2. B-Late changes In severe degree of obstruction : The intrapelvic pressure becomes closure or higher than the glomerular filtration rate(6-12mm Hg), -less urine can be secreted. -Glomerular filtration rate and renal plasma flow are reduced. -Concentration ability is gradually reduced. -In severe unilateral obstruction fluid and soluble substances reabsorbed through either the tubules or the lymphatic and will excreted by other kidney.

3. Irreversible progression of loss of function may occur as early as 7days(dilatation and necrosis of the proximal tubules. Recovery of renal function may take up to 4weeks after release of complete obstruction. The extent of recovery is difficult to asses before release of the obstruction.

4. Common causes of urinary tract obstruction: 1- Lower &Mid tract: Urethral stricture. B.P.H. Neurogenic bladder. Bladder neck Tumor. Bladder neck stenosis.. In neonates posterior urethral valve. 2-Upper tract: Ureteropelvic junction stenosis,ureteral or renal pelvis stone,ureteral stricture.

5. Symptoms: 1- Lower and mid tract symptoms: In stage of compensation :with hypertrophied detrusor the contraction is so strong producing symptoms of the irritable bladder: urgency, urge incontinence,and frequency,dysuria. In stage of decompensation :vesical tone become impaired, or urethral resistance exceed detrussor power producing symptoms of obstruction: Hesitancy, week stream, urinary retention,terminal dribbling

6. Upper and Lower tract symptoms: - Flank and radiated pain. -Gross hematuria. -Gastrointestinal symptoms. -Chills,Fever. -Cloudy urine,Dysuria.

7. Signs: 1-Lower &Mid tract : -Induration in urethra(Urethral stricture). -DRE: atony of the anal sphincter(damage to sacral nerve roots). -Enlarged prostate. -Vesical distention. -Observation of the force and caliber of the urinary stream.

8. 2-Upper tract: -Enlarged kidney. -Large pelvic mass(pregnancy,tumor). -Children's with advanced urinary tract obstruction may develop ascites. Laboratory Findings: -Anemia. -Microscopic hematuria. -In significant bilateral hydronephrosis: Urea-Creatinine ratio is above 10.

9. – X-RAY: Plain film of the abdomen: Enlargement of the renal shadow. Calcified shadows :renal or ureteral,tumor or metastases to the bones of the pelvis or spine. Intravenous pyelogram : Information about the function. degree and level of obstruction. Radiopaque and radio lucent stones. Bladder trabeculation and and diverticuli. Tumors Residual urine.

11. Retrograde urethro-cystogram:

12. Ultrasound

13. Renal Isotopes scan

14. C.T

16. Treatment 1-Relief of the obstruction. 2-Eradication of the infection.