How reliable are ultrasound measurements of renal length in adults?

Normal sonographic measurements for kidney dimensions in Saudi adult population: A cross-sectional prospective study

BACKGROUND

The use of ultrasound-based measurements to determine renal size has proven valuable in the diagnosis of renal function and associated disorders. The dimensions of the abdominal organs are affected by an individual's body age, height, sex, and weight. The objective of this study was to establish the standard sonographic parameters for renal dimensions and to determine the correlation between body measurements and renal dimensions in a population of healthy adults residing in Jazan City, Saudi Arabia.

METHODS

The present study was a prospective study conducted at a single center located in Jazan City from February to August 2022. Ninety-five participants underwent abdominal ultrasonography. The process of measuring renal size through sonography entails the measurement of various dimensions of the kidney, such as renal length, width, and thickness. The demographic information of the participants, including their sex, age, height, and weight, was documented. All analyses were performed using Statistical Package for the Social Sciences v27 software.

RESULTS

The dimensions of the right kidney, specifically the length, width, and thickness, had mean value of 9.79 centimeters (cm), 5.09 cm, and 4.10 cm, respectively. The left kidney had mean dimensions of 10.1 cm, 5.09 cm, and 4.10 cm for length, width, and thickness, respectively. The left kidney was larger than the right kidney. Furthermore, male participants exhibited larger kidney measurements than their female counterparts did. A noteworthy positive correlation was observed between the thickness of the left kidney and sex, whereas no significant correlations were found with age, weight, or height.

CONCLUSION

The current study revealed that the kidney dimensions were observed to be larger in males as compared to females. The research findings indicate that there is no significant correlation between kidney dimensions and various demographic factors, such as age, height, weight, and sex. In addition, this study provides reference tables for further use.

Early Renal Ultrasound in Patients with Congenital Solitary Kidney Can Guide Follow-Up Strategy Reducing Costs While Keeping Long-Term Prognostic Information

We aimed to evaluate the prognostic value of renal length (RL) > 2 standard deviation scores (SDS) measured by renal ultrasound (RUS), across infancy, childhood and adolescence, in identifying which patients with congenital solitary functioning kidney (CSFK) are at lower risk of developing kidney injury (KI). We also estimated the cost saving of integrating the current follow-up protocols with an early RUS algorithm (ERUSA). Fifty-six CSFK adult patients who were 1–3 months old at first observation of undergoing RUS were enrolled. KI was defined by hypertension and/or proteinuria and/or declined renal function. ERUSA was assessed by early (at 1–3 months of life) RUS and was retrospectively tested in our patients. ERUSA establishes that patients with RL > 2SDS at early RUS do not undergo further follow-ups. The others undergo another RUS at 1 year of age along with follow-ups according with current protocols, with the exception of RUS which could be no longer performed. Direct and indirect costs were calculated for each analysed protocol and the cost saving of applying ERUSA was calculated. None of the patients with early RL > 2SDS presented KI in adulthood. A RL > 2SDS was predictive of absence of KI only at 1–3 months (OR = infinity) and 1 year of age (OR = 0.13; 95%CI: 0.03–0.66; p = 0.01). ERUSA provided a total cost-sparing ranging from 38.6% to 55.3% among the analysed follow-up protocols. With ERUSA, no patients developing KI in adulthood were missed. In conclusion, only a RL > 2SDS at 1–3 months and 1 year of age predicted good prognosis in young adulthood. ERUSA can guide a cost-sparing follow-up strategy in CSFK patients while maintaining important long-term information.

How reliable is renal ultrasound to measure renal length and volume in patients with chronic kidney disease compared with magnetic resonance imaging?

Background

Renal length, volume, and parenchymal thickness are important clinical parameters, yet data concerning the accuracy and reproducibility of ultrasound (US)-based renal length and volume assessment in patients with chronic kidney disease (CKD) are scarce.

Purpose

To establish whether renal length, volume, and parenchymal thickness can be reliably measured with renal US in patients with CKD.

Material and Methods

All participants underwent renal US, immediately followed by 3-T magnetic resonance imaging (MRI). Renal length, width, transverse diameter, and parenchyma thickness were measured with both methods; renal volume was calculated using the ellipsoid formula. A total of 45 patients with CKD (eGFR [mean ± SD] 57.4 ± 4.4 mL/min/1.73 m2) and 46 participants without CKD (eGFR 97.0 ± 2.4 mL/min/1.73 m2) were included.

Results

US-measured renal length correlated strongly with MRI-measured renal length in no-CKD patients (Spearman’s r = 0.83 and 0.85 for the right and left kidney, respectively; P < 0.005) and CKD patients (r = 0.89 and 0.92 for the right and left kidney, respectively; P < 0.005). There was a significant but weaker correlation between MRI- and US-measured right and left renal volume (r = 0.72, P < 0.005) in no-CKD (r = 0.74 and r = 0.72, respectively; for both: P < 0.005) and CKD patients (r = 0.83 and 0.85, P < 0.005). Weak to moderate correlations were found for parenchyma thickness for the right (CKD group: r = 0.29, no-CKD: r = 0.23; for both: P < 0.05) and left kidney (CKD: r = 0.52, no-CKD group: r = 0.37, P < 0.05). Both intra-observer (Pearson’s correlations of 0.82 for the right and 0.89 for the left kidney) and inter-observer (Lin’s correlation coefficient of 0.90 for the right and 0.82 for the left kidney) reproducibility of US-assessed renal length was high.

Conclusions

US-based assessment of renal length in CKD patients is comparable to MRI measures. Both intra- and inter-observer reproducibility of US-assessed renal length in CKD patients are high. Measurements of US renal volume and parenchymal thickness should, however, be interpreted with caution.

