclic antidepressant (e.g. amitriptyline 10–25 mg in the evening) has been shown to be useful in some patients with resistant symptoms, probably by influencing central pain perception. When significant symptoms of depression are present, however, adequate therapy with full antidepressant doses should be employed. The selective serotonin reuptake inhibitors are also efficacious in some patients. Minor tranquillisers (e.g. benzodiazepines) are not recommended for use in this chronic condition.

There is increasing evidence that non-absorbable antibiotics improve diarrhoea-predominant IBS.

If food intolerance is strongly suspected, trials of exclusion diets and blind challenges to identify offending foods and additives have been reported to decrease symptoms in some patients, especially those with predominant diarrhoea. This is rarely necessary, and may be most appropriately carried out in an allergy clinic with a research interest in this field. There is no role for a gluten-free diet in IBS. If coeliac disease is suspected, serological testing and, if positive, small bowel biopsy are indicated.

Relaxation therapy may be appropriate for some patients, and individual psychotherapy or hypnotherapy, which have been reported to improve symptoms if other measures have not been helpful, can also be arranged by a psychologist, psychiatrist or interested general practitioner.

When to review the diagnosis

If new symptoms develop or there is a change in the pattern of existing symptoms, it is important to review the diagnosis carefully or to consider the possibility that an additional problem has arisen. Other disorders that may need to be considered, depending on the individual case, include:

• the development of colon cancer;
• an episode of diverticulitis or an intercurrent gastrointestinal infection;
• symptoms due to gallstones;
• peptic ulceration;
• the development of pancreatic carcinoma;
• the development or exacerbation of a psychological problem, such as depression.

Key Points

• Chronic or recurrent abdominal pain is a common symptom and is often a source of diagnostic difficulty.
• Organic gastrointestinal disorders (e.g. complicated diverticular disease, gynaecological disorders and Crohn’s disease) and functional bowel disorders (e.g. irritable bowel syndrome and functional abdominal pain syndrome) are the two main categories of disorders causing chronic lower abdominal pain.
• Irritable bowel syndrome is the most common functional bowel disorder.
• Important features of the history include the site, radiation and referral of the abdominal pain, and also the character, intensity and duration of the pain and any modifying factors.
• Alarm symptoms such as fever, weight loss, rectal bleeding, steatorrhoea or family history of gastrointestinal carcinoma increase the likelihood of organic disease.
• The extent of the clinical evaluation depends on the age of the patient and the duration and severity of symptoms.
• Investigations required may include colonic investigation, abdominal radiology and a range of blood and stool tests. Other specialised tests (e.g. ultrasound of mesenteric vessels) may be indicated.
• Management of the relevant organic gastrointestinal disorders depends on a precise diagnosis.
• Management principles of irritable bowel syndrome include education about the mechanisms of symptoms, reassurance regarding the longer term safety of the diagnosis, and use of simple dietary modifications and non-drug therapy.

Further reading

Brandt L.J., Chey W.D., Foxx-Orenstein A.E., et al. An evidence-based systematic review on the management of irritable bowel syndrome. Am J Gastroenterol. 2009;104(suppl 1):S1-S35.

Brenner D.M., Moeller M.J., Chey W.D., et al. The utility of probiotics in the treatment of irritable bowel syndrome: a systematic review. Am J Gastroenterol. 2009;104:1033-1049.

Clouse R.E., Mayer E.A., Aziz Q., et al. Functional abdominal pain syndrome. In Drossman D.A., editor: Rome III: The Functional Gastrointestinal Disorders, 3rd edn, McLean: Degnon Associates, 2006.

Ford A.C., Chey W.D., Talley N.J., et al. Yield of diagnostic tests for celiac disease in individuals with symptoms suggestive of irritable bowel syndrome: systematic review and meta-analysis. Arch Intern Med. 2009;169:651-658.

Kellow J.E., Azpiroz F., Delvaux M., et al. Principles of applied neurogastroenterology: physiology/motility sensation. In: Drossman D.A., editor. Rome III: The Functional Gastrointestinal Disorders. 3rd edn. McLean: Degnon Associates; 2006:40-63.

Longstreth G.F., Thompson W.G., Chey W.D., et al. Functional bowel disorders. Gastroenterology. 2006;130:1480-1491.

Shepherd S.J., Parker F.C., Muir J.G., et al. Dietary triggers of abdominal symptoms in patients with irritable bowel syndrome: randomized placebo-controlled evidence. Clin Gastroenterol Hepatol. 2008;6:765-771.

Spiegel B.M., Chey W.D., Chang L. Bacterial overgrowth and irritable bowel syndrome: unifying hypothesis or a spurious consequence of proton pump inhibitors? Am J Gastroenterol. 2008;103:2972-2976.

Spiller R.C. Postinfectious irritable bowel syndrome. Gastroenterology. 2003;124:1662-1671.

Talley N.J., Spiller R. Irritable bowel syndrome: a little understood organic bowel disease? Lancet. 2002;360:555-564.

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