Renal and Ureteric Stones Flashcards
What is a Nephrolithiasis/Urolithiasis?
Urinary tract calculi - crystal aggregates and stones that form in the collecting ducts.
How are renal and ureteric stones classified? (3).
Based on site of impaction :
- Pelviureteric Junction (Renal Pelvis - Ureter).
- Pelvic Brim (Ureters arch over Iliac Vessels).
- Vesicoureteric Junction (Ureter - Bladder) : commonest.
Epidemiology of Renal and Ureteric Stones (3).
- 3x commoner in Males.
- Peak Age : 20-40.
- Lifetime Incidence : 15%; 50% of them have renal colic again within 5 years.
What is the main presenting complaint in a symptomatic stone (4)?
RENAL COLIC :
- Colicky (fluctuating pain severity based on motion of stone).
- Unilateral.
- Loin-to-Groin.
- Excruciating Pain.
Clinical Features of Stones (5).
- Asymptomatic.
- Renal Colic.
- Microscopic Haematuria.
- Oliguria.
- Nausea and Vomiting.
What is a Staghorn Calculus?
A stone involving the renal pelvis and extending into at least 2 calyces.
What conditions can predispose Staghorn Calculus development? (3)
- Alkaline Urine.
- Struvite (recurrent UTIs - bacteria hydrolyse urea into Ammonia which creates Struvite).
- Ureaplasma Urealyticum and Proteus Infections.
Calcium Oxalate Stones Profile :-
- Proportion of Stones.
- Risk Factors (3).
- Imaging.
Proportion : 85%.
Risk Factor : Hypercalciuria (Main); Hyperoxaluria and Hypocitraturia.
Imaging : Radio-opaque (less than Calcium Phosphate).
Why is Hypocitraturia a cause of stones?
Citrate usually forms complexes with Calcium which makes it more soluble.
What are the 3 main causes of hypercalcaemia?
- Calcium Supplementation.
- Hyperparathyroidism.
- Cancer e.g. Myeloma, Breast, Lung
Cystine Stones Profile :-
- Proportion of Stones.
- Aetiology.
- Imaging.
Proportion : 1%.
Aetiology : Inherited AR Disorder of Transmembrane Cystine Transport leading to reduced absorption of Cystine from the intestine and renal tubule.
Imaging : Radiodense - contain Sulphur; semi-opaque with ground-glass appearance.
Uric Acid Stones Profile :-
- Proportion of Stones.
- Risk Factors (2).
- Aetiology.
- Imaging.
Proportion : 5-10% of Stones.
Risk Factors : Gout & Ileostomy (loss of HCO3- and fluid so urine is more acidic).
Aetiology : Uric acid is a product of purine metabolism - precipitating when urinary pH is low e.g. disease with extensive tissue breakdown (malignancy) and kids with inborn errors of metabolism.
Imaging : Radiolucent (not visible on X-Ray).
Calcium Phosphate Stones Profile :-
- Proportion of Stones.
- Aetiology.
- Imaging.
Proportion : 10% of Stones.
Aetiology : High Urinary pH causes supersaturation of urine with Calcium and Phosphate = RTA Type I and III.
Imaging : Radio-opaque like bone.
Struvite Stones Profile :-
- Proportion of Stones.
- Aetiology.
- Imaging.
Proportion : 2-20% of Stones.
Aetiology : Result of Urease-producing bacteria (chronic infection).
Imaging : Radio-opaque.
Give 4 drugs that promote the formation of Calcium stones.
LAST :-
- Loop Diuretics.
- Acetazolamide.
- Steroids.
- Theophylline.
Why do Thiazide Diuretics prevent the formation of Calcium stones?
Increased distal tubular Calcium resorption.
Investigations of Renal Stones.
- Urine Dipstick - Microscopic Haematuria.
- Urine pH (types of stones).
- CT KUB (Gold-Standard) within 14 hours of admission.
How does urine pH change after a meal?
- Normal Range = 5-7.
- Post-prandially (after a meal) - purine metabolism produces uric acid (pH should fall).
- Alkaline Tide - urine becomes more alkaline later.
- Look at urine pH for indication of different types of stones.
What is CT KUB?
Non-Contrast CT of Kidney, Ureters and Bladder.
Alternative of CT KUB.
US KUB - useful in pregnant women and kids.
Symptomatic Management of Stones (3).
- NSAIDs - analgesia of choice e.g. PR/IM Diclofenac (or Paracetamol).
- Antiemetics - N&V.
- Antibiotics - Infection.
Passage of Stones (2).
- Less than 6mm = 50% chance of passing without intervention (4 weeks).- WATCH & WAIT.
- Tamsulosin (a-Blocker) can help spontaneous passage.
Surgical Management of Stones (4).
- Extracorporeal Shock Wave Lithotripsy.
- Uteroscopy and laser Lithotripsy.
- Percutaneous Nephrolithotomy.
- Open Surgery.
What is Extracorporeal Shock Wave Lithotripsy (2)?
- Direct shock wave at stone under X-ray guidance to break it down.
- Shock waves can cause solid organ injury - analgesia pre and post-procedure.
What is Uteroscopy and Laser Lithotripsy (3)?
- Insert Camera via Urethra, Bladder and Ureter to identify stone and use targeted laser to break it down.
- Indication : ESWL is contraindicated e.g. pregnancy, complex stone disease.
- Leave stent in situ for 4 weeks.
What is Percutaneous Nephrolithotomy (2)?
- Insert Nephroscope via small incision in back through kidney to assess ureter.
- General anaesthesia in theatre.
Immediate Emergency Management of Renal Stones (3).
- Bypass obstruction via Nephrostomy and remove stone using Ureteroscopy.
- Ureteric Obstruction due to Stones + Infection = Emergency.
- Decompress using Nephrostomy Tube Placement, Ureteric Catheter and Ureteric Stent.
Main Complications of Renal Calculi (2).
- Obstruction - AKI.
2. Infection with Obstructive Pyelonephritis.
Risk Reduction of Future Episodes of Renal Stones (7).
- Dehydration - Increase Oral Fluids.
- Fresh Lemon Juice (Hypercitraturia).
- Avoiding Carbonated Drinks (Phosphoric Acid promotes Calcium Oxalate stone).
- Reducing Dietary Salt (6g/day).
- Reducing Oxalate-Rich Food (Spinach, Nuts, Rhubarb, Tea).
- Reducing Urate-Rich Food (Kidney, Liver, Sardines).
- Medications : Potassium Citrate, Thiazide Diuretics e.g. Indapamide.