Decrease in 1-year Kidney Graft Size Predicts Inferior Outcomes After Deceased Donor Kidney Transplantation

BACKGROUND

Longest bipolar length of the kidney graft is routinely measured for ultrasonographic assessment of graft size (GS), although the value of the graft length remains unclear.

METHODS

In a single-center, observational study involving 319 deceased-donor kidney transplant recipients, we assessed variations in absolute and adjusted GS (corrected for body surface area) between 1 and 12 months after transplantation ([INCREMENT]GS1m→12m). We tested whether variations in GS during the first year were predictive of the composite outcome of a reduction of 50% or more in the estimated glomerular filtration rate or end-stage graft failure.

RESULTS

At 1 year after transplantation, 121 patients (38%) had a decrease in GS ([INCREMENT]GS1m→12m <0), and 198 patients (62%) had an increase in GS ([INCREMENT]GS1m→12m ≥0). After a median follow-up of 53 months, 41 patients with a decrease in GS reached the composite outcome as compared with 12 patients with an increase in GS (34% and 6%, respectively; P < 0.001). Areas under the receiver operating characteristics curves of absolute and adjusted [INCREMENT]GS1m→12m for composite outcome were 0.81 (95% confidence interval [95% CI], 0.74-0.88) and 0.78 (95% CI, 0.70-0.86), respectively. In multivariate analysis, the risk of the composite outcome was significantly higher among patients with a decrease in GS during the first year after transplantation (hazard ratio, 4.55; 95% CI, 2.35-8.81; P < 0.001).

CONCLUSIONS

A decrease in kidney GS during the first year after transplantation, as compared with an increase in GS, is a powerful predictor of subsequent graft dysfunction or end-stage graft failure.

Validation of a novel translumbar ultrasound technique for measuring renal dimensions in horses

A reliable method for obtaining renal ultrasonographic measurements in the horse is important for diagnosis and monitoring of clinical renal disease. The aims of this prospective study were to develop and validate a novel translumbar ultrasound technique for measuring renal dimensions in horses. Six Thoroughbred or Thoroughbred part bred horses were recruited. All horses were scheduled for euthanasia due to reasons unrelated to the kidneys. Two observers recorded renal length, width, and depth; and dimensions of the cortex, medulla, pyramids, and pelvis for both kidneys in each horse using novel translumbar and conventional transabdominal ultrasound methods. The same measurements were recorded from post-mortem renal specimens. Both kidneys were consistently identified by both methods in the 15-17th intercostal spaces and paralumbar fossa. Using the translumbar technique, maximal dimensions were obtained for the left kidney in the 16th intercostal space (length 16.2 ± 2.0 cm, width 11.8 ± 0.5 cm, depth 6.4 ± 0.9 cm) and for the right kidney in the 15th intercostal space (length 16.1 ± 1.2 cm, width 13.4 ± 1.2 cm, depth 6.7 ± 0.7 cm). Renal dimensions obtained by transabdominal and translumbar projections did not differ (P > 0.05). Good correlations were found between overall renal dimensions and post-mortem measurements for both ultrasound techniques (r(2) > 0.8), but were better for the translumbar method (mean r(2) = 0.92 cf. 0.88). Good-to-excellent reliability was found for all translumbar ultrasound measurements except for the renal cortex. Reproducibility was better for the larger (overall length, width, and depth) than the smaller (cortex, medulla, and pyramids) structures. Findings indicated that translumbar ultrasonography is a valid method for measuring renal dimensions in horses.

Predictors of diabetic nephropathy

Diabetic nephropathy (DN) is a leading cause of morbidity and mortality in diabetic patients representing a huge health and economic burden. Alarming recent data described diabetes as an unprecedented worldwide epidemic, with a prevalence of ∼6.4% of the world population in 2010, while the prevalence of CKD among diabetics was approximately 40%. With a clinical field hungry for novel markers predicting DN, several clinical and laboratory markers were identified lately with the promise of reliable DN prediction. Among those are age, gender, hypertension, smoking, sex hormones and anemia. In addition, eccentric left ventricular geometric patterns, detected by echocardiography, and renal hypertrophy, revealed by ultrasonography, are promising new markers predicting DN development. Serum and urinary markers are still invaluable elements, including serum uric acid, microalbuminuria, macroalbuminuria, urinary liver-type fatty acid-binding protein (u-LFABP), and urinary nephrin. Moreover, studies have illustrated a tight relationship between obstructive sleep apnea and the development of DN. The purpose of this review is to present the latest advances in identifying promising predictors to DN, which will help guide the future research questions in this field. Aiming at limiting this paramount threat, further efforts are necessary to identify and control independent modifiable risk factors, while developing an integrative algorithm for utilization in DN future screening programs.

Decrease rate of the renal diameter in chronic hemodialysis patients

We here present the results of ultrasonographic (US) evaluations on the alteration of renal diameter of chronic HD patients. Of 109 outpatient HD patients who had neither severe acquired cystic disease of the kidney nor hereditary polycystic kidney disease, we performed US two or three times to measure their maximum renal diameter (mean of both kidneys), and the yearly alteration rate was calculated. The average interval of the two measurements was 35.9 months, and the average HD duration from the HD induction to the first measurement was 29.5 months. The average decrease rate of renal diameter was 4.34 ± 0.4 (SE) mm/year. No statistical difference was seen on the decrease rate in relation to gender, age and original disease (among three groups, glomerulonephritis and IgA nephropathy, diabetes, and others including hypertension). However, the decrease rate was large when the first measurement was close to the induction of hemodialysis, suggesting that the alteration rate reduced according to the hemodialysis vintage (5.3 ± 0.8 mm/year, first measurement not more than 10 months after induction of HD and 1.5 ± 1.6 mm/year, first measurement more than 80 months after induction of HD). Renal diameter decreased approximately 4.3 mm each year, and the decrease rate slowed as the length of time on dialysis increased.

