Diseases of the renal system 2 Flashcards
What is obstructive uropathy?
- Obstruction of the urinary tract
- Can occur anywhere from the renal pelvis to the urethral meatus
- Onset may be chronic or acute
- Unilateral or bilateral
What are the pelvic causes of urinary tract obstruction?
- calculi
- tumours
- ureteropelvic stricture
What are the ureter-intrinsic causes of urinary tract obstruction?
- calculi
- tumours
- clots
- sloughed papillae
- inflammation
What are the ureter-extrinsic causes of urinary tract obstruction?
- pregnancy
- tumours (i.e. cervix)
- retroperitoneal fibrosis
What are the bladder causes of urinary tract obstruction?
- calculi
- tumours
- functional (e.g. neurogenic)
What are the prostatic causes of urinary tract obstruction?
- Hyperplasia
- carcinoma
- prostatitis
What are the urethral causes of urinary tract obstruction?
- Posterior valve stricture
- tumours (rare)
What are the possible sequelae of urinary tract obstruction?
- Infection- cystitis, ascending pyelonephritis
- Stone/calculi formation
- Kidney damage - Acute or chronic
What do the consequences of a urinary tract obstruction depend on?
- Site of obstruction
- Degree of obstruction
- Duration of obstruction
What is the result of obstructive uropathy - acute complete obstruction?
- Reduction in glomerular filtration rate
- Mild dilatation and mild cortical atrophy
- Can cause acute renal failure
What is the result of obstructive uropathy - chronic and intermittent?
- Continued glomerular filtration -> Dilatation of pelvis+calyces
- Filtrate passes back into interstitium -> Compression of medulla -> Impaired concentrating ability
- Eventual cortical atrophy, fall in renal filtration and renal failure
What are the clinical features of obstruction?
Acute bilateral obstruction
- Pain,
- Acute renal failure and anuria
Chronic unilateral obstruction
- Asymptomatic initially
- If unresolved cortical atrophy and reduced renal function
Bilateral partial obstruction
- Initially polyuric with progressive renal scarring and impairment
What is the epidemiology of renal calculi?
- Affect 7-10% of the population - increasing
- Male predominance
- Peak onset 20 – 30
- Can form anywhere in the urinary tract but most commonly in the kidney
What is the pathogenesis of renal calculi?
- Either due to an excess of substances which may precipitate out e.g. Ca+
- A change in the urine constituents causing precipitation of substances e.g. change in pH
- Poor urine output – Supersaturation
- Decreased citrate levels
How are renal calculi composed?
By composition
- Calcium stones (70%) - calcium oxalate +/- calcium phosphate
- Struvite stones (15%) – magnesium ammonium phosphate
- Urate stones (5%) – uric acid
- Cystine stones (1%)
What is the most common cause of calcium stones?
Most commonly identified cause is hypercalciuria, due to:
- Hypercalcaemia
- Bone disease, PTH excess, sarcoidosis
- Excessive absorption of intestinal Ca+
- Inability to reabsorb tubular Ca+
- Idiopathic
What are the other risk factors for calcium stones?
- Gout: forms a core for Ca+ crystal formation
- Hyperoxaluria:
- Hereditary
- Excess dietary intake
What is the pathogenesis of struvite stones?
- Urease producing bacterial infection (proteus)
- Urease converts urea to ammonia
- Causes a rise in urine pH
- Precipitation of magnesium ammonium phosphate salts
- Large “staghorn” calculi
What are the causes of urate stones?
Hyperuricaemia
- Gout
- Patients with high cell turn over e.g. leukaemia
Idiopathic
What are the causes of cystine stones?
- Rare
- Occur in the presence of an inability of kidneys to reabsorb amino acids
What investigations do you performs for renal calculi?
- Non-contrast CT scanning is gold standard-
sensitivity of >95% - Ultrasound in pregnancy or where CT not possible 30-67% sensitive
- Intravenous urography 70% sensitive for stones
What are the sequelae of renal calculi?
- Obstruction
- Haematuria
- Infection
- Squamous metaplasia +/- Squamous cell carcinoma
What percentage of cancers are renal cell?
3%
What is the most common kind of renal cell carcinoma?
clear cell