Clinical features of patients with solitary kidneys

Solitary kidney and risk of chronic kidney disease

The renal outcome of solitary kidney remains controversial. We examined the longitudinal association of congenital or acquired solitary kidney with the development of chronic kidney disease (CKD). A cohort study was performed involving 271,171 Korean men and women free of CKD at baseline who underwent a health screening program and who were followed annually or biennially for an average of 5.4 years. Solitary kidney was determined based on ultrasonographic findings. CKD was defined as an estimated glomerular filtration rate of < 60 ml/min/1.73 m² and/or the presence of proteinuria in two or more consecutive visits. During 1,472,519.6 person-years of follow-up, 2989 participants developed CKD (incidence rate: 2.0 per 1000 person-years). After adjustment for potential confounders, the aHR (95% CIs) for incident CKD comparing solitary kidney to the control was 3.26 (1.63-6.54). In analyses of cause-specific solitary kidney, aHR (95% CIs) for CKD comparing unilateral nephrectomy and congenital solitary kidney to the control were 6.18 (2.31-16.49) and 2.22 (0.83-5.92), respectively. The association between solitary kidney and CKD was stronger in men. Having a solitary kidney was independently associated with an increased risk of CKD development. Therefore, preventive strategies for reducing the risk of CKD are required in individuals with a solitary kidney.

Renal Damage Frequency in Patients with Solitary Kidney and Factors That Affect Progression

Background. The aim of this study is to assess renal damage incidence in patients with solitary kidney and to detect factors associated with progression. Methods. Medical records of 75 patients with solitary kidney were investigated retrospectively and divided into two groups: unilateral nephrectomy (group 1) and unilateral renal agenesis/dysplasia (group 2). According to the presence of kidney damage, each group was divided into two subgroups: group 1a/b and group 2a/b. Results. Patients in group 1 were older than those in group 2 (p = 0.001). 34 patients who comprise group 1a had smaller kidney size (p = 0.002) and higher uric acid levels (p = 0.028) than those in group 1b at presentation. Uric acid levels at first and last visit were associated with renal damage progression (p = 0.004, 0.019). 18 patients who comprise group 2a were compared with those in group 2b in terms of presence of DM (p = 0.038), HT (p = 0.003), baseline proteinuria (p = 0.014), and uric acid (p = 0.032) levels and group 2a showed higher rates for each. Progression was more common in patients with DM (p = 0.039), HT (p = 0.003), higher initial and final visit proteinuria (p = 0.014, for both), and higher baseline uric acid levels (p = 0.047). Conclusions. The majority of patients with solitary kidney showed renal damage at presentation. Increased uric acid level is a risk factor for renal damage and progression. For early diagnosis of renal damage and reducing the risk of progression, patients should be referred to a nephrologist as early as possible.

Association of Retinoid X Receptor Alpha Gene Polymorphism with Clinical Course of Chronic Glomerulonephritis

Background

Vitamin D (VD), VD binding protein, VD receptor (VDR), and retinoids are involved in pathogenesis of chronic glomerulonephritis (ChGN). We aimed to compare distribution of VD pathway gene polymorphisms in ChGN patients showing glomerular filtration rate (GFR) category 1–3, GFR category 5D, and healthy controls in order to elucidate the role of VD-related polymorphisms in the course of ChGN.

Material/Methods

GFR category 1–3 ChGN patients (n=195), GFR category 5D ChGN patients (n=178), and controls (n=751) underwent testing for polymorphisms of genes encoding VD binding protein (GC, rs2298849, rs7041, rs1155563), VDR (VDR, rs2228570, rs1544410), and retinoid X receptor alpha (RXRA, rs10776909, rs10881578, rs749759).

Results

Among GFR 1–3 subjects possessing TT genotype of RXRA rs10776909, 75% of patients had nephrotic syndrome, and 37.5% had glomerular hyperfiltration defined as GFR >140 ml/min/1.73 m², and, consequently, serum creatinine was lower in these patients compared to the remaining subjects (0.67±0.26 vs. 0.94±0.34, P=0.014). In GFR category 5D ChGN patients, frequencies of RXRA rs10776909 allele T (25% vs. 19%) and CT+TT (46% vs. 34%) were higher compared to frequencies of respective variants in controls (P_trend=0.004, P_genotype=0.008).

Conclusions

RXRA rs10776909 allele T is specifically involved in the pathogenesis of ChGN. This risk allele may be also associated with worse clinical course of ChGN.

