Prediction of renal recovery in hydronephrotic kidneys

Development and validation of a novel prediction model for predicting renal function recovery after diversion in patients with obstructive uropathy

OBJECTIVE

To develop and validate a novel prediction model predicting renal function recovery following diversion in patients with obstructive uropathy (OU) to the emergency department (ED).

METHODS

After a systematic literature search, a novel prediction model called PGIMER Obstructive Uropathy Score (POUS) was constructed including five variables: age (<60 or >60 years), duration of symptoms (<4 or >4 weeks), presence of solitary functioning kidney, baseline hemoglobin levels and venous blood pH. This model was then validated in a prospective, observational single-center study of patients presenting with OU caused by various etiologies. Patients with OU and raised serum creatinine (>2 mg/dL) presenting to our ED were included. Renal function recovery was defined as creatinine value <1.5 mg/dL at 4 weeks following diversion.

RESULTS

In this study, 174 consecutive patients with OU were recruited, and 74 (42.5%) patients had renal function recovery. All the variables included in the POUS were noted to be statistically significant on univariate analysis. On multivariate logistic regression analysis, only POUS was identified as an independent predictor of renal function recovery. On receiver operating curve analysis, the area under the curve for POUS was 0.832 for predicting recovery. A POUS of 5 or more had specificity and sensitivity of 83% and 73.6%, respectively, in predicting renal function recovery. The goodness of fit and calibration plots showed good concordance of the predicted values with the observed values.

CONCLUSIONS

The POUS model is an accurate and simple-to-use tool for predicting renal function recovery. POUS model requires external validation prior to clinical use in different populations.

Factors influencing recoverability of renal function after urinary diversion through percutaneous nephrostomy

CONTEXT

Various factors predict recoverability of kidney function preoperatively. Placement of percutaneous nephrostomy (PCN) and measuring the differential creatinine clearance (diff. %CrCl) is still regarded as a simple and reliable method.

AIMS

The aim was to evaluate correlation between renal cortical thickness (CT), hydronephrosis, intrapelvic pressure (IPP), PCN output, renal morphological factors such as length, width, echogenicity, corticomedullary differentiation (CMD), status of c/l kidney, and presence of infection which can predict recoverable function.

SETTINGS AND DESIGN

A prospective study done between July 2013 and June 2014 in Urology Department.

SUBJECTS AND METHODS

Hundred and sixty patients of supravesical obstruction for various causes who need PCN either due to chronic renal failure or nonvisualized kidney on contrast study, were included. IPP was measured during PCN placement. After 4 weeks 24 h urine was sent for CrCl and urine pH.

STATISTICAL ANALYSIS USED

Correlation of continuous and categorical variables with dependent variable (diff. %CrCl) was formulated using spearman correlation and Mann-Whitney U test. Simple and multiple linear regression analysis were performed.

RESULTS

The study includes 160 patients with median age of 65.5 years. Hydronephrosis were due to stone in 76 (47.5%), pelviureteric junction obstruction (PUJO) in 40 (25%), cancer in 32 (20%), others in 12 cases (7.5%). IPP was <10 cm H2O in 48 (30%); 10-20 cm H2O in 64 (40%) and >20 cm H2O in 48 (30%). There was significant correlation between IPP and diff. %CrCl with correlation coefficient ρ = 0.509 (P = 0.0001).

CONCLUSIONS

CT, parenchymal echogenicity, CMD, pre-PCN creatinine, and status of c/l kidney are the only independent variables which can predict the renal function while other variables like renal size, urine output, infection, hydronephrosis lost their statistical significance in multivariate analysis. Furthermore, IPP measured before PCN directly correlated with daily urine output and diff. %CrCl.

Factors influencing the non-recovery of renal function after the relief of urinary tract obstruction in women with cancer of cervix

OBJECTIVES

To identify factors associated with non-recovery of renal function after the relief of urinary tract obstruction in women with cancer of cervix.

