Urinalysis and Body Fluids 6th Edition by Majorie DiLorenzo, Susan Strasinger

Exercise 12

Differentiate between cystinuria and cystinosis, including the differences found during analysis of the urine and the disease processes.

Step 1 of 2

Cystinuria:

Increased cystine (amino acids) in urine causes cystinuria.

• It is caused by inability of renal tubules to reabsorb cystine during glomerular filtration

• Arginine, lysine, and ornithine are present along with cystine

The cystinuria disorder has two modes of inheritance:

• In one mode, any one of the 4 amino acids arginine, cystine, lysine, and ornithine reabsorption is affected

• In another mode, only lysine, and cystine are not reabsorbed

• Nearly 65% of the people who are present with all four amino acids lysine, ornithine, cystine, and arginine in affected condition will have renal calculi formation in early life

• Lysine, ornithine, and arginine are not present in microscopic constituents because they are much soluble than cystine

• As cystine is not soluble much, the laboratory screening test involves observation of cystine in first morning or concentrated specimens

• Only cystine is found in the analysis of calculi

• Cyanide-nitroprusside is used in screening test for cystine

• 2mL of Sodium cyanide is added to 3mL of urine and after 10 minutes, addition of 5 drops of 5% sodium nitroprusside produces red-purple color, which indicates excess cystine in the specimen