Renal functional outcomes after surgery for renal cortical tumors

Historically, radical nephrectomy represented the gold standard for the treatment of small (≤ 4cm) as well as larger renal masses. Recently, for small renal masses, the risk of ensuing chronic kidney disease and end stage renal disease has largely favored nephron-sparing surgical techniques, mainly partial nephrectomy. In this review, we surveyed the literature on renal functional outcomes after partial nephrectomy for renal tumors. The largest randomized control trial comparing radical and partial nephrectomy failed to show a survival benefit for partial nephrectomy. With regards to overall survival, surgically induced chronic kidney disease (GFR < 60 ml/min/ 1.73m²) caused by nephrectomy might not be as deleterious as medically induced chronic kidney disease. In evaluating patients who underwent donor nephrectomy, transplant literature further validates that surgically induced reductions in GFR may not affect patient survival, unlike medically induced GFR declines. Yet, because patients who present with a renal mass tend to be elderly with multiple comorbidities, many develop a mixed picture of medically, and surgically-induced renal disease after extirpative renal surgery. In this population, we believe that nephron sparing surgery optimizes oncological control while protecting renal function.

Microalbuminuria and hyperfiltration in subjects with nephro-urological disorders

BACKGROUND

Microalbuminuria (MA) has been shown to be an early biomarker of renal damage. It is postulated that MA is the early result of hyperfiltration, which could evolve into glomerular sclerosis and renal failure if hyperfiltration is left untreated. We hypothesized that MA is a good indicator of hyperfiltration in children with kidney disorders, obviating the need to calculate the filtration fraction (FF).

METHODS

A total of 155 children or young adults were prospectively included [42 single kidney (SK), 61 vesico-ureteral reflux, 23 obstructive uropathies, 29 other kidney diseases]. We measured inulin, para-aminohippuric acid clearances, FF and MA. Prediction of hyperfiltration was explored by studying the association between the FF and other variables such as urinary albumin (Alb), urinary albumin-creatinine ratio (ACR) and creatinine clearance.

RESULTS

A significant but weak association between urinary Alb or ACR and FF was found in subjects with an SK (Spearman correlation coefficients 0.32 and 0.19, respectively). Multivariate analysis also showed that urinary Alb and ACR significantly predict FF only in subjects with an SK (r(2) = 0.17, P = 0.01 and r(2) = 0.13, P = 0.02, respectively). This holds true only in subjects with an SK and inulin clearance >90 mL/min/1.73 m(2) (r(2) = 0.41, P < 0.001). There was no association between creatinine clearance and FF.

CONCLUSIONS

MA is not associated with FF in our subjects with nephro-urological disorders, except in those with an SK, where the association is weak, indicating that MA is due to other mechanisms than high FF and cannot predict hyperfiltration in such groups.

Adverse consequences of accelerated neonatal growth: cardiovascular and renal issues

Epidemiological and experimental studies show that the risk of cardiovascular and metabolic diseases at adulthood is inversely related to the weight at birth. Although with less evidence, low birth weight has been suggested to increase the risk of chronic kidney disease (CKD). It is well established that the developmental programming of arterial hypertension and of renal disease involves in particular renal factors, especially nephron endowment, which is reduced in low birth weight and maternal diabetes situations. Experimental studies, especially in rodents, have demonstrated the long-term influence of postnatal nutrition and/or postnatal growth on cardiovascular, metabolic and renal functions, while human data are scarce on this issue. Vascular and renal diseases appear to have a "multihits" origin, with reduced nephron number the initial hit and rapid postnatal growth the second hit. This review addresses the current understanding of the role of the kidney, both as a mechanism and as a target, in the developmental origins of adult disease theory, with a particular focus on the long-term effects of postnatal growth and nutrition.

Congenital versus acquired solitary kidney: is the difference relevant?

BACKGROUND

Serious concerns have risen during the last decades regarding the potential role of solitary kidney (SK) in promoting systemic hypertension, proteinuria and glomerulosclerosis. The aim of the study was to assess mid- and long-term outcome of children with SK, with special highlight on the differential functional outcome of congenital and acquired forms of SK.

METHODS

Ninety-seven patients (43 females) aged from 2.9 to 25 years with radiologically normal SK were divided into two groups depending on whether they had a congenital (CSK, n = 44) or an acquired SK (ASK, n = 53). Mean follow-up time with SK was 8.3 ± 3.2 and 9.1 ± 4.4 years, respectively (P = NS). Blood pressure (BP), glomerular filtration rate (GFR) measured by inulin clearance, and microalbuminuria were assessed in all patients.

