HYDRONEPHROSIS

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HYDRONEPHROSIS

• Donna C. Queyquep, M.D.
• PGY II, Pediatrics
• November 19, 2004

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Definition

• The dilation of the renal pelvis and calyces.
• May be considered a physiologic response to the
  interruption of urine.
• Not always caused by obstruction.

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Incidence

• Pre-natal ultrasound
• detects fetal anomaly in 1 of pregnancies, of
  which 20-30 are genitourinary in origin and 50
  manifest as hydronephrosis

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Causes

• Can be intrinsic, extrinsic or functional and can
  be classified as to level within the urinary
  tract
• Ureter
• Intrinsic
• congenital ureteropelvic junction stricture
• papillary necrosis
• iatrogenic
• blood clot
• ureteral tumor

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Causes

• Extrinsic
• retroperitoneal cancer
• aortic aneurysm
• retrocaval ureter
• inflammatory bowel disease
• retroperitoneal hemorrhage
• lymphocele

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Causes

• Functional
• gram-negative infection
• neurogenic bladder
• Bladder
• Intrinsic
• calculi
• bladder neck contracture
• Functional
• VUR
• neurogenic bladder

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Causes

• Urethra
• Intrinsic
• urethral stricture
• Extrinsic
• BPH

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Antenatal Period

• The most common cause is physiologic dilation.
• Metanephric urine production begins at 8 weeks,
  even before ureteral canalization is complete.
• Transient obstruction with hydronephrosis occurs.

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Embryology
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Pathophysiology

• Anatomic and functional processes interrupts the
  flow of urine.
• There is a rise in ureteral pressure causing
  stretching and dilation if pressures continue to
  rise, leads to decline in renal blood flow and
  GFR.
• When significant obstruction is persistent, it
  affects nephrogenic tissue and results in varying
  degrees of cystic dysplasia and renal impairment.

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Grading of Severity of Hydronephrosis
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Most Common Causes in Neonates

• Ureteropelvic Junction Obstruction
• Ureterovesical Junction Obstruction
• Posterior Urethral Valves
• Eagle-Barrett Syndrome (a.k.a. Prune Belly
  Syndrome)
• Vesicoureteral Reflux
• Ureterocele

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Ureteropelvic Junction Obstruction

• UPJ is the most common cause of hydronephrosis in
  children.
• May be the result of incomplete racanalizaton of
  the proximal ureter, abnormal development of
  ureteral musculature, abnormal peristalsis,
  ureteral valves or polyps.
• Causes functional obstruction.

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Ureteropelvic Junction Obstruction

• Malefemale ratio is 21.
• Prior to prenatal screening, about 25 were
  diagnosed in the first year of life.
• Decreasing frequency with age.

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Clinical Details of UPJ Obstruction

• Anatomically indistinct segment of the upper
  collecting system where the renal pelvis funnels
  into the ureter.
• In 25-40 of kidneys, a supernumerary artery
  crosses the collecting system on its course into
  the kidneys lower pole causing mechanical
  obstruction.
• Occurs more often on the left side than on the
  right with a 32 ratio.

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Other facts on UPJ

• Often associated with other congenital renal
  anomalies
• ectopic or horseshoe kidneys
• duplication of the collecting system
• contralateral renal dysplasia
• MCDK
• renal agenesis
• VUR (lt40), often low grade
• VATER Syndrome

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Diagnostic Modality for UPJ

• Ultrasonography is the initial modality of
  choice.
• IVP
• Retrograde pyelography
• Radionuclide renogram

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Assessments on UTS

• Renal length/size
• Degree of caliectasis and parenchymal thickness
• Presence of ureteral dilatation

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Treatment for UPJ Pyeloplasty
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Posterior Urethral Valves

• Abnormal congenital mucosal folds that are thin
  membranes impeding bladder drainage.
• Most common obstructive urethral lesion in male
  newborns found at the distal prostatic urethra.
• Incidence is approxly 1 in 8,000 males.
• Approxly 50 have reflux.
• VCUG is the modality of choice.

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Radiographic signs of PUV

• distended prostatic urethra
• valve leaflets
• bladder and/or bladder neck hypertrophy
• diverticula
• narrow stream in the penile urethra
• incomplete emptying of the bladder

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Treatment of PUV

• Transurethral valve ablation, vesicostomy or
  upper tract diversion
• Urethral stricture is a common complication
• Fetal intervention carries a high risk with
  mortality rate of 43
• ESRD, renal insufficiency and chronic renal
  failure are long-term consequences

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• 30 of boys with posterior urethral valves whose
  symptoms present in infancy are at risk for
  progressive renal insufficiency.

