Alterations of Renal and Urinary Tract Function in Children Chapter 37 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier.

Alterations of Renal and Urinary Alterations of Renal and Urinary Tract Function in ChildrenTract Function in Children

Chapter 37Chapter 37

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Development of the Development of the Urinary Renal SystemUrinary Renal System

PronephrosPronephros MesonephrosMesonephros MetanephrosMetanephros

Ureteric budUreteric bud Metanephrogenic blastemaMetanephrogenic blastema

Urine formation and excretion begin by the Urine formation and excretion begin by the third month of gestationthird month of gestation

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Fluid and Electrolyte BalanceFluid and Electrolyte Balance Blood flow to the kidney in a newborn is Blood flow to the kidney in a newborn is

primarily to the medullary nephronsprimarily to the medullary nephrons Because of short loops of Henle in the Because of short loops of Henle in the

medullary nephrons, an infant produces more medullary nephrons, an infant produces more dilute urinedilute urine

Infants are in a high anabolic state, so their Infants are in a high anabolic state, so their urea excretion is low urea excretion is low Urea is required to establish the concentration Urea is required to establish the concentration

gradient in the medullagradient in the medulla

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Fluid and Electrolyte BalanceFluid and Electrolyte Balance Infants: narrow chemical safety marginInfants: narrow chemical safety margin

High hydrogen ion concentrationHigh hydrogen ion concentration Low osmotic pressureLow osmotic pressure Limited ability to regulate internal environmentLimited ability to regulate internal environment

Immaturity and smaller tubule surface area Immaturity and smaller tubule surface area diminish the water reabsorption response to diminish the water reabsorption response to antidiuretic hormone (ADH)antidiuretic hormone (ADH)

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Fluid and Electrolyte BalanceFluid and Electrolyte Balance Immature tubular transport capacityImmature tubular transport capacity

The ability to excrete a potassium load, reabsorb The ability to excrete a potassium load, reabsorb bicarbonate, or buffer hydrogen with ammonia bicarbonate, or buffer hydrogen with ammonia does not become efficient until approximately 2 does not become efficient until approximately 2 years of ageyears of age

Diarrhea, infection, fasting, and poor feeding Diarrhea, infection, fasting, and poor feeding can rapidly lead to severe acidosis and fluid can rapidly lead to severe acidosis and fluid imbalanceimbalance

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Location of Body WaterLocation of Body Water

After birth the proportion of total body water to After birth the proportion of total body water to body weight does not change markedly but body weight does not change markedly but location of water doeslocation of water does

Extracellular fluid volume (ECF) of the newborn Extracellular fluid volume (ECF) of the newborn infant is nearly double that of the adultinfant is nearly double that of the adult Decrease in ECF occurs during periods of rapid Decrease in ECF occurs during periods of rapid

growth—infancy and adolescencegrowth—infancy and adolescence

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Exchange of Body WaterExchange of Body Water

Adults take in and excrete approximately 2000 Adults take in and excrete approximately 2000 ml of water daily (5% of total body fluid and 14% ml of water daily (5% of total body fluid and 14% of ECF)of ECF)

Infants exchange 600 to 700 ml (290% of the Infants exchange 600 to 700 ml (290% of the total or nearly 50% of the extracellular volume)total or nearly 50% of the extracellular volume) Makes control of dehydration and overhydration more Makes control of dehydration and overhydration more

difficult difficult

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Structural AbnormalitiesStructural Abnormalities Congenital abnormalities of the kidney and Congenital abnormalities of the kidney and

urinary tract occur in about 1 out of 500 urinary tract occur in about 1 out of 500 newborns newborns

Abnormalities Abnormalities MinorMinor NonpathologicNonpathologic Easily correctable anomalies Easily correctable anomalies Anomalies that are incompatible with life Anomalies that are incompatible with life

