Prediction of differential creatinine clearance in chronically obstructed kidneys by non-contrast helical computerized tomography

Quantitative evaluation of chronically obstructed kidneys from noncontrast computed tomography based on deep learning

OBJECTIVE

To quantitatively report renal parenchymal volume (RPV), renal sinus volume (RSV), and renal parenchymal density (RPD) for chronically obstructed kidneys from noncontrast computed tomography (NCCT).

METHODS

This retrospective study was approved by the institutional review board of our hospital with a waiver of informed consent. We retrospectively collected 304 consecutive NCCT scans of urinary obstruction and constructed two datasets: one with 167 patient scans for parenchyma and sinus segmentation (segmentation dataset) and the other containing 137 scans from different patients diagnosed with chronic urinary obstruction (CUO dataset) and paired with split glomerular filtration rate (sGFR). A cascaded three-dimensional (3D) U-Net model was developed and validated for parenchyma and sinus segmentation. The RPV, RSV, and RPD of the CUO dataset were calculated by the model with manual editing. A multivariate analysis was performed to show the association between all parameters and the sGFR.

RESULTS

In the test dataset, the Dice values for parenchyma and sinus segmentation were 0.95 ± 0.04 and 0.90 ± 0.05, respectively. Compared with those of nonobstructed kidneys, the RSV and RPD of obstructed kidneys increased, but RPV and sGFR decreased (P < .001). For chronically obstructed kidneys, age (r = -0.292, P < .001), RPV (r = 0.849, P < .001), RSV (r = -0.331, P < .001), and RPD (r = -0.296, P < .001) were significantly correlated with sGFR. The fitted regression model was sGFR = 10.873-0.111 Age + 0.211 RPV - 0.022 RSV (r² = 0.712).

CONCLUSIONS

NCCT combined with deep learning has the potential to be a single radiological procedure for morphological and functional evaluation of chronically obstructed kidneys.

Role of preoperative MR volumetry in patients with renal cell carcinoma for prediction of postoperative renal function after radical nephrectomy and nephron sparing surgery

Purpose

Preoperative computed tomography or magnetic resonance (MR) imaging are commonly used for radiological evaluation of renal cell carcinoma (RCC) before radical nephrectomy or nephron sparing surgery(NSS). This study aimed to assess the role of MRI for predicting postoperative renal function by preoperative estimation of renal parenchymal volume and correlation with glomerular filtration rate (GFR).

Materials and Methods

A prospective observational study was conducted from February 2015 to October 2016 at a tertiary care hospital in northern India. MR imaging was done on 3 Tesla MR scanner (Signa Hdxt General Electrics, Milwaukee, USA). MR volumetry was used to estimate the renal parenchymal volume. GFR was measured in all patients using Tc99m Diethyl-triamine-penta-acetic acid using Russell’s algorithm. Such measurement was done preoperatively, and postoperatively 3 months after surgery.

Results

30 patients with suspected RCC underwent NSS (n=10) and radical nephrectomy (n=20). Median tumour volume was 175.7cc (range: 4.8 to 631.8cc). The median volume of the residual parenchyma on the affected side was 84.25±41.97cc while that on the unaffected side was 112.25±26.35cc. There was good correlation among the unaffected kidney volume and postoperative GFR for the radical nephrectomy group (r=0.83) as well as unaffected kidney volume, total residual kidney volume and residual volume of affected kidney with postoperative GFR for the NSS group (r=0.71, r=0.73, r=0.79 respectively; P <0.05).

Conclusion

Preoperative residual parenchymal volume on MR renal volumetry correlates well with postoperative GFR in patients with RCC undergoing radical nephrectomy or NSS.

The Urological Association of Asia clinical guideline for urinary stone disease

The Urological Association of Asia, consisting of 25 member associations and one affiliated member since its foundation in 1990, has planned to develop Asian guidelines for all urological fields. The field of stone diseases is the third of its guideline projects. Because of the different climates, and social, economic and ethnic environments, the clinical practice for urinary stone diseases widely varies among the Asian countries. The committee members of the Urological Association of Asia on the clinical guidelines for urinary stone disease carried out a surveillance study to better understand the diversity of the treatment strategy among different regions and subsequent systematic literature review through PubMed and MEDLINE database between 1966 and 2017. Levels of evidence and grades of recommendation for each management were decided according to the relevant strategy. Each clinical question and answer were thoroughly reviewed and discussed by all committee members and their colleagues, with suggestions from expert representatives of the American Urological Association and European Association of Urology. However, we focused on the pragmatic care of patients and our own evidence throughout Asia, which included recent surgical trends, such as miniaturized percutaneous nephrolithotomy and endoscopic combined intrarenal surgery. This guideline covers all fields of stone diseases, from etiology to recurrence prevention. Here, we present a short summary of the first version of the guideline - consisting 43 clinical questions - and overview its key practical issues.

Use of Contrasted Computerized Tomography as a Surrogate for Nuclear Medicine Renogram to Categorize Renal Function in the Setting of Ureteropelvic Junction Obstruction

OBJECTIVE

To use basic measurements on contrasted computerized tomography (CT) to reliably determine whether a kidney with ureteropelvic junction obstruction (UPJO) is definitively functional (≥30% differential renal function [DRF]) or nonfunctional (≤10% DRF), obviating the need for nuclear medicine renogram (RG) to determine DRF.