RESULTS

Two children (2%), one in each group, had systemic hypertension confirmed by 24-h ambulatory BP monitoring, and 17 (17.5%) had a significant microalbuminuria (8 in CSK and 9 in ASK, P = NS). The overall mean GFR was 100.6 ± 15 mL/min/1.73 m(2) and was found to be inversely correlated with age and follow-up time. Seven children had a GFR <80 mL/min/1.73 m(2), all had been nephrectomized in early childhood. Interestingly, GFR was higher in CSK than in ASK group (107.2 vs. 95.2 mL/min/1.73 m(2), P < 0.01) and was negatively related to follow-up time only in the latter but not in the former group.

CONCLUSIONS

In the light of these results, it appears that renal function in children with SK is well preserved in short and medium term, but it seems to decline gradually with longer periods of follow-up, particularly in ASK, thus assuming a better functional adaptation in CSK. Both conditions remain yet risky and predispose children to a greater incidence of hypertension and renal impairment in later life. Thereby, careful screening should be proposed throughout childhood to detect early signs of glomerular hyperfiltration and prevent its progression to more serious complications.

Urinary transforming growth factor beta1 in children and adolescents with congenital solitary kidney

The aim of the study was to assess urinary transforming growth factor beta1 (TGF beta1) level in children and adolescents with congenital solitary kidney (CSK), depending on estimated glomerular filtration rate (eGFR) and compensatory overgrowth of the kidney. The study group (I) consisted of 65 children and young adults, 0.5-22 years of age (median 10.0 years) with CSK and no other urinary defects. The control group (C) contained 44 healthy children and adolescents, 0.25-21 years old (median 10.3 years). We used an enzyme-linked immunosorbent assay (ELISA) to determine the urinary level of TGF beta1, the Jaffe method to assess creatinine concentration, and the Schwartz formula to estimate GFR. Kidney length was measured while the patient was in a supine position, and overgrowth (O%) was calculated with reference to the charts. Urinary TGF beta1 level in CSK patients was more than twice as high as that in controls (P < 0.05). Also, eGFR in patients with CSK exceeded the values in the control group (P < 0.01). Compensatory overgrowth of the solitary kidney was found (median 19.44%). Urinary TGF beta1 concentration was positively correlated with eGFR (r = 0.247, P < 0.05), uric acid concentration (r = 0.333, P < 0.01), and percentage of overgrowth (r = 0.338, P < 0.01) and body mass index (BMI) centile (r = 0.274, P < 0.05). We concluded that, although proteinuria and progressive renal insufficiency is not observed in patients with CSK during childhood, the renal haemodynamic changes are present and may be a risk factor for impairment of renal function and hypertension in future life.

Ambulatory blood pressure monitoring and renal functions in children with a solitary kidney

The aim of this study is to investigate the blood pressure (BP) profile, microalbuminuria, renal functions, and relations with remaining normal kidney size in children with unilateral functioning solitary kidney (UFSK). Sixty-six children with UFSK were equally divided into three groups: unilateral renal agenesis (URA), unilateral atrophic kidney (UAK), and unilateral nephrectomy (UNP). Twenty-two age-, weight-, and height-matched healthy children were considered as a control group. The serum creatinine level and first-morning urine microalbumin and creatinine concentrations were determined by the standard methods. Also, the BP profile was determined by ambulatory blood pressure monitoring (ABPM). We found that the serum creatinine level was higher and creatinine clearance was lower in each patient groups compared to those of the control group (p < 0.05). Compared with the controls, each group of patients had mean office, 24-h, daytime, and night-time systolic and diastolic BP values similar to those of the controls (p > 0.05). An inverse correlation was found between the renal size standard deviation scores (SDS) of normal kidneys and 24-h systolic and diastolic BP load SDS in all of the patients (p < 0.05; r = -0.372, r = -0.295, respectively). The observed relationship between renal size SDS and 24-h mean arterial pressure (MAP), systolic and diastolic BP load SDS suggests that children with UFSK should be evaluated by using ABPM for the risk of hypertension.

Consequences of Intrauterine Growth Restriction for the Kidney

Low birth weight due to intrauterine growth restriction is associated with various diseases in adulthood, such as hypertension, cardiovascular disease, insulin resistance and end-stage renal disease. The purpose of this review is to describe the effects of intrauterine growth restriction on the kidney. Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction, leading to a low nephron endowment. The compensatory hyperfiltration in the remaining nephrons results in glomerular and systemic hypertension. Hyperfiltration is attributed to several factors, including the renin-angiotensin system (RAS), insulin-like growth factor (IGF-I) and nitric oxide. Data from human and animal studies are presented, and suggest a faltering IGF-I and an inhibited RAS in intrauterine growth restriction. Hyperfiltration makes the kidney more vulnerable during additional kidney disease, and is associated with glomerular damage and kidney failure in the long run. Animal studies have provided a possible therapy with blockage of the RAS at an early stage in order to prevent the compensatory glomerular hyperfiltration, but this is far from being applicable to humans. Research is needed to further unravel the effect of intrauterine growth restriction on the kidney.

