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Chapter 48: Sickle Cell Nephropathy

A 21-year-old African–American man presented to the emergency room with a chief complaint of painless pinkish urine. He has no significant past medical history except for known sickle cell trait. Physical examination: afebrile, blood pressure 100/70 mm Hg, heart rate 76 beats/min, temperature 98.7oF, and respiratory rate 16 breaths/min. His examination is unremarkable. Urinalysis shows 3+ blood and >800 red blood cells per high power field. The patient was sent home on ciprofloxacin for presumed urinary tract infection. Three months later he represented to the emergency room with flank pain, recurrent gross hematuria, weight loss, chest pain, shortness of breath, and lightheadedness. Pan-body CT scan was performed to evaluate weight loss. Chest CT showed bilateral pulmonary nodules, hilar lymphadenopathy, and multiple vertebral lesions.

Which one of the following is the most likely cause of his hematuria?

A. Pyelonephritis

B. Renal cell medullary carcinoma

C. Papillary necrosis

D. Kidney stone

The answer is B. Renal medullary cancer occurs almost exclusively in patients with sickle cell trait at a relatively young age (20–30 year old) as aggressive metastatic disease at the time of diagnosis. Patient may present with hematuria, flank pain, abdominal mass, or weight loss.

A 19-year-old African–American man with SCD presented to your office for a preathletic physical. He described himself as healthy and physically active. He denied history of pharyngitis, tonsillitis or skin infection. He consumes 11 oz of premier protein drink with meals three times daily. His vital signs were: blood pressure 106/70 mm Hg, heart rate 76 beats/min, temperature 98.6oF, and respiratory rate 12 breaths/min. His examination was notable for pale conjunctivae and nailbeds. His lungs were clear to auscultation and percussion. He was noted to have a soft grade 1/6 systolic ejection murmur. His abdomen was soft, nondistended and nontender and he had no peripheral edema.

Laboratory findings:

Sodium 139 mEq/L, potassium 4.2 mEq/L, chloride 105 mEq/L, bicarbonate 24 mEq/L, blood urea nitrogen 8 mg/dL, creatinine 0.4 mg/dL, WBC count 4.2 cells/uL, hemoglobin 6.8 g/dL, hematocrit 19%, platelet count 230,000/mmol. Urinalysis: specific gravity 1.012, pH 5.5, trace blood, and trace protein. Urinary albumin to creatinine ratio is 100 ug/mg.

The patient was advised to refrain from physical activities and return in 2 weeks for follow-up. Repeat urine studies at 2 week follow-up reveal persistent microalbuminuria.

Which one of the following is a plausible explanation for microalbuminuria?

A. Loss of glomerular permselectivity

B. Protein drink

C. Rigorous exercise

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