ABSTRACT Introduction: The aim of this work is to study the density of the renal papillae in stone-forming patients and to determine its usefulness. Materials and Methods: This study included a total of 79 patients diagnosed with renal stones and on whom a computed tomography without contrast was performed from June 2014 to May 2015. The patients were divided into two groups: Group 1 (single episode) included 43 patients, and Group 2 (recurrent episodes) included 36 patients. The density of six renal papillae (3 per kidney) was measured, and the means obtained were compared between Groups 1 and 2. Statistical analysis was performed using SPSS 20.0. Results: The mean papillary density in Group 1 was 32.26 (SD 4.07) HU compared to 42.36 (SD 8.03) HU in Group 2 (P=00001). A ROC curve was constructed, obtaining an optimal cut-off point of 36.8HU [area under the curve, 0.881 (95% CI; 0.804-0.958); P=0001], with a sensitivity of 80% and a specificity of 90%. The relative risk was estimated at 40.3 (95% CI; 10.8-151.1), meaning that a patient with a mean papillary density greater than 36.8HU would have a 40 times greater risk of having recurrent renal stones. The positive predictive value (PPV) was 81% and the negative predictive value (NPV) was 90%. Conclusion: The measurement of renal papillary density could be useful in predicting recurrent stone-formers. These results need to be confirmed in future studies with a greater number of patients and a longer follow-up.

Litíase renal cálcica é uma doença comum que afeta a população no mundo todo e tem alta taxa de recorrência. Diferentes alterações metabólicas podem desencadear o aparecimento de distúrbios de pedras de cálcio, como hipercalciúria, hiperoxalúria, hiperuricosúria, hipocitratúria e outros. Existem também doenças altamente prevalentes associadas à doença de cálculo de cálcio, como hipertensão, obesidade e perda de densidade óssea mineral. Para realizar prevenção e tratamento adequados, é necessário diagnóstico correto, examinando o metabolismo mineral sérico e urinário. Depois de conhecer o diagnóstico metabólico, é possível estabelecer um tratamento dietético e farmacológico que permita controlar a doença e prevenir a recorrência de cálculos biliares. Há alguns avanços no tratamento dessa doença e incluem o uso de alendronato de sódio em pacientes com nefrolitíase de cálcio e osteopenia/osteoporose, ou a combinação de um tiazídico com um bifosfonato. Em resumo, litíase renal cálcica exige, muitas vezes, um tratamento multidroga com rigorosos controle e acompanhamento de pacientes.

Calcium renal lithiasis is a frequent condition that affects the worldwide population and has a high recurrence rate. Different metabolic changes may trigger the onset of calcium stone disorders, such as hypercalciuria, hyperoxaluria, hyperuricosuria, hypocitraturia and others. There are also other very prevalent disorders that are associated with calcium calculi, such as arterial hypertension, obesity and loss of bone mineral density. A correct diagnosis needs to be obtained through examining the serum and urinary parameters of mineral metabolism in order to carry out adequate prevention and treatment of this condition. Once the metabolic diagnosis is known, it is possible to establish dietary and pharmacological treatment that may enable monitoring of the disease and prevent recurrence of stone formation. Some advances in treating this pathological condition have been made, and these include use of sodium alendronate in patients with calcium renal lithiasis and osteopenia/osteoporosis, or use of a combination of a thiazide with a bisphosphonate. In summary, calcium renal lithiasis often requires multidrug treatment with strict control and follow-up of patients.