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Common Urological Problems

Urinary Stone Disease Evaluation

  • - General Urology - Common Urological Problems - Urinary Stone Disease
  • Jul 25, 2010
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Tags: | abdominal pain | acute abdomen | biliary stone | bowel obstruction |

Urinary stones can mimic other retroperitoneal and peritoneal pathologic states.  A full differential diagnosis of the acute abdomen should be made, including acute appendicitis, ectopic and unrecognized pregnancies, ovarian pathologic conditions including twisted ovarian cysts, diverticular disease,  bowel obstruction,  biliary stones with and without obstruction, peptic ulcer disease, acute renal artery embolism, and abdominal aortic aneurysm, to mention a few.  Peritoneal signs should be sought during physical examination.

A proper evaluation requires a thorough medical history.
The nature of the pain should be evaluated, including its onset, character, potential radiation, activities that exacerbate or ease the pain,  associated nausea and vomiting or gross hematuria,  and a history of similar pain.  Patients with previous stones frequently have had similar types of pain in the past, but not always.

1. Crystalluria-
Crystalluria is a risk factor for stones.

Stone formers, especially those with calcium oxalate stones, frequently excrete more calcium oxalate crystals, and those crystals are larger than normal >12 mm). The rate of stone formation is proportional to the percentage of large crystals and crystal aggregates. Crystal production is determined by the saturation of each salt and the urinary concentration of inhibitors and promoters.

Urine samples should be fresh; they should be centrifuged and examined immediately for optimum results.  Cystine crystals are hexagonal;  struvite stones appear as coffin lids; brushite (CaHPO4) stones are splinter-like and may aggregate with a spoke-like center; calcium apatite-(Ca)5 (PO4)3 (OH)-and uric acid crystals appear as amorphous powder because the crystals are so small; calcium oxalate dihydrate stones are bipyramids; and calcium oxalate monohydrate stones are small biconcave ovals that may appear as a dumbbell.  Cystine and struvite crystals are always abnormal and require further investigations. Other crystals are frequently found in normal urinalyses.

Urinary Stone Disease

Urinary Stone Disease

2. Socioeconomic factors-
Renal stones are more common in affluent, industrialized countries. Immigrants from less industrialized nations gradually increase their stone incidence and eventually match that of the indigenous population. Use of soft water does not decrease the incidence of urinary stones.

3. Diet-
Diet may have a significant impact on the incidence of urinary stones. As per capita income increases the average diet changes,  with an increase in saturated and unsaturated fatty acids, an increase in animal protein and sugar,  and a decrease in dietary fiber,  vegetable protein, and unrefined carbohydrates. A less energy-dense diet may decrease the incidence of stones. This fact has been documented during war years when diets containing minimal fat and protein resulted in a decreased incidence of stones.

Vegetarians may have a decreased incidence of urinary stones.  High sodium intake is associated with increased urinary sodium, calcium, and pH, and a decreased excretion of citrate; this increases the likelihood of calcium salt crystallization because the urinary saturation of monosodium urate and calcium phosphate (brushite) is increased.

Fluid intake and urine output may have an effect on urinary stone disease.  The average daily urinary output in stone formers is 1.6 L/day.

4. Occupation-
Occupation can have an impact on the incidence of urinary stones.  Physicians and other white-collar workers have an increased incidence of stones compared with manual laborers. This finding may be related to differences in diet but also may be related to physical activity; physical activity may agitate urine and dislodge crystal aggregates. Individuals exposed to high temperatures may develop higher concentrations of solutes owing to dehydration,  which may have an impact on the incidence of stones.

5. Climate-
Individuals living in hot climates are prone to dehydration, which results in an increased incidence of urinary stones, especially uric acid calculi. Although heat may cause a higher fluid intake, sweat loss results in lowered voided volumes. Hot climates usually expose people to more ultraviolet light,  increasing vitamin D3 production. Increased calcium and oxalate excretion has been correlated with increased exposure time to sunlight. This factor has more impact on light-skinned people and may help explain why African Americans in the United States have a decreased stone incidence.

6. Family history-
A family history of urinary stones is associated with an increased incidence of renal calculi. A patient with stones is twice as likely as a stone-free cohort to have at least one first-degree relative with renal stones (30% versus 15%). Those with a family history of stones have an increased incidence of multiple and early recurrences.  Spouses of patients with calcium oxalate stones have an increased incidence of stones; this may be related to environmental or dietary factors.

7. Medications-
A thorough history of medications taken may provide valuable insight into the cause of urinary calculi. The antihypertensive medication triamterene is found as a component of several medications, including Dyazide, and has been associated with urinary calculi with increasing frequency. Long-term use of antacids containing silica has been associated with the development of silicate stones. Carbonic anhydrase inhibitors may be associated with urinary stone disease (10–20% incidence). The long-term effect of sodium- and calcium-containing medications on the development of renal calculi is not known.

Protease inhibitors in immunocompromised patients are associated with radiolucent calculi.

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