Renal function of children receiving long-term parenteral nutrition

Nutrition and Intestinal Rehabilitation of Children With Short Bowel Syndrome: A Position Paper of the ESPGHAN Committee on Nutrition. Part 2: Long-Term Follow-Up on Home Parenteral Nutrition

Short bowel syndrome (SBS) is the leading cause of intestinal failure (IF) in children. The preferred treatment for IF is parenteral nutrition which may be required until adulthood. The aim of this position paper is to review the available evidence on managing SBS and to provide practical guidance to clinicians dealing with this condition. All members of the Nutrition Committee of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) contributed to this position paper. Some renowned experts in the field joined the team to guide with their expertise. A systematic literature search was performed from 2005 to May 2021 using PubMed, MEDLINE, and Cochrane Database of Systematic Reviews. In the absence of evidence, recommendations reflect the expert opinion of the authors. Literature on SBS mainly consists of retrospective single-center experience, thus most of the current papers and recommendations are based on expert opinion. All recommendations were voted on by the expert panel and reached >90% agreement. This second part of the position paper is dedicated to the long-term management of children with SBS-IF. The paper mainly focuses on how to achieve intestinal rehabilitation, treatment of complications, and on possible surgical and medical management to increase intestinal absorption.

Frequency and impact of enteric hyperoxaluria in pediatric short bowel syndrome: a retrospective single centre study

Objectives

The survival of pediatric patients with short bowel syndrome has improved in recent years. Enteric hyperoxaluria as a pathophysiological consequence has been hardly addressed so far. It can be associated with nephrolithiasis, nephrocalcinosis or even renal insufficiency. We assessed the prevalence of hyperoxaluria and its pathogenic consequences in a retrospective single centre study over the last 12 years.

Methods

We conducted an internal database search for all pediatric patients suffering from short bowel syndrome treated from 2010 to 2022 in the department of pediatric gastroenterology as well as the pediatric nephrology and dialysis unit. Out of 56 patients identified, 26 patients were analysed for etiology of short bowel syndrome, renal excretion of oxalate (24/26), remaining short bowel and large intestinal length as well as further clinical parameters such as eGFR, nephrocalcinosis/urinary stone formation or stool frequency.

Results

Hyperoxaluria was detected in 14/26 patients (54%). Nephrocalcinosis was present in four patients. Out of these four patients, hyperoxaluria could be proven (21% of all hyperoxaluric patients) in three cases, one hyperoxaluric patient had nephrolithiasis (7%). In one patient hyperoxaluria lead to end stage renal disease. We found that 80% of patients with volvulus developed enteric hyperoxaluria. None of the investigated factors had an effect on oxalate excretion.

Conclusion

Enteric hyperoxaluria is a relevant pathophysiological finding in patients with short bowel syndrome occurring in about 50% of our cohort with multiple pathogenic complications. Regular screening for hyperoxaluria may be implemented in medical care for patients with short bowel syndrome. If necessary, prophylaxis, e.g., dietary advice or metaphylaxis should be initiated.

Intestinal adaptation and rehabilitation

Massive intestinal resection is a regrettably necessary but life-saving intervention for progressive or fulminant necrotizing enterocolitis (NEC). However, the resultant short bowel syndrome (SBS) poses its own array of challenges and complications. Within hours of such an abrupt loss of intestinal length, the intestine begins to adapt. Our ability to understand this process of intestinal adaptation has proven critical in our ability to clinically treat the challenging problem of short bowel syndrome. This review first highlights key data relating to intestinal adaptation including structural and functional changes, biochemical regulation, and other factors affecting the magnitude of intestinal adaptation responses. We then focus on intestinal rehabilitation as it relates to strategies to enhance intestinal adaptation while meeting nutritional needs and preventing complications of parenteral nutrition.

Intestinal failure among adults and children: Similarities and differences

Intestinal failure (IF) is a complex medical condition that is caused by a constellation of disorders, resulting in the gut's inability to adequately absorb fluids and nutrients to sustain hydration, growth, and survival, thereby requiring the use of parenteral fluid and/or nutrition. Significant advancements in intestinal rehabilitation have resulted in improved survival rates for individuals with IF. There are distinct differences, however, related to etiology, adaptive potential and complications, and medical and surgical management when comparing children with adults. The purpose of this review is to contrast the similarities and differences between these two distinct groups and provide insight for future directions, as a growing population of pediatric patients will cross into the adult world for IF management.

