What complication may occur as a result of hyperparathyroidism?

Choice A rationale

While the lymphatic system is involved in managing interstitial fluid, erythema is specifically a vascular phenomenon. The lymphatic system's primary role after an injury is to drain the excess fluid and debris that accumulate in the tissues, which helps reduce edema (swelling) rather than causing the red color. Erythema is caused by an increase in the volume of oxygenated blood in the superficial dermis, which is not a function of the lymphatic vessels.

Choice B rationale

Following a bone fracture, the body initiates an acute inflammatory response. Damaged mast cells and platelets release chemical mediators like histamine and bradykinin. These substances cause local vasodilation, which is the widening of the blood vessels at the injury site. This increased blood flow, known as hyperemia, brings essential white blood cells and nutrients to the area to begin the repair process. The surge of red, oxygenated blood near the skin surface produces erythema.

Choice C rationale

Increased capillary permeability is indeed a part of the inflammatory process, but it is primarily responsible for the development of edema, not erythema. When capillaries become "leaky," protein-rich fluid escapes into the interstitial space, causing tissue swelling. Erythema is specifically defined by the redness of the skin, which is the direct result of vasodilation and increased blood flow to the area, whereas permeability changes focus on the movement of fluid out of the vessels.

Choice D rationale

The immune system does not typically block lymphatic drainage as a standard response to a fracture. In fact, an efficient lymphatic system is necessary to clear the inflammatory exudate. If the lymphatic system were blocked, it would lead to severe, localized lymphedema, but it would not be the primary cause of the redness seen immediately after an injury. Erythema is an active process of bringing blood to the site, not a passive result of blocked drainage.

Choice A rationale

Syndrome of inappropriate antidiuretic hormone involves the excessive release of ADH, leading to significant water reabsorption in the renal collecting ducts. This process results in the production of highly concentrated urine and a marked decrease in total urine volume, known as oliguria. Normal urine output is typically ≥ 0.5 mL/kg/hr. In SIADH, the kidneys continue to retain water inappropriately despite the body being in a state of fluid volume excess, leading to concentrated urine.

Choice B rationale

Patients with SIADH typically experience rapid weight gain rather than weight loss. This weight gain is the direct result of excessive free water retention caused by the high levels of circulating antidiuretic hormone. The retained water expands the extracellular and intracellular fluid compartments. Unlike heart failure or renal failure, this fluid accumulation usually does not present with visible peripheral edema because the water is distributed evenly throughout all body fluid compartments.

Choice C rationale

Increased thirst is generally suppressed in SIADH because the patient is already in a state of fluid overload and has low serum osmolality. Thirst is a physiological response usually triggered by dehydration or high serum sodium levels. In SIADH, the serum is diluted by excess water, dropping the sodium concentration often below 135 mEq/L. Consequently, the brain's thirst center is not stimulated, and patients must often be restricted to less than 800 mL of fluid daily.

Choice D rationale

SIADH is characterized by dilutional hyponatremia, not hypernatremia. The excessive retention of free water dilutes the total amount of sodium in the extracellular fluid, resulting in serum sodium levels that are lower than the normal range of 135 to 145 mEq/L. Hypernatremia would involve a sodium concentration > 145 mEq/L and is typically seen in conditions where water is lost in excess of solute, such as diabetes insipidus, which is the physiological opposite of SIADH.