L24 - Obstructive uropathy Flashcards
Congenital abnormalities of ureter
- Duplication(bifid ureter)
- Valve
- Stricture
- Abnormal course, e.g. retrocaval ureter
- Ectopic opening
Ureteric duplication
Congenital disorder
Double ureters may pursue separate courses to the bladder, but commonly are joined within the bladder wall and drain through a single ureteric orifice.
Retrocaval ureter
- Aka preureteric vena cava
- ureteric congenital anomality
- Right ureter goes under inferior vena cava
Congenital abnormalities of bladder
Extroversion (or exstrophy)
Bladder Extroversion
- absence of anterior bladder wall and lower abdominal wall
- defect of the pubic symphysis
- defect of bladder
- malformed external genitalia
- urachus may remain patent in part or in whole, forming sinus, cyst or fistula
Complications: Urachus subjected to repeated infections, squamous metaplasia and malignancy (Adenocarcinoma); associated with Epispadias
Congenital abnormalities of urethra
1) Epispadias (urethral orifice on dorsum of penis; often associated with extroversion)
2) Hypospadias (urethral orifice on ventral side of penis; more common)
3) Urethral valves (usually in male posterior urethra; cause obstruction)
Obstructive Nephropathy classification
By location of obstruction:
1) in the lumen (e.g. calculi and blood clots)
2) in the wall (tumour, infections - gonorrhoea)
3) outside the wall (prostatic hyperplasia)
By nature of obstruction:
1) Mechanical (calculi and blood clots),
2) iatrogenic (surgical or medical processes like ligation or division in pelvic surgery; or drugs that are known to cause fibrosis)
3) inflammatory (tuberculosis)
4) neoplastic and tumour-like
5) congenital and developmental (phimosis, valves, aberrant artery etc.)
Common obstructive lesions
- In males: prostatic hyperplasia
- In females: pregnancy (reversible)
- Stones
- Urothelial tumors
- Tuberculosis
- Neurogenic bladder
Renal colic
- Renal colic is the pain caused by acute ureteric obstruction
- Radiates from the loin at the back to the suprapubic region
- One of the most severe type of acute pain
- The most common cause is due to renal stone
Urinary calculi location and component
Urinary calculi may form anywhere in the urinary tract (urolithiasis) the most common sites being the pelvicalyceal system and bladder.
The most common urinary stones, accounting for 80% of cases, are composed of calcium oxalate or phosphate.
Urinary calculi pathogenesis
Main predisposing factors
1) Increased concentration of solute in urine (low fluid throughput or primary increase in metabolite)
2) Reduced solubility of solute in urine (due to persistently abnormal urinary pH).
Conditions that cause these factors to operate are low fluid intake, urine stasis, persistent urinary tract infection, and primary metabolic disturbances.
Half of urinary calculi cases are associated with idiopathic hypercalciuria, with only about 10% being secondary to hypercalcaemia. Other cases may be caused by hyperoxaluria, which has several associations, e.g. ingestion of large amount of ascorbic acid.
[note: The biggest portion of calcium in the diet usually comes from dairy products. Calcium in these milk products is usually easily absorbed.]
Possible sequelae of urinary stones:
- renal colic;
- haematuria (gross or microscopic)
- postrenal acute renal failure (if stone has obstructed a single functioning kidney or has caused acute retention of urine)
- hydroureter and hydronephrosis (-> permanent damage to the kidney)
- associated infections (acute infective complications such as acute pyelonephritis, pyonephrosis, and perinephric abscess)
Staghorn Stone
Branched renal calculi that occupy a large portion of the collecting system of kidney. Typically, they fill the renal pelvis and branch into several or all of the calices.
Patterns of urinary obstruction
Obstruction may be:
- sudden or insidious
- partial or complete
- unilateral or bilateral
- occur at any level of the urinary tract from the urethra to the renal pelvis.
Bilateral obstruction prognosis
Bilateral involvement with effects upon the whole system is seen due to obstructions in the urethra (gonorrhoea stricture) or bladder neck (prostatic hyperplasia). Effects include:
1) Bladder muscle hypertrophy gives trabeculations and bladder diverticuli, which may perforate
2) Building up of intravesicular pressure causes ureteric outflow obstruction and predisposes to vesico-ureteric reflux. The result is bilateral hydroureters and hydronephrosis.
3) Hypertension is common in such patients.
4) Complete bilateral obstruction results in anuria and is incompatible with long survival unless the obstruction is relieved.
5) Infections (bladder diverticulitis, peritonitis) and stone formation and aggravation are frequent complications proximal to the obstruction site due to poor drainage.
6) Acute retention of urine –> acute renal failure
7) Renal colic in acute ureteric obstruction
8) Unrelieved obstruction always leads to permanent renal damage and impairment of renal function
Hydroureter and hydronephrosis
Respectively refers to the dilatation of the ureter and pelvi-calyceal system, caused by obstruction of urinary free flow
Vesicoureteral reflux
- Reflux of urine from bladder back to ureter and kidneys
- Rise in intravesical pressure may lead to vesicoureteral reflux
- Normally valve-like action of intramural part of the ureter prevents reflux (at vesicoureter junction)
- Severity of reflux depends on intravesical pressure and competence of valve-like effect at the vesicoureteral junction
Grading of Vesicoureteral reflux
Reflux can be demonstrated and graded by a micturition or voiding cystogram with radiologic contrast filling the bladder via a bladder catheter
Vesicoureteral reflux and kidney scarring
- Deep cortical scar with corresponding scar in the medulla
- Scarring of kidney may occur when:
- Sterile reflux occurs at high pressure
- Urine gets infected (chronic pyelonephritis)
Note: Reflux associated renal scars tend to be at the polar areas where _intrarenal reflux i_s more prone to occur
Papillary necrosis or Necrotizing papillitis
Necrosis of renal papillae (may be presented with inflammation)
CAUSES:
1) Urinary tract obstruction (plus infection)
2) Diabetes Mellitus
3) Analgesic nephropathy
4) Hemoglobinopathies, e.g. sickle cell anemia
[2-4: associated with microvascular disease]
EFFECTS
- hematuria
- renal colic (by sloughing)
- acute renal failure (when extensive)
- chronic renal failure
- predisposition to infection
- predisposition to urothelial (transitional cell) carcinoma of the renal pelvis.