Management of pediatric intestinal failure related to short bowel syndrome

Intestinal failure (IF) secondary to short bowel syndrome is a challenging and complex medical condition with significant risk for surgical and medical complications. Significant advancements in the care of this patient population have led to improved survival rates. Due to their intensive medical needs children with IF are at risk for long-term complications that require comprehensive management and close monitoring. The purpose of this paper is to review the available literature emphasizing the surgical aspects of care for children with IF secondary to short bowel syndrome. A key priority in the surgical care of this patient population includes strategies to preserve available bowel and maximize its function. Utilization of novel surgical techniques and autologous bowel reconstruction can have a significant impact on children with IF secondary to short bowel syndrome related to the function of their bowel and ability to achieve enteral autonomy. It is also important to understand the potential long-term complications to ensure strategies are put in place to mitigate risk with early detection to improve long-term outcomes.

Children with Intestinal Failure Maintain Their Renal Function on Long-Term Parenteral Nutrition

BACKGROUND

Long-term parenteral nutrition (PN) has been associated with renal complications, including hypercalciuria, nephrocalcinosis, proteinuria and reduced glomerular filtration rate (GFR). Pediatric data are scarce and mostly short-term. Our study aimed to evaluate renal complications in children with intestinal failure (IF) receiving long-term PN.

METHODS

A cross-sectional study was performed in a tertiary pediatric IF clinic of patients receiving home-PN treatment for more than 1 year. Data regarding medical background, anthropometrics, laboratory investigations and abdominal sonography were retrieved.

RESULTS

Complete data were available for 15 children (67% males), with a median age of 6 (range 1.5-15) years and a median (IQR) PN duration of 4 (1.5-6) years. Low-grade proteinuria was identified in 61% and microalbuminuria in 30% of the cohort. Hypercalciuria and hyperoxaluria were present in 50% and 46%, respectively. One patient had nephrocalcinosis. The estimated GFR was normal in all but one patient who had pre-existing kidney disease.

CONCLUSIONS

Pediatric IF patients can present with preserved kidney function after years of PN treatment. Despite the high prevalence of hypercalciuria, nephrocalcinosis was not common. Base line and long-term monitoring of various aspects of renal function would be essential to characterize the effects of prolonged PN on kidney functions in pediatric patients.

Combined use of creatinine and cystatin C improves the detection of renal dysfunction in children undergoing home parenteral nutrition

BACKGROUND

Renal dysfunction can complicate home parenteral nutrition (HPN). The aims were, in the context of pediatric HPN, to assess renal function using the measured glomerular filtration rate (mGFR), determine the most accurate formula(s) to estimate GFR, and identify possible underlying mechanisms of renal impairment.

METHODS

A retrospective study was performed in 2 centers. Patients receiving HPN and aged 2-16 years without medical history of nephropathy were included. GFR was measured using iohexol clearance. Estimated GFR (eGFR) was calculated using creatinine, cystatin C-based, and combined (eGFR_cr+cyst ) Schwartz formulas.

RESULTS

A total of 36 patients (18 females) were included; they received HPN for 8 (2-16) years. The primary digestive disease was short-bowel syndrome for 16 (44%) patients, gastrointestinal motility disorder for 10 (28%), or congenital diarrhea for 10 (28%). The median (range) mGFR was 99 (33-136) ml/min/1.73 m² ; 9 (25%) patients had mildly decreased mGFR (<90 and ≥60 ml/min/1.73 m² ), and 2 (6%) had mildly to severely decreased mGFR (<60 ml/min/1.73 m² ). The eGFR_cr+cyst formula was the most accurate and precise to estimate GFR. A significant negative correlation between mGFR and PN duration was found for patients receiving PN for 6-7/7 days (P = .008). Activation of the renin-angiotensin system was identified in 15 of 36 (42%) patients.

