A patient with a history of nephrolithiasis presents with sudden-onset severe colicky flank pain radiating to the groin. On physical examination, there is tenderness over the costovertebral angle and hematuria. What is the most likely diagnosis?

Correct Answer: C

Rationale: The correct answer is C: Renal colic due to ureteral calculus. The sudden-onset severe colicky flank pain radiating to the groin along with tenderness over the costovertebral angle and hematuria are classic symptoms of kidney stones (ureteral calculus). The pain results from the obstruction of urine flow by the stone, leading to increased pressure and spasm in the ureter. Acute pyelonephritis (choice A) presents with fever, chills, and systemic symptoms. Renal artery embolism (choice B) typically presents with acute onset severe flank pain but is associated with risk factors like atrial fibrillation. Renal infarction (choice D) presents with sudden-onset severe flank pain but is less likely than ureteral calculus in a patient with a history of nephrolithiasis.

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

Correct Answer: B

Rationale: In this scenario, the pregnant woman is presenting with severe abdominal pain, passage of tissue, and cervical dilation with products of conception protruding through the cervical os at 12 weeks gestation. These are classic signs and symptoms of an incomplete abortion. Incomplete abortion occurs when not all of the products of conception are expelled from the uterus. It can present with vaginal bleeding, abdominal pain, cervical dilation, and passage of tissue. The management of incomplete abortion may involve expectant, medical, or surgical options depending on the clinical context and the patient's condition.