USMLE Forums banner

Hexagonal Crystals in Urine

11K views 7 replies 6 participants last post by  chienpolska 
#1 ·
A 17 year old man comes to the emergency department and complains of intensive left flank pain that radiate to the groin.He refer to his symptoms as 'stone passage',which he has experienced "for so many times since childhood". His uncle has the same problem. Urinary shows hexagonal crystals. The urinary cyanide nitroprusside test is positive. Which of the following is the most likely cause of this patient's condition?

A. Amino acid transport abnormality
B. Parathryoid adenoma
C. Abnormality of uric acid metabolism
D. Excessive intestinal reabsorption of oxalate
E. Infection

A Qbank Q
 
#5 ·
Answer A

The most likely diagnosis is cystinuria, characterized by impaired amino acid transport. The problem lies with the defective transport of dibasic amino acids (cystine,lysine,arginine and ornithine) by the brush borders of renal tubular and intestinal epithelial cells. Cystine is poorly soluble in water ; this leads to the formation of hard, radioopaque renal stones.

In this case,the clues to the correct diagnosis are the patient's personal history of recurrent stones since childhood, positive family history,typical hexagonal crystals on urinalysis ,and a positive urinary cyanide nitroprusside test. The urinary cyanide nitroprusside test can detect elevated cystine levels, which can help confirm the diagnosis; this test is widely used as a qualitative screening procedure and is particularly helpful in diagnosis in homozygotes.

Very high Yield !
 
#6 ·
Answer is A

Cystinuria is a condition passed down through families in which stones made from an amino acid called cystine form in the kidney, ureter, and bladder.
Symptoms

  • Blood in the urine
  • Flank pain or pain in the side or back
    • Pain is usually on one side; it is rarely felt on both sides
    • Pain is often severe:redcheeks;
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top