MKSAP quiz: Prognosis in chronic kidney disease
This month's quiz asks readers to evaluate a 54-year-old man during a new patient visit. He has a 30-year history of type 2 diabetes mellitus and 10-year history of hypertension, as well as an estimated glomerular filtration rate that indicates chronic kidney disease.
A 54-year-old man is evaluated during a new patient visit. He has a 30-year history of type 2 diabetes mellitus and 10-year history of hypertension. Medical history is also significant for obesity and hypercholesterolemia. Medications are amlodipine, atorvastatin, canagliflozin, metformin, and lisinopril-hydrochlorothiazide. At his last visit to his previous physician, serum creatinine level was 1.4 mg/dL (123.8 µmol/L), and estimated glomerular filtration rate was 58 mL/min/1.73 m2.
On physical examination, blood pressure is 158/82 mm Hg, and pulse rate is 62/min; other vital signs are normal. BMI is 38. The remainder of the examination is normal.
Laboratory studies show albumin 3.5 g/dL (35 g/L), creatinine 1.6 mg/dL (141.4 µmol/L), normal electrolytes, and an estimated glomerular filtration rate of 50 mL/min/1.73 m2
Urinalysis shows no blood and 2+ protein.
Results of kidney ultrasonography and referral to an ophthalmologist for a dilated retinal examination are pending.
Which of the following is the most appropriate test to assess the prognosis of this patient's chronic kidney disease?
A. Hemoglobin A1c measurement
B. Kidney biopsy
C. Serum parathyroid hormone measurement
D. Spot urine albumin-creatinine ratio
MKSAP Answer and Critique
The correct answer is D. Spot urine albumin-creatinine ratio. This item is available to MKSAP subscribers as item 29 in the Nephrology section. More information about MKSAP is online.
The most appropriate test to help diagnose the cause and assess the prognosis of this patient's chronic kidney disease (CKD) is a spot urine albumin-creatinine ratio (Option D). CKD is defined as abnormal kidney structure or function present for >3 months. CKD is stratified into stages 1 to 5 based on the level of estimated glomerular filtration rate (eGFR). Because albuminuria is associated with increased renal and cardiovascular morbidity and mortality, eGFR-based kidney stages are modified by the degree of albuminuria. This dual eGFR and albuminuria-staging matrix provides a means for predicting which patients are at highest risk for developing end-stage kidney disease. This patient has CKD confirmed by a persistently low eGFR for at least 6 months. A spot urine albumin-creatinine ratio should be obtained to determine the degree of proteinuria. In addition to prognostication, this test will help categorize his CKD as nephrotic or non-nephrotic, which will inform diagnostic testing.
Controlling hyperglycemia in patients with diabetes mellitus will slow the progression of CKD. Although a hemoglobin A1c measurement (Option A) is important in the management of diabetes, it is not the most appropriate test to determine the cause and prognosis of CKD.
Kidney biopsy (Option B) is used to determine the cause of CKD when a glomerulonephritis or unexplained tubulointerstitial disease is likely. Kidney biopsy is not indicated in the presence of shrunken kidneys (<9 cm), which generally indicate chronic irreversible disease. Consideration of a kidney biopsy is premature for this patient, pending results of kidney ultrasonography, urine albumin-creatinine ratio, and ophthalmology examination. If retinopathy is confirmed by a dilated retinal examination and the patient has albuminuria, the most likely diagnosis in this patient with long-standing diabetes is diabetic kidney disease.
Serum parathyroid hormone (Option C), calcium, phosphorus, and 25-hydroxyvitamin D levels are indicated for management of CKD-mineral and bone disorder. Although these laboratory studies are indicated for all patients with CKD, they are not used as tests to help determine the prognosis of CKD.
Key Points
- Chronic kidney disease is defined as abnormal kidney structure or function present for >3 months.
- In patients with chronic kidney disease, albuminuria is associated with increased renal and cardiovascular morbidity and mortality.