3. S L I D E 2
Background
• Removal of endstage kidneys has been advocated for patients with
large proteinuria, refractory hypertension, recurrent urinary tract
infections (UTI) or urosepsis, urolithiasis, and polyuria
• Heavy proteinuria and hypoalbuminemia are associated with an
increased risk of thrombosis and thromboembolic events
4. S L I D E 3
Background
• Removing the native kidney(s) in nephrotic patients is expected to
reduce the risk of acute graft thrombosis, intravascular volume
depletion, nutritional deficit, and delayed wound healing
• Nephrectomy in children with polyuria help to reduce the risk of
graft injury due to hypoperfusion from extracellular volume
depletion and to alleviate the difficulty of maintaining high post-KT
fluid intake
• There is minimal quantitative data on the effect of residual native
kidney urine output and post-KT graft function in children
5. S L I D E 4
Study Aims
• To examine indications, surgical approach, and
complications of native nephrectomies prior to
transplantation
• To determine the effects of uni- and bilateral
nephrectomy on selected biological and clinical
parameters, specifically urine volume and protein loss
(where applicable) and serum protein concentrations.
6. S L I D E 5
Study design
• Single-center retrospective cohort study at Montreal Children’s
Hospital in Canada
• Identified consecutive patients with uni- or bilateral native
nephrectomies from a total of 126 consecutive graft recipients in
our pediatric KT database
• Between December 1992 and October 2011
8. S L I D E 7
Definitions
• Polyuria:
– Sustained urine output of >2.5 ml/kg/h
• Proteinuria
– >4 mg urine protein/m2 per hour
• Large (nephrotic range) proteinuria
– >40 mg/m2 per hour
• To assess the urine output and proteinuria, timed urine
collection(s) were <2 months pre- and >2 weeks post-
nephrectomy
9. S L I D E 8
Statistical analysis
• Fisher’s exact test was used for categorical variables
• Non-parametric (Wilcoxon matched-pairs signed ranks and Mann–
Whitney U) tests for continuous variables
• Linear regression was used to assess longitudinal changes in urine
output and biochemical results pre- and postnephrectomy
• Assumptions of a normal distribution of residuals, lack of
heteroscedasticity, multicollinearity and non-linearity were
satisfied
• A critical p value of 0.05 was used. The Bonferroni correction was
applied in cases of multiple testing
• Statistical analyses were performed using Stata software
10. S L I D E 9
Results
• The median age at transplantation in the nephrectomized study
cohort was 9.4 years (range 2.0–19.5 years)
18. S L I D E 17
Nephrectomy-related complications
• Peritoneal tears
– Occurred in 5 patients:
• 3/10 patients underwent open retroperitoneal nephrectomy
• 1 associated with a large polycystic kidney & repair of
bilateral hydroceles
• 1/10 patients undergoing bilateral synchronous
retroperitoneal nephrectomy
• Minor complications
– Partial lung atelectasis (3 patients)
– Transient subcutaneous emphysema (2 patients)
– Volume mediated hypertension in five patients with ARPKD (1
patient) and FSGS (4 patients) (managed by intensified dialysis)
19. S L I D E 18
Conclusion
• Unilateral nephrectomy reduced polyuria in all patients, by a
median of 34%, and proteinuria by 40%, while bilateral
(synchronous or staged) nephrectomy improved serum total
protein, albumin and fibrinogen concentrations significantly by 17–
42%
• The main risk of the procedure is peritoneal laceration with
temporary interruption of peritoneal dialysis.
21. S L I D E 20
Surgical procedures
• 12/18 patients (66.6%) underwent left sided unilateral
nephrectomy
• This allowed for removal of the right kidney at the time
of KT, if needed, which is the preferred side for the
future graft
22. S L I D E 21
Recurrent UTI
• 9 patients had nephrectomy for recurrent UTI (3 unilateral and 6
bilateral nephrectomies)
• 3 were nephrectomized at or after KT
• 1 had insufficient postoperative information
• 4 had no more UTIs between nephrectomy and KT
• 1 had a single UTI
• Post-KT
• 3/9 patients remained free of UTIs during 2 years of observation
• 6/9 had at least one recurrence of UTI (median 3.0 UTIs per
person-year). All patients had UTI risks (e.g. VACTERL sequence,
posterior urethral valve bladder, cystoplasty, & CIC)
23. S L I D E 22
Nephrectomy Decision
• Physiological aspects
– Volume status and the perfusion of the (adult) graft in the
pediatric recipient
• Clinical arguments
– Severe arterial hypertension
• Psychosocial factors
– Predicted inability to comply with increased post-transplant
fluid intake
24. S L I D E 23
Gradual decrease of urine output following unilateral nephrectomy (in months; median 36%, range −10 to −70%).
Depicted are all patients for whom data on serial, post-nephrectomy urine collections were available. 0 Time of
nephrectomy.
Heteroscedasticity (also spelled heteroskedasticity) refers to the circumstance in which the variability of a variable is unequal across the range of values of a second variable that predicts it. It means data with unequal variability (scatter) across a set of second, predictor variables.
Multicollinearity (also collinearity) is a phenomenon in which one predictor variable in a multiple regression model can be linearly predicted from the others with a substantial degree of accuracy.
When conducting multiple analyses on the same dependent variable, the chance of committing a Type I error increases, thus increasing the likelihood of coming about a significant result by pure chance. To correct for this, or protect from Type I error, a Bonferroni correction is conducted.
Bonferroni correction is a conservative test that, although protects from Type I Error, is vulnerable to Type II errors (failing to reject the null hypothesis when you should in fact reject the null hypothesis)
