A patient arrived in the emergency room with a fever of 38.5 °C. Change the temperature to Fahrenheit.

Choice A rationale

Inflammation of the gallbladder, or cholecystitis, typically causes pain in the right upper quadrant of the abdomen, often radiating to the right shoulder or back. While percussion can elicit tenderness, the primary location of pain is not the costovertebral angle, which is anatomically associated with the kidneys.

Choice B rationale

Sharp pain along the costovertebral angles (CVA) during percussion is a classic clinical sign known as CVA tenderness. This finding is highly indicative of inflammation or infection of the kidneys, such as pyelonephritis. The kidneys are retroperitoneal organs located just below the twelfth rib, making them directly accessible to percussion at this anatomical landmark.

Choice C rationale

Enlargement of the liver, or hepatomegaly, is typically assessed by palpation and percussion of the right upper quadrant, below the costal margin. While it can cause discomfort, liver enlargement does not primarily manifest as pain at the costovertebral angles upon percussion.

Choice D rationale

Pancreatitis, inflammation of the pancreas, usually causes severe epigastric pain that often radiates to the back. While it is a retroperitoneal organ, its anatomical location and the nature of the pain differ significantly from the localized tenderness elicited at the costovertebral angles during percussion.

Choice A rationale

An intradermal injection is administered into the dermis, the layer of skin directly beneath the epidermis. A 15-degree angle ensures the needle enters superficially, creating a small wheal as the medication is deposited. This shallow angle minimizes penetration into subcutaneous tissue, which is crucial for proper antigen-antibody reactions in allergy testing or tuberculosis screening.

Choice B rationale

A 90-degree angle is used for intramuscular injections, where the medication is delivered deep into muscle tissue. This angle allows for rapid absorption due to the rich vascular supply of muscle, but it would cause excessive penetration and potential systemic absorption if used for an intradermal injection, negating its diagnostic purpose.

Choice C rationale

A 45-degree angle is typically used for subcutaneous injections, delivering medication into the adipose tissue layer beneath the dermis. This angle is too deep for an intradermal injection and would result in the medication being absorbed systemically rather than remaining in the dermal layer for localized diagnostic reactions.

Choice D rationale

A 30-degree angle is also too steep for an intradermal injection. While less deep than a 45-degree angle, it still risks penetrating beyond the dermis into the subcutaneous tissue. The goal of an intradermal injection is to deposit the substance within the highly specific dermal layer to elicit a localized, measurable response.