Adult hypertension and kidney disease: the role of fetal programming

Hypertension (HTN) and chronic kidney disease are highly prevalent diseases that tend to occur more frequently among disadvantaged populations, in whom prenatal care also tends to be poor. More and more evidence is emerging highlighting the important role of fetal programming in the development of adult disease, suggesting a possible common pathophysiologic denominator in the development of these disorders. Epidemiologic evidence accumulated over the past 2 decades has demonstrated an association between low birth weight and subsequent adult HTN, diabetes, and cardiovascular disease. More recently, a similar association has been found with chronic kidney disease. Animal studies and indirect evidence from human studies support the hypothesis that low birth weight, as a marker of adverse intrauterine circumstances, is associated with a congenital deficit in nephron number. The precise mechanism of the reduction in nephron number has not been established, but several hypotheses have been put forward, including changes in DNA methylation, increased apoptosis in the developing kidney, alterations in renal renin-angiotensin system activity, and increased fetal glucocorticoid exposure. A reduction in nephron number is associated with compensatory glomerular hypertrophy and an increased susceptibility to renal disease progression. HTN in low birth weight individuals also appears to be mediated in part through a reduction in nephron number. Increased awareness of the implications of low birth weight and inadequate prenatal care should lead to public health policies that may have long-term benefits in curbing the epidemics of HTN, diabetes, and kidney disease in generations to come.

Low birth weight, nephron number, and kidney disease

More and more evidence is emerging that highlights the far-reaching consequences of prenatal (intrauterine) programming on organ function and adult disease. In humans, low birth weight (LBW) occurs more frequently in disadvantaged communities among whom there is often a disproportionately high incidence of adult cardiovascular disease, hypertension, diabetes mellitus, and kidney disease. Indeed, many epidemiologic studies have found an inverse association between LBW and higher blood pressures in infancy and childhood, and overt hypertension in adulthood. Multiple animal models have demonstrated the association of LBW with later hypertension, mediated, at least in part, by an associated congenital nephron deficit. Although no direct correlation has been shown between nephron number and birth weight in humans with hypertension, nephron numbers were found to be lower in adults with essential hypertension, and glomeruli tend to be larger in humans of lower birth weight. An increase in glomerular size is consistent with hyperfiltration necessitated by a reduction in total filtration surface area, which suggests a congenital nephron deficit. Hyperfiltration manifests clinically as microalbuminuria and accelerated loss of renal function, the prevalence of which are higher among adults who had been of LBW. A kidney with a reduced nephron number has less renal reserve to adapt to dietary excesses or to compensate for renal injury, as is highlighted in the setting of renal transplantation, where smaller kidney to recipient body-weight ratios are associated with poorer outcomes, independent of immunologic factors. Both hypertension and diabetes are leading causes of end-stage renal disease worldwide, and their incidences are increasing, especially in underdeveloped communities. Perinatal programming of these 2 diseases, as well as of nephron number, may therefore have a synergistic impact on the development of hypertension and kidney disease in later life. Existing evidence suggests that birth weight should be used as a surrogate marker for future risk of adult disease. Although the ideal solution to minimize morbidity would be to eradicate LBW, until this panacea is realized, it is imperative to raise awareness of its prognostic implications and to focus special attention toward early modification of risk factors for cardiovascular and renal disease in individuals of LBW.

The relationship between microalbuminuria and glomerular filtration rate in young type 1 diabetic subjects: The Oxford Regional Prospective Study

BACKGROUND

The purpose of this study was to examine the relationship between glomerular filtration rate (GFR) measured at 5 years' diabetes duration and annual urine albumin excretion in a prospective cohort of children with type 1 diabetes (T1DM).

METHODS

Three hundred and eight children were followed from diagnosis of T1DM [aged 9.8 years (range 0.4-15.9) for a median duration of 10.9 years (6.0-17.8) with annual assessments comprising measurement of HbA1(c) and 3 urine samples for albumin:creatinine ratio (ACR). GFR was measured in all children at 5 years' diabetes duration.

