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
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

‘Functional’ disorders

Common

• Diverticulitis, diverticular stricture

• Lactase deficiency

• Gynaecological disease

• Intestinal obstruction (partial, subacute)

• Crohn’s disease (especially small bowel)