**5. Diagnosis**

#### **5.1. History**

To diagnose giardiasis, an expert microbiologist is required to identify giardia trophozoite in stool samples. Initial steps to diagnose malabsorption require extensive history and physical examinations. Duration of diarrhoea, stool characteristic and presentation of other symptoms such as poor night vision (vitamin A deficiency), pin and needles in both arms and legs (vitamin B6, B12 deficiency), poor cognitive functions, muscle wasting and significant weight lost suggest present of malabsorption. However, extensive history is still needed to exclude other differential diagnosis of chronic diarrhoea [45] (**Table 3**). History of travel especially to the endemic area of *giardia* helps increase suspicion for this infection.

Effective ways in history taking is to know the differential diagnosis of diarrhoea.

Other information that should be obtained is



**Table 3.** Differential diagnosis of chronic diarrhoea [45].

**Figure 2.** Diagnosis algorithm for chronic diarrhoea.

In fact, after the resolve of diarrhoea, myopathy also improves. Main symptoms of these patients are proximal myopathy which is transient, but patients may have other co-morbid

To diagnose giardiasis, an expert microbiologist is required to identify giardia trophozoite in stool samples. Initial steps to diagnose malabsorption require extensive history and physical examinations. Duration of diarrhoea, stool characteristic and presentation of other symptoms such as poor night vision (vitamin A deficiency), pin and needles in both arms and legs (vitamin B6, B12 deficiency), poor cognitive functions, muscle wasting and significant weight lost suggest present of malabsorption. However, extensive history is still needed to exclude other differential diagnosis of chronic diarrhoea [45] (**Table 3**). History of travel especially to the

**1.** Onset: gradual, sudden, congenital. Diarrhoea caused from malabsorption usually pro-

**4.** Systematic diseases such as endocrine (hypothyroidism, hypothyroidism), immunological

**5.** Other associated symptoms such as abdominal pain (location, precipitating, aggravating,

Enterotoxins (e.g., cholera)

Congenital chloridorrhea

Magnesium ingestion Lactase deficiency

Diffuse mesenteric atherosclerosis Intestinal hurry following vagotomy

Neuroendocrine tumours (e.g, carcinoid syndrome)

Intestinal resection, diffuse intestinal mucosal disease

endemic area of *giardia* helps increase suspicion for this infection.

Effective ways in history taking is to know the differential diagnosis of diarrhoea.

symptoms associated with hypokalaemia.

Other information that should be obtained is

**2.** Pattern: continuous or intermittent.

Secretory Exogenous secretagogues

diseases, and neoplasm.

relieving factors).

gressive in term of frequency and consistency.

**3.** Iatrogenic factors such as drugs, radiation, tube feeding.

**Type of diarrhoea Causes Example**

Intestinal ischemia Rapid intestinal transit

Osmotic Ingestion of poorly absorbed agent

**Table 3.** Differential diagnosis of chronic diarrhoea [45].

Endogenous secretagogues Absence of ion transporter Loss of intestinal surface area

Reduced nutrient transport

**5. Diagnosis**

32 Current Topics in Giardiasis

**5.1. History**

As **Table 3**, the initial step in the evaluation of chronic diarrhoea is to send stool off for assessment of stool osmotic gap. This allows the differentiation of chronic watery diarrhoea into secretory (faecal osmotic gap <50 mOsm per kg) and osmotic (faecal osmotic gap >125 mOsm per kg). Watery diarrhoea is likely osmotic because the symptoms caused by malabsorption and maldigestion.

#### **5.2. Physical examinations**

Physical examination is important and provide important clue into the diagnosis of chronic diarrhoea [45]. Recent weight loss and lymphadenopathy could result from chronic infection or malignancy. Eye finding such as episcleritis or exophthalmia suggests that the diarrhoea is caused by inflammatory bowel disease (IBD) and hyperthyroidism, respectively. The signs that are directly attributed to giardiasis are limited; in fact, there are no specific signs that direct the clinician to suspect giardiasis. However, signs such as anaemia (iron deficiency anaemia), nail pallor, glossitis and koilonychias suggest that there is malabsorption of iron, and cause such as *giardia*, especially in region such as Thailand, should be identified.

#### **5.3. Laboratory diagnosis**

Stool microscopy is an important initial test to identify *giardia* trophozoite, blood and faecal leukocyte. Faecal pH test can be done quickly in most centre along with faecal electrolyse to help distinguish secretory diarrhoea from osmotic diarrhoea. A complete blood count, albumin level, erythrocyte sedimentation rate, liver function testing, thyroid-stimulating hormone level and electrolyte levels are important and help exclude other diagnosis such as hyperthyroidism, inflammatory bowel disease, chronic pancreatitis as well as chronic hepatitis [45]. **Figure 2** shows the diagnosis algorithm in managing patients with chronic diarrhoea [45].

## **6. Conclusion**

*Giardia* is one of the most common water-borne diseases in Thailand and in the world. The finding is particularly more in the area with poor sanitation and unsafe water. In Thailand, the parasites are found in lake and canal but also in water supplies, swimming pool and well. *Giardia* can be transmitted through food and person-person contact. *Giardia* infection usually will be cleared within a few weeks; however, patients might still have intestinal symptoms even after the infection is cleared.

The mechanisms of malabsorption in giardiasis are still obscured. The mechanism such as epithelial dysfunction, villi malformation and immunological disordered has been postulated to be an important cause of malabsorption and maldigestion in giardiasis. It is important to recognise symptoms of chronic giardiasis because this may lead to long-term disability.

Infection with *Giardia* duodenalis may remain asymptomatic or cause acute or chronic diarrhoea. In addition to the intestinal presentation, patient may also develop extra-intestinal complication such as impairment of cognitive function, muscular complications and nutritional deficiencies. Moreover, giardiasis is now recognised as important cause of failure to thrive, stunting and growth retardation in children of the developing countries. In Thailand, giardiasis is considered as public health importance. Although, the long-term consequences of giardiasis is variable, school health program and health education are available for parents and children aimed at reducing the prevalence of parasitic infection and, as a consequence, have a beneficial effect on child growth and development [39].

The diagnosis of giardiasis can be very difficult in asymptomatic individuals. However, the initial steps should include history taking and physical examinations. There are many differential diagnosis of chronic diarrhoea in both adult and children; therefore, good approach in to diagnosis of giardiasis can help reduce hospital health care cost for the patients. Stools sample should be obtained as are sent for microscopy to identify giardia's trophozoite. Serum iron, ferritin, B12 and sign of complications of giardiasis should be investigated.

Treatment aimed directly at clearing the parasite. The antibiotic that is most frequently used is metronidazole. Nutrition supplements, improved health hygiene and sanitation are important aspect into management of giardiasis. Symptoms such as diarrhoea may persist long after the parasites have been cleared.