Comparison of renal ultrasonographic measurements between healthy cats of three cat breeds: Ragdoll, British Shorthair and Sphynx

Healthy cats of three cat breeds — Sphynx (n = 11), British Shorthair (n = 15) and Ragdoll (n = 15) — were included in this study. All cats underwent an ultrasonographic examination to assess renal length, cortical thickness, medullary thickness and corticomedullary ratio. Of all ultrasonographic measurements, renal length showed the highest variation. For all ultrasonographic dimensions, individual and kidney side (left vs right) variation were much more pronounced than interbreed variation. Sphynx cats tended to have larger kidneys (4.09 ± 0.33 cm) than British Shorthair (3.77 ± 0.43 cm) and Ragdoll cats (3.87 ± 0.41 cm). British Shorthair cats, however, tended to have a thinner cortex (0.67 ± 0.13 cm) and medulla (0.76 ± 0.18 cm) than Sphynx (0.76 ± 0.14 cm and 0.90 ± 0.25 cm, respectively) and Ragdoll cats (0.75 ± 0.13 cm and 0.91 ± 0.22 cm, respectively). However, statistical tests did not reveal significant differences between these cat breeds. The corticomedullary ratio was similar for the three cat breeds (Sphynx: 0.93 ± 0.43; British Shorthair: 0.91 ± 0.26; Ragdoll: 0.88 ± 0.31). The left kidney (3.83 ± 0.42 cm) was significantly smaller than the right kidney (3.99 ± 0.40 cm) and showed a thicker medulla (left: 0.93 ± 0.21 cm, right: 0.79 ± 0.22 cm), and thus a lower corticomedullary ratio (left: 0.80 ± 0.23, right: 1.01 ± 0.32). For the cortical thickness, no significant difference was observed between the left (0.71 ± 0.14 cm) and right kidney (0.74 ± 0.14 cm).

Renal evaluation of Aotus azarai infulatus by ultrasonography and serum chemistry profile

This study aimed to characterize anatomical and biochemical properties of owl monkey kidneys in order to provide normal reference values. Sixty-nine Aotus azarai infulatus (45 males and 24 females) were divided into four different age groups (AG1: 3 months-1 year; AG2: 2-3 years; AG3: 4-6 years; and AG4: over 7 years old). The monkeys were evaluated with a serum chemistry profile, focusing on serum creatinine (SCr) and blood urea nitrogen (BUN) and with ultrasound. Mean body mass differed among the age groups. This significance was attributed to AG1 body mass being significantly lower than in AG2 and that in both AG2 and AG3 being significantly lower than in the two older age groups (AG3 and AG4). SCr and BUN concentrations differed significantly between the sexes and SCr level correlated positively with age. In contrast, renal measurements did not differ between males and females. Left and right renal volumes did not differ significantly within age groups, or among AG2, AG3, and AG4. Renal volumes in AG1, however, while not differing from those in AG2, did differ significantly from those in AG3 and AG4. In conclusion, this study provides ultrasonographic reference values for the morphology the kidneys in A. a. infulatus. Evidence is also provided that SCr and BUN levels in owl monkeys are influenced by the sex and age of the individual, factors that should be considered when interpreting test results.

Evaluation of kidney size in children: a pilot study of renal length as a surrogate of organ growth

Purpose

Somatic growth is an important indicator of health in children. Adequate organ growth is essential in growth and directly related to body growth. We consider renal length as a surrogate of organ growth in growing children. Measurement of weight, height, and many anthropometric indices, such as body surface area (BSA), body mass index (BMI), and Rohrer and Kaup indices, are used to evaluate growth status. The aim of this study was to evaluate the association between renal length and somatic parameters and analyze the affecting factors for renal size during growth.

Methods

The data for renal length in 66 children (age, 12.9±15.6 months; male/female, 34/32) were obtained. Each kidney was measured with ultrasonography and dimercaptosuccinic acid scan. The data on age, sex, height, and weight were obtained from the medical records. BSA, BMI, and Rohrer and Kaup indices were calculated from measured height and weight. BSA was calculated by 2 methods, and is expressed as BSA I and BSA II.

Results

There were significant correlations between renal size and age, weight, height, BSA I, BSA II, and Rohrer index. In the regression analysis, the most significant contributing factor to renal growth was height (R²=0.636, P<0.001).

Conclusion

Height seems to be the most important factor associated with organ growth in growing children. Further studies to evaluate adequate organ growth should be carried out.

The morphometric development and arterial vascularization of bovine fetal kidneys in the prenatal period

This study presents a morphometric developmental analysis of bovine kidneys and a demonstration of intrarenal arterial vascularization in the prenatal period. A total of 40 Holstein bovine fetuses constituted the material of the study. The fetuses were divided into three groups, according to the gestational stages they belonged to early, mid- and late stages, such that each group comprised 10 fetuses. Sixty kidneys and their renal arteries were evaluated using morphometric measurements. Furthermore, 10 bovine fetuses were injected with cast solution to demonstrate the intrarenal arteries. Data obtained in the present study were statistically analyzed. Although the right and left kidneys did not significantly differ from each other, significant differences existed between the different gestational stages (P<0.05). The kidney parameters, including length, width and thickness, were positively correlated with both the right and left kidneys as well as with gestational age. Four types of intrarenal arterial segmentation were demonstrated. Type I was observed in 10 kidneys (50%), type II in four kidneys (20%) as well as type III, and type IV in only two kidneys (10%). In the most frequent arterial segmentation type (type I), the renal artery divided into three segmental arteries, which supplied the cranial polar, medial and caudal polar regions of the kidney, after stemming from the abdominal aorta. Furthermore, cases of double and multiple renal arteries were also observed.

