In malnourished adolescent with anorexia nervosa, Cockroft-Gault formula is the most relevant formula to estimate renal function

Assessment of the renal function of patients with anorexia nervosa

BACKGROUND

A decreased glomerular filtration rate (GFR), estimated using creatinine (Cr- eGFR), is often found at the initial presentation of anorexia nervosa (AN). Its pathophysiology has been explained mainly by dehydration, and chronic hypokalemia is also thought to be a cause. However, because we have often experienced cases of AN with decreased Cr-eGFR without these conditions, we must consider different etiologies. The focus of this paper is on low free triiodothyronine (FT3) syndrome. We also discuss the utility of eGFR, estimated using cystatin-C (CysC-eGFR), for these patients.

METHODS

The data of 39 patients diagnosed with AN between January 2005 and December 2023 was available for study. The characteristics of patients at the lowest and highest body mass index standard deviation score (BMI-SDS) were examined. Data on the parameters Cr-eGFR, CysC-eGFR, dehydration markers, potassium (K), and hormonal data and BMI-SDS were assessed during the treatment course to evaluate the correlations in these parameters. Blood hematocrit, uric acid (UA), blood urine nitrogen (BUN) level, and urine specific gravity were adopted as dehydration markers; FT3, free thyroxine, thyroid stimulating hormone, and insulin-like growth factor were adopted as hormonal data. Cr-eGFR and simultaneously evaluated dehydration markers, K, or hormonal data were extracted and correlations associated with the changes in BMI-SDS were examined. Furthermore, Cr-eGFR and simultaneously assessed CysC-eGFR were compared.

RESULTS

When the BMI-SDS was at the lowest value, low-FT3 syndrome was shown. Severe hypokalemia was not found in our study. A linear relation was not found between Cr-eGFR and BMI-SDS. A statistically significant correlation was found between Cr-eGFR and FT3 (p = 0.0025). Among the dehydration markers, statistically significant correlations were found between Cr-eGFR and BUN or UA. The difference between Cr-eGFR and CysC-eGFR was prominent, and CysC-eGFR showed much higher values.

CONCLUSIONS

Our data indicates that low-FT3 syndrome and dehydration were related to the renal function of our patients with AN. Furthermore, our data suggest that caution is needed in the interpretation of kidney function evaluation when using CysC-eGFR in cases of AN.

Determinants and risk factors for renal damage: where do patients hospitalized for severe anorexia nervosa stand? A multi-center study

BACKGROUND

Although renal damage is increasingly reported among the most undernourished patients with Anorexia Nervosa (AN), it remains underestimated in current practice, and often associated with acute dehydration. The purpose of our study was to evaluate the frequency, the extent, and the risk factors of renal involvement among adolescents and adults hospitalized in specialized units for AN.

METHODS

In this multi-center study, 197 consecutive participants were included, aged 13-65, from 11 inpatient eating disorder psychiatric units. Information on the course of AN, clinical characteristics, biological data, and medication were collected.

RESULTS

At admission, mean BMI was 13.1 (± 1.6) kg/m2 for a mean age of 20.74 (± 6.5) years and the z-score was - 3.6 (± 1.33). Six participants (3.0%) had hyponatremia, four (2.0%) had hypokalemia, and nine (4.5%) had hypochloremia. The Blood Urea Nitrogen/Creatinine ratio was over 20 for 21 (10.6%) participants. The mean plasma creatinine was 65.22 (± 12.8) µmol/L, and the mean eGFR was 74.74 (± 18.9) ml/min. Thirty- five participants (17.8%) had an eGFR > 90 ml/min, 123 (62.4%) from 60 to 90 ml/min, 35 (17.8%) from 45 to 60 ml/min, and 4 (2%) under 45 ml/min. In multivariate analysis, only BMI on admission was a determinant of renal impairment. The lower the BMI the more severe was the renal impairment.

CONCLUSION

When eGFR is calculated, it highlights renal dysfunction found in severe AN requiring hospitalisation in specialized units. The severity of undernutrition is an independent associated factor. Kidney functionality tests using eGFR, in addition to creatinine alone, should be part of routine care for patients with AN to detect underlying renal dysfunction.

Renal and electrolyte complications in eating disorders: a comprehensive review

Eating disorders are psychiatric disorders with significant and widespread medical complications, including renal disorders. Renal disease is not uncommon in patients with eating disorders but is often unrecognized. It includes both acute renal injury and progression to chronic kidney disease requiring dialysis. Electrolyte abnormalities including hyponatremia, hypokalemia, and metabolic alkalosis are common in eating disorders and vary depending on whether patients engage in purging behaviors. Chronic hypokalemia due to purging in patients with anorexia nervosa-binge purge subtype or bulimia nervosa can lead to hypokalemic nephropathy and chronic kidney disease. Additional electrolyte derangements are seen during refeeding, including hypophosphatemia, hypokalemia, and hypomagnesemia. Patients can also develop Pseudo-Bartter's syndrome which leads to edema and rapid weight gain in patients who cease purging behavior. Clinicians and patients should be aware of these complications in order to provide education and early detection and prevention.

