Urinary Tract Obstruction and Urolithiasis

Urinary Tract Obstruction Urolithiasis Axel Baez Torres, M.D.  Objectives Describe the pathophysiology mechanisms induced in urinary tract obstruction Recall the clinical features, clinical course and treatment of urinary tract obstruction Describe th...

Urinary Tract Obstruction Urolithiasis Axel Baez Torres, M.D.  Objectives Describe the pathophysiology mechanisms induced in urinary tract obstruction Recall the clinical features, clinical course and treatment of urinary tract obstruction Describe the mechanisms involved in the formation of renal calculi Recall the different types and prevalence of renal calculi with the emphasis on associated clinical conditions  Objectives Recall the clinical course and treatment of patients with renal calculi Describe renal cystic dysplasia in terms of pathogenesis associated congenital anomalies, pathology and clinical course Urinary Tract Obstruction The causes of urinary tract obstruction are multiple Among intrinsic causes nephrolithiasis, sloughed renal papilla, strictures and cancer are the most common Among extrinsic causes carcinoma of the uterine cervix or endometrium, prostatic hyperplasia, retroperitoneal fibrosis and retroperitoneal tumors are the most common  Urinary Tract Obstruction Urinary tract obstruction is more common in males than females in childhood; the most common causes include ureteropelvic or vesicoureteral obstruction Between childhood and age 60 is more common in females; the most common cause is a gynecologic tumor After age 60 is again higher in men, primarily because of prostatic disease  Urinary Tract Obstruction Pathophysiology – The pathophysiologic mechanisms by which urinary tract obstruction damages the kidney include increased pressure into the medulla, intrarenal reflux of urine and direct pressure on blood vessels within the medulla  Urinary Tract Obstruction Clinical Features – The clinical picture of urinary tract obstruction is highly variable; bilateral partial obstruction may present with loss of ability to concentrate urine whereas sudden complete obstruction presents with acute renal failure  Urinary Tract Obstruction Treatment and Clinical Course – Treatment depends on the primary condition causing the obstruction – The most important factor in determining the degree of recovery is the duration of obstruction  Urolithiasis The formation of renal calculi depends on a balance of factors: – Concentration of the specific component (supersaturation) – Presence of nucleating factors such as epithelial cells, debris or casts – Deficiency of stone inhibitors such as nephrocalcin, the Tamm- Horsfal protein or citrate  Renal Calculi Type Proportion Calcium Oxalate 75% Struvite 10-15% Uric Acid 5-6% Cystine 1% Other 15%  Urolithiasis Calcium Oxalate Stones – Vast majority of renal calculi – Over half calculi are associated with hypercalciuria without hypercalcemia – Approximately one fifth are associated with hyperuricosuria  Urolithiasis Struvite Stones – Magnesium ammonium phosphate stones – Strongly associated with infection with urea- splitting bacteria, most often Proteus species – Large staghorn calculi are almost always associated with this type of stone  Urolithiasis Uric Acid Stones – Majority of patients have neither hyperuricemia or hyperuricosuria – Stone formation in this patients is believed to be due to a tendency to excrete urine with pH below 5.5 as uric acid is insoluble in acidic urine  Urolithiasis Clinical Features – Renal colic syndrome manifested by flank/groin excruciating pain; nausea and vomiting are frequent – Calculi may be painless if they remain in the pelvis – Hematuria is a frequent manifestation  Urolithiasis Clinical Course – Smaller stones are more likely to cause complications because they are free to pass into the ureter – Calculi predispose to infection due to obstruction and trauma  Urolithiasis Treatment – Stones less than 5mm are likely to pass spontaneously – Stones less than 2cm can often be treated with lithotripsy – Larger stones may require nephrolithotomy