Medical topic

1. RENAL CALCULI.
DR AL-AMMARY.

2. ETIOLOGY.
 Many theories have been proposed to explain the cause
of renal stone formation. Unfortunately, no one
mechanism can fully explain the cause of all stone
formers.
 In one commonly accepted model of stone formation, a
period of abnormal crystalluria is required. For crystals to
form and grow, the urine must be supersaturated with
the salt of the stone forming crystal.
 Urinary substances that act as inhibitors to crystal
formation must be reduced or absent in urine, and
certain proteins that act as the framework for the crystal
depositions must be present in the urine.

3. RISK FACTORS.
Risk factors that enhance stone formation
include;
1. metabolic state (influenced by the patients
genetic background),
2. hormonal imbalance,
3. environmental factors,
4. dietary excesses,
5. anatomic abnormalities leading to chronic
infection or stasis.

4. TYPES OF STONES.
 Stones form in the collecting tubules and pass into the
calyces, renal pelvis, and ureter.
 The most common stones are as follows;
1. Calcium-containing stones 70%.
(calcium oxalate, calcium phosphate, mixed)
2. Infection stones 15-20%.
(struvite, magnesium ammonium phosphate)
3. Uric acid stones, 5-10%.
4. Cystine stones, 1-5%.
 Men commonly form calcium stones with either oxalate or
phosphate while women are more prone to infection
stones due to higher incidence of UTI than men. Cystine
stones are inherited as an autosomal-recessive trait.

5. CLINICAL PRESENTATION.
 Nonobstructing caliceal stones are usually
discovered as incidental findings on
radiographs obtained for evaluation of other
organ systems or during evaluation of
hematuria.
 Obstruction at the level of the ureteropelvic
junction causes sharp, intermittent colicky pain
localized to the flank or costovertebral angle.
The pain is not related to activity and may be
accompanied by nausea and vomiting.

6. INVESTIGATIONS.
 Microscopic or gross hematuria is common. The
absence of hematuria does not exclude renal stone
disease.
 Pyuria may be present without infection and crystals may
be seen.
 An acid urine (pH<5.5) is suggestive of uric acid stone,
whereas a pH of 8 suggests an infections stone.
 Only 90% of stones are radiopaque at KUB. Pure uric
acid stones are usually radiolucent and do not appear on
a plain film of the abdomen.
 An excretory urogram (IVP) is obtained in all patients
suspected of having a renal stone, unless they are
allergic to contrast.

7. TREATMENT.
 Indications of surgical stone removal include;
1. persistent pain,
2. recurrent gross hematuria,
3. obstruction with progressive renal damage
4. recurrent UTI.
 Pure uric acid stones can almost always be
dissolved by oral alkalinization therapy.
Potassium citrate or sodium bicarbonate are two
oral agents that can be used to alkanize the
urine to a pH range of 6.5-7.

8. TREATMENT. cont…
 ESWL(electrohydraulic shock wave lythotomy) is
the treatment of choice in managing a 1-cm
obstructing calcium pelvic stone and it is
successful in >90% of cases. Cystine stones are
usually refractory to ESWL treatment.
 In addition, stones of other composition >2.5 cm
in diameter are frequently associated with
obstruction following ESWL treatment and such
patients are best managed by either
percutaneous or open surgical stone removal.

9. STAGHORN CALCULI:
ETIOLOGY.
 Most stones of staghorn size are infection-related and
composed of magnesium-ammonium phosphate
(struvite) along with calcium phosphate.
 These mineral precipitate on a matrix cast of the
pyelocalyceal system in a staghorn configuration.
 The basic abnormality in these patients is chronically
alkaline urine that results from infection with urease-
producing urinary pathogens.
 Some uric acid stones and cystine stones may also
develop in staghorn configuration.
 Calcium oxalate and calcium phosphate stones, the
most common of stones, rarely grow in staghorn shape
or to such a large size.

10. STAGHORN CALCULI:
TREATMENT.
 Many studies have shown that the natural
history of these stones is progressive
obstruction, infection, and loss of kidney
function. Therefore, the presence of this type of
stone is in itself an indication for intervention,
even in the absence of symptoms.
 In the past, a kidney splitting operation called
anatrophic nephrolithotomy was often
performed.
 Currently, various combinations of percutaneous
stone removal and ESWL may be used as an
alternative to such surgery.

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