Macroscopic Urine Examination

Question 1

Urochrome

Answer 1

Pigment responsible for yellow color of urine, formed from endogenous metabolism

Question 2

Red Pigment

Answer 2

Hematuria produces a cloudy red urine, and hemoglobinuria appears as a clear red specimen

Question 3

Foam

Answer 3

Bilirubin: Yellow foam in a sample if it is shaken, normal urine will only form a small amount that rapidly disappears

Protein: indicated by a large amount of white foam

Question 4

Orange Pigment

Answer 4

Medications given to people with UTIs can cause a thick orange pigment in urine that obscures the natural color and interferes with chemical tests that are based on color reactions

Question 5

Brown Pigment

Answer 5

If a fresh urine sample is brown and contains blood it may be due to glomerular bleeding resulting from the conversion of hemoglobin to methemoglobin

Question 6

Port Wine Pigment

Answer 6

Oxidation of porphobilinogen to porphyrin causes a port wine color

Question 7

Black/Brown Pigment Upon Standing

Answer 7

Urines that turn black or brown upon standing and have negative blood results, may contain melanin or homogentisic acid

• Melanin comes from melanogen which is produced in excess when malignant melanoma is present
• Homogentisic acid is a metabolite of phenylalanine and imparts of black color to alkaline urine from people who have have inborn errors of metabolism - alkaptonuria

Question 8

Blue or Green Urine Pigment

Answer 8

Urine may be caused by a urinary tract infection by Pseudomonas

Question 9

Purple Urine Pigment

Answer 9

Staining may occur in catheter bags and is caused by Klebsiella or Providencia