KIDNEY STONE DISEASE   52A

A 48-year-old man presents to the emergency department with severe, colicky right flank pain. He denies dysuria and fever. He does report significant nausea without vomiting. He has never experienced anything like this before. On examination, he is afebrile, his blood pressure is 160/80 mm Hg, and his pulse rate is 110 beats/min. He is writhing on the gurney, unable to find a comfortable position. His right flank is mildly tender to palpation, and abdominal examination is benign. Urinalysis is significant for 1+ blood, and microscopy reveals 10 to 20 red blood cells (RBCs) per high-power field. Nephrolithiasis is suspected, and the patient is intravenously hydrated and given pain medication with temporary relief.

What are the salient features of this patient’s problems? How do you think through his problems?

Salient features: Flank pain; first episode in the fourth decade of life; nausea and vomiting; writhing in discomfort; afebrile; flank tender to palpation; benign abdominal examination; hematuria

How to think through: The colicky pain with the hematuria suggests nephrolithiasis. The patient also has demographic risk factors. (Stones occur in men > women; ages 30–50 years.) What feature in this case makes nephrolithiasis more likely than an acute abdomen? (The patient is moving continually.) Why is he hypertensive and tachycardic? (Most likely because of pain.) What is the most common type of renal calculi? (Calcium oxalate.) Treatment and dietary interventions vary based on the type of stone. Although serum and urine studies can help ascertain the type of stone, as can radiographic lucency and appearance, analysis of a recovered stone is best. Which stones are radiolucent on plain abdominal radiography? (Uric acid stones.) What radiographic study is preferred? (Noncontrast helical computed tomography [CT].) The largest stone that can pass spontaneously is 6 mm. Can any medications facilitate the passage of a stone? (α-Blockers and calcium channel blockers.) Pain control with nonsteroidal antiinflammatory drugs and opioids is the other key component of treatment. What developments in this case would serve as indications for further intervention? (Failure to pass the stone; intractable pain and nausea; fever.) What are some of the interventions available? (Extracorporeal shock wave or percutaneous lithotripsy.) What dietary modification should be recommended to prevent recurrence? (Low-salt diet; decreased animal protein intake; increased fluid intake.)

KIDNEY STONE DISEASE   52B

What are the essentials of diagnosis and general considerations regarding kidney stone disease?

Essentials of Diagnosis

Flank pain, hematuria, nausea and vomiting

Identification of stone on noncontrast spiral CT scan

General Considerations

Kidney stones affect men more often than women; high-protein and high-salt diets and genetic factors such as cystinuria and distal renal tubular acidosis contribute to stone formation

Five types of kidney stones: calcium oxalate, calcium phosphate, struvite, uric acid, cystine

Most urinary stones contain calcium (85%) and are radiopaque; uric acid stones are radiolucent

Uric acid calculi: from malignancy, uricosuric medications, abrupt weight loss, low urine pH

Struvite calculi (“staghorn” calculi) occur with recurrent urinary tract infections with urease-producing organisms, including Proteus, Pseudomonas, and Providencia spp.

Cystine calculi: an inherited disorder with recurrent stone disease

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