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Structural AbnormalitiesStructural Abnormalities Ectopic kidneysEctopic kidneys Horseshoe kidneys (1 per 600 births)Horseshoe kidneys (1 per 600 births) Hypospadias (1 in 300 infant boys)Hypospadias (1 in 300 infant boys)

ChordeeChordee Epispadias (1 in 40,000 to 118,000 births M>F)Epispadias (1 in 40,000 to 118,000 births M>F) Exstrophy of the bladderExstrophy of the bladder

Ideally the bladder and pubic defect should be closed before Ideally the bladder and pubic defect should be closed before the infant is 48 hours oldthe infant is 48 hours old

Surgical reconstruction is performed usually within the first year Surgical reconstruction is performed usually within the first year Staged procedures include bladder augmentation, bladder Staged procedures include bladder augmentation, bladder

neck closure, or reconstruction of both bladder neck closures neck closure, or reconstruction of both bladder neck closures and reconstructionand reconstruction

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Structural AbnormalitiesStructural Abnormalities Ureteropelvic junction obstruction Ureteropelvic junction obstruction

Blockage of the tapered point where the renal pelvis Blockage of the tapered point where the renal pelvis transitions into the ureter; variety of causestransitions into the ureter; variety of causes

Bladder outlet obstructionBladder outlet obstruction Urethral valves, urethral polyps, urethral atresiaUrethral valves, urethral polyps, urethral atresia

Hypoplastic or dysplastic kidneysHypoplastic or dysplastic kidneys Unilateral or bilateral; occurrence may be incidental Unilateral or bilateral; occurrence may be incidental

or familial or familial

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Structural AbnormalitiesStructural Abnormalities Renal agenesisRenal agenesis

Absence of one or both kidneysAbsence of one or both kidneys Polycystic kidney diseasePolycystic kidney disease

Autosomal dominant (1 in 1000 live births) Autosomal dominant (1 in 1000 live births) Cyst formation and obstruction accompanied by Cyst formation and obstruction accompanied by

destruction of renal parenchyma, interstitial fibrosis, destruction of renal parenchyma, interstitial fibrosis, and loss of functional nephrons and loss of functional nephrons

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GlomerulonephritisGlomerulonephritis

Poststreptococcal glomerulonephritis (PSGN)Poststreptococcal glomerulonephritis (PSGN) PSGN occurs after a throat or skin infection with PSGN occurs after a throat or skin infection with

certain strains of group A certain strains of group A αα-hemolytic streptococci-hemolytic streptococci A sudden onset of hematuria, edema, hypertension, A sudden onset of hematuria, edema, hypertension,

and renal insufficiencyand renal insufficiency Antigen-antibody complexes and complement are Antigen-antibody complexes and complement are

deposited in the glomerulusdeposited in the glomerulus The immune complexes initiate inflammation and The immune complexes initiate inflammation and

glomerular injuryglomerular injury One of the most common postinfectious renal One of the most common postinfectious renal

diseases in children ages 5 to 15 yearsdiseases in children ages 5 to 15 years

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GlomerulonephritisGlomerulonephritis Immunoglobulin A (IgA) nephropathyImmunoglobulin A (IgA) nephropathy

Characterized by deposition of mostly IgA but Characterized by deposition of mostly IgA but some IgM antibodies and complement in the some IgM antibodies and complement in the mesangium of the glomerular capillariesmesangium of the glomerular capillaries

Henoch-SchHenoch-Schöönlein purpura nephritisnlein purpura nephritis Also referred to as anaphylactoid purpuraAlso referred to as anaphylactoid purpura IgA nephropathy that causes inflammation and IgA nephropathy that causes inflammation and

damage to the glomerular blood vesselsdamage to the glomerular blood vessels

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Hemolytic-Uremic Syndrome Hemolytic-Uremic Syndrome (HUS)(HUS)

Most common cause of acute renal failure in Most common cause of acute renal failure in childrenchildren

HUS associated with bacterial and viral agentsHUS associated with bacterial and viral agents Escherichia coliEscherichia coli O157:H7 O157:H7

