RENAL STONES OR KIDNEY STONES OR NEPHROLITHIASIS

Association : It has association with hypertension, obesity, diabetes and osteoporosis.

Epidemiology : Presents between 20 to 60 years of age. Affects 10% population over lifetime and 75% recurr.

Pathophysiology : Stone growth starts with the formation of crystals in supersaturated urine which then adhere to the urothelium, thus creating the nidus for subsequent stone growth.

• Risk factors :
• Low fluid intake
• Hypercalciuria
• Excess risk of stone formation is seen in patients with primary hyperparathyroidism, deactivating vitamin D receptor (VDR) polymorphisms and activating fibroblast growth factor (FGF) 23 polymorphism.

• Oxalate stones risk factors :
• High salt diet
• Low calcium intake
• Hypocitraturia
• High animal protein intake
• Hyperoxaluria

• Other Symptoms:
• Pink, red or brown urine
• Cloudy or foul-smelling urine
• A persistent need to urinate, urinating more often than usual or urinating in small amounts
• Nausea and vomiting
• Fever and chills if an infection is present

• When to see a doctor :
• Pain so severe that you can't sit still or find a comfortable position
• Pain accompanied by nausea and vomiting
• Blood in your urine
• Difficulty passing urine

• Red flag features warranting investigations:
• First stone episode under the age of 25
• Recurrent stones
• Bialateral or multiple stones, nephrocalcinosis
• Strong family history of stones
• PImpaired renal function (eGFR- < 60 ml/min/1.73m2) associated with stones
• Non calcium oxilate stones
• Radioluscent stones (may be urate or cystine)
• stone episode associated with underlying condition (eg: inflammatory bowel disease , gastric byepass suregery or metabolic syndrome)

Initial diagnosis in red flag features patients :

Sample	Test
Serum Sample	Urea, Creatinine, Pottasium, Bicarbonate, Chloride, calcium phosphate, magnesium,25-hydroxyvitamin D,urate
Whole blood(EDTA tube)	Parathyroid Hormone
Fresh spot urine sample	Urine pH (pH meter better than dipstick)
2 x 24hour urine collection (acidified sample)	Calcium, oxilate, citrate, sodium ( and ceratinine - to assess completeness when comparing repeated 24h collections from the same patient)

• Types of renal stones
• Calcium stones
• Struvite stones
• Uric acid stones
• Cystine stones

• Management :
• All patients in whom further management is appropriate should receive dietary and lifestyle advice.
• In temperate climates, a fluid intake of at least two litres a day halves recurrence rates.
• A diet high in fruit and vegetables is recommended because the high potassium content promotes urinary citrate excretion
• These foods are also a source of phytates which, like citrate, increase calcium salt solubility.
• An adequate calcium intake, with restricted animal protein, reduces urine oxalate.
• A limited salt and sugar intake is also advised.
• Where possible, an underlying disorder predisposing to stone formation should be identified and treated.

Urine chemistry risk factor	Possible effect on stone formation	Treatment
Hypercalcuria	Most stones contain calcium	Dietary salt and sugar restriction(Thiazide +/- amiloride)
Hyperoxeluria NB: urine oxelate often within the 'reference range' in calcium oxelate stone formers	Common component of stones	Dietery restriction of Animal protein and high oxelate foods Adequete diary calcium intake
Hyprocitraturia	Reduced solubility of calcium salts	High fruit vegetable intake citrate supplementation
Low urine pH	Reduced solubility of calcium oxalate, uric acid and cystine	Urine alkalinization with citrate or bicarbonate ( avoid in calcium phosphate nephrolithiasis)