A patient with diabetes mellitus presents with polyuria, polydipsia, nocturia, and fatigue. Laboratory findings reveal hyperglycemia, glycosuria, and ketonuria. What is the most likely diagnosis?

Correct Answer: B

Rationale: The presentation of a patient with diabetes mellitus showing symptoms of polyuria, polydipsia, nocturia, and fatigue along with laboratory findings of hyperglycemia, glycosuria, and ketonuria is indicative of diabetic ketoacidosis (DKA). DKA is a serious complication of diabetes characterized by hyperglycemia, metabolic acidosis, and ketosis. The increased glucose levels lead to glycosuria, causing osmotic diuresis resulting in polyuria, polydipsia, and nocturia. The body starts breaking down fats for energy in the absence of sufficient insulin, leading to the production of ketones causing ketonuria. The patient may also experience fatigue due to the metabolic abnormalities present in DKA.

Correct Answer: B

Rationale: Benign prostatic hyperplasia (BPH) is a condition characterized by an abnormal enlargement of the prostate gland, which is non-cancerous. This enlargement can lead to lower urinary tract symptoms such as urinary hesitancy (difficulty starting the urine stream), weak urinary stream, incomplete bladder emptying, frequent urination, urgency, and nocturia. BPH is a common condition in aging men and is not usually associated with prostate cancer. Other conditions like prostate cancer, prostatitis, and prostate adenoma may present with similar symptoms, but BPH is specifically characterized by the non-cancerous enlargement of the prostate gland. Treatment for BPH may include medications to improve symptoms or surgical procedures to reduce the size of the prostate gland.

Correct Answer: A

Rationale: The clinical presentation of fever, chills, headache, and myalgia after a trip to sub-Saharan Africa is highly indicative of malaria. Specifically, the presence of intraerythrocytic ring forms and trophozoites on blood smear examination points towards Plasmodium falciparum as the most likely causative agent. Plasmodium falciparum is the most deadly of the Plasmodium species that cause malaria and is responsible for the majority of severe malaria cases worldwide. It is transmitted through the bite of infected Anopheles mosquitoes. Treatment for Plasmodium falciparum infection usually involves antimalarial medications such as artemisinin-based combination therapies.

Correct Answer: C

Rationale: Cryptosporidium parvum is a protozoan parasite often found in contaminated water sources. This parasite is known to cause watery diarrhea, abdominal cramps, and nausea in infected individuals. The presence of oocysts in the stool sample is characteristic of Cryptosporidium infection. Other parasitic infections may present with similar symptoms, but in this case, the most likely culprit based on the exposure history and laboratory findings is Cryptosporidium parvum.

Correct Answer: D

Rationale: Ovarian torsion is the most likely cause of the pregnant woman's symptoms as described. Ovarian torsion occurs when the ovary twists on its pedicle, leading to compromised blood flow to the ovary. This can cause severe abdominal pain, bloating, and constipation. On examination, an abdominal mass may be palpable due to an enlarged, twisted ovary. Bowel sounds may be diminished due to the effect of the torsion on surrounding structures. Ectopic pregnancy, threatened abortion, and placenta previa are less likely to present with an abdominal mass and diminished bowel sounds.