A patient has a plasma urea concentration of 26 mg per 100 mL and a urinary urea concentration of 18.2 mg/mL. Urine flow is 2.0 mL/min. The clearance rate for urea is:

Correct Answer: B

Rationale: Urea clearance = UV/P: U=18.2 mg/mL, V=2 mL/min, P=26 mg/100 mL = 0.26 mg/mL. (18.2 × 2) / 0.26 = 36.4 / 0.26 ≈ 70 mL/min e.g., partial reabsorption. 35 underestimates half off. 105/140 overstate exceed GFR. 70 distinguishes it, critical for clearance calc, unlike wrong values.

Correct Answer: C

Rationale: Recovery in acute renal failure is marked by decreasing BUN and creatinine as glomerular filtration improves, unlike weight (fluid variable), high output (diuretic phase), or electrolyte shifts (secondary). This distinguishes renal function restoration, critical for prognosis, contrasting with earlier phases' markers.

Correct Answer: A

Rationale: High-glucose dialysate risks hyperglycemia in diabetes not liver (metabolism), heart (fluid), or lung (respiratory) issues primarily. This distinguishes glucose monitoring, key for diabetic PD patients, contrasting with other comorbidities.

Correct Answer: C

Rationale: Prostatic urethra is lined with transitional epithelium, adapting to urine flow, unlike simple columnar (glands), while penile urethra has stratified columnar/pseudostratified, and membranous is transitional. This distinguishes urethral histology, key for anatomical precision, contrasting with incorrect linings.

Correct Answer: D

Rationale: In purine synthesis, nitrogen at position 1 comes from aspartate (via adenylosuccinate), not alanine, glutamate, or glycine (other positions). This distinguishes purine biosynthesis, critical for nucleotide metabolism, contrasting with amino acid roles.