Chronic lower abdominal pain or discomfort

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7 Chronic lower abdominal pain or discomfort

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

• Diverticulitis, diverticular stricture

• Lactase deficiency

• Gynaecological disease

• Intestinal obstruction (partial, subacute)

• Crohn’s disease (especially small bowel)

• 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

• Functional abdominal bloating

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

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