Hemoglobinuria or myoglobinuria

Hemoglobinuria and myoglobinuria

I always confused these two conditions when I was a medical student. Now let me make these conditions as simple as possible.

Hemoglobinuria just means presence of hem in the urine whereas myoglobinuria means presence of myoglobin in the urine. Both can cause acute kidney injury due to pigment nephropathy.

Remember that both can cause a false positive in urine dipstick for RBC. Patients with both these conditions produce tea coloured urine. However myoglobinuria may be differentiated from hemoglobinuria by performing a series of simple tests.

-Myoglobinuria is brown, and often only a few RBCs are present in the urine.
-Hematuria produces a reddish sediment in spun urine samples.
-Red or brown urine with a negative dipstick result for blood indicates a dye in the urine.
-Hemoglobin produces a reddish or brown coloration in the spun serum, whereas myoglobin does not discolor the serum.
-CK levels are markedly elevated in myoglobinuria.

Another common question in MRCP- if you notice red to brown urine with negative dipstick, there are only a few possibilities- bladder analgesic phenazopyridine or a variety of other medications, certain food dyes, the ingestion of beets in susceptible subjects, porphyria and hydroxocobalamin for the treatment of cyanide intoxication.

Question in MRCP

A 17 year old male with glucose-6-phosphate dehydrogenase deficiency presents with tiredness and is noticed to
be jaundiced. These features have developed since he developed a mild chest infection one week ago. Which one
of the following is the most likely haematological finding?

1 ) Haemoglobinuria
2 ) low mean cell volume
3 ) Positive direct antiglobulin test
4 ) Reduced reticulocyte count
5 ) Spherocytes present on blood film

Answer: 1