A patient presents with sudden-onset severe scrotal pain, swelling, and erythema. Physical examination reveals a tender, swollen, and high-riding testicle. What is the most likely diagnosis?

Correct Answer: A

Rationale: Given the sudden-onset severe scrotal pain, swelling, and erythema, along with the physical examination findings of a tender, swollen, and high-riding testicle, the most likely diagnosis is testicular torsion. Testicular torsion occurs when the spermatic cord twists, leading to compromised blood flow to the testicle, causing ischemia and severe pain. It is considered a surgical emergency that requires prompt diagnosis and intervention to salvage the affected testicle. Prompt surgical detorsion is necessary to prevent irreversible testicular damage. While epididymitis, testicular trauma, and testicular tumors can also present with scrotal pain and swelling, the presence of a high-riding testicle in this context is highly suggestive of testicular torsion.

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.

Correct Answer: B

Rationale: The constellation of severe lower abdominal pain, fever, and vaginal discharge in a pregnant woman raises suspicion for pelvic inflammatory disease (PID). Cervical motion tenderness and adnexal tenderness are classic physical exam findings for PID. The presence of bilateral adnexal masses further supports the diagnosis, as PID can lead to the formation of tubo-ovarian abscesses. Ectopic pregnancy may present with similar symptoms but is less likely in this case as bilateral adnexal masses suggest a more diffuse inflammatory process. Placenta previa would typically present with painless vaginal bleeding in the third trimester, which is not consistent with the symptoms described. Ovarian torsion would present with sudden severe unilateral lower abdominal pain and is less likely to involve both ovaries simultaneously.