Intestinal Parasites and Infestation

Published on 13/07/2015 by admin

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Last modified 22/04/2025

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 Giardia lamblia (giardiasis)

image Cryptosporidium (cryptosporidiosis)
image Entamoeba histolytica (amebiasis)

IMAGING

• Best diagnostic clue

image Ascariasis: Linear filling defect on small bowel follow-through (SBFT)
image Giardiasis and cryptosporidiosis

– Thickened duodenal and jejunal folds on SBFT
image Amebiasis: Diffuse ulcerating colitis, right lobe liver abscess on CECT
• Location

image Small bowel (SB), colon, CBD, or pancreatic duct (ascariasis)
image Duodenum, jejunum (giardiasis)
image Colon, liver (amebiasis)
• Best imaging tool

image SBFT (ascariasis, giardiasis, and cryptosporidiosis)
image Barium enema, CECT (amebiasis)

TOP DIFFERENTIAL DIAGNOSES

• Crohn disease
• Ulcerative colitis

CLINICAL ISSUES

• Ascariasis infests 25% of world population
• Giardiasis and cryptosporidiosis: Most common protozoal diseases in USA
• Amebiasis infests 10% of world population

DIAGNOSTIC CHECKLIST

• Consider Crohn disease, ulcerative colitis
image
(Left) Axial CECT with intravenous and oral contrast in a 19-year-old woman from Mexico status post motor vehicle crash reveals linear filling defects image in the proximal small bowel. These defects represent the roundworm Ascaris lumbricoides.

image
(Right) Anteroposterior view of a small bowel follow-through (SBFT) demonstrates thickened folds in the proximal jejunum image from giardiasis.
image
(Left) SBFT in a 40-year-old man who recently immigrated from India, now presenting with abdominal pain and diarrhea, demonstrates long curvilinear filling defects image within the small bowel, essentially diagnostic of Ascaris infestation.

image
(Right) Small bowel barium study reveals Ascaris as a longitudinal filling defect in the distal small bowel image.

TERMINOLOGY

Definitions

• Enteric infection with roundworm Ascaris lumbricoides
• Enteric protozoal infection with Giardia lamblia, Cryptosporidium, or Entamoeba histolytica

IMAGING

General Features

• Best diagnostic clue

image Ascariasis: Linear filling defect on SBFT
image Giardiasis and cryptosporidiosis: Thickened duodenal/jejunal folds on SBFT
image Amebiasis: Diffuse ulcerating colitis, right lobe liver abscess on CECT
• Location

image Small bowel (SB), colon, common bile duct (CBD), or pancreatic duct (ascariasis)
image Duodenum and jejunum (giardiasis)
image Colon or liver (amebiasis)

Radiographic Findings

• Radiography

image Ascariasis: Soft tissue mass from coiled worms at ileocecal valve
image May progress to SB obstruction (SBO)

Fluoroscopic Findings

• Barium studies

image Linear filling defects up to 35 cm long in SB (ascariasis)
image Thickened duodenal and jejunal folds (giardiasis and cryptosporidiosis); colon ulcerations (amebiasis)
image  

CT Findings

• CECT

image Ascariasis: Linear or mass-like filling defects in SB, biliary obstruction, pancreatitis
image Amebic colitis: Mucosal hyperenhancement, submucosal edema ± solitary nonseptate liver abscess
image Giardiasis and cryptosporidiosis: SB wall thickening and submucosal edema

Ultrasonographic Findings

• Grayscale ultrasound

image Amebiasis: Rounded hypoechoic right lobe liver abscess with low-level internal echoes, little distal acoustic enhancement

Imaging Recommendations

• Best imaging tool

image SBFT (ascariasis and giardiasis); barium enema, CECT (amebiasis)

DIFFERENTIAL DIAGNOSIS

Crohn Disease

• Aphthous ulcers, skip areas of SB and colon, sinus tracts into mesentery, fibrofatty extramural masses

Ulcerative Colitis

• Superficial ulcers, granular mucosa, long-segment strictures, rectal involvement

PATHOLOGY

General Features

• Associated abnormalities

image Ascariasis: SBO, pancreatobiliary obstruction
image Giardiasis: Medium-moderate blunting of SB villi
image Amebiasis: Colitis with flask-shaped ulcers

Gross Pathologic & Surgical Features

• Ascariasis: SBO (mass of worms), appendicitis, pancreatitis, cholangitis
• Giardiasis: Often grossly normal SB
• Amebiasis: Ulcerating acute colitis, toxic megacolon, large inflammatory masses (ameboma)