PATIENTS AND METHODS

Thirty-seven women with cancer of cervix and obstructive renal failure were prospectively studied. Patients were evaluated in the day before nephrostomy (D0); and in the 1st (D1), 7th (D7), and 30th day (D30) after unilateral nephrostomy. The following parameters were analyzed: age serum urea, and serum creatinine (S(creat)), in D0, D7, and D30. Renal cortical thickness was measured by ultrasonography in D0. During nephrostomy procedure, urine samples for urinalysis and culture were collected and renal biopsy was attempted. Patients were divided in two groups according to S(creat) in D30: patients with S(creat) < 1, 4mg/dL (R group) and those with S(creat) > or = 1, 4mg/dL (nR group).

RESULTS

Ten patients died before D30 and were not studied. R group (n = 12) was younger (43 +/- 9 vs. 52 +/- 10 years, p < 0.05) than nR group (n = 15), and presented lower serum urea in D0 (134 +/- 67 vs. 212 +/- 51 mg/dL, p < 0.01) and in D7 (94 +/- 20 vs. 155 +/- 18 mg/dL, p < 0.05). Renal cortex was thicker in R group (17 +/- 1 vs. 13 +/- 1 mm, p < 0.05). Survival was higher in R group (11/12) than in nR group (0/15, p < 0.01). All urine samples showed leukocyturia but culture was positive in only two. In three out of nine biopsy attempts enough material was obtained. Light microscopy revealed interstitial fibrosis plus tubular atrophy, and partial glomerular fibrosis was present in two biopsies.

CONCLUSIONS

The non-recovery of renal function after the relief of obstruction in human obstructive renal failure is associated with older age and decreased renal cortical thickness. The complete renal recovery improves patient survival despite malignancy.

Prognosis of radiologically non-functioning obstructed kidneys

Twenty patients found to have unilateral radiologically non-functioning obstructed kidneys on excretory urography (IVU), and who had normal contralateral kidneys, were further evaluated. Ultrasonography, radionuclide imaging and CT scan were carried out pre-operatively to try to predict which of the kidneys were potentially recoverable after relief of obstruction. Percutaneous nephrostomy was also performed on the last consecutive 7 patients 4 weeks before definitive treatment and the function of the kidneys determined daily. The patients were re-evaluated 2 months after the relief of obstruction. Ultrasonography, radionuclide imaging and CT scan were not found to be reliable in predicting whether these kidneys were potentially recoverable. We consider percutaneous nephrostomy a good procedure for obtaining prognostic information prior to definitive surgery.

Recovery of radiologically functionless obstructed kidneys

Eleven patients had radiologically non-functioning and unilaterally obstructed kidneys with normal kidneys on the other side. The kidneys were divided into three groups according to the urinary pH of the obstructed kidney at operation: Group 1 (pH 6.0 or less); Group 2 (pH 6.1-7.1); Group 3 (pH greater than 7.1). The obstruction was corrected in all patients despite the pre-operative radiological findings or the morphological appearance at operation. Radiological recovery was assessed 2 months post-operatively and was found to be good in all patients in Group 1. In Group 2, recovery was good in one patient, moderate in two and absent in one. In Group 3 there was no evidence of radiological recovery in either patient.

Changes in urinary pH and glomerular filtration rate in partially obstructed canine kidney

The creatinine clearance and urinary pH changes were studied in 12 male dogs in whom the ureters were unilaterally obstructed for periods ranging from 2 days to 27 weeks. The obstruction was then released and the recovery was studied. Using the contralateral kidney as control, significant drop in the creatinine clearance was observed to be consistently associated with failure to produce acidic urine. The obstructed kidneys with urinary pH above 7.00 had significant reduction in creatinine clearance when compared with obstructed kidneys with urinary pH 7.00 or less (p less than 0.005). The marked drop in the creatinine clearance and rise in urinary pH was observed to occur in kidneys obstructed for more than 3 weeks. With obstruction for shorter periods, the ability to produce acidic urine is preserved and the recovery potential is good.