Reference ranges and reliability of transabdominal ultrasonographic renal dimensions in thoroughbred horses

The aims of this study were to establish a normal reference range (mean ± 2 SD) and assess reliability of renal dimensions obtained using transabdominal ultrasonography in Thoroughbred horses (n = 7). A minimum of three ultrasonographic cineloops were obtained from each intercostal space and the left paralumbar fossa by two observers daily for three consecutive days. Renal length, width, and thickness and cortex, medulla, and pelvic dimensions were obtained. Measurements were undertaken by both observers, who were unaware of prior measurements, to assess reproducibility and measured on three separate occasions to evaluate short-term measurement repeatability. Measurements from images obtained by both operators were compared to evaluate image repeatability. The left kidney was consistently identified in the left 15th-17th intercostal space and the paralumbar fossa with maximal length in the 16th intercostal space (12.7 ± 2.0 cm) and maximal width in the paralumbar fossa (7.9 ± 1.1 cm). The right kidney was consistently identified in the right 15th-17th intercostal space with maximal length and maximal width in the 15th intercostal space (16.0 ± 0.7 cm and 7.9 ± 1.0 cm). Reproducibility, image repeatability, measurement repeatability were good to excellent, although were less good for the smaller structures. There were no differences in renal dimensions between horses. Overall renal ultrasonography was reliable and a normal reference range for Thoroughbred horses was established. Renal dimensions vary between rib spaces. As repeatability and reproducibility were excellent for renal length and width, it may be prudent to use those measurements in rib spaces where parameters were maximal.

Predictors of kidney dimensions measured by multi-detector computed tomography (MDCT) in 930 middle-aged and elderly patients

PURPOSE

A few studies investigated renal size using computed tomography (CT) in middle-aged and elderly patients while taking renal function into account. Thus, we aimed to assess kidney dimensions and their predictors in patients without known renal disease by multi-detector computed tomography (MDCT).

METHODS

This is a 6-month-long prospective observational study. Estimated glomerular filtration rate (eGFR) was calculated with Cockcroft-Gault (CG) and modification of diet in renal disease (MDRD) formulas. Pole-to-pole kidney length (R1) was determined from coronal and sagittal oblique images. Kidney length (R2), width (R3), and parenchymal thickness were measured in axial slices.

RESULTS

The data of the 930 patients were included in this study. CG-eGFR was more closely correlated with R1, R2, and R3 than MDRD-eGFR. CG-eGFR, female gender, and presence of diabetes mellitus were independent predictors of R1 size in logistic regression analyses.

CONCLUSION

Kidney sizes diminish with advancing age. CG-eGFR shows a better correlation with kidney dimensions compared with MDRD. Overall, age was a stronger determinant of eGFR than renal dimensions.

Measurement of renal dimensions in vivo: A critical appraisal

Kidney volume is regarded as the most precise indicator of kidney size. However, volume assessment is not widely used clinically because its measurement is difficult due to the complex kidney shape. Apart from the conventional methods of measurement of renal dimensions from X-rays, ultrasound scan, computed tomography scan and magnetic resonance imaging have evolved as the three best modalities for this purpose currently. Assessment of kidney size should also be made individually since many factors like body mass index, height, gender, age, position of kidneys, sex, stenoses and number of renal arteries influence the measurements. In this paper, we have critically analysed the advantages and disadvantages of the various methods of renal morphometry, by reviewing the literature spanning over the period of 1976 - 2009.

Large kidneys predict poor renal outcome in subjects with diabetes and chronic kidney disease

Background

Renal hypertrophy occurs early in diabetic nephropathy, its later value is unknown. Do large kidneys still predict poor outcome in patients with diabetes and Chronic Kidney Disease (CKD)?

Methods

Seventy-five patients with diabetes and CKD according to a Glomerular Filtration Rate (GFR, by 51Cr-EDTA clearance) below 60 mL/min/1.73 m² or an Albumin Excretion Rate above 30 mg/24 H, had an ultrasound imaging of the kidneys and were cooperatively followed during five years by the Diabetology and Nephrology departments of the Centre Hospitalier Universitaire de Bordeaux.

Results

The patients were mainly men (44/75), aged 62 ± 13 yrs, with long-standing diabetes (duration:17 ± 9 yrs, 55/75 type 2), and CKD: initial GFR: 56.5 (8.5-209) mL/min/1.73 m², AER: 196 (20-2358) mg/24 H. Their mean kidney lenght (108 ± 13 mm, 67-147) was correlated to the GFR (r = 0.23, p < 0.05). During the follow-up, 9/11 of the patients who had to start dialysis came from the half with the largest kidneys (LogRank: p < 0.05), despite a 40% higher initial isotopic GFR. Serum creatinine were initially lower (Small kidneys: 125 (79-320) μmol/L, Large: 103 (50-371), p < 0.05), but significantly increased in the "large kidneys" group at the end of the follow-up (Small kidneys: 129 (69-283) μmol/L, Large: 140 (50-952), p < 0.005 vs initial). The difference persisted in the patients with severe renal failure (KDOQI stages 4,5).

Conclusions

Large kidneys still predict progression in advanced CKD complicating diabetes. In these patients, ultrasound imaging not only excludes obstructive renal disease, but also provides information on the progression of the renal disease.

