Parasites and Biliary stones

Ascariasis ٨
Ascariasis
Ascariasis is caused by the parasite Ascaris lumbricoides, the largest
intestinal nematode found in humans. Infection with this roundworm is
most common in tropical and subtropical countries with the majority of
infections in Southeast Asia (73%), Africa (12%), and South and Central
America (8%) (Sarinas and Chitkara, 1997).
Life cycle is characterized by an early pulmonary and later intestinal
phase that follows the ingestion of infective eggs contained in
contaminated food and soil. One of the most serious complications that
may accompany heavy intestinal infestation is biliary ascariasis
(Carpenter, 1998).
The life cycle of Ascariasis lumbricoides is complex and begins with
the ingestion of eggs. The larvae penetrate the intestinal wall and enter
the surrounding capillaries where they migrate through the lungs 1–2
weeks after the initial ingestion. In the lungs, the larvae again penetrate
the capillary walls, entering the alveolar space where they ascend the
tracheobronchial tree to the epiglottis, where they are eventually
swallowed. The larvae reach the small intestines, most commonly the
jejunum, where they mature into adult worms and they live from 10 to 24
months (Valentine et al., 2001).
Biliary involvement is the result of an erratic roundworm migration
from the bowel, which may cause threatening complications such as
cholecystitis, pancreatitis and hepatic abscesses (Sandouk et al., 1997).
Intestinal ascariasis usually remains asymptomatic, but
complications, such as appendicitis, intestinal obstruction, volvulus, or
even bowel perforation may occur (Misra et al., 1999). Migration
through the papilla of Vater can cause acute acalculous cholecystitis,