RESULTS

Two hundred forty-three (78.8%) subjects were normoalbuminuric (MA-) for the duration of the study. At 5 years: 35 (11.4%) subjects had MA (MA+) and 30 (9.7%) subjects were normoalbuminuric but developed MA during subsequent follow-up annual assessments (future MA+). In the future MA+ group compared to the MA+ and MA- groups; GFR was higher (167 vs. 134 vs. 139 mL/min/1.73 m(2), P < 0.002); the prevalence of hyperfiltration (GFR >125 mL/min/1.73 m(2)) was greater (97 vs. 57 vs. 64%, P= 0.006) and HbA1c levels were higher (11.4 vs. 10.8 vs. 9.7%, P < 0.001). The probability (Cox Model) of having hyperfiltration at 5 years' duration was related to puberty (a 1.7-fold increased risk with puberty onset) and poor glycemic control (a 10% increased risk for a 1% increase in HbA1c). Comparing subjects with and without hyperfiltration, prior to the first GFR measurement no difference in ACR levels existed; however, after this time median ACR levels were significantly greater [1.2 (0.1-86.4) vs. 0.9 (0.1-71.6) mg/mmol, P= 0.003], independent of age and HbA1c levels. The probability of developing MA between 5 and 10 years' duration was associated with poor glycemic control (a 30% increased risk for a 1% increase in HbA1c) and higher GFR at 5 years (22% increased risk for a 10 mL/min/1.73 m(2) rise in GFR).

CONCLUSION

Glomerular hyperfiltration is associated with puberty and increasing ACR levels and is predictive of MA independent of HbA1c. This suggests that factors other than poor glycemic control may be involved in the pathogenesis of early diabetic nephropathy and early intervention with medical therapy to reduce GFR may be beneficial even before onset of MA.

Nephron endowment and blood pressure: what do we really know?

It has been hypothesized that a reduced number of nephrons at birth contributes to the development of essential hypertension. Nephron number in normal human kidneys has been shown to vary up to eightfold. Therefore, a significant proportion of the population appears to be at risk for developing hypertension. Furthermore, nephron deficits might explain why some racial groups have a higher incidence of hypertension and end-stage renal disease than others. Animal studies have demonstrated that maternal limitations in nutrient supply, both gross and nutrient-specific; exposure to elevated levels of hormones or toxins; and genetic factors can lead to permanent deficits in nephron number and, when examined, elevated blood pressure. In this review, maternal and genetic factors influencing nephron endowment and the implications of nephron deficit for hypertension and renal disease in humans are discussed.

Gestational hypertension and preeclampsia associated with unilateral renal agenesis in women with uterine malformations

OBJECTIVE

To evaluate the possible connection between gestational hypertensive disorder and unilateral renal agenesis in women with congenital uterine anomalies.

STUDY DESIGN

Thirty-three (16%) out of 206 women with uterine anomalies had unilateral renal agenesis. Nineteen of them had delivered and comprised the study group. The control group consisted of 44 women among the 206 with similar uterine malformations who had normal bilateral kidneys and matched in age and parity with the study group. Retrospective analysis considered the presence of gestational hypertension, proteinuria, preeclampsia, perinatal outcomes and manifestations of hypertension and renal disease during the follow-up period in both groups. The median follow-up was 166 months (range 24-372 months).

RESULTS

Women with unicornuate uterus most frequently (25%) evinced unilateral renal agenesis. Eight (42%) out of 19 women with malformed uterus and unilateral renal agenesis had in at least one pregnancy gestational hypertension, preeclampsia or gestational proteinuria compared to 8 (18%) out of 44 women with two kidneys (relative risk, RR 2.33, 95% CI 1.02, 5.29). Seventeen (35%) out of all 49 pregnancies in the study group were complicated by gestational hypertensive disorder or proteinuria as against 10 (11%) out of 90 pregnancies in the control group (RR 3.12, 95% CI 1.55, 6.28). Perinatal outcomes were similar in both groups. During follow-up none had diagnosed proteinuria or chronic renal disease, but two out of 19 women (11%) with unilateral renal agenesis had commenced medication for chronic hypertension.

CONCLUSION

Unilateral renal agenesis predisposes women with uterine anomalies to preeclampsia.

Predisposition to nephropathy in Polynesians is associated with family history of renal disease, not diabetes mellitus

AIMS

Familial clustering of diabetes and nephropathy suggests that either common environmental or inherited mechanisms are important in developing diabetic nephropathy. If an inherited mechanism is important, the albumin excretion rate might be increased in those at future risk. This study aimed to determine whether people with a family history of diabetes or people with a family history of renal disease were most at risk.

METHODS

In a two-by-two factorial study of urinary albumin in non-diabetic Polynesians, 90 people with a first degree relative (FDR) with end-stage renal failure (ESRF) and diabetes (group 1) were compared with 90 people with a FDR with non-diabetic ESRF (group 2), with 90 people with a FDR with diabetes but no known nephropathy (group 3) and 90 people with no known relatives with either diabetes or nephropathy (group 4). Groups were matched for ethnicity and age.

