URINARY OBSTRUCTION

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URINARY OBSTRUCTION STASIS

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Obstructive Uropathy

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? ? ? ? II
Obstructive Uropathy

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• 6. ???? ?? ? ???? ????? ????.

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Etiology

• Obstructive Uropathy

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1. Etiology

• Functional obstruction
• 1gt loss of ureteral peristalsis
• 2gt vesicoureteral reflux
• 3gt neurogenic bladder
• with detrusor-sphincter
  dyssynergia

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1. Etiology

• Mechanical obstruction
• 1. Congenital
• 1gt intrinsic UPJ obstruction, UVJ
  obstruction,
• ureterocele,
  ectopic ureter, phimosis
• posterior urethral
  valve, meatal stenosis,
• 2gt extrinsic UPJ obstruction,
  retrocaval ureter
• 2. Acquired
• 1gt intrinsic stone, bladder
  tumor, BPH,
• urethral stricture
• 2gt extrinsic retroperitoneal
  fibrosis, pregnancy,
• metastasis (cervix
  ca., colon ca.)

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Pathogenesis

• Obstructive Uropathy

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2. Pathogenesis

• 1. Lower tract
• - dilatation of the urethra proximal to
  obstruction
• 2. Mid tract (bladder)
• - stage of compensation detrusor
  hypertrophy
• - stage of decompensation dilatation
  atony
• 3. Upper tract
• 1gt Ureter
• - compensation thickening,
  tortuosity, elongation
• - decompensation dilatation
• 2gt Kidney
• - convex(clubbed) calyx ?
  compression ischemic
• - pyelointerstitial reflux
• - contralateral compensatory
  hypertrophy

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2. Pathogenesis

• Renal counterbalance
• functional impairment in unilateral
  hydronephrosis
• will be greater and will increase
  faster
• than that seen in bilateral
  hydronephrosis.

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Pathology

• Obstructive Uropathy

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3. Pathology

• 1. kidney weight
• - increase initially (edema)
• - after 4 to 8 wks, decrease
  (atrophy)
• 2. first few days flattening of the papilla
• 1 wk dilated collecting tubules show
  some atrophy
• 2 wk atrophy of proximal tubules
• 4 wk 50 decrease in medullary
  thickness
• pathologic changes in
  glomerulus
• 8 wk 1cm parenchyme
• 3. Tamm-Horsfall protein casts in Bowman's space
• pathognomonic of obstruction or VUR.

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Pathophysiology

• Obstructive Uropathy

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4. Pathophysiology

• Functional changes
• 1gt concentrating ability
• the first parameter of renal
  function
• to be impaired and is the
  last to return
• 2gt GFR ?, RBF ?
• 3gt sodium reabsorption ?, urine
  acidification ?
• 4gt urea Cr ratio ? (in urine)
• 5gt urine dilution is not affected.

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4. Pathophysiology

• Turnover of renal pelvis urine
• in hydronephrosis
• 1gt extravasation into the perirenal
  space ------ high pr.
• 2gt pyelovenous backflow
  ------------------------ high pr.
• 3gt pyelolymphatic backflow
  --------------------- low pr.

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4. Pathophysiology

• Acute obstruction (Triphasic response)
• --------------------------------------------
  ------------------
• 
  RBF ureteral pr.
• ------------------------------------------------
  --------------
• Phase I (0 - 1.5 hr.) ?
  ?
• Phase II (1.5 - 5 hr.) ?
  ?
• Phase III (5 - 18 hr.) ?
  ?
• ------------------------------------------------
  --------------
• prostaglandins
  (vasodilatation)
• thromboxane
  (vasoconstriction)

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4. Pathophysiology

• Chronic obstruction
• Ureteral pressure 15 mmHg
  (6-8 wk)
• RBF 18 (6 wk)
• GFR 0.4 ml/min (5 wk)
• - 6 weeks of complete
  obstruction in the dog
• ? no return of function

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4. Pathophysiology

• Unilateral vs. bilateral obstruction
• 1. Mechanism of decreased GFR
• 
  Unilateral Bilateral
• tubular pressure
  ?, N ??
• afferent arteriolar pr.
  ?? ?
• 2. Filtration fraction (GFR/RPF)
• unilateral ? (GFR ?? / RPF
  ?)
• bilateral ? (GFR ? /
  RPF ??)

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4. Pathophysiology

• Postobstructive diuresis
• in bilateral obstruction
• - massive diuresis after relief of
  chronic obstruction
• - mechanism 1. impaired sodium
  reabsorption
• 2. impaired urine
  concentrating ability
• 3. solute diuresis
  (retained urea)
• 4. decreased
  responsiveness to ADH

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4. Pathophysiology

• Recoverability of renal function
• (1) Duration of obstruction (acute,
  chronic)
• (2) Severity of obstruction (partial,
  complete)
• (3) Magnitude of intrapelvic pressure
• (4) Infection
• (5) Age
• (6) Status of contralateral kidney
  (abnormal, normal)
• (7) Bilateral or unilateral obstruction

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