What is a common consequence of an untreated roundworm infection?

A common consequence of an untreated roundworm infection is intestinal obstruction. Roundworms, particularly species such as Ascaris lumbricoides, can grow to be quite large and may inhabit the intestines, leading to physical blockages. When the roundworms multiply, they can create a mass that prevents the normal passage of food and waste through the digestive tract, resulting in serious complications. Symptoms of intestinal obstruction can include abdominal pain, vomiting, and in severe cases, it can lead to a risk of perforation of the intestine, which is a medical emergency.

Other potential health issues related to untreated roundworm infections, though serious, do not directly result in the same kind of acute obstruction as mentioned. Hepatitis is related to liver conditions and not typically caused by roundworms. Chronic fatigue may occur due to various reasons, including nutrient deficiencies from the infection, but is not the direct most common consequence. Fluid retention can arise from other complications related to gastrointestinal issues, yet does not specifically identify the primary consequence of the blockages that roundworms can cause.

Thus, intestinal obstruction is the direct result of the physical presence and mass effect of roundworms in the intestine, making it the most plausible consequence of an untreated roundworm infection.