Urinary tract calculi

Question 1

What is urinary tract calculi?

Answer 1

Presence of crystalline stones (calculi) within the urinary system (kidneys and ureter)

Question 2

What types of stones can a patient with UTC have?

Answer 2

calcium oxalate (most common, 75%), struvite (15%) uric acid (5%), cysteine (1%)

1. Calcium Oxalate ⇒ radioopaque (white on x-ray/CT), acidifies urine pH, hypercalciuria is a risk factor
2. Struvite ⇒ radioopaque, tend to form staghorn calculi, alkalizes urine pH, UTI with urease producing bacteria. Recurrent UTIs are predisposing factor (chronic proteus infection). Made up of magnesium ammonium phosphate.
3. Uric Acid ⇒ radiolucent (black on x-ray/CT - not visible on x-ray), associated with gout/hyperuricaemia

Question 3

What can cause UTC’s to form?

Answer 3

1. Many cases are IDIOPATHIC 
2. Conditions 
   - Calcium: primary hyperparathyroidism, renal tubular acidosis, sarcoidosis 
   - Oxalate: IBD (Crohn’s, Ulcerative colitis) 
3. Infection 
4. Urinary retention(due to stasis of fluid) 
5. Drugs: Indinavir, acyclovir 

Question 4

What are the risk factors for UTC?

Answer 4

dehydration, high salt intake, white ancestry, male, obesity, crystalluria 

Question 5

What are the presenting symptoms/ signs of UTC?

Answer 5

Asymptomatic until calculi gets stuck.
- Renal Colic → severe, acute flank pain that radiates to the groin (loin → groin pain)
- May be colicky
- Nausea & Vomiting
- Urinary frequency / urgency
- Haematuria (85% microscopic)
- Testicular pain

Question 6

What investigations are used to diagnose/ monitor UTC?

Answer 6

1. Non-Contrast CT KUB → Gold Standard. Urgent (within 24 hrs of presentation). Can see calcification in renal collecting system or ureter, also shows hydronephrosis (dilatation of the renal pelvis, calyces, and/or the proximal ureter due to a distal obstruction to the outflow of urine). CT’s are contraindicated in pregnant women.
   - Renal Ultrasound → if pregnant or a child
   - Hydronephrosis (Ix = Ultrasound) may indicate complete obstruction of ureter. Patient may need nephrostomy as decompression.
2. Urine Dipstick → 1st line bedside. May show microhaematuria.
3. U&E’s → if possibility of developing post-renal AKI due to obstruction
4. X-Ray → visible stone on x-ray is necessary for the use of ESWL (uric acid stones are radiolucent and are not visible on x-ray)
5. Pregnancy Test → in all women of childbearing age to exclude ectopic pregnancy.
6. FBC → raised WCC may suggest infection (UTI)

Question 7

How are UTC’s managed?

Answer 7

1. Acute → hydration, analgesia (NSAIDS - IM diclofenac), anti-emetics (treat n&v)
2. Stone <5mm and NON OBSTRUCTING → will pass spontaneously
   - Alpha blocker (tamsulosin) if stone in distal ureter, if not passed after 4-6 weeks then surgery
   - if obstructing JJ stent insertion
3. Stone >10mm or Failed Therapy → 1st line is extra corporeal shock wave lithotripsy (non-invasive method enabling stone fragmentation using an acoustic pulse), ureteroscopy (ureteroscope passed retrograde through the ureter and into the renal pelvis to remove or destroy stones), percutaneous nephrolithotomy- PCNL (minimally invasive keyhole surgery through the back to retrieve stones)
   - Ureteroscopy should be done rather than lithotripsy in pregnant patients
   - Staghorn calculi (struvite) or >20mm → PCNL
4. Calcium Stones → thiazide diuretics (cause hypercalcaemia, meaning less calcium excreted in urine).
5. Uric Acid Stones → allopurinol.
6. Infected or Obstructed System (AKI/Sepsis/Hydronephrosis) → Nephrostomy (+ IV Abx)
   - Obstructed system will cause hydronephrosis