Clinical estimation of GFR — MCQs

A healthy 30-year-old female has a measured creatinine clearance of 100 mL/min. She has a filtration fraction (FF) of 25%. Serum analysis reveals a creatinine level of 0.9 mg/dL and an elevated hematocrit of 0.6. Which of the following is the best estimate of this patient’s renal blood flow?

A 39-year-old woman is brought to the emergency department in a semi-unconscious state by her neighbor who saw her lose consciousness. There was no apparent injury on the primary survey. She is not currently taking any medications. She has had loose stools for the past 3 days and a decreased frequency of urination. No further history could be obtained. The vital signs include: blood pressure 94/62 mm Hg, temperature 36.7°C (98.0°F), pulse 105/min, and respiratory rate 10/min. The skin appears dry. Routine basic metabolic panel, urine analysis, urine osmolality, and urine electrolytes are pending. Which of the following lab abnormalities would be expected in this patient?

A laboratory technician processes basic metabolic panels for two patients. Patient A is 18 years old and patient B is 83 years old. Neither patient takes any medications regularly. Serum laboratory studies show: Patient A Patient B Na+ (mEq/L) 145 141 K+ (mEq/L) 3.9 4.4 Cl- (mEq/L) 103 109 HCO3- (mEq/L) 22 21 BUN (mg/dL) 18 12 Cr (mg/dL) 0.8 1.2 Glucose (mg/dL) 105 98 Which of the following most likely accounts for the difference in creatinine seen between these two patients?

A 32-year-old man is brought to the Emergency Department after 3 consecutive days of diarrhea, fatigue and weakness. His stool has been soft and mucoid, with no blood stains. The patient just came back from a volunteer mission in Guatemala, where he remained asymptomatic. His personal medical history is unremarkable. Today his blood pressure is 98/60 mm Hg, pulse is 110/min, respiratory rate is 19/min, and his body temperature is 36.7°C (98.1°F). On physical exam, he has sunken eyes, dry mucosa, mild diffuse abdominal tenderness, and hyperactive bowel sounds. Initial laboratory tests are shown below: Serum creatinine (SCr) 1.8 mg/dL Blood urea nitrogen (BUN) 50 mg/dL Serum sodium 132 mEq/L Serum potassium 3.5 mEq/L Serum chloride 102 mEq/L Which of the following phenomena would you expect in this patient?

An investigator is attempting to assess the glomerular filtration rate (GFR) of a healthy adult volunteer. The volunteer's inulin clearance is evaluated under continuous inulin infusion and urine collection and compared to the creatinine clearance. It is found that the estimated GFR based on the volunteer's creatinine clearance is 129 mL/min and the estimated GFR calculated using the inulin clearance is 122 mL/min. Which of the following is the best explanation for the difference in these measurements?

A researcher is investigating the effects of a new antihypertensive medication on renal physiology. She gives a subject a dose of the new medication, and she then collects plasma and urine samples. She finds the following: Hematocrit: 40%; Serum creatinine: 0.0125 mg/mL; Urine creatinine: 1.25 mg/mL. Urinary output is 1 mL/min. Renal blood flow is 1 L/min. Based on the above information and approximating that the creatinine clearance is equal to the GFR, what answer best approximates filtration fraction in this case?

A 58-year-old Caucasian woman visits her primary care physician for an annual check-up. She has a history of type 2 diabetes mellitus and stage 3A chronic kidney disease. Her estimated glomerular filtration rate has not changed since her last visit. Today, her parathyroid levels are moderately elevated. She lives at home with her husband and 2 children and works as a bank clerk. Her vitals are normal, and her physical examination is unremarkable. Which of the following explains this new finding?

A 68-year-old woman presents to her primary care physician for a regular check-up. She complains of swelling of her legs and face, which is worse in the morning and decreases during the day. She was diagnosed with type 2 diabetes mellitus a year ago and prescribed metformin, but she has not been compliant with it preferring 'natural remedies' over the medications. She does not have a history of cardiovascular disease or malignancy. Her vital signs are as follows: blood pressure measured on the right hand is 130/85 mm Hg, on the left hand, is 110/80 mm Hg, heart rate is 79/min, respiratory rate is 16/min, and the temperature is 36.6℃ (97.9°F). Physical examination reveals S1 accentuation best heard in the second intercostal space at the right sternal border. Facial and lower limbs edema are evident. The results of the laboratory tests are shown in the table below. Fasting plasma glucose 164 mg/dL HbA1c 10.4% Total cholesterol 243.2 mg/dL Triglycerides 194.7 mg/dL Creatinine 1.8 mg/dL Urea nitrogen 22.4 mg/dL Ca2+ 9.6 mg/dL PO42- 3.84 mg/dL Which of the following statements best describes this patient's condition?

A 9-year-old boy is brought to the physician's office by his mother because of facial swelling for the past 2 days. The mother says that her son has always been healthy and active but is becoming increasingly lethargic and now has a puffy face. Upon inquiry, the boy describes a foamy appearance of his urine, but denies having blood in the urine, urinary frequency at night, or pain during urination. He has no history of renal or urinary diseases. Physical examination is unremarkable, except for generalized swelling of the face and pitting edema on the lower limbs. Dipstick analysis reveals 4+ proteinuria. An abdominal ultrasound shows normal kidney size and morphology. A renal biopsy yields no findings under light and fluorescence microscopy; however, glomerular podocyte foot effacement is noted on electron microscopy. Which of the following changes in Starling forces occurs in this patient's condition?

A 70-year-old female with chronic kidney failure secondary to diabetes asks her nephrologist to educate her about the techniques used to evaluate the degree of kidney failure progression. She learns about the concept of glomerular filtration rate (GFR) and learns that it can be estimated by measuring the levels of some substances. The clearance of which of the following substances is the most accurate estimate for GFR?