Regarding renal colic secondary to calculi:

Correct Answer: C

Rationale: The correct answer is C because renal colic can present without hematuria. Renal colic is typically associated with severe flank pain caused by ureteral stones. Hematuria is a common symptom but not always present. This is due to the stone's location and size affecting the degree of irritation and damage to the urinary tract. Therefore, the absence of hematuria does not exclude the possibility of renal colic. Choices A, B, and D are incorrect. Females are not more commonly affected than males, calculi can be either radio-opaque or radio-lucent, and the recurrence rate by 5 years is closer to 50% rather than 20%.

Correct Answer: C

Rationale: The correct answer is C: Men with a history of cryptorchidism are at the greatest risk for the development of testicular cancer. This is because cryptorchidism, which is the condition of undescended testicles, is a known risk factor for testicular cancer. When the testicles do not descend properly, there is an increased likelihood of cancer development. This statement is true as individuals with cryptorchidism have a higher risk of testicular cancer compared to those without this condition. Other choices are incorrect: A: Testicular cancer is not the most common cancer in men aged 30 to 50 years. Prostate cancer is more common in this age group. B: The early symptoms of testicular cancer are not pain and induration. Common symptoms include painless testicular swelling or a lump. D: The cure rate for testicular cancer is actually high, especially when detected early. This statement is incorrect.

Correct Answer: D

Rationale: The correct answer is D because the presence of yellowish 1-cm nodules that are firm and nontender on the scrotal skin could indicate a serious issue such as testicular cancer or a benign condition like sebaceous cysts. Further evaluation is necessary to rule out malignancy or infection. A: Skin on the scrotum being taut is a normal finding. B: Left testicle hanging lower than the right is a common anatomical variation, not a cause for concern. C: The absence of information makes it impossible to determine if this finding requires follow-up.

Correct Answer: B

Rationale: Step-by-step rationale for choice B being correct: 1. Renal autoregulation maintains a constant glomerular filtration rate (GFR). 2. If the collecting tubule reabsorbs less water, it helps regulate the body's fluid balance. 3. Reabsorbing less water in the collecting tubule helps prevent excessive fluid loss or retention. 4. This process ensures that the body maintains appropriate blood volume and blood pressure. Summary of why other choices are incorrect: A: Loop of Henle reabsorbs ions, not more sodium and chloride ions. C: Afferent arterioles constrict to decrease GFR, not dilate to increase it. D: Efferent arterioles constrict to maintain GFR, not dilate to allow faster blood flow.

Correct Answer: D

Rationale: The correct answer is D because tubular reabsorption refers to the process of reabsorbing substances, including water, from the renal tubules back into the bloodstream. This process occurs mainly in the proximal convoluted tubule and loop of Henle, not the distal convoluted tubule as stated in choice B. Choice A is incorrect because tubular reabsorption does not specifically eliminate wastes; that is the role of tubular secretion. Choice C is incorrect because tubular reabsorption does not directly control blood pH by removing H+ ions from the filtrate; that is primarily done through the kidneys' buffering systems. Overall, choice D is the most accurate as it reflects the primary function of tubular reabsorption in returning water back to the blood.