Case

A 48-year-old man presents with a history of frequent watery diarrhoea for the last 3 months, up to six times daily. He travelled to Southeast Asia, including Thailand, 3 months ago. There has been no blood in the stools and they have not been excessively pale or difficult to flush away. After he drinks milk or eats gluten-containing foods, his symptoms are worse.

Physical examination reveals a well-looking, afebrile man. There is no obvious lymphadenopathy, his abdominal examination is normal and the remainder of the examination is non-contributory.

The patient is noted to be anaemic with a haemoglobin of 90 (normal is 120-140); the anaemia is hypochromic and microcytic. On checking his iron stores are low but his B₁₂ and folate levels are normal. He has a low calcium and phosphate as well as a low vitamin D. Stool examination microscopy is normal, but Giardia antigen is positive.

He is given a course of tinidazole, but symptoms continued on follow-up 1 month later. In view of this, he is tested for coeliac disease, and tissue transglutaminase antibodies are positive. Upper endoscopy is performed and small bowel biopsies obtained; these show partial villous atrophy consistent with coeliac disease, but no giardia. A bone mineral density scan is performed and he has evidence of osteopenia. He is treated with a gluten-free diet as well as iron, calcium and vitamin D supplements plus folic acid, and has an excellent response with resolution of his diarrhoea. He is advised to maintain a gluten-free diet for life for treatment of coeliac disease.

Villous atrophy can be seen both in giardia and coeliac disease so these conditions can be confused. Testing bone mineral density is important in coeliac disease where a lifelong gluten-free diet is recommended to reduce complications. Patients may develop secondary lactose intolerance (and milk intolerance) with coeliac disease, but this usually recovers after a gluten-free diet is adopted.

Introduction

Chronic diarrhoea can be simply defined as the frequent or urgent passage of unformed stool for at least one month. As with acute diarrhoea (Ch 13), a careful history and physical examination will often help suggest the diagnosis and direct investigations.

History

The clinician needs to determine what the patient means by diarrhoea. The patient should be asked about the frequency and consistency of the stools. Diarrhoea needs to be distinguished from rectal urgency alone or faecal incontinence (Ch 16).

Clues to the cause of the diarrhoea can be obtained from the history and examination (Table 14.1). Small-volume, frequent stools suggest large bowel disease and tenesmus (a constant sense of the need to defecate) suggests rectal involvement. Large-volume, watery stools are consistent with small bowel disease, whereas obvious clinical steatorrhoea with pale, bulky, oily stools that float suggests the presence of small bowel or pancreatic disease.

Table 14.1 Clinical features in chronic diarrhoea

The presence of blood may indicate local anal bleeding or other colonic disease. Bright red blood that is separate from the stool is consistent with an anal or rectal cause, but may occur with more proximal colonic disease. Altered blood, or blood with the stool is in keeping with higher colonic bleeding, such as from inflammatory bowel disease or colon cancer (Ch 10).

Symptoms associated with the diarrhoea may also provide valuable information about the nature of the underlying disease process. Weight loss suggests an organic disorder and may be marked with malabsorption, carcinoma or inflammatory bowel disease. Large joint arthritis or sacroileitis suggests inflammatory bowel disease. Yersinia infection and Whipple’s disease can also present with arthritis.

Symptoms of individual nutrient deficiencies (like easy bruisability with vitamin K deficiency, night blindness with vitamin A deficiency, tetany and osteomalacia with vitamin D deficiency and stomatitis, angular cheliosis, glossitis and anaemia with iron and B group vitamin deficiency) not only help separate functional from organic diarrhoea but also may provide aetiological clues.

The presence of a skin rash may suggest coeliac disease (e.g. dermatitis herpetiformis) or inflammatory bowel disease (e.g. erythema nodosum or erythema multiforme). Crampy abdominal pain occurs with diarrhoea of any cause, but pain shortly after eating raises the possibility of partial bowel obstruction (e.g. Crohn’s disease or bowel cancer). Abdominal pain is also a feature of chronic pancreatitis, associated with malabsorption. Abdominal bloating may occur with most forms of diarrhoea but, in association with alternating diarrhoea and constipation, suggests the presence of the irritable bowel syndrome. The duration of symptoms may also be helpful, as diarrhoea occurring over many years is more in keeping with a benign process.

There may be a correlation between diarrhoea and diet. Milk consumption in lactose-intolerant individuals or sorbitol intake (in chewing gum and fruit juices) can cause diarrhoea. Changing to a high-fibre diet may also cause a change in bowel habit with loose stools.

A history of systemic disease may be relevant. Disorders such as diabetes mellitus and hyperthyroidism may present with diarrhoea.

Previous surgical history including gastrectomy (postvagotomy diarrhoea and dumping syndrome), small bowel resection, bariatric surgeries and cholecystectomy must be obtained.

