You are seeing a 12-year-old female who presented to the emergency department with the sudden onset of severe abdominal pain. Imaging that was obtained to rule out appendicitis revealed a mass adjacent to the bladder. The mass was surgically resected, and pathology demonstrated a paraganglioma. Which of the studies below would be most useful to determine disease stage for this patient?

Correct Answer: D

Rationale: The correct answer is D: Ga 68-DOTATATE PET/CT. Paragangliomas are neuroendocrine tumors that can secrete catecholamines and have a high expression of somatostatin receptors. Ga 68-DOTATATE PET/CT is the most appropriate imaging study to determine disease stage in patients with paragangliomas because it can detect the somatostatin receptor expression in these tumors, aiding in localization, staging, and treatment planning. A: Bone scan is not the most useful study for determining disease stage in paraganglioma. B: Lumbar puncture for cerebrospinal fluid cytology is not relevant for staging paraganglioma. C: Bone marrow aspirate and biopsy are not the most appropriate studies for staging paraganglioma.

Correct Answer: A

Rationale: The correct answer is A: Its half-life is about 10 days. Factor XIII has a long half-life due to its stable tetrameric structure, allowing it to circulate in the blood for about 10-14 days. This extended half-life is crucial for its role in stabilizing fibrin clots. Explanation for why other choices are incorrect: B: Factor XIII is not an activator of thrombin; rather, it crosslinks fibrin strands to strengthen clots. C: Factor XIII levels are low in newborns and gradually increase during the first few months of life. D: Factor XIII is not part of the contact activation system, which involves factors XII, XI, and prekallikrein.

Correct Answer: C

Rationale: The correct answer is C: Fresh frozen plasma (20 mL/kg), which will raise her factor XI level to 20%. Fresh frozen plasma contains various clotting factors, including factor XI. In a patient with severe factor XI deficiency, administering fresh frozen plasma can increase factor XI levels and help reduce the risk of perioperative bleeding. The dose of 20 mL/kg is appropriate for this patient's weight of 62 kg. Cryoprecipitate (choice A) may contain factor XI but is not the optimal choice for raising factor XI levels specifically. Factor XI concentrate (choice B) would be ideal but is not commonly available, making fresh frozen plasma a more practical option. Prothrombin complex concentrate (choice D) primarily contains factors II, VII, IX, and X, but not factor XI, so it would not effectively raise factor XI levels in this patient.

Correct Answer: C

Rationale: The correct answer is C: Rib tenderness. Rib tenderness would decrease suspicion for pulmonary embolism because it suggests a musculoskeletal origin of chest pain rather than a vascular one. Pulmonary embolism typically presents with symptoms such as shortness of breath, pleuritic chest pain, and sometimes cough, but rib tenderness is not a common finding in this condition. Fever is non-specific and can be present in various conditions, including pulmonary embolism. Shortness of breath is a key symptom of pulmonary embolism and would increase suspicion for this diagnosis.

Correct Answer: B

Rationale: Step 1: Agreeing to wait until week 12 of therapy before resection allows chemotherapy to shrink the tumor, making surgery easier and potentially less extensive. Step 2: Waiting until week 12 also helps assess the tumor's response to chemotherapy, guiding further treatment decisions. Step 3: Choosing not to delay the resection until week 12 may risk more extensive surgery or complications due to the tumor's size. Step 4: Opting for radiotherapy regardless of tumor resection status at week 12 is not advisable as unnecessary radiation exposure should be avoided unless absolutely necessary.