Correct Answer: B

Rationale: The correct answer is B: Hypertrophic pyloric stenosis. The "string sign" is associated with hypertrophic pyloric stenosis, a condition where the pyloric canal is narrowed, leading to gastric outlet obstruction. Intussusception (choice A) typically presents with colicky abdominal pain and currant jelly stools. Hirschsprung disease (choice C) is characterized by the absence of ganglion cells in the distal colon. Meckel diverticulum (choice D) is a congenital outpouching of the small intestine that can present with painless rectal bleeding.

Correct Answer: B

Rationale: Teaching infection control measures is crucial as Hepatitis A is highly contagious, especially in household settings. Proper hand hygiene and avoiding sharing personal items can prevent the spread of the virus within the family. Option A is incorrect because bed rest is not typically required for hepatitis A. Option C is incorrect as the child can return to school once feeling well and no longer contagious, not necessarily after a specific duration. Option D is incorrect because hepatitis A can be transmitted through contaminated food, water, or close personal contact.

Correct Answer: D

Rationale: Intussusception is the correct answer. It refers to the condition where one segment of the bowel folds into another, leading to an obstruction. Atresia (Choice A) is the absence or abnormal closure of a normal opening or tubular structure. Stenosis (Choice B) is the narrowing of a passage in the body. Herniation (Choice C) is the abnormal protrusion of an organ or tissue through a defect in its surrounding walls. Intussusception is a medical emergency commonly observed in infants and young children and necessitates prompt intervention to prevent severe complications.

Correct Answer: D

Rationale: Excessive vomiting in pyloric stenosis leads to the loss of stomach acid (hydrochloric acid), resulting in metabolic alkalosis, not hyperkalemia, hyperchloremia, or metabolic acidosis. Metabolic alkalosis is characterized by a higher pH level in the blood due to the loss of acid and a relative increase in bicarbonate. Hyperkalemia is an elevated level of potassium in the blood and is not directly related to excessive vomiting in pyloric stenosis. Hyperchloremia is an excess of chloride in the blood, which is not typically associated with this condition. Metabolic acidosis is a condition characterized by a lower pH level in the blood, caused by an excess of acid or a loss of bicarbonate, which is not the typical complication seen in pyloric stenosis with excessive vomiting.

Correct Answer: C

Rationale: The most important intervention in managing a child with sickle cell crisis is the administration of pain relief. During a sickle cell crisis, severe pain is a prominent symptom due to vaso-occlusive episodes. Effective pain management, along with adequate hydration and oxygen therapy, is crucial in treating a sickle cell crisis and preventing further complications. Choice A, the administration of iron supplements, is not the priority during a sickle cell crisis. Iron supplements are typically used to manage anemia in individuals with sickle cell disease but are not the primary intervention during a crisis. Choice B, the initiation of a high-calorie diet, is not the most critical intervention during a sickle cell crisis. While proper nutrition is important in managing sickle cell disease, it is not the immediate priority during a crisis. Choice D, limiting fluid intake, is not recommended during a sickle cell crisis. Hydration is essential in managing sickle cell crisis to prevent complications like dehydration and further vaso-occlusive episodes.