A drug history may identify the cause of diarrhoea; a wide variety of medications have been implicated. Antibiotics and antacids are frequent offenders in this category. Non-steroidal anti-inflammatory drugs (by causing ileal damage and bile salt malabsorption), metformin and several cardiac drugs (antiarrthymics, antihypertensives and diuretics) are other commonly used offenders and should be sought in the history. Alcohol is also a cause of chronic diarrhoea and surreptitious laxative abuse needs to be considered in difficult cases.

A sexual history is important in the evaluation of a chronic diarrhoeal illness, as diarrhoea is a very common symptom in patients with HIV/AIDS. Overseas travel before the onset of diarrhoea may implicate a gastrointestinal infection or, more frequently, a postinfectious irritable bowel syndrome.

The family history should be obtained as inflammatory bowel disease, bowel cancer and coeliac disease have an increased incidence in families.

Physical Examination

Evidence of malnutrition and wasting should be sought and the skin examined for rashes, pigmentation and evidence of nutritional deficiency. There may be evidence of iron deficiency (pallor, cheilosis, glossitis and koilonychias) or vitamin B₁₂ deficiency (peripheral neuropathy, glossitis and knuckle pigmentation). Protein deficiency may result in peripheral oedema and white nails.

Signs of thyrotoxicosis including tachycardia, systolic hypertension, sweating and tender thyroid nodule should be checked as well as all lymph node groups examined as a clue to lymphoma, malignancy and other chronic infections.

Further clues to the cause of diarrhoea may be obtained from abdominal examination. An abdominal mass or liver secondaries may be identified. A rectal mass may be present on rectal examination, or faecal impaction, particularly in elderly patients, may be noted and sphincteric tone should be tested to rule out faecal incontinence. Perianal disease with fissures, fistulae and abscesses is common in Crohn’s disease (Ch 12).

Assessment

The history and physical examination will often direct the order and nature of investigations.

Categorising the pattern of diarrhoea into osmotic (ceases on fasting), secretory (persists in fasted state), inflammatory (passage of blood) and classical steatorrhoea helps in directing investigations though overlap can occur. (See Figs 14.1 and 14.2.)

Figure 14.1 Flow chart 1.

Adapted from Fine, KD, Schiller, LR. AGA technical review on the evaluation and management of chronic diarrhea. Gastroenterology 1999; 116:1464.

Figure 14.2 Flow chart 2

From Fine, KD, Schiller, LR. AGA technical review on the evaluation and management of chronic diarrhea. Gastroenterology 1999; 116:1464.

Approach to Chronic Diarrhoea

In those in whom the diagnosis is not obvious, a variety of factors will influence the order and extent of investigations, especially the age of the patient and the length of the history. A long history suggests a benign illness, although disorders, such as coeliac disease and Crohn’s disease, may not be diagnosed for many years because of subtle symptoms. Conversely, the development of new symptoms in a patient over the age of 40 years would raise concern about the possibility of bowel cancer.

A full blood count and erythrocyte sedimentation rate (ESR) is a simple initial blood investigation and may provide information about anaemia due to iron, folate or vitamin B₁₂ deficiency. It may also show an elevated white cell count or ESR, suggesting the presence of inflammation. The serum albumin will often be low with chronic inflammatory process or with malnutrition.

The stool examination may provide information about parasites, such as Giardia lamblia, and may also document white blood cells implicating inflammation or infection, or red blood cells in bleeding (e.g. carcinoma). The stool weight provides some evidence of the severity of diarrhoea.

Sigmoidoscopy may establish the presence of inflammation or tumours. A biopsy should always be performed in patients with diarrhoea to exclude microscopic or collagenous colitis. Melanosis coli may be obvious macroscopically and will also be demonstrated on biopsy. A colonoscopy requires a full bowel preparation with sedation, but has the advantage of examining the entire bowel length and often the terminal ileum can be intubated as well. Disorders that may require colonoscopy for diagnosis include bowel cancer, polyps, segmental colitis and terminal ileitis.

Radiological investigations that may aid in the investigation of diarrhoea include a plain abdominal x-ray, small bowel series, barium enema, virtual computed tomography (CT) colonography and abdominal CT scan.

If small bowel disease is suspected, a small bowel biopsy (usually performed endoscopically) may provide further information. A disaccharidase assay can be carried out at the same time as a small bowel biopsy and bacterial culture.

Further investigations that may be needed if no diagnosis is reached include stool examination for laxatives and blood tests for thyroid function (thyroid-stimulating hormone) and hormone-secreting tumours (e.g. gastrin and vasoactive intestinal polypeptide).

Malabsorption

The basic physiological problem the body faces in assimilation of food is the passage of nutrients across the limiting cell membrane of the enterocyte. The problem is solved by breaking food particles down to basic components (digestion) and the insertion of special carrier proteins into the absorptive cells to facilitate absorption. The term ‘malabsorption’ is generally used to encompass both impaired digestion and defective absorption. A classification of malabsorption is shown in Box 14.1.

Clinical Approach to the Patient with Malabsorption

Diagnosis in malabsorption requires firstly suspecting its presence, secondly confirming its existence and thirdly demonstrating the cause (Table 14.2).