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The value of urodynamic studies

may then be taken both to achieve urinary, continence and to preserve upper tract function. The common surgical procedures carried out incluide bladder neck reconstruction, bladder augmentation, and the placement of the artificial urinary sphincter. Perioperative urodynamic studies in children undergoing such procedures are standard practice in most major centres. End stage renal disease in children requiring renal transplantation is associated with lower urinary tract obstruction in as many as 25%. Pretransplant urodynamics in these children will allow, if necessary, the construction of a urinary tract that will not prejudice renal function in the engrafted kidney.2021 Cystometry is indicated in children with reflux where bladder dysfunction is suspected, especially if reimplantation surgery is contemplated, as a relationship may exist between severe vesicoureteric reflux

and abnormal bladder activity.22 Cystometry and videocystometry are invasive studies, the latter involving exposure to radiation. Recent advances include the availability of extended night time cystometry,23 with so called physiological filling of the bladder with the patient's own urine.24 More recently ambulatory urodynamics involving a Holter type principle has permitted the recording of bladder pressure over many hours while the child goes about his or her normal activities.25 These studies provide a more sensitive index of lower urinary tract function than conventional cystometry and are of particular use in infants and younger children (such as those under the age of 5 years) who are often unable to cooperate with the more traditional techniques. Urodynamic studies in general, and cystometric investigations in particular, are fundamental to the initial and on-going management of many children with urological abnormalities, particularly those with neuropathic bladder dysfunction. The value of these studies in children depends on careful patient selection together with sympathetic management of the child during the study. MICHAEL D DINNEEN PATRICK G DUFFY

Urodynamics Unit, Department of Paediatric Urology, Hospitalfor Sick Children, Great Ormond Street, London WClN33H

1 Abrams PH, Blaivas JG, Stanton SL, Andersen JT. The standardisation of terminology of lower urinary tract function. Scand J Urol Nephrol 1988; 114: 5-19. 2 Koff SA. Guest editors notes. Dialogues in Pediatric Urology 1983; 6(8): 2. 3 Saxton HM. Urodynamics: the appropriate modality for the investigation of frequency, urgency, incontinence, and voiding difficulties. Radiology 1990; 175: 307-16. 4 Styles RA, Neal DE, Griffiths CJ, Ramsden PD. Long-term monitoring of bladder pressure in chronic retention of urine: the relationship between detrusor activity and upper tract dilatation. 7 Urol 1988; 140: 330-4. 5 Lissens M, Van de Walle JP, Vereecken R, Bruyninckx F, Rosselle N. Electromyography of the external anal sphincter muscle during urodynamic testing in children with meningomyelocele. Acta Belg Med Phys 1990; 13: 167-73. 6 Norgaard JP, Hansen JH, Nielsen JB, Rittig S, Djurhuus JC. Nocturnal studies in enuretics. A polygraphic study of sleep-EEG and bladder activity. Scand J Urol Nephrol 1989; 125 (suppl): 73-8. 7 Jarvelin MR, Huttunen NP, Seppanen J, Seppanen U, Moilanen I. Screening of urinary tract abnormalities among day and nightwetting children. Scand _J Urol Nephrol 1990: 24: 181-9. 8 Whiteside CG, Arnold EP. Persistent primary enuresis - a urodynamic assessment. BMJ 1975; i: 364-7. 9 Van Gool JD, Vijverberg MAW, de Jong TPVM. Functional daytime incontinence: clinical and urodynamic assessment. Scand Jf Urol Nephrol 1992; 141 (suppl): 58-69. 10 Van Gool JD, Vijverberg MA, Messer AP, Elzinga-Plomp A, de Jong TP. Functional daytime incontinence: non-pharmacological treatment. Scandj7 UrolNephrol 1992; 141 (suppl): 93-103. 11 Allen TD. Dysfunctional voiding. In: Retik AB, Cukier J, eds. Pediatric urology Baltimore: Williams and Wilkins, 1987: 228. 12 Mundy AR, Borzyskowski M, Saxton HM. Videourodynamic evaluation of neuropathic vesicourethral dysfunction in children. Br Jf Urol 1982; 54: 645-9. 13 Rudy DC, Woodside JR. The incontinent myelodysplastic patient. Urol Clin North Am 1991; 18: 295-308. 14 Perez LM, Khoury J, Webster GD. The value of urodynamic studies in infants less than 1 year old with congenital spinal dysraphism. Jf Urol 1992; 148: 584-7. 15 McGuire EJ, Woodside JR, Borden TA, Weiss RM. Prognostic value of urodynamic testing in myelodysplastic patients. Jf Urol 1981; 126: 205-9. 16 Bauer SB, Hallet M, Khoshbin S, et al. Predictive value of urodynamic evaluation in newborns with myelodysplasia. JAMA 1984; 252: 650-2. 17 Zoller G, Schoner W, Ringert RH. Pre- and postoperative urodynamic findings in children with tethered spinal cord syndrome. Eur Urol 1991; 19: 139-41. 18 Foster LS, Kogan BA, Cogen PH, Edwards MS. Bladder function in patients with lipomyelomeningocele. 7 Urol 1990; 143: 984-6. 19 Hollowell JG, Hill PD, Duffy PG, Ransley PG. Bladder function and dysfunction in bladder exstrophy and epispadias. Lancet 1991; 338: 926-8. 20 Burns MW, Watkins SL, Mitchell ME, Tapper D. Treatment of bladder dysfunction in children with end-stage renal disease. J Pediatr Surg 1992; 27: 170-4. 21 Dinneen MD, Fitzpatrick MM, Godley ML, et al. Renal transplantation in young boys with posterior urethral valves. A preliminary report. Br Jf Urol 1993 (in press). 22 Nielsen JB. Lower urinary tract function in vesicoureteral reflux. ScandJ7 Urol Nephrol 1989; 125 (suppl): 15-21. 23 McInerney PD, Harris SA, Pritchard A, Stephenson TP. Night studies for primary diurnal and nocturnal enuresis and preliminary results of the 'clam' ileocystoplasty. BrJ Urol 1991; 67: 42-3. 24 Passerini-Glazel G, Cisternino A, Artibani W, Pagano F. Ambulatory urodynamics: preliminary experience with vesicourethral holter in children. Scand _J Urol Nephrol 1992; 141 (suppl): 87-92. 25 McInerney PD, Vanner TF, Harris SA, Stephenson TP. Ambulatory urodynamics. BrJ Urol 1991; 67: 272-4.

