Urinary 7 - Urinary Stones Flashcards by Megan Scotcher

In what form is Calcium and Phosphate stored in bone?

Hydroxyapatite crystals [Ca10(PO4)6(OH)2]

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How many grams of Calcium is stored within an adult skeleton and teeth?

~1000g

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Which 2 hormones control serum calcium levels?

1) Parathyroid hormone

2) Calcitriol

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What stimulus causes increased secretion of PTH?

Fall in serum Calcium levels

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What tissues does PTH affect?

Kidneys

Bones

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What affect does PTH have on the kidneys?

Increases Calcium resorption
Decreases Calcium excretion
Increases conversion of Calcidiol to Calcitriol via 1alpha-hydroxylase

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What affect does PTH have on bones?

Increases osteoclast activity = increased bone resorption

- Decreases osteoblast activity

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How does Calcitriol increase serum Calcium levels?

Acts on bone: Increases Osteoclast activity

Acts on small intestine: Increases Calcium absorption

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How does Calcitriol increase Calcium absorption from the small intestine?

Increases the expression of Calcium Binding Proteins on apical gut wall

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What enzymes converts Calcidiol to Calcitriol?

1alpha-hydroxylase

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What is the function of 1alpha-hydroxylase?

Converts Calcidiol to Calcitriol

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Where does the majority of Calcium and Phosphate resorption take place?

Proximal Convoluted Tubule

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What are the 4 types of Calcium stones?

1) CaOx + CaP
2) CaP only
3) Struvite (Magnesium Ammonium Phosphate Hexahydrate)
4) Uric acid

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Name 3 types of stones which are not made up of Calcium:

1) Cysteine stones
2) Drug stones
3) Ammonium acid urate stones

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Name 3 drugs which may cause urinary stones:

1) Indinavir (for HIV)
2) Triamterene (Diuretic)
3) Sulphadiazine (Antibiotic)

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What are the most common causes of hypercalcaemia?

Primary hypersecretion of PTH

- Destruction of bone tissue due to Myeloma or diffuse metastases

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What is the most common type of urinary stone?

CaOx + CaP

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Give 5 symptoms of hypercalcaemia:

1) Painful bones
2) Abdominal groans
3) Renal stones
4) Psychic moans
5) Severe muscle weakness

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Are urinary stones more common in men or women?

Men 2:1

Except struvite stones which are more common in women due to increased incidence of UTIs in women

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Which urinary stone can grow very quickly?

Struvite stones

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What causes a Struvite stone?

Bacterial UTI, with bacteria which have Urease

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What type of stone is often caused by hyperparathyroidism, or renal tubular acidosis?

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CaP only stones

Name some causes of hypercalciuria:

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Increased Calcium absorption from GIT
Increased Calcium resorption from bone (immobilisation/weightlessness)
Excessive dietary Calcium intake
Hypercalcaemia

What type of diuretics can cause hypercalcaemia?

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Thiazide diuretics

Name some causes of hyperoxaluria:

- Primary = rare autosomal recessive genetic disorder - Increased intestinal Oxalate absorption (secondary to Crohns post resection usually) - Increased Oxalate intake and decreased Calcium intake

Name some foods high in Oxalate:

Tea Rhubarb Spinach Nuts

What are the 2 common causes of CaP-only urinary stones?

1) Hyperparathyroidism | 2) Renal tubular acidosis

What condition predisposes to cysteine stones?

Cysteinuria | Rare genetic disorder

What is Milk-Alkali syndrome?

Excessive intake of Calcium and absorbable alkali, resulting in hypercalcaemia, metastatic calcification and renal failure. Most commonly caused by post-menopausal women ODing on Calcium supplements

Who is particularly at risk of developing uric acid stones?

- Gout sufferers - People with an increased cell turnover (Lympho-/Myelo-proliferative disorders, or chemotherapy patients) - Dehydrated people

What is the most common bacteria which causes Struvite stones?

Proteus mirabilis

What shape do Struvite stones usually take, and where do they develop?

Staghorn shape | Renal pelvis and several calyces

Who are predisposed to UTI's?

- Women (shorter urethra) - Spinal cord injury - Neurogenic bladder - Vesicoureteric reflux - Obstructive uropathy (enlarged prostate/pregnancy/stones/tumours)

Describe renal colic:

Excruciating pain from flank radiating to iliac fossa or inner thigh (L1 distribution) Bouts ~ 20-60 min Untreated usually subsides within ~ hrs Often with nausea/vomiting/pallor/sweating/restlessness/haematuria

What causes renal colic?

Ureteric stone | Peristaltic contractions or spasm of ureter trying to expel stone

What is the name of the pain associated with a ureteric stone?

Renal colic

What type of pain is associated with a kidney stone?

Dull loin ache

What is the maximum diameter of a urinary stone which can be passed?

< 5 mm

At what diameter do urinary stones usually require intervention?

> 7 mm

List some presentations associated with a urinary stone:

- Man (or woman with recurrent UTIs) - Renal colic or dull loin ache - Urinary retention - Haematuria - Renal failure (fluid retention, drowsiness, SOB, fatigue, nausea)

Why are many sufferers of urinary stones resistant to increasing their water intake?

Causes increased pain - Most have urinary retention due to obstruction, so more fluid will increase the pain - May be painful to urinate due to inflammation from obstruction/UTI

What does MSU stand for?

Mid-Stream Urine sample

Why would you want an MSU from a patient with suspected urinary stone?

Microscopy for casts/RBCs/crystals | Culture bacteria

What type of stones are radio-opaque?

- CaOx + CaP - CaP-only - Struvite

What type of stones are radio-lucent?

- Uric acid stones | - Triamterene stones

Name some investigations performed when urinary stones suspected:

- MSU (culture/microscopy) - Plain abdo X-Ray - Ultrasound - CT scan of kidney, ureter and bladder - Blood: FBC, CRP, renal function, electrolytes, calcium, phosphate and urate, creatinine - Ureteroscopy

List some complications of urinary stones:

- Acute pyelonephritis +/- septicaemia (Gram +ve) - Pressure necrosis of renal parenchyma - Urinary obstruction --> hydronephrosis - Ulceration through wall of collecting system

What are the management options for someone with a urinary stone?

- Analgesia (IV Diclofenac/Pethidine if in hospital, or NSAIDs if not) - Percutaneous nephrolithotomy - Extracorporeal Shock Wave Lithotripsy (ESWL)

Describe ESWL (Extracorporeal Shock Wave Lithotripsy):

External focused high-intensity ultrasonic waves used to break up stones near renal pelvis ~ 30-60 mins

What does ESWL stand for?

Extracorporeal Shock Wave Lithotripsy

Which analgesia is usually given to patients admitted to hospital with a painful urinary stone?

IV Diclofenac/Pethidine

Potassium citrate salts may promote the formation of which type of stones?

CaP-only

How do Thiazide diuretics decrease the excretion of Ca2+?

Increase Ca2+ reabsorption

Name some urinary stone preventions:

- Increase water intake - Thiazide diuretics (decrease Ca2+ excretion) - Potassium citrate to alkalinise urine (can induce CaP stones)

Urinary 7 - Urinary Stones Flashcards

(54 cards)