NEPHROLITHIASIS

BY

DR I O MBAH. (MB;BS, FWACP) CHIEF CONSULTANT PHYSICIAN /

NEPHROLOGIST, Snr Lecturer, CM & HS, BHUTH, JOS

M1 POSTING, MAY 2021

KIDNEY STONES: SIMPLE STONE FACTS

• 1% OF all stones in adults are Cystine stones
• 2L of urine production / day is recommended for stone prevention
• This takes us to FLUID THERAPY (Expatiate)
• 3^rd most common disorder of UT is stones
• 4 most common stones of UT are Ca2++, (75%); Uric acid (10%) , Struvite (5%) and Cystine (1%)

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• 5% of stones are STRUVITE stones
• 6 weeks is adequate for any stone that will pass to do so
• 7% OF WOMEN will have a stone more of STRUVITE
• Apples don’t fall far from it’s tree (Family members live in same environ)

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When it comes to kidney stones, numbers play an important role

• We are often faced with difficult questions like
• Will my stone pass?
• When will my stone pass?
• What happens if I do nothing?
• Am I a time bomb waiting for my stone to pass?

• Why am I making stone?
• Will I have surgery?
• What type of surgery is good for me?
• Won’t you guys crush the stones?
• So those are the concerns to consider when you tell a patient they have kidney stones.

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The truth is that we don’t have all the answers to these Qs.

• Like snowflakes, no two kidney stones are alike and therefore may behave differently.
• 1 stone passage is all you need to have to know you don’t want another
• Stones account for 1% of all hospital admissions
• Stones are the 3^rd commonest cause of UT disorder behind UTI and prostate conditions

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SOME IMPORTANT NUMBERS AGAIN!

• 25% of patients with Kidney stones need surgery
• 25% of “ “ “ have gout
• 25% of patients “ “ “ have family history
• 35-45 years of age is peak incidence of stones formation

KIDNEY ANATOMY

FILTRATION OF FLUIDS

INTRODUCTION

• As kidneys filter waste from the blood, they create urine.
• Sometimes salts & other minerals in urine stick together to form small kidney stones
• These range from the size of sugar crystal to a ping pong ball

• They are largely unnoticed until they move about & cause blockage
• They can affect any part of the UT from kidneys to bladder

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THE ACTUAL MECHANISM

• SUPERSATURATION & CRYSTALLIZATION > stone formation
• Types of stones are : CALCIUM, URATE, STRUVITE & CYSTINE
• All commoner in men
• Except Struvite FEMALE TO MALE RATIO 2:1. Why?
• Industrialized countries have 10-12% risk of stone formation life-time risk

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TYPES OF STONES : CALCIUM STONES

• Commonest type of all UT stones
• Ca Oxalate the most common type which could be
• A) Ca Oxalate monohydrate
• B) Ca Oxalate dihydrate
• Then Ca PO4

WHAT CAUSES CALCIUM STONES?

• AETIOLOGY: Hypercalciuria (40-75%), which could be
• Absorptive “”, Renal, Resorptive hypercalciuria
• Hypocitraturia (Citrate normally binds to Ca to form a soluble substance thereby discouraging crystallization of Ca stones, but lack of citrate…

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INTRO 2: 15% of Ca stones are 2ndry to an underlying disorder

• Distal Renal Tubular acidosis (Rare)
• Hereditary / Acquired (Hyperchloremic acidosis)
• Pry Hyperoxaluria (Hereditary)

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OTHERS

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• CaPO4 in stones are usually hydroxyapatite or brushite
• Idiopathic Hypercalciuria is ? Hereditary (Normocalcemia with unexplained calciuria).
• Hyperuricosuria (DIET)

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WHAT OF CYSTINE & STRUVITE?

• Cystine stones (Hereditary)
• In Idiopathic hypercalciuria R/O Paget’s disease
• 50% of men form a single Ca stone, others may form multiple stones (Recurrent stones may occur once in 3yrs
• Struvite (Infection) : commoner in females (1:3)

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Types of stone

Uric acid

Calcium oxalate

Types of stones

Cystine

Struvite

AETIOLOGY / RISK FACTORS FOR KINDS OF STONES

• No single cause
• Family Hx; “Apples do no fall far from their trees”
• Personal Hx (Has to do with lifestyle, little H2O intake, dairy foods, sweats)
• BMI
• Dehydration (Low intake / Xs loss of fluids)

• Hyperparathyroidism
• Renal tubular acidosis
• Lack of subs that prevent crystallization (Pyrophosphate, Citrate, Glycoprotein)
• Supersaturated urine with these materials (Uric acid, Ca, oxalate etc)
• pH just has to be alkaline (for Ca stones to form Or acidic for uric acid stones to form)

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DETAILS OF URINARY STONES FORMATION

