Nephrolithiasis Flashcards
what is the definition of nephrolithiasis?
Nephrolithiasis refers to the presence of crystalline stones (calculi) within the urinary system (kidneys and ureter). Such renal stones are composed of varying amounts of crystalloid and organic matrix. Ureteric stones almost always originate in the kidney but then pass down into the ureter.
what is the epidemiology of nephrolithiasis?
Lifetime prevalence 10%
Adult men more likely
what is the aetiology of nephrolithiasis?
Renal stones are crystalline mineral depositions that form from microscopic crystals in the loop of Henle, distal tubules, or the collecting duct.
This is usually in response to elevated levels of urinary solutes such as calcium, uric acid, oxalate, and sodium, as well as decreased levels of stone inhibitors such as citrate and magnesium.Low urinary volume and abnormally low or high urinary pH also contribute to this process. All of these can lead to urine supersaturation with stone-forming salts and subsequent stone formation.
Supersaturation depends on urine pH, ionic strength, solute concentration, and solute chemical interaction. The higher the concentration of two ions, the more likely they are to precipitate out of solution and form crystals. As ion concentrations increase, their activity product reaches the solubility product (Ksp). Concentrations above this point can initiate crystal growth.
Once crystals are formed, they either pass out with the urine or become retained in the kidney, where they can grow and stones can form. In urine, even when the concentration of calcium oxalate exceeds the solubility product, crystallisation may not occur because of prevention from urinary inhibitors. Both urinary calcium and oxalate are important and equal contributors to calcium oxalate stone formation.
Several factors increase calcium oxalate supersaturation in urine. These include low urine volume and low citrate, and increased calcium, oxalate, and uric acid.
what are the risk factors for nephrolithiasis?
Dehydration High salt intake White Male Obesity Crystalluria
what is the pathophysiology of nephrolithiasis?
Stone formation pathology unknown
Renal colic from nephrolithiasis is secondary to obstruction of the collecting system by the stone. The stretching of the collecting system or ureter is due to an increase in intraluminal pressure. This causes nerve endings to stretch and therefore the sensation of renal colic. Pain from urinary calculi can also be due to local inflammatory mediators, oedema, hyperperistalsis, and mucosal irritation.
what are the key presentations of nephrolithiasis?
renal colic
what is renal colic?
Presentation of nephrolithiasis. Classical renal colic is described as severe, acute flank pain that radiates to the ipsilateral groin. However, some patients may have no radiation and some stones are asymptomatic.
what are the signs of nephrolithiasis?
Risk factors
Previous history
Obesity
what are the symptoms of nephrolithiasis?
Renal colic
Nausea
Haematuria
Testicular pain
what are the first line and gold standard investigations for nephrolithiasis?
Non-contact helical CT scan (non pregnant adult) - urgent (within 24 hours), calcification seen in renal collecting system or ureter; hydronephrosis; perinephric stranding (indicative of inflammation or infection)
Renal ultrasound (pregnant or child) - calcification seen within urinary tract, along with dilation
Urinalysis - may be normal; dipstick positive for leukocytes, nitrates, blood; microscopic analysis positive for WBCs, RBCs, or bacteria
FBC and differential - variable, raised WBC may show infection
Serum electrolytes, urea and creatinine - hypercalcaemia may suggest hyperparathyroidism, hyperuricemia may suggest gout
Urine pregnancy test (women of childbearing age)- exclude ectopic pregnancy
what are the differential diagnoses for nephrolithiasis?
Acute appendicitis, ectopic pregnancy, ovarian cyst
how is nephrolithiasis managed?
Renal colic:
Hydration and analgesics (NSAIDs consider opioids)
Confirmed stone:
With infection - urgent decompression and urgent antibiotic therapy
Without infection - urgent decompression
Confirmed renal stone, no evidence of obstruction:
Hydration, analgesics, antibiotics, watchful waiting, surgical intervention
Condriemed ureteric stones, no evidence of obstruction:
As above + Medical expulsive therapy (MET) using an alpha-blocker is an option for distal ureteric stones <10 mm in adults and children.(tamsulosin or alfuzosin)
Pregnant:
Refer to obstetrician or urologist - If the patient has no evidence of infection, the specialist will arrange ureteroscopy. Ureteroscopy has been demonstrated to be safe in pregnancy.
how is nephrolithiasis monitored?
Once the patient’s stone episode is complete, patients with risk of recurrence should have a full metabolic workup, including serum studies and 24-hour urine, to determine whether any metabolic abnormalities exist that predispose to recurrent stone formation.
what are the complications of nephrolithiasis?
Post-percutaneous nephrolithotomy bleeding, post shock wave lithotripsy haematoma, post treatment sepsis
what is the prognosis of nephrolithiasis?
Nephrolithiasis is a lifelong disease process. The rate of recurrence of nephrolithiasis is 50% at 5 years