Microscopic Features

• Ascariasis: Mucosal destruction at worm attachment sites; inflammatory changes in appendix, pancreas, biliary tree
• Giardiasis: Villous blunting, inflammatory cells in lamina propria
• Amebiasis: Colitis with neutrophilic infiltrate and deep ulcers into submucosa

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Ascariasis: Abdominal pain, diarrhea (may be asymptomatic); biliary invasion may cause obstruction and cholangitis

–  
image Giardiasis and cryptosporidiosis: Abdominal pain, diarrhea, nausea, vomiting, distension, weight loss, malabsorption
image Amebiasis: Diarrhea, fever, GI bleeding

Demographics

• Epidemiology

image Ascariasis infests 25% of world population (especially Africa and Asia)
image Cryptosporidiosis and giardiasis are most common protozoal diseases in USA; ∼ 2-5% of general population, higher in immunosuppressed patients

–  
image Amebiasis infests 10% of world population

– Especially in developing countries with poor sanitation
– Up to 10% of Mexican population is seropositive for E. histolytica
– Most cases seen in developed countries occur in immigrants from endemic areas

Natural History & Prognosis

• Ascariasis: SBO, appendicitis, pancreatitis
• Protozoal infection: Usually self-limited in immune competent; may be life-threatening in immunosuppressed
• Amebic infection: Usually asymptomatic

image Invasive disease occurs much more frequently in children and in patients who are malnourished, immunosuppressed, or have other diseases

Treatment

• Options, risks, complications

image Ascariasis: Anthelminthic chemotherapy with mebendazole, albendazole, or pyrantel pamoate
image Giardiasis and cryptosporidiosis: Nitazoxanide or metronidazole

– Most cases need only supportive care
– Immune restoration with HAART usually causes resolution of symptoms in HIV patients
image Amebiasis: Metronidazole

DIAGNOSTIC CHECKLIST

Consider

• Consider Crohn disease, ulcerative colitis

Image Interpretation Pearls

• Linear filling defects, thickened proximal SB folds, ileocecal ulcerations
image
Spot film from a SBFT demonstrates Ascaris in the distal small bowel image.

image
Axial CECT demonstrates an amebic right lobe liver abscess with a peripheral zone of edema image.

SELECTED REFERENCES

1. Ruankham, W, et al. Prevalence of helminthic infections and risk factors in villagers of Nanglae Sub-District, Chiang Rai Province, Thailand. J Med Assoc Thai. 2014; 97(Suppl 4):S29–S35.

 

Proceedings of the IV International Giardia and Cryptosporidium Conference, 31 January–03 February 2012, Wellington, New Zealand. Infect Genet Evol. 2013; 15:1–94.

Lakshmi, SP, et al. Ascariasis: challenges in the diagnosis of single worm disease. J Indian Med Assoc. 2013; 111(9):621–622.

Moonah, SN, et al. Host immune response to intestinal amebiasis. PLoS Pathog. 2013; 9(8):e1003489.

Kao, S, et al. Education and imaging. Gastrointestinal: Amebic colitis. J Gastroenterol Hepatol. 2009; 24(1):167.

Ghonge, NP. Gastric migration of intestinal ascariasis: B-mode sonographic depiction. J Ultrasound Med. 2008; 27(12):1799–1801.

Lim, JH. Parasitic diseases in the abdomen: imaging findings. Abdom Imaging. 2008; 33(2):130–132.

Njemanze, PC, et al. High-frequency ultrasound imaging of the duodenum and colon in patients with symptomatic giardiasis in comparison to amebiasis and healthy subjects. J Gastroenterol Hepatol. 2008; 23(7 Pt 2):e34–e42.

Suzuki, A, et al. Education and imaging. Gastrointestinal: ascariasis. J Gastroenterol Hepatol. 2008; 23(11):1770.

Das, CJ, et al. Imaging of ascariasis. Australas Radiol. 2007; 51(6):500–506.

Rana, SS, et al. Parasitic infestations of the biliary tract. Curr Gastroenterol Rep. 2007; 9(2):156–164.

Ali, SA, et al. Giardia intestinalis. Curr Opin Infect Dis. 2003; 16(5):453–460.

McDonald, V. Parasites in the gastrointestinal tract. Parasite Immunol. 2003; 25(5):231–234.

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