METHODS

This is a single institution, retrospective cohort of patients diagnosed with UPJO who underwent either pyeloplasty or nephrectomy between December 2004 and December 2014. Included patients had both preoperative mercaptoacetyltriglycine RG and contrasted CT within 180 days of each other. Patients with stents or nephrostomy tubes were excluded.

RESULTS

A total of 49 patients were included. The strongest correlation between differential CT measurements and DRF on RG existed by multiplying the cortical area by the average cortical Hounsfield units (Pearson's r = 0.90, P < .001). Using an equation derived from linear regression and cutoff values generated by receiver operator curve (ROC) analysis, CT equation-estimated DRF values of ≥40% and ≤10% correlated with "definitively functional" RG values of ≥30% (100% specificity) and with "definitively nonfunctional" RG values of ≤10% (100% specificity), respectively. In 30 out of 49 cases, CT could have replaced RG.

CONCLUSION

RG is the gold standard in determining quantitative DRF. However, the treatment algorithm for a kidney with symptomatic UPJO hinges on categorized function: "functional" (repair) or "nonfunctional" (remove). Appropriate measurements on contrasted CT can categorize definitively functional or nonfunctional kidneys with UPJO, negating the need for RG to obtain DRF in a majority of cases. This study design favors real-world application with potential to reduce medical expenditure and delay in definitive treatment.

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.

Correlation between differential renal function estimation using CT-based functional renal parenchymal volume and (99m)Tc - DTPA renal scan

Introduction and Objective:

Nuclear renal scan is currently the gold standard imaging study to determine differential renal function. We propose helical CT as single modality for both the anatomical and functional evaluation of kidney with impaired function. In the present study renal parenchymal volume is measured and percent total renal volume is used as a surrogate marker for differential renal function. The objective of this study is to correlate between differential renal function estimation using CT-based renal parenchymal volume measurement with differential renal function estimation using ^99mTC - DTPA renal scan.

Materials and Methods:

Twenty-one patients with unilateral obstructive uropathy were enrolled in this prospective comparative study. They were subjected to ^99mTc - DTPA renal scan and 64 slice helical CT scan which estimates the renal volume depending on the reconstruction of arterial phase images followed by volume rendering and percent renal volume was calculated. Percent renal volume was correlated with percent renal function, as determined by nuclear renal scan using Pearson coefficient.

Results and Observation:

A strong correlation is observed between percent renal volume and percent renal function in obstructed units (r = 0.828, P < 0.001) as well as in nonobstructed units (r = 0.827, P < 0.001).

Conclusion:

There is a strong correlation between percent renal volume determined by CT scan and percent renal function determined by ^99mTC - DTPA renal scan both in obstructed and in normal units. CT-based percent renal volume can be used as a single radiological tests for both functional and anatomical assessment of impaired renal units.

Renal parenchyma thickness: a rapid estimation of renal function on computed tomography

PURPOSE

To define the relationship between renal parenchyma thickness (RPT) on computed tomography and renal function on nuclear renography in chronically obstructed renal units (ORUs) and to define a minimal thickness ratio associated with adequate function.

MATERIALS AND METHODS

Twenty-eight consecutive patients undergoing both nuclear renography and CT during a six-month period between 2004 and 2006 were included. All patients that had a diagnosis of unilateral obstruction were included for analysis. RPT was measured in the following manner: The parenchyma thickness at three discrete levels of each kidney was measured using calipers on a CT workstation. The mean of these three measurements was defined as RPT. The renal parenchyma thickness ratio of the ORUs and non-obstructed renal unit (NORUs) was calculated and this was compared to the observed function on Mag-3 lasix Renogram.

RESULTS

A total of 28 patients were evaluated. Mean parenchyma thickness was 1.82 cm and 2.25 cm in the ORUs and NORUs, respectively. The mean relative renal function of ORUs was 39%. Linear regression analysis comparing renogram function to RPT ratio revealed a correlation coefficient of 0.48 (p < 0.001). The linear regression equation was computed as Renal Function = 0.48 + 0.80 * RPT ratio. A thickness ratio of 0.68 correlated with 20% renal function.

CONCLUSION

RPT on computed tomography appears to be a powerful predictor of relative renal function in ORUs. Assessment of RPT is a useful and readily available clinical tool for surgical decision making (renal salvage therapy versus nephrectomy) in patients with ORUs.

Is it always necessary to treat a ureteropelvic junction syndrome?

The term ureteropelvic junction (UPJ) obstruction covers different morbid entities, and the old aphorism, "A UPJ is not a UPJ" remains true. Hydronephrosis is readily seen on antenatal ultrasonography but does not necessarily imply obstruction. Although most cases will resolve spontaneously, the probability of a significant pathology is related to the degree of pyelectasis, as seen on the third trimester study. Criteria of obstruction are difficult to define with precision, but two that are well-accepted are size of the renal pelvis (> 15 mm) and relative renal function, as determined by adequate isotopic studies. A new therapeutic standard has been established, and minimally invasive surgery has finally dethroned its open rival. Possibly facilitated by robotic assistance, laparoscopic dismembered pyeloplasty is the present gold standard, albeit endopyelotomy remains the least invasive with similar results in carefully selected patients.