CONCLUSION

Renal dysfunction was frequent and correlated with the duration of PN only for patients with the most severe intestinal failure. The use of eGFR_cr+cyst improves its detection in these patients. Chronic dehydration may be an underlying mechanism.

Evolution of renal function in patients with severe intestinal failure on home parenteral nutrition

BACKGROUND

Kidney disease is a frequent but underestimated complication in patients suffering from intestinal failure (IF) treated by long-term home parenteral nutrition (HPN). The evolution in glomerular filtration rate (GFR) over time is poorly characterized. The current equations for estimating GFR have limited precision. No study has specifically investigated the reliability of recent creatinine-based estimated GFR (eGFR) equations in this population. The aim of this study was to evaluate the renal function decline under home parenteral nutrition (HPN) with a gold standard method and compare the performances of routinely used eGFR equations.

METHODS

Forty patients with HPN and two or more GFR measurements were retrospectively studied. The renal function decline was calculated by the slope drawn between the successive measured GFRs (mGFRs). The performances of the Modification of Diet in Renal Disease, Chronic Kidney Disease Epidemiology Collaboration, full age spectrum and revised Lund-Malmö equations were compared with reference methods (inulin or iohexol clearance).

RESULTS

The mean mGFR was 78 ± 28 mL/min/1.73 m2. The annual decline of mGFR was -1.9 mL/min/1.73 m2/year. No predisposing factor was identified to predict impairment in renal function. eGFR formulas grossly overestimated mGFR and had a low level of accuracy.

CONCLUSIONS

Patients with IF are at significant risk for impaired renal function. In this population, the tested eGFR equations were inaccurate. However, monitoring kidney function with mGFR remains important in these patients, as their GFR regularly declines and no specific risk factor has yet been identified.

Nephrocalcinosis and Renal Dysfunction in Pediatric Intestinal Failure

BACKGROUND

Outcomes of pediatric intestinal failure (PIF) have improved recently, with other comorbidities, such as increased echogenicity/nephrocalcinosis on ultrasound (US) in long-term survivors now evident. We evaluated the significance of nephrocalcinosis over time in PIF and its impact on renal function.

METHODS

Retrospective analysis on a cohort of PIF patients was performed. Presence of nephrocalcinosis and/or increased renal echogenicity (identified on US), estimated glomerular filtration rate (eGFR; ml · min · 1.73 m2), renal tubular function, PN volume (ml · kg · day) and PN exposure time (hours/day) were reviewed annually over a follow-up period of 2 years. Outcomes in the nephrocalcinosis versus normal US groups were compared.

RESULTS

Forty patients (28 boys, median age 2.7 years) were followed for 2 years. Fifteen (38%) had either increased echogenicity or nephrocalcinosis (group 1) at initial US. US were normal in the remaining 25 (62%) on initial assessment (group 2). eGFR did not differ between group 1 and group 2 at baseline (118 vs 133, P = 0.51) and year 2 (130 vs 131, P = 1.00). The percentage of patients with abnormal markers of tubular function was similar in both groups at year 2 (high urine calcium: creatinine 33 versus 30, P = 0.83; high urine calcium: citrate 39 versus 42, P = 0.87; low urine citrate: creatinine 15 versus 17, P = 1.00; high urine oxalate: creatinine 39 versus 25, P = 0.77).

CONCLUSIONS

A large proportion of PIF patients with a history of parenteral nutrition (PN) exposure have nephrocalcinosis and/or increased echogenicity on US. Over a 2-year follow-up period, however, these abnormalities had no impact on eGFR or renal tubular function.

Monitoring of long-term parenteral nutrition in children with intestinal failure

Pediatric intestinal failure (IF) is a rare and complex condition associated with significant morbidity and mortality. It is defined as the reduction of gut mass or function below the minimal needed for absorption of nutrients and fluid to sustain life and growth. Since the advent of specialized multidisciplinary intestinal rehabilitation centers, IF management has considerably evolved in the last years, but serious complications of long-term parenteral nutrition (PN) can occur. Main complications include intestinal failure-associated liver disease, growth failure, body composition imbalance, central venous access complications, micronutrient deficiencies and toxicities, metabolic bone disease, small intestinal bacterial overgrowth, and renal disease. With improvement in survival rates of patients over the last 20 years, emphasis should be on limiting IF-related comorbidities and improving quality of life. Close monitoring is pivotal to ensuring quality of care of these patients. The care of children with chronic IF should involve a comprehensive monitoring plan with flexibility for individualization according to specific patient needs. Monitoring of children on long-term PN varies significantly across units and is mainly based on experience, although few guidelines exist. This narrative review summarizes the current knowledge and practices related to monitoring of children with IF. The authors also share their 20-year experience at the Royal Children's Hospital in Melbourne Australia on this topic.

