Kidney stones Flashcards
What are kidney stones?
Nephrolithiasis refers to the presence of crystalline stone (calculi) within the urinary system.
Such renal stones are composed of varying amounts of the crystalloid and organic matrix.
Ureteric stones almost always originate in the kidney and then pass down into the ureter.
How are kidney stones formed?
Renal stones are usually in response to elevated levels of urinary solutes such as calcium, uric acid, oxalate.
There’s also decreased levels of stone inhibitors such as citrate and Mg2+.
How common are kidney stones?
There’s a 7-10% lifetime risk for women and men respectively.
How do symptomatic patients present?
Patients typically present with acute renal colic, although some patients are asymptomatic.
Classification of kidney stones
Calcium stones- 80% of renal calculi.
Calcium oxalate- 80% of all calcium stones.
Calcium phosphate- 20% of all calcium stones.
Uric acid stones- 10-20% of renal calculi, most commonly due to urinary pH <5.5
Cystine stones- 1% of renal calculi (caused by an inborn error of metabolism, cystinuria an autosomal-recessive disorder that results in abnormal renal tubular re-absorption of the amino acids cysteine, lysine and arginine
Struvite stones: 1-5% of renal calculi also known as infection stones, composed of magnesium, ammonium and phosphate.
Signs & symptoms
Acute, severe flank pain. Previous episodes. Nausea and vomiting Urinary frequency/urgency. Haematuria Testicular pain Groin pain Fever Tachycardia Hypotension
Risk factors of kidney stones
High protein & salt intake White ancestry Male sex Dehydration Obesity Crystalluria Occupational exposure to dehydration Warm climate FHx Precipitant medications: calcium-containing antacids. carbonic anhydrase inhibitors. sodium and calcium-containing medications.
Investigations for kidney stones
Urinalysis- positive for leukocytes, nitrites and blood (may be normal) FBC Serum electrolytes Urea and creatinine Urine pregnancy test Non-contrast helical CT scan Stone analysis Consider: Plain abdominal radiography (KUB)- calcification Renal ultrasound- calcification Intravenous pyelogram- calcification 24-hour urine monitoring- increased or decreased values for urinary electrolytes. Spot urine for cystine.
Differentials of kidney stones
Acute appendicitis Ectopic pregnancy Ovarian cyst Diverticular disease Bowel obstruction Acute pancreatitis Ovarian torsion Peptic ulcer disease Gastroenteritis Abdominal aortic aneurysm Pyelonephritis Tubo-ovarian abscess Testicular torsion Musculoskeletal back pain Mesenteric ischaemia Constipation Cholecystitis & biliary colic
Management of kidney stones
The main goal of initial treatment for an acute stone event is symptomatic relief.
Symptomatic relief is with hydration and analgesia/anti-emetics as needed.
If there is no infection, the stone may be managed conservatively with opioids and NSAIDs
Many ureteric stones <10mm pass spontaneously, using an alpha-blocker such as tamsulosin may be of benefit.
The use of alpha-blocker for this is an off label use of these drugs.
How should kidney stones be managed if there are signs of infection?
Immediate urological consultation should be initiated.
This is an emergency that requires antibiotics and renal decompression to decrease the chance of sepsis.
How should >10mm kidney stones be managed?
Stones > 10mm indicates additional surgical treatment:
Extracorporeal shock wave lithotripsy (ESWL) for 10-20mm or ureteroscopy can be considered as first-line therapy.
>20mm should be treated with percutaneous nephrolithotomy (PCNL)
How should pregnant women with stones and renal colic should be managed?
If the renal colic is not controlled with oral analgesia or there are an obstructing stone and signs of infection, the pregnant woman should receive a ureteric stent or percutaneous nephrostomy tube.
