Evaluation of renal function in human visceral leishmaniasis (kala-azar): a prospective study on 50 patients from Brazil

Background: There are few studies of renal function evaluation in visceral leishmaniasis (kala-azar). The aim of this study was to evaluate glomerular filtration rate (GFR) and tubular function as urinary acidification capacity and maximal urinary concentration, in patients with the chronic form of kala-azar. Patients and methods: This is a cross-sectional study of 50 consecutive patients with kala-azar. GFR was calculated by 24-hour creatinine clearance. Urinary pH, titratable acidity and urinary ammonia excretion were measured after acidloading with NH4Cl. Urine to plasma osmolality ratio (U/Posm) was evaluated after water withdrawal and vasopressin administration. All parameters were also measured in 20 healthy volunteers (control group). Results: GFR was normal in 44% of the patients, elevated in one third, and decreased in the remaining 28%. Decreased GFR was attributed to fluid loss, hypotension and immunological glomerular disease. Urinary concentrating capacity was abnormal in 68% of the patients with kala-azar after pitressin administration. A urinary pH higher than 5.5 was seen in 64% of cases after ammonium chloride acidification test. There was decreased formation of titratable acidity in 64% and low formation of ammonia urinary excretion in 30% of cases. Complete distal renal tubular acidosis was observed in 30% of patients and an incomplete form was found in 34%. Conclusion: Abnormalities in glomerular filtration, urinary concentration and acidification are consistently associated to the chronic form of kala-azar and can be a consequence of the immunological system dysregulation that occurs in this disease.