RESULTS

Subjects with a family history of ESRF (groups 1 and 2) had an increased mean albumin-creatinine ratio (1.25 vs. 1.00 mg/mmol, P = 0.01), but in subjects with a family history of diabetes (groups 1 and 3), the mean ratios were not significantly different from those without a family history of diabetes (1.06 vs. 1.17 mg/mmol; P = 0.2). In those with a family history of nephropathy, fasting blood glucose and systolic blood pressure were increased, while fasting insulin and 2 h insulin concentrations were lower. A family history of diabetes was associated with an increased fasting blood glucose and 2-h blood glucose. By multiple linear regression, the mean systolic blood pressure (P = 0.02), the 2-h glucose concentration (P = 0.05), a family history of renal failure (P = 0.04), female sex (P = 0.0001) and the total cholesterol (P = 0.01) were each independently associated with microalbuminuria, while a family history of diabetes was not (P = 0.09).

CONCLUSIONS

These data suggest that among Polynesians there is no specific inherited tendency to diabetic nephropathy per se. The risk of nephropathy does not appear to be associated with the degree of familial risk of diabetes itself. Rather, the risk of diabetic nephropathy may be the result of a familial risk of nephropathy from any cause and is associated with diabetes through relative hypoinsulinaemia and hyperglycaemia.

Hypertension in renal failure

Hypertension is a common component of the morbidity associated with renal failure. The mechanisms that contribute to high blood pressure are reviewed in this section. Also covered are therapies to reduce hypertension, the treatment goals of those therapies, and the outcomes of antihypertensive therapy on kidney function in patients with renal failure. Various antihypertensive agents are specifically addressed, and a treatment paradigm is presented for combination antihypertensive drug therapy, which is usually necessary in the antihypertensive therapy of patients with renal failure.

The hyperfiltration theory: a paradigm shift in nephrology

Experimental studies incriminate glomerular hypertension in mediating progressive renal damage after any of a variety of initiating injuries. Prevention of glomerular hypertension by dietary protein restriction or antihypertensive therapy lessens progressive glomerular damage in several experimental models of chronic renal disease. Glomerular hypertension and hyperfiltration also occur in humans with diabetes mellitus, solitary or remnant kidneys, and various forms of acquired renal disease. Clinical studies indicate that dietary protein restriction and antihypertensive therapy also slow progression in many of these disorders. Large multicenter trials confirm the beneficial effects of these therapeutic maneuvers on the rate of progression of chronic renal disease.

Long-term effects of reduced renal mass in humans

The long-term risks of kidney donation have not been well defined. We carried out meta-analysis of investigations that examined the long-term effects of reduced renal mass in humans. We used multiple linear regression to combine studies and adjust for differences in the duration of follow-up, the reason for reduced renal mass, the type of controls, age and gender. We analyzed 48 studies with 3124 patients and 1703 controls. Unilateral nephrectomy caused a decrement in glomerular filtration rate (-17.1 ml/min; 95% confidence interval -20.2 to -14.0 ml/min) that tended to improve with each 10 years of follow-up (1.4 ml/min/decade; 0.3 to 2.4 ml/min/decade). Patients with single kidneys had small, progressive increases in proteinuria (76 mg/day/decade; 52 to 101 mg/day/decade), but proteinuria was negligible after nephrectomy for trauma or kidney donation. Nephrectomy did not affect the prevalence of hypertension, but there was a small increase in systolic blood pressure (2.4 mm Hg; -0.3 to 5.1 mm Hg, P > 0.05) which rose further with duration of follow-up (1.1 mm Hg/decade; 0.0 to 2.2 mm Hg/decade). Diastolic blood pressure was higher after nephrectomy (3.1 mm Hg; 1.8 to 4.4 mm Hg), but this increment did not change with duration of follow-up. Thus, in normal individuals, unilateral nephrectomy does not cause progressive renal dysfunction, but may be associated with a small increase in blood pressure.

Fewer nephrons at birth: a missing link in the etiology of essential hypertension?

