RENAL STONES UROLITHIASIS

1. RENAL STONES

2.  Renal stones are formed within the kidneys, and this
is called nephrolithiasis.
 Urolithiasis is a condition that occurs when these
stones exit the renal pelvis and move into the
remainder of the urinary collecting system, which
includes the ureters, bladder, and urethra.

3.  Many patients with urolithiasis can be managed with
expectant management, analgesic, and anti-emetic
medications; however, stones that are associated
with obstruction, renal failure, and infection require
further increasingly critical interventions.

4.  80% of stones are composed of calcium oxalate or
phosphate.
 Other stone types include uric acid (9%), struvite
(10%), and cystine (1%) stones and are significantly less
common than stones composed of calcium oxalate or
phosphate (80%).
Etiology

5.  The different types of stones occur due to varying
risk factors such as diet, prior personal and family
history of stones, environmental factors,
medications, and the patient’s medical history.

6.  poor oral fluid intake,
 high animal-derived protein intake,
 high oxalate intake (found in foods such as beans,
beer, berries, coffee, chocolate, some nuts, some
teas, soda, spinach, potatoes), and
 high salt intake.
RISK FACTORS

7.  Low calcium intake has been shown to increase the
risk of kidney stone formation, contrary to common
belief.
 Decreased oral calcium intake will reduce calcium
levels within the GI tract, which would otherwise be
available to bind to oxalate. This, in turn, will increase
oxalate absorption and excretion, increasing the risk
of stone formation.

8.  Procedures such as Roux-en-Y gastric bypass and
sleeve gastrectomy have shown a three-fold increase
in calcium oxalate stone formation.
 The presence of medical conditions such as chronic
kidney disease, hypertension, gout, diabetes mellitus,
hyperlipidemia, obesity, endocrine, and malignancies
increase the risk of the development of kidney
stones.

9.  The presence of medical conditions such as chronic
kidney disease, hypertension, gout, diabetes mellitus,
hyperlipidemia, obesity, endocrine, and malignancies
increase the risk of the development of kidney
stones.

10.  Struvite stones, also known as infection stones, are
less common and can form slowly and before
becoming symptomatic. This type of stone can form
large calculus .
 They are composed of magnesium ammonium
phosphate and form secondary to elevated urine pH,
and this is largely caused by the presence
of Proteus or Klebsiella species, which are urease
formers.

11.  Uric acid stone formation is related to low urinary uric
acid levels, low urine pH, and low urinary volume.
 Cystine stones are rare and occur due to an inborn
congenital disorder causing mutations in 2 genes,
SLC3A1 and SLC7A9. These mutations cause defective
cystine metabolism and transport, resulting in
cystinuria and stones.

12.  Urolithiasis occurs when crystals that the stone is
composed of supersaturate the urine due to being
present in a high concentration and begin to collect
and crystallize within the parenchyma of the kidney,
forming the renal calculi.
 These crystals will aggregate together and continue
to enlarge with the potential to migrate into the
ureter and become symptomatic.
Pathophysiology

13.  If the stone causes an obstruction and does not allow
for the passage of urine through the ureter,
hydronephrosis can occur secondary to upstream
dilation of the ureter and renal pelvis.
 obstructruction is near the ureteropelvic junction
(UPJ) because in this region the diameter of the
ureter is very narrow.

15.  Stones are painful within the ureter because as they
pass through the ureter, increased luminal tension
and hydronephrosis will lead to prostaglandin release,
resulting in colicky pain associated with the condition.

16.  symptoms, ranging from asymptomatic to critically ill.
 sudden to gradual onset, unilateral colicky
abdominal/flank pain that often waxes/wanes,
hematuria (90% microscopic on UA), nausea,
vomiting, and fever.
 Depending on the location of the pain within the
urinary tract, pain can range from flank pain when
near the ureteropelvic junction to groin/scrotal/labial
pain if the stone is at the ureterovesical junction.
History and Physical

17.  Pediatric patients may present with irritability, crying,
fevers, and vomiting. Awake and alert patients are
often restless due to the pain and shift around
incessantly to find a position of comfort.
 In severe cases, stones can cause urinary obstruction
and/or can become a source of sepsis.

18.  Urine analysis (UA) with microscopy (can show gross
blood or + microscopic hematuria, +/-leukocyte
esterase, +/- nitrites +WBC), urine HCG (all women of
reproductive age), CBC, CMP, lactic acid, lipase,
amylase, blood cultures (if the patient has +SIRS
criteria).
Evaluation

19.  Renal ultrasound
 X-ray of kidney, ureter, and bladder (KUB) can be
used to assess for radiopaque stones (calcium
phosphate and oxalate), but not radiolucent stones
(uric acid and cystine),
 CT abdomen/pelvis without contrast has become the
ideal study of choice to assess for ureterolithiasis if
the patient can tolerate radiation, with sensitivity and
specificity of 95% and 98%.

