Urinary Tract Calculi

Question 1

Define

Answer 1

Stones form in collecting ducts and may be deposited anywhere from the renal pelvis to the urethra, though classically at:

• Pelviureteric junction
• Pelvic brim
• Vesicoureteric junction

Types:
o Calcium oxalate (75%)
o Magnesium ammonium phosphate (15%) o Urate (5%)
o Hydroxyapatite (5%)
o Brushite, cysteine (1%)
o Mixed

Question 2

Risk factors

Answer 2

Change in urinary pH

↘ ALKALINE: Calcium oxalate, calcium phosphate and

magnesium ammonium phosphate stones

↘ ACID: cysteine and uric acid stones

• Hypercalciuria – idiopathic, drug e.g. lithium, thiazides
• Hypercalcaemia – malignancy, hyperparathyroidism, sarcoidosis, myeloma, ↑intake
• Hyperoxaluria – ↑intake (rhubarb, spinach, strawbs, tea, tomato, beetroot, beans, chocolate, nuts), ↑colonic absorption in small bowel disease, autosomal recessive inherited enzyme deficiency
• Hyperuricaemia – tumour lysis syndrome, high cell turnover states
• Cystinuria – autosomal recessive defect of renal tubular transport
• Anatomical abnormalities – e.g. horse shoe kidneys

Question 3

Epidemiology

Answer 3

• COMMON
• 2-3% of general population
• 3 x more common in MALES
• Age group affected: 20-50 yrs
• Bladder stones more common in developing countries
• Upper urinary tract stones more common in industrialised countries

Question 4

Symptoms

Answer 4

• Renal colic → excruciating ureteric spasms, pain radiating from loin to groin with N&V
• Kidney stones → loin pain, between rib 12 and lateral edge of lumbar muscles - worsened by movement or pressure on trigger spot
• Ureteric stones →
• Lower ureter: pain in scrotum/penile tip/labia

majora, bladder irritability

• Mid-ureter may mimic appendicitis/diverticulitis
• Bladder stones → Dysuria, frequency, pelvic pain, strangury (painful, freq urination of small volumes with urgency) ±interrupted flow
• Haematuria and proteinuria ±Anuria
• UTI and pyelonephritis may co-exist (fever, rigors, loin pain, N&V)

Question 5

Signs

Answer 5

• Loin to lower abdominal tenderness
• NO signs of peritonism
• Leaking AAA is the main differential to consider in older men
• Signs of systemic sepsis if there is an obstruction and infection above the stone

Question 6

Investigation

Answer 6

Blood: U&Es, Ca2+, PO43−, Alb, PTH, vitamin D, urate, bicarbonate, serum ACE, TFT

Urine: urinalysis (blood +ve, protein, nitrates), microscopy and culture, test pH
24 hr collection: Cr clearance, Ca2+, PO43−, oxalate, urate

Plain radiography KUB: shows radio-opaque stones

CT abdomen: high diagnostic accuracy, visualises radio-lucent calculi (spiral non-contrast CT considered superior to IVU) Helps exclude differentials

X-Ray KUB: will show up 80% of stones

IV urogram (IVU): IV contract followed by radiograph, shows up filling defect in urinary outflow
Require a plain control

Renal US: to assess for hydronephrosis or hydroureter Chemical analysis: of the stone if passed

Question 7

Management

Answer 7

• NSAID analgesics e.g. diclofenac ±opioids
• Rehydrate (oral or IV)
• Treat exacerbating factors and UTI

<5mm calculi → ~90% pass spontaneous, ↑fluid intake <10 mm calculi → medical expulsive treatment

↘ Ca2+ channel blockers (e.g. nifedipine) and α-antagonists (e.g. tamulosin) reduce uteric spasm, promote expulsion and reduce requirement on analgesia

ESWL (extracorporeal shockwave lithotripsy) → non-invasive, US wave shatter stone - suitable for smaller stones in the kidneys/ureter, use if medical treatment has failed to remove stone after 48 hours

Cystoscopy → also visualisation of the stone and urinary tract, with a laser to breaks up the stone

Percutaneous nephrolithotomy → keyhole surgery to remove stones when large (>2cm)/multiple/complex
May be necessary for calculi not suitable for other modalities

Question 8

Prevention

Answer 8

↑fluid intake

• *Calcium stones:** ↓calcium and vitamin D intake
• *Oxalate stones:** ↓oxalate-containing foods and vitamin C intake

Uric acid stones: Allopurinol (inhibits xanthine oxidase and uric acid synthesis), urinary alkalization (oral sodium bicarbonate) Cysteine stones: D-Penicillamine (chelates cysteine), urinary alkalinisation

Question 9

Complication

Answer 9

Obstruction and hydronephrosis, infection, complications of the cause

Question 10

Prognosis

Answer 10

Approximately 20% of calculi will not pass spontaneously. Up to 50% of patients may have recurrence within 5 years