Renal Function in Children on Long Term Home Parenteral Nutrition

Objectives: To assess renal function in pediatric intestinal failure (IF) patients on long term home parenteral nutrition (HPN). Methods: Children who received HPN for a minimum of 3 years between 2007 and 2017 were identified from the IF clinic of a large tertiary referral center. Estimated glomerular filtration rate (eGFR) was calculated using the Schwartz formula at discharge on HPN, after 6 months, 1, 2, and 3 years. Results: Twenty five patients (40% male) fulfilled the inclusion criteria. The indications for HPN were due to an underlying motility disorder in 56% (14/25), enteropathy in 24% (6/25), and short bowel syndrome in 20% (5/25). At the start of HPN 80% (20/25) had a normal eGFR. Four children (17%) had an abnormal eGFR. In the group of patients with normal eGFR at the start of HPN 30% (6/20) had at least one episode of decreased eGFR in the following 3 years, however there was no significant decline in eGFR at the end of the 3 year study period. Overall there was no statistically significant deterioration of eGFR in the study population (p = 0.7898). Conclusion: In our cohort of children on long term HPN no significant decline of eGFR could be demonstrated within 3 years of starting PN.

Etiology and prognosis of pediatric short bowel syndrome

Pediatric intestinal failure is a complex and devastating condition defined as the inability of the intestine to absorb an adequate amount of fluid and nutrients to sustain life. The primary goal of intestinal failure treatment is to achieve enteral autonomy with a customized treatment plan. Although recent improvements in intestinal failure patient care have led to significant improvements in the morbidity and mortality rate, children with intestinal failure are at risk for multiple complications such as intestinal failure associated liver disease, recurrent septic episodes, central line complications, metabolic bone disease, impaired kidney function, and failure to thrive. In this article, we review the current literature on the etiology and factors affecting prognosis of pediatric IF.

High Incidence of Proteinuria in Children With Chronic Intestinal Failure Under Long-term Parenteral Nutrition

Long-term home parenteral nutrition (LTPN) in children with chronic intestinal failure (CIF) is associated with renal complications such as fluid and electrolyte imbalances, nephrocalcinosis, nephrolithiasis, and chronic kidney disease (CKD). The etiology of CIF-associated nephropathy is multifactorial. The aim of this study was to evaluate renal involvement under LTPN. In this study, 50 patients with CIF, median age 4.2 years (1.4-9.3; 23 girls) were included. Kidney involvement was a frequent finding in this study. CKD was present in 30% of patients without correlation with LTPN duration. Glomerular proteinuria was found in the majority of patients (76%), an important long-term risk factor for the progression of CKD. Increased urinary α-1 microglobulin was significantly associated with duration (years) of LTPN and was increased in patients with CKD.

Parenteral Nutrition: Indications, Access, and Complications

Parenteral nutrition (PN) is a life-sustaining therapy in patients with intestinal failure who are unable to tolerate enteral feedings. Patient selection should be based on a thorough assessment to identify those at high nutrition risk based on both disease severity and nutritional status. This article reviews both the acute and chronic indications for PN as well as special formulation consideration in specific disease states, vascular access, and complications of both short-term and long-term PN.