In 1988, Brenner et al advanced the hypothesis that the nephron endowment at birth is inversely related to the risk of developing essential hypertension in later life (Am J Hypertens 1:335-347, 1988). This novel perspective on the origins of essential hypertension was taken from the viewpoint that the development and maintenance of hypertension must involve a renal factor favoring sodium retention, thereby preventing pressure-induced natriuresis from restoring blood pressure toward normal levels. Since nephron numbers in the normal population range from 300,000 to 1,100,000 or more, it was reasoned that a congenital deficit in nephron endowment itself could be the renal risk factor for hypertension: demographic groups in whom hypertension is unusually prevalent tend to have smaller kidneys, implying fewer nephrons, and some inbred hypertensive rat strains have, on average, fewer nephrons than their respective normotensive controls. We argue that recent independent observations in humans relating low birth weight to both increased risk of hypertension in later life and the formation of fewer nephrons at birth lend strong support to the nephron number hypothesis. Moreover, independent experimental studies in rodents suggest that maternal protein intake during gestation is directly related to he numbers of nephrons formed and that when protein intake is restricted, the offspring develop hypertension in maturity. The concept that nephron numbers may be programmed during gestation, as these observations imply, is discussed in relation to the potential advantages and disadvantages of such a mechanism for the next generation; parallels are drawn with the relationship of low birth weight to pancreatic beta cell development and maturity-onset diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic theory of progressive renal disease: a 10-year update in brief review

Experimental studies have suggested that glomerular hypertension is ultimately damaging to the kidney. Prevention of glomerular hypertension by dietary protein restriction or antihypertensive therapy lessens glomerular injury in several experimental models of chronic renal disease. Glomerular hypertension and hyperfiltration also occur in humans with diabetes mellitus, solitary or remnant kidneys, and various forms of acquired renal disease. Clinical studies are beginning to show that dietary protein restriction and antihypertensive therapy may slow progression in these disorders. Large multicenter trials are currently under way to better define the effects of these therapeutic maneuvers on the progression of chronic renal disease.

Nephron underdosing: a programmed cause of chronic renal allograft failure

The findings cited in this report suggest that renal allograft survival might be improved by matching nephron supply to recipient needs (analogous to prescription dialysis based on Kt/V). Methods for assessing functional graft capacity (ie, nephron number, filtration, or total microvascular surface area) are needed. Graft weights might serve as a useful alternative until better indices are devised. Measures for defining and possibly reducing recipient demands are also needed to preserve graft performance. Where gross imbalances between nephron supply and recipient demand are not likely to be corrected over the long term by engraftment of a single kidney, consideration should be given to dual kidney transplantation, currently feasible only from cadaveric, but eventually from xenogeneic sources as well. The predicted longer survival and avoidance of premature return to end-stage renal disease with the transplantation of two kidneys in certain conditions could render this approach more rational, both in clinical and economic terms, than single kidney engraftment for those at greatest risk for shortened graft survival. The dosing of larger numbers of nephrons might also lessen the risk of coexistent hypertension and thereby reduce the magnitude and tempo of immune injury to the graft.

Prognosis of patients with unilateral renal agenesis

The clinical course was reviewed in 157 patients with unilateral renal agenesis and a normal contralateral kidney for the purpose of establishing a prognosis. There were 85 males (54%) and 72 females (46%). The mean age at diagnosis of unilateral renal agenesis was 37 years. The mean years at risk was 56. Proteinuria (> 150 mg/24 h) was found in 19% of the 37 patients tested (P < 0.001), hypertension developed in 47% of the 47 patients tested (P = 0.010), and renal function (adjusted for age and sex) was decreased in 13% of the 32 patients tested (P = 0.001). An increased filtration fraction was found in 7 (54%) of 13 patients evaluated. At the completion of this study, 114 patients (73%) were alive, and the survival rate was similar to that of age-, sex-matched United States life tables. Forty-three patients (27%) died; 6 deaths (4%) were caused by renal failure. Our review indicates that patients with unilateral renal agenesis and a normal solitary kidney are at increased risk of proteinuria, hypertension, and renal insufficiency. Therefore, it is essential to have prolonged and careful follow-up and to employ strategies that maximize renal preservation.

Single kidney function: early and late changes in urate transport after nephrectomy

Renal urate transport was studied by means of pyrazinamide (PZA) and probenecid (PB): (a) before and at 2, 6, 24 weeks (24 patients), (b) 1 to 30 years after uninephrectomy in 27 and 12 patients with Ccr greater than 80 and 30 to 70 ml/min, respectively. Uninephrectomy was followed by important tubular urate transport modifications during at least two weeks, which lead to a marked uricosuria as indicated by significant increase in FEur (mean value +/- SD, 0.228 +/- 0.059 vs. 0.097 +/- 0.014 and 0.099 +/- 0.019 in normals and chronically diseased solitary kidneys). Reduced response to PZA and PB suggests a diminished reabsorptive capacity for urate mainly at the presecretory site which persisted after FENa normalization. Tubular compensations were presumably complete at six weeks, since pattern of urate transport returned to normal with an almost complete reabsorption of filtered urate load (99%) and a percentage of postsecretory reabsorption (80%) very close to those seen in normal subjects with a pair of kidneys. The adjustment in urate excretion in solitary kidneys was achieved by a significant increase of secreted urate as compared with 50% of pre-uninephrectomy values. Thus, increased urate secretion by the remaining intact organ is sufficient to maintain urate balance with a normal serum level.

