Case presentation:
A 29 year old man with a history of bipolar (manic-depressive) disorder who has been treated
with lithium for 7 years now presents with progressive renal failure and new onset orthostatic
hypotension.
Over the past year, the patient has experienced polyuria, polydipsia and mild renal
insufficiency with a serum creatinine level maintained near 2 mg/dl (normal 0.7-1.4 mg/dl).
There was no family history of renal disease.
On physical exam, the patient was afebrile, with a heart rate of 100 bpm and a blood pressure
of 120/90.
Laboratory testing revealed:
Urine specific gravity 1.007
BUN 50 mg/dl
Serum creatinine 4 mg/dl
Serum sodium 158 meq/l
Important negative findings:
- Erythrocyte sedimentation rate and IgA levels were not elevated.
- Serum complement was not decreased and a test for anti-nuclear antibodies was negative.
- An intravenous pyelogram and renal ultrasound were normal.
Questions:
- What are the most important laboratory findings?
- What is the patient's primary problem?
- Does the patient have prerenal azotemia?
- Why are the negative findings important?
- What other test might you order on a patient with similar physical findings and test results?