Long-term outcomes of pediatric intestinal failure

Management of pediatric intestinal failure has evolved in recent decades, with improved survival since the advent of specialized multidisciplinary intestinal failure centers. Though sepsis and intestinal failure associated liver disease still contribute to mortality, we now have growing data on the long-term outcomes for this population. While intestinal adaptation and parenteral nutrition weaning is most rapid during the first year on parenteral support, achievement of enteral autonomy is possible even after many years as energy and protein requirements decline dramatically with age. Intestinal transplant is an option for patients experiencing complications of long-term parenteral nutrition who are expected to have permanent intestinal failure, but outcomes are hindered by immunosuppression-related complications. Much of the available data comes from single center retrospective reports, with variable inclusion criteria, intestinal failure definitions, and follow-up durations; this limits the ability to analyze outcomes and identify best practices. As most children now survive long-term, the focus of management has shifted to the avoidance and management of comorbidities, support of normal growth and development, and optimization of quality of life for these medically and surgically complex patients.

Prevalence of renal abnormality in pediatric intestinal failure

BACKGROUND

Outcomes of children with intestinal failure have improved over the last decade. However, with improved survival, other co-morbidities have become evident. The goal of our study was to evaluate the presence of renal nephrocalcinosis or increased echogenicity in a cohort of patients with pediatric intestinal failure (PIF).

METHODS

A cross-sectional prevalence design was performed in PIF patients followed by our intestinal rehabilitation program between 2013 and 2014. Renal function was evaluated using serum creatinine and urea, urine oxalate, creatinine, calcium, and calcium/creatinine ratios. Renal ultrasounds were performed to assess for echogenicity. Data was collected on intestinal failure related factors and nutritional intake. Data was analyzed using medians and Mann-Whitney U or proportions and chi square.

RESULTS

Fifty-four patients (median age 48months; 33 males (61%) were studied. Twenty-two patients (41%) had increased echogenicity or nephrocalcinosis on ultrasound. There were no differences in serum Creatinine or urea, but patients with nephrocalcinosis had statistically different calcium:creatinine ratio (1.69 vs 0.74; p=0.043), urine oxalate (108 vs 219; p=0.06), and serum phosphate (1.55 vs 1.75; p=0.044). Patients with echogenicity had a shorter colonic remnant (25cm vs 31cm; p=0.01), a history of longer PN exposure (928 vs 483days; p=0.05), percent PN calories (37 vs 0; p=0.05), PN h/day (13 vs 0; p=0.05), but no difference in PN Ca/phosphate/magnesium content (mmol/kg).

CONCLUSION

A large proportion of PIF patients have increased echogenicity/nephrocalcinosis on ultrasound that is associated with prolonged PN exposure. This has implications for long-term management. Regular surveillance is required, and further study is warranted to determine specific risk factors.

Renal consequences of parenteral nutrition

Parenteral nutrition (PN) can be described as the "Intravenous administration of nutrients necessary to sustain life in those who would otherwise have died or suffered serious disease". PN is indicated in children who cannot be fully fed by the oral or intestinal route, usually as a result of intestinal failure. Intradialytic parenteral nutrition (IDPN) is rarely indicated in children on dialysis and does not confer a benefit over enteral supplements in the compliant patient with adequate intestinal function. Renal and metabolic consequences of PN are potentially life-threatening and include disorders of glucose homeostasis, acid-base and fluid and electrolyte disturbances, nephrolithiasis, impaired renal function and metabolic bone disease. Many of these complications are avoidable. Adequate clinical and biochemical assessment and monitoring of children receiving PN by a multidisciplinary nutrition support team is recommended to mitigate against the risks of these complications.

MYO5B mutations in patients with microvillus inclusion disease presenting with transient renal Fanconi syndrome

BACKGROUND AND OBJECTIVE

: Microvillus inclusion disease (MVID) is a rare congenital enteropathy associated with brush border atrophy and reduced expression of enzymes at the enterocytes' apical surface. MVID is associated with mutations in the MYO5B gene, which is expressed in all epithelial tissues. Whether organs other than the intestine are affected in MVID is unclear. We report 2 patients with MVID that developed renal Fanconi syndrome while receiving total parenteral nutrition. Renal Fanconi syndrome has been correlated to apical plasma membrane defects in kidney proximal tubular epithelial cells. The aim of the present study was to determine whether MYO5B mutations in these patients correlate with similar apical plasma membrane defects in renal tubular epithelial cells as observed in the intestine.

