A 3-year-old girl is seen in the emergency depament with acute abdominal pain. She has a 5-day history of vomiting and abdominal distension. She has not passed stool during this time, and during the past day, has been vomiting bilious material. On physical examination, she is lethargic, with a firm and tender abdomen, and peritoneal signs are present. She is immediately referred for laparotomy for suspected diagnosis of intussusception vs. volvulus. At surgery, approximately 20 cm of small intestine is found to be markedly distended, and is resected. The section contains a tightly knotted ball of nematodes that are about 15 to 35 cm in length. The worms have tapered ends without hooks. Pa of the life cycle of this patient’s parasite is a filarial stage in which larvae, hatched in the duodenum, penetrate the wall of the small intestine. The passage of migrating larvae most commonly produces symptomatic disease in which of the following organs?
A 3-year-old girl is seen in the emergency depament with acute abdominal pain. She has a 5-day history of vomiting and abdominal distension. She has not passed stool during this time, and during the past day, has been vomiting bilious material. On physical examination, she is lethargic, with a firm and tender abdomen, and peritoneal signs are present. She is immediately referred for laparotomy for suspected diagnosis of intussusception vs. volvulus. At surgery, approximately 20 cm of small intestine is found to be markedly distended, and is resected. The section contains a tightly knotted ball of nematodes that are about 15 to 35 cm in length. The worms have tapered ends without hooks. Pa of the life cycle of this patient’s parasite is a filarial stage in which larvae, hatched in the duodenum, penetrate the wall of the small intestine. The passage of migrating larvae most commonly produces symptomatic disease in which of the following organs?
💡 Explanation
## **Core Concept**
The question describes a case of intestinal obstruction caused by a parasitic infection. The key details provided are the presence of a "tightly knotted ball of nematodes" in the resected intestine and a life cycle that includes a filarial stage with larvae penetrating the intestinal wall. This points towards an infection caused by a type of nematode (roundworm).
## **Why the Correct Answer is Right**
The description of the worms as having "tapered ends without hooks" and being about 15 to 35 cm in length, along with the life cycle details, is indicative of *Ascaris lumbricoides* (the large roundworm). A key part of the life cycle of *As. lumbricoides* involves the migration of larvae through the lungs. During this migratory phase, the larvae can cause significant inflammation and damage to lung tissue. Therefore, the symptomatic disease most commonly produced by the passage of migrating larvae of this parasite is in the **lungs**, leading to conditions such as Löffler's syndrome, characterized by pulmonary infiltrates and eosinophilia.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While the intestine is the final site of infection for *As. lumbricoides*, the question specifically asks about the organ most commonly affected by the migrating larvae, which is not the intestine but the lungs.
- **Option B:** The liver is involved in the initial phase of larval migration (via the portal vein), but it's not the organ most commonly associated with symptomatic disease caused by migrating larvae.
- **Option C:** The skin is not directly involved in the typical migratory pathway of *As. lumbricoides* larvae; they do not penetrate the skin to enter the host.
- **Option D:** The **lungs** are the correct site, making other options incorrect by the process of elimination.
## **Clinical Pearl / High-Yield Fact**
A memorable point for exams is that *Ascaris lumbricoides* infection can cause respiratory symptoms during the larval migration phase, such as cough and wheezing, due to the larvae passing through the lungs. This phase can sometimes be confused with asthma or other respiratory conditions.
## **Correct Answer:** . **Lungs**
✓ Correct Answer: C. Lungs
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