Ureteric calculi

Section: Urology Curriculum: Curriculum, page 29

Definition

• Renal stones located anywhere along the GU tract with the potential to cause pain, obstruction and infection

Epidemiology

• M>F 2:1 with peak age 40

Classification

• Stone type
  • 80% - Calcium - calcium oxalate and calcium phosphate
  • 10% - Struvite - magnesium, ammonium and phosphate
  • 9% - Uric acid
  • 1% - Cystine

Aetiology

• Risk Factors
  • Non-modifiable
    • FHX of stones
    • Genetic susceptibility
    • Medical conditions = primary hyperparathyroidism, gout, diabetes, medullary sponge kidney, type 1 renal tubular acidosis, UTI, cystinuria
  • Modifiable
    • Urinary - high ca, high oxalate, low citrate, high uric acid, low volume, low pH
    • Dietary - low fluid intake, low calcium, low K
    • Medications - steroids, loop diuretics, antivirals, some abs - Ceftri, cipro
• Stone specific causes
  • Calcium - hyperparathyroid, hypercalciuria, hyperoxaluria
  • Struvite - recurrent UTI - proteus/klebsiella
  • Uric acid - gout

Pathophysiology

• Stone formation
  • Supersaturation of urine by stone forming constituents
    • Usually crystals or FBs act as a nidus
    • Oxalate, calcium, uric acid and low volume
  • Crystal nucleation, growth, aggregation and cell interaction
  • Crystal retention and stone formation
• Renal Colic
  • Obstruction of ureter with continual ureteric peristalsis in an attempt to pass the obstructing stone
  • With obstruction causing urine stasis and no flow this can lead to stagnation and bacterial infection → septic stone or pyelonephritis
  • The obstruction places back pressure on the kidney resulting in reduced GFR and subsequent AKI/CKD

Clinical

• Loin to groin flank pain and tenderness typical of renal colic
• N+V and urinary sx - haematuria, dysuria
• +/- constitutional sx

Investigations

• Bloods
  • Inflammatory markers
  • Renal function and electrolytes
  • Para - calcium, PTH, phosphate
  • Uric acid
• Urine
  • MC+S, casts
• Imaging
  • X-ray KUB - 85% of stones (the calcium ones) can be seen
  • Helps determine if F/U can be with xray instead of CT
  • CTKUB - 95% sensitivity
    • R/O other causes
    • Scout film - determines if xray can be used for F/U
    • Ureteral dilation, hydroneph, enlarged kidney, stranding
  • Renal USS
    • Useful in pregnancy to assess for ureteral dilatation or hydropneph

Management

• Principles
  • Relieve obstruction - alpha blocker, JJ stent, nephrostomy
  • Treat sepsis - abx, IVF, pressors
• Approach
  • CRISP
  • Abx if signs of infection
  • IVF
  • Indications for admission
    • Urosepsis
    • Renal impairment or solitary kidney
    • Unable to manage pain
    • Ureteric stone >5mm
  • Surgery
    • Indications
      • Ureteral stones >1cm
        • <10mm stones that have not passed within 4-6 weeks
      • Symptomatic stones
      • Solitary kidney
    • Options
      • JJ stent
      • ESWL
      • Percutaneous Nephrolithotomy
      • Nephrostomy tube

Prognosis

• <6mm stone >80% chance of passing

• 7mm unlikely to pass on its own

• Sx can be ongoing for weeks despite stone passage
• Xray KUB or USS in 6 weeks to confirm resolution can be done

Extra

• Narrow points of the ureter - PUJ, where the ureter crosses the common iliac A bifurcation, VUJ
• Causes of ureteric obstruction
  • Luminal - stone
  • Mural - urothelial malignancy, bladder malignancy, stricture
  • Extrinsic compression - tumour benign or malignancy