METHODS

: Biopsies from kidney, duodenum, ileum, jejunum, and colon of 2 patients with MVID carrying MYO5B mutations and of age-matched controls were fixed in paraffin and analyzed with immunohistochemistry and transmission electron microscopy.

RESULTS

: Structural defects of the brush border and apical recycling endosome organization are observed in enterocytes of all of the segments of the small intestine and colon. MYO5B mutations in patients with MVID with renal Fanconi syndrome do not correlate with aberrant apical plasma membrane morphology or altered apical recycling endosome organization in renal tubular epithelial cells.

CONCLUSIONS

: MYO5B mutations have divergent effects on the apical membrane system in kidney and intestinal epithelial cells. Epithelial defects presented in MVID are therefore likely triggered by intestine-specific factors, the identification of which may provide new targets and open avenues for the development of alternative therapeutic strategies to combat this devastating disease.

Complications of parenteral nutrition

Parenteral nutrition plays a vital role for patients with intestinal failure and those who are unable to maintain oral or enteral nutrition alone. Parenteral nutrition has been shown to improve clinical outcome in patients with malnutrition and intestinal tract dysfunction. The use of parenteral nutrition is not without risk of serious complications. Parenteral nutrition complications can be divided into mechanical related to vascular access, septic, and metabolic. This article provides a review on the short- and long-term complications of parenteral nutrition and their management.

Organ heavy-metal accumulation during parenteral nutrition is associated with pathologic abnormalities in rats

OBJECTIVES

Metabolic bone disease, hepatic abnormalities, splenic insufficiency, and nephropathy have been associated with long-term total parenteral nutrition (TPN). We determined the heavy-metal contamination in TPN solutions and investigated whether it was associated with organ deposition and pathologic organ damage.

METHODS

Five representative TPN solutions (two adult standard solutions, one renal solution, and one standard pediatric solution to reflect clinical practice) and 28 TPN components were analyzed with inductively coupled plasma mass spectrometry. Twenty-six male Fisher 344 rats were assigned to two groups (chow/NaCl = 8 and TPN = 18). TPN or NaCl was infused at a rate of 50 mL/d. After 14 d, serum, femurs, spine, liver, kidneys, brain, spleen, and testes were analyzed for heavy-metal deposition by using inductively coupled plasma mass spectrometry. Tissues were fixed in formalin, sectioned, and stained with hematoxylin and eosin, periodic acid Schiff, and Masson's trichrome stain. Kidneys were fixed in gluteraldehyde for ultrastructural examination with scanning electron microscopy.

RESULTS

The predominant sources of contaminants in TPN were amino acids (Al, As, Cr, Ge, Pb, Sn), dextrose (As, Ba, Cr, Sn), Ca gluconate (Al), K2PO4 (Al), lipid emulsion (As, Sn), and vitamins (As). Significant variations in the level of contamination depended on TPN formulation and brand of constituents. In the kidney, Pb, Cr, and Mn concentrations were greater than in controls, although there was no correlation with serum creatinine. Hepatic Cr and Pb concentrations were greater in TPN rats, although there was no correlation with serum aspartate aminotransferase or total bilirubin. Splenic Ba, Cr, Ge, Pb, Mn, and Sn concentrations were greater in TPN rats. Only serum Cr concentration was significantly correlated with splenic concentration (r = 0.46, P = 0.04). Brain and serum Ba concentrations were significantly correlated (r = 0.60, P = 0.007). No significant correlations were observed between any other metal in serum and that metal's respective organ concentration. No increase in heavy-metal accumulation was seen in the femur, spine, or testis. There were no significant depositions of As, Cd, Hg, St, or V in any of the organs examined. Serum Al and Cr concentrations were significantly increased in TPN rats, although there was no correlation with tissue concentrations. No significant increases in heavy-metal concentrations in tissue or plasma were observed for any of the other metals measurable by inductively coupled plasma mass spectrometry. Histologically in the TPN group, 50% of the rats had mild to moderate hepatic steatosis and 33% to 50% developed renal morphologic abnormalities; brains and spleens remained histologically normal.

CONCLUSIONS

We found significant heavy-metal contamination of TPN solutions, and this contamination can lead to organ deposition and subsequent histologic abnormalities.

