A patient presents with acute onset of shoulder pain and limited range of motion after a fall onto an outstretched hand. Physical examination reveals tenderness over the greater tuberosity of the humerus and pain with passive abduction and external rotation of the shoulder. Which of the following conditions is most likely?

Correct Answer: A

Rationale: The correct answer is A: Rotator cuff tear. The presentation of acute shoulder pain and limited range of motion after a fall onto an outstretched hand, along with tenderness over the greater tuberosity and pain with passive abduction and external rotation, is classic for a rotator cuff tear. The mechanism of injury and physical exam findings are consistent with this condition. B: Glenohumeral dislocation typically presents with a visibly deformed shoulder and loss of normal shoulder contour. C: Acromioclavicular joint separation would present with tenderness over the AC joint rather than the greater tuberosity, and typically involves a history of direct trauma to the shoulder. D: Proximal humerus fracture would present with more diffuse shoulder pain and swelling, and not specific tenderness over the greater tuberosity.

Correct Answer: B

Rationale: The most appropriate initial management for the patient described is hemodialysis. Hemodialysis is essential for managing chronic kidney disease with severe symptoms and electrolyte imbalances like hyperkalemia and metabolic acidosis. Hemodialysis helps to remove urea and creatinine from the blood, correct electrolyte abnormalities, and improve symptoms such as fatigue, dyspnea, and peripheral edema. Initiation of ACE inhibitor therapy (Choice A) is contraindicated in severe kidney disease due to the risk of worsening renal function. Intravenous administration of calcium gluconate (Choice C) is used for acute hyperkalemia with cardiac toxicity, not for initial management. Sodium bicarbonate administration (Choice D) may help correct metabolic acidosis, but it does not address the underlying cause or the need for urgent renal replacement therapy.

Correct Answer: B

Rationale: The correct answer is B: Acute glomerulonephritis. Glomerulonephritis is characterized by inflammation of the glomeruli in the kidneys, leading to symptoms like hematuria (blood in urine), proteinuria (excess protein in urine), and hypertension (high blood pressure). Acute tubular necrosis (A) involves damage to the renal tubules, not the glomeruli. Chronic kidney disease (C) refers to long-term kidney damage and may not always present with the classic symptoms mentioned. Nephrotic syndrome (D) involves excessive protein loss in urine but may not always involve inflammation of the glomeruli.

Correct Answer: C

Rationale: The correct answer is C: Cryptosporidium parvum. This parasite is the most likely cause of the infection due to its presentation with watery diarrhea, abdominal cramps, and nausea after consuming contaminated water. Laboratory tests revealing oocysts in the stool sample further support this diagnosis as Cryptosporidium parvum is known to produce oocysts in the stool. Giardia lamblia (choice A) presents with similar symptoms but does not typically produce oocysts. Entamoeba histolytica (choice B) is more associated with bloody diarrhea and liver abscesses. Cyclospora cayetanensis (choice D) is also associated with watery diarrhea but is less common in this scenario. Thus, based on the symptoms and laboratory findings, Cryptosporidium parvum is the most likely culprit.

Correct Answer: A

Rationale: The correct answer is A: Plasmodium falciparum. Plasmodium falciparum is the most likely causative agent because the patient's symptoms of fever, chills, headache, and myalgia, along with the presence of intraerythrocytic ring forms and trophozoites on blood smear, are characteristic of malaria, particularly caused by P. falciparum in sub-Saharan Africa. Summary of other choices: B: Trypanosoma cruzi causes Chagas disease, which presents with symptoms like fever, rash, and swelling at the site of entry, not consistent with the patient's presentation. C: Borrelia burgdorferi causes Lyme disease, which typically presents with a characteristic rash (erythema migrans) and arthritis, not matching the patient's symptoms. D: Leishmania donovani causes visceral leishmaniasis, which presents with symptoms like weight loss, hepatosplen