Dietary management in nephrotic syndrome Nephrotic syndrome is characterised by heavy proteinuria, hypoalbuminaemia, and oedema with hyperlipidaemia.1 The majority of children with nephrotic syndrome have a steroid sensitive condition that is associated with minimal histological changes in the glomeruli (MCNS). The initial management involves the control of oedema and prevention of infection while awaiting the response to corticosteroids. If the child does respond to prednisolone with infrequent relapses, then there are likely to be a few long term dietary problems.2 However, children who frequently relapse and are steroid dependent may require long term dietary advice to monitor and maintain nutritional status and prevent obesity. Growth and endocrine function are important issues in the long term management of such patients.3

Initial advice Growth parameters should always be recorded and dry weight estimated, as surface area is used to calculate the prednisolone dosage. A dietitian should be involved in the initial management both to review the dietary history as well as advising on the practicalities of the moderate fluid restriction that is often required in the initial oedematous phase while awaiting the response to steroids. The basic advice is a 'healthy eating' diet for all the family. It should provide adequate energy based on the estimated average requirement for children of the same chronological age.4 A protein intake of 1-2 gfkg body weight/day should be adequate for most children. In the past diets containing increased intakes of protein (3-4 g/kg/body weight/day) were prescribed in the belief

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that they would help to restore serum protein pools.5 Animal studies, however, have shown that although dietary protein augmentation increased albumin synthesis it had no significant effect upon serum albumin concentrations or muscle protein as all of the additional ingested protein was catabolised to urea and excreted in the urine rather than used- to promote growth.6 Alternatively there have been concerns that high protein diets may accelerate the progression of human and experimental glomerulonephritis7 and therefore the use of low protein diets have also been recommended. Although these diets have been shown to decrease proteinuria, there is the possible risk of malnutrition as suggested by animal studies.8 Such diets are also impractical to follow. A 'no added salt' diet is advised when the child is oedematous and should ideally be followed as part of the general healthy eating advice in the long term. This can be done by omitting the addition of salt to food at the table and reducing the intake of highly salted manufactured foods, particularly snack foods such as crisps. Very low sodium diets and the use of low sodium specialist products should not be necessary. This advice can produce conflict within families and possible confusion. Follow up dietetic review in the clinic will help reinforce previous advice and help ensure that the diet is practical and not unnecessarily restrictive. The use of monounsaturated or polyunsaturated margarines and oils are also advocated as part of the general healthy eating gdvice with a reduction of a saturated fat intake. Attempts at dietary manipulation of lipids in the diet may be more relevant in the child with a chronic nephrotic state. A leaflet/booklet on healthy eating should be available to the family.

and catabolic state may require a period of nutritional support either with oral or nasogastric tube fed supplements. Vitamin supplementation and iron treatment may also be indicated."I Such children are often hospitalised for long periods and the clinical course may be complicated by diarrhoea and other nosocomial infections from the ward.

Weight control Prednisolone treatment undoubtedly stimulates the child's appetite and dietary advice about the prevention of excessive weight gain is important. Many children and their parents become upset with changes in body image, and this is particularly true with adolescents. In between meal snacks such as biscuits, crisps, and fizzy (high sugar) drinks should be avoided with low energy alternatives promoted. Healthy eating advice should again be reinforced. Occasionally contact with the nursery or school may be necessary as part of the psychosocial support required in some families.