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Eagle-Barrett Syndrome

• More commonly known as Prune Belly Syndrome
• Characterized by
• deficiency of abdominal wall musculature
• a dilated, non-obstructed urinary tract
• bilateral cryptorchidism
• talipes equinovarus and hip dislocation
• Incidence is 1/35-50,000
• gt95 occur in males

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• Believed to be caused by in-utero urinary tract
  obstruction and a specific mesodermal injury
  between the 4th and 10th week of gestation.
• Associated with renal dysplasia or agenesis.
• Often presents with a large-capacity, poorly
  contractile bladder.
• Heart, pulmonary, GI and orthopedic anomalies
  occur in a large percentage of PBS patients.

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Management

• Neonatal Period
• Optimize urinary tract drainage
• Monitor and treat renal insufficiency
• Antibiotic prophylaxis if reflux is present
• Children
• Surgical repair of reflux
• Orchiopexy
• Reconstruction of the abdominal wall
• Renal transplant

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Vesicoureteral Reflux

• Retrograde propulsion of urine into the upper
  urinary tract during bladder contraction.
• Primary reflux is caused by attenuation of the
  trigone and the contiguous intravesical ureteral
  musculature.
• May be caused by the ectopic insertion of the
  ureter into the bladder wall resulting in a
  shorter intravesicular ureter, which acts as an
  incompetent valve during urination.

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• The ratio of the submucosal tunnel length to the
  ureteral diameter is the primary factor
  determining the effectiveness of the normal valve
  mechanism.
• It is normally 51, and in those with reflux it
  is 1.41.
• The intramural length increases from 0.5 cm at
  birth to 1.3 cm by 12 years of age.
• Duplication of the collecting system and
  ureteroceles should also be considered.

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Some clinical facts about VUR

• It is genetic.
• Occurs in about 30 of first-degree relatives.
• 1/3 of children with a urinary tract infection
  has reflux on VCUG.
• Primary reflux tends to resolve over time as
  intravesical segment elongates with growth.

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Grading of Vesicoureteral Reflux
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Prognosis

• Kidney is most susceptible to scarring in the
  first year of life and at the time of first upper
  tract infection.
• Scars less frequently develop after the age of 5.
• VUR and scarring lead to hypertension,
  progressive renal insufficiency and failure.

• Resolves spontaneously before adolescence in
• 90 of Gr. 1 reflux
• 80 of Gr. 2
• 50 of Gr. 3
• 10 of Gr. 4
• 0 in Grade 5 reflux

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Treatment

• Observation
• Medical treatment of infections
• Surgical treatment
• significant hydroureteronephrosis
• indicated if impossible to keep urine sterile and
  reflux persists
• acute pyelonephritis occurs
• evidence of increasing renal damage

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On Presentation, how do we manage?

• Antenatal diagnosis of HN
• Enlarged palpable kidneys on PE
• Incidental finding on UTS done for
  other anomalies.

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• Management would depend on the clinical condition
  of the patient and the suspected nature of the
  lesion.
• More common to have a unilateral HN that is not
  associated with systemic or pulmonary
  complications.
• Postnatal UTS confirmation at about 1 month of
  life, depending on severity.
• Bilateral HN
• urgent work-up especially when accompanied by
  oligohydramnios and pulmonary disease
• if male infant, postnatal VCUG and UTS

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• Prophylactic antibiotics (Amoxicillin 20mg/kg PO
  daily) before VCUG is performed, as
  hydronephrosis may be due to reflux.
• DMSA scan to evaluate renal function.
• Definitely
• Check presence and regularity of voiding.
• Mild HN UA, BMP
• Moderate UA, BMP, VCUG
• Refer to specialist

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References

• Tanagho and McAninch. Smiths General
  Urology.16th ed 2004, McGraw-Hill Companies,
  USA.
• Zitelli and Davis. Atlas of Pediatric Physical
  Diagnosis. 4th ed2002, Mosby, Inc., USA.
• Resnick and Novick. Urology Secrets. 3rd ed2003,
  Hanley and Belfus, Inc., USA.
• Edmondson, J.D. Antenatal Hydronephrosis. Mar
  2004, Emedicine article.
• Wiener, J.S. Ureteropelvic Junction Obstruction,
  Congenital. Aug 2004, Emedicine article.
• Maniam, P. Hydronephrosis and Hydroureter. Aug
  2004, Emedicine article.
• Div of Urology, Childrens Hosp, Boston, MA.
  Neonatal Hydronephrosis. Digital Urology Journal.
  Internet download.

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References

• McCarthy, K. Vesicoureteral Reflux. Mar 2004,
  Emedicine article.
• Behrman, et al. Nelson Textbook of Pediatrics.
  17th ed Saunders Co., USA.
• Lloyd-Davies, et al. Color Atlas of Urology. 2nd
  edMosby-Year Book Europe Limited, London,
  England.
• Gillenwater, et al. Adult and Pediatric Urology.
  4th ed, Vol. I 2002, Lippincott Williams and
  Wilkins, USA.
• Cloherty, et al. Manual of Neonatal Care. 5th ed
  2004, Lippincott Williams and Wilkins, USA.
• Gonzales and Bauer. Pediatric Urology Practice.
  1999 Lippincott Williams and Wilkins, USA.

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