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Chemical Pathology > Renal Calculi > Flashcards

Renal Calculi Flashcards

1
Q

What are renal calculi?

A
  • Renal calculi (Kidney stones or nephrolithiasis or urolithiasis)
  • Are hard deposits made of minerals and salts that form inside the kidneys as a result of precipitation of urinary constituents
  • May develop in one or both of the kidneys.
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2
Q

When calcifications occur scattered throughout the parenchyma, it is called?

A

Nephrocalcinosis

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3
Q

Kidney stone formation is considered to be an environmental or nutritional disease, linked to affluence (T/F)?

A

True

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4
Q

Kidney stones affects what percentage of the world population?

A
  • 12% of the world’s population
  • 5-10% of people in western world are thought to have formed at least one kidney stone by the age of 70years
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5
Q

Kidney stones are associated with what risk?

A

An increased risk of end-stage renal failure

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6
Q

Sex predominance in Formation of Kidney stones ?

A
  • Male predominance of about 12%
  • Females - 6% (prevalence is increasing)
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7
Q

Renal colic is defined as??

A

The passage of a stone, associated with severe pain called renal colic, which may last 15mins to several hours and is commonly associated with nausea and vomiting

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8
Q

Underlying pathogenesis of renal stones ?

A
  • Occurs when solutes crystallize out of urine to form stones.
  • Commonly caused by inadequate hydration and subsequent low urine volume
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9
Q

The 4 most common factors contributing to urinary stone formation?

A
  • Hypercalciuria - excess calcium in the urine
  • Hyperoxaluria - increased urinary excretion of oxalate
  • Hyperuricosuria - urinary excretion of uric acid greater than 800 mg/day in men and greater than 750 mg/day in women.
  • Hypocitrauria - Citrate in the urine is an inhibitor of calcium salt crystallization.
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10
Q

Other factors contributing to the formation of kidney stones include?

A
  • anatomical features leading to urinary stasis
  • low urine volume
  • High oxalate or high sodium diet
  • UTI
  • Systemic acidosis
  • medications (indinavir, Atazanavir, triamterene, Guaifenesin, over use of silicate and sulfonamide)
  • Cystinuria
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11
Q

Drugs that can predispose to Kidney stone formation?

A

indinavir, Atazanavir
triamterene
Guaifenesin
over use of silicate and sulfonamide

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12
Q

The 4 main types of renal calculi includes ?

A
  • Calcium stones
  • Uric acid stones
  • Struvite or Magnesium Ammonium phosphate stones
  • Cystine stones
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13
Q

Features of calcium oxalate stones ?

A

Calcium Oxalate
- Most common (80%), caused by supersaturation of urine with calcium and oxalate
- Tend to form in alkaline medium

Causes ;
- Hyperparathyroidism
- sarcoidosis
- osteoporosis,
- vitamin intoxication
- renal calcium leak
- Hpomagnesemia
- hypocitrauria
- hyperoxaluria

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14
Q

Features of calcium phosphate stones?

A
  • (5-10%)
  • caused by super-saturation of urine with calcium phosphate salt
  • also occurs in alkaline medium.
  • Causes are excessive intake of milk and diary products
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15
Q

Features of uric acid stones

A
  • Uric acid stones are associated with a pH of less than 5
  • a high intake of purine foods (fish, legumes, meat),
  • cancer
  • These stones may also be associated with gout.
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16
Q

Cystine stones features ;

A
  • Due to an intrinsic metabolic defect causing the failure of the renal tubules to reabsorb cystine, lysine, Ornithine and arginine
  • Seen in inherited cystinuria
17
Q

Struvite or Magnesium Ammonium Phosphate Stones features;

A
  • Struvite stones occur to the extent of 10–15% and have also been referred to as infection stones and triple phosphate stones.
  • It is caused by gram-negative, urease positive organisms that breakdown urea into ammonia and are formed in alkaline medium.
  • This is common in woman because of UTI

Common organisms include;
- pseudomonas,
-proteus
- klebsiella.

18
Q

Pathophysiology of renal stone formation

A
  • The pathophysiology is in two phases:

first is super-saturation of the urine by stone-forming constituents, including calcium, oxalate, and uric acid.
- Crystals or foreign bodies can act as nidi, upon which ions from the supersaturated urine form microscopic crystalline structures.

•The resulting calculi give rise to symptoms when they become impacted within the ureter as they pass toward the urinary bladder

• The second phenomenon, which is most likely responsible for calcium oxalate stones, is deposition of stone material on a renal papillary calcium phosphate nidus, typically a Randall plaque

19
Q

Pathophysiology of calcium oxalate stone formation?

A
  • Deposition of stone material on a renal papillary calcium phosphate nidus, typically a Randall plaque (always consist of calcium phosphate)
  • These plaques start suburothelial and then gradually grow until they break through the urothelium into the renal pelvis
  • They form an anchored lithogenic nidus for stone formation.
  • Once in continuous contact with urine, layers of calcium oxalate typically start to form on the calcium phosphate nidus.
  • Calcium oxalate stones tend to form when the urinary pH is under 7.2, while calcium phosphate will form in more alkaline urine.
  • Calcium phosphate stones usually precipitate in the basement membrane of the thin loop of Henle and may erode into the interstitium.
20
Q

Colicky pain is due to?

A

Dilation and spasm of the ureter

21
Q

Natural urinary stone inhibitors includes?

