Symptoms and diagnosis

Symptoms of kidney toxicity include fatigue, dehydration, polyuria (the passage of a large volume of urine), polydipsia (excessive or abnormal thirst), high blood pressure and a rapid heart rate.

It is usually diagnosed by testing for the presence of protein in the urine or by measuring the levels of a protein called creatinine in the blood. Kidney function is said to be impaired if levels of creatinine in the blood are elevated or if clearance of creatinine is below 60ml/min. A positive diagnosis is usually confirmed with an ultrasound scan and possibly analysis of a sample of kidney tissue.

A measure called glomerular filtration rate is emerging as a more sensitive method for the diagnosis of kidney disease in HIV-positive patients.¹ This is a measure of the filtering activity of the kidneys, calculated using the creatinine level, age, gender, weight and body size. (See Kidney toxicity - Symptoms and diagnosis in Side-effects and Renal function tests in A to Z of tests.)

Fanconi syndrome is a disorder of the proximal renal tubes of the kidneys, where electrolytes and nutrients are not properly absorbed back into the body. Low levels of phosphorous in the blood (hypophosphataemia) is a sign of kidney impairment associated with Fanconi's syndrome.

Recent guidelines for HIV-positive patients from the Infectious Diseases Society of America have recommended screening for kidney disease at the time of HIV diagosis. Thereafter, patients at high risk of developing kidney disease should be screened every year. These include people of African descent, those with CD4 cell counts below 200 cells/mm³ or viral loads above 4000 copies/ml, and those with diabetes, high blood pressure or hepatitis C co-infection.²