Renal Calculi and Nephrocalcinosis

Question 1

Type and frequency of renal stones in the UK.

Answer 1

Calcium oxalate usually with calcium phosphate (65%)

Calcium phosphate alone (15%)

Magnesium ammonium phosphate aka Struvite (10-15%)

Uric acid (3-5%)

Cystine (1-2%)

Question 2

Calcium oxalate and phosphate stones men vs women.

Answer 2

More common in men.

Question 3

Mixed infective stones men vs women.

Answer 3

More common in women 2:1.

Question 4

Causes of renal calculi.

Answer 4

Dehydration

Hypercalcaemia

Hypercalciuria

Hyperoxaluria

Hyperuricaemia and hyperuricosuria

Infection

Cystinuria

Primary renal disease

Drugs.

Question 5

Give examples of impairment of inhibitors that prevent crystallisation.

Answer 5

Inorgnaic magnesium

Pyrophosphate

Citrate

Glycosaminoglycans

Nephrocalcin

Question 6

Most common causes of hypercalciuria.

Answer 6

Hypercalcaemia

High dietary intake of calcium

Excessive resorption of calcium from the skeleton

Idiopathic

Question 7

Some common causes of hypercalcaemia.

Answer 7

Primary

Vitamin D ingestion

Sarcoidosis

Question 8

Genetic causes of hyperoxaluria.

Answer 8

Inborn errors of glyoxylate metabolism.

Alanine-glyoxylate aminotransferase deficiency

Glyoxylate reductase hydroxypyruvate reductase deficiency

Question 9

Prognosis of genetic causes of hyperoxaluria.

Answer 9

Widespread calcium oxalate crystal deposition in the kidneys leading to CKD in late teens or early twenties.

Successful liver transplantation has been shown to cure the metabolic defect.

Question 10

Common causes of mild hyperoxaluria.

Answer 10

Excess ingestion of spinach, rhubarb and tea.

Dietary calcium restriction leading to increased absorption of oxalate.

GI disease such as Crohn’s leading to increased absorption of oxalate.

Question 11

Causes of hyperuricaemia.

Answer 11

Idiopathic gout

Myeloproliferative disorders leading to increased cell turnover.

Dehydration

Patients with ileostomies (loss of bicarb leading to acidic urine)

Question 12

Causes of struvite stones.

Answer 12

UTI especially due to Proteus mirabilis which hydrolyse urea.

Question 13

Primary renal diseases leading to calculi.

Answer 13

Polycystic renal disease

Medullary sponge kidney leading to dilation of the collecting ducts that leads to urinary stasis and calcification.

Renal tubular acidosis . Presistently alkaline urine and reduced urinary citrate excretion lead to stone formation.

Question 14

Drugs that promote calcium stone formation.

Answer 14

Loop diuretics

Antacids

Glucocorticoids

Theophylline

Vitamins D and C

Acetazolamide

Question 15

Drugs that promote uric acid stones.

Answer 15

Thiazides

Salicylates

Question 16

Drugs that can precipitate into stones.

Answer 16

Indinavir

Trimaterene

Sulfadiazine

Question 17

Clinical features of renal calculi.

Answer 17

Usually asymptomatic

Most common symptoms is pain.

Haematuria

UTI

UTO

Sweating, pallor, vomiting

Question 18

Explain the pain in renal calculi.

Answer 18

Sharp or dull

Constant, intermittent or colicky

Fluids and diuretics can worsen it

Exertion might mobilise some calculi and cause pain

When a stone enters the ureter it will cause pain and associated nausea.

Question 19

What are bladder stones associated with?

Answer 19

Bacteriruia

Frequency

Dysuria

Haematuria

Severe introital or perineal pain may occur if trigonitis is present.

Question 20

Investigations of renal calculi.

Answer 20

FBC, U&Es, Ca2+, PO43-, glucose, bicarbn, urate

Urine dipstick usually +ve for blood

Urine pH

24h urine for calcium, oxalate, urate citrate, sodium, crea and stone biochemistry.

Mid-stream speciemn of urine

Ultrasonography

Non-contrast CT (CT-KUB) is the best investigation of choice. It helps exclude other differentials such as rupture AAA. 99% of stones are visible.

XR-KUB 80% of stones are visible.

Question 21

What stones are radiolucent?

Answer 21

Uric acid stones.

However with injection of contrast it shows as a filling defect.

It can also be seen on CT.

Question 22

Management of calculi regardless of size.

Answer 22

Analgesia (diclofenac 75mg IV/IM or 100 mg PR), opioids if CI.

Antibiotics (piperacillin/tazobactam or gentamicin) if infection.

Lots of fluids!

Question 23

Management of stone < 5 mm in lower ureter.

Answer 23

90-95% pass spontaneously.

Just increase fluid intake.

Question 24

Management of stone > 5 mm/pain not resolving.

Answer 24

Start nifedipine 10mg/8h or alphablockers like tamsulosin.

If it still doesn’t pass try ESWL if the stone is less than 1 cm or ureteroscopy using a basket.

Percutaneous nephrolithotomy can be used to remove larger stones, mutliple or complex.

Question 25

Prevention of urinary calculi.

Answer 25

Drink plenty

Normal dietary Ca2+ intake (not too low as that can cause refractory Oxalate excretion and oxalate stone)

In calcium stones a thiazide can be used.

In oxalate stones pyridoxine can be used and reduced oxalate intake.

In struvite stones you treat infection promptly or might even need proactive antibiotics.

In urate stones allopurinol, urine alkalinisation can also help.

Cystine requires vigorous hydration.

Question 26

Give causes of nephrocalcinosis.

Answer 26

Renal cortical necrosis (rare)

Hypercalcaemia

Renal tubular acidosis

Primary hyperoxaluria

Medullary sponge kidney

TB