• Break down of delicate balance bw solubility & pptn of salts
• The kds must conserve water but they must excrete materials that have low solubility
• These two opposing requirements must be balanced during adaptation to diet, climate & activity
• The problem is mitigated to some extent bcos the urine contains subs such as pyrophosphate, citrate, & glycoproteins that inhibit crystallization

• These protective mechanisms are less than perfect
• When urine becomes supersaturated with insoluble materials (CaPO4, Oxalate, urate,) crystals form & grow
• Urine supersaturating can be increased by : DEHYDRATION, or by OVERSECRETION of Ca, PO4, Cystine, Uric acid
• Urine pH is also impt; <5.5 leads to uric acid stones, while CaPO4 (alkaline)

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Causes of Different types of stones (Those produced by inf, non-inf, gene)

• Ca oxalate; Oxalate naturally occur in food eg milk, cheese, yogurt, fruits, vegies, nuts, chocolate, high level of vit D, Liver, & Intestinal bye pass.
• Struvite : Usually in response to infections, UTI. Urea splitting orgs (MagnesiumNH4PO4). The stones can grow quickly to staghorn causing few symptoms. Historically 56% of staghorns are metabolic while 44% infective

• Uric Acid : People who don’t drink enough or who lose too much fluid & eat high prot diet, Could be genetic
• Cystine : Hereditary disorder, Autosomal recessive. Impaired Kd & Int tubular transport of cystine that cause the kidneys to excrete too much of certain dibasic a.a (Cystine, Ornithine, Lysine, Arginine [COLA] > cystinuria (Only Cystine is asso with stone formation due to its poor solubility.

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SYMPTOMATOLOGY

• Asymptomatic (8mm stones have 20% chance of spontaneous passage)
• When symptomatic (usually stones >10mm. Largest kd stone ever 13cm)
• Flank pain which increases in intensity (4-6hrs), colicky, sharp, stabbing, throbbing discomfort, radiating to the groin (An experience you don’t want a repeat) One stone passage is enough

OTHERS

• Dysuria
• Haematuria (strangury)
• Urgency
• Frequency
• Cloudy foul smelling urine
• Fever, chills, Nausea, Vomiting if infection is present

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BLOODY / CLOUDY URINE SAMPLES

INVESTIGATION

• Most patients with nephrolithiasis have remediable metabolic disorders that cause stones to form
• These can be detected by chemical analyses of serum & urine
• 24 hr urine collection / corresponding blood samples
• Since stone risks vary with diet, activity, & environment at least one urine collection should be made on a weekend & another on a work day

• In hyperuricosuria (10-50%), Hyperoxaluria (8%), Hypocitraturia (favours). At the uric acid level of 750mg/day (female) ; 800mg/d (male) > hyperurico..
• Urine pH (<5.5 favours urate stones, while alkaline, Ca stones)
• Urine vol (>2.5l/day ) reduces stone formation by 50%

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DIAGNOSIS

• Plain abd xray for radiopaque stones (except uric acid stone)
• Nephrocalcinosis (Ca stones grow in the papillae, break but stay there so that multiple papillary calcification are seen on abd x-ray (nephrocalcinosis). This is common in Hereditary Renal Tubular Acidosis (RTA) or severe hypercalciuria
• 24 hr urine collection with corresponding blood sample to assay the levels of Ca, Uric acid, electrolytes, Cr, vol, oxalate, citrate, pH
• USS
• Helical CT scanning without radio contrast enhancement

TREATMENT ; DEPENDS ON THE FOLLOWING

• Location of stone
• The extent of obstruction
• The nature of the stone
• The fxn of the affected & un affected kidneys

• Presence or absence of UTI
• The progress of stone passage
• Risk of operation / anaesthesia in light of clinical state of patient
• Treatment could be medical or surgical

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TREATMENT

• MEDICAL ; No matter the type of stone
• Drugs like alpha1 blockers to dilate ureters causing stones to pass (<.5cm can pass naturally) & Also Captopril & D-penicillamine (for Cystine)
• Liberal fluid intake to dilute urine to dissolve stones is advised for all patients.
• BUT Irrigation chemolytic therapy (added for Cystine stones)

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• Alkalinize (pot cit) or acidify (Vit C) urine depending on stone type (Alkali supplements for Uric acid stones, Cystine stones, Distal renal tubular acidosis, Hypocitraturia). Acidify for CaPO4 & Brushite stones
• Thiazides also lower urine calcium
• Dietary advice (Low purine diet ; no red meat ? Fish)

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SURGICAL

• SURGICAL : Percutaneous Nephrolithotomy using nephroscope
• Ureteroscopy (ureteral & stones in renal pelvis)
• Extracorporeal Lithotripsy (crush stones & it passes out in urine)

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INDICATIONS FOR STONE REMOVAL

• Severe obstruction
• Infection
• Intractable pain
• Serious bleeding