Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 22-year-old man comes for a routine evaluation. He has a history of type 1 diabetes mellitus and began taking insulin glargine and insulin lispro 8 years ago. Two days ago, he participated in a marathon race.
On physical examination, temperature is 36.4 °C (97.5 °F), blood pressure is 112/70 mm Hg, pulse rate is 60/min, and respiration rate is 15/min. BMI is 24 kg/m2. Funduscopic examination is normal. There is normal sensation in the extremities.
Laboratory studies:
| Hemoglobin A1c | 5.8% |
| Urinalysis | Normal |
| Urine albumin-creatinine ratio | 100 mg/g |
In addition to refraining from heavy exercise, which of the following is the most appropriate next step in this patient’s management?
A) Begin losartan
B) Perform kidney biopsy
C) Repeat urine albumin-creatinine ratio in 1 year
D) Repeat urine albumin-creatinine ratio in 2 weeks
The correct answer is D) Repeat urine albumin-creatinine ratio in 2 weeks. This item is available to MKSAP 15 subscribers as item 15 in the Nephrology section. More information about MKSAP 15 is available online.
Annual measurement of the urine albumin excretion is indicated for patients with type 1 diabetes mellitus. However, because this patient’s albumin excretion was abnormal, repeat testing in less than 1 year is warranted in order to determine whether his proteinuria is transient or persistent. Fever and exercise can cause a transient increase in protein excretion, and this patient’s participation in a marathon 2 days ago may explain his proteinuria. Repeat urinalyses should be performed twice within the next 6 months, and the presence of microalbuminuria (defined as a urine albumin-creatinine ratio between 30 and 300 mg/g) would be confirmed if two of the three urine samples are positive. Therefore, in this patient, repeat urinalysis in 2 weeks is reasonable.
Kidney biopsy is not indicated unless the presence of proteinuria has been established.
Microalbuminuria is the first detectable manifestation of diabetic nephropathy and typically occurs 5 to 15 years after the diagnosis of type 1 diabetes mellitus, but a diagnosis of microalbuminuria has not yet been confirmed in this patient. Diabetic nephropathy also is typically associated with hypertension and diabetic retinopathy, which are absent in this patient. Treatment for diabetic nephropathy with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker is not appropriate at this time.
Key Point
- Because factors such as fever and exercise can cause a transient increase in protein excretion, patients with type 1 diabetes mellitus who have abnormal findings on annual measurement of the urine albumin excretion should undergo repeat urinalyses twice within the next 6 months; positive findings on two of the three urine samples would confirm a diagnosis of microalbuminuria (defined as a urine albumin-creatinine ratio between 30 and 300 mg/g).
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