Morphological findings in 70 kidneys of living donors for renal transplant

Seventy donor kidneys for transplant were studied with light microscopy (LM), electron microscopy (EM) and immunofluorescence (IM) for C3, C4, Clq, IgG, IgA, IgE, IgM, and antifibrin; the samples were taken just before transplanting the allograft kidney. Glomerular changes were found in 35.7% of apparently normal living donors: 9 cases showed relative glomerular ischemia with an irregular basal membrane (12.9%); 5 cases showed a diffusely widened basal membrane without antecedents of hyperglycemia (7.1%); in one case (1.4%) there was a lesion similar to type 1 mesangio-capillary glomerulonephritis with C3++, IgG++, IgA+, and IgM+; in another case (1.4%) there were scant isolated C3 glomerular, subepithelial deposits with indentation of the basement membrane of the immunocomplex type with a microhematuria which was demonstrated only after donation, and in 9 cases (among them two pairs of siblings) there were mesangial IgA and mesangial electron-dense deposits compatible with Berger's disease (12.9%). None of these glomerulopathies were evident under LM.

The solitary kidney: a model of chronic hyperfiltration in humans

Reduction of renal mass (11/12) in rats leads to progressive azotemia, proteinuria, and hypertension. Less extensive renal ablation resulting from uninephrectomy also accelerates the progression of focal glomerulosclerosis (FGS) induced by experimental diabetes, renal irradiation, aminonucleoside nephrosis, or aging. The consequence of the absence of one kidney in man are examined in three different clinical situations. Unilateral renal agenesis seems to predispose to the development of FGS, but most reports include isolated cases and the true incidence of FGS is not known. The solitary kidney following uninephrectomy for acquired unilateral disease undergoes a compensatory rise in glomerular filtration rate (GFR) that remains stable for several decades. Finally, kidney donors followed for over 2 decades show unimpaired GFR, elevated at 70% to 80% of the normal (two-kidney) GFR. Some donors develop mild, nonprogressive proteinuria. Their incidence of hypertension matches that in the control population. Thus, hyperfiltration secondary to 50% reduction of renal mass in humans does not lead to loss of function of the remaining parenchyma.

Kidney function in adults born with unilateral renal agenesis or nephrectomized in childhood

We have evaluated the long-term prognosis in an unselected group of adult patients either uni-nephrectomized in childhood because of hydronephrosis or born with unilateral renal agenesis. Thirty-six patients aged 7-47 years were followed for 7-40 years. In 23 control subjects aged 20-47 years the glomerular filtration rate (GFR) and the p-aminohippuric acid clearance (CPAH) did not change significantly with age. In patients with a single kidney the size of that kidney was larger and GFR and CPAH were higher than single kidney values in control subjects. However, in patients with a single kidney since childhood the GFR and the CPAH declined slowly but significantly during the follow-up period. Significant microalbuminuria occurred in 47% of the patients with a single kidney and was more frequent with a longer follow-up period. No patient had renal insufficiency or a marked increase in arterial blood pressure. We conclude that in patients with a single kidney since childhood the long-term prognosis is good, but the late decrease in GFR and increase in albumin excretion may indicate a moderate risk for premature renal damage.

Effect of unilateral nephrectomy on three patients with histopathological evidence of diabetic glomerulosclerosis in the resected kidney

Diabetes mellitus and surgical ablation of renal tissue are two independent influences associated with hyperfiltration and elevated levels of the glomerular transcapillary hydraulic pressure differential (delta P). There is increasing evidence that hyperfiltration with elevated delta P is pathogenic and leads to glomerular damage. The authors questioned whether these two influences (surgical ablation of renal tissue and diabetes mellitus) would act in an additive fashion in human patients to produce an accelerated decline in renal function. Three patients with non-insulin-dependent diabetes mellitus who had undergone a unilateral nephrectomy (for a variety of reasons) were (retrospectively) identified. In each patient, morphologic evidence of diabetic glomerulonephropathy was present in the resected kidney. The charts from these patients were reviewed and post-nephrectomy renal function was estimated over time by plotting reciprocal serum creatine values versus time. Follow-up intervals after nephrectomy varied from 4 to 15 years. The results of our follow-up showed no obvious detrimental effect on renal function (as measured by 1/serum creatinine) attributable to the unilateral nephrectomy. The authors conclude that residual renal function (and ultimate outcome) in patients with non-insulin-dependent diabetes mellitus is highly variable, but does not seem to be adversely affected (at least over the time span of observation in these patients) by unilateral nephrectomy.