A patient presents with knee pain and swelling following a fall onto a flexed knee. Physical examination reveals a palpable effusion and tenderness along the joint line. McMurray's test elicits pain and clicking with passive knee flexion and internal rotation. Which condition is most likely?

Correct Answer: B

Rationale: The presentation of knee pain and swelling following a fall onto a flexed knee, along with a palpable effusion and tenderness along the joint line, is highly suggestive of a meniscus injury. The McMurray's test specifically evaluates for meniscal tears. In this case, the presence of pain and clicking with passive knee flexion and internal rotation indicates a medial meniscus tear as the most likely diagnosis. Patellar tendinitis usually presents with anterior knee pain that is worsened by activities such as jumping or running. Lateral collateral ligament (LCL) sprain typically presents with lateral knee pain and instability. Quadriceps tendon rupture would present with significant weakness and inability to fully extend the knee, which is not described in this scenario.

Correct Answer: D

Rationale: The constellation of symptoms presented (periorbital edema, hypertension, proteinuria) along with the laboratory findings (elevated creatinine and urea levels, hyperkalemia, metabolic acidosis) are classical signs of chronic kidney disease (CKD). In CKD, the kidneys gradually lose their function over time, leading to impaired filtration of waste products and electrolyte imbalance. The presence of hypertension and proteinuria are common in CKD due to the compromised renal function. Additionally, elevated serum creatinine and urea levels, hyperkalemia, and metabolic acidosis are indicative of kidney dysfunction.

Correct Answer: A

Rationale: The most likely causative agent in this scenario is Plasmodium falciparum, which is the parasite that causes malaria. The symptoms of fever, chills, headache, and myalgia following a camping trip are highly suggestive of malaria, especially if the patient has thrombocytopenia and leukopenia. Plasmodium falciparum is known to cause severe malaria with complications such as thrombocytopenia and leukopenia. The other options, Trypanosoma cruzi, Borrelia burgdorferi, and Leishmania donovani, do not typically present with all of the symptoms described and are not associated with the laboratory findings of thrombocytopenia and leukopenia.

Correct Answer: A

Rationale: The patient's symptoms of fever, chills, headache, and myalgia after returning from sub-Saharan Africa are consistent with malaria. Intraerythrocytic ring forms and trophozoites observed on blood smear examination are characteristic of Plasmodium species, particularly Plasmodium falciparum, which is the most common and deadliest species causing malaria in sub-Saharan Africa. Plasmodium falciparum can lead to severe complications, such as cerebral malaria, if not promptly treated. Trypanosoma cruzi causes Chagas disease, not malaria. Borrelia burgdorferi is responsible for Lyme disease, which typically presents with a different set of symptoms like erythema migrans rash. Leishmania donovani causes visceral leishmaniasis, not malaria.

Correct Answer: C

Rationale: Placenta previa is a condition where the placenta partially or completely covers the cervix, leading to painless vaginal bleeding during pregnancy. In the scenario described, the painless, bright red vaginal bleeding at 34 weeks gestation with a closed cervix is classic for placenta previa. This condition is more common in the third trimester and can be diagnosed through ultrasound. It is important to manage placenta previa carefully to prevent complications such as severe bleeding, preterm birth, and maternal/fetal distress.