A
  • Water (urinary volume)
  • Citrate
  • Tamm-Horsfall protein
  • Nephrocalcin
  • Uropontin
  • Glycosaminoglycans
22
Q

clinical manifestation Of Renal calculi ?

A
  • Severe pains on the side and back just below the ribs.
  • Pain spread to the lower abdomen and groin
  • Pain comes in waves and fluctuates in intensity
  • Pain on urination
  • Cloudy or foul smelling urine
  • Nausea and vomiting
  • Fever and chills if infection is present
  • Urinating small amount of urine
  • Hematuria- as 85% of patients demonstrate at least microscopic hematuria on urinalysis.
23
Q

Radiation of renal colic

A
  • Renal colic usually peaks within 90 to 120 minutes
  • pain radiation follows dermatomes T10 to S4
24
Q

Phases of renal colic pain?

A

1) The first phase may wake the patient up from sleep, and the pain is steady, followed by waves of excruciating pain.

2) The second phase is characterized by constant pain and may last 3 to 4 hours.

3) The third phase is associated with mild pain relief, but waves of pain may persist. This phase may last 4 to 16 hours.

25
Q

Physical examination findings in renal stones

A
  • may reveal costovertebral tenderness and hypoactive bowel sounds.
  • The testis and pubic area may be tender to touch.
  • Fever is rarely seen in renal colic, but the presence of fever, pyuria, and leucocytosis may be indicative of pyelonephritis.
26
Q

Urinanalysis in Investigation of renal calculi

A
  • Hematuria is usually present, but up to 15% of kidney stone patients will not demonstrate even microscopic hematuria.
  • The presence of urinary crystals may suggest urolithiasis.
  • *^Positive nitrites, leukocytes, and bacteria** suggest infection, which should be cultured and treated aggressively.
27
Q

Ultrasound scan findings;

A
  • Obtained to screen for the presence of significant nephrolithiasis but may often miss small stones, calculi hidden by overlying bowel, or uncalcified
  • For assessing obstruction and resultant hydronephrosis,
  • It can also be used to measure the resistive index, which can suggest ureteral obstruction.
  • Ultrasound can also identify uric acid and other non-calcific stones if they are large enough (usually greater than 4 mm)
  • but it can also miss the presence of stones less than 5 mm.
28
Q

Risk factors for renal calculi;

A
  • Bone disorders
  • Chronic diarrhea, malabsorption
  • Diabetes, obesity (especially in women)
  • Family history of kidney stones
  • Gastrointestinal disease
  • GI bypass surgery (especially Rous-en-Y)
  • Gout
  • Hyperparathyroidism
  • Prior stones
  • Renal tubular acidosis
  • Sarcoidosis
29
Q

Medical treatment of renal stones ?

A
  • Smaller stones (less than 5 mm) have a greater chance (90%) of being excreted in the urine with use of medications like
  • tamsulosin
  • nifedipine
  • alfuzosin
  • Any hint of a urinary tract infection should be treated aggressively with antibiotics.
  • Acute management requires IV hydration, analgesia, and antiemetic medications
30
Q

Conditions requiring urgent intervention ?

A
  • An obstructing stone in a patient with a urinary tract infection, fever, or sepsis. (This is called pyonephrosis or obstructive pyelonephritis and requires urgent surgical decompression by urology or interventional radiology)
  • Nausea or pain uncontrolled with outpatient management
  • An obstructing stone in a solitary kidney
  • Any degree of simultaneous bilateral obstruction can easily lead to renal failure.
  • Any degree of obstruction with a rising creatinine
31
Q

In the case of urinary tract infection or urosepsis with an obstructing stone, how do you manage?

A

The obstruction should first be relieved with either a ureteral double J stent or nephrostomy tube placement.

The more severely ill the patient, the greater the benefit from a nephrostomy tube

•Definitive stone management can then occur once the infection is no longer active.

Morbidly obese patients and those who cannot be safely taken off of their blood thinners may require a double J stent, regardless.

32
Q

Surgical management of renal stones

A
  • Lithotripsy ( extracorporeal shockwave lithotripsy)
  • Ureterolithotomy,
  • pyelolithotomy,
  • nephrolithotomy,
  • partial or total nephrectomy.
33
Q

Prevention of renal stones

A
  • Avoid too high protein diet: usually protein intake is limited to 60g/day to reduce urinary excretion of calcium and uric acid
  • Salt and high sodium food should be reduced - sodium competes with calcium for reabsorption in the kidney.
  • Take plenty fluids during the day.
  • Avoid/reduce intake of oxalate containing foods.
  • Avoid activities that would cause excessive sweating and dehydration.
34
Q

Prognosis of Renal Calculi?

A
  • Close to 80% to 90% of renal calculi pass spontaneously.
  • About 3% of patients need admission because of pain, inability to pass the stone, or dehydration.
  • A few patients may develop urinary tract obstruction and an upper urinary tract infection. This can result in urosepsis or pyelonephritis.
  • Most of these patients require an urgent procedure to bypass the stone until the infection is resolved.
  • The recurrence rate of renal calculi has been reported to be about 50% within 5 years.
  • Individuals with ongoing malignancy or metabolic disorders are at a higher risk for recurrence.
35
Q

The key for all patients with renal calculi is to?

A

Stay hydrated; not medical therapy is success without adequate hydration and sufficient urinary fluid output

Chemical Pathology (8 decks)

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