Complications of long-term home total parenteral nutrition: their identification, prevention and treatment

The purpose of this review is to describe the most common complications of home total parenteral nutrition, their identification, treatment and prevention. Data sources were manuscripts and abstracts published in the English literature since 1968. Studies were selected for summarization in this review on the basis of clinical relevance to the practicing clinician. Home total parenteral nutrition is a relatively safe, life-saving method for nutrient delivery in patients with compromised gastrointestinal function. However, numerous complications, with associated morbidity and mortality, involving the delivery system and the gastrointestinal, renal, and skeletal systems may develop. Catheter-related complications are often preventable and treatable when they occur, although renal and bone abnormalities have elusive etiologies.

Renal function and urinary excretion of electrolytes in patients receiving cyclic parenteral nutrition

BACKGROUND

Long-term parenteral nutrition (LTPN) has been shown to induce renal impairment and bone demineralization. However, the mechanism of both injuries has not been clarified.

METHODS

This prospective study was performed in 16 patients with short bowel syndrome, aged 28 to 63 years, who had received LTPN for 31 +/- 7 months. Urinary excretion of electrolytes were measured before (diurnal, 12 hours) and during (nocturnal, 12 hours) parenteral nutrition. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured in the morning after the nutritional bag supply.

RESULTS

Mean GFR was 86 +/- 7 mL/min/1.73 m2 and ERPF was 412 +/- 31 mL/min/1.73 m2. Decreased GFR was present in 9 patients. There was no relation between renal function and age or the duration of LTPN. Urine volume and excretion of urea, creatinine, sodium, magnesium, and phosphate but not potassium increased significantly in nocturnal urine compared with diurnal urine. On the basis on 24-hour calciuria, 7 patients were normocalciuric (NCa) whereas 9 were hypercalciuric (HCa). Both had excessive nocturnal calciuria, but only the HCa group had diurnal hypercalciuria, the calcium supply being identical. Bone mineral density (BMD) was slightly, although not significantly, higher in NCa group, but in all patients BMD correlated significantly with calciuria. Serum parathyroid hormone and vitamin D were not different in the two groups.

CONCLUSIONS

In patients receiving LTPN, renal function is frequently impaired, by a mechanism which remains unclear. In nocturnal cyclic mode of nutrition, urinary volume and electrolyte excretion occurred predominantly during the infusion, but some patients have diurnal hypercalciuria. In these patients a defect in renal calcium reabsorption or more likely the inability of bone to retain the infused calcium may be responsible for bone demineralization.

Excessive urinary oxalate excretion occurs in long-term TPN patients both with and without ileostomies

OBJECTIVE

To determine if excessive oxalate and deficient citrate excretion were associated with TPN-associated nephropathy.

DESIGN

Crossectional cohort.

SETTING

Outpatient clinic.

SUBJECTS

Twenty-five patients (15 males, 10 females) aged 51 +/- 17 (mean +/- SD) years who had received home total parenteral nutrition (TPN) for 10 +/- 4 years. Fifteen subjects had ileostomies (Group A) and 10 had functional colons (Group B).

OUTCOME MEASURES

Glomerular filtration rate (GFR), tubular reabsorption of phosphate (TRP), urinary oxalate and citrate excretion.

RESULTS

The mean GFR was 68.1 +/- 34.5 ml/minute/1.73 m2 and did not differ between Groups A and B. The mean TRP was 65.0 +/- 32.2% for Group A and 80.5 +/- 16.0% for Group B. The difference was not statistically significant. Urinary oxalate and citrate excretion were 40.2 +/- 30.2 and 324.4 +/- 239.0 mg/day respectively for Group A, and 63.2 +/- 34.2 and 474.8 +/- 936.3 respectively for Group B. The differences were not statistically significant. Thirty-eight percent (38%) of patients with ileostomies and 78% of patients without ileostomies had excessive urinary oxalate excretion (> 40 mg/day). Fifteen percent (15%) of patients with ileostomies and 50% of patients without ileostomies had decreased urinary citrate excretion (< 140 mg/day).

CONCLUSIONS

Increased endogenous oxalate production may occur in patients receiving long-term TPN.