Obstruction and urolithiasis Flashcards
Outline urinary tract obstruction
- Can occur at any level
- Unilateral or bilateral
- Complete or incomplete
- Gradual or acute onset
What conditions are patients with urinary tract obstruction more at risk of?
- UTI - due to obstruction of urine flow and stasis
- Reflux
- Stone formation
What is a staghorn calculus?
- Antler-shaped calculus
- Take on shape/form of urinary tract
What are some causes of urinary retention?
- Calculi
- Pregnancy
- Benign prostatic hypertrophy (BPH)
- Recent surgery
- Drugs
- Urethral strictures
- Pelviureteric junction obstruction
- Pelvic masses
- Constipation
- Inflammation
- Tumours
- Neurogenic disorders
How does pregnancy cause urinary retention?
- High levels of progesterone relax muscle fibres in the renal pelvis and ureters
- Cause dysfunctional obstruction
How do neurogenic disorders that cause urinary retention arise?
- Congenital abnormalities affecting spinal cord
- External pressure on cord or lumbar nerve roots
- Trauma to spinal cord
Outline acute urinary retention
- Painful inability to void
- Residual volume 300-1500ml
Outline chronic urinary retention
- Painless
- May still be voiding
- Residual volume 300-4000ml
- Can get acute on chronic retention
How do we manage acute urinary retention?
- Catheterise and record residual urinary volume
- History - weight loss, haematuria, urine stream etc.
- Examination (abdo, ext. genitalia, DRE)
- Urine dip
- U&Es
- Treat any obvious causes e.g. constipation or BPH
How do we treat acute urinary retention caused by BPH?
- Alpha blocker
- May trial without catheter after 1-2 weeks
How do we manage chronic urinary retention?
- Catheterise and record residual volume
- History
- Exam
- Urine dip, U&Es (K+ needs to be monitored)
- Plan for long-term catheterisation or intermittent catheterisation
- Do not attempt to trial without catheter
Outline high pressure chronic urinary retention
- Abnormal U&Es, hydronephrosis
- Repeat episodes can cause permanent renal scarring and CKD
Outline low pressure chronic urinary retention
- Normal renal function
- No hydronephrosis
What is post-obstructive diuresis?
- Occurs following resolution of urinary retention through catheterisation
- Kidneys often over-diurese
- Can lead to worsening of AKI (pre-renal)
- Urine output should be monitored for 24 hours post catheterisation
- Patients with high urine volumes should be supported with IV fluids
What is hydronephrosis?
- Dilation of renal pelvis and calyces due to obstruction at any point in the urinary tract
- Causes increased pressure and blockage
- Can be unilateral or bilateral
What causes unilateral hydronephrosis?
- Upper urinary tract obstruction
What causes bilateral hydronephrosis?
- Lower urinary tract obstruction
How does hydronephrosis affect the kidneys?
- Progressive atrophy of the kidney develop
- Back pressure from obstruction is transmitted to distal parts of nephron
- GFR declines
- If obstruction is bilateral, patient goes into renal failure
Where is the obstruction found in hydronephrosis?
- Pelviureteric junction
What is hydroureter?
- Obstruction at ureter
- Eventually develops into hydronephrosis
What is bladder distension with hypertrophy?
- Obstruction of bladder neck/urethra
- Eventually leads to hydroureter and hydronephrosis
Outline acute ureteric obstruction
- Results in renal colic
- Usually caused by calculus but can be due to blot clots or sloughed papilla
- Usually a unilateral problem
- Leads to acute renal failure if bilateral
- Presents as anuria or oliguria
- Pyonephrosis can develop
What is pyonephrosis?
- An infected, obstructed kidney
- Urological emergency
- Failure to promptly decompress may lead to death from sepsis and permanent loss of renal function
How is upper urinary tract obstruction diagnosed?
- Diagnosis with CT or USS - show structure not function
- Diuretic renography (MAG3) is a functional test
How is the upper urinary tract drained?
- Nephrostomy
- JJ stent
Outline urolithiasis
- Urinary calculi
- Affects 10% of the population
- Especially men and Caucasians
- Dehydration is a predisposing factor (increases conc. of urine)
- High recurrence rate 860-80%
What are the 3 most common sites of urinary calculi?
- Pelviureteric junction
- Pelvic brim
- Vesicoureteric junction
What is the gold standard for diagnosing urinary calculi?
- CT scan of kidneys, ureters and bladder
What are the 5 types of urinary calculi?
- Calcium oxalate - most common, associated with hypercalcaemia, primary hyperparathyroidism, hyperoxaluria
- Mixed calcium phosphate and calcium oxalate stones - associated with alkaline urine
- Magnesium ammonium phosphate stones - associated with urea splitting bacteria
- Uric acid stones - associated with gout and myeloproliferative disorders
- Cystine stones - patients with inherited cystinuria
How do patients with urinary calculi present?
- Depends on site of stone
- Renal stones may cause a continuous dull ache in the loins
- Ureteric stones cause renal colic radiating from loin to groin. Patient appears sweaty, pale and restless with vomiting and nausea
- Bladder stones cause strangury
- Recurrent and untreatable UTIs, haematuria or renal failure
- May be asymptomatic
Why do ureteric stones cause renal colic?
- Due to increased peristalsis in ureters in response to passage of a small stone
How do we treat urinary calculi?
- Adequate analgesia
- High fluid intake
- Stones of 4-5mm usually pass spontaneously
- Larger stones might require surgical treatment
What do other treatments for urinary calculi involve?
- Extracorporeal shock wave lithotripsy: shock waves are used to fragment calculi into small pieces which will then pass out in urine
- Ureteroscopic destruction or removal of stones
- Endoscopic removal of stone (PCNL)
- Open surgical removal
How do we prevent further formation of urinary calculi?
- High fluid intake
- Correction of any underlying metabolic abnormality