Reduced renal length and volume 20 years after very preterm birth

Intrauterine growth retardation is presumed to be associated with decreased renal size and impaired renal function as a result of stunted kidney development and nephron deficit. To study whether very preterm birth also affects renal size at young adulthood, we sonographically measured bipolar kidney length and volume in 51 very premature individuals (<32 weeks of gestation), either small (SGA) or appropriate (AGA) for gestational age (22 SGA and 29 AGA), and 30 full-term controls 20 years after birth. Relative kidney length and volume were calculated. Both absolute and relative left kidney length and volume were significantly lower in SGA and AGA individuals, notably in women. Renal size did not differ between SGA and AGA individuals. In 70% of controls, the left kidney was larger than the right one compared with 40.9% in SGA [relative risk (RR) 1.7; 95% confidence interval (CI) 1.0-3.0] and 48.3% in AGA (RR 1.5; 95% CI 0.9-2.3) individuals. Renal structural anomalies were present in eight prematurely born participants only. Our data suggest that kidney growth is stunted after preterm birth, especially on the left side, and in the female gender.

A longitudinal study of kidney structure and function in adults

BACKGROUND

Although kidney size is commonly measured in patients with chronic kidney disease (CKD), its relationship with kidney function is poorly understood. We conducted this longitudinal study to better understand the relationship between kidney size and function.

METHODS

We retrospectively studied 178 kidneys measured by ultrasound in 93 patients with CKD who did not have autosomal polycystic kidney disease. Renal function was measured using estimated glomerular filtration rate (GFR). A mixed model that accounted for repeated measurements or nested observations was used for statistical analysis.

RESULTS

In cross-sectional analyses, the following independent variables emerged as predictors of kidney size: estimated GFR along with its squared term, height, age and interactions of each of these two independent variables with aetiology of CKD. In longitudinal analyses over a median follow-up of 3.7 years, after accounting for predictors of baseline kidney size such as aetiology, height and estimated GFR, we found that kidney atrophy occurred at a rate of 0.072 cm/year (SD 0.016, P = 0.007). This atrophy was 'blunted' with declining GFR. Each 1 mL/min/1.73 m(2)/year greater decline in eGFR abrogated kidney atrophy by 0.015 cm/year (P = 0.024).

CONCLUSION

Although in cross-sectional surveys kidney size is directly related to function, the longitudinal relationship between form and function is inverted. Since the rate of change in GFR determines kidney atrophy, we conclude that kidney size is a determinant of renal prognosis.

A Case of Chronic Renal Dysfunction Following Treatment with Oral Acyclovir

Nephrotoxicity is a well-known side effect of intravenous acyclovir treatment but occurs rarely by oral treatment. A 76-y-old healthy male, with normal baseline renal functions (blood creatinine 0.6 mg%), received oral acyclovir at a dose of 800 mg five times daily for 10 days for treatment of herpes zoster ophthalmicus. He developed renal failure with blood creatinine levels of 3 mg% and his renal function failed to improve within eight months of end of treatment. Affection of renal function has to be considered also in relation to oral acyclovir treatment, especially in elderly subjects.

Reliability of renal ultrasound measurements in children

The aim of the investigation reported here was to assess the intraobserver and interobserver variability of renal measurements in children. The study comprised 56 paired measurements in 28 children (median age 7.5 years, range 3.0-15.0 years) without renal or ureterovesical anomalies. Intraobserver and interobserver reproducibility was assessed by repeated measurements of the left and right renal length, width, and thickness. Intraclass correlation coefficients (ICCs) with the corresponding 95% confidence interval (CI) were calculated. Bland and Altman plots were computed to assess the agreement of the measurements. Limits of agreement +/- 2 standard deviations (SD) for the mean differences in renal measurements were derived. Intraobserver ICCs ranged from 0.93 (left and right renal width and right renal thickness) to 0.99 (left renal length), and interobserver ICCs ranged from 0.64 (right renal thickness) to 0.90 (right renal length). Limits of agreement in the Bland and Altman plots ranged from -8.0 to 9.2% (intraobserver left renal width) to the widest limit from -18.0 to 19.2% (interobserver left renal length). Overall, this study demonstrated the good reproducibility and agreement of most renal dimensions in children measured by ultrasound (US). Based on these results, we conclude that US is an appropriate measure to assess renal dimensions in both clinical and epidemiological studies.

Measurement of kidney volume with multi-detector computed tomography scanning in young Korean

PURPOSE

Kidney volume is regarded as the most precise indicator of kidney size. However, it is not widely used clinically, because its measurement is difficult due to the complex kidney shape. We attempted to evaluate the normal kidney volume in young Korean men by using multi-detector computed tomography (MDCT).

MATERIALS AND METHODS

We retrospectively reviewed MDCT data of young Korean men (113 patients). After data processing, we measured the volume and length of the kidneys. Body parameters (height, body weight, body-surface area, and total body water) and laboratory data were collected. Glomerular filtration rate (GFR) was calculated using Cockcroft-Gault (CG) equation.

RESULTS

The mean kidney volume was 205.29 +/- 36.81 cm(3); and mean kidney length was 10.80 +/- 0.69 cm. The former correlated significantly with height, body weight, body-surface area, and total body water (p < 0.05, correlation coefficient : gamma = 0.328, 0.649, 0.640, and 0.638, respectively). The latter also correlated significantly with all body indexes, however the correlation was weaker, except with height (p < 0.05, correlation coefficient : gamma = 0.457, 0.473, 0.505, and 0.503, respectively). Only kidney volume significantly predicted estimated GFR (adjusted R(2) = 0.431, F = 85.90 and p < 0.05).

CONCLUSION

The kidney volume measured with MDCT is correlated well with body parameters, and is useful to predict renal function.

The effect of fluid intake on renal length measurement in adults

PURPOSE

To evaluate whether oral fluid intake has an effect on renal length as determined with sonography.