20.  The benefit of MRI is that it provides 3D imaging
without radiation, and it is a good second-line
imaging option for pregnant and pediatric patients
to be used adjunctively to ultrasound.

21.  pain control is an important intervention. Oral and IV
anti-inflammatory medications (NSAIDs) are indicated
as first-line treatments for pain. Opioids can be used,
but are reserved for refractory pain.
 Nausea and vomiting should be treated with IV
antiemetic medications such as ondansetron,
metoclopramide, promethazine.
 Medical expulsive therapy, or MET, includes alpha-
blockers, such as doxazosin and tamsulosin, which is
a useful adjunct to facilitate passage of larger (5-10
mm) stones but has not shown to be beneficial in the
passage of smaller ones.
Treatment / Management

23.  IV crystalloid fluids can be given to patients who
appear dehydrated due to persistent vomiting, but
have not been shown to facilitate stone passage
 Approximately 86% of stones will pass
spontaneously within 30-40 days

24.  large stones, or if the presentation is acute renal
failure, oliguria/anuria, associated infection, or a
history of the solitary kidney is present, may require
urgent/emergent urologic intervention.
 Intractable pain or vomiting, inability to tolerate oral
intake, pregnancy, or pediatric patients may require
hospitalization for closer observation.

25.  There are various methods of acute urologic
interventions, including extracorporeal shockwave
lithotripsy (ESWL), flexible ureteroscopy (URS), and
percutaneous nephrolithotomy (PCNL).

29. percutaneous nephrolithotomy
(PCNL)

31.  Acute renal obstruction with signs of urinary tract
infection is a urologic emergency. This will require
emergent decompression to prevent permanent renal
damage and worsening of infection.
 The two options currently present for this are
indwelling ureteral catheter and placement of a
nephrostomy tube.

32.  calcium urolithiasis, medications such as thiazide diuretics, citrate salts
(potassium citrate), and lifestyle modifications are beneficial in long-term
management
 Struvite stones require surgical intervention and close follow-up with
urology.
 The cornerstone of cystine stone urolithiasis is lifestyle modification,
including increasing fluid intake to optimize urinary output to around 3
liters per day and minimizing animal protein and sodium intake. Potassium
citrate and thiol drugs have also been beneficial in patients with a history of
cystine stones.
 Uric acid stones can be managed with increased fruit, and vegetable intake
decreased animal protein intake, and initiation of potassium citrate and uric
acid lowering medications such as allopurinol to prevent recurrence of
stones.

33.  Asymptomatic/calyceal stones (non-struvite) typically do not
require acute intervention and can be monitored over time with
a routine evaluation with ultrasound or KUB.
 Stones that are less than 5-6 mm can usually pass spontaneously
and can be treated using medical management (anti-emetics,
analgesia, increased oral fluid intake, and alpha-receptor
antagonists [i.e., tamsulosin]).Patients with small stones should
be counseled on risk factor modification to prevent stone
recurrence.
 Larger stones may require more invasive techniques such as
shock wave lithotripsy, percutaneous nephrolithotomy, or a
combination of the two.
Prognosis

34.  Infected stones have a good prognosis with early
acute intervention, including antibiotics,
hemodynamic stabilization, and interventions to
remove the septic stone.

35.  Complications include acute renal failure secondary to
obstruction, anuria, urinary tract infection with renal
obstruction, and sepsis

36.  keep well hydrated (increase fluids to 2.5-3.5 liters/day and
 avoid food/drinks that are high in oxalates if they have a history of calcium stones.
 If expectant management is used, follow-up for repeat imaging/assessment is advised
after 14 days from diagnosis, along with oral NSAID use for analgesia and a urine
strainer to assess for passage of the stone.
 A healthy lifestyle, including weight loss if overweight/obese and a balanced diet low
in salt, is encouraged.
 Avoidance of fish oil and vitamin C has also been shown to reduce the risk of stone
formation.
 Intake of citric acid (lemon juice, orange juice, melon juice).
 Despite common belief, a diet with higher calcium intake (milk, tofu, orange juice,
almonds), has been shown to reduce the risk of stone formation because calcium will
bind with oxalate in the gut, reducing the amount of urinary oxalate available to
precipitate into a stone
Deterrence and Patient Education