Risk of dialysis and renal diseases in patients with anorexia nervosa in Taiwan

OBJECTIVE

To investigate the incidence and risk of renal-related complications in a nationwide cohort of Taiwanese patients with anorexia nervosa (AN).

METHOD

This longitudinal cohort study analyzed the data of 43,951 individuals-comprising 2091 patients with AN and their controls matched (1:20) using propensity scores according to sex, age, degree of urbanization of residence, socioeconomic status, and year of diagnosis-from a population-based health insurance database; the study lasted 16 years. We used Kaplan-Meier curves to estimate the cumulative incidence of renal events. We also performed Cox proportional regression and constructed a risk model with death as a competing event (both adjusted for basic characteristics, renal diseases, and psychiatric comorbidities) to examine the risk of dialysis and renal outcomes in the AN group relative to the control group.

RESULTS

In total, 204 and 10 patients with AN had renal-related outcomes and end-stage renal disease (ESRD), respectively. The cumulative incidence rates of all renal outcomes and ESRD in the AN group were 10.72% and .64%, respectively, at 10-year follow-up. Compared with the control group, the AN group had a significantly higher risk of acute dialysis (adjusted hazard ratio 2.10 [95% confidence interval 1.19-3.68]), hypokalemia, hypovolemia, nephritis, acute renal failure, and chronic renal failure. The AN group did not have a significantly higher risk of ESRD.

DISCUSSION

The elevated risks of acute dialysis and some renal outcomes in AN highlight the importance of monitoring electrolyte imbalance and renal malfunctioning.

PUBLIC SIGNIFICANCE

Malnutrition and purging behaviors may cause renal complications in patients with AN. In this longitudinal cohort study, we found that the 10-year cumulative incidence of all renal outcomes in AN was 10.72%, and that patients with AN had a two-fold higher risk of overall renal outcomes compared with those without AN. Our findings imply that weight restoration and ceasing purging behaviors are crucial for recovery from AN.

Renal Function in Patients Hospitalized With Anorexia Nervosa Undergoing Refeeding: Findings From the Study of Refeeding to Optimize Inpatient Gains

PURPOSE

Among complications of malnutrition secondary to anorexia nervosa (AN) or atypical anorexia nervosa (AAN), renal impairment remains poorly elucidated. Evaluating renal function in hospitalized pediatric patients with AN and AAN undergoing refeeding will yield important information to guide clinicians in screening and managing renal dysfunction in this population.

METHODS

This is a secondary analysis of data from the Study of Refeeding to Optimize Inpatient Gains trial, a multicenter randomized clinical trial comparing higher calorie refeeding versus lower calorie refeeding in 120 adolescents and young adults hospitalized with medical instability secondary to AN or AAN. Baseline disease characteristics were obtained. Vital sign measurements, weight, electrolytes, and fluid status were evaluated daily to ascertain medical stability. Renal function on admission and throughout hospitalization was quantified using daily creatinine measurement and calculation of the estimated glomerular filtration rate (eGFR) using the modified Schwartz equation. Regression analysis and mixed linear models were utilized to evaluate factors associated with eGFR.

RESULTS

Of the 111 participants who completed treatment protocol, 33% had a baseline eGFR less than 90, suggesting renal impairment. Patients who experienced more rapid weight loss and more severe bradycardia were more likely to have low admission eGFR. While eGFR improved during refeeding, eGFR change by day based on refeeding treatment assignment did not reach statistical significance (95% confidence interval, -1.61, 0.15]; p = .095).

DISCUSSION

Renal impairment is evident on admission in a significant number of adolescents and young adults hospitalized with AN and AAN. We demonstrate that short-term medical refeeding yields improvement in renal function.

Renal dysfunctions and clinical correlates in adolescents with restrictive anorexia nervosa

BACKGROUND AND AIMS

The alteration of kidney function in adolescents with anorexia nervosa (AN) is a frequent, but still poorly investigated, consequence of AN. In this study, we analyzed glomerular filtration rate with the Cockroft-Gault formula in a group of 148 adolescents with Anorexia Nervosa and correlated it to clinical and biochemical data collected at admission.

METHODS

A retrospective study was conducted on 148 patients hospitalized from 2016 to 2019 for severe malnutrition due to restrictive AN. We measured glomerular filtration rate and correlated it with the patients' anamnestic history, nutritional status and biochemical data.

RESULTS

For the 148 AN patients, 40 (27%) resulted at admission at stage 1 of kidney damage (GFR>90 mL/min), 88 patients (59%) at stage 2 (GFR 89-60 mL/min), 17 patients (11%) at stage 3A (GFR 59-45 mL/min) and 3 patients (2%) at stage 3B (GFR 44-30 mL/min). Results outlined a correlation between the entity of kidney damage and BMI at admission and before illness onset, but not with the rapidity and entity of weight loss. Further, more severe renal damages corresponded to major biochemical and hormonal alterations.

CONCLUSIONS

Results of our study confirm that kidney damage is a frequent condition in adolescents with restrictive-type AN and support making kidney functionality tests part of routine care in patients with AN.