METHODS

We studied 524 adult patients who were referred to our ultrasound unit with complaints other than urinary tract symptoms. The mean age of the patients was 44 years (range 17-76). All of the measurements were performed with the patient in the prone position. The renal length of each kidney was measured by the same observer before and after oral fluid intake. Student's t-test was applied for the statistical significance of renal length measurements before and after hydration. Analysis of variance was performed for the effect of age and sex on the renal length measurements.

RESULTS

The mean renal length on the right side was 106.2 +/- 5.5 mm and 107.5 +/- 5.7 mm on the left side before hydration. There was no statistically significant difference between right and left side renal length measurements. After hydration, the mean renal length was 113.5 +/- 6.1 mm on the right side and 114.6 +/- 6.6 mm on the left side. The mean increase in renal length after hydration was statistically significant (P < 0.001) and was 6.8% on the right side and 6.6% on the left side. Sex and age did not affect the measurements significantly.

CONCLUSIONS

Oral fluid intake causes a statistically significant increase in renal length. This observation should be taken into consideration when renal length measurements are clinicallly important.

Sonographic assessment of the severity and progression of autosomal dominant polycystic kidney disease: the Consortium of Renal Imaging Studies in Polycystic Kidney Disease (CRISP)

BACKGROUND

The accuracy and precision of ultrasonography (US) in assessing the severity of autosomal dominant polycystic kidney disease (ADPKD) is unknown.

METHODS

US and magnetic resonance imaging (MRI) were performed at baseline and 1 year on 230 subjects with ADPKD. Ellipsoid volume was calculated from US length, width, and depth, and sequential transverse images were used to measure total and cystic volume directly. These were compared with MRI measurements of kidney volume and cystic volume.

RESULTS

Variability between different sonographers ranged from 18% to 42%. Correlations between US and MRI volume were 0.88 and 0.89. The SD of the discrepancy from MRI ranged from 21% to 33% and was unrelated to kidney size or body mass. Kidney length was the most reproducible measurement, and its correlation with MRI volume was 0.84. All patients with an US volume less than 700 cm3 had an MRI volume less than 1,000 cm3, and all patients with an US volume greater than 1,700 cm3 had an MRI volume greater than 1,000 cm3. Increases in volume after 1 year were 12% +/- 36% for the ellipsoid method, 6% +/- 29% for the direct method, and 4.2% +/- 7.2% for MRI. Correlation between US and MRI measurement of fractional cyst volume was 0.80.

CONCLUSION

Sonographic measurement of kidney volume in patients with ADPKD is inaccurate and lacks the precision necessary to measure short-term disease progression. However, sonography can provide an estimate of kidney volume that reflects severity and prognosis in individual patients.

Ultrasound measured renal length versus low dose CT volume in predicting single kidney glomerular filtration rate

Ultrasound measured renal length and CT measured renal volume are potential surrogate markers for single kidney glomerular filtration rate (SKGFR). The aims of this study are to determine: (1) the repeatability of ultrasound measured length and low radiation dose spiral CT measured volume; (2) the relationship between renal length and volume; and (3) whether length and/or volume is a predictor of SKGFR. 69 patients with suspected renal artery stenosis underwent ultrasound renal length measurement, CT evaluation of renal volume and assessment of SKGFR. 40 patients had ultrasound measurement of length and CT evaluation of volume performed twice on two separate visits. 25 patients also had ultrasound measured renal parenchymal thickness and area. The region of interest was drawn around the kidneys and a threshold set to subtract renal peripelvic fat and renal pelvis. The volume from each slice was summed to obtain the total volume for each kidney. The limits of agreement for ultrasound measured renal length were -1.6 cm to 1.52 cm and that for CT renal volume were -33 ml to 32 ml. There was significant correlation between ultrasound measured length and CT volume (r=0.74, p<0.01). Volume was a better predictor of SKGFR (r(2)=0.57) than length (r(2)=0.48). The combined parameters of ultrasound measured length, area and parenchymal thickness were a better predictor of volume (r(2)=0.81) and SKGFR (r(2)=0.58) than ultrasound measured length on its own. The low dose CT technique was reasonably reproducible and renal volume measurements correlate better with SKGFR than length. Ultrasound predictions of renal volume and SKGFR can be improved by incorporating cross-sectional area and parenchymal thickness. Further investigation is required to refine our low dose CT technique.

Kidney growth in 717 healthy children aged 0-18 months: a longitudinal cohort study

Kidney size is an important parameter in the evaluation of children with renal disease. However, reference materials for kidney size in healthy children have been limited beyond the neonatal period. We performed a longitudinal cohort study of 717 healthy children born at term with normal birth weight. Kidney size and shape were determined by ultrasonography and related to gender, age, and body size (weight, length, body surface area, skinfold thickness) at 0, 3, and 18 months of age. Gender-differentiated reference charts were established. Boys had significantly larger kidney volumes than girls ( P<0.001) and larger relative volumes (kidney volume/weight) at 0 and 3 months ( P<0.001), but not at 18 months of age. The best single predictor of gender-differentiated kidney volume was weight. Relative kidney volume changed with increasing age and height in a two-phase pattern: an initial decrease until a height of 65-70 cm was reached followed by a stable level. In conclusion, kidney size was significantly influenced by gender, age, and body composition. Relative kidney volume decreased with increasing age and height in a two-phase pattern. These characteristic changes in kidney volume indicated that infant kidney growth might be influenced by sex steroids and growth hormone in addition to body composition.

