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Common Urological Problems

Urinary Stone Disease - Special Situations

  • - General Urology - Common Urological Problems - Urinary Stone Disease
  • Jul 25, 2010
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Tags: | abdominal pain | asymptomatic hematuria | calcium | calcium nephrolithiasis |

Medullary sponge kidney is a common condition characterized by tubular ectasia associated with parenchymal cysts and clefts that predispose to nephrolithiasis in 50% of affected patients. It is most often an asymptomatic condition; however it may present with renal colic, hematuria, or urinary tract infection.  It is a radiographic diagnosis.

The condition can involve select papillae or,  more frequently, can be global.  A full metabolic evaluation helps direct appropriate medical therapy.

There are 3 main types of renal tubular acidosis: types I, II, and IV. Type I is associated with renal calculi.

image Figure 16–11.  Scout abdominal radiograph demonstrating a right renal calculus (arrow) in a patient with severe kyphoscoliosis. Respiratory compromise limited patient positioning for surgery.

Patients with type I renal tubular acidosis present with persistent acidemia with a low serum bicarbonate value unexplained by hyperventilation or known renal failure. The diagnosis should be suspected in those with a known family history, severe hypocitraturia, nephrocalcinosis, medullary sponge kidney, or a fasting urine pH >6 in the absence of infection. Patients usually present with nephrolithiasis (calcium phosphate), nephrocalcinosis, or osteomalacia (or a combination).  This disease can be acquired as an adult or inherited with an autosomal dominant pattern.

The diagnosis is confirmed by assessing the patient’s response to an acid load.  This is frequently produced by a rapid oral ammonium chloride load (0.1 g/kg over 1 hour). The dose can be given before bedtime in the evening; the patient is instructed to fast until a second morning voided urine sample and a serum bicarbonate level are obtained.

A normal person responds by eliminating the acid load in the urine, resulting in a urinary pH <5.3. Those who do not respond in this fashion can be said to have type I renal tubular acidosis.

Urinary Stone Disease

Urinary Stone Disease

Additionally, the diagnosis should be challenged in those with normal citrate values. Treatment is centered on base replacement with potassium citrate or potassium bicarbonate solutions.  Urinary citrate levels can be used to monitor effective treatment.

Squamous cell carcinoma of the upper urinary tract is uncommon but has been associated with calculi in more than 50% of cases. Chronic irritation from calculi or infection may be contributory factors. Upper-tract calculi may predispose patients to transitional cell carcinoma.

Urinary calculi are unusual in children.  A full and thorough metabolic evaluation should be undertaken.  Stone analysis is particularly helpful in directing these investigations.  Children born prematurely and given furosemide while in the neonatal intensive care unit are at increased risk of developing urinary stone disease. Treatment may be limited by endoscope size.  Preliminary data show no change in renal growth after ESWL.

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