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Parasitic Infestations of Surgical Importance in Children 143
Demographics
Ascariasis is a common problem in the tropics and subtropics, where
the moist humid climates of alternating dry season and rainy season
permit all-year embryonation of the ova of Ascaris lumbricoides. This
is further aggravated by the poor environmental standards, improper
disposal of sewage, and low socioeconomic conditions prevailing in
most cities in Africa.
Although it occurs at all ages, ascariasis is most common in children
2 to 10 years of age; the prevalence decreases after the age of 15 years.
The incidence is higher in males than females, probably because they
are more exposed to outdoor activities. Infants may be infested soon
after birth, the mother transmitting the ova with her dirty fingers. In
developing counties with poor sanitary conditions, more than 70% of
children are infested, and globally more than 1.5 billion people are
infested with Ascaris lumbricoides.
Aetiology/Pathophysiology
Ascariasis is caused by Ascaris lumbricoides, a large lumen-dwelling
nematode contracted by the consumption of its eggs. Transmission
occurs mainly via ingestion of water or food contaminated with these
eggs from human faeces and occasionally via inhalation of polluted Figure 23.1: Exceptional ascaris burden causing acute intestinal obstruction.
dust. Children playing in contaminated soil may acquire the parasite
from their dirty hands. Transplacental migration of larvae has also Eosinophilia is present in the early phases of infestation, but due to the
occasionally been reported. mixture of parasitic infestations present at the same time, it is not diagnostic.
The eggs reach the small intestine, where the larvae are liberated. Investigations
The larvae penetrate the small intestinal wall and migrate through the
lymphatics and bloodstream to the liver, and then to the lungs, where Erect plain abdominal x-ray
they enter the alveoli. There they pause for at least 2–3 weeks and Radiographs are useful in heavily infested children where the worms
molt, giving rise to allergic bronchopneumonia in previously infected appear radiolucent. A mass of worms may contrast against the gas in the
and sensitised individuals. Later, they wander up the bronchi and bowel, typically producing a “whirlpool” effect. The radiographs also
trachea, giving rise to bronchitis with bronchospasm and urticaria and show features of intestinal obstruction, such as abdominal distention,
occasionally larvae in the sputum. Most larvae are swallowed and grow dilated bowel loops, and multiple air fluid levels and free gas under the
to adulthood in the small intestine. Adult worms do not multiply in the diaphragm in cases with intestinal perforation.
human host, so the number of adult worms per infested person relates to Ultrasonography
the degree of continued exposure to infectious eggs over time. Ultrasonography may be helpful, with the round worm appearing sono-
The adult worms give rise to mechanical problems due to their size graphically as a thick echogenic strip with a central anechoic tube or
and the smaller diameter of the lumen of the bowel of children. Also, multiple long, linear, parallel echogenic strips without acoustic shadow-
due to their large number and mass, they lead to a severe nutritional ing. Curling movements of the worms may be observed on prolonged
drain in these patients. A temperature elevation to 39°C, certain drugs, scanning.
such as antihelminthic, and some unknown influences cause the worms
to congregate, sometimes resulting in intestinal obstruction (Figure Stool examination for ova
23.1) and migration out of the gut into the bile duct, oesophagus, mouth, This is not helpful where infestation rates are high.
pancreatic duct, or appendix, and occasionally the liver. Adult worms Treatment
may perforate the gut, leading to peritonitis. Sometimes, the presence Children with uncomplicated ascariasis are managed as paediatric
and activity of large numbers of worms alone may be associated with outpatients and rarely referred to the surgeon. However, following
vomiting, fever, and abdominal pain. By far, small intestinal obstruction intestinal obstruction due to ascariasis, the various options in manage-
(whether simple occlusive, intussusception, or volvulus) accounts for ment are as follows:
many of the serious pathologic effects attributed to this worm. Conservative approach
Clinical Presentation Various authors have recorded a high success rate with a conserva-
The presentation of ascariasis may be straightforward. Early symptoms tive approach. They observed that, unlike other mechanical causes of
may be related to the larval migration in the lung. In established cases, intestinal obstruction, most cases of acute intestinal obstruction due to
the child may be malnourished. Worms may have been vomited out or ascariasis can be managed conservatively. This approach is, however,
passed rectally. The difficulty, however, is in clinching the diagnosis of most suitable for mild cases with partial obstruction; it entails decom-
intestinal obstruction as a result of ascaris worms. There is, therefore, pression of the bowel, intravenous fluid replacement, antispasmodics,
need for a high index of suspicion in all cases of intestinal obstruction and anthelmintic administered after the attack has subsided.
in children. A history of a recent purgative will be important, since these Surgical approach
have been known to precipitate obstructions.
Among other presentations, pyrexia of moderate degree may be Complete obstruction should be relieved surgically after resuscitation
observed; colicky central abdominal pain may be the chief complaint; of the patient by any of the following methods:
vomiting may be frequent, either due to the activity of the worms or as • Milking: The bolus of worms is broken up and massaged into the
a result of actual obstruction; the abdomen may be generally tender; larger diameter caecum and ascending colon.
and in half the cases, an abdominal mass that is ill-defined, mobile, • Enterostomy: The antimesenteric border of the bowel is opened,
and sometimes multiple and commonly situated in the umbilical region through which the worms are carefully extracted and the resulting
may be palpable. opening repaired transversely in two layers.