The reproducibility and short-term and long-term repeatability of sonographic measurement of splenic length

This study was undertaken to evaluate the reproducibility (interobserver variability), and the short-term and long-term repeatability (intraobserver variability) of sonographic measurement of the maximum and mean splenic length. Ultrasound (US) measurements of the splenic length were performed in 43 subjects, ages 30 to 59 years old (mean age = 44.5 years). Each subject attended three US sessions: baseline examination and 30 min and 8 weeks after the baseline examination. In each session, US examinations of the spleen were performed and the splenic length was measured by four operators. In each examination, the splenic length was measured 3 times, and the maximum and mean values were obtained. The overall reproducibility of the measurements of maximum and mean splenic lengths were 67% and 89%, respectively. The short-term repeatability in measuring the maximum and mean splenic lengths were 87% and 94%, respectively, whereas the long-term repeatabilities were 61% and 76%, respectively. The reproducibility and short-term and long-term repeatability of the measurement of mean splenic length were higher than those of the maximum splenic length. In the mean and maximum splenic length measurement, the short-term repeatability was higher than the long-term repeatability. The results suggested that the mean splenic length has a higher reliability in sonographic measurement and should be used in routine clinical practice. Measurement errors should be considered when evaluating the changes of splenic length in serial US examinations, particularly in long-term follow-up.

Reduced kidney size in patients with simple renal cysts

BACKGROUND

Renal cysts frequently occur in the absence of genetic diseases but their significance is unknown. Since multiple cysts develop in many patients with advanced renal disease, we tested the hypothesis that isolated cysts are associated with early nephron loss.

METHODS

All inpatient and outpatient sonograms performed by the Renal Division since 1995 were reviewed and, after exclusion of duplicate studies, patients with genetic cystic disorders, complex cysts, hydronephrosis, peripelvic cysts, end-stage renal disease and transplanted kidneys, 2526 were selected for this study, of which 385 had one or more cysts. Maximum renal length was used as an indication of size, and renal function was estimated by serum creatinine concentration.

RESULTS

Both right and left kidney length were significantly less in patients with cysts (P < 0.0001), independent of which kidney contained the cyst(s). Renal lengths were less in patients with multiple cysts as opposed to single cysts but not in patients with bilateral cysts as compared to unilateral cysts. Cysts were twice as frequent in solitary kidneys than in dual kidneys (P = 0.01). In outpatients matched for age and gender, those with cysts had a higher serum creatinine concentration but with borderline significance (P = 0.06). Multivariate analysis revealed that age, gender, and renal length were each independent variables and together accounted for one third of the incidence of cysts.

CONCLUSION

Kidney size is reduced in patients with simple renal cysts noted on renal sonography, and cysts may be associated with reduced renal function. This suggests that isolated cysts are an indication of nephron loss in patients with renal abnormalities.

Appraising surgeons learning sonography: measuring measurement variability

PURPOSE

Sonography is increasingly used by various clinicians in several task-specific situations. We present a method of assessing 1 aspect of a nonspecialist's ability in performing sonography, measurement variability.

METHODS

An experienced radiologist and a surgeon who had received 4 weeks of sonography training each made triplicate measurements of gallbladder dimensions in 19 adult patients undergoing abdominal sonography. The observers examined the subjects in immediate succession using the same ultrasound equipment and were blinded to each other's measurements until the end of the study. Intraobserver measurement variability rates were calculated for gallbladder length, height, and width by using analysis of variance techniques and were expressed as a within-subject standard deviation and a repeatability coefficient.

RESULTS

In terms of intraobserver measurements, the estimated within-subject standard deviations were comparable for the radiologist and the surgeon (length, 0.22 versus 0.17 cm; height, 0.14 versus 0.14 cm; and width, 0.12 versus 0.14 cm, respectively), as were the repeatability coefficients. The interobserver variability showed good agreement as well; the estimated within-subject standard deviations (and 95% limits of agreement) obtained were length, 0.47 cm (-1.08 to 1.48 cm); height, 0.34 cm (-1.08 to 0.49 cm); and width, 0.28 cm (-0.80 to 0.81 cm).

CONCLUSIONS

The ability to measure organ dimensions accurately is an essential sonographic skill that can be readily appraised. The findings from this comparison study illustrate that this 1 small aspect of sonography can be learned by various clinicians and that their ability in this task can be appraised. In a clinical setting, the small degree of variability in measurements made by the experienced radiologist and the sonography-trainee surgeon is likely to be satisfactory.

Sonographic measurement of kidney size in geriatric patients

PURPOSE

The aim of this study was to compare the value of absolute and relative renal length (ARL and RRL, respectively) measurements in determining variations in normal kidney size related to sex, body height, and increasing age among patients older than 60 years.

METHODS

Kidney sizes were prospectively measured sonographically in patients older than age 60 years. Longitudinal renal lengths (ARLs) were measured, and the RRLs were calculated by dividing the ARL by the body height. ARL and RRL measurements were analyzed according to sex, age, and body height.

RESULTS

The ARLs and RRLs of the left kidney in 236 patients were significantly greater than those of the right kidney (p < 0.05) in both sexes. The ARLs for both kidneys were also significantly greater in men than they were in women (p < 0.05). In contrast, the RRLs for both kidneys were significantly lower in men than they were in women (p < 0.05). Both left and right ARLs decreased significantly with increasing age regardless of sex (p < 0.01 and p < 0.05, respectively). The same was true for left and right RRLs (p < 0.01 and p < 0.05, respectively).

CONCLUSIONS

Renal size decreases with increasing age among patients older than 60 years. In our series of geriatric patients, the use of RRLs could not completely eliminate variations related to a subject's height, sex, and age. Therefore, we recommend that the ARL be used for renal measurements in geriatric patients.

