Giardiasis differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.; Serge Korjian M.D.

Overview

Giardiasis must be differentiated from other causes of abdominal pain, bloating, acute or chronic diarrhea, and weight loss, such as other infectious causes of gastroenteritis, including bacterial, viral, fungal, and parasitic pathogens, in addition to non-infectious causes, including acute pancreatitis, appendicitis, bowel obstruction, diverticulitis, drug reaction, hyperthyroidism, inflammatory bowel disease, celiac disease, lactose intolerance, Whipple disease, tropical sprue, and lymphoma.

Differentiating Giardiasis from other Diseases

• Giardiasis must be differentiated from other causes of acute or chronic diarrhea, bloating, abdominal pain, and fever (less common).
• Differential diagnosis of giardiasis includes the following:

Infectious Differential Diagnoses

• Bacterial infections (e.g. E. coli infection, shigellosis, salmonellosis, C. jejuni infection)
• Viral infections (e.g. norovirus, rotavirus, astrovirus, HIV)
• Fungal infections (e.g. Candida spp.)
• Parasites (E. histolytica, Cryptosporidium spp., Cyclospora)

Non-infectious Differential Diagnoses

The following are the non-infectious differential diagnoses of E. coli enteritis:

• Acute pancreatitis
• Adrenal insufficiency and Waterhouse-Friedrichsen syndrome
• Allergy (e.g. insect bite allergy or anaphylaxis)
• Appendicitis
• Bowel obstruction
• Celiac disease
• Diverticulitis
• Drug reaction (e.g. antimicrobial agents, antihypertensive therapy, chemotherapy, anticonvulsants)
• Endometriosis
• Familial Mediterranean fever
• Gastrointestinal perforation
• Hyperthyroidism
• Ileus
• Inflammatory bowel disease (Crohn's disease or ulcerative colitis)
• Intussusception
• Ischemic colitis
• Ketoacidosis
• Lactose intolerance
• Lymphoma
• Mesenteric ischemia
• Necrotizing enterocolitis
• Ogilvie syndrome
• Peritonitis
• Pneumonia
• Poisoning and toxicity (e.g. carbon monoxide poisoning, organophosphate poisoning, digitoxin toxicity)
• Ruptured abdominal aortic aneurysm
• Spider bite
• Tropical sprue
• Volvulus
• Urinary tract infection
• Whipple disease

To view a comprehensive list of abdominal pain differential diagnoses, click here.
To view a comprehensive list of diarrhea differential diagnoses, click here.

Giardiasis must be differentiated from other diseases that may cause chronic diarrhea, weight loss, and abdominal pain especially in immunocompromised patients.

Disease	Prominent clinical findings	Laboratory or radiological findings
Chronic giardiasis	Chronic giardiasis may develop after acute episode of giardiasis or without any acute events. Loose foul smelling stools Flatulence Fatigue Weight loss Steatorrhea Some patients develop acquired lactose intolerance (manifested by exacerbation of symptoms following ingestion of dairy products)	Microscopic identification of the organism in the stool Hypoalbuminaemia Vitamin B12 and folate deficiencies (as the organism inhabits the duodenum)
Cryptosporidiosis	Incubation period is 7-10 days. In immunocompetent patients: Disease might be asymptomatic or cause gastroenteritis (but without any biliary involvement) Gastroenteritis usually resolves spontaneously within 14 days. In immunocompromised patients: Disease is usually more severe and prolonged (especially in severly immunocomprmised patients with CD4 count < 100 cells/microL). Cryptosporidiosis may involve the biliary tract and the liver. Weight loss Abdominal RUQ tenderness might be present if biliary or hepatic involvement is present.	Microscopic identification of the organism in the stool: The oocysts appear red on staining with modified acid fast staining PCR: Most specific and sensitive diagnostic tool. PCR is expensive and used in limited cases.
Cystoisosporiasis (isosporiasis)	Cystoisosporiasis is usually seen in immunocompromised patients. Incubation period can last up to 2 weeks Watery diarrhea that is profuse and foul smelling Constitutional symptoms (headache, low grade fever, myalgia and malaise)	Isospora ova or parasites can be visualized on stool microscopic examination. Upper GI endoscopy may used for excluding other esophageal or gastric disease and obtaining specimens for histopathology.
Tropical sprue	History of travel to a tropical region (for a period more than a month) Chronic diarrhea Steatorrhea Examination may show signs of vitamin deficiencies (eg glossitis)	Megaloblastic anemia that might progress into pancytopenia Hypoalbuminaemia Vitamin D defeciency and hypocalcemia