Nephrology Case Challenge: Man on Keto Diet Has Severe Diarrhea and Neurogenic Bladder

C. Elena Cervantes, MD


February 06, 2023

Physical Examination and Workup

Upon examination, the patient appears thin and chronically ill. His vital signs include a temperature of 96.8 °F (36 °C) and a sitting blood pressure of 90/60 mm Hg with a heart rate of 82 beats/min, which decreases to 75/50 mm Hg with a heart rate of 90 beats/min within 3 minutes of standing. His respiration rate is 16 breaths/min. His cardiopulmonary examination is unremarkable, with 2+ peripheral edema in both lower extremities.

His complete blood cell count is within normal ranges, except for anemia (hemoglobin level, 9.8 g/dL [reference range, 13.8-17.2 g/dL]) and thrombocytopenia (98,000 cells/μL [reference range, 150,000-450,000 cells/μL]). His basic metabolic panel shows low serum albumin (3.2 g/dL [reference range, 3.5-5.3 g/dL]), low total protein (6 g/dL [reference range, 6-8.2 g/dL]), and elevated creatinine (1.6 mg/dL [reference range, 0.6-1 mg/dL]) levels. Other laboratory parameters are unremarkable. His urinalysis findings are "bland," with no hematuria or pyuria. Renal ultrasonography reveals a distended bladder but no hydronephrosis.

A review of the patient's records shows that the creatinine level ranged between 1.1 and 1.3 mg/dL for the past 3 years, peaking at 2.1 mg/dL during prerenal azotemia associated with diarrhea and hypovolemia episodes. Over the past year, his creatinine level ranged between 1.5 and 1.6 mg/dL, with an estimated glomerular filtration rate (eGFR) of 42-46 mL/min based on the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. He had 300 mg of proteinuria in a 24-hour urine collection (normal level < 150 mg in 24 hours) without evidence of albuminuria.

Approximately 2 years ago, an immunoglobulin (Ig) A lambda monoclonal band was identified on serum immunofixation (772 mg/dL [reference range, 82-453 mg/dL]), but serum and urine electrophoresis results were unremarkable. His free light chain ratio was reported as normal (0.39 [reference range, 0.26-1.65]), with free kappa light chains of 17.6 mg/L (reference range, 3.3-19.4 mg/L) and free lambda light chains of 45.6 mg/L (reference range, 5.7-26.3 mg/L).


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