Resumo Contexto e objetivo: Cálculos de fosfato de amônio e magnésio (FAM), também conhecidos como cálculos de estruvita, estão associados à infecção urinária e ao comprometimento da unidade renal. O objetivo deste estudo é avaliar os fatores de risco metabólico-urinários para recorrência de cálculos renais em pacientes submetidos à nefrectomia devido a cálculo de FAM. Métodos: Revisamos retrospectivamente os prontuários de pacientes > 18 anos submetidos à nefrectomia total devido a cálculos de FAM puro e cálculos de oxalato de cálcio puro (OxCa) de julho de 2006 a julho de 2016. Os parâmetros metabólicos urinários foram avaliados através de exames de urina de 24 horas ≥ 3 meses após a nefrectomia. Os parâmetros metabólicos urinários e um novo evento relacionado à litíase foram comparados. Resultados: Vinte e oito e 39 pacientes foram incluídos nos grupos FAM e OxCa, respectivamente. As anormalidades em amostras de urina de 24 horas foram similares entre os grupos. A hipercalciúria ocorreu em 7,1 e 10,3% dos pacientes nos grupos FAM e OxCa, respectivamente (p = 0,66), enquanto a hipocitratúria esteve presente em 65,2 e 59,0% dos pacientes nos grupos FAM e OxCa, respectivamente (p = 0,41). Nenhuma diferença significativa em novos eventos foi encontrada entre os grupos FAM e OxCa (17,9 vs. 23,1%, respectivamente; p = 0,60). Conclusão: Uma avaliação de urina de 24 horas deve ser oferecida aos pacientes submetidos à nefrectomia devido a cálculos de FAM puro, a fim de detectar risco metabólico, melhorar o tratamento e prevenir a recorrência de cálculos.

Abstract Background and objective: Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones. Methods: We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared. Results: Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60). Conclusion: A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

ABSTRACT Objectives: Nephrectomy due to stone disease may be a challenging procedure owing to the presence of significant inflammation and infection, involving high complication rate. The objective of our study was to identify predictors for complications of nephrectomy for urolithiasis. Patients and Methods: A retrospective review of 149 consecutive patients > 18y submitted to simple nephrectomy for urolithiasis from January 2006 to July 2012 was performed. Clinical data, computed tomography findings and pathology report were analyzed. Postoperative complications were categorized based on Clavien - Dindo classification. Logistic multivariate regression models assessed the predictors for surgical complications of nephrectomy for urolithiasis. Results: Eighty-three (55.7%) patients were submitted to laparoscopic nephrectomy and 66 (44.2%) to open procedure. Conversion to open surgery was necessary in 19.2% (16 / 83). On univariable analysis, higher preoperative chronic kidney stage (p = 0.02), Charlson comorbidity index ≥ 2 (p = 0.04), higher ASA score (p = 0.001), urgency due to sepsis (p = 0.01), kidney size ≥ 12 cm (p = 0.006), renal and perirenal abscess (p = 0.004 and 0.002 respectively) and visceral adhesion (p = 0.04) were associated with Clavien - Dindo score > 1. On multivariate analysis, higher ASA score (p = 0.01), urgency due to sepsis (p = 0.03), kidney size ≥ 12 cm (p = 0.04) and preoperative abscess (p = 0.04) remained significantly associated with complications. End - stage renal disease with dialysis was needed post - operatively in 3.4% (5 / 144) of patients. Conclusions: We identified that higher ASA score, urgency due to sepsis, kidney size ≥ 12 cm and preoperative abscess were associated with Clavien - Dindo score > 1.

RESUMO Objetivo: investigar os fatores de risco de conversão para cirurgia aberta na nefrectomia laparoscópica (NL) para urolitíase. Métodos: foram revisados os dados de todos os pacientes maiores de 18 anos de idade submetidos à NL entre janeiro de 2006 e maio de 2013 em nossa Instituição. Índice de Charlson, escore ASA, função renal pela equação e estágio de MDRD (Modification of Diet in Renal Disease), achados de tomografia computadorizada (TC) pré-operatória, complicações pela classificação de Clavien-Dindo e taxa de conversão foram analisados. Determinaram-se os fatores de risco para conversão por meio de regressão logística. Resultados: oitenta e quatro pacientes foram submetidos à LN, sendo que 16 (19%) tiveram seu procedimento convertido para cirurgia aberta devido à forte aderência do hilo renal aos órgãos adjacentes. Outras causas associadas à conversão foram sangramento excessivo (n=6) e lesão do intestino grosso (n=3). Na análise univariada, cirurgia renal prévia, borramento da gordura perirrenal, abscesso renal, abscesso perirrenal, abscesso pararrenal, fístula, aderência ao fígado ou baço e aderência ao intestino foram associados à conversão. Na análise multivariada, abscesso pararrenal e aderência ao intestino foram fatores de risco significativos para a conversão. Conclusão: abscesso pararrenal e aderência ao intestino demonstrados na TC pré-operatória são fatores de risco de conversão para cirurgia aberta em LN por urolitíase.

ABSTRACT Objective: to investigate the risk factors for conversion to open surgery in laparoscopic nephrectomy (LN) for urolithiasis. Methods: we reviewed data on all patients over 18 years of age submitted to LN between January 2006 and May 2013 at our institution. We analyzed the Charlson's index, the ASA score, renal function by the equation and stage of MDRD (Modification of Diet in Renal Disease), preoperative computed tomography (CT) findings, complications by the Clavien-Dindo classification and conversion rate. We used logistic regression analysis to determine the risk factors for conversion. Results: eighty-four patients underwent LN, 16 (19%) sustaining convertion to open surgery due to the strong adhesion of the renal hilum to the adjacent organs. Other causes associated with conversion were excessive bleeding (n=6) and lesion of the large intestine (n=3). In the univariate analysis, previous renal surgery, perirenal fat blurring, renal abscess, perirenal abscess, pararenal abscess, fistula, adherence to the liver or spleen, and adherence to the intestine were associated with conversion. In the multivariate analysis, pararenal abscess and adherence to the intestine were significant risk factors for conversion. Conclusion: pararenal abscess and bowel adhesions demonstrated in the preoperative CT are risk factors for conversion to open surgery in LN due to urolithiasis.