Ultra-sonografia de características lineares e estimativas do volume de rins de cães

Obtiveram-se as medidas lineares de rins de cães adultos, clinicamente normais, por meio da ultra-sonografia, e estimou-se o volume dos rins de 35 cães (18 fêmeas e 17 machos) sem raça definida e com idade entre dois e seis anos. Os animais foram divididos em três grupos de acordo com o peso corporal (3,1 a 10,0 kg; 10,1 a 20,0 kg e 20,1 a 45,0 kg). Os planos de secção sagital, dorsal e transversal foram utilizados para obtenção das medidas lineares de comprimento (C), largura (L) e espessura (E). O volume renal foi calculado a partir das medidas lineares utilizando-se a fórmula para o volume de um elipsóide. Os valores médios encontrados para os três grupos foram, respectivamente: comprimento (4,73; 6,09 e 7,13cm), largura (2,81; 3,44 e 3,95cm), espessura (2,43; 3,00 e 3,58cm) e volume (17,98; 33,36 e 53,81cm³). As dimensões dos rins esquerdo e direito e de machos e fêmeas foram equivalentes. Observaram-se correlações positivas entre todas as medidas renais e peso corporal.

Renal volume measurements: accuracy and repeatability of US compared with that of MR imaging

PURPOSE

To determine the accuracy and repeatability of ultrasonography (US) with the ellipsoid formula in calculating the renal volume.

MATERIALS AND METHODS

The renal volumes in 20 volunteers aged 19-51 years were determined by using US with the ellipsoid formula and magnetic resonance (MR) imaging with the voxel-count method by two independent observers for each modality. The observers performed all measurements twice, with an interval between the first and second examinations. The voxel-count method was the reference standard. Repeatability was evaluated by calculating the SD of the difference (method of Bland and Altman).

RESULTS

Renal volume was underestimated with US by 45 mL (25%) on average. A comparable underestimation was found when the ellipsoid formula was applied to MR images. This indicates that the inaccuracy of US renal volume measurements (a) occurred because the kidney does not resemble an ellipsoid and (b) was not primarily related to the imaging modality. Intra- and interobserver variations in US volume measurements were poor; the SD of the difference was 21-32 mL. For comparison, the SD of the difference in reference-standard measurements was 5-10 mL.

CONCLUSION

Use of US with the ellipsoid formula is not appropriate for accurate and reproducible calculation of renal volume.

Kidney length in postoperative acute renal failure

PURPOSE

The aim of this study was to evaluate kidney length in patients with postoperative acute renal failure (PARF).

METHODS

The effect of PARF on renal size was prospectively studied in 76 patients with PARF and 40 healthy volunteers. Sonographic measurements of kidney length and the level of serum creatinine were obtained each day patients stayed in our surgical intensive care unit. These measurements were done once in volunteers. All study subjects were divided into groups on the basis of age, those younger than 65 years and those 65 years or older. Statistical analyses on the relation of renal size, age, and degree of PARF used the kidney length:body height ratio (KBR) and the peak serum creatinine level. Follow-up kidney length and creatinine measurements were done in 24 patients 1-5 years after they recovered from PARF.

RESULTS

Regardless of age, mean KBRs were significantly greater in patients than in healthy volunteers (< 65 years, p < 0.001; > or = 65 years, p = 0.008), with a negative correlation between KBR and patient age (r = -0.664; p < 0.001). A positive correlation was found between the KBR and the peak serum creatinine level in patients younger than 65 years (r = 0.543; p < 0.001); an insignificant negative correlation was found between these factors in patients 65 years or older (r = -0.264; p = 0.1). Follow-up on recovered patients showed that their KBRs were significantly lower than the values when patients had PARF (< 65 years, p < 0.001; > or = 65 years, p = 0.027).

CONCLUSIONS

PARF produces a sonographically measurable increase in renal size.

In vitro measurement of kidney size: comparison of ultrasonography and MRI

In this in vitro study, the accuracy and repeatability of magnetic resonance imaging (MRI) and ultrasound (US) in assessing renal length and volume were determined. US and MR images of 20 cadaver pig kidneys were obtained twice and evaluated by two observers for each modality. The fluid displacement method provided the "gold standard." Renal volumes were calculated from the US and MR images using the ellipsoid formula. Additional volume calculations after segmentation of the kidney on MR images were done using the voxel-count method. Volumes calculated with the ellipsoid formula resulted in an average of 24% underestimation (range 5%-48%) of the renal volume for both US and MRI. With the voxel-count method, no significant deviation from the true renal volume was encountered. Repeatability was also greatest with the voxel-count method. Measuring renal length, repeatability was, again, better with MRI compared to US. For reliable calculation of renal size in vitro, MRI with use of the voxel-count method is preferred.

Sonographic measurement of absolute and relative renal length in adults

PURPOSE

The aim of this study was to evaluate sonographically measured absolute and relative lengths of normal kidneys according to subject height, sex, and age.

METHODS

Real-time sonography was performed on 202 subjects. Measurements of longitudinal renal diameter represented absolute renal length. Relative renal length was calculated using the kidney length: body height ratio (KBR).

RESULTS

Statistical analyses were done on findings in 175 subjects without renal impairment (104 men and 71 women) whose ages ranged from 17 to 85 years (mean +/- SD, 46.3 +/- 17.1). The mean heights of the subjects were 176 +/- 7 cm for men and 167 +/- 6 cm for women. The left kidney was absolutely (mean +/-SD, 112 +/- 9 mm) and relatively (mean KBR +/- SD, 0.655 +/- 0.042) longer than the right kidney (absolute length, 110 +/- 8 mm; KBR, 0.641 +/- 0.038), regardless of sex (p < 0.01). The absolute renal length was significantly greater in men than in women for both kidneys (p < 0.01), but there was no significant difference between KBRs (p > 0.05). Renal length decreased with age, and the rate of decrease seemed to accelerate at 60 years and older. When height and age were included in the multivariate regression analysis, sex was not a significant predictor of kidney length.

CONCLUSIONS

Relative renal length better represents kidney size than absolute renal length because it eliminates sex and height differences.