ALAN R WATSON JANET E COLEMAN

Food allergy As the aetiology of MCNS is unknown, there are some parents who become concerned that dietary factors may be responsible especially as MCNS is commoner in atopic families. There are reports suggesting food hypersensitivity, particularly to milk and dairy products, may be aetiological factors in the glomerular damage in both young and adult patients.9 10 If a trial of a few foods diet is contemplated it should be under close dietetic supervision. One should be aware that some families may seek advice from alternative medicine sources, especially if they have concerns about the use of corticosteroids. Steroid resistant nephrotic syndrome This group of patients is usually very heterogenous with an underlying renal pathology that does not respond to at least four weeks of daily prednisolone treatment. Prolonged initial steroid dosage combined with oedema, 'anorexia',

Hyperlipidaemia The management of hyperlipidaemia is controversial and could be of some importance if the nephrotic state is prolonged. 12 The manipulation of dietary fat intake has a limited effect in reducing serum lipids and current interest is focused on the use of lipid lowering agents such as simvastatin. 3 Although not currently licensed for children, we have maintained five patients with chronic nephrosis on dosages of 10 to 20 mg of simvastatin daily for up to three years with significant lowering of serum cholesterol concentrations and no obvious side effects. -

Congenital nephrotic syndrome This is a rare condition that in the past was associated with failure to thrive, progressive renal failure, and eventual death.'4 If such patients are to survive they require intensive dietetic support because of the anorexia that is complicated by fluid restriction. A protein intake of 2-4 kglbody weight/day with maximum energy intake within the fluid allowance may be indicated. Nutritional supplements will be essential to achieve nutritional requirements and administration by the nasogastric or preferably gastrostomy route will be indicated should the child fail to meet their nutritional requirements orally. '5The losses of protein can be reduced by unilaterial or bilateral nephrectomy combined with early dialysis and transplantation.'6 Paediatric Renal Unit, City Hospital Trust, Hucknall Road, Nottingham NG5 IPB I Watson AR. Nephrotic syndrome. In: Campbell AGM, McIntosh N, eds.

Forfar and Arneils textbook of paediatrics. 4th Ed. Edinburgh: Churchill Livingstone, 1992: 1057-61. 2 Haycock GB. Renal disease. In: McLaren DS, Burman D, Belton NR, Williams AF, eds. Textbook of paediatric nutrition. 3rd Ed. Edinburgh: Churchill Livingstone, 1991: 238-40. 3 Rees L, Greene SA, Adlard P, et al. Growth and endocrine function in steroid sensitive nephrotic syndrome. Arch Dis Child 1988; 63: 484-90. 4 Committee on Medical Aspects of Food Policy, Department of Health. Dietary reference values for food energy and nutrients for the United Kingdom. London: HMSO, 1991. 5 Blainey JD. High protein diets in the treatment of the nephrotic syndrome. Clin Sci 1954; 13: 567-81. 6 Al-Bander H, Kayser GA. Ineffectiveness of dietary protein augmentation in the management of nephrotic syndrome. Pediatr Nephrol 1991; 5: 482-6. 7 Brenner BM, Mayer TW, Hostetter TH. Dietary protein intake and the progressive nature of kidney disease. N Engl J Med 1982; 302: 652-9. 8 Feehally J, Baker F, Walls J. Dietary manipulation in experimental nephrotic syndrome. Nephron 1988; 50: 247-52. 9 Genova R, Sanfilippo M, Rossi ME, Vierucci A. Food allergy in steroid resistant nephrotic syndrome. Lancet 1987; i: 1315-6. 10 Lagrue G, Laurent J, Rostoker G, Lang D. Food allergy in idiopathic nephrotic syndrome. Lancet 1987; ii: 277. 11 Strauss J, Zillerueb G, Freundlich M, Abitol C. Less commonly recognised features of childhood nephrotic syndrome. In: Gruskin AB, ed. Pediatr Clin North Am 1987; 34: 591-607. 12 Grundy SM, Vega GL. Rationale and management of hyperlipidaemia of the nephrotic syndrome. Am J Med 1989; 87: 3-11. 13 Rabelink AJ, Hene RJ, Erkelens DW. Effects of simvastatin and cholestyramine on lipoprotein profile in hyperlipidaemia of nephrotic syndrome. Lancet 1988; ii: 1335-8. 14 Rapola J, Huttenen NP, Hallman N. Congenital and infantile nephrotic syndrome. In: Edelman CM, eds. Pediatric kidney disease. 2nd Ed. Boston: Little Brown, 1992: 1291 -305. 15 Coleman JE, Watson AR. Gastrostomy buttons: the optimal route for nutritional support in children with chronic renal failure. J Renal Nutrition 1992; 2 (suppl 1): 21-6. 16 Mahan JD, Mauer SM, Sibley RK, Vernier RL. Congenital nephrotic syndrome: evolution of medical management and results of renal transplantation. _Pediatr 1984; 105: 549-57.