The bacterial toxin from The bacterial toxin from E. coliE. coli damages red damages red cells and endothelial cellscells and endothelial cells

The endothelial lining of the glomerulus The endothelial lining of the glomerulus becomes swollen and occluded with fibrin clotsbecomes swollen and occluded with fibrin clots

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Hemolytic-Uremic Syndrome Hemolytic-Uremic Syndrome (HUS)(HUS)

Causes a decreased glomerular filtration rate Causes a decreased glomerular filtration rate with hematuria and proteinuriawith hematuria and proteinuria

Swollen vessels damage red cells as they Swollen vessels damage red cells as they passpass

The damaged red cells are removed from the The damaged red cells are removed from the circulation by the spleen, causing acute circulation by the spleen, causing acute hemolytic anemiahemolytic anemia

The microcirculation develops numerous The microcirculation develops numerous thrombithrombi

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Nephrotic SyndromeNephrotic Syndrome A group of symptoms characterized by A group of symptoms characterized by

proteinuria, hypoproteinemia, hyperlipidemia, proteinuria, hypoproteinemia, hyperlipidemia, and edemaand edema Minimal change nephropathy (MCN)Minimal change nephropathy (MCN) Focal segmental glomerulosclerosis (FSGS)Focal segmental glomerulosclerosis (FSGS) Mesangial proliferationMesangial proliferation

Can develop as part of many renal diseasesCan develop as part of many renal diseases

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Urinary Tract Infections (UTIs)Urinary Tract Infections (UTIs) Common in 7- to 13-year-old girlsCommon in 7- to 13-year-old girls E. coli,E. coli, the most common pathogen, ascends the most common pathogen, ascends

the urethra in cystitis or the ureter in the urethra in cystitis or the ureter in pyelonephritis pyelonephritis

CystitisCystitis Acute pyelonephritis Acute pyelonephritis

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Vesicoureteral Reflux (VUR)Vesicoureteral Reflux (VUR) Retrograde flow of urine from the bladder into Retrograde flow of urine from the bladder into

the uretersthe ureters Reflux encourages infected urine from the Reflux encourages infected urine from the

bladder to be swept up into the kidneysbladder to be swept up into the kidneys Leads to frequent pyelonephritisLeads to frequent pyelonephritis Caused by a congenital abnormality or Caused by a congenital abnormality or

ectopic insertion of the ureter into the bladderectopic insertion of the ureter into the bladder Diagnosed by a voiding cystourethrogram Diagnosed by a voiding cystourethrogram

(VCUG) and an intravenous pyelogram (IVP)(VCUG) and an intravenous pyelogram (IVP)

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Vesicoureteral Reflux (VUR)Vesicoureteral Reflux (VUR)

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Vesicoureteral Reflux (VUR)Vesicoureteral Reflux (VUR)

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Wilms TumorWilms Tumor An embryonal tumor of the kidney An embryonal tumor of the kidney Arises from the proliferation of abnormal renal Arises from the proliferation of abnormal renal

stem cells (metanephric blastema)stem cells (metanephric blastema) Three cellular componentsThree cellular components

Stromal, epithelial, and blastemicStromal, epithelial, and blastemic Inherited and sporadic formsInherited and sporadic forms

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EnuresisEnuresis Involuntary passage of urine by child who is Involuntary passage of urine by child who is

beyond the age when voluntary bladder beyond the age when voluntary bladder control should have been acquiredcontrol should have been acquired 4 to 5 years old4 to 5 years old

Primary enuresisPrimary enuresis The child has never been continentThe child has never been continent

Secondary enuresisSecondary enuresis Diurnal, nocturnal, or bothDiurnal, nocturnal, or both

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EnuresisEnuresis TheoriesTheories

Organic causesOrganic causes Maturational lagMaturational lag Genetic factorsGenetic factors Sleep patternsSleep patterns Psychosocial theoriesPsychosocial theories