Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.


Pronephros

Mesonephros

Metanephros
 Ureteric bud
 Metanephrogenic blastema

Urine formation and excretion begin by the third month of gestation
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
2




Blood flow to the kidney in a newborn is primarily to the medullary nephrons
Because of short loops of Henle in the medullary nephrons, an infant produces more dilute urine
Infants are in a high anabolic state, so their urea excretion is low
 Urea is required to establish the concentration gradient in the medulla
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
3


Infants: narrow chemical safety margin
 High hydrogen ion concentration
 Low osmotic pressure
 Limited ability to regulate internal environment

Immaturity and smaller tubule surface area diminish the water reabsorption response to antidiuretic hormone (ADH)
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
4


Immature tubular transport capacity
 The ability to excrete a potassium load, reabsorb bicarbonate, or buffer hydrogen with ammonia does not become efficient until approximately 2 years of age

Diarrhea, infection, fasting, and poor feeding can rapidly lead to severe acidosis and fluid imbalance
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
5


After birth the proportion of total body water to body weight does not change markedly but location of water does

Extracellular fluid volume (ECF) of the newborn infant is nearly double that of the adult
 Decrease in ECF occurs during periods of rapid growth —infancy and adolescence
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
6


Adults take in and excrete approximately 2000 ml of water daily (5% of total body fluid and 14% of ECF)

Infants exchange 600 to 700 ml (290% of the total or nearly 50% of the extracellular volume)
 Makes control of dehydration and overhydration more difficult
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
7


Congenital abnormalities of the kidney and urinary tract occur in about 1 out of 500 newborns

Abnormalities
 Minor
 Nonpathologic
 Easily correctable anomalies
 Anomalies that are incompatible with life
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
8






Ectopic kidneys
Horseshoe kidneys (1 per 600 births)
Hypospadias (1 in 300 infant boys)
 Chordee
Epispadias (1 in 40,000 to 118,000 births M>F)
Exstrophy of the bladder
 Ideally the bladder and pubic defect should be closed before the infant is 48 hours old
 Surgical reconstruction is performed usually within the first year
 Staged procedures include bladder augmentation, bladder neck closure, or reconstruction of both bladder neck closures and reconstruction
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
9


Ureteropelvic junction obstruction
 Blockage of the tapered point where the renal pelvis transitions into the ureter; variety of causes

Bladder outlet obstruction
 Urethral valves, urethral polyps, urethral atresia

Hypoplastic or dysplastic kidneys
 Unilateral or bilateral; occurrence may be incidental or familial
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
10


Renal agenesis
 Absence of one or both kidneys

Polycystic kidney disease
 Autosomal dominant (1 in 1000 live births)
 Cyst formation and obstruction accompanied by destruction of renal parenchyma, interstitial fibrosis, and loss of functional nephrons
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
11


Poststreptococcal glomerulonephritis (PSGN)
 PSGN occurs after a throat or skin infection with certain strains of group A α-hemolytic streptococci
 A sudden onset of hematuria, edema, hypertension, and renal insufficiency
 Antigen-antibody complexes and complement are deposited in the glomerulus
 The immune complexes initiate inflammation and glomerular injury
 One of the most common postinfectious renal diseases in children ages 5 to 15 years
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
12


Immunoglobulin A (IgA) nephropathy

 Characterized by deposition of mostly IgA but some IgM antibodies and complement in the mesangium of the glomerular capillaries
Henoch-Sch önlein purpura nephritis
 Also referred to as anaphylactoid purpura
 IgA nephropathy that causes inflammation and damage to the glomerular blood vessels
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
13


Most common cause of acute renal failure in children

HUS associated with bacterial and viral agents
 Escherichia coli O157:H7

The bacterial toxin from E. coli damages red cells and endothelial cells

The endothelial lining of the glomerulus becomes swollen and occluded with fibrin clots
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
14


Causes a decreased glomerular filtration rate with hematuria and proteinuria

Swollen vessels damage red cells as they pass

The damaged red cells are removed from the circulation by the spleen, causing acute hemolytic anemia

The microcirculation develops numerous thrombi
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
15


A group of symptoms characterized by proteinuria, hypoproteinemia, hyperlipidemia, and edema
 Minimal change nephropathy (MCN)
 Focal segmental glomerulosclerosis (FSGS)
 Mesangial proliferation

Can develop as part of many renal diseases
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
16


Common in 7- to 13-year-old girls

E. coli, the most common pathogen, ascends the urethra in cystitis or the ureter in pyelonephritis

Cystitis

Acute pyelonephritis
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
17


Retrograde flow of urine from the bladder into the ureters

Reflux encourages infected urine from the bladder to be swept up into the kidneys

Leads to frequent pyelonephritis

Caused by a congenital abnormality or ectopic insertion of the ureter into the bladder

Diagnosed by a voiding cystourethrogram
(VCUG) and an intravenous pyelogram (IVP)
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
18

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
19

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
20


An embryonal tumor of the kidney

Arises from the proliferation of abnormal renal stem cells (metanephric blastema)

Three cellular components
 Stromal, epithelial, and blastemic

Inherited and sporadic forms
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
21


Involuntary passage of urine by child who is beyond the age when voluntary bladder control should have been acquired
 4 to 5 years old

Primary enuresis
 The child has never been continent

Secondary enuresis
 Diurnal, nocturnal, or both
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
22


Theories
 Organic causes
 Maturational lag
 Genetic factors
